Dose Optimization Using a Deep Learning Tool in Various CT Protocols for Urolithiasis: A Physical Human Phantom Study.

Background and Objectives: We attempted to determine the optimal radiation dose to maintain image quality using a deep learning application in a physical human phantom. Materials and Methods: Three 5 × 5 × 5 mm3 uric acid stones were placed in a physical human phantom in various locations. Three tube voltages (120, 100, and 80 kV) and four current-time products (100, 70, 30, and 15 mAs) were implemented in 12 scans. Each scan was reconstructed with filtered back projection (FBP), statistical iterative reconstruction (IR, iDose), and knowledge-based iterative model reconstruction (IMR). By applying deep learning to each image, we took 12 more scans. Objective image assessments were calculated using the standard deviation of the Hounsfield unit (HU). Subjective image assessments were performed by one radiologist and one urologist. Two radiologists assessed the subjective assessment and found the stone under the absence of information. We used this data to calculate the diagnostic accuracy. Results: Objective image noise was decreased after applying a deep learning tool in all images of FBP, iDose, and IMR. There was no statistical difference between iDose and deep learning-applied FBP images (10.1 ± 11.9, 9.5 ± 18.5 HU, p = 0.583, respectively). At a 100 kV-30 mAs setting, deep learning-applied FBP obtained a similar objective noise in approximately one third of the radiation doses compared to FBP. In radiation doses with settings lower than 100 kV-30 mAs, the subject image assessment (image quality, confidence level, and noise) showed deteriorated scores. Diagnostic accuracy was increased when the deep learning setting was lower than 100 kV-30 mAs, except for at 80 kV-15 mAs. Conclusions: At the setting of 100 kV-30 mAs or higher, deep learning-applied FBP did not differ in image quality compared to IR. At the setting of 100 kV-30 mAs, the radiation dose can decrease by about one third while maintaining objective noise.

MRI features of symptomatic amputation neuromas.

OBJECTIVES: To demonstrate the magnetic resonance imaging (MRI) features of amputation neuromas in lower extremity amputees and investigate independent predictive MRI features for symptomatic neuromas. METHODS: This retrospective study included 45 amputation neuromas in 44 lower extremity amputees. Two radiologists assessed the imaging features, including shape, size, type (end-bulb or spindle), signal intensity (SI), heterogeneity, margins, enlarged fascicles, dark outer rim, tail sign, target sign, enhancement, perilesional fibrosis, and muscle denervation. The neuromas were categorized into symptomatic (n = 24) or asymptomatic (n = 21). Symptomatic neuromas were determined based on neuropathic pain characteristics, the presence of Tinel's sign or tenderness, and response to local anesthetic injection. Univariate and multivariate analyses were performed to identify independent predictive MRI features. RESULTS: Of 45 neuromas, 80% (36/45) were end-bulb neuromas and 20% (9/45) were spindle-type neuromas. Eighty percent of the neuromas (36/45) were heterogeneous on T2-weighted images (WIs). Enlarged fascicles were present in 42% (19/45) and dark outer rims in 27% (12/45) of the neuromas. Among the 23 neuromas with enhanced images, 78% (18/23) showed enhancement. Heterogeneity on T2-WIs and enhancement ratios were significantly different between the asymptomatic and symptomatic neuroma groups (p < 0.05). The multivariate analyses indicated that heterogeneity on T2-WIs was an independent factor associated with symptomatic neuromas (p < 0.001). CONCLUSIONS: Heterogeneity on T2-WIs could be a predictive indicator for symptomatic neuromas in lower extremity amputees. KEY POINTS: • Amputation neuromas are classified as either end-bulb or spindle-type. They can show enlarged fascicles, dark outer rims, and enhancement. • Heterogeneity on T2-weighted images could be a predictive indicator for symptomatic neuromas. • Predicting the symptomatic neuroma on MRI would help in effective management of stump pain.

Final diagnosis and patient disposition following equivocal results on 2-mSv CT vs. conventional-dose CT in adolescents and young adults with suspected appendicitis: a post hoc analysis of large pragmatic randomized trial data.

OBJECTIVE: To compare 2-mSv CT and conventional-dose CT (CDCT, typically 7-8 mSv) regarding final diagnosis and patient disposition following equivocal CT results in adolescents and young adults with suspected appendicitis. METHODS: In total, 3074 patients of 15-44 years (28 ± 9 years, 1672 women) from 20 hospitals were randomized to undergo contrast-enhanced 2-mSv CT (n = 1535) or CDCT (n = 1539) from December 2013 through August 2016. One hundred sixty-one radiologists prospectively rated the likelihood of appendicitis in a Likert scale (i.e., grades 1-5). The final diagnosis was based on CT image, surgical, pathologic, and clinical findings. Post hoc analysis was performed for final diagnosis, surgical procedure, and delay in patient management following equivocal results (i.e., grade 3). RESULTS: The 2-mSv CT and CDCT groups were comparable for final diagnosis following equivocal results, including confirmed appendicitis (1.2% [18 patients] vs. 1.2% [19], p > 0.99), negative appendectomy (0.1% [2] vs. 0.3% [4], p = 0.53), and perforated appendicitis (0.1% [1] vs. 0.2% [3], p = 0.53). More patients were confirmed as not having appendicitis following equivocal results in the CDCT group than in the 2-mSv CT group (2.2% [34] vs. 1.0% [16], p = 0.016). The two groups were comparable for the need of appendectomy (1.4% [22] vs. 1.5% [23], p > 0.99), need of additional imaging tests (0.7% [11] vs. 1.1% [17], p = 0.35), and delay in patient management following equivocal results. CONCLUSION: 2-mSv CT is comparable to CDCT regarding final diagnosis and patient disposition following equivocal CT results. KEY POINTS: • Our results strengthen evidence justifying the use of low-dose CT instead of conventional-dose CT (CDCT) in adolescents and young adults with suspected appendicitis. • The 2-mSv CT and CDCT groups were comparable for final diagnosis following equivocal CT results, including confirmed appendicitis (1.2% vs. 1.2%, p > 0.99), negative appendectomy (0.1% vs. 0.3%, p = 0.53), and perforated appendicitis (0.1% vs. 0.2%, p = 0.53). • The two groups were comparable for the need for appendectomy (1.4% vs. 1.5%, p > 0.99), need for additional imaging tests (0.7% vs. 1.1%, p = 0.35), and delay in patient management, following equivocal CT results.

Conventional-Dose CT Versus 2-mSv CT for Right Colonic Diverticulitis as an Alternate Diagnosis of Appendicitis: Secondary Analysis of Large Pragmatic Randomized Trial Data.

BACKGROUND. Adoption of low-dose CT for the diagnosis of appendicitis has been slow in children and in adults, partly because of concern about missing alternative diagnoses including right colonic diverticulitis. OBJECTIVE. The purpose of our study was to retrospectively compare the diagnostic performance of IV contrast-enhanced 2-mSv and conventional-dose CT (CDCT) for the diagnosis of right colonic diverticulitis in adolescents and young adults with suspected appendicitis. METHODS. This post hoc analysis of a prospective randomized controlled trial included 3074 patients (1672 female patients and 1402 male patients) ranging in age from 15 to 44 years old (mean ± SD, 28 ± 9 years) from 20 hospitals. From December 2013 to August 2016, patients were randomized to either the 2-mSv CT group (n = 1535 patients) or the CDCT (median, 7 mSv) group (n = 1539 patients). A total of 161 radiologists prospectively issued CT reports in which they suggested alternative diagnoses for 976 (2-mSv CT) and 924 (CDCT) patients. Seven independent assessors adjudicated final diagnoses on the basis of clinical and CT findings. Endpoints of test-positives, test-negatives, sensitivity, and specificity for right colonic diverticulitis were compared using chi-square and Mann-Whitney U tests. Characteristics and disposition of patients with test-positive results were assessed. Four readers retrospectively reviewed CT images of 400 patients selected from the trial (113 and 108 patients with diverticulitis from 2-mSv CT and CDCT groups, respectively) to evaluate interobserver agreement for right colonic diverticulitis in terms of Gwet coefficients. RESULTS. Between-group differences were minute for most endpoints related to right colonic diverticulitis: test-positives (difference, 0.2% [95% CI, -1.8% to 2.1%]; 7.8% [119/1535 patients] vs 7.6% [117/1539 patients]; p = .93), test-negatives (0.5% [95% CI, -1.5% to 2.5%]; 91.7% [1407/1535] vs 91.2% [1403/1539]; p = .67), sensitivity (0% [95% CI, -6% to 6%]; 95% [110/116] vs 95% [105/111]; p > .99), and specificity (0.3% [95% CI, -0.5% to 0.9%]; 99.4% [1401/1410] vs 99.1% [1397/1409]; p = .66). The characteristics and disposition of test-positive patients were similar between the two groups. Gwet coefficients were high and comparable between the two groups (2-mSv CT vs CDCT, 0.849 vs 0.889; p = .20). CONCLUSION. Two-millisievert CT is comparable to conventional-dose CT for the diagnosis of right colonic diverticulitis. CLINICAL IMPACT. By mitigating concern about a missed diagnosis of right colonic diverticulitis, the results further support the use of low-dose CT in patients with suspected appendicitis. TRIAL REGISTRATION. ClinicalTrials.gov NCT01925014.

Recent trends in cell membrane-cloaked nanoparticles for therapeutic applications.

Synthetic nanoparticles are extensively utilized in various biomedical engineering fields because of their unique physicochemical properties. However, their exogenous characteristics result in synthetic nanosystem invaders that easily induce the passive immune clearance mechanism, thereby increasing the retention effect caused by reticuloendothelial system (RES), resulting in low therapeutic efficacy and toxic effects. Recently, a cell membrane cloaking has been emerging technique as a novel interfacing approach from the biological/immunological perspective. This has been considered as useful technique for improving the performance of synthetic nanocarriers in vivo. By cell membrane cloaking, nanoparticles acquire the biological functions of natural cell membranes due to the presence of membrane-anchored proteins, antigens, and immunological moieties as well as physicochemical property of natural cell membrane. Due to cell membrane cloaking, the derived biological properties and functions of nanoparticles such as their immunosuppressive capability, long circulation time, and disease targeting ability have enhanced their future potential in biomedicine. Here, we review the cell membrane-cloaked nanosystems, highlight their novelty, introduce the preparation and characterization methods with relevant biomedical applications, and describe the prospects for using this novel biomimetic system that was developed from a combination of cell membranes and synthetic nanomaterials.

Technical success rates and reliability of spin-echo echo-planar imaging (SE-EPI) MR elastography in patients with chronic liver disease or liver cirrhosis.

OBJECTIVES: To determine the technical success rates of MR elastography (MRE) according to established gradient-recalled echo (GRE) and spin-echo echo-planar imaging (SE-EPI) sequences and to compare liver stiffness (LS) values between the sequences during expiratory and inspiratory phases in patients with chronic liver disease or liver cirrhosis. METHODS: One hundred and eight patients who underwent MRE were included in this retrospective study. MRE was performed at 3 T based on both sequences during expiration as well as inspiration. Technical failure of MRE was determined if there was no pixel value with a confidence index higher than 95% and/or no apparent shear waves imaged. LS measurements were performed using free-drawing region of interest. To evaluate clinical factors related to the technical success rate of MRE, we assessed etiology of liver disease, ascites, body habitus, iron deposition, and liver morphology of patients. Statistical analysis was performed with the Wilcoxon test, Bland-Altman plot, independent t test, Mann-Whitney test, and McNemar test. RESULTS: The technical success rate of MRE in SE-EPI was significantly higher than that of GRE (98.1% vs. 80.7%, p < 0.0001). On the basis of univariate analysis, height, weight, and BMI were significantly associated with failure of MRE (p < 0.05). There was no significant difference in LS values between GRE and SE-EPI (2.82 kPa vs. 2.92 kPa (p > 0.05)). However, the LS values were significantly higher during inspiration than expiration with both GRE and SE-EPI (p < 0.0001). CONCLUSION: MRE in SE-EPI during expiratory breath-hold can be used as a reliable examination to evaluate liver fibrosis. KEY POINTS: • The technical success rate of MR elastography in spin-echo echo-planar imaging (SE-EPI) was significantly higher than that in gradient-recalled echo (GRE) during both the inspiratory and expiratory phases. • Liver stiffness values were significantly higher during inspiration than during expiration in both GRE and SE-EPI. • MR elastography in SE-EPI during expiratory breath-hold can be used as a reliable examination in patients with liver fibrosis.

Echogenic foci in thyroid nodules: diagnostic performance with combination of TIRADS and echogenic foci.

BACKGROUND: The malignancy risks of various echogenic foci in thyroid nodules are not consistent. The association between malignancy and echogenic foci and various Thyroid Imaging Reporting and Data System (TIRADS) in thyroid nodules has not been evaluated. We evaluated the malignancy probability and diagnostic performance of thyroid nodules with various echogenic foci and in combination with TIRADS. METHODS: This retrospective study was approved by Institutional Review Board. The data were retrospectively collected from January 2013 to December 2014. In total, 954 patients (mean age, 50.8 years; range, 13-86 years) with 1112 nodules were included. Using χ2 test, we determined the prevalence of benign and malignant nodules among those with and without echogenic foci; we associated each of 6 echogenic foci types with benign and malignant nodules. Diagnostic performance was compared between the 6 types alone and in combination with various TIRADS. RESULTS: Among 1112 nodules, 390 nodules (35.1%) were found to have echogenic foci, and 722 nodules (64.9%) were not. Among nodules with echogenic foci, 254 nodules (65.1%) were malignant. The punctate echogenic foci with comet-tail artifact showed malignancy rate of 77.8% in solid and predominantly solid nodules. Our study demonstrated relatively low PPV (33.3-56.4%) in nodules with large echogenic foci without shadowing, macrocalcification, and peripheral curvilinear or eggshell echogenic foci with or without shadowing. However, when combined with high suspicion category of TIRADS, PPV increased to 50.0-90.9%. CONCLUSION: Combination with TIRADS with different types of echogenic foci offer better stratification of the malignancy risk.

Usefulness of Testicular Volume, Apparent Diffusion Coefficient, and Normalized Apparent Diffusion Coefficient in the MRI Evaluation of Infertile Men With Azoospermia.

OBJECTIVE: The purpose of this article is to assess retrospectively the usefulness of testicular volume, apparent diffusion coefficient (ADC), and normalized ADC as measured using MRI in predicting the histopathologic grade of azoospermia and in differentiating obstructive from nonobstructive azoospermia. MATERIALS AND METHODS: A computerized search generated a list of 30 infertile men with azoospermia who had undergone both scrotal MRI and testis biopsy. MRI-determined testicular volumes, ADCs, and normalized ADCs were compared between infertile men with obstructive azoospermia and those with nonobstructive azoospermia. The normalized ADC was calculated as ADC of the testis divided by the ADC of the bladder lumen. RESULTS: Sixteen men had obstructive azoospermia and 14 had nonobstructive azoospermia. The testicular volume was significantly greater in patients with obstructive azoospermia (8.7-27.6 mL) than in patients with nonobstructive azoospermia (1.8-15.4 mL; p < 0.001). The ROC AUC for distinguishing nonobstructive from obstructive azoospermia using testicular volume was 0.92 (a cutoff value of ≤ 13.06 mL yielded sensitivity of 85.71% and specificity of 87.5%). Testicular ADC and normalized ADC were significantly lower in patients with obstructive azoospermia (0.329 × 10-3 to 1.578 × 10-3 mm2/s for ADC; 0.113 to 0.449 for normalized ADC) than in patients with nonobstructive azoospermia (0.801 × 10-3 to 2.211 × 10-3 mm2/s [p = 0.0094] for ADC; 0.235 to 0.61 [p = 0.0001] for normalized ADC). The ROC AUCs for distinguishing nonobstructive from obstructive azoospermia using testicular ADC and normalized ADC were 0.741 (a cutoff value of > 1.031 × 10-3 mm2/s yielded sensitivity of 92.86% and specificity of 56.25%) and 0.875 (a cutoff value of > 0.425 yielded sensitivity of 78.57% and specificity of 93.75%), respectively. CONCLUSION: Testicular volume, ADC, and normalized ADC, as measured using MRI, are useful in predicting the histopathologic grade of azoospermia and in differentiating obstructive from nonobstructive azoospermia.

The role of ultrasound in the evaluation of acute pelvic pain in pregnancy and postpartum period: a review.

PURPOSE OF REVIEW: Acute pelvic pain in pregnant and postpartum patients presents diagnostic and therapeutic challenges. Ultrasound remains the primary imaging modality of choice for assessing pregnant and postpartum women. The purpose of this review is to help practitioners ensure a correct diagnosis of acute pelvic pain in pregnancy and the postpartum period. RECENT FINDINGS: This review describes the various causes and highlights the sonographic features and characteristics of acute pelvic pain in pregnancy and the postpartum period. SUMMARY: Evaluation of acute pelvic pain in pregnancy and the postpartum period is challenging. Knowledge of the clinical settings and sonographic features of acute pelvic pain in pregnancy and the postpartum period can lead to accurate diagnosis and appropriate management of the condition.

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.

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.

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.

Superficial Echogenic Lesions Detected on Neonatal Cranial Sonography: Possible Indicators of Severe Birth Injury.

OBJECTIVES: The purpose of this study was to evaluate the characteristics and importance of superficial echogenic lesions around cranial sutures on neonatal cranial sonography. METHODS: We retrospectively reviewed the clinical records and neuroimaging studies of 40 neonates who had superficial echogenic lesions around sutures on neonatal cranial sonography. Magnetic resonance imaging (n = 18) and computed tomography (n = 2) were performed within 2 weeks after sonography. We correlated sonographic findings with computed tomographic and magnetic resonance imaging findings and analyzed them. We also evaluated the associated lesions, neurologic signs, and follow-up changes. RESULTS: Sonographically, the superficial echogenic lesions involved both sulci and perisulcal parenchyma in 39 neonates and were located in the frontal and parietal areas around the sagittal suture in 38 neonates. Magnetic resonance imaging revealed a pattern of hypoxic ischemic encephalopathy in 9 neonates, birth trauma in 3 neonates, a mixed pattern of hypoxic ischemic encephalopathy and trauma in 3 neonates, nonspecific single infarctions in 2 neonates, and lack of a defined lesion in 1 neonate. The associated lesions were subdural hemorrhage (n = 12), epidural hematoma (n = 4), germinal matrix hemorrhage (n = 3), intraventricular hemorrhage (n = 2), and periventricular leukomalacia (n = 1). All epidural hematomas were associated with scalp hematoma, and 2 patients had skull fractures. One neonate with epidural hematoma associated with a hypoxic ischemic encephalopathy pattern showed mild spasticity in both ankles until 16 months. CONCLUSIONS: Superficial echogenic lesions detected around cranial sutures on neonatal sonography may be an indicator of more serious intracranial lesions such as more extensive hypoxic ischemic encephalopathy and intracranial hematomas, including epidural hematoma.

Initial Performance of Radiologists and Radiology Residents in Interpreting Low-Dose (2-mSv) Appendiceal CT.

OBJECTIVE: The objective of our study was to prospectively evaluate the initial diagnostic performance and learning curve of a community of radiologists and residents in interpreting 2-mSv appendiceal CT. SUBJECTS AND METHODS: We included 46 attending radiologists and 153 radiology residents from 22 hospitals who completed an online training course of 30 2-mSv CT cases. Appendicitis was confirmed in 14 cases. Most of the readers had limited (≤ 10 cases, n = 32) or no (n = 118) prior experience with low-dose appendiceal CT. The order of cases was randomized for each reader. A multireader multicase ROC analysis was performed. Generalized estimating equations were used to model the learning curves in diagnostic performance. RESULTS: Diagnostic performance gradually improved with years of training. The average AUC was 0.94 (95% CI, 0.90-0.98), 0.92 (0.88-0.96), 0.90 (0.85-0.96), and 0.86 (0.80-0.92) for the attending radiologists, senior residents, 2nd-year residents, and 1st-year residents, respectively. We did not observe any notable intrareader learning curves over the training course of the 30 cases except a decrease in reading time. Diagnostic accuracy and sensitivity were significantly affected by the reader training level and prior overall experience with appendiceal CT but not by the prior specific experience with low-dose appendiceal CT. CONCLUSION: The learning curve is likely prolonged and forms gradually over years by overall radiology training and clinical experience in general rather than by experience with low-dose appendiceal CT specifically.

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.

Magnetic resonance imaging features of ovarian fibroma, fibrothecoma, and thecoma.

OBJECTIVE: To retrospectively evaluate the conventional and functional (diffusion- or perfusion-weighted) magnetic resonance (MR) imaging features of ovarian fibroma, fibrothecoma, and thecoma. MATERIALS AND METHODS: Histologically proven ovarian fibromas (n = 19), fibrothecomas (n = 7), and thecomas (n = 2) were reviewed (26 patients). The morphologic and signal intensity (SI) characteristics on conventional MR imaging (n = 28, all cases) were analyzed. The b 1000 signal intensity on diffusion-weighted image (DWI) (n = 22) and the time-to-signal intensity curve on perfusion-weighted image (PWI) (n = 7) were also analyzed. The presence and shape of the ipsilateral ovarian tissue surrounding the lesions were evaluated on T2-weighted image. RESULTS: Twenty-two cases (79%) were predominantly solid tumor. Majority of the detected lesions exhibited the characteristic homogeneous low SI on T1- (24/28, 86%) and T2- (19/28, 68%) weighted image. Conversely, a number of lesions exhibited high SI (9/28, 32%) on T2-weighted image. Most lesions presented with a detectable ipsilateral ovary on T2-weighted image (24/28, 86%). Tumors larger than 6 cm more likely showed atypical morphology (mixed solid and cystic, cystic), atypical SI (high on T1- and T2-weighted image), and large amount ascites. Larger tumor group (>6 cm) was more likely diagnosed as fibrothecoma or thecoma than fibroma by pathology. On DWI, 16 lesions showed low b 1000 signal intensity (16/22, 73%). On PWI, all lesions showed curve type 1 or 2 (7/7, 100%), which tends to characterize benign lesions. All (16/16, 100%) pre-menopausal women had a detectable ipsilateral ovary, and six (60%) out of 10 post-menopausal women had a detectable ipsilateral ovary (p < 0.05). CONCLUSIONS: Combining conventional morphologic and signal intensity characteristics with the findings from DWI or PWI might help differentiate ovarian fibroma, fibrothecoma, and thecoma from ovarian malignancy, although further prospective larger scale study using DWI and PWI is needed.

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.