Pseudoenhancement of simulated renal cysts in a phantom using different multidetector CT scanners

We undertook this study to determine whether pseudoenhancement of renal cysts occurs on scans obtained with multidetector CT (MDCT) scanners and whether the effect is influenced by scanning parameters.

A kidney phantom with varying attenuation was created to simulate different levels of renal parenchymal enhancement (150 and 250 H). Two water-filled cylinders simulating renal cysts-one with a 5-mm diameter and one with a 15-mm diameter-were suspended in the "kidney." After validating the pseudoenhancement effect produced in our phantom model with a single-detector helical CT scanner, we investigated the effect with matrix array and adaptive array MDCT scanners using detector configurations of 1.25 and 2.5 mm and beam pitches of 0.75:1.0 and 1.5:1.0 at an effective reconstructed slice thickness of approximately 3 mm. Three sets of experiments were performed at each setting, and mean cyst density was measured. Data were statistically analyzed using the Student's t test and multiple logistic regression analysis when appropriate.

Although pseudoenhancement was observed with MDCT scanners, the effect was statistically significant only for scans depicting the smaller cyst at a background renal density of 250 H on the matrix array MDCT. Modulation of scanning parameters did not alter these findings. Pseudoenhancement was significantly higher with the matrix array MDCT scanner than with the adaptive array MDCT scanner (p < 0.05).

In our phantom model, high levels of renal enhancement produced pseudoenhancement in small renal cysts with different models of MDCT scanners, irrespective of pitch or detector configuration.