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Renal masses: quantitative assessment of enhancement with dynamic MR imaging
Vincent B Ho1, Scott F Allen, Maureen N Hood
1MR Research Division, Department of Radiology and Radiological Sciences, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd, Bethesda, MD 20814-4799, USA. vho@usuhs.mil
Purpose:
To establish a quantitative magnetic resonance (MR) imaging contrast enhancement criterion for distinguishing cysts from solid renal lesions.
Materials And Methods:
Regions of interest were measured in 74 patients with renal lesions evaluated by means of dynamic contrast material-enhanced MR imaging with serial breath-hold spoiled gradient-echo acquisitions. Sensitivity for renal tumors and specificity for renal cysts were established by using percentage of enhancement thresholds that varied between 5% and 35%.
Results:
The mean percentage of enhancement at MR imaging for the 50 renal cysts was less than 5%; for the 50 renal tumors, it was 97% or higher. With use of a threshold percentage of enhancement of 15% and results obtained between 2 and 4 minutes after administration of contrast material, all malignancies (sensitivity for tumor, 100%) were diagnosed, and there were 6% or fewer false-positive tumor diagnoses. Lower thresholds resulted in unacceptably high false-positive rates (ie, cysts that appeared to enhance-pseudoenhancement), whereas higher threshold values (>20%) resulted in an unacceptably lower sensitivity for tumors.
Conclusion:
The optimal percentage of enhancement threshold for distinguishing cysts from malignancies with the imaging technique prescribed was 15%, and the optimal timing for measurement was 2-4 minutes after administration of contrast material.