Abdomen and Oncology

Key images

Findings

55-year-old male with a renal mass found during a routine abdominal ultrasonography. Evaluation conducted on the dual-energy IQon Spectral CT.

Low monoenergetic images better delineate renal tumors and help enhance the clinician’s ability to detect renal vein thrombosis. By analyzing attenuation curves, it is possible to characterize a thrombus as tumoral.

Axial images and attenuation curves

On the conventional CT images obtained during the nephrographic phase after 60 ml of contrast administration (iodine concentration 350 mg/ml), the borders of a renal tumor were less well delineated compared to the virtual monoenergetic images at 50 keV. Moreover, the low monoenergetic images showed renal vein invasion, which was difficult to see on the conventional CT images. A left nephrectomy was performed, and histological results revealed clear cell carcinoma with invasion of the renal vein.

Discussion

Dedicated post-processing of dual-energy CT data sets provided the opportunity to reconstruct virtual monoenergetic images. The use of low monoenergetic images (40-60 keV), acquired closer to the k-edge of iodine, enhances the clinician’s capability for lesion detection and makes vascular studies possible with lowered contrast material administered. This technique can also be used in the setting of tissue characterization by analyzing attenuation curves of different materials at distinct energy levels.

Contrast-enhanced conventional CT axial image: It is difficult to delineate the borders of the tumor, especially anteriorly, and to depict the renal vein thrombosis (white circle).

Virtual monoenergetic axial image at 50 keV: Better delineates the renal tumor and improves the detection of the thrombus in the vein (white circle).

Attenuation curves: the attenuation curve of the ROI that represents the thrombus in the left renal vein (magenta color) is similar to the ROI that is representative of the tumor (blue color), which suggests a tumoral thrombus.

Macroscopic photograph of nephrectomy specimens shows a solid tumor and signs of venous invasion (white arrows).

Histopathological features characteristic of high grade clear cell carcinoma (HE x 10).

History Benefits or pitfalls of dual-energy CT