Pushing Boundaries in Abdominal Imaging

There is still much left to explore in abdominal imaging!

That is the conclusion after attending the scientific sessions at the annual meeting of the Society of Abdominal Radiology (SAR) which was recently held in Scottsdale, Arizona (March 4–9).

One full day was dedicated to presenting the latest research currently being performed in the field of Abdominal Imaging, with a wide variety of topics being covered. LI-RADS, or the uniform reporting of focal liver lesion in suspected cases of hepatocellular carcinoma (HCC), was addressed in several papers. In patients with cirrhosis, specific imaging criteria as outlined in the LI-RADS standard, substitute the need for a tissue diagnosis to establish the diagnosis of hepatocellular carcinoma. However, these criteria were designed specifically to be used in patients with chronic liver disease.

In a presentation entitled “CT of Hepatocellular Carcinoma in Non-alcoholic Fatty Liver Disease: Imaging Characteristics and Inter-rater Agreement” presented by the group from the Mayo Clinic, found that the performance of the imaging criteria, specifically the finding of portovenous phase washout of HCC were not always present in patients with non-alcoholic fatty liver disease (47.6%), and that delayed phase washout remains and important part of the imaging study, with the sign present in 78.6% of tumors in this patient population — a practical point to keep in mind for any practicing radiologist.

Cross sectional imaging has fundamentally changed the way gastroenterologists diagnose, manage and treat patients with inflammatory bowel disease. Active research is being conducted into how best to diagnose and follow-up patients with Crohn’s disease, and how best to detect effectiveness of medical treatment in a timely fashion. Along these lines, the group from Cincinnati Children’s Hospital Medical Center presented their experience with “Inter-radiologist Agreement Using Society of Abdominal Radiology-American Gastroenterological Association (SAR-AGA) Consensus Nomenclature for Reporting CT and MR Enterography in Pediatric Small Bowel Crohn Disease” and found that although there was “fair to moderate agreement” for major imaging criteria in the pediatric population, there was “moderate to substantial agreement” for standardized radiology report impressions. This is an important conclusion as, again, having a standard lexicon for interpretations allows for better communication between radiologists and their referring physicians, allows for longitudinal evaluation of a patient’s imaging findings over time and enables and facilitates outcome-based research. They also concluded that better radiologist education is needed to help further standardize reporting, with such conclusions applicate to the adult population as well.

One of the most surprising presentations was from the group at University of California San Diego and Los Angeles, who concluded that contrast-enhanced ultrasound (CEUS) for the detection of hepatocellular carcinoma actually performed worse than grey scale imaging alone, in those patients undergoing imaging guided therapy. The introduction of contrast to ultrasound imaging in the United States has been viewed as major development in the field, with its added ability to identify and characterize lesions in general, and specifically liver lesions, potentially obviating the need for CT or MRI. The postulated reason for their result could be the greater distance of posterior right liver lobe lesions could be limiting the ability of ultrasound to resolve the finding. As this is sure to create some controversy in the ultrasound world, expect more research and study into the role and effectiveness of contrast in ultrasound exams.

As the SAR combines both gastrointestinal and genitourinary radiology, there were several presentations on the application and reliance of using the “PI-RADS” score. Similar to LI-RADS, PI-RADS score provides a uniform reporting system of prostate MRIs when being evaluated for clinically significant prostate cancer. Normal or benign findings are classified as PI-RADS 1 or 2, concerning lesions being classified as PI-RADS 4 or 5, with the indeterminate group having a PI-RADS score of 3. A presentation entitled “Predictive Role of PI-RADSv2 and ADC Parameters in Differentiating Gleason Pattern 3+4 and 4+3 Prostate Cancer” by the group from Brigham and Women’s Hospital showed that prostate MRI was not able to differentiate these 2 pathologic diagnoses, which could have implications for clinical management.

No radiology scientific presentation in 2018 would be complete with at least one presentation into the realm of machine learning and imaging, and SAR 2018 was no exception. The ability of machine learning to facilitate the interpretation of medical imaging has the potential to be a huge benefit to the practice of radiology presented, and via direct extension, huge benefit to the patients we care for. One such project studying the ability of using open-source Google™ TensorFlow to discriminate between malignant renal cell carcinoma and benign oncocytomas on multi-detector CTs. They found they could reliable identify oncocytomas in 70% of cases and renal cell carcinoma in 100% of cases. Although they converted the DICOM images into JPG images to allow the data to be ingested into the algorithm (a limitation of the software), it does show the potential utility of machine learning as a decision support tool in the characterization of incidental renal lesions.

There were many more facets covered in the scientific component of the meeting, including radiomics, advances in US and utility of MR in disease evaluation. Aside from looking at the content of the presentation, one of the best aspects of the scientific sessions were the number of presenters who were residents or fellows in training, as well as a medical student! Such enthusiasm at an early stage of one’s career will ensure that the future of radiology research will continue, and that the specialty will continue to push the limits of what we know today and open up new avenues that we could not even imagine.

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