Purpose To investigate the relationship between energy level of virtual monoenergetic (VM) imaging and sensitivity in the detection of minimally enhancing renal lesions. Materials and Methods Phantoms simulating unenhanced and contrast material-enhanced renal parenchyma were equipped with inserts containing different concentrations of iodine (range, 0-1.15 mg iodine per milliliter). A total of 180 patients (117 men; mean age, 65.2 years ± 13.0 [standard deviation]) with 194 (62 solid, 132 cystic) renal lesions larger than 10 mm in diameter underwent unenhanced single-energy CT and contrast-enhanced dual-energy CT. VM imaging data sets were created for 70, 80, 90, and 100 keV. Renal lesions were measured, and enhancement was calculated. Area under the receiver operating characteristic curve (AUC) for renal lesion characterization was determined by using the DeLong method. Results The AUC was highest at 70 keV and decreased as energy increased toward 100 keV. AUC in the phantom decreased from 98% (95% confidence interval [CI]: 95, 100) at 70 keV to 88% (95% CI: 79, 96) at 100 keV (P = .004). AUC in patients decreased from 96% (95% CI: 94, 98) at 70 keV to 79% (95% CI: 71, 86) at 100 keV (P = .001). In patients with an enhancement threshold of 15 HU, sensitivity in the detection of solid renal lesions decreased between from 91% (49 of 62 [95% CI: 78, 97]) at 70 keV to 48% (33 of 62 [95% CI: 25, 71]) at 100 keV (P < .05), with no change in specificity (93% [120 of 132 {95% CI: 87, 97}] at 70 keV, 97% [125 of 132 {95% CI: 92, 99}] at 100 keV). Conclusion There is a reduction in diagnostic accuracy for renal lesion characterization with increasing VM imaging energy. The 70-keV setting may provide an optimal trade-off between sensitivity and specificity. © RSNA, 2018 Online supplemental material is available for this article.

Purpose To determine whether single-phase contrast material-enhanced dual-energy material attenuation analysis improves the characterization of small (1-4 cm) renal lesions compared with conventional attenuation measurements by using histopathologic analysis and follow-up imaging as the clinical reference standards. Materials and Methods In this retrospective, HIPAA-compliant, institutional review board-approved study, 136 consecutive patients (95 men and 41 women; mean age, 54 years) with 144 renal lesions (111 benign, 33 malignant) measuring 1-4 cm underwent single-energy unenhanced and contrast-enhanced dual-energy computed tomography (CT) of the abdomen. For each renal lesion, attenuation measurements were obtained; attenuation change of greater than or equal to 15 HU was considered evidence of enhancement. Dual-energy attenuation measurements were also obtained by using iodine-water, water-iodine, calcium-water, and water-calcium material basis pairs. Mean lesion attenuation values and material densities were compared between benign and malignant renal lesions by using the two-sample t test. Diagnostic accuracy of attenuation measurements and dual-energy material densities was assessed and validated by using 10-fold cross-validation to limit the effect of optimistic bias. Results By using cross-validated optimal thresholds at 100% sensitivity, iodine-water material attenuation images significantly improved specificity for differentiating between benign and malignant renal lesions compared with conventional enhancement measurements (93% [103 of 111]; 95% confidence interval: 86%, 97%; vs 81% [90 of 111]; 95% confidence interval: 73%, 88%) (P = .02). Sensitivity with iodine-water and calcium-water material attenuation images was also higher than that with conventional enhancement measurements, although the difference was not statistically significant. Conclusion Contrast-enhanced dual-energy CT with material attenuation analysis improves specificity for characterization of small (1-4 cm) renal lesions compared with conventional attenuation measurements. © RSNA, 2017 Online supplemental material is available for this article.

Purpose To determine the effect of radiation dose and iterative reconstruction (IR) on noise, contrast, resolution, and observer-based detectability of subtle hypoattenuating liver lesions and to estimate the dose reduction potential of the IR algorithm in question. Materials and Methods This prospective, single-center, HIPAA-compliant study was approved by the institutional review board. A dual-source computed tomography (CT) system was used to reconstruct CT projection data from 21 patients into six radiation dose levels (12.5%, 25%, 37.5%, 50%, 75%, and 100%) on the basis of two CT acquisitions. A series of virtual liver lesions (five per patient, 105 total, lesion-to-liver prereconstruction contrast of -15 HU, 12-mm diameter) were inserted into the raw CT projection data and images were reconstructed with filtered back projection (FBP) (B31f kernel) and sinogram-affirmed IR (SAFIRE) (I31f-5 kernel). Image noise (pixel standard deviation), lesion contrast (after reconstruction), lesion boundary sharpness (average normalized gradient at lesion boundary), and contrast-to-noise ratio (CNR) were compared. Next, a two-alternative forced choice perception experiment was performed (16 readers [six radiologists, 10 medical physicists]). A linear mixed-effects statistical model was used to compare detection accuracy between FBP and SAFIRE and to estimate the radiation dose reduction potential of SAFIRE. Results Compared with FBP, SAFIRE reduced noise by a mean of 53% ± 5, lesion contrast by 12% ± 4, and lesion sharpness by 13% ± 10 but increased CNR by 89% ± 19. Detection accuracy was 2% higher on average with SAFIRE than with FBP (P = .03), which translated into an estimated radiation dose reduction potential (±95% confidence interval) of 16% ± 13. Conclusion SAFIRE increases detectability at a given radiation dose (approximately 2% increase in detection accuracy) and allows for imaging at reduced radiation dose (16% ± 13), while maintaining low-contrast detectability of subtle hypoattenuating focal liver lesions. This estimated dose reduction is somewhat smaller than that suggested by past studies. © RSNA, 2017 Online supplemental material is available for this article.

You have accessJournal of UrologyStone Disease: Epidemiology & Evaluation I1 Apr 2017MP01-07 THE ADDED UTILITY OF DIGITAL TOMOSYNTHESIS TO STANDARD ABDOMINAL RADIOGRAPHY FOR IDENTIFICATION OF URINARY CALCULI Daniel Wollin, Rajan Gupta, Brian Young, Eugene Cone, Adam Kaplan, Daniele Marin, Bhavik Patel, Michael Ferrandino, Glenn Preminger, and Michael Lipkin Daniel WollinDaniel Wollin More articles by this author , Rajan GuptaRajan Gupta More articles by this author , Brian YoungBrian Young More articles by this author , Eugene ConeEugene Cone More articles by this author , Adam KaplanAdam Kaplan More articles by this author , Daniele MarinDaniele Marin More articles by this author , Bhavik PatelBhavik Patel More articles by this author , Michael FerrandinoMichael Ferrandino More articles by this author , Glenn PremingerGlenn Preminger More articles by this author , and Michael LipkinMichael Lipkin More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.082AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES The current gold standard for imaging evaluation of urinary stones is non-contrast CT (NCCT), although in recent years the concerns regarding repeated radiation doses has called into question the need for this modality in all cases. For this reason, plain abdominal radiography (KUB) is used by many urologists in a diagnostic and follow-up setting. Digital tomosynthesis (DT) is a novel imaging technique that produces a number of coronal images from a single tomographic sweep, creating high quality images with less radiation than low-dose NCCT. Our aim was to evaluate the added utility of DT to KUB for the identification of urinary stones. METHODS Seven fresh cadavers with an intact genitourinary system and no history of nephrolithiasis were implanted with kidney and ureteral stones of known size and composition using endoscopic methods or a small ureterotomy. After stone implantation was completed, the cadavers were imaged with KUB and DT. Three blinded readers (2 urologists and 1 radiologist with experience in evaluating KUB/KUB-DT for stone disease) evaluated all sets of radiographs. Readers initially evaluated only KUB for the presence and location of calculi and recorded their responses. Readers then were instructed to add in tomogram images to their evaluation and re-record the presence and location of calculi to assess the possible value added by tomograms without changing their initial responses based on KUB only. Reference standard was established by consensus reading with a board-certified urologist and board-certified radiologist with 7 years of experience, neither of which served as a blinded reader on this study. Accuracy of stone detection and assessment of stone location was performed using an exact and nearest neighbor match to account for potential movement of stones after implantation as well as perception differences between readers as to nomenclature of stone location. RESULTS A total of 59 stones were identified in the seven cadavers as part of the gold standard interpretation. Using KUB only with an exact and nearest neighbor match, Reader 1 accurately identified 45.7% (27/59 stones), Reader 2 identified 47.4% (28/59) stones, and Reader 3 identified 35.6% (21/59) stones. Using KUB-DT with an exact and nearest neighbor match, there was a statistically significant improvement in accuracy of stone detection (p <0.01 for all readers) as Reader 1 accurately identified 72.9% (43/59 stones), Reader 2 identified 62.7% (37/59) stones, and Reader 3 identified 66.1% (39/59) stones. Overall this was calculated as a 57% relative increase in stone detection. Of note, the number of false positives (suspected calculi based on reader assessment that were not present on gold standard reading) on KUB and KUB-DT was similar across both reading sessions (11 and 16 respectively, for all readers combined). CONCLUSIONS Addition of digital tomosynthesis to KUB leads to significant improvement in the detection of urinary calculi when compared to KUB alone without a concomitant significant increase in false positives. Further studies will determine the true cost and radiation savings associated with the use of this technology, but it appears to be a promising imaging modality for urinary stones and a possible alternative to NCCT in some settings. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e3-e4 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Daniel Wollin More articles by this author Rajan Gupta More articles by this author Brian Young More articles by this author Eugene Cone More articles by this author Adam Kaplan More articles by this author Daniele Marin More articles by this author Bhavik Patel More articles by this author Michael Ferrandino More articles by this author Glenn Preminger More articles by this author Michael Lipkin More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Purpose: To investigate the impact of a second-generation noise-optimized monoenergetic algorithm on selection of the optimal energy level, image quality, and effect of patient body habitus for dual-energy multidetector computed tomography of the pancreas.Materials and Methods: Fifty-nine patients (38men, 21 women) underwent dual-energy multidetector computed tomography (80/ Sn140 kV) in the pancreatic parenchymal phase. Image data sets, at energy levels ranging from 40 to 80 keV (in 5-keV increments), were reconstructed using first-generation and second-generation noise-optimized monoenergetic algorithm. Noise, pancreatic contrast-to-noise ratio (CNRpancreas), and CNR with a noise constraint (CNRNC) were calculated and compared among the different reconstructed data sets. Qualitative assessment of image quality was performed by 3 readers.Results: For all energy levels below 70 keV, noise was significantly lower (P <= 0.05) and CNRpancreas significantly higher (P < 0.001), with the second-generation monoenergetic algorithm. Furthermore, the second-generation algorithm was less susceptible to variability related to patient body habitus in the selection of the optimal energy level. The maximal CNRpancreas occurred at 40 keV in 98% (58 of 59) of patients with the second-generation monoenergetic algorithm. However, the CNRNC and readers' image quality scores showed that, even with a second-generation monoenergetic algorithm, higher reconstructed energy levels (60-65 keV) represented the optimal energy level.Conclusions: Second-generation noise-optimized monoenergetic algorithm can improve the image quality of lower-energy monoenergetic images of the pancreas, while decreasing the variability related to patient body habitus in selection of the optimal energy level.