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Renal Cyst Pseudoenhancement at Multidetector CT: What Are the Effects of Number of Detectors and Peak Tube Voltage?¹

¹ From the Department of Radiology, University of California–San Francisco, 505 Parnassus Ave, Box 0628, C-372C, San Francisco, CA 94143-0628. From the 2007 RSNA Annual Meeting. Received September 7, 2007; revision requested December 12; revision received December 16; final version accepted January 28, 2008. Z.J.W. supported in part by National Institute of Biomedical Imaging and Bioengineering Training Grant 1 T32 EB001631-01A1. Address correspondence to Z.J.W. (e-mail: jane.wang{at}radiology.ucsf.edu).

Purpose: To determine the effect of the number of detectors and peak tube voltage on renal cyst pseudoenhancement in a phantom model.

Materials and Methods: This study on computed tomographic (CT) phantoms did not require institutional review board approval. The renal compartments of a CT phantom were filled with iodinated contrast material diluted to attain attenuations of 40, 140, and 240 HU. Saline-filled cylinders simulating cysts of varying diameters (range, 0.7–3.0 cm) were serially suspended in the renal compartments and scanned at 80, 90, 100, 120, and 140 kVp in 16-detector (n = 3) and 64-detector (n = 2) CT scanners. Generalized estimating equations were used to determine predictors of cyst pseudoenhancement (defined as a >10 HU increase in cyst attenuation when the background renal attenuation increased from 40 to 140 or 240 HU).

Results: Pseudoenhancement was seen with higher frequency (59 [61%] of 96 cysts vs 52 [39%] of 132 cysts, P < .05) and magnitude (17 vs 13 HU, P < .005) with 64- rather than with 16-detector scanners. Pseudoenhancement was also seen with higher frequency (25 [42%] of 60 cysts vs 11 [18%] of 60 cysts, P < .005) and magnitude (18 vs 13 HU, P < .05) at 140 kVp than at 80 or 90 kVp. Cyst pseudoenhancement increased with higher background renal enhancement (P < .005) and smaller cyst diameter (P < .05). The number of detectors, peak tube voltage, renal parenchymal enhancement level, and cyst diameter were independent predictors of cyst pseudoenhancement.

Conclusion: Lower tube voltage settings may be useful when accurate differentiation between small renal cysts and solid masses is critical, particularly for 64-detector CT scanners.

© RSNA, 2008

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