Imaging: Varying results for PI-RADS in diagnosing central lesions

Gary J. Faerber, MDThe AUA 2016 imaging take-home messages included abstracts about texture analysis, an imaging algorithm using CT and MRI in the evaluation of fat-poor angiomyolipomas, and contrast-enhanced ultrasound. The take-home messages were presented by Gary J. Faerber, MD, of the University of Utah Health Sciences, Salt Lake City.

The utility of the Prostate Imaging Reporting and Data System (PI-RADS) has been demonstrated for peripheral lesions, but two studies reported varying results using PI-RADS and MRI in diagnosing central lesions. Of 252 lesions identified in one study, 128 had prostate cancer detected. Midline lesions also had higher rates of being intermediate- or high-risk cancers. In the second study, 27 central zone lesions were identified and biopsied despite the fact the central zone lesions were more likely to have higher PI-RADS scores than the peripheral zone or transitional zone lesions. Only two of 27 had significant prostate cancer, and both of these lesions had PI-RADS scores <3.   

Texture analysis, which uses mathematical methods to evaluate the intensity and relationship of pixels on CT with one another, appears to differentiate oncocytomas from clear cell carcinomas. This suggests a noninvasive method of differentiating benign from malignant renal lesions is possible.

A study examining what to do with patients with a negative fusion-guided biopsy identified 45 patients who had an initial negative fusion biopsy but who underwent repeat fusion biopsy due to a rising PSA or atypical small acinar proliferation (ASAP) found on initial fusion biopsy. Ten of the 45 had a positive repeat fusion biopsy; of those, three of 10 had intermediate-risk prostate cancer and only one had high-risk disease. Risk factors associated with a positive repeat biopsy were PSA >10 ng/mL and a mean PSA rise of 3. Higher PI-RADS scores, history of ASAP, or change in PSA density were not associated with a positive re-biopsy.

Pulsed laser and ultrasound multispectral photoacoustic imaging (MPI) was used to identify six of seven oncocytomas and 19 of 22 renal cell carcinomas (RCC), suggesting MPI could be used intraoperatively to assist surgeons in enucleation in the case of oncocytoma versus wider resection in the case of RCC.

An imaging algorithm using CT and MRI in the evaluation of fat-poor angiomyolipomas (AMLs) seems to be very predictive. MRI+CT scores of 0 to 1 demonstrated no AMLs, whereas MRI+CT scores of 4 to 6 captured 93% of all fat-poor AMLs.

Continue to the next page for more take-home messages.

• A ceiling-mounted lead-acryl shield used to protect against radiation during ureteroscopy provided significant forehead protection, but acceptance of the shield was far from universal among surgeons. Judicious use of fluoroscopic imaging remains the best method to reduce radiation exposure during endoscopic procedures.

• A proprietary device fitted to the C-arm that digitally enhances the image during ureteroscopy showed significant reduction in fluoroscopy time and radiation dose, with no negative impact on image quality.

• A 1-hour, in-service training exercise designed to reduce residents’ radiation exposure resulted in a 30% reduction in fluoroscopy times.

• Contrast-enhanced ultrasound (CEUS) may be a less expensive surrogate for MRI imaging in patients post-cryotherapy. In a comparison of standard MRI versus CEUS for follow-up of small renal cell carcinomas treated with cryoablation, there was complete concordance between MRI and CEUS findings. Of two patients with documented recurrence, both MRI and the CEUS demonstrated the recurrence.

• A comparison of CEUS versus standard fluoroscopic antegrade nephrostogram to evaluate ureteral patency following percutaneous nephrolithotomy found perfect concordance to the findings, with 10 of 12 ureters being patent and two of 12 demonstrating ureteral obstruction.

• Preliminary work using ultrasound to determine wall tension, wall stress, and compliance during urodynamic testing in patients with overactive bladder may lead to the development of less invasive methods of measuring bladder function and may supplant the need for standard invasive urodynamic evaluation.

• In a study of real-world use of ultrasound by U.S. urologists (via certification and re-certification logs), the vast majority of practitioners use ultrasound for prostate imaging, but many use it for in-office renal and scrotal diagnostic purposes. This suggests training programs should consider broadening the scope of ultrasound training beyond that of the prostate.

More AUA 2016 take-home messages:

Minimally Invasive Surgery: Study shows huge variance with RALP cost

Basic Science Research: Trimodal therapy shows promise in oligometastatic PCa

Stone Disease: New AUA guide discusses SWL vs. URS

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