AAPM Newsletter September/October 2000 Vol. 25 No. 5

Newsletter AMERICAN ASSOCIATION

OF

PHYSICISTS

IN

VOLUME 25 NO.5

MEDICINE SEPTEMBER/OCTOBER 2000

AAPM President’s Column Creatures of Habit

By Kenneth Hogstrom Houston, TX By the time this column reaches you, another AAPM Annual Meeting will have passed (the 42nd), you will hopefully have taken a relaxing summer vacation, your kids will be back in school, you will be almost caught up at work, and many will be beginning to prepare for the annual ASTRO, RSNA, or other meeting.

In many ways we are creatures of habit! One of our best habits is our striving to work together and individually for medical physics to best serve humankind. When we look at the world from this viewpoint, our differences are small and our challenges are great. In recent months, I have been particularly pleased to see the significant amount of work done together and individually by those serving and practicing medical physics. I am proud to be associated with medical physics, and I am fortunate to be able to work with so many fine people in our association.

I believe this theme is evident as you read through my column and others in the Newsletter.

Chicago 2000 World Congress The World Congress on Medical Physics and Bioengineering was quite a success. The weather in Chicago was extremely pleasant, and the meeting was well organized.

Data from the Annual Meeting Coordination Committee showed there were 5,488 attendees (3,582 medical physics and 1,906 bioengineering registrants) of which 3,534 were scientists (1,871 medical physicists and 1,663 bioengineers). It is not possible to recognize everyone who contributed to the organization of the meeting, so let me share with you some that I mentioned in my welcoming statement on behalf of the AAPM at the opening ceremonies. I recognized those AAPM members

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on the Organizing Committee, co-president Bill Hendee and members Gary Fullerton, Renate Muller-Runkel, Azam Niroomand-Rad, Russell Ritenour, Bruce Thomadsen, and Kenneth Vanek. Next, I especially recognized the AAPM headquarters office staff, who handled the meeting preparations, financial records, and information systems for the World Congress. The latter allowed efficient registration, abstract submission and acceptance, and program development. We had an outstanding display of technical exhibits,

INSIDE TABLE OF CONTENTS President’s Column...........p.1 Chairman of the Board.....p.4 Salary Survey......................p.6 Executive Director’s Col....p.7 New Officers and Board.....p.8 Nomination of Officers....p.8 Coolidge Award Winner.....p.9 Achievement Awardees....p.11 New AAPM Fellows..........p.12 Year 2000 Awards.............p.12 Varian Resident Award.....p.13 Education Council Report...p.13 Letters to Editor.............p.15 New Members................p.21 Summer School.................p.23

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and we thank our technical exhibitors for their support.

The scientific programs provided an outstanding venue for us to interact professionally. And I recognized Bob Gould, Richard Leahy, Eric Klein, Mary Martel, Ben Archer, and Caridad Borras for organizing the tracks in diagnostic, radiation therapy, and radiation safety medical physics, as well as the many abstract reviewers.

2000 AAPM Summer School The 2000 AAPM Summer School, “General Practice of Radiation Oncology Physics in the 21st Century,� was held July 29 - August 1 on the Northern Illinois University Campus in Dekalb, IL. Preliminary data show that the summer school was a huge success with approximately 325 registrants and faculty. Special thanks to the program directors, Almon Shiu and David Mellenberg, and to Kevin Corrigan, local arrangements coordinator. The format of morning lectures, afternoon workshops, and evening demonstrations was well received. Proceedings of the summer school are available from Medical Physics Publishing.

The Medical Physicist Brochure The Public Education Committee (PubCom) has undertaken a very important task for Medical Physicists. It is preparing a set of brochures on the Medical Physicist that is targeted to the patient for the purpose of helping educate them on the role of the Med-

ical Physicist in their diagnosis and treatment. The Committee recently completed the first brochure describing the role of the Medical Physicist in radiation oncology, and that brochure was distributed to AAPM members in the spring of this year. Shortly after its release, several concerns were raised about certain aspects of the brochure, which resulted in the AAPM Executive Committee (EXCOM) freezing the brochure from further distribution until these issues could be addressed. Following its April 28-29 meeting, EXCOM appointed Jerry White, Secretary, to head a review committee consisting of N i c k Detorie, chair of Public Education Committee, Jatinder Palta, chair of Science Council, and Don Frey, chair of Education Council. It is hoped that modifications to the brochure will be completed and approved by PubCom before the end of the year. It is important that the brochure appropriately reflect to the patient the role of the Medical Physicist in radiation oncology, as the brochure will be used for many years to come.

Also, it sets the standard for development of similar brochures for the role of the Medical Physicist in diagnostic imaging and nuclear medicine.

National Institutes for Health (NIH) The AAPM continues to be a strong supporter of the NIH developing a National Institute of Biomedical Imaging and Engineering. Our support is through membership in the Academy for Radiological Research (ARR), and our rep-

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resentative is Phil Judy. The ARR, whose President is Douglas Maynard, had a booth at the 2000 World Congress, where it gathered 600 additional letters and emails to US Congressional representatives, bringing the total to over 13,000. As the issue is currently at a critical time in Congress, I sent an email to all AAPM members in August urging them to communicate support to their Congressional representatives. Recall the AAPM Board of Directors supports this action because imaging and bioengineering are not specific to particular disease sites or organ systems, and consequently do not fit well into the structure of the NIH. It is believed that a new Institute would increase opportunity and efficiency. We will keep the membership informed of future developments.

On August 8, 2000, I sent a letter on behalf of the AAPM Research Committee and Science Council to Ellie Ehrenfeld, Director, Center for Scientific Review. The letter, which is posted on our web site, responded to the NIH April 2000 Phase II Implementation Plan developed by the Panel on Scientific Boundaries for Review. The AAPM supports the NIH mission to fund technology-driven research as well as hypothesis-driven research and development.

However, there is concern that the fragmenting of the Radiation Study Section would have a negative effect on radiotherapy physics by diffusing qualified reviewers over too many study sections. Also, the AAPM recommends that Med-

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ical Physicists be appointed to Study Section boundary teams involved in the design of Study Sections likely to evaluate medical physics grant applications.

National Council for Radiation Protection Ken Kase reported to the AAPM Board of Directors the appreciation of the National Council for Radiation Protection (NCRP) for the support of the AAPM. The NCRP operates under congressional charter as a voluntary organization supported by contracts and grants for specific projects, and several staff have been discharged recently due to lack of funding. As one of the radiological societies that support the NCRP, the AAPM Board approved increasing its general contribution to the NCRP from $3,500 to $7,000 annually. The AAPM also supports the NCRP for operation of Scientific Committee 9, which is drafting a report on Structural Shielding and Design Evaluation for Medical Use of X-Rays in Diagnostic Radiology, and Scientific Committee 46-13, which is drafting a similar report for Therapeutic Radiology.

Journal of Applied Clinical Medical Physics The AAPM Board of Directors has approved a request that will purchase from the American College of Medical Physics (ACMP) a CD for each AAPM member, which will contain a cumulative copy of all issues through 2001 of the ACMP Journal of Applied Clinical Medical Physics (JACMP).

Also, the ACMP has offered the

AAPM a link to the JACMP web site. The JACMP is the new on-line journal of the ACMP, which complements our Medical Physics Journal by offering a venue for publication of non-scientific medical physics papers, i.e. clinical, professional, and educational articles. The journal’s editor is Peter Almond. The Board’s passage of this request acknowledges the value of the JACMP to the Medical Physicist and the AAPM’s support for the success of this new journal. To learn more of JACMP, please access its web site http://ojps.aip.org/acm/ and read the editorial by Medical Physics editor, Colin Orton.

American Board of Radiology In response to a request from the American Board of Radiology (ABR), the AAPM Board of Directors approved that the AAPM re-nominate Bill Hendee for a second 4year term as Trustee in Radiologic Physics (Diagnostic Imaging) to the ABR. Bill Hendee presently serves as Vice President of the ABR. The AAPM Board of Directors, under the supervision of President-elect Charles Coffey, is in the process of selecting nominees for the replacement of Guy Simmons, who is completing his second term as a Trustee in Radiologic Physics (Nuclear Medicine). Our Board of Directors amended the selection process to allow one of its three nominees to be selected by the American College of Medical Physics using the same criteria as the AAPM.

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Accelerator Engineers I am pleased to report that the ad-hoc committee entitled “Formation of Professional Society for Radiotherapy Accelerator Maintenance Personnel” hosted the first organizing meeting of interested accelerator engineers and technicians. The meeting was held July 22-23 in Chicago, just prior to the 2000 World Congress on Medical Physics and Biomedical Engineering. This meeting was a complete success with there being 50 accelerator maintenance personnel in attendance. There were presentations by Jim Galvin, Sal Trofi, Don Frey, Bob Rice, Ned Ster nick, and myself. There was considerable time for group discussion that resulted in the formation of a number of committees to begin addressing issues necessary for formation of the professional society.

Nomination of Elected Officers One item discussed in the Long Range Planning meeting earlier this year was the method for nominating officers to be elected by the AAPM membership. There is a desire to have broader representation than the present Nominating Committee. Jean St. Germain, chair of the Rules Committee, explains the present process and is soliciting member opinion in her article later in the Newsletter. I feel there is a need for change to have a more democratic nominating process, and I encourage input from the membership to Jean.

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Report of the Chairman of the Board of Directors

by Geoffrey Ibbott Lexington, KY Annual Meeting Events The 2000 Annual Meeting was a full and interesting one.

I hope that all who attended learned as much and enjoyed themselves as much as I did.

Congratulations to the organizers for a very successful event!

In this column, I will describe several actions taken by the Board of Directors during the Annual Meeting.

These are followed by a report from the Intersociety Summer Conference.

Salary Survey to be Available to Institutions The Professional Council submitted an action item to make the AAPM Salary Survey to institutions that hire medical physicists.

This action stemmed from discussions at this year’s Long-Range Planning meeting. The new policy adopted by the Board reads as follows: “If an institution sends a written request to AAPM Headquarters on the institution’s letterhead which indicates that they hire medical physicists and need access to the salary survey, then Headquarters will forward a copy of the most recent survey.”

Discount for Subscribers to Electronic Journal Increased The Journal Business Management Committee (JBMC) submitted an action item to continue the discount offered to members who subscribe to

Medical Physics Online and elect not to receive the paper version for the full year. The action item also recommended increasing the discount from $10 to $20 for the year. This action was approved.

Additional Headquarters Staff The Board recently approved several action items that will add to our Headquarters Staff.

First is a position proposed by the Professional Council, and approved last year, to recruit a Government Relations Specialist. Recruiting for this position has begun. The position was discussed in previous Newsletters.

The Board approved a request from the Electronic Media Coordinating Committee to create a new position at Headquarters called Web Designer. This position will assist Micheal Woodward and the IS group at HQ to undertake revisions to our web site, and further develop it.

The Compensation Committee recommended that the temporary position created at HQ to assist with planning for the WC 2000 be made permanent.

Sal Trofi pointed out that as the Association grows and provides more services to its members, the additional staff person is needed. The Board agreed with the recommendation.

Intersociety Summer Conference July 28-30, 2000 Each year, the American College of Radiology organizes a

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gathering of leaders from a number of radiological societies and organizations. This conference is organized by the Intersociety Commission, an operational commission of the ACR which has approximately 45 member organizations. The Intersociety Commission was established to promote collegiality within the field of radiology; to foster and encourage communication among the national radiological societies; provide direct representation to the Board of Chancellors; and make recommendations on problems and areas of concern in radiology.

Kay Vydareny, MD, of Emory University chairs the Commission.

Each organization is invited to send two officers and the executive director. In the past, the AAPM has sent the President and Chairman of the Board, although other senior medical physicists have been asked to represent the AAPM when, as is sometimes the case, the Conference coincides with our Annual Meeting.

This year, President Ken Hogstrom and I attended on

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behalf of the AAPM. Medical Physics was also represented

by Bhudatt Paliwal and Ken Vanek on behalf of the ACMP. The meeting was held at the Del Coronado Hotel in San Diego, California, from July 28-30, immediately following the World Congress 2000.

The topic for this year’s conference was “Radiology 2000: Reinventing Radiology. Strategies and Solutions - Past, Present and Future.” This topic was chosen by the Executive Committee of the Intersociety Commission because of recent concerns over how radiologists are trained, marketed and viewed by other physicians.

President Hogstrom and I arrived on Friday afternoon, missing the morning session, due to our attendance at the AAPM Board meeting on Thursday evening. The talks were on a variety of topics, but a key talk addressed one of the major topics of the conference: “What other clinicians think”, by David Guss, MD, chair of Emergency Medicine at UCSD. We also missed the Friday luncheon talk given by William Hendee, Ph.D., who spoke on the Institute of Medicine Report “To Err is Human: Building a Safer Health System.”

The remaining sessions on Friday addressed accreditation and credentialing issues. The speakers explained the ACR practice accreditation programs in Cardiovascular Imaging, MRI, and Ultrasound.

Several key themes emerged from this session: Radiologists must improve their relationships with patients, and improve their image with other doctors. There are needs to

improve the quality of radiological services, as well as to enhance training of residents and medical students. Finally, research efforts need to be increased.

On Saturday morning, the talks continued to address these themes. Three speakers discussed the Residency Review Committee, the ABR, and supply and demand issues. The focus was on improving the training of residents, but there was also much discussion about the current shortage of properly trained radiologists. It was noted that new training programs have been developed to address the shortage in specific subfields such as vascular and interventional radiology, but that few trainees are actually enrolled in these programs. It was also observed that while groups such as the Intersociety Commission often meet to develop strategies, these strategies are very difficult to execute successfully. The quote of the weekend was attributed to Robert Bree, MD, who said “Culture eats strategy for lunch.”

Dr. Douglas Maynard spoke on the formation of a National Institute of Biomedical Imaging and Engineering. He described the progress made recently by the Academy of Radiology Research to add sponsors to the bills presently before Congress. The AAPM has contributed to this effort.

Following the speakers on Saturday, the attendees again broke up into small work groups. The objective was to develop several action items on the topics of supply vs. demand, the image of radiolo-

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gists, research, and training.

During these sessions, the participants made suggestions for specific actions that should be taken by the ACR or other societies to address the issues.

On Sunday morning, these action items were reviewed and refined, and will form the basis of a “white paper” report that will be published later this year. While a number of specific actions were suggested in the report, several were prepared in the form of resolutions to be considered by the ACR at the Council meeting to be held in September.

The first of these resolutions addressed supply and demand of radiologists, technologists and physicists. The resolution calls for the formation of a task force made up of representatives of several societies including the AAPM, to explore ways to increase the workforce in radiology. The methods to be considered are to include support of training programs, and the increased use of technology.

Two additional resolutions were written to address the image of radiology and of radiologists, and will encourage radiologists to interact more directly with their patients.

With regard to promoting research activities among radiologists, the Conference drafted resolutions encouraging the ACR to stimulate a letter-writing campaign by radiologists to support passage of the bill to form a National Institute of Biomedical Imaging and Engineering. The Conference also will encourage the ACR Imaging Network to enable private practice groups to participate.

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Finally, the Conference set several initiatives to improve training of residents, and to ensure that certain important skills are tested by the written and oral board examinations.

As was the case last year, time was found after the Con-

ference adjourned for us to meet with the ASTRO leadership to discuss issues of mutual interest. This informal meeting has proven to be a valuable opportunity for communication and coordination of our societies’ activities.

President Hogstrom and I both felt our participation in this Conference was worthwhile and contributory, and encourage that the AAPM’s presence be continued in the future.

Validation of Salary Survey

by Arnold Cohen, Chair Snohomish, WA The topic of validity of the AAPM Professional Information Survey Report (Salary Survey) has been under consideration for years among the members of the Professional Survey Subcommittee.

However, in the last year or so, an increasing number of AAPM members have expressed their concern over this issue. In addition, during the Fal1 of 1999 there was considerable discussion on the Med Phys Listserver concerning the validity of the survey.

In response to these concerns, we are currently in the process of hiring an outside firm to perform a validity study of the 1999 survey. We will keep the membership informed as to the progress of this inquiry.

While the issue of external validity is unanswered, we do have some control over the internal validity of the process.

The entire survey process, including writing the questionnaire, tracking first-wave nonrespondents, reviewing completed responses for internal validity, data entry into the database, and producing and proofreading the completed report is done with great care and attention to detail. The

Salary Survey Report cover letter describes some of this process in the section on “Data Verification Procedures.” This section is reproduced below: “Since respondents are assured anonymity, it is not possible to verify their reported salaries with external sources. However, a number of different procedures are used to examine internal validity,consistency and reliability.

First, each returned questionnaire is read to ensure that all relevant items are answered.

Two people enter the data from each questionnaire independently.

Those files are then compared and, whenever the typists’ entries differ, the forms are checked as one method of identifying typographical errors. Prior to the analysis of salary information, the data from each questionnaire are examined for unlikely combinations of employment characteristics. Each questionnaire is checked if it fails any of the following comparisons: * Zero years of experience but highest degree was earned more than one year ago * Years of experience too high compared to year and level of highest degree

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* Total time spent working across all disciplines does not equal 100% * Total salary does not equal principal salary plus consulting salary, and * Forms that indicate no employer change but report salary changes between ‘98 and ‘99 that are over 10% or below 0%.

Questionnaires are also examined if the reported salaries were outside of the typical range for that employment category, or the salary was below $30,000 or above $200,000. The distribution of salaries within each employment category was closely scrutinized for unusual fluctuations, and the high and low salaries in each category are verified. Often these checks identified typographical errors resulting from poor penmanship, but occasionally problems can not be resolved and the response is excluded from the analysis. Finally, each line of data in this report is compared against the prior year’s data as a check for consistency over time. The questionnaires from groups whose salary data show large fluctuations over time are carefully examined for mistakes.”

Please direct any questions or suggestions regarding the survey process to: Arnold Cohen, Chairperson AAPM Professional Survey Subcommittee

arniez@compuserve.com

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Executive Director’s Column

By Sal Trofi College Park, MD World Congress Meeting The total attendance at the World Congress meeting held in Chicago in July was 5,488 or about 120 short of prediction.

This meeting was roughly twice the size and complexity of a regular AAPM annual meeting. Given that this is the first time my staff was involved in an undertaking of this magnitude, I want to congratulate them for a job well done.

Many attendees commented about their satisfaction of the high quality of the meeting.

We had anticipated about 2,000 abstract submissions, and we actually received 2,541. Power Point computer projection was allowed for presentations at the Chicago 2000 World Congress.

We had 153 exhibitors renting booths. Normally we have about 115. Many exhibitors rented more booths this year (498 booth equivalents this year vs. 388 total last year).

The extra revenue from exhibit rentals helped offset penalties paid to hotels for not meeting sleeping room guarantees. About 40% of World Congress registrants did not sleeping rooms in hotels with which we had contracts. This is an extraordinarily high percentage. Total revenues did exceed expenses, so the Congress, in the end, was a financial success.

AAPM Website

report is now available for free download to AAPM Members in PDF for mat, and new reports will be archived as they are published. Reports can be found under the publications section on the AAPM website.

The process for changing or obtaining a username and password is now fully automated. Forgot your password?

Enter your email address and it will be mailed to you. Never had a password or want to change yours? The system makes changes to your username and password in real time now with no human intervention. This greatly decreases the time a member must wait to download member resources from the website as it can be utilized at any hour of the day.

The History committee is beginning a project to put up every photograph in its archive online and available for viewing, along with a database of information about the photos that will be dynamically generated by the AAPM Membership. See a photo of an old friend and know something about the photo that isn’t in the description? Add a comment for others to read in the future.

A search engine has been restored to AAPM.ORG to make finding things a little easier. We had to temporarily discontinue this feature while we changed and reconfigured web servers.

Almost every task group

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Other News Dues renewal notices for the year 2001 will be mailed during the first week of October.

Dues amounts are the same as 2000 dues. You are encouraged to pay your dues via the AAPM website. This will help to reduce staff processing time.

We are in the search stage in the process of hiring a government affairs specialist. This new staff person will assist AAPM with their interaction with Congress, federal agencies and other policymaking groups. This person will also be expected to maintain a relationship with non-government agencies and other associations with which AAPM has an interest.

By the time this newsletter reaches you, construction of the new office space will be in progress. Staff phone numbers and email addresses will remain the same. All staff will be temporarily relocated to other officers in the building.

We intend to provide quality member services while construction is taking place.

Everything should be back to normal at the end of December.

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SEPTEMBER/OCTOBER 2000

AAPM New Officers and Board of Directors

Robert Gould

Gerald White, Jr.

Melissa Martin

President Elect

Secretary

Treasurer

Gary Ezzell

BOARD MEMBERS

AT

LARGE

John Hazle

Eric Klein

Robert Pizzutiello, Jr.

Mechanism for Nomination of AAPM Officers

by Jean St. Germain Rules Chair NewYork, NY In response to a request from the Board of Directors and the Executive Committee, the Rules Committee is consider-

ing whether the current mechanism provided for the nomination of officers should be changed. This current mechanism, found in Article III, Section 5 of the By-Laws, provides that the President appoint a Nominating Committee con-

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sisting of three persons with the President as Chair. The Committee nominates officers of the Association. These nominations do require concurrence of the Board. Typically, the President has chosen two Past Presidents of the

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Association to this Committee although he is free to appoint other persons to this task.

Some persons have expressed the opinion that this mechanism leads to the perception of an “old boys network”. Other persons feel that the mechanism has served us well.

A variety of changes to this mechanism have been proposed. The proposals include: adding the retiring Board

Members-at-Large to the Nominating Committee, having Committee members other than the President elected by the Board, developing a mechanism for members to nominate persons in a manner similar to the mechanism for Board Members-at-Large.

We are now soliciting opinions from the membership at large. Please feel free to email your suggestions or com-

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ments to me. We hope to bring a proposal to the Board for further discussion and possible action at the RSNA meeting.

2000 William D. Coolidge Award Winner Biography Lowell Anderson received his PhD degree in biophysics from the University of Rochester in 1958. After an eleven-year appointment as biophysicist at Argonne National Laboratory, where he worked mainly on developing instrumentation for neutron dosimetry, he joined the Department of Medical Physics at Memorial Sloan-Kettering Cancer Center in New York. At Memorial, because of his neutron dosimetry background he was selected to coordinate a contract with the Department of Energy to evaluate the use of 252Cf sources in interstitial brachytherapy. That project led to his long-time interest and specialization in brachytherapy physics. Lowell was head of Brachytherapy Physics until his retirement in 1998 and is currently Member, Emeritus at Memorial. He is certified in Radiological Physics by the American Board of Radiology and is a Fellow of the AAPM. He served on several Task Groups of the AAPM

Lowell Anderson Radiation Therapy Committee, most recently on TG-64 on Per manent Prostate Seed Implant Brachytherapy. He is President this year of the AAPM’s New York chapter, the Radiological and Medical Physics Society of New York.

He has served on the Board of the American Brachytherapy Society (ABS) and as Chairman of the ABS Physics Committee.

He is currently an editor of the Journal of Brachytherapy International. In 1982, he was

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honored by the ABS as the 3rd Henschke Memorial Lecturer. In 1990, he received the Kurt Sauerwein Award, for scientific contributions to high-dose-rate remote afterloading, from the German firm Isotopen Technik Dr. Sauerwein GMBH. At Memorial, Lowell was active in teaching and was, for many years, the coordinator of the Radiation Physics Lecture and Problem Course for residents and physics post-doctoral fellows. He served as advisor for many of these students in special projects that resulted in publications. He has presented numerous lect ure s on bra c hy th e r a p y physics for the AAPM’s Therapy Physics Review Course and as refresher courses at meetings of the American Society for Therapeutic Radiology and Oncology. Dr. Anderson has authored or co-authored 80 papers in peer-reviewed journals, as well as two books and 52 book chapters.

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Dr. Anderson’s Acceptance Speech Text of acceptance speech given at World Congress 2000 in Chicago Even those of you who know me may not realize that at one time I was a very religious person, and talked to God frequently. On one occasion during that phase of my life, I remember asking him about his concept of time. He said, "A million years on your time scale is just like one second to me." So then I asked, "How about a million dollars, what is that like to you." His response was, "A million dollars to me is just like a single penny is to you." Pressing my luck at that point, I said "God, do you suppose I could have a few of your pennies?" And God said, "Why certainly. Just a second!"

Well, I'm still waiting for that second to run its course. But I've come to realize that money isn't everything and that there are other kinds of income that are more rewarding, the honor I am receiving today for example. I must admit that, in view of the prestige-heavy list of former recipients, prior to my name being put forward, I had never considered myself Coolidge Award material. But I also must admit that, after reviewing all of the kind words used on my behalf, I'm gradually warming to the idea.

I think, perhaps, enough has been said about me and I would like to talk for a few minutes about the man for whom the award is named, Dr. William David Coolidge. It

struck me as a timely topic, not only because we haven't heard much about him in this forum for a while, but also because we are celebrating the end of a calendar century and Dr. Coolidge was someone whose own life spanned more than a century.

As you will recall from Dr. Laughlin and Dr. Goodwin's 40th Anniversary History of the AAPM, Dr. Coolidge was the first recipient of the Award in 1972 at the age of ninety-eight.

In view of his health, it was presented to him at the General Electric Research and Development Center in Schenectady, where he had spent nearly all of his professional career. It was the 18th and last of the various medals and awards he had received, beginning in 1914, for his contributions to metallurgy, to incandescent electric lighting and to radiology. He died on the 3rd of February, 1975, at the age of 101.

He shared ancestors with President Calvin Coolidge; John and Mary Coolidge came to Massachusetts in 1630. Born in 1873, William grew up on a small farm west of Boston. He did his undergraduate work at MIT in electrical engineering, where he was mentored by the chemist, W. R. Whitney, for whom he was later to work at GE. He switched to physics for his Ph D, which he obtained at Leipzig in 1898. He came back to MIT in 1899 to teach physics for a short time, but then broadened his scientific horizons again when he joined A. A. Noyes as a physical

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chemist. Whitney went on to found the GE Research Lab at Schenectady in 1900 and Coolidge joined him there in 1905. His first big project was to develop ductile tungsten.

Light bulbs, since Edison invented them in 1879, used carbon filaments until 1898, when osmium was the first metal filament to be tried. Serious efforts to develop tungsten filaments started in about 1904, but the filaments resulting from the many processes tried were all brittle and subject to "offsetting", lateral displacements at boundaries perpendicular to the filament.

Offsetting resulted from grain growth during a. c. operation and shortened bulb life significantly. After 1909, filaments made by the Coolidge process were free from this problem during comparable operation.

The Coolidge method started with baking purified tungstic oxide in a special crucible made in Battersea, a suburb of London, prior to reducing it to coarse tungsten powder. The crucible transferred something to the material that was important in avoiding grain growth; adding thoria was later found to accomplish the same result.

The metal powder was compacted into bars, which were pre-sintered at 1100 (C prior to actual sintering in hydrogen at temperatures a few hundred degrees below the melting point, the objective being to make particles combine and the density increase. The final act is high-temperature swaging, in this case drawing into wire.

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Coolidge early on had an interest in x-rays. Already in 1896, after graduating MIT, he built an x-ray producing machine and, not long after joining GE, his notes show that he recognized the potential value of tungsten for x-ray tubes. He got considerable support from Irving Langmuir, who joined the Lab in 1909 and confirmed that thermionic emission was enhanced by higher vacuum and by a thoriated filament. Coolidge published his successful hot-cathode x-ray tube in both Physical Review and the American Journal of Roentgenology.

The tube was produced in time to be useful in the First World War. The usual x-ray tube, prior to Coolidge, contained a gas at a pressure of a few microns.

Positive ions from the gas bombarded the cold cathode to produce electrons that then bombarded the anode to gen-

erate x-rays. In the Coolidge tube, on the other hand, the pressure was only a few hundredths of a micron and the cathode was hot. Among the important advantages cited by Coolidge for his design were that the tube current could be independently controlled by the filament temperature, that stable continuous operation was a reality, and that there were no unwanted x-rays from the glass envelope.

Coolidge's reputation was based mainly on what he accom p lis he d be fore he became Director. As summarized in an anonymous quotation, "He first made tungsten ductile and used it to generate x-rays in a tube that bears his name." With the problems of the 1929 depression taking their toll, Whitney resigned and Coolidge took over in 1932. He fulfilled these administrative duties admirably, fostering polymer development

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and nuclear research, and putting off retirement until near the end of the war, when he was succeeded by C. Guy Suits, whom he had made Asst Director in 1940.

Looking into Dr. Coolidge's background has certainly given me a fuller appreciation of the prestige represented by the Award. His accomplishments set a high standard for those who would follow in his path, and I am made to feel further honored to receive the award which bears his name. I am very thankful to those who have recommended me for this distinction, especially John Laughlin and Clif Ling, to each of whom I owe so much.

Thank you. „

2000 Achievement Award Winners

William Hanson

Mary Meurk

Houston, TX

Orinda, CA

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AAPM NEWSLETTER

SEPTEMBER/OCTOBER 2000

New AAPM Fellows Komanduri Ayyangar

Michael Goitein

David Neblett

Daniel Bassano

Lincoln Hubbard

William Potvin, Jr.

Jerry Battista

Saiful Huq

Anthony Benedetto

Shirish Jani

Raymond Rossi (Deceased)

James Carey

Franca Kuchnir

George Chen

Louis Levy

Chen-Shou Chui

David Lightfoot

Bert Coursey

Ali Meigooni

Kunio Doi

Radhe Mohan

Subhash Sharma Rene Smith Kenneth Vanek Theodore Villafana Martin Weinhous

Development Committee Announces Year 2000 Awards

by Steve Goetsch, Chair La Jolla, CA The Awards SubCommittee of the AAPM Development Committee has announced the winners of Residencies and Fellowships for the year 2000.

The Awards Subcommittee, chaired by Bhudatt Paliwal, reviewed applicants and made the final decisions on individual and program winners.

The AAPM Fellowship was awarded to Stephen Kry at University of Texas M.D. Anderson Cancer Center. The award will be supervised by Program Director Kenneth Hogstrom. The award, totaling $15,000 per year, began on July 1, 2000 and continues through June 30, 2002. The AAPM Fellowship is sponsored directly by the AAPM General Fund.

Two ASTRO Clinical Residencies were also awarded.

One award was given to Barnes-Jewish Hospital in St. Louis and will be administered

by Eric Klein. The second award is given to the University of Wisconsin and will be administered by Rupak Kumar Das. Each award is a two-year award, totaling $15,000 per year. Individual recipients of these awards have not been named yet. Both awards began July 1, 2000 and run until June 30, 2002. These awards are the 10th and 11th Residencies sponsored by the American Society for Therapeutic Radiology and Oncology, dating back to 1992.

The RSNA Research and Education Fund Residency was awarded to UT M.D. Anderson, and given to Kerry Krugh.

This residency, supervised by John Hazle, is a two-year award, totaling $15,000 per year, which began July 1, 2000 and runs until June 30, 2002.

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An additional Clinical Residency was awarded to the University of Minnesota. This award was originally to be sponsored by Elekta Oncology Systems, but due to budgetary problems Elekta will only be able to fund the second year of the award. The first year of the award will therefore be funded by proceeds from the AAPM Educational Endowment Fund, says to Development Committee Chair Steven Goetsch. The Residency will be under the supervision of Faiz Khan. No individual recipient has been named for the award, which began July 1, 2000.

One additional Residency, designated as the RSNA Research and Education Fund Residency, has yet to be awarded. Deadlines for this award were extended.

Ken Hogstrom noted at the July 23 meeting of the Devel-

AAPM NEWSLETTER

opment Committee, that EXCOM had voted unanimously at their meeting in April to ask the Awards SubCommittee of the Development Committee to give lowest priority in future Residency awards to those institutions

which have had a Residency award in the past but have not yet applied for CAMPEP accreditation. Present award rules also require an institution which receives a Residency award to apply for CAMPEP accreditation by the second

SEPTEMBER/OCTOBER 2000

year of the award. To date, Barnes-Jewish Hospital, University of Minnesota and McGill University have obtained CAMPEP accreditation for Residency programs.â–

Varian Oncology Resident Announced at University of Kentucky

by Steve Goetsch, Chair La Jolla, CA Stephen Klash is the the Varian Oncology Medical Physics Resident at the University of Kentucky Chandler Medical Center, and began his residency on November 3, 1999. Klash holds a B.S. degree in Biology from the State University of New York at Buffalo, and a M.S. degree in Biophysics from the same institution. He has worked as a health physicist and diagnostic physicist.

Geoffrey Ibbott, Associate Professor of Radiation Medicine, and current Chairman of the AAPM Board of Directors

made the announcement and will supervise Klash during his two-year residency.

The Varian Oncology residency has been granted to two residents each year, continuously since 1993. Past recipients have included the University of Minnesota (twice), Memorial Sloan-Kettering (twice), McGill University and Mallinckrodt Institute of Radiology (twice, one in 1999). Residency Awards are administered by the AAPM Development Committee and are currently sponsored by individual organizations or commercial firms. „

Stephen Klash

AAPM Education Council Report

by Donald Frey, Chair Charleston, SC The Education Council has had a very active spring and summer.

The Education and Training of Medical Physicists Committee, chaired by Bhudatt Paliwal, has established a new subcommittee. The Med-

ical Physicist Workforce Subcommittee, chaired by John Horton, held its first meeting at the World Congress, and is working to establish workforce requirements for the profession. Additional activities have centered on ways to collect data and plans to generate a first order model. The subcommittee will be working

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closely with committees from the Professional Council, and is also working on a revision of Report 44: Education and Training of Medical Physicists.

The revised version will include advances in the field of medical physics since the last report.

The Continuing Education Committee, chaired by

AAPM NEWSLETTER

SEPTEMBER/OCTOBER 2000

Tony Seibert, has established a new subcommittee. The ASTRO Education Coordination Subcommittee, chaired by Randall tenHaken, will be working with ASTRO to improve medical physics education at the ASTRO meeting.

This subcommittee has been aided by a meeting that President Hogstrom had with the ASTRO board of directors.

This year’s summer school, entitled “General Practice of Radiation Oncology in the Next Century,” was successfully held at Northern Illinois University in DeKalb, immediately following the World Congress. Topics covered included dose specifications, dosimetry analysis, 3D RTP, forward treatment planning (FRTP), IMRT, radiation therapy beam calibration, QA for R TP and IMR T, brachytherapy dose specification and calculations, ultrasound guided prostate implants and endovascular implants, HDR techniques, and detectors for 2D and 3D dosimetry. A published hardbound text of the program was distributed at the school.

Unlike previous schools, fully 50% of the formal program involved breakout sessions in small groups for hands-on workshops covering TG-51, TG-43, 3D RTP and implant techniques. Over thirty vendor-provided workstat i on s wer e used for workshops. The workshops were well received and popular, as were the informal evening sessions for workstation demonstrations and discussions. This school also incorporated format changes to help make it easier to attend

both the summer school and annual meeting: in addition to being re-linked to the annual meeting, the school was shortened to 3.5 days.

The school received mostly high praise from the nearly 450 total scientific attendees.

Extensive planning and work went into arranging and conducting this school with its numerous workshops. Program directors, Almon Shiu and David Mellenberg, and Local Arrangements chaired by Kevin Corrigan (Sherry Connors, Jackie Esthappan , Al and Lenore Hrejsa, Al Kepka, Nick Lembares, Ingrid Marshall, Chester Reft, Renate Muller-Runkel, Vythialingam Sathiaseelan and Jerry Soen) have done an extraordinary job in providing an outstanding education experience. Sincere thanks are due them as well as to our corporate colleagues for providing the workstations used for workshops and evening sessions..

If you were unable to attend, the book is available from Medical Physics Publishing.

Lee Goldman, the chair of the Summer School Subcommittee, reminds us that it is not too early to mark your calendars for the 2001 summer school. This school will be held at the University of Washington from June 2428, 2001 The topic will be “Accreditation Programs & the Medical Physicist.” The many areas where physicists are involved in these programs will be considered. Bob Dixon is the director.

The AAPM cooperates with many societies by endorsing and co-sponsoring their meetings. Endorsement means that

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the AAPM has reviewed the program and feels it could be of interest to medical physicists. Co-sponsorship means that the AAPM, through its members, is actively involved in planning the meeting. The AAPM co-sponsors the RSNA, SNM, SPIE, SCAR meetings.

The AAPM co-sponsorship allows the meetings to be accredited by CAMPEP. The Public Education Committee, chaired by Nick Detorie, has been working to set up liaisons with patient advocacy groups. The purpose of the liaisons is to inform the advocacy groups about the vital role that medical physics plays in the diagnosis and treatment of various diseases.

In addition the Medical Physics Education of Physicians Committee and the Training of Medical Physics Committee have been working to improve our relations with other societies and groups.

AAPM NEWSLETTER

SEPTEMBER/OCTOBER 2000

Letters to the Editor Medical Physics: A Question of Leadership

by Don Tolbert Honolulu, HI I will preface my remarks with a personal note. By the end of this calendar year, I will have retired from the medical physics profession. I have loved medical physics. It’s been good to me and I’ve tried to give back, but it’s time to move on to something else. It has been my privilege to have had leadership roles in all three of our organizations.

The highlights to me were chairing the AAPM’s Professional Council from ‘88 to ‘94 and following that, chair of the ACR’s Commission on Medical Physics (term ending on September 27 of this year). Leadership has been an important calling to me and while I’m still learning, I see things in our community that bother me a great deal.

A friend once offered that if you’re three steps ahead, you’re a leader. If you’re ten steps ahead you’re a target.

Effective leadership, in my opinion, protects everyone. It states objectives, explains rationale for attaining those objectives, and asks for discussion and perhaps a consensus before moving forward. I’ve personally benefited a great deal from the discussion phase. Leaders don’t necessarily know everything and all points of view need to be

sentation of the AAPM membership on professional issues.When I was Professional Council chair the question was whether or not the AAPM should continue to have a Professional Council. The answer was always yes. The presumption now appears to be that the ACMP will eventually be in charge so let’s begin the transition. Perhaps the ACMP can provide better coverage but how do we know? I’ve never understood why there has never been a proposal from the ACMP that would address issues that companion their desire to represent the medical physics community on professional issues. Practically how can a subset organization represent the entire membership of the AAPM on professional issues?

Should the AAPM enable the ACMP to direct its’ Professional Council? Should the AAPM eliminate its’ Professional Council and simply let the ACMP do it? How will the AAPM remain accountable for ACMP’s proposed representation? How will the AAPM membership not included in the ACMP membership be represented? Will referendums be used? If not, why?

I don’t know what the ACMP stands for. I let my member-

For years the ACMP has wanted to take over representation of the AAPM membership on professional issues. addressed.

An aspect of the relationship between the ACMP and AAPM has bothered me for some time. What was reported in the last AAPM Newsletter has prompted me to share my concerns with the AAPM members hip .

Pre s ide nt K e n Hogstrom reported in the most rece nt AAPM N e w s le t t e r (July/August) on the Long Range Planning meeting between EXCOM and the Council chairs. The purpose of the meeting was “to discuss initiatives and issues of importance to the AAPM and to reach consensus recommendations that could be incorporated into further development of the strategic plans of the appropriate committees.” As part of the report, the chair of the Professional Council and EXCOM agreed to “Continue to coordinate professional activities with the ACMP through having staff cooperation, having overlapping memberships at the committee level, and issuing technical standards in concert with ACMP and ACR standards.”

For years the ACMP has wanted to take over repre-

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AAPM NEWSLETTER

SEPTEMBER/OCTOBER 2000

ship lapse because there didn’t appear to be professional issue objectives from this organization led by people who are senior and supposedly experienced at leadership. I urge the

AAPM membership to become aware of professional issues, educate yourselves, and make your voice count. I fear that if you don’t, it won’t.

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AAPM NEWSLETTER

SEPTEMBER/OCTOBER 2000

Why Use TG-51 Instead of TG-21

by D.W.O. Rogers Ottawa, ON Canada Ionizing Radiation Standards, National Research Council of Canada Ottawa K1A 0R6 The TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams was published last year[1]. It is recommended for use by the AAPM and the RPC in Houston has started using it as the basis of its clinical dosimetry comparisons. In addition, a COMP committee recommended that TG-51 be adopted for use in Canada.

Despite all this approval and support, the protocol is very much a prescriptive document and the rationale for using it is not as clear as it could be. In this article I would like to present a brief rationale for why TG-51 should be used instead of TG-21.

The arguments for changing to TG-51 from TG-21 can be summarized as follows: *TG-51 is much simpler conceptually since it avoids the irrelevant quantity air-kerma. *TG-51 is much less work to use (once converted!) *TG-51 is easier to teach and has none of the many known errors in TG-21. *TG-51 has improved accuracy. *The formalism allows direct measurement of the major factors in the protocol (kQ, kecal, k’R50 ).

In the following I will concentrate on the issue of the

improved accuracy and indirectly address the other issues along the way. I will also discuss why TG-51 has adopted %dd(10)x as a beam quality specifier. For a more general introduction to the advantages of using absorbed-dose calibration factors, see ref [2].

Where does the improved accuracy come from for photon beams?

1) TG-51 gets the absorbed dose in a 60Co beam correct since it uses a calibration factor directly. When using airkerma and absorbed-dose calibration factors traceable to Canadian primary standards, the doses determined with TG51 are 0.1 to 0.8% higher than those determined using TG-21 (the exact value depends on the chamber used; data are from Shortt et al[3], and Seuntjens et al[4]). If one corrects all the known mistakes in TG-21 and uses the same data sets as in TG-51, these discrepancies range from -0.47% to +0.33%, so at least part of the problem is due to errors in TG-21, but the rest of the problem must be due to other, as yet not understood problems with TG21 or the data used (any errors in the standards would show up as a constant offset). If one is using calibration factors traceable to NIST, all of the above figures are increased by 1.1% because of the known differences between the NIST and NRC primary standards for air-kerma and absorbed dose to water[3]. Given that the uncertainties on the primary standards for absorbed dose

17

to water and air kerma are roughly equal, then by changing to TG-51 there is a clear increase in accuracy in the dose assigned in a 60Co beam since the uncertainty in TG-21 to convert from air kerma to absorbed dose is removed.

Furthermore there is a noticeable change in the assigned dose, which is a 1.1% larger change for calibration factors traceable to NIST. 2) For photon beams, TG-21 used stopping powers from ICRU Report 35 whereas the electron beam portion of the protocol used the more accurate and definitive values from ICRU Report 37[5]. TG-51 consistently uses Report 37 stopping powers which reduces the assigned dose in accelerator photon beams by up to 1.3% compared to TG-21.

3) TG-21 ignores the fact that many ion chambers have aluminum electrodes. Ma and Nahum[6] have done a complete set of calculations showing that such electrodes increase ion chamber response by up to 0.8%. Since this also affects air-kerma calibration factors, it is not a major effect in photon beams, but it does increase the dose assigned in high-energy photon beams by up to 0.3% and TG-51 takes this into account.

Fortunately, for accelerator photon beams these 3 effects tend to cancel and so the dose assigned in accelerator photon beams using TG-51 is about the same as that assigned with TG-21 when using NRC traceable calibration factors or

AAPM NEWSLETTER

SEPTEMBER/OCTOBER 2000

about 1% higher using NIST traceable factors. Ding et al[7] and Huq[8] have experimentally confirmed this.

Where does the improved accuracy come from for electron beams?

1) TG-21 was unclear about how to determine R 50, the depth at which the dose fell to 50% of its maximum. TG-51 has clarified and simplified this by requiring a measurement of I50, the depth at which the ionization drops to 50% and then uses a simple equation to get R50.

2) TG-21 used stoppingpower ratios calculated for mono-energetic electron beams but Ding et al[10] showed that these could lead to errors of up to 1.8%. TG-51 has overcome this shortcoming by changing to a new reference depth for electron beams at dref = 0.6 R50 - 0.1 cm.

This is at dose maximum for low-energy beams but deeper for high-energy beams. By making this change in the reference depth, the TG-51 protocol is able to use the stopping-power ratios calculated for the realistic electron beams and at the same time have a much simplified data set[11]. This reduces the dose assigned by up to 0.6% for low-energy electron beams and increases it by up to 1.2% for high-energy beams.

3) TG-51 takes into account the aluminum central electrode in many Farmer chambers and in electron beams this leads to a 0.7% increase in the assigned dose.

4) By avoiding the conversion from air to water based quantities in 60Co beams, TG51 makes the same gains in

accuracy for electron beams as outlined above for photon beams.

So the overall gain in accuracy in electron beams using TG-51 is increases in the doses of between 0% and 3% compared to TG-21, the larger changes being for measurements with chambers having aluminum electrodes at high energies. Ding et al have confirmed these expectations[7].

TG-51 recommends crosscalibrating plane-parallel chambers in high-energy electron beams but allows the use of 60Co calibrations of planeparallel chambers. This latter option is to meet US legal requirements and the crosscalibration technique is to be strongly encouraged in Canada since the data required to use the 60Co calibration factors are somewhat suspect[7](despite being my own calculations, and at the risk of reducing our calibration income!).

Why switch to using %dd(10)x from TPR20,10?

Perhaps the most controversial aspect of TG-51 concerns the issue of beam quality specification in photon beams. Why change?

Consider what happens if NRC measures a kQ factor for an NE2561 ion chamber in a beam with TPR20,10=0.792 and then asks the British standards lab (NPL) to do the same thing. The factors measured differ by 1.2%. If we now specify the beam qualities in the two labs using %dd(10)x we get agreement at the 0.1% level. This is because TPR20,10 does not specify the quality of the beams as well as %dd(10)x. If we now ask, How well does this NRC mea-

18

sured kQ agree with the value predicted by TG-51? the answer is, within 0.5% using %dd(10)x but it would disagree by 1.6% if TG-51’s physics were implemented using TPR20,10. The data are from Seuntjens et al[4] who also show that what occurs in this specific example (admittedly extreme) is generally true for different ion chambers and different laboratories. So the need for %dd(10)x is well established experimentally and was predicted by calculations in 1993[12].

Some claim that %dd(10)x is hard to measure because of electron contamination effects.

For beams with energies of 10 MV and above, one needs to insert a 1 mm lead sheet (being given away for free at the World Congress in Chicago) in the beam instead of measuring the depth-dose curve in the open beam. Then one uses a simple formula to deduce the value of %dd(10)x in the open beam taking into account the electron contamination generated by the lead and the hardening of the beam by the lead. If we assume that these Monte Carlo calculations are wrong by 50% (and we know they are more accurate than that!), then for a beam with %dd(10)x = 80%, the error in the assigned dose would be 0.17%. If we altogether ignore the electron contamination correction with the lead foil, the error in the assigned dose is 0.35%. So for an uncertainty concerning electron contamination effects of no more than a few tenths of a percent, we remove an uncertainty (when using measured values of kQ) of up to

AAPM NEWSLETTER

1.1% due to beam quality specification issues.

The Measured Values One distinct advantage of the TG-51 protocol over the TG-21 protocol is that the major factors (kQ, kecal and k’R50) can be measured directly using primary standards for absorbed dose to water whereas many factors in TG-21 are impossible to measure directly (eg, Ngas, Pwall, (L/ρ) etc). Seuntjens et al[4] have measured the most important of these, viz kQ, and report that for measurements with 20 ion chambers of 6 types at 3 energies, the rms deviation between TG51 values and measured values is 0.4%, which is comparable to the measurement uncertainty. This gives confidence in the use of these factors. One could, of course, also measure the overall accuracy of TG-21 and Seuntjens et al report that the rms deviation vs TG-21 is 1.7%. They also report that an optimal air-kerma based protocol has an rms deviation from their data of 0.7% (this means that the extra rms deviation introduced by using and airkerma based protocol is larger than the entire rms deviation using TG-51).

Conclusions The TG-51 protocol is not only easier to use than TG-21, it is more accurate and has been experimentally verified for photon beams. The hope is that once it is fully implemented in Canada there will be an improvement in radiotherapy, if only because TG-51 will save overworked medical physicists some time, while at the same time improving accu-

racy in the doses they assign and minimizing the chances of mistakes.

[1] P. R. Almond et al, AAPM’s TG—51 Protocol for Clinical Reference Dosimetry of High-Energy Photon and Electron Beams, Med. Phys.

26, 1847 (1999).

[2] D. W. O. Rogers, The advantages of absorbed-dose calibration factors, Med. Phys.

19, 1227 (1992).

[3] K. Shortt et al, Comparison of Dosimetry Calibration Services at the NRCC and the NIST, Med. Phys. 27, 1644 (2000).

[4] J. P. Seuntjens et al, Absorbed-dose beam quality conversion factors for cylindrical chambers in high-energy photon beams, Med. Phys., submitted Nov. (1999).

[5] D. W. O. Rogers et al, Comments on the 60-Co Graphite/Air Stopping-Power Ratio used in the AAPM Protocol, Med. Phys. 13, 964 (1986).

[6] C. M. Ma et al, Effect of size and composition of central electrode on the response of cylindrical ionization chambers in high-energy photon and electron beams, Phys.

Med. Biol. 38, 267 (1993).

[7] G. X. Ding et al, Clinical reference dosimetry: Comparison between AAPM TG-21 and TG-51 protocols, Med. Phys., 27 1217 (2000).

[9] M. S. Huq, An Evaluation of the Recommendations of the AAPM TG—51 Protocol: Photon Beam Comparison with the TG—21 Protocol, Med. Phys.(abs) 26, 1154 (1999).

[10] G. X. Ding et al, Calculation of stopping-power ratios

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SEPTEMBER/OCTOBER 2000

using realistic clinical electron beams, Med. Phys. 22, 489 (1995).

[11] D. T. Burns et al, R50 as a beam quality specifier for selecting stopping-power ratios and reference depths for electron dosimetry, Med. Phys.

23, 383 (1996).

[12] A. Kosunen et al, Beam Quality Specification for Photon Beam Dosimetry, Med. Phys. 20, 1181(1993).24

Reprinted with permission from Interactions Vol. 46 (2000).

Vol

AAPM NEWSLETTER

SEPTEMBER/OCTOBER 2000

Implementation of TG-51: Practical Considerations

by Jessica Lowenstein Radiological Physics Center Houston, TX Last year the AAPM published a new protocol for the calibration of high-energy photon and electron radiotherapy beams (Medical Physics 26, p1847-1870, 1999). As physicists have begun to implement TG-51, many questions have arisen, including (1) What changes should one expect when converting from TG-21 to TG-51? (2) Is a 1mm thick sheet of lead necessary in the determination of beam quality [%dd(10)x] for photon energies ≥ 10 MV? (3) Is measurement of polarity effect necessary every time that reference dosimetry is done? (4) Do I need to re-measure all of my photon depth dose data? In preparation for on-site institutional dosimetry reviews and audits using the TG-51 protocol, the Radiological Physics Center (RPC) has investigated these questions.

TG-51/TG-21 To determine the magnitude of the change in beam calibration, the RPC compared dose rates determined in a water phantom using TG-21 to those determined using TG-51 for several photon and electron energies. The results were published in the new electronic jour nal, which can be accessed through www.acmp.org, which has a link to the journal. (S. Cho et al., Journal of Applied Clinical

Medical Physics 1 (3), Summer 2000). We determined that the change from TG-21 to TG-51 would result in up to a 1% increase in measured output (Gy to water/MU at dmax) for photons and up to a 2% increase for electrons. Physicists may discover either larger or smaller differences between the two protocols depending on their current calibration techniques. If these changes are greater then 2.5%, it is recommended that physicists contact the RPC before implementing the protocol. Before making the conversion to TG51, be sure to notify all personnel involved at your facility of the magnitude of these changes.

Lead Foil To examine the uncertainty introduced by determining the photon beam quality, %dd(10)x, using open field depth dose and the interim equation (eq. 15 in the protocol) rather than depth dose with the lead foil, the RPC evaluated kQ both ways for 10 MV through 23 MV photon beams produced by several LINAC models. The data collected to date include several units with tertiary multi-leaf collimators, where the recommended minimum of 45 cm between the distal aspect of the collimator assembly and the water surface could not be met. Of the beams measured to date, the maximum difference in %dd(10)x determined with and without lead was 1.5%, leading to a change in kQ

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of 0.2%. Although the Radiation Therapy Committee approved the RPC to use the no lead depth dose as an appropriate operational approximation, at this time, the RPC will continue to use the 1 mm lead sheet to determine %dd(10)x for photon energies ≥ 10 MV for on-site dosimetry visits to collect further data on a wider selection of therapy machines.

Polarity Effects To assess whether polarity effects measurements must be per for med during each dosimetry review visit, the RPC measured polarity correction factors, Ppol,, for a selection of Farmer-type cylindrical chambers and two parallel plate chambers (for electrons only) on different machine models.

Data was obtained from our previous comparison of TG21 and TG51 (S. Cho et al., Journal of Applied Clinical Medical Physics 1 (3), Summer 2000) and from measurements performed by RPC physicists during on-site review visits. For photon energies and for electron energies ≥ 12 MeV the polarity correction was found to be 1.000 ± 0.001. For electron energies < 12 MeV, the polarity correction is measurable for both cylindrical and parallel plate chambers. The RPC reminds the community that an ionization chamber, like any other new piece of equipment, needs to be accepted/commissioned. For ion chambers, this commissioning should include an

AAPM NEWSLETTER

assessment of the polarity effects for all beam energies and modalities to be measured. For that ion chamber an informed decision can then be made as to which energies and modalities require polarity corrections. The RPC has adopted the following policy concerning polarity correction for its on-site review visits: (1) A polarity correction of 1.000 will be used for all photon energies and for electron energies ≥ 12 MeV. (2) For electron energies < 12 MeV the RPC will measure the polarity correction.

Photon Depth Dose Data TG-51 states that relative depth dose data for photon beams are obtained by measuring relative depth ioniza-

tion and shifting these data to the effective point of measurement. Since the dose conversion factors are independent of depth, this shifted depth ionization curve becomes a depth dose curve. Many therapy beams have been commissioned using a cylindrical ion chamber to measure depthdose without shifting depth to the effective depth. Since the gradient of the depth dose curve is nearly constant with depth; and, if the depth dose curve used clinically is used to convert dose from the calibration depth (10 cm) to the reference depth (dmax or other), then the use of “unshifted depth dose data” increases the uncertainty in the dose only near dmax. Therefore, if this additional uncertainty near dmax (which exists with the

SEPTEMBER/OCTOBER 2000

present dosimetry system) is acceptable, it may not be necessary to re-measure depth dose data or apply effective point of measurement corrections to the raw data.

Please feel free to contact the RPC at (713) 792-3226 with questions and problems if you need assistance.

J. Lowenstein P. Balter S. Cho and Radiological Physics Center We also would like to acknowledge the other RPC and ADCL physicists: D. Followill, J.F. Aguirre, R. Tailor, J.A. BenComo, N. Wells, and W. Hanson.

New Members Associate Toth, Thomas Milwaukee, WI Corresponding Huisman, Henkjan Nymegen, NETHERLANDS Khoo, Benjamin Cheng Choon Singapore, SINGAPORE Zonneveld, Guido Antoine Amsterdam, NETHERLANDS Franco, Maria Del Carmen Monterrey, MEXICO

Gonzalez Lopez Antonio

Weigl, Gisbert Schwerin, GERMANY

DuBose, James Michael Snellville, GA

Full

Efros, Charlotta

Able, Charles Reno, NV

Annadale, VA

Alkhatib, Hassaan Columbia, SC

Frensemeier, Jeffrey Robert Lutherville, MD

Bailey, Colin Scio, N Boylan, Eugene James Portland, ME

Van Kleffens, Herman Helmond, NETHERLANDS

Gaiser, James Concord, NC Gates, Vanessa Royal Oak, MI

Butts, Kim Stanford, CA

Valencia, SPAIN

Powley, Sally Kathryn Lincoln Lincolnshire, CANADA

Francescon, Paolo Vicenza, ITALY

Cavedon, Carlo Vicenza, ITALY Chapel-Gomez, Maria Luisa Santa Cruz Tenerife, SPAIN

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Hearn, Robert Andre Roswell, GA Holupka, Edward Medway, MA

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SEPTEMBER/OCTOBER 2000

Joshi, Chandra Prakash Kingston, ON, CANADA

Peters, Dana Bethesda, MD

Li, Texin Gainesville, FL

Kamman, Richard Groningen, NETHERLANDS

Readshaw, Amy Beaver, PA

Mader, Brian Kevin Decatur, GA

Karaoglan, Eser Fresno, CA

Tirawongkusol, Kitiwan Arlington, TX

Naughton, John Patrick Gainesville, FL

Kennelly, Timothy Edward Ballston Lake, NY

Trail, Cheryl Haddonfield, NJ

Rhoades IV, Samuel James San Antonio, TX

Krieman, Christine Buford, GA

Student

Leblanc, Philippe St Luc, QC, CANADA Marcu, Silviu-Marcel Cleveland, OH Morrison, Paul Richard Boston, MA Nelson, Kevin Jacksonville, FL Nichols, Trent Lee Knoxville, TN Ocasio, Michael San Diego, CA Salem, Mohamed Shaaban Hawalli, KUWAIT Smith, Jacqualyn Knoxville, TN Stasi, Michele Torino, ITALY Strash, Alfred Midlothian, VA Tuy, Heang Shenyang Liaoning, PEOPLES REPUBLIC OF CHINA Young, Lori Seattle, WA

Junior

Aydogan, Bulent Gainesville, FL Barnhart, Todd Denver, CO Beach, Stephen Mark Madison, WI Boccaletti, Karina Sao Paulo, BRAZIL Booth, Jeremy Todd ADELAIDE, AUSTRALIA Brodeur, Marylene Montreal, QC, CANADA Bulut, Ahmet Baton Rouge, LA Dorbu, Godwin Toledo, OH Gilardi, Azita Tarzana, CA Hutchinson, Della Philadelphia, PA Hugo, Geoffrey Douglas Los Angeles, CA Jirasek, Andrew Vancouver, BC, CANADA

Keister, Justin Mark Lexingotn, KY

La Shell, Sean James Boston, MA

Koch, Nicholas Corey Houston, TX

Myler, Uwe Kurt Hamilton, ON, CANADA

Lee, Michael Chun-Chieh Stanford, CA

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Tarik

Shen, Bin Omaha, NE Stewart, Kristin Joy Montreal, QC, CANADA Stiles, Timothy Allen Madison, WI Wilson, Kathryn Ellen Gainesville, FL Yoe-Sein, Maung Lexington, KY Zalzberger, Shamay Petah Tikva, ISRAEL

Â&#x201E;

AAPM NEWSLETTER

SEPTEMBER/OCTOBER 2000

2001 AAPM Summer School June 23-28, 2001

Accreditation Programs and the Medical Physicist University of Washington Seattle, Washington Mark your calendars!

Donâ&#x20AC;&#x2122;t miss this one! Get inside information on ACR accreditation programs: understand the details of required physics testing and participation, as well as clinical and administrative requirements.

Learn the latest about JCAHO accreditation and deemed status accreditation in Radiation Oncology and in other areas.

Learn about the business side of accreditation: economics and relationships to reimbursement and turf. Review basic physics in the various areas. Be the first on your block to see details of new accreditation programs in Radiography and Fluoroscopy, CT, and Interventional Radiology. Pick up a few CME hours in mammography while you enjoy beautiful Seattle.

Program summary: Overview of ACR accreditation programs- the big picture MRI accreditation: Phantom tests and physics behind

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them; Physics of a QC program; trouble-shooting using the physics tests.

CT accreditation: Physics related to testing, CT phantom and tests.

Ultrasound accreditation, Radiation Oncology accreditation, Nuclear Medicine accreditation, JCAHO accreditation, Mammography accreditation:High level trouble-shooting, digital mammography, stereotactic biopsy.

Radiography and Fluoroscopy accreditation: The new ACR R/F phantom, required physics tests, etc.

AAPM NEWSLETTER

SEPTEMBER/OCTOBER 2000

AAPM NEWSLETTER MANAGING EDITOR Marsha Dixon

EDITOR-IN-RESIDENCE Robert Dixon Send information to: Marsha Dixon Broadcast News Public Relations 201 Knollwood Street Winston-Salem, North Carolina 27104 (336) 721-9171 Phone (336) 721-0833 Fax Email: rdixon@wfubmc.edu The AAPM newsletter is printed bi-monthly. Deadline to receive material for consideration is four to six weeks before mailing date. We welcome your entries, and encourage authors of articles to supply a photo. Please send material via e-mail, disks or mail. Faxes are encouraged as back-up, and are acceptable alone.

NEXT ISSUE November/December, 2000

DEADLINE October 15,2000

MAIL DATE November 15, 2000

Editorial Board Benjamin Archer Bruce Curran Don Frey John Kent Richard Morin Alfred Smith

AMERICAN ASSOCIATION OF PHYSICISTS IN MEDICINE One Physics Ellipse College Park, Maryland 20740-3846 (301) 209-3350 Phone (301) 209-0862 Fax e-mail: aapm@aapm.org http://www.aapm.org

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