Evaluation of Urinary Calculi: A Comparison of CT Values between Spectrum CT and Conventional CT

Objective: To evaluate the difference of spectrum mixed energy(Quality Check) mode and conventional CT for the diagnosing of urinary calculi. Methods: Sixty-three urinary stones were obtained by endoscopic lithotripsy from the urology department of Peking university first hospital. Each calculi underwent the conventional CT scan and spectral imaging technique(Discovery CT750 HD; GE Healthcare) respectively and the scan parameters were consistent strictly. At the GE AW4.4 work station, the CT value of all the images were measured by an experienced radiologist. Paired t test and Pearson correlation analysis were used to compare differences between the two modes. Results: The average CT value of the 63 cases was 886 HU± 428 HU for conventional unenhanced CT mode, and 789 HU± 351 HU for Quality Check mode. The difference of CT value was statistically significant(t=6.90, P < 0.01). The CT value of Quality Check mode was correlated with conventional unenhanced CT mode(r=0.978, R²=0.957; P < 0.01). Conclusion: There is high correction between the two measurement modes, while the CT value of Quality Check mode is lower than that of conventional one. Quality Check mode probably can alternative the conventional CT scans in diagnosing urinary calculi.