RSNA: MRI most oft used after ultrasound abdomen

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CHICAGO--The rates for further imaging with MRI have increased significantly following a primary ultrasound abdomen study that is equivocal, while those for CT, biopsy and radiography have substantially fallen, according to clinical findings presented Nov. 30 at the Radiological Society of North America (RSNA).

“The expanded applications for various modalities have resulted in a general increase an imaging; however, a substantial fraction results from the over utilization of imaging,” said study presenter Supriya Gupta, MBBS, MD, from Massachusetts General Hospital in Boston.

She and colleagues sought to evaluate the trends in recommendations rate for recommending high-cost versus low-cost modality exams from ultrasound abdomen using a natural language processing (NLP) program (Leximer) to classify unstructured abdominal radiology reports into those with recommendations (R+) and those without recommendations (R-).

The researchers took all R+ abdominal ultrasound reports which were then analyzed from 1993 till 2009 and the rate and type of recommended modality (ROR) was noted for each of them. The values were adjusted for the growth rate of overall imaging exams for the same time period and statistical significance was measured using student t-test.

Out of the 1,011,052 ultrasound abdomen exams from 1993 till 2010, recommendations were made in 20.07 percent cases. Out of those recommendations, ultrasound was recommended in 14 percent, followed by biopsy (11.12 percent), followed by MRI (7.9 percent) and CT (5.83 percent), whereas others were repeat current exam (12.36 percent), endoscopy (0.18 percent), PET (0.02 percent) and x-ray (0.87 percent).

Gupta reported that the ROR for MRI has increased from 4.55 percent in 1993 to 10.11 percent in 2009, but for the same time period, ROR for CT decreased from 16.36 percent in 1993 to 3.75 percent in 2009, for biopsy decreased from 11.1 percent in 1993 to 5.8 percent in 2009 and for radiography decreased from 2.07 percent to 0.65 percent. The ROR for ultrasound, however, remained almost the same—14.2 percent in 1993 to 12.62 percent in 2009.

The increase in recommendation for further MRI following ultrasound of the abdomen may reflect the greater likelihood of higher test specificity for MRI as compared with CT, Gupta concluded.

She added that while this study highlights “current practice trends, it also highlights the inconsistencies of recommendations among various radiologists in the same institution.”