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

Abstract

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 jack-knife 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.

Observer Performance with Varying Radiation Dose and Reconstruction Methods for Detection of Hepatic Metastases

“…Projection raw data were collected between October 1, 2012, and July 1, 2014, in patients who underwent contrast-enhanced CT in our department. On the basis of prior work, 83 patients were planned for inclusion in this study; of these patients, approximately half was to have proven hepatic metastases, a quarter was to have proven benign hepatic lesions, and a quarter was to have no hepatic lesions (20). …”

“…Exclusion criteria included a metastasis larger than 5 cm, more than seven metastases, or presence of primary hepatic tumors. Patient examinations were compared against one another to select a cohort of 42 patients who had visually challenging yet proven hepatic metastases (from 517 archived patients with liver metastases) (20). The radiologist tightly circumscribed every liver lesion and documented the reference information relating to its diagnosis.…”

“…Inclusion criteria for benign lesions included typical imaging findings of hemangioma and cyst, as previously described (20), with another cross-sectional examination that demonstrated stability over at least a 6-month interval, or histopathologic confirmation. For patients without lesions, the contrast agent–enhanced CT examination had to have subsequent or previous cross-sectional imaging performed 12 months or longer apart, with both exams interpreted as negative for metastases or benign lesions by two gastrointestinal radiologists.…”

Low kV versus dual-energy virtual monoenergetic CT imaging for proven liver lesions: what are the advantages and trade-offs in conspicuity and image quality? A pilot study

“…Proven malignant lesions occurred in patients with documented primary malignancies that demonstrated progression (enlargement over time) or regression (diminishing size with treatment), or which were diagnosed as malignant based on histopathologic analysis of the resected specimen or biopsy. Criteria for proven benign lesions included stability on CT or MR imaging for at least 6 months, in addition to demonstration of typical imaging features for a cyst (cystic lesion without enhancement or wall) or hemangioma (nodular, peripheral and progressive enhancement isointense with the blood pool) [15]. For each patient, up to three liver proven lesions were used in this study, and the phase of enhancement on which the lesion was the most subtle was chosen for inclusion.…”

Dual-Source Single-Energy Multidetector CT Used to Obtain Multiple Radiation Exposure Levels within the Same Patient: Phantom Development and Clinical Validation

“…By generating data sets at different radiation dose levels (including submillisievert levels) from a single DSSE acquisition within the same patient, the dose-split DSSE technique minimizes the effect of important confounding variables for the assessment of dose reduction strategies, including interpatient or interscan variability. This will enable more simulate reduced-dose CT data sets (21,22). Furthermore, when compared with multiple single-energy CT acquisitions at different radiation dose levels, a variable dose-split DSSE protocol eliminates the need for multiple intravenous contrast material injections and avoids potential variability due to misregistration among different data sets secondary to patient motion or differences in contrast material timing.…”