A Huge Gastric Angiolipoma Presenting with Acute Upper Gastrointestinal Hemorrhage: A Case Report.

BACKGROUND: Angiolipoma is a benign neoplasm mainly composed of adipose tissue and proliferating blood vessels and is relatively rare in the gastrointestinal tract. And among them, gastric angiolipomas are extremely rare and tend to be small. CASE PRESENTATION: We report the clinical and imaging features of a patient with a huge angiolipoma in the stomach and an episode of hematemesis and melena, caused by the ulceration of the gastric mucosa overlying the gastric subepithelial angiolipoma revealed by the endoscopic evaluation. The patient was anemic, and the anemia resolved after local surgical resection of the tumor. We also reviewed the imaging and histological features of the presenting gastric angiolipoma. CONCLUSION: Radiologists should be aware of this rare benign gastric tumor that may present with gastrointestinal hemorrhage.

Detection of Ureteral Stones in Kidney Ureter Bladder Radiography: Usefulness of Digital Post-processing.

PURPOSE: Kidney, Ureter, and Bladder radiography (KUB) has frequently been used in suspected urolithiasis, but its performance is known to be lower than that of Computed Tomography (CT). This study aimed to investigate the diagnostic performance of digitally KUB in the detection of ureteral stones. MATERIALS AND METHODS: Thirty patients who underwent digital KUB and CT were included in this retrospective study. The original digital KUB underwent post-processing that involved noise estimation, reduction, and whitening in improving the visibility of ureteral stones. Thus, 60 digital original or post-processed KUB images were obtained and ordered randomly for blinded review. After a period, a second review was performed after unblinding stone laterality. The detection rates were evaluated at both initial and second reviews, using CT as a reference standard. The objective (size) and subjective (visibility) parameters of ureteral stones were analyzed. Fisher's exact test was used to compare the detection sensitivity between the original and post-processed KUB data set. Visibility analysis was assessed with a paired t-test. The correlation of stone size between CT and digital KUB data sets was assessed with the Pearson's correlation test. RESULTS: The detection rate was higher for most reviewers once stone laterality was provided and was non-significantly better for the post-processed KUB images (p > 0.05). There was no significant difference in stone size among CT and digital KUB data sets. In all reviews, visibility grade was higher in the post-processed KUB images, irrespective of whether stone laterality was provided. CONCLUSION: Digital post-processing of KUB yielded higher visibility of ureteral stones and could improve stone detection, especially when stone laterality was available. Thus, digitally post-processed KUB can be an excellent modality for detecting ureteral stones and measuring their exact size.

Imaging Features of Extramammary Paget Disease of the Scrotum: A Case Report.

Extramammary Paget disease (EMPD) is a rare intraepithelial malignancy originating in areas rich in apocrine glands, such as the vulva, perineum, perianal area, scrotum, and penis. A few reports of EMPD involving the scrotum have been described in the literature. However, only few reports have described imaging features observed in patients presenting with EMPD. We report EMPD in a patient showing scrotal involvement, focusing on imaging features, particularly those determined ultrasonographically.

Efficacy of Superb Microvascular Imaging for Diagnosing Acute Cholecystitis: Comparison with Conventional Ultrasonography.

We evaluated the diagnostic performance of ultrasonography (US) plus superb microvascular imaging (SMI) compared with conventional US alone for diagnosing acute cholecystitis. We included 54 patients with suspected biliary disease. The SMI pixel count showing flow signal was measured in the region of interest of the gallbladder bed of the liver. Two radiologists independently evaluated imaging features and rated five-point diagnostic likelihood level before versus after the additional SMI using the cutoff SMI pixel count. The SMI pixel count was significantly higher in acute than in non-acute cholecystitis (169.84 vs. 27.48, p < 0.001). The optimal SMI cutoff pixel count for predicting acute cholecystitis obtained by receiver operating characteristic curve was 56.67(82.8% sensitivity, 92.0% specificity). The area under the curve value was significantly higher after the additional SMI than before (0.798-0.863 vs. 0.701-0.736, p < 0.05). US plus SMI could objectively improve diagnostic performance compared with conventional US for acute cholecystitis.

Risk Factors Associated With Incomplete Colonoscopy Based on the Analysis of Computed Tomographic Colonography Findings.

OBJECTIVE: This study aimed to identify the computed tomographic colonography (CTC) findings of incomplete colonoscopy compared with those of complete colonoscopy. METHODS: The clinical data and CTC imaging data from January 2004 to December 2012 were retrospectively obtained at 2 different institutions and reviewed by the central review system. A total of 71 patients who underwent both videocolonoscopy and CTC were included in this study. The CTC findings and clinical data were evaluated for the completeness of colonoscopy. RESULTS: In the CTC analysis, differences in total colon length, abdominal circumference, and sigmoid colon diameter were statistically significant between both groups (P < 0.05). Body mass index (BMI) and height were identified as significant clinical factors influencing the completeness of colonoscopy. In multiple logistic regression tests, only BMI and sigmoid colon diameter were independent factors (P < 0.05). CONCLUSIONS: High BMI larger diameter of sigmoid colon was associated with incomplete colonoscopy based on CTC.

Classification of spontaneous isolated superior mesenteric artery dissection: correlation with multi-detector CT features and clinical presentation.

PURPOSE: The purpose of the study is to propose a computed tomography (CT) classification of spontaneous isolated superior mesenteric artery dissection (SISMAD) correlated with clinical presentation METHODS: We retrospectively reviewed CT images of 40 patients with SISMAD at our institution from 2006 to 2015 and proposed a new classification: type I, patent false lumen with both entry and re-entry; type II, patent false lumen without re-entry; type III, completely or partially thrombosed false lumen; and type IV, thrombosed false lumen with ulcer-like projection. Additionally, we included a subtype (S) at each type when there was either a long segment of dissection and/or significant true lumen stenosis. CT features were statistically analyzed using Fisher's exact and Mann-Whitney test. RESULTS: The CT findings classified patients as type I (15%), type II (12.5%), type III (35%), and type IV (37.5%). Of the 40 patients, 25 (62.5%) were symptomatic. There was a significantly different proportion of each type between symptomatic and asymptomatic patients (p = 0.005). There were 25 patients with subtype (S); no type I or II, 12 type III, and 13 type IV. The symptomatic patients showed longer dissection tendency and more severe true lumen stenosis (78% vs. 53%, p = 0.000) compared with asymptomatic patients. CONCLUSION: The proposed multi-detector CT classification of SISMAD correlates with clinical presentation. This new classification could be helpful for treatment planning.

Distinguishing benign from malignant thyroid nodules using thyroid ultrasonography: utility of adding superb microvascular imaging and elastography.

OBJECTIVE: Thyroid nodules are common; however, malignancy is less than 7%. Therefore, additional techniques such as Doppler ultrasonography or elastography are used to improve diagnostic performance of conventional ultrasonography. We want to prospectively investigate the use of additional superb microvascular imaging (SMI) and strain elastography to B-mode ultrasound in thyroid nodules in distinguishing benign from malignant thyroid nodules. METHODS: We analyzed 52 thyroid nodules (malignant = 26, benign = 26) and reviewers scored the likelihood of malignancy for three data sets (i.e., B-mode ultrasonography alone, B-mode ultrasonography + SMI, and B-mode ultrasonography + strain elastography). The area under the receiver-operating characteristic curve (Az) values, sensitivities, and specificities were compared. RESULTS: A comparison of the data sets revealed that area under the receiver-operating characteristic curve values were similar without statistical difference. However, on comparing sensitivity and specificity based on the management decision of whether to conduct fine-needle aspiration (FNA) after combining information from all three types of imaging (B-mode ultrasonography + SMI + strain elastography), specificity was significantly higher for the combined technique (34.6%) than for B-mode ultrasonography alone (11.5%), without decrease in sensitivity (P = 0.032). CONCLUSION: Additional use of SMI and strain elastography could potentially lead to increase in specificity in thyroid ultrasonography.

Comparison and Combination of Strain and Shear Wave Elastography of Breast Masses for Differentiation of Benign and Malignant Lesions by Quantitative Assessment: Preliminary Study.

OBJECTIVES: To compare the diagnostic performance of strain and shear wave elastography of breast masses for quantitative assessment in differentiating benign and malignant lesions and to evaluate the diagnostic accuracy of combined strain and shear wave elastography. METHODS: Between January and February 2016, 37 women with 45 breast masses underwent both strain and shear wave ultrasound (US) elastographic examinations. The American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) final assessment on B-mode US imaging was assessed. We calculated strain ratios for strain elastography and the mean elasticity value and elasticity ratio of the lesion to fat for shear wave elastography. Diagnostic performances were compared by using the area under the receiver operating characteristic curve (AUC). RESULTS: The 37 women had a mean age of 47.4 years (range, 20-79 years). Of the 45 lesions, 20 were malignant, and 25 were benign. The AUCs for elasticity values on strain and shear wave elastography showed no significant differences (strain ratio, 0.929; mean elasticity, 0.898; and elasticity ratio, 0.868; P > .05). After selectively downgrading BI-RADS category 4a lesions based on strain and shear wave elastographic cutoffs, the AUCs for the combined sets of B-mode US and elastography were improved (B-mode + strain, 0.940; B-mode + shear wave; 0.964; and B-mode, 0.724; P < .001). Combined strain and shear wave elastography showed significantly higher diagnostic accuracy than each individual elastographic modality (P = .031). CONCLUSIONS: These preliminary results showed that strain and shear wave elastography had similar diagnostic performance. The addition of strain and shear wave elastography to B-mode US improved diagnostic performance. The combination of strain and shear wave elastography results in a higher diagnostic yield than each individual elastographic modality.

Radiologic Findings in Extrapancreatic Solid Pseudopapillary Tumor with Aggressive Behavior: a Case Report.

Solid pseudopapillary tumor (SPT) is a low grade malignant tumor in the pancreas, and extrapancreatic SPT is extremely rare. We report a case of a 61-year-old woman who complained abdominal pain with diffuse tenderness. She was diagnosed with extrapancreatic SPT with extensive peritoneal dissemination and hepatic metastases. Although a few cases have reported imaging findings of extrapancreatic SPT, there have been no reports of extrapancreatic SPT with aggressive tumor behavior and dismal prognosis. Although imaging features closely resembled those of classical pancreatic SPTs, malignant transformation of extrapancreatic SPT should be considered when focal discontinuity of the tumor capsule with ill-defined margin and invasion of adjacent structures were identified.

How to Differentiate Borderline Hepatic Nodules in Hepatocarcinogenesis: Emphasis on Imaging Diagnosis.

BACKGROUND: Rapid advances in liver imaging have improved the evaluation of hepatocarcinogenesis and early diagnosis and treatment of hepatocellular carcinoma (HCC). In this situation, detection of early-stage HCC in its development is important for the improvement of patient survival and optimal treatment strategies. Because early HCCs are considered precursors of progressed HCC, precise differentiation between a dysplastic nodule (DN), especially a high-grade DN, and early HCC is important. In clinical practice, these nodules are frequently called "borderline hepatic nodules." SUMMARY: This article discusses radiological and pathological characteristics of these borderline hepatic nodules and offers an understanding of multistep hepatocarcinogenesis by focusing on the descriptions of the imaging changes in the progression of DN and early HCC. Detection and accurate diagnosis of borderline hepatic nodules are still a challenge with contrast enhanced ultrasonography, CT, and MRI with extracellular contrast agents. However, gadoxetic acid-enhanced MRI may be useful for improving the diagnosis of these borderline nodules. KEY MESSAGES: Since there is a net effect of incomplete neoangiogenesis and decreased portal venous flow in the early stage of hepatocarcinogenesis, borderline hepatic nodules commonly show iso- or hypovascularity. Therefore, precise differentiation of these nodules remains a challenging issue. In MRI using hepatobiliary contrast agents, signal intensity of HCCs on hepatobiliary phase (HBP) is regarded as a potential imaging biomarker. Borderline hepatic nodules are seen as nonhypervascular and hypointense nodules on the HBP, which is important for predicting tumor behavior and determining appropriate therapeutic strategies.

Shear Wave Liver Elastography with a Propagation Map: Diagnostic Performance and Inter-Observer Correlation for Hepatic Fibrosis in Chronic Hepatitis.

The aim of this study was to determine the performance of shear wave elastography (SWE) with a propagation map in the diagnosis of hepatic fibrosis, and to assess its reliability with transient elastography (TE) as the reference standard. Our prospective study included 115 consecutive patients with suspected or alleged chronic hepatitis. Patients underwent SWE by two different operators and TE by sonographers on the same day. The correlation coefficient of the intra-class correlation test between an experienced radiologist and a third-year radiology resident was 0.878. There was a moderate correlation between SWE and TE (r = 0.511) in the diagnosis of hepatic fibrosis. The best cutoff values predicting significant hepatic fibrosis and liver cirrhosis by SWE were >1.78 m/s (area under the receiver operating characteristic curve [AUROC] = 0.777) and >2.24 m/s (AUROC = 0.935), respectively. SWE with a propagation map is a reliable method for predicting hepatic fibrosis regardless of operator experience.

Unenhanced computed tomography for normal appendix detection: comparison of low-dose with statistical iterative reconstruction and regular-dose with filtered back projection.

PURPOSE: To evaluate the differences in visualization of a normal appendix between regular-dose (RD) and low-dose (LD) unenhanced CT. MATERIAL AND METHODS: 179 patients underwent both RDCT and LDCT for urolithiasis. Two reviewers evaluated the appendiceal visualization on a three-point scale. Sensitivities and interobserver agreement were measured. RESULTS: There were no significant differences between RDCT and LDCT in sensitivity, regardless of the reviewer. Interobserver agreement was excellent in both RDCT and LDCT. CONCLUSION: Unenhanced LDCT is a good tool for detecting a normal appendix and is also useful for less experienced interpreters who are unfamiliar with using LDCT images.

Adenofibroma in the Uterine Cervix Manifesting as Multilocular Cystic Lesions.

Uterine cervical adenofibroma, a very rare benign neoplasm, has rarely been reported in imaging features in the English literature. Herein, we describe a case of uterine cervical adenofibroma that was depicted as a multilocular cystic lesion with enhanced solid portions.

Diagnostic performance of stomach CT compared with endoscopic ultrasonography in diagnosing gastric subepithelial tumors.

PURPOSE: To evaluate the diagnostic ability of multi-detector computed tomography (MDCT) compared to endoscopic ultrasonography (EUS) as a standard reference, and investigate the factors influencing the detection of small gastric subepithelial tumors (SETs) (<5 cm) on MDCT with stomach protocol. METHODS: We retrospectively investigated 70 patients who were suspected with gastric SETs on esophagogastroduodenoscopy (EGD), and underwent both EUS and computed tomographic (CT) scanning. EUS was performed by two gastroenterologists, and location, size, echotexture, echogenicity, and layer of origin were described when gastric SETs were detected on EUS. MDCTs were reviewed based on consensus of two radiologists blinded to the EUS result. Size, location, enhancement pattern, and contour of the lesion detected on CT were described. We calculated the diagnostic ability of CT compared to EUS with respect to detection of gastric SETs, and investigated the factors influencing detection of SETs on CT. We also used receiver operating characteristic (ROC) curve to obtain optimal cut-off size for predicting CT visibility of small SETs. RESULTS: Of the 70 patients, who underwent both CT and EUS due to suspicious presence of SET on EGD, EUS detected 56 probable cases of SET and 14 cases of external compression. CT led to detection of 39 cases of SET out of the 56 cases. Sensitivity and specificity of CT was 69.6% and 100.0%, respectively. Positive predictive value (PPV) and negative predictive value (NPV) of CT were 100.0% and 45.2%, respectively. There was a significant difference in mean size of CT-detected lesions compared to CT-invisible lesions (14.36 mm vs. 8.52 mm, p < 0.001), but no significant differences in terms of layer of origin and location between these two groups (p > 0.5) were observed. The ROC analysis revealed that the optimal cut-off value, also referred to prediction of CT visibility, was 10 mm. Out of 70 cases, 26 cases (37.14%) were identified as external compression or insignificant lesions such as lipoma, hemangioma, lymphangioma, or gastritis cystica on CT, and do not require regular follow-up. CONCLUSIONS: Stomach CT shows good feasibility with respect to depiction of small SETs, especially in cases where size is larger than 10 mm. Henceforth, it is proposed that stomach CT would be a complimentary or problem-solving tool for SET in evaluating the presence of external compression and characterization of tumors.

Comparison of Knowledge-based Iterative Model Reconstruction and Hybrid Reconstruction Techniques for Liver CT Evaluation of Hypervascular Hepatocellular Carcinoma.

OBJECTIVE: The purpose of this work was to evaluate the image quality, lesion conspicuity, and dose reduction provided by knowledge-based iterative model reconstruction (IMR) in computed tomography (CT) of the liver compared with hybrid iterative reconstruction (IR) and filtered back projection (FBP) in patients with hepatocellular carcinoma (HCC). METHODS: Fifty-six patients with 61 HCCs who underwent multiphasic reduced-dose CT (RDCT; n = 33) or standard-dose CT (SDCT; n = 28) were retrospectively evaluated. Reconstructed images with FBP, hybrid IR (iDose), IMR were evaluated for image quality using CT attenuation and image noise. Objective and subjective image quality of RDCT and SDCT sets were independently assessed by 2 observers in a blinded manner. RESULTS: Image quality and lesion conspicuity were better with IMR for both RDCT and SDCT than either FBP or IR (P < 0.001). Contrast-to-noise ratio of HCCs in IMR-RDCT was significantly higher on delayed phase (DP) (P < 0.001), and comparable on arterial phase, than with IR-SDCT (P = 0.501). Iterative model reconstruction RDCT was significantly superior to FBP-SDCT (P < 0.001). Compared with IR-SDCT, IMR-RDCT was comparable in image sharpness and tumor conspicuity on arterial phase, and superior in image quality, noise, and lesion conspicuity on DP. With the use of IMR, a 27% reduction of effective dose was achieved with RDCT (12.7 ± 0.6 mSv) compared with SDCT (17.4 ± 1.1 mSv) without loss of image quality (P < 0.001). CONCLUSIONS: Iterative model reconstruction provides better image quality and tumor conspicuity than FBP and IR with considerable noise reduction. In addition, more than comparable results were achieved with IMR-RDCT to IR-SDCT for the evaluation of HCCs.

Imaging features of left ovarian and renal venous aneurysms: two case reports and literature review.

Venous aneurysms rarely occur in the visceral veins. We report two extremely rare cases of venous aneurysms, one of the ovarian vein and the other one of the renal vein. The aneurysms were depicted on grayscale and color Doppler ultrasonography as anechoic saccular structures with compressibility and blood flow. Pulsed Doppler ultrasonography showed venous flow. Contrast-enhanced computed tomography showed aneurysmal venous dilatation. We diagnosed left ovarian and renal venous aneurysms. We also review the clinical presentation and implications of visceral venous aneurysms.

Knowledge-based iterative model reconstruction (IMR) algorithm in ultralow-dose CT for evaluation of urolithiasis: evaluation of radiation dose reduction, image quality, and diagnostic performance.

PURPOSE: To evaluate the efficacy of a knowledge-based iterative model reconstruction (IMR) algorithm for reducing image noise in ultralow-dose (ULD) CT for urolithiasis. MATERIALS AND METHODS: A total of 103 patients diagnosed with urinary stones (n = 276) were enrolled. Regular dose (RD) scans (120 kV and 150 mAs, maximal tube current in dose modulation) were reconstructed using filtered back-projection (FBP, RD-FBP), and ULD scans (100 kV and 20 mAs, fixed tube current) were reconstructed with FBP (ULD-FBP), statistical iterative reconstruction (IR; ULD-iDose), and a knowledge-based IMR algorithm (ULD-IMR). Prospective interpretations of the two scans were performed with respect to radiation dose, objective image noise, and subjective assessment. The subjective assessment was also evaluated with regard to each patient's body mass index (BMI, < 25 or ≥ 25 kg/m(2)). Using RD CT (RD-FBP) as the reference standard, two reviewers assessed the diagnostic performance and inter-observer agreement for ULD-IMR. RESULT: The average effective doses with RD CT and ULD CT were 8.31 and 0.68 mSv, respectively, and the average radiation dose reduction rate was 91.82% (p < 0.01). The lowest objective image noise was observed with ULD-IMR (p < 0.01). Subjective assessment in ULD-IMR was comparable to that of RD-FBP, although RD-FBP remained statistically superior. For BMI, there was a statistically significant difference in subjective image quality between the normal (4.7 ± 0.54) and overweight or obese groups (4.2 ± 0.5) (p < 0.05). The ULD-IMR showed a greater than 75% concordant rate in overall stones and 100% in ureter stones larger than 3 mm. However, for stones <3 mm, neither reviewer had a good detection rate (45.5% and 56.9% for the general and genitourinary radiologist, respectively). Inter-observer agreement was almost perfect (κ = 0.82). CONCLUSION: Despite a significant radiation dose reduction, ULD-IMR images were comparable in image quality and noise to RD-FBP images. Furthermore, the diagnostic performance of the ULD non-enhanced CT protocol was comparable to that of the RD scan for diagnosing urinary stones larger than 3 mm.

Differentiation of small arterial enhancing hepatocellular carcinoma from non-tumorous arterioportal shunt with an emphasis on the precontrast CT scan.

PURPOSE: To evaluate the value of precontrast phase (PP) of quadriphasic CT for differentiation of small arterial enhancing hepatocellular carcinoma (HCC) from non-tumorous arterioportal (AP) shunt in patients with chronic liver disease. METHODS: Forty-eight patients with 28 HCCs and 28 AP shunts were enrolled. All lesions (5-20 mm) showed arterial hyperenhancement with isoattenuation on portal venous phase or delayed phase without typical features of AP shunt. We evaluated and analyzed the attenuation of the lesions with qualitative and quantitative methods in each phase. The size, location, shape, margin, and coexistent HCC were evaluated. Diagnostic performances were also compared with triphasic CT and quadriphasic CT including PP in prediction of AP shunts from HCCs. RESULTS: The round or oval shape and visually low attenuation on PP were independent predictors for differentiating HCCs from AP shunts in multivariate analysis. Our study also revealed significantly increased diagnostic performances for both observers when PP was added to the triphasic CT. CONCLUSIONS: PP can be helpful in differentiation of small arterial enhancing HCCs from AP shunts. Careful evaluation of PP may lower need for follow-up CT or MRI, and can possibly achieve earlier diagnosis of small HCCs.

CT for evaluation of urolithiasis: image quality of ultralow-dose (Sub mSv) CT with knowledge-based iterative reconstruction and diagnostic performance of low-dose CT with statistical iterative reconstruction.

PURPOSE: To compare radiation dose and image quality in regular, low, and ultralow-dose CT protocols, and to evaluate diagnostic performance of low-dose CT for urolithiasis. MATERIALS AND METHODS: Sixty-five patients with suspected urolithiasis underwent three different scans under the regular, low, and ultralow-dose protocols. The regular dose scans were reconstructed using filtered back projection and the low-dose scans were reconstructed using a statistical iterative reconstruction. The ultralow-dose scans were reconstructed using both techniques in addition to a knowledge-based IR. Effective radiation doses were compared. Objective image noise was assessed by measuring standard deviation of HU and subjective image assessment was performed with a 3- or 5-point scale. Diagnostic performance of the low-dose image was evaluated, using the regular dose image as a standard reference and the interobserver agreement between two reviewers with different levels of experience was calculated. RESULTS: The effective radiation dose was significantly different in each protocol (p < 0.001) and estimated dose reduction of the low-dose and ultralow-dose protocols was 76.4% and 89.8%, respectively. The knowledge-based iterative reconstruction algorithm showed poorer subjective image quality than the regular and low-dose protocols, but it also had the least objective image noise. Overall, the low-dose image set showed a greater than 84% concordance rate and 100% in ureter stones larger than 3 mm. Interobserver agreement was substantial (kappa value = 0.61). CONCLUSIONS: The knowledge-based IR can provide a better quality image while reducing radiation exposure under the same protocol. Furthermore, the diagnostic performance of the low-dose CT protocol is comparable to the regular dose scan.

Usefulness of low-dose nonenhanced computed tomography with iterative reconstruction for evaluation of urolithiasis: diagnostic performance and agreement between the urologist and the radiologist.

OBJECTIVE: To evaluate the efficacy of low-dose nonenhanced computed tomography (LDCT) with iterative reconstruction (IR) technique for urologists to detect urolithiasis by comparing diagnostic performance and interobserver agreement between the urologist and the uroradiologist. PATIENTS AND METHODS: We evaluated the 116 patients with urinary stones (n = 197) using both conventional-dose nonenhanced computed tomography (CT) using filtered back projection (CDCT-FBP) and LDCT-IR. Scans were interpreted for stone characteristics, objective image noise, and subjective image assessment. Diagnostic performance and interobserver agreement of LDCT-IR were assessed between 1 urologist and 1 radiologist. RESULTS: There were no significant differences in all stones. The average effective dose (mSV) in the all size groups was 5.92 (CDCT-FBP) and 1.39 (LDCT-IR), respectively (P <.001). The average effective dose reduction rate was 76.6%, allowing minimal additional radiation exposure from simultaneous CT. Objective image noise was higher in LDCT-IR (20.0-26.2; P <.01), but there was no significant difference in the Hounsfield unit between both CT protocols (52.3 and 56.7; P = .103). There were no cases of any unacceptable images in subjective image assessment. The sensitivity and specificity of LDCT-IR were 99.1%-100.0% with a diagnostic accuracy of 99.1%-100% for stones ≥3 mm. Diagnostic performance was similar between the urologist and the radiologist. Interobserver agreement of LDCT-IR between the 2 reviewers was high with kappa values (0.901-1.000). CONCLUSION: LDCT-IR provided an excellent diagnostic performance and interobserver agreement between the urologist and the uroradiologist, reducing radiation exposure significantly; in real settings, the urologist should consider replacing LDCT-IR as the standard examination for detecting urolithiasis.