Basics of Radiology_Herman Miroslav

Miroslav Heřman et al.

Basics of Radiology

Miroslav Heřman et al.

Basics of Radiology

Reviewers: prof. MUDr. Vlastimil Válek, CSc., MBA, EBIR prof. MUDr. Jiří Neuwirth, CSc., MBA Authors: doc. MUDr. Stanislav Buřval, Ph.D. doc. MUDr. Marie Černá, Ph.D. MUDr. Filip Čtvrtlík, Ph.D. MUDr. Radka Dusíková MUDr. Martin Hazlinger prof. MUDr. Miroslav Heřman, Ph.D. prof. MUDr. Martin Köcher, Ph.D. MUDr. Kamila Michálková MUDr. Kateřina Spáčilová MUDr. Zbyněk Tüdös, Ph.D. MUDr. Lucia Veverková, Ph.D. doc. MUDr. Jaroslav Vomáčka, Ph.D., MBA

prof. MUDr. Miroslav Heřman, Ph.D. et al.

Basics of Radiology Executive editor prof. RNDr. Hana Kolářová, CSc. In-house editor Mgr. Tereza Vintrová Translation Martin Štěrba, Simon Gill Layout Petr Jančík Cover doc. Ondřej Michálek Published by Palacký University Olomouc Křížkovského 8, 771 47 Olomouc vydavatelstvi.upol.cz Printed by Profi-tisk group s.r.o.

Chválkovická 223/5, 77900 Olomouc 1st English Edition Translation from the 2014 Czech Edition “Základy radiologie” (ISBN 978-80-244-2901-4) © Miroslav Heřman et al., 2021 © Palacký University Olomouc, 2021 Translation © Martin Štěrba, Simon Gill, 2021 Olomouc 2021 All rights reserved. No part of this publication may be reproduced in any form without the prior permission of the Publisher.

Unauthorized use of this work is an off ence under the Copyright Act. VUP 2017/0165 (print) VUP 2020/0437 (online: PDF) ISBN 978-80-244-5697-3 (print) ISBN 978-80-244-5837-3 (online: PDF)

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Contents List of Abbreviations ........................................... 10 1. Introduction.................................................... 11 1.1 1.2 1.3 1.4

Origin and Properties of X-rays............................ 11 Biological Effects of X-rays .................................... 11 Principles of Radiation Protection ....................... 11 Overview of Doses in Radiological Examinations............................................................ 12 1.5 Request for Radiological Examination................. 13 1.6 Radiological Report................................................. 13

2. Imaging Methods............................................ 14 2.1 Radiography............................................................. 14 2.2 Fluoroscopy ............................................................. 15 2.3 Tomography, Tomosynthesis.................................. 16 2.4 Angiography............................................................. 16 2.5 Ultrasonography (US)............................................. 17 2.6 Computed Tomography (CT)................................ 21 2.7 Magnetic Resonance (MR)..................................... 25 2.7.1 Magnetic Resonance Imaging (MRI)......... 26 2.7.2 Magnetic Resonance Angiography (MRA)............................................................ 29 2.7.3 Magnetic Resonance Spectroscopy (MRS)............................................................. 30 2.7.4 Functional Magnetic Resonance Imaging (fMRI)............................................................. 30 2.7.5 Other Types of MR Examinations.............. 31 2.8 Picture Archiving and Communication Systems – PACS....................................................... 32

3. Contrast Media............................................... 33 3.1 Positive CM.............................................................. 33 3.1.1 Barium CM.................................................... 33 3.1.2 Iodine CM...................................................... 33 3.2 Negative CM............................................................. 35 3.3 Double Contrast Examination............................... 35 3.4 Contrast Media for Ultrasonography.................... 35 3.5 Magnetic Resonance Contrast Media................... 36

4. Thorax.............................................................. 37 4.1 Imaging Anatomy.................................................... 37 4.2 Imaging Methods..................................................... 40 4.2.1 Chest Radiograph.......................................... 40 4.2.2 Computed Tomography (CT)..................... 40 4.2.3 Angiographic Methods................................. 42 4.2.4 Ultrasonography............................................ 42 4.2.5 Magnetic Resonance..................................... 42 4.2.6 Nuclear Medicine Methods......................... 43 4.2.7 Intervention Radiology Methods................ 43 4.2.8 Other Imaging Methods............................... 43 4.3 General Signs of Pathological Changes................ 43

4.3.1 Symptoms of Lung Diseases........................ 43 4.3.2 Changes in the Hila and Pulmonary Vasculature .................................................... 48 4.3.3 Changes in the Diaphragm and Diaphragm Angles........................................ 49 4.3.4 Changes in the Heart and Mediastinum.... 49 4.3.5 Changes in the Skeleton of the Thorax....... 52 4.3.6 The Main Differences in Radiographs Taken of a Standing or Supine Patient........ 52 4.4 Evaluation and Examination Report..................... 53 4.4.1 Radiograph..................................................... 53 4.4.2 CT.................................................................... 53 4.5 Pulmonary Inflammation ...................................... 54 4.5.1 Pneumonia, Bronchopneumonia................ 54 4.5.2 Atypical Pneumonia, Mycotic and Parasitic Lung Disease.................................. 54 4.5.3 Complications of pulmonary inflammation................................................. 56 4.5.4 Pulmonary Tuberculosis ............................. 58 4.5.5 Chronic Obstructive Pulmonary Disease............................................................ 59 4.6 Diffuse Interstitial Lung Disease........................... 59 4.6.1 Pneumoconioses........................................... 60 4.6.2 Sarcoidosis..................................................... 61 4.6.3 Hypersensitivity Pneumonitis (HP)........... 62 4.6.4 Pulmonary Fibrosis....................................... 62 4.7 Tumours of the Lungs and Bronchi....................... 64 4.7.1 Bronchogenic Carcinoma............................ 64 4.7.2 Metastases in the Lungs................................ 65 4.7.3 Intra-thoracic Lymphomas and Leukaemia...................................................... 67 4.7.4 Benign Lung Tumours.................................. 68 4.8 Pulmonary Circulatory Disorders......................... 68 4.8.1 Congenital Anomalies.................................. 68 4.8.2 Pulmonary Embolism.................................. 68 4.8.3 Pre-capillary Pulmonary Hypertension..... 68 4.8.4 Pulmonary Oedema (Post-capillary Pulmonary Hypertension)........................... 69 4.9 The Heart.................................................................. 71 4.9.1 Congenital Malformations........................... 71 4.9.2 Heart Failure.................................................. 71 4.9.3 Diseases of Valves.......................................... 71 4.9.4 Bacterial Endocarditis.................................. 71 4.9.5 Myxoma and Other Intra-cardial Expansions..................................................... 71 4.9.6 Ischaemic Heart Disease, Myocardial Infarction........................................................ 72 4.9.7 Hypertension................................................. 72 4.9.8 Pericardial Disease........................................ 72 4.10 Diseases of the Mediastinum................................. 72 4.10.1 Expansion in the Mediastinum................ 72 4.10.2 Mediastinitis............................................... 73

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Contents 4.11 Pleural Diseases....................................................... 73 4.11.1 Pleural Fluid.............................................. 73 4.11.2 Pneumothorax........................................... 75 4.11.3 Pleural Thickening.................................... 75 4.11.4 Pleural Tumours....................................... 75 4.12 Chest Injuries........................................................... 75

5. Musculoskeletal System................................. 79 5.1 Imaging Anatomy.................................................... 79 5.2 Imaging Methods..................................................... 82 5.2.1 Radiography................................................... 82 5.2.2 Computed Tomography .............................. 82 5.2.3 Ultrasonography ........................................... 82 5.2.4 Magnetic Resonance..................................... 83 5.2.5 Nuclear Medicine Methods......................... 83 5.2.6 Arthography................................................... 83 5.2.7 Densitometry................................................. 83 5.2.8 Interventional Radiology Methods............. 83 5.3 General Signs of Pathological Changes................ 83 5.3.1 Symptoms of Skeletal Affection.................. 83 5.3.2 Symptoms of Soft Tissue Disorders............ 85 5.4 Evaluation and Examination Report..................... 87 5.4.1 Radiographs................................................... 87 5.4.2 Other Imaging Methods............................... 87 5.5 Injuries...................................................................... 87 5.5.1 Bones.............................................................. 87 5.5.2 Joints............................................................... 91 5.5.3 Soft Tissues of Joints..................................... 92 5.5.4 Muscles and Tendons................................... 94 5.6 Degenerative Joint Diseases – Osteoarthritis....... 94 5.7 Bone and Joint Inflammations............................... 95 5.7.1 Bone Inflammation – Osteomyelitis........... 95 5.7.2 Joint Inflammations – Arthritis.................. 96 5.8 Bone Tumours........................................................ 100 5.8.1 Osteogenic Tumours................................... 102 5.8.2 Chondrogenic Tumours............................. 102 5.8.3 Osteoclastoma (Giant Cell Tumour)........ 103 5.8.4 Bone-Marrow Tumours.............................. 103 5.8.5 Vascular Tumours....................................... 104 5.8.6 Secondary Bone Tumours (Metastases)... 104 5.8.7 Bone Pseudotumours................................. 104 5.9 Tumours of Soft Tissues........................................ 108 5.9.1 Benign Tumours.......................................... 108 5.9.2 Malignant Tumours.................................... 108 5.10 Other Osteopathies............................................... 108 5.10.1 Circulation Disorders.............................. 108 5.10.2 Metabolic and Hormonal Osteopathies............................................. 109 5.10.3 Other Bone Diseases................................ 111

6. Gastrointestinal Tract (GIT)........................ 112 6.1 Imaging Anatomy.................................................. 112 6.2 Imaging Methods................................................... 114 6.2.1 Examinations Using Contrast Media ...... 115 6.2.2 Ultrasonography.......................................... 117

6.3

6.4

6.5

6.6

6.7

6.8

6.9

6.2.3 Computed Tomography (CT)................... 118 6.2.4 Magnetic Resonance................................... 120 6.2.5 Interventional Radiology Methods........... 120 6.2.6 Radiograph................................................... 121 General Signs of Pathological Changes of the Gastrointestinal Tract in an Examination with CM........................................................................... 121 Assessment and Examination Report................. 122 6.4.1 Examination with Contrast Media........... 122 6.4.2 Ultrasonography.......................................... 123 6.4.3 CT/MR......................................................... 123 Diseases of the Pharynx and Oesophagus.......... 123 6.5.1 Inflammation of the Oesophagus............. 123 6.5.2 Retropharyngeal Abscess........................... 124 6.5.3 Oesophageal manifestations of the systemic autoimmune diseases.................. 124 6.5.4 Hypopharyngeal Tumours......................... 124 6.5.5 Oesophageal Tumours................................ 124 6.5.6 Diverticula of the Oesophagus.................. 125 6.5.7 Achalasia...................................................... 126 6.5.8 Gastro-Oesophageal Varices...................... 126 6.5.9 Oesophageal Perforation............................ 126 Stomach and Duodenal Disorders...................... 126 6.6.1 Inflammatory Diseases of the Stomach and Duodenum........................................... 126 6.6.2 Tumours of the Stomach and Duodenum................................................... 128 6.6.3 Hiatus Hernia.............................................. 129 6.6.4 Blunt Duodenal Injury............................... 130 6.6.5 Duodenal Diverticula................................. 130 Small Bowel Disease.............................................. 131 6.7.1 Inflammatory Diseases of the Small Bowel............................................................ 131 6.7.2 Malabsorption Syndrome.......................... 132 6.7.3 Tumours of the Small Bowel...................... 132 6.7.4 Meckel’s Diverticulum................................ 132 Diseases of the Colon............................................ 132 6.8.1 Inflammatory Diseases of the Colon........ 132 6.8.2 Tumours of the Large Bowel...................... 134 6.8.3 Colonic Diverticulosis................................ 136 6.8.4 Anorectal Dysfunctions............................. 137 Evaluation of Post-operative Conditions of the Gastrointestinal Tract............................................ 137

7. Liver, Bile Ducts, Pancreas, and Spleen...... 139 7.1 Liver......................................................................... 139 7.1.1 Imaging Methods........................................ 139 7.1.2 Hepatic Steatosis.......................................... 140 7.1.3 Cirrhosis....................................................... 140 7.1.4 Portal Hypertension.................................... 141 7.1.5 Liver Cysts.................................................... 141 7.1.6 Liver Abscess .............................................. 141 7.1.7 Liver Tumours............................................. 142 7.1.8 Injuries.......................................................... 143 7.2 Gallbladder and Bile Ducts.................................. 145

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Contents

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7.2.1 Imaging Methods........................................ 145 7.2.2 Cholecystolithiasis...................................... 146 7.2.3 Choledocholithiasis.................................... 147 7.2.4 Cholecystitis................................................. 147 7.2.5 Cholangitis................................................... 148 7.2.6 Tumours....................................................... 148 7.2.7 Icterus........................................................... 148 7.2.8 Postoperative Complications..................... 149 7.3 Pancreas.................................................................. 149 7.3.1 Imaging Methods........................................ 149 7.3.2 Acute Pancreatitis........................................ 149 7.3.3 Chronic Pancreatitis................................... 150 7.3.4 Tumours of the Pancreas............................ 150 7.4 Spleen...................................................................... 151 7.4.1 Imaging Methods........................................ 151 7.4.2 Splenomegaly............................................... 151 7.4.3 Expansion..................................................... 151 7.4.4 Injuries.......................................................... 152

8. Abdominal Trauma and Acute Abdomen....................................................... 153 8.1 Abdominal Trauma .............................................. 153 8.2 Acute Abdomen..................................................... 153 8.2.1 Inflammatory Acute Abdomen................. 154 8.2.2 Bowel Obstruction and Ileus..................... 155 8.2.3 Bleeding........................................................ 158

9. Urinary System, Sex Organs in Men, Retroperitoneum.......................................... 160 9.1 Imaging Anatomy.................................................. 160 9.2 Imaging Methods................................................... 162 9.2.1 Ultrasonography.......................................... 162 9.2.2 Computed Tomography............................. 163 9.2.3 Radiography................................................. 163 9.2.4 Intravenous Urography (IVU)................... 163 9.2.5 Voiding Cystourethrography..................... 163 9.2.6 Digital Subtraction Angiography, Interventional Radiology........................... 163 9.2.8 Magnetic Resonance................................... 163 9.3 Evaluation and Examination Report................... 163 9.4 Congenital Anomalies and Variants................... 164 9.5 Acquired Anomalies of Kidney Position ........... 165 9.6 Urolithiasis............................................................. 166 9.7 Obstructive Uropathy........................................... 166 9.8 Renal masses.......................................................... 167 9.9 Tumours of the Renal Pelvis, Ureter, and Urinary Bladder ............................................. 170 9.10 Acute Inflammatory Diseases of the Kidney.... 170 9.11 Chronic Inflammatory Diseases of the Kidney and Urinary Tract................................... 170 9.12 Urinary Tract Trauma.......................................... 172 9.13 Renovascular Hypertension................................ 172 9.14 Transplanted Kidney............................................ 172 9.15 Prostate Disease.................................................... 173 9.16 Diseases of the Testicles and Epididymis ......... 173

9.17 Adrenal Diseases.................................................. 173 9.18 Other Retroperitoneal Diseases......................... 175

10. Neuroradiology – Brain, Skull..................... 176 10.1 Imaging Anatomy................................................. 176 10.2 Imaging Methods................................................. 178 10.2.1 Computed Tomography........................... 179 10.2.2 Magnetic Resonance................................ 179 10.2.3 Angiography.............................................. 179 10.2.4 Ultrasonography....................................... 179 10.2.5 Radiography.............................................. 179 10.3 General Signs of Pathological Changes............. 179 10.3.1 Symptoms of Brain Pathology................ 179 10.3.2 Symptoms of Pathologies of Spaces Filled with Cerebrospinal Fluid (CSF) ......................................................... 180 10.3.3 Symptoms of Pathology of the Cerebral Meninges .................................. 181 10.3.4 Symptoms of Vascular Impairment....... 182 10.4 Assessment and Examination Report................ 182 10.5 Congenital Varieties and Anomalies................. 182 10.6 Head and Brain Trauma...................................... 183 10.6.1 Skeletal Injury........................................... 184 10.6.2 Brain Injuries............................................ 184 10.6.3 Extracerebral Traumatic Haemorrhage............................................ 186 10.6.4 Other Traumatic Intracranial Changes...................................................... 187 10.7 Stroke..................................................................... 188 10.7.1 Ischaemic Stroke ...................................... 188 10.7.2 Haemorrhagic Stroke .............................. 189 10.8 Tumours................................................................ 191 10.9 Inflammations....................................................... 194 10.10 Diseases of the White Matter........................... 195 10.11 Diseases of Cerebral Vessels............................. 195 10.12 Degenerative Diseases of the Brain................. 197

11. Neuroradiology – Spine, Spinal Cord......... 199 11.1 Imaging Anatomy................................................. 199 11.2 Imaging Methods................................................. 201 11.2.1 Radiography.............................................. 201 11.2.2 Computed Tomography........................... 201 11.2.3 Magnetic Resonance................................ 202 11.3 General Signs of Pathological Changes............. 202 11.3.1 Symptoms of Skeletal Pathology............. 202 11.3.2 Signs of Intervertebral Discs Pathology .................................................. 202 11.3.3 Symptoms of Spinal Canal and Its Content Pathology.................................... 202 11.4 Evaluation and Examination Report................. 205 11.5 Congenital Variations and Anomalies............... 205 11.6 Trauma of the Spine and Spinal Cord ............... 206 11.7 Tumours................................................................ 208 11.8 Degenerative Diseases......................................... 210 11.9 Inflammatory Diseases........................................ 214

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Contents

12. Head and Neck Radiology .......................... 215 12.1 Imaging Anatomy................................................. 215 12.2 Imaging Methods................................................. 218 12.2.1 Ultrasonography....................................... 218 12.2.2 Computed Tomography........................... 218 12.2.3 Magnetic Resonance................................ 219 12.2.4 Radiography.............................................. 219 12.2.5 Contrast Examination.............................. 219 12.2.6 Interventional Methods........................... 219 12.2.7 Nuclear Medicine Methods..................... 219 12.3 Evaluation and Examination Report................. 219 12.4 Thyroid Gland, Parathyroid Glands................... 220 12.5 Cervical Lymphadenopathy................................ 221 12.6 Other Expansions in the Neck............................ 221 12.7 Tumours of the Maxillofacial Region................ 222 12.8 Larynx, Pharynx................................................... 222 12.9 Paranasal Sinuses.................................................. 224 12.10 Temporal Bone................................................... 225 12.11 Large Salivary Glands........................................ 226 12.12 Orbits................................................................... 227 12.13 Facial Injuries..................................................... 228

13. Breast Imaging.............................................. 230 13.1 Imaging Anatomy................................................. 230 13.2 Imaging Methods................................................. 231 13.2.1 Mammography (MG).............................. 231 13.2.2 Ultrasonography (US).............................. 231 13.2.3 Magnetic Resonance................................ 231 13.2.4 Ductography............................................. 232 13.2.5 Nuclear Medicine Methods..................... 232 13.2.6 Biopsy......................................................... 232 13.3 General Signs of Pathological Changes............. 234 13.4 Evaluation and Examination Report ................ 234 13.5 Inflammatory Diseases of the Breast................. 235 13.6 Benign Breast Lesions.......................................... 236 13.7 Malignant Breast Tumours.................................. 236

14. Radiodiagnostics in Gynaecology and Obstetrics....................................................... 239 14.1 Imaging Anatomy................................................. 239 14.2 Imaging Methods................................................. 240 14.3 Evaluation and Examination Report................. 241 14.4 Imaging during Pregnancy................................. 241 14.5 Imaging in the Evaluation of Infertility............. 243 14.6 Inflammations of the Uterus and Adnexa, Endometriosis....................................................... 243 14.7 Cystic and Tumourous Affections of the Uterus and Adnexa........................................................... 243

15. Arterial System.............................................. 245 15.1 Imaging Anatomy................................................. 245 15.2 Imaging Methods................................................. 248 15.2.1 Digital Subtraction Angiography (DSA)......................................................... 248

15.2.2 Doppler Ultrasonography....................... 250 15.2.3 CT Angiography (CTA)........................... 251 15.2.4 MR Angiography (MRA)........................ 253 15.2.5 Radiograph................................................ 254 15.3 General Signs of Pathological Changes............. 255 15.3.1 Pathological Findings in Arteriography (DSA, CTA, and MRA)............................ 255 15.3.2 Pathological Findings in US.................... 259 15.4 Evaluation and Examination Report................. 259 15.5 Pathological Conditions of the Aortic Arch and Arteries of the Head (Brain and Face) and Neck.................................. 260 15.5.1 Pathological Conditions of the Aortic Arch............................................................ 260 15.5.2 Pathological Conditions of the Arteries of the Neck and Face................. 260 15.5.3 Pathological Conditions of the Intracranial Vasculature.......................... 261 15.5.4 Detection of Brain Death........................ 261 15.6 Pathological Conditions of Upper Extremity Arteries.................................................................. 262 15.7 Pathological Conditions of the Heart and Coronary Arteries................................................ 262 15.7.1 Pathological Conditions of the Heart.... 262 15.7.2 Pathological Conditions of Coronary Arteries...................................................... 263 15.8 Pathological Conditions of the Thoracic Aorta and Medullary and Spinal Arteries ................... 263 15.9 Pathological Conditions of Splanchnic Arteries.................................................................. 263 15.10 Pathological Conditions of Renal Arteries..... 264 15.11 Pathological Conditions of the Abdominal Aorta, Pelvic, and Lower Extremity Arteries................................................................ 264 15.12 Pathological Conditions of the Pulmonary Arteries................................................................ 265

16. Venous System.............................................. 266 16.1 Imaging Anatomy................................................. 266 16.2 Imaging Methods................................................. 268 16.2.1 Doppler Ultrasonography....................... 268 16.2.2 Venography (Phlebography)................... 268 16.2.3 CT Venography and MR Venography... 269 16.2.4 Radiograph................................................ 270 16.3 General Signs of Pathological Changes............. 270 16.3.1 Pathological Findings in US.................... 270 16.3.2 Pathological Findings in Venography.... 271 16.4 Evaluation and Examination Report................. 271 16.5 Venous Thrombosis............................................. 271 16.6 Occlusion of the Superior or Inferior Vena Cava.............................................................. 271 16.7 Examination of the Venous System of the Upper Extremities before the Implantation of a Dialysis Shunt ................................................... 271 16.8 Portal Hypertension............................................. 272

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17. Lymphatic System......................................... 273 17.1 Imaging Anatomy................................................. 273 17.2 Imaging Methods................................................. 274 17.2.1 Ultrasonography....................................... 274 17.2.2 Computed Tomography........................... 274 17.2.3 Magnetic Resonance................................ 274 17.2.4 Nuclear Medicine Methods..................... 274 17.3 Evaluation and Examination Report ................ 274 17.4 Lymphadenopathy................................................ 274 17.5 Lymphocele........................................................... 276

18. Interventional Radiology............................. 277 Vascular Interventions.................................................. 277 18.1 Recanalization Interventions............................... 277 18.1.1 Percutaneous Transluminal Angioplasty (PTA).................................... 277 18.1.2 Subintimal Angioplasty........................... 279 18.1.3 Stents in the Vascular System.................. 280 18.1.4 Local Thrombolysis.................................. 282 18.1.5 Mechanical Thrombectomy.................... 282 18.2 Reconstruction Interventions.............................. 282 18.2.1 Endovascular Treatment of Arterial Aneurysms, Pseudoaneurysms, and Arteriovenous Fistulas with Stent Grafts.......................................................... 282 18.3 Transcatheter Embolization Methods................. 284 18.3.1 Chemotherapy and Chemoembolization of Liver Metastases................................... 285 18.3.2 Preoperative Embolization of the Portal Vein................................................. 285 18.3.3 Embolization of Acute Bleeding into the GIT....................................................... 287 18.3.4 Endovascular Treatment of Haemobilia................................................ 287 18.3.5 Endovascular Treatment of Vascular Trauma....................................................... 287 18.3.6 Sclerotherapy of Peripheral Vascular Malformations.......................................... 288 18.3.7 Endovascular Embolization Methods in Neuroradiology......................................... 289 18.4 Inferior Vena Cava Filters..................................... 290

18.5 Transjugular Intrahepatic Portosystemic Shunt (TIPS)........................................................... 291 Non-Vascular Interventions......................................... 291 18.6 Percutaneous Biopsy............................................ 291 18.7 Percutaneous Aspiration and Drainage of Fluid Collections and Abscesses......................... 292 18.8 Radiofrequency Ablation.................................... 293 18.9 Interventions in the Biliary Tract....................... 293 18.9.1 Percutaneous Transhepatic Drainage of the Biliary Tract (PTD)....................... 293 18.9.2 Dilation of Stenoses of the Biliary Tract........................................................... 294 18.9.3 Percutaneous Extraction of Stones from the Biliary Tract............................... 294 18.10 GIT Interventions ............................................. 294 18.10.1 Dilatation of GIT Stenoses................ 294 18.10.2 Palliative Treatment of Dysphagia with Stents........................ 295 18.10.3 Percutaneous Gastrostomy................ 295 18.11 Percutaneous Nephrostomy............................. 296 18.12 Respiratory Interventions................................. 296

19. Paediatric Radiology.................................... 297 19.1 Respiratory Tract.................................................. 297 19.1.1 Pulmonary Diseases................................. 297 19.1.2 Mediastinal Diseases................................ 298 19.1.3 Heart Disease............................................ 298 19.2 Gastrointestinal Tract.......................................... 298 19.2.1 Diseases of the Gastrointestinal Tract........................................................... 299 19.3 Urogenital Tract.................................................... 300 19.3.1 Diseases of the Kidneys and the Urinary Tract...................................... 302 19.4 Musculoskeletal System....................................... 304 19.4.1 Diseases of the Skeleton........................... 304 19.5 Neuroradiology..................................................... 306 19.5.1 Diseases of the Brain................................ 307 19.5.2 Diseases of the Spine................................ 308

Index..................................................................... 310

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List of Abbreviations 2D two-dimensional 3D three-dimensional a. artery AA acute abdomen AAA aneurysm of the abdominal aorta AG angiography AP anteroposterior (projection) APTT activated partial thromboplastin time A-V arteriovenous AVM arteriovenous malformation CM contrast media CNS central nervous system comm. communis (common) CRP C-reactive protein CT computed tomography CTA CT angiography d. ductus DSA digital subtraction angiography DWI diffusion-weighted imaging dx. dexter, right ERCP endoscopic retrograde cholangiopancreato­graphy FLAIR fluid-attenuation inversion recovery fMRI functional magnetic resonance FNA fine needle aspiration GIT gastrointestinal tract HU Hounsfield unit inf. inferior INR international normalized ratio IU intravenous urography IV intravenous KTI cardio-thoracic index lat. lateralis m. morbus m. musculus MDCT multidetector CT (more precisely CT with multiple detector rows)

med. medialis MG mammography MIP maximum intensity projection MR magnetic resonance MRA magnetic resonance angiography MRCP magnetic resonance cholangiopancreatography MRI magnetic resonance imaging MRS magnetic resonance spectroscopy mSv milisievert n. nerve PA posteroanterior (projection) PACS picture archiving and communication systems PC phase contrast PET positron emission tomography PNO pneumothorax PNS paranasal sinuses proc. processus (protuberance) PTA percutaneous transluminal angioplasty PTC percutaneous transhepatic cholangiography PTCA percutaneous transluminal coronary angioplasty PTD percutaneous transhepatic drainage (of biliary tract) RFA radiofrequency ablation sin. sinister, left SPECT single-photon emission computed tomography STIR short-tau inversion recovery sup. superior Sv sievert (mSv – milisievert) TIPS transjugular intrahepatic portosystemic shunt TNM tumour, node and metastasis (tumour grading system) TOF time of flight (MRA sequence type) tr. truncus US ultrasonography v. vena

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1.

Introduction Miroslav Heřman

Radiology is a clinical medical discipline based on imaging. Imaging methods are used in diagnostics, as well as for guiding therapeutic procedures.

The objective of this radiology textbook is primarily to teach a student to correctly indicate individual imaging examinations and to know their common indications and contraindications, as well as to learn to assess and report of the common types of examinations needed in clinical disciplines. The path to these goals leads through an understanding of the basic principles of imaging methods.

1.1 Origin and Properties of X-rays X-rays are electromagnetic waves with a very short wavelength of 10–8–10–12 m. In radiodiagnostics, the wavelengths of 10–9–10–11 m are used.

X-ray properties: an X-ray is invisible, it propagates linearly at the speed of light, and in a vacuum it decreases with the square of distance. It passes through an object in which it is partially absorbed and scattered, and the amount of an X-ray absorbed and scattered depends on the composition of the object (its average atomic number, density, and thickness) and the quality of the X-ray (its wavelength). In the object, the X-ray induces the ionization and excitation of atoms. X-rays produce a blackening of the photographic material (the so-called photochemical effect), the origin of visible light in luminophores (the so-called luminescent effect), and the excitation of some substances, which is used in digital radiography. The biological effects of ionizing radiation are significant.

Generation of X-rays: in radiology, the source of X-rays is an X-ray tube (Fig. 1.1). X-rays are generated by the rapid braking of very fast-flying electrons in a mass with a high proton number (e.g. tungsten).

occur if the dose in a tissue or an organ exceeds a certain threshold. An example may be an acute radiation syndrome or local effects on the skin. In radiology, we encounter only stochastic effects, as we use low doses of radiation. The stochastic effects are delayed zero-threshold effects and each dose, even a very small one, corresponds to a certain probability of their occurrence. The most serious effects include the origin of malignant tumours and genetic changes.

The aim of protection against ionizing radiation in radiology is to prevent the occurrence of deterministic effects and to limit the stochastic effects to an acceptable level.

1.3 Principles of Radiation Protection Radiation protection is defined by the International Atomic Energy Agency as the protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this. The reduction of the expected dose and the measurement of a human dose uptake are fundamental to radiation protection.

The International Committee on Radiation Protection (ICRP) recommends, develops and maintains the

X-ray tube

housing

1.2 Biological Effects of X-rays The radiation absorbed in a human body has negative effects, which are conditioned primarily by the excitation and ionization of the mass atoms. At the cellular level, the most significant damage is that done to the DNA molecule. The dividing cells are those most sensitive to X-rays. That is why we particularly consider the indication of X-ray procedures in the pelvis and abdomen and all X-rays in children.

The biological effects of ionizing radiation on the organism are divided into deterministic and stochastic. Deterministic effects are of the threshold type – the effect will only

A

C

W useful X-ray beam

Fig. 1.1 X-ray tube scheme. The X-ray tube is an evacuated glass tube stored in a lead housing. The cathode (C) is heated to emit electrons which are greatly accelerated as a result of the high voltage between the cathode and the anode (A). Accelerated electrons collide with anode material and their kinetic energy changes to heat (99%) and X-rays (1%). A rotating anode is used (rotor – R) for better cooling. The useful radiation beam leaves the X-ray tube by the window (W) in the X-ray tube housing.

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1. Introduction

International System of Radiological Protection, based on the evaluation of the large body of scientific studies available to equate risk to received dose levels. The system’s health objectives are to manage and control exposures to ionizing radiation so that deterministic effects are prevented, and the risks of stochastic effects are reduced to the extent that is reasonably achievable.

The ICRP’s recommendations flow down to national and regional regulators, which have the opportunity to incorporate them into their own law. In most countries a national regulatory authority works towards ensuring a secure radiation environment in society by setting dose limitation requirements that are generally based on the recommendations of the ICRP. The ICRP uses the following overall principles for all controllable exposure situations.

Justification: No unnecessary use of radiation is permitted, which means that the advantages must outweigh the disadvantages.

Limitation: Each individual must be protected against risks that are far too large through individual radiation dose limits.

Optimization: Radiation doses should all be kept as low as reasonably achievable (ALARA). This means that it is not enough to remain below the radiation dose limits, but that radiation doses are as low as reasonably achievable, which often means much lower than the permitted limit.

There are no limits to the medical exposure of patients. This is to be construed as meaning that when the

examination under consideration is reasonably indicated, there is no dose limit that is not to be exceeded.

1.4 Overview of Doses in Radiological Examinations In the last two decades there has been a significant increase in the absolute number of tests using ionizing radiation. As a result, its current use in medicine represents the largest artificial source of ionizing radiation for the population in advanced countries.

For comparison of the doses received in different types of examinations, it is useful to use the effective dose. The effective dose is calculated from the doses absorbed by individual organs and is expressed as a single number. Its unit is the sievert (Sv). It enables an estimate of the risk of stochastic effects (the occurrence of fatal tumours and genetic changes) that can be compared to other risks. For children under 15 years of age, the effective dose of the same examination, i.e. the risk of stochastic effects from radiation exposure, is two to three times higher than for adults.

Table 1.1 lists the values of ​​ the effective dose and the risk of stochastic effects in some examinations. In general, the effective doses of standard radiological examinations differ significantly (0.01–10 mSv), but in most cases they are considerably lower than the effective dose in CT examinations (approximately 2–20 mSv). The average effective doses of interventional procedures using ionizing radiation are usually

Table 1.1 Typical effective doses in adults in connection with some medical procedures and their risks.

Diagnostic procedure (source) average background radiation tooth radiograph (intraoral) limb and joint radiographs (except hip) chest radiograph (PA projection) chest radiograph (PA and lateral projections) skull radiograph abdominal radiograph lumbar spine radiograph intravenous urography barium meal CT of head CT of chest or abdomen angiography of head or neck diagnostic coronarography coronarography + PTA + stent introduction TIPS introduction bone scintigraphy whole body PET/CT

Typical effective dose

Risk of developing fatal tumour*

average of 3 mSv/year 0.005 mSv < 0.01 mSv 0.02 mSv 0.1 mSv 0.1 mSv 0.7 mSv 1.5 mSv 3 mSv 6–8 mSv 2 mSv 7–8 mSv 5 mSv 7 mSv** 15 mSv** 70 mSv** 6 mSv 15 mSv

1: 4,000,000 < 1 : 2,000,000 1 : 1,000,000 1 : 200,000 1 : 200,000 1 : 30,000 1 : 15,000 1 : 7,000 1 : 3,500–2,500 1 : 10,000 1 : 3,000–2,500 1 : 4,000 1 : 3,000 1 : 1,600 1 : 300 1 : 3,500 1 : 1,500

* Fatal tumour = a tumour as a result of which the patient dies. ** Values may vary significantly, depending on the experience of the physician performing the examination and the difficulty of the examination (for example, for TIPS introduction, they vary within the range of 20–180 mSv).

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1.5 Request for Radiological Examination

13

in the range of 5–70 mSv, while in nuclear medicine they are in the range of 0.3–20 mSv. These doses can be compared to the dose we receive from the natural background, which is 3 mSv per year on average (in the range of 1.5–7.5 mSv per year). For a comparison of the risks posed by ionizing radiation with some other common risks, see Table 1.2.

Exposure to ionizing radiation during pregnancy.

Foetal exposure to ionizing radiation may lead to prenatal death, retardation of intrauterine growth, mental retardation, organ malformations, and the development of malignant tumours in a new-born child. The risk of these effects depends on the gestational age at the time of exposure and the size of the dose. In radiological examinations which do not directly irradiate the foetus the dose for the foetus is minimal and the risk of these changes is unlikely. In abdominal and pelvic examinations, some complications may occur. However, if the procedure is necessary and cannot be replaced by another method (e.g. ultrasonography or magnetic resonance), the risk is acceptable. For example, after a radiograph of the abdomen or lumbar spine, the risk of a tumour developing in the child increases from 0.067% to 0.084% and the increase in other risks is even lower. In

Table 1.2 Risk of death resulting from common influences/ activities.

Cause

Risk of death

the risk of carcinoma from food additives pregnancy for mother general anaesthesia travel by jet plane (> 1,000 miles per year) occupational injury traffic accident life in a big city (pollution) smoking 10 cigarettes a day

1 : 1,000,000 1 : 170,000 1 : 50,000 1 : 30,000 1 : 2,000 1 : 500 1 : 160 1:5

examinations with a higher dose in the area of the abdomen, of course, the risk of developing the above complications increases.

1.5 Request for Radiological Examination When requesting a radiological examination, the indicating physician has to fill in a form with two kinds of data: 1) Basic personal data of the patient (to correctly identify the patient), 2) Clinical data – the type and region of ​​examination required, and also the patient’s anamnesis, significant clinical and laboratory findings, and the results of other examinations. For the radiologist, the request form is a primary source of patient data. The most important data is the clinical diagnosis (in relation to the examination required) and the question which is to be answered by the examination. For an examination in which the administration of a contrast medium is anticipated, an allergic anamnesis must also be given on the form.

1.6 Radiological Report The report is a part of the examination. Generally, it consists of three parts: 1) the name of the examination and the technique applied, 2) the description of the examination (“objective” description of what is visible in images), and 3) the impression, where the information from the description of the examination with the clinical data is combined. In shorter descriptions, some or all of the parts are aggregated.

In the description, we use terms that will be discussed with each method. The description should be sufficiently detailed to provide a good idea of the image even if we do not have the images available. The radiologist’s ability to draw a correct impression from the examination is to a large extent conditioned by the accuracy, completeness, and quality of the anamnestic and clinical data on the request form.

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14

2.

Imaging Methods Miroslav Heřman

This chapter discusses the basic principles of imaging methods, their most common indications and contraindications, and the general terms used in the examination report.

2.1 Radiography Radiography is an imaging technique using X-rays to view the internal structure of an object. Radiographs, usually shortened to X-rays, are results of the rays generated in the X-ray tube (Fig. 2.1) which pass through the area being examined, where they are partially absorbed and scattered, depending on the composition of the tissues being examined, and then they are captured by a detector. The original recording material was a photographic film. By developing the film we get the final image. Nowadays, radiographs are made digitally in most cases. The most significant benefits of digital radiography are the higher quality of the images acquired, the reduction of the dose, the possibility of subsequent modification of the image (e.g. highlighting the most important parts of the image, adjusting the brightness, contrast, enlargement, highlighting of the interfaces), and archiving images in digital form.

There are two basic principles of digital imaging: computed radiography and digital radiography.

In computed radiography (CR), the radiation passed through the object is captured on a plate containing a sensitive layer based on photostimulable phosphor. The image

a

is processed in a digitizer (reading device) by scanning the plate with a laser. The amount of light released is registered and the latent image of the phosphor layer is converted into digital form. The phosphor layer is then erased by the laser and is ready for further use. These plates are stored in similar cassettes to X-ray films and maintained in a similar way – after the image is captured, the cassette is inserted into the digitizer and the resulting digital image is displayed on a monitor, where it can be further edited. The entire process from exposure to the display of the image takes 0.5–2 minutes (Fig. 2.1).

Digital radiography (DR) uses different technical principles, but in both systems the conversion of passed X-rays to electrical digital signals occurs directly in the detector of the device. This transfer is faster than in computed radiography and, moreover, there is no need to transport the cassette from the examining room to the digitizer, which significantly accelerates the whole process – the image is available a few seconds after its exposure (Fig. 2.2).

A radiograph is a two-dimensional image of a threedimensional object. It is a summation image – it captures information about all the tissues through which radiation has passed, regardless of the order in which it occurred. Tissues that absorb more radiation produce opaque [shadowed, (hyper)dense] areas, while less absorbent tissues are presented as lucent (hypodense) areas. These terms are relative – they are always related to a normal condition. This terminology is based on traditional radiographs. Because the radiograph

b

Fig. 2.1 Computed radiography process. a) Radiation coming out from the X-ray tube ( ) passes through the object being examined (elbow) and interacts with the sensitive layer of the plate enclosed in the cassette ( ). The phosphor-coated imaging plate interacts with X-rays transmitted through the object to capture a latent image. b) The cassette is then marked with patient data ( ) and inserted into the digitizer ( ). In the digitizer, the film is removed from the cassette and scanned by a laser beam; the amount of energy released is registered at each point of the image and thus the latent image is “converted” to the resulting digital image, which is displayed on the monitor, checked or modified by a radiological technician, and sent to the digital archive.

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2.2 Fluoroscopy

15 Fig. 2.2 Digital radiography process. a) Radiation coming out from the X-ray tube ( ) passes through the object being examined (hand) and interacts with the digital detector ( ) in which the transmitted X-rays at each point of the image are converted to digital electrical impulses. b) The image obtained is displayed on the monitor, where a radiological technician checks or modifies it and sends it to the digital archive.

a

is negative, the areas of lucency are displayed as “darker” and opaque ones as “lighter” (Fig. 2.3). Especially in digital images, it is not a problem to convert the image into a “positive” one (“reverse” white and black shades), but a negative image is used as the basic one.

Radiography is limited to demonstrating five basic densities: air, which is most lucent – appears the blackest in a radiograph; fat, which is shown in a lighter shade of grey than air; soft tissue and fluid, which have intermediate density (soft tissue and fluid have the same density on radiographs); calcium, usually contained within bones or calcifications;

Fig. 2.3 Hypodensity/hyperdensity. In the chest image, a hyperdensity or opacity ( ) is visible on the left side, with a hypodensity (lucency) in it ( ) that is inferiorly contoured by an air-fluid level (a typical appearance of an abscess).

b

metal or contrast agents, which are most opaque (they appear as white) in a radiograph, because they attenuate a large proportion of the X-ray beam.

When radiographs of most areas are being captured, images are taken in two projections, most often anteroposterior and lateral. Two projections are advantageous for several reasons – primarily to provide information about the spatial layout of structures, and to find changes that may not be noticeable in one projection. The term anteroposterior (AP) indicates that the X-ray beam enters through the anterior (front) aspect of the body, and exits out of the posterior (back) aspect, where the beam is detected. This is the way most radiographs are taken. An important exception is chest imaging, where images are taken of standing patients as posteroanterior (PA). In right lateral projection the X-ray beam passes from the left to the right side (i.e. the patient’s right side is closer to the detector).

Traditionally, radiographs were viewed using a viewer, an accessory device that emits homogeneous, reasonably intense light. When orienting radiographs on the viewer, the anteroposterior and posteroanterior images are laid in such a way that it is as if we are looking at the standing patient facing us in a basic anatomical position (exceptions include, for example, radiographs of hands or feet, which are laid with the fingers or toes upward). The left and right sides of the image are indicated by the letters L or R, usually located in a corner of the image. We obey the same guidelines when orienting digital images displayed on a computer monitor.

Indications and contraindications. Radiographs of the skeleton and chest are most frequent. Pregnancy is a relative contraindication for performing all tests using ionizing radiation.

2.2 Fluoroscopy Fluoroscopy enables real-time radiographic visualization of moving structures. A continuous X-ray beam passes through the patient and then is captured by a detector and

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16

2. Imaging Methods

a

b

Fig. 2.4 Fluoroscopic examination room. The X-ray tube ( ), the examination table, and the detector ( ) are connected so that the patient can be examined a) standing or b) lying, or the table can be tilted to the Trendelenburg position (the head is lower than the legs).

A fluoroscopic image can be viewed on a monitor directly in the examination room or outside it.

displayed on a monitor (Fig. 2.4). Fluoroscopic findings are most often documented in radiographs. When compared to radiography, fluoroscopy has a higher radiation dose and lower resolution and contrast, but it allows the imaging of dynamic processes.

Indications and contraindications. Fluoroscopy is used to monitor continuous radiographic procedures such as studies of the gastrointestinal tract, angiography, and interventional procedures; it is also used for intraoperative imaging, most often in skeletal surgery. The contraindications do not differ from those of other methods using X-rays.

2.3 Tomography, Tomosynthesis Tomography (from the Greek tomos – layer, cut) was used to reduce the problem of superimposition (summation) of structures in radiography. By moving the X-ray source and the film in opposite directions during the exposure, it was possible to obtain a sharp image of the selected plane of interest and blur other planes.

Indications and contraindications. The main indications were the imaging of lung or bone changes that were insufficiently delineated on conventional radiographs. This method has been replaced in clinical practice by more advanced techniques, particularly by computed tomography (CT). The contraindications do not differ from those of other radiographic methods.

Tomosynthesis is a new technology combining traditional tomography and CT. With a single motion of the Xray tube by several tens of degrees, the data retrieved on a flat digital detector allows the reconstruction of multiple thin layers (either parallel or multi-plane) or even threedimensional imaging. The dose received during an examination is similar: up to twice as high in comparison with a plain radiograph.

Indications and contraindications. Tomosynthesis is beginning to find clinical applications, especially in mammography and lung and skeletal evaluation. The

contraindications do not differ from those of other methods using X-rays.

2.4 Angiography The term angiography generally refers to the imaging of vessels. Vessels can be viewed either non-invasively, using techniques of Doppler ultrasonography, CT angiography, or MR angiography (these methods will be discussed later), or invasively by angiography. This narrower sense of angiography will be used here. In angiography, a contrast medium (CM) is administered intravascularly, followed by radiographic imaging.

Angiographic examinations are performed at special surgeries equipped with an angiographic system. This system allows the fluoroscopic guidance that is necessary for the guidance of angiographic instruments (catheters, guide wires, etc.), as well as fast radiography. The layout of the X-ray tube and the opposite detector placed on a movable C-arm allows both fluoroscopy and radiography in different projections (Fig. 2.5). The patient lies on a freely movable table, known as a floating plate (which can be locked in the selected position). For CM administration at angiographic examinations, we use a contrast media injector that allows rapid and accurate dosing coordinated with imaging.

Digital subtraction angiography (DSA) is used in most angiographic examinations. Its basic principle is the digitization of the fluoroscopic image and the computer subtraction of images before and after the injection of CM. Subtraction leads to removal of the “background” (especially skeletal) structures visible in the unsubtracted image, and therefore only vessels filled with contrast medium are shown (Fig. 2.6).

The term angiography is used in clinical practice to display arteries, capillaries, and veins in one area (e.g. carotid angiography), as well as for imaging arteries only (e.g. angiography of the lower limbs). The term venography is used to target veins.

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2.5 Ultrasonography (US)

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2.5 Ultrasonography (US)

Fig. 2.5 View from the control room to the angiographic examination room. The patient lies on the examination table, and the physician performing the examination uses the monitors to check the position of the catheter that has been inserted. The detector located above the area being examined and the X-ray tube (now under the table) are attached to the C-arm ( ) and allow different projections to be set up. At the front, we can see the monitors in the control room.

Indications and contraindications. Angiography is primarily used to diagnose vascular diseases, currently most commonly just prior to vascular interventional radiological procedures. Contraindications to angiographic examinations are the same as those of other methods using X-rays, accompanied by contraindications associated with the application of contrast media and haemocoagulation disorders.

a

b

The synonyms for ultrasonography are sonography and ultrasound (and echocardiography for cardiac US).

US is an imaging method utilizing ultrasound reflections from tissue interfaces with different acoustic impedances.

Ultrasound is a wave of a mechanical nature, transmitted as the vibration of particles in a medium. When passing through the mass, the ultrasound is absorbed, scattered, or reflected. In diagnostics, we use reflections that occur at the interface of different media (tissues with different acoustic impedances); the greater the difference in the density of these media, the greater the intensity of the reflection.

For diagnostic purposes, we use frequencies of 2–20 MHz, which are suited to the imaging of soft tissues and fluids.

The interface between a fluid medium (in which we can include soft tissue because of its high water content) and a bone or a gas is so big that it reflects almost all ultrasound waves. Therefore, organs located beneath the skeleton or gas can only be examined in a limited way. For the same reason, it is necessary to use contact gels on the skin – to remove the thin layer of air between the skin and the probe, which would prevent the waves from crossing into the area being examined. An important exception to examinations of structures beneath the skeleton is the transcranial Doppler examination of the major brain arteries. It is performed over a squamous part of the temporal bone that is relatively thin and the ultrasound of higher intensity used in Doppler US passes through it at a sufficient intensity.

The source of ultrasound is a piezoelectric crystal that deforms its shape by the action of alternating current. The opposite principle is used to capture reflections (echoes), with the intensity of the reflection informing us about the

c

d

Fig. 2.6 Principle of digital subtraction (image of the popliteal artery and its branches). a) An unenhanced image is taken before the administration of CM and b) is converted to a negative on the computer. c) The image after the injection of CM (without subtraction). d) If we merge images (b) and (c), structures that have not changed (= skeleton, soft tissues) will be subtracted (and disappear) and only those structures that differ, i.e. arteries filled with contrast medium, will remain. We can view the subtracted image (d) either like this or in the negative or project the skeleton (or part of it) back into the image.

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18

2. Imaging Methods

b

Fig. 2.7 a) Ultrasound machine. b) Probes – different types. On the left, a convex probe with lower frequencies for the examination of deeper structures, e.g. the abdomen. In the middle, a linear probe with higher frequencies for the examination of superficially located structures, e.g. the neck or limb vessels (the image displayed on the machine was obtained by this probe). On the left, a sector probe with a small contact area designed specifically to examine the smallest children.

a

size of the difference in the tissue interface and the time that elapsed from its sending to returning informing us about the distance of the interface from the source.

In most ultrasound applications, the same crystal transmits waves (about 0.5% of its operating time) and receives reflections (99.5% of its operating time). The crystal or, more precisely, crystals are located in a probe, which may be of one of several designs. The most common are sector, linear, and convex probes (Fig. 2.7). The probes also differ in the frequency transmitted: 2–5 MHz frequencies are used to display deeper structures, 5–15 MHz frequencies are used for studying structures closer to the surface (greater spatial resolution but limited penetration). For endosonographic examinations, special probes are used that can be inserted into the organ’s lumen to perform endorectal, transvaginal, endovascular, transoesophageal, or intravascular exa­mination.

The most commonly used type of ultrasound imaging is dynamic B-mode (brightness mode), in which the image is created by capturing a large number of side-by-side reflections, the intensity of whose reflection is associated with a particular degree of grey colour on the monitor. In the description of these images, we use the terms hyperechogenic Fig. 2.8 Examples of structures with different echogenicity. a) In a liver with medium echogenicity, multiple circular anechogenic lesions of different sizes corresponding to cysts are apparent. b) In another patient, an anechogenic gallbladder is shown under the liver, where a strong echo is visible ( ) accompanied by an acoustic shadow ( ). It is a typical image of a stone. c) Another patient – in the posterior part of the liver, a circular hyperechogenic lesion corresponding to the haemangioma is seen.

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a

b

c

2.5 Ultrasonography (US)

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(or hyperechoic) (with higher echogenicity – lighter on the screen – the tissues with more distinct interfaces), isoechogenic (isoechoic) (with the same echogenicity), hypoechogenic (hypoechoic) (with lower echogenicity – darker on the screen – homogeneous tissue with a lower number of lesser interfaces), and anechogenic (anechoic) (without internal echoes – the image is black or dark – fluids) (Fig. 2.8, Table 2.1 Echogenicity of some tissues.

Examples of tissue

anechogenic

fluid (e.g. urine, bile, cysts’ content, blood in vessels)

hypoechogenic

renal parenchyma, lymph nodes, haematoma (usually heterogeneous, often hypo- and hyperechogenic), abscess content, empyema

middle echogenicity

normal liver, spleen, thyroid gland

hyperechogenic

liver with steatosis, fibrosis, or cirrhosis; pancreas in the elderly or obese patients, haematoma

strong echo with an acoustic shadow

bone, calcification, stone, gas (e.g. air in trachea or intestine)

left

right

Echogenicity

Table 2.1). Significantly echogenic lines (strong echo) accompanied by an acoustic shadow in the direction from the probe (an area where no waves spread) indicate the presence of bone, stone, calcification, or gas (Fig. 2.8b). In describing the US finding, the terms hyperechogenic/hypoechogenic most commonly relate to the normal echogenicity of an organ or tissue.

US images can be obtained in different planes. When we are looking at the image, the principle is that, in images in the transverse plane, the left side of a patient is on the right (similar to radiographs), while in images in the sagittal or coronal plane the cranial direction is on the left (Fig. 2.9).

A real-time dynamic image is obtained by means of US, allowing us to choose the most favourable projection plane and also to monitor the movement (e.g. vascular pulsation, heart movement, or organ movement during breathing).

In echocardiography, the M-mode (motion mode), producing a set of curves that record the movement of, for example, heart valves, can be used.

Doppler technique. It uses the Doppler phenomenon – changes in the frequency of waves reflected from a moving object. The speed and direction of motion of the object can be determined from the wave frequency change. The movement of blood cells in blood vessels is most commonly examined in diagnostics. Doppler information can be imaged in colours – colour mapping of moving objects against

b

inferior

superior

a

c Fig. 2.9 Thyroid imaging. a) The position of the probe on the neck to obtain an image in the transverse plane. b) Transverse plane image. The trachea is in the middle of the image and an acoustic shadow can be seen behind it. c) A probe positioned on the neck to obtain an image of the left thyroid lobe in the sagittal plane. d) Image of the left lobe of the thyroid gland in the sagittal plane. The position of the probe in the radiographs (b) and (d) is indicated by a pictogram which is usually located in a corner of the image.

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d

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2. Imaging Methods

a

b

Fig. 2.10 Doppler imaging. a) Colour flow mapping – moving objects in the selected sector of the image are displayed in colour (the image in the sagittal plane displays the inferior part of the liver and the larger part of the right kidney). b) Doppler curve – at the top of the image, the right femoral artery (red) and vein (blue) are shown. The Doppler curve in the lower part of the image was obtained from the artery at the place marked by cursors. The curve shows the time (in seconds) on the x-axis and the speed (in cm/s) on the y-axis. It is a triphasic curve representing a normal finding in the limb arteries.

the background of the image in B-mode (Fig. 2.10a) or as a curve (or more precisely a spectrum of curves) showing velocities over time (Fig. 2.10b).

Colour Doppler images are generally combined with greyscale (B-mode) images to display duplex sonography images, allowing for simultaneous visualization of the anatomy of the area. Blood flow relatively toward the transducer face is usually displayed in shades of red, whereas blood flow relatively away from the transducer face is displayed in shades of blue. The colours indicate the direction of movement towards or from the probe and their shades indicate the speed. In addition to this standard colour mapping technique, we can also use other techniques such as the energy Doppler mode, where very slow flows in small vessels can be registered (albeit without information about flow direction) (Fig. 2.11).

From the Doppler curve, we can read the data on the maximum systolic velocity or the lowest diastolic velocity, as well as calculate different ratios indicating, for example, the resistance in the periphery of the supplied area of the vessel being examined (known as the resistance index – RI).

Fig. 2.11 The energy Doppler showing flows even in small vessels in the periphery of the right kidney (cf. Fig. 2.10a).

Fig. 2.12 Contrast ultrasonography.

Evaluation of the finding after intravenous administration of ultrasonic contrast medium. The curves at the bottom of the image show the character of enhancement in various regions of the left lobe of the liver, in which geographic hyperechogenic regions are visible.

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