Observer Performance in the Detection and Classification of Malignant Hepatic Nodules and Masses with CT Image-Space Denoising and Iterative Reconstruction.

PURPOSE: To determine if lower-dose computed tomographic (CT) scans obtained with adaptive image-based noise reduction (adaptive nonlocal means [ANLM]) or iterative reconstruction (sinogram-affirmed iterative reconstruction [SAFIRE]) result in reduced observer performance in the detection of malignant hepatic nodules and masses compared with routine-dose scans obtained with filtered back projection (FBP). MATERIALS AND METHODS: This study was approved by the institutional review board and was compliant with HIPAA. Informed consent was obtained from patients for the retrospective use of medical records for research purposes. CT projection data from 33 abdominal and 27 liver or pancreas CT examinations were collected (median volume CT dose index, 13.8 and 24.0 mGy, respectively). Hepatic malignancy was defined by progression or regression or with histopathologic findings. Lower-dose data were created by using a validated noise insertion method (10.4 mGy for abdominal CT and 14.6 mGy for liver or pancreas CT) and images reconstructed with FBP, ANLM, and SAFIRE. Four readers evaluated routine-dose FBP images and all lower-dose images, circumscribing liver lesions and selecting diagnosis. The jackknife free-response receiver operating characteristic figure of merit (FOM) was calculated on a per-malignant nodule or per-mass basis. Noninferiority was defined by the lower limit of the 95% confidence interval (CI) of the difference between lower-dose and routine-dose FOMs being less than -0.10. RESULTS: Twenty-nine patients had 62 malignant hepatic nodules and masses. Estimated FOM differences between lower-dose FBP and lower-dose ANLM versus routine-dose FBP were noninferior (difference: -0.041 [95% CI: -0.090, 0.009] and -0.003 [95% CI: -0.052, 0.047], respectively). In patients with dedicated liver scans, lower-dose ANLM images were noninferior (difference: +0.015 [95% CI: -0.077, 0.106]), whereas lower-dose FBP images were not (difference -0.049 [95% CI: -0.140, 0.043]). In 37 patients with SAFIRE reconstructions, the three lower-dose alternatives were found to be noninferior to the routine-dose FBP. CONCLUSION: At moderate levels of dose reduction, lower-dose FBP images without ANLM or SAFIRE were noninferior to routine-dose images for abdominal CT but not for liver or pancreas CT.

Correlation of radiographic renal cell carcinoma tumor volume utilizing computed tomography and magnetic resonance imaging compared with pathological tumor volume.

OBJECTIVE: New evidence suggests that three-dimensional pathological tumor volume (TV) provides additional prognostic information in renal cell carcinoma (RCC) to that provided by tumor size alone. The aim of this study was to assess the correlation between radiographic TV, by computed tomography (CT) and magnetic resonance imaging (MRI), and pathological tumor volume (TV). MATERIAL AND METHODS: Pathological TV from 143 patients treated with surgical removal for unilateral RCC was compared with radiographic TV. Measurements were taken by one central pathologist and one radiologist, who were blinded to each other's findings. The TV for each modality was calculated using the equation for measuring the volume of an ellipsoid: π/6(Length × Width × Height). RESULTS: No statistical differences were noted for relevant clinicopathological covariates between patients who had CT scan or MRI. The correlation coefficient for pathological TV was similar for MRI (0.97) and CT (0.98), although the correlation was lowest for those patients with the smallest tumors (0.82 for pT1a). The TV correlation was weaker among non-obese patients [0.99 for body mass index (BMI) >30 vs 0.89 for BMI <30]. Gender, tumor grade and tumor subtype did not affect TV correlation. Incongruence between radiographic TV and pathological TV is due to overestimation of TV by radiographic imaging. CONCLUSIONS: There was a strong correlation between RCC TV on preoperative images (CT and MRI) compared with pathological TV. This correlation was diminished for patients with smaller tumors. Future investigations are needed to validate this observation and more directly explore the ability of radiographic TV to predict RCC progression and patient outcome.