Two-Stage Training Framework Using Multicontrast MRI Radiomics for IDH Mutation Status Prediction in Glioma.

Purpose To develop a radiomics framework for preoperative MRI-based prediction of isocitrate dehydrogenase (IDH) mutation status, a crucial glioma prognostic indicator. Materials and Methods Radiomics features (shape, first-order statistics, and texture) were extracted from the whole tumor or the combination of nonenhancing, necrosis, and edema regions. Segmentation masks were obtained via the federated tumor segmentation tool or the original data source. Boruta, a wrapper-based feature selection algorithm, identified relevant features. Addressing the imbalance between mutated and wild-type cases, multiple prediction models were trained on balanced data subsets using random forest or XGBoost and assembled to build the final classifier. The framework was evaluated using retrospective MRI scans from three public datasets (The Cancer Imaging Archive [TCIA, 227 patients], the University of California San Francisco Preoperative Diffuse Glioma MRI dataset [UCSF, 495 patients], and the Erasmus Glioma Database [EGD, 456 patients]) and internal datasets collected from the University of Texas Southwestern Medical Center (UTSW, 356 patients), New York University (NYU, 136 patients), and University of Wisconsin-Madison (UWM, 174 patients). TCIA and UTSW served as separate training sets, while the remaining data constituted the test set (1617 or 1488 testing cases, respectively). Results The best performing models trained on the TCIA dataset achieved area under the receiver operating characteristic curve (AUC) values of 0.89 for UTSW, 0.86 for NYU, 0.93 for UWM, 0.94 for UCSF, and 0.88 for EGD test sets. The best performing models trained on the UTSW dataset achieved slightly higher AUCs: 0.92 for TCIA, 0.88 for NYU, 0.96 for UWM, 0.93 for UCSF, and 0.90 for EGD. Conclusion This MRI radiomics-based framework shows promise for accurate preoperative prediction of IDH mutation status in patients with glioma. Keywords: Glioma, Isocitrate Dehydrogenase Mutation, IDH Mutation, Radiomics, MRI Supplemental material is available for this article. Published under a CC BY 4.0 license. See also commentary by Moassefi and Erickson in this issue.

Synthesizing 3D Multi-Contrast Brain Tumor MRIs Using Tumor Mask Conditioning.

Data scarcity and data imbalance are two major challenges in training deep learning models on medical images, such as brain tumor MRI data. The recent advancements in generative artificial intelligence have opened new possibilities for synthetically generating MRI data, including brain tumor MRI scans. This approach can be a potential solution to mitigate the data scarcity problem and enhance training data availability. This work focused on adapting the 2D latent diffusion models to generate 3D multi-contrast brain tumor MRI data with a tumor mask as the condition. The framework comprises two components: a 3D autoencoder model for perceptual compression and a conditional 3D Diffusion Probabilistic Model (DPM) for generating high-quality and diverse multi-contrast brain tumor MRI samples, guided by a conditional tumor mask. Unlike existing works that focused on generating either 2D multi-contrast or 3D single-contrast MRI samples, our models generate multi-contrast 3D MRI samples. We also integrated a conditional module within the UNet backbone of the DPM to capture the semantic class-dependent data distribution driven by the provided tumor mask to generate MRI brain tumor samples based on a specific brain tumor mask. We trained our models using two brain tumor datasets: The Cancer Genome Atlas (TCGA) public dataset and an internal dataset from the University of Texas Southwestern Medical Center (UTSW). The models were able to generate high-quality 3D multi-contrast brain tumor MRI samples with the tumor location aligned by the input condition mask. The quality of the generated images was evaluated using the Fréchet Inception Distance (FID) score. This work has the potential to mitigate the scarcity of brain tumor data and improve the performance of deep learning models involving brain tumor MRI data.

Workflow interruptions in an era of instant messaging: A detailed analysis.

INTRODUCTION: The complex practice environment and responsibilities incumbent on diagnostic radiologists creates a workflow susceptible to disruption. While interruptions have been shown to contribute to medical errors in the healthcare delivery environment, the exact impact on highly subspecialized services such as diagnostic radiology is less certain. One potential source of workflow disruption is the use of a departmental instant messaging system (Webex), to facilitate communications between radiology faculty, residents, fellows, and technologists. A retrospective review was conducted to quantify the frequency of interruption experienced by our neuroradiology fellows. MATERIALS AND METHODS: Data logs were gathered comprising all instant messages sent and received within the designated group chats from July 5-December 31, 2021, during weekday shifts staffed by neuroradiology fellows. Interruptions per shift were calculated based on month, week, and day of the week. RESULTS: 14,424 messages were sent across 289 total shifts. The 6 fellows assigned to the main neuroradiology reading room sent 3258 messages and received 10,260 messages from technologists and other staff. There was an average of 50 interruptions per shift when examined by month (range 48-53), and 52 interruptions per shift when examined by day of the week (range 40-60). CONCLUSION: Neuroradiology fellows experience frequent interruptions from the departmental instant messaging system. These disruptions, when considered in conjunction with other non-interpretative tasks, may have negative implications for workflow efficiency, requiring iterative process improvements when incorporating new technology into the practice environment of diagnostic radiology.

MRI-Based Deep Learning Method for Classification of IDH Mutation Status.

Isocitrate dehydrogenase (IDH) mutation status has emerged as an important prognostic marker in gliomas. This study sought to develop deep learning networks for non-invasive IDH classification using T2w MR images while comparing their performance to a multi-contrast network. Methods: Multi-contrast brain tumor MRI and genomic data were obtained from The Cancer Imaging Archive (TCIA) and The Erasmus Glioma Database (EGD). Two separate 2D networks were developed using nnU-Net, a T2w-image-only network (T2-net) and a multi-contrast network (MC-net). Each network was separately trained using TCIA (227 subjects) or TCIA + EGD data (683 subjects combined). The networks were trained to classify IDH mutation status and implement single-label tumor segmentation simultaneously. The trained networks were tested on over 1100 held-out datasets including 360 cases from UT Southwestern Medical Center, 136 cases from New York University, 175 cases from the University of Wisconsin-Madison, 456 cases from EGD (for the TCIA-trained network), and 495 cases from the University of California, San Francisco public database. A receiver operating characteristic curve (ROC) was drawn to calculate the AUC value to determine classifier performance. Results: T2-net trained on TCIA and TCIA + EGD datasets achieved an overall accuracy of 85.4% and 87.6% with AUCs of 0.86 and 0.89, respectively. MC-net trained on TCIA and TCIA + EGD datasets achieved an overall accuracy of 91.0% and 92.8% with AUCs of 0.94 and 0.96, respectively. We developed reliable, high-performing deep learning algorithms for IDH classification using both a T2-image-only and a multi-contrast approach. The networks were tested on more than 1100 subjects from diverse databases, making this the largest study on image-based IDH classification to date.

Diurnal variation of major error rates in the interpretation of abdominal/pelvic CT studies.

RATIONALE AND OBJECTIVE: Variation of visual selective attention through the day has been demonstrated in several arenas of human performance, including radiology. It is uncertain whether this variation translates to an identifiable diurnal pattern of error rates for radiology interpretation. The purpose of this study was to attempt to identify particular days of the week and times of the day when radiologists might be most prone to error. MATERIALS AND METHODS: Abdomen/pelvis CT studies containing at least one major error were collected from a 10-year period from the quality assurance (QA) database at our institution. A major error was defined as a missed finding that had altered management in a way potentially detrimental to the patient. The identified studies were categorized by the day of the week and hour of the day that the study was interpreted. Study volume data over this same period was also obtained by day of the week and time of day, so to normalize the data based on case volume. Standard errors of the volume-adjusted error rates were obtained based on the binomial distribution. The null hypothesis of constant error rates over time was tested using a weighted logistic regression model with linear time as predictor. RESULTS: A total of 252 major errors were identified. More errors were made on Monday than on any other day of the week (n = 58). Major error rates increased through the mid to late morning (9 am to 12 pm), and then decreased progressively through the afternoon until 4 pm, when a rise in the error rate was seen. This pattern persisted when error rates were normalized by study volume within each hour. Overall tests of time-constancy of error rates by day and hour were statistically significant (both p-values < 0.001). CONCLUSION: Our study shows that error rates in abdominal CT do seem to vary with time of day and day of the week. During the workweek, error rates were highest in the late morning and at the close of the workday, and greater on Mondays than other days.

No Cases of Nephrogenic Systemic Fibrosis after Administration of Gadoxetic Acid.

Background Gadoxetic acid (GA) has distinctive pharmacokinetic properties with important applications in hepatobiliary imaging. However, there are limited data evaluating the safety of GA administration in patients with impaired kidney function and the incidence of nephrogenic systemic fibrosis (NSF). Purpose To evaluate safety of GA regarding risk of NSF in patients with impaired kidney function. Materials and Methods This retrospective study identified all GA-enhanced MRI (hereafter, GA MRI) examinations performed between July 2008 and December 2019 through a search of the electronic medical record. Serum creatinine values within 180 days or less of each GA MRI examination were retrieved and estimated glomerular filtration rate (eGFR) was calculated. The eGFR value nearest to each MRI examination was used. A separate search in the electronic medical record was also performed to identify patients with NSF. Dermatologists, nephrologists, and nephrologists at our institution were surveyed for any cases of NSF. In patients with NSF, all MRI examinations performed and contrast agents administered to these patients were recorded. Results Overall, 7820 GA MRI examinations were identified, performed in 5351 patients (3022 women and 2329 men). These included 299 examinations (242 patients) with eGFR of 30-44 mL/min/1.73 m2 and 183 examinations (157 patients) with eGFR less than 30 mL/min/1.73 m2. There were 109 examinations (in 94 patients) with eGFR of 15-29 mL/min/1.73 m2, 40 examinations (in 39 patients) with eGFR less than 15 mL/min/1.73 m2, and 34 examinations in 27 patients undergoing hemodialysis. Seventeen patients with eGFR less than 30 mL/min/1.73 m2 or undergoing dialysis underwent GA MRI two or more times. Eighteen patients with biopsy-confirmed NSF were identified, none of whom were exposed to GA. The mean follow-up period for GA MRI examinations performed in patients with severe kidney impairment was 4.2 years (range, 0.2-11.3 years). Conclusion Gadoxetic acid may be safe with respect to nephrogenic systemic fibrosis in this patient population, although further studies are needed to confirm this. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Davenport and Shankar in this issue.

Statin Use is Protective Against Hepatocellular Carcinoma in Patients With Nonalcoholic Fatty Liver Disease: A Case-control Study.

BACKGROUND AND GOAL: The incidence of nonalcoholic fatty liver disease (NAFLD)-associated hepatocellular carcinoma (HCC) is rising. We aimed to characterize risk factors for NAFLD-HCC development. METHODS: We performed a retrospective case-control study of HCC cases from a cohort of NAFLD patients who underwent at least 2 computed tomography scans. NAFLD-HCC cases confirmed on contrast imaging and/or biopsy were included. Controls were NAFLD patients without HCC matched by sex and age. Clinical variables were assessed. Visceral adipose tissue and subcutaneous adipose tissue were measured by computed tomography at 2 timepoints: before HCC diagnosis and at diagnosis. RESULTS: We identified 102 subjects [34 HCC cases, 68 controls, 65% (n=66) males, mean age: 69 y] from 2002 to 2016. Cirrhosis was present in 91%. In multivariate analysis, statin use was protective against HCC [odds ratio (OR)=0.20, 95% confidence interval (CI): 0.07-0.60, P=0.004], while hypertension was a risk factor for HCC (OR=5.80, 95% CI: 2.01-16.75, P=0.001). In multivariate analysis, visceral adipose tissue in males was higher before HCC diagnosis and declined by HCC diagnosis in 86%, which was a significant difference compared with controls (OR=2.78, 95% CI: 1.10-7.44, P=0.04). CONCLUSIONS: In a cohort of NAFLD-HCC patients, statin use was protective against HCC, while hypertension conferred an increased risk. Visceral adiposity at baseline was not a risk factor, but was higher in male patients before HCC development, declining in the majority by HCC diagnosis.

A General Framework for Monitoring Image Acquisition Workflow in the Radiology Environment: Timeliness for Acute Stroke CT Imaging.

Many facets of an image acquisition workflow leave a digital footprint, making workflow analysis amenable to an informatics-based solution. This paper describes a detailed framework for analyzing workflow and uses acute stroke response timeliness in CT as a practical demonstration. We review methods for accessing the digital footprints resulting from common technologist/device interactions. This overview lays a foundation for obtaining data for workflow analysis. We demonstrate the method by analyzing CT imaging efficiency in the setting of acute stroke. We successfully used digital footprints of CT technologists to analyze their workflow. We presented an overview of other digital footprints including but not limited to contrast administration, patient positioning, billing, reformat creation, and scheduling. A framework for analyzing image acquisition workflow was presented. This framework is transferable to any modality, as the key steps of image acquisition, image reconstruction, image post processing, and image transfer to PACS are common to any imaging modality in diagnostic radiology.

Opportunistic screening for osteoporosis using abdominal computed tomography scans obtained for other indications.

BACKGROUND: Osteoporosis is a prevalent but underdiagnosed condition. OBJECTIVE: To evaluate computed tomography (CT)-derived bone mineral density (BMD) assessment compared with dual-energy x-ray absorptiometry (DXA) measures for identifying osteoporosis by using CT scans performed for other clinical indications. DESIGN: Cross-sectional study. SETTING: Single academic health center. PATIENTS: 1867 adults undergoing CT and DXA (n = 2067 pairs) within a 6-month period over 10 years. MEASUREMENTS: CT-attenuation values (in Hounsfield units [HU]) of trabecular bone between the T12 and L5 vertebral levels, with an emphasis on L1 measures (study test); DXA BMD measures (reference standard). Sagittal CT images assessed for moderate-to-severe vertebral fractures. RESULTS: CT-attenuation values were significantly lower at all vertebral levels for patients with DXA-defined osteoporosis (P < 0.001). An L1 CT-attenuation threshold of 160 HU or less was 90% sensitive and a threshold of 110 HU was more than 90% specific for distinguishing osteoporosis from osteopenia and normal BMD. Positive predictive values for osteoporosis were 68% or greater at L1 CT-attenuation thresholds less than 100 HU; negative predictive values were 99% at thresholds greater than 200 HU. Among 119 patients with at least 1 moderate-to-severe vertebral fracture, 62 (52.1%) had nonosteoporotic T-scores (DXA false-negative results), and most (97%) had L1 or mean T12 to L5 vertebral attenuation of 145 HU or less. Similar performance was seen at all vertebral levels. Intravenous contrast did not affect CT performance. LIMITATION: The potential benefits and costs of using the various CT-attenuation thresholds identified were not formally assessed. CONCLUSION: Abdominal CT images obtained for other reasons that include the lumbar spine can be used to identify patients with osteoporosis or normal BMD without additional radiation exposure or cost. PRIMARY FUNDING SOURCE: National Institutes of Health.

Unreported vertebral body compression fractures at abdominal multidetector CT.

PURPOSE: To retrospectively assess the prevalence and clinical outcomes of unreported vertebral compression fractures at abdominal computed tomography (CT). MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval; the need for informed consent was waived for this retrospective analysis. A total of 2041 consecutive adult patients (1640 women, 401 men; age range, 19-94 years) underwent both abdominal multidetector CT and dual-energy x-ray absorptiometry (DXA) within 6 months of each other between 2000 and 2007, before sagittal CT reconstructions were obtained routinely. Transverse (axial) and retrospective sagittal multidetector CT reconstructions were reviewed for the presence of moderate or severe vertebral body compression fractures of the lower thoracic and lumbar spine by using the Genant visual semiquantitative method. Twenty-six patients were excluded for evidence of pathologic fracture or for technical factors limiting compression fracture detection. Electronic medical records were reviewed for patients with moderate or severe compression fractures to determine whether the fracture was reported at prospective CT interpretation, was known previously, or was diagnosed subsequently. Correlation was made with central DXA T scores. Statistical analysis was performed with the Student t test and Fisher exact test. RESULTS: At least one moderate or severe vertebral body compression fracture was identified retrospectively at CT in 97 patients (mean age, 70.8 years). Fractures involved one level in 67 and multiple levels in 30 patients, for a total of 141 fractures. In 81 (84%) patients, prospective CT diagnosis was not made. Patients in whom fractures were reported prospectively were significantly older and were more likely to have a severe compression fracture (P < .05). In 52 (64%) patients with an unreported fracture, the vertebral compression fracture was not known clinically. In 18 patients, subsequent diagnosis of a compression fracture was determined by means of another imaging study (median interval, 7 months). At DXA, 39 (48%) of 81 patients with unreported vertebral body compression fractures had a nonosteoporotic T score (greater than -2.5). CONCLUSION: Most clinically important vertebral body compression fractures in nontrauma patients at risk for low bone mineral density may go unreported at abdominal multidetector CT if sagittal reconstructions are not routinely evaluated.

Renal cell carcinoma: attenuation values on unenhanced CT.

OBJECTIVE: The purpose of this study is to analyze the attenuation values of pathologically proven renal cell carcinomas (RCCs) on unenhanced CT and to determine the range of values wherein malignancy should be considered. MATERIALS AND METHODS: A retrospective review was performed of 189 consecutive patients with 193 pathologically proven RCCs 1 cm or larger on unenhanced CT. For each RCC, attenuation values were assessed throughout the tumor by continuous sampling with a 25-100-mm(2) region of interest (ROI), avoiding foci of calcification and peritumoral volume averaging. The lowest and highest ROI attenuation values per lesion were recorded. Each tumor was categorized as either homogeneous or heterogeneous on the basis of visual inspection with soft-tissue window settings. RESULTS: The 193 malignant tumors ranged in size from 1.1 to 20.1 cm (mean [± SD], 5.1 ± 3.4 cm). Eighteen RCCs (9.3%) were homogeneous in appearance on unenhanced CT. The minimum and maximum ROI attenuation values obtained by sampling throughout each tumor were 27.5 ± 10.4 HU (range, 4-67 HU) and 39.7 ± 10.6 HU (range, 21-80 HU), respectively. Regional areas of minimum attenuation less than 20 HU and maximum attenuation greater than 70 HU were seen in 24.9% (48/193) and 2.1% (4/193) of RCCs, respectively. However, all 193 RCCs (100%) were predominantly composed of noncalcific regions within 20-70 HU; 72.5% (140/193) fell entirely within this 20-70 HU "danger zone," including all 18 homogeneous lesions. CONCLUSION: All proven RCCs in this series contained substantial noncalcified regions that measured 20-70 HU in ROI attenuation on unenhanced CT. Indeterminate renal lesions on unenhanced CT measuring within this 20-70-HU danger zone warrant further workup, whereas lesions that fall entirely outside this range may be considered benign.

Diagnostic performance of multidetector computed tomography for suspected acute appendicitis.

BACKGROUND: Use of preoperative computed tomography for suspected acute appendicitis has dramatically increased since the introduction of multidetector CT (MDCT) scanners. OBJECTIVE: To evaluate the diagnostic performance of MDCT for suspected acute appendicitis in adults. DESIGN: Analysis of MDCT findings and clinical outcomes of consecutive adults referred for MDCT for suspected appendicitis from January 2000 to December 2009. SETTING: Single academic medical center in the United States. PATIENTS: 2871 adults. MEASUREMENTS: Interpretation of nonfocused abdominopelvic MDCT scans by radiologists who were aware of the study indication. Posttest assessment of diagnostic performance of MDCT for acute appendicitis, according to the reference standard of final combined clinical, surgical, and pathology findings. RESULTS: 675 of 2871 patients (23.5%) had confirmed acute appendicitis. The sensitivity, specificity, and negative and positive predictive values of MDCT were 98.5% (95% CI, 97.3% to 99.2%) (665 of 675 patients), 98.0% (CI, 97.4% to 98.6%) (2153 of 2196 patients), 99.5% (CI, 99.2% to 99.8%) (2153 of 2163 patients), and 93.9% (CI, 91.9% to 95.5%) (665 of 708 patients), respectively. Positive and negative likelihood ratios were 51.3 (CI, 38.1 to 69.0) and 0.015 (CI, 0.008 to 0.028), respectively. The overall rate of negative findings at appendectomy was 7.5% (CI, 5.8% to 9.7%) (54 of 716 patients), but would have decreased to 4.1% (28 of 690 patients) had surgery been avoided in 26 cases with true-negative findings on MDCT. The overall perforation rate was 17.8% (120 of 675 patients) but progressively decreased from 28.9% in 2000 to 11.5% in 2009. Multidetector computed tomography provided or suggested an alternative diagnosis in 893 of 2122 patients (42.1%) without appendicitis or appendectomy. LIMITATION: Possible referral bias, because some patients whose appendicitis was difficult to diagnose on clinical grounds may not have been referred for MDCT for evaluation of suspected appendicitis. CONCLUSION: Multidetector computed tomography is a useful test for routine evaluation of suspected appendicitis in adults. PRIMARY FUNDING SOURCE: None.

Simultaneous screening for osteoporosis at CT colonography: bone mineral density assessment using MDCT attenuation techniques compared with the DXA reference standard.

The purpose of this study was to evaluate the utility of lumbar spine attenuation measurement for bone mineral density (BMD) assessment at screening computed tomographic colonography (CTC) using central dual-energy X-ray absorptiometry (DXA) as the reference standard. Two-hundred and fifty-two adults (240 women and 12 men; mean age 58.9 years) underwent CTC screening and central DXA BMD measurement within 2 months (mean interval 25.0 days). The lowest DXA T-score between the spine and hip served as the reference standard, with low BMD defined per World Health Organization as osteoporosis (DXA T-score ≤ -2.5) or osteopenia (DXA T-score between -1.0 and -2.4). Both phantomless quantitative computed tomography (QCT) and simple nonangled region-of-interest (ROI) multi-detector CT (MDCT) attenuation measurements were applied to the T(12) -L(5) levels. The ability to predict osteoporosis and low BMD (osteoporosis or osteopenia) by DXA was assessed. A BMD cut-off of 90 mg/mL at phantomless QCT yielded 100% sensitivity for osteoporosis (29 of 29) and a specificity of 63.8% (143 of 224); 87.2% (96 of 110) below this threshold had low BMD and 49.6% (69 of 139) above this threshold had normal BMD at DXA. At L(1) , a trabecular ROI attenuation cut-off of 160 HU was 100% sensitive for osteoporosis (29 of 29), with a specificity of 46.4% (104 of 224); 83.9% (125 of 149) below this threshold had low BMD and 57.5% (59/103) above had normal BMD at DXA. ROI performance was similar at all individual T(12) -L(5) levels. At ROC analysis, AUC for osteoporosis was 0.888 for phantomless QCT [95% confidence interval (CI) 0.780-0.946] and ranged from 0.825 to 0.853 using trabecular ROIs at single lumbar levels (0.864; 95% CI 0.752-0.930 at multivariate analysis). Supine-prone reproducibility was better with the simple ROI method compared with QCT. It is concluded that both phantomless QCT and simple ROI attenuation measurements of the lumbar spine are effective for BMD screening at CTC with high sensitivity for osteoporosis, as defined by the DXA T-score.

Hepatic steatosis (fatty liver disease) in asymptomatic adults identified by unenhanced low-dose CT.

OBJECTIVE: The purpose of this study was to investigate the prevalence of hepatic steatosis in an asymptomatic U.S. adult population using attenuation values at unenhanced CT as the reference standard. We also assessed the utility of known clinical risk factors for diagnosis. MATERIALS AND METHODS: For 3,357 consecutive asymptomatic adults (1,865 women and 1,492 men; mean age, 57.0 years), hepatic and splenic CT attenuation values (Hounsfield units) were obtained by unenhanced CT using a low-dose colonography technique for colorectal cancer screening. Multiple attenuation criteria for steatosis were applied, including liver thresholds and comparison of liver and spleen attenuation. Relevant clinical risk factors were compared against a CT liver attenuation < or = 40 HU, which has been shown to exclude mild steatosis. RESULTS: Mean liver attenuation was 58.8 +/- 10.8 (SD) HU. The prevalence of moderate-to-severe hepatic steatosis (defined by liver attenuation < or = 40 HU) was 6.2% (208/3,357). For CT attenuation criteria that include milder degrees of steatosis, prevalence increased to as high as 45.9% (1,542/3,357) for a liver-to-spleen attenuation ratio of < or = 1.1. Overweight status (body mass index > 25) was a sensitive indicator for moderate-to-severe steatosis (92.8%) but was highly nonspecific (37.5%). Other clinical risk factors, such as diabetes, dyslipidemia, hypertension, alcohol overuse, and hepatitis, were more specific (77.6-92.4%) but highly insensitive (1.9-37.5%). Combining clinical risk factors did not substantially increase the accuracy for screening. CONCLUSION: Assessment of liver attenuation by use of unenhanced CT represents an objective and noninvasive means for detection of asymptomatic hepatic steatosis, whereas clinical risk factor assessment is unreliable. Further longitudinal investigation is needed to determine the most appropriate attenuation threshold and the risk for disease progression to steatohepatitis and cirrhosis.

Prevalence of urolithiasis in asymptomatic adults: objective determination using low dose noncontrast computerized tomography.

PURPOSE: The true prevalence of urolithiasis in asymptomatic adults is unknown. Unenhanced computerized tomography represents the gold standard for detection. We evaluated the prevalence and symptomatic incidence of urolithiasis in a large cohort of asymptomatic adults using noncontrast computerized tomography. MATERIALS AND METHODS: Low dose noncontrast computerized tomography was performed in 5,047 consecutive asymptomatic adults (mean age 56.9 years, 2,747 women and 2,300 men) between 2004 and 2008. Presence, size and location of urinary calculi were recorded. Screening prevalence as well as the incidence of symptomatic stone disease during a 10-year interval (1997 to 2007) was compared against previously established clinical risk factors. RESULTS: The screening prevalence of asymptomatic urolithiasis was 7.8% (395 of 5,047 adults) with an average of 2.1 stones per case (range 1 to 29) and a mean stone size of 3.0 mm (range 1 to 20). During a 10-year period 20.5% (81 of 395) of patients with stones (1.6% of entire screening cohort) had at least 1 symptomatic episode. Males were more likely to have urolithiasis than females (9.7% vs 6.3%, p <0.001). Diabetes (9.0% vs 7.7%, p = 0.45), obesity (7.6% vs 7.9%, p = 0.72) and age 60 years or older (8.0% vs 7.7%, p = 0.73) did not affect prevalence, but diabetes and obesity did correlate with symptom development (p <0.001 and p <0.05, respectively). CONCLUSIONS: This objective population based assessment in a large asymptomatic cohort showed an 8% prevalence of urolithiasis. Most cases were unsuspected and remained asymptomatic. Although there was no correlation between asymptomatic urolithiasis and diabetes, obesity or older age, diabetes and obesity were associated with a higher incidence of symptoms over time.

Background fluctuation of kidney function versus contrast-induced nephrotoxicity.

OBJECTIVE: The reported incidence of contrast-induced acute kidney injury varies widely. Almost no studies have been conducted to quantify the background fluctuation of kidney function of patients receiving iodinated contrast medium. The purpose of this study was a retrospective comparison of the incidence of acute kidney injury among patients undergoing CT with low-osmolar (iohexol) or isoosmolar (iodixanol) contrast medium with the incidence among patients undergoing CT without contrast administration. MATERIALS AND METHODS: Creatinine concentration and estimated glomerular filtration rate were evaluated for 11,588 patients. Rates of acute kidney injury (defined as a 0.5 mg/dL increase in serum creatinine concentration or a 25% or greater decrease in estimated glomerular filtration rate within 3 days after CT) were compared among groups and stratified according to creatinine concentration and estimated glomerular filtration rate before the imaging examination. RESULTS: In all groups, the incidence of acute kidney injury increased with increasing baseline creatinine concentration. No significant difference in incidence of presumed contrast-induced kidney injury was identified between the isoosmolar contrast medium and the control groups. The incidence of acute kidney injury in the low-osmolar contrast medium cohort paralleled that of the control cohort up to a creatinine level of 1.8 mg/dL, but increases above this level were associated with a higher incidence of acute kidney injury. CONCLUSION: We identified a high incidence of acute kidney injury among control subjects undergoing unenhanced CT. The incidence of creatinine elevation in this group was statistically similar to that in the isoosmolar contrast medium group for all baseline creatinine values and all stages of chronic kidney disease. These findings suggest that the additional risk of acute kidney injury accompanying administration of contrast medium (contrast-induced nephrotoxicity) may be overstated and that much of the creatinine elevation in these patients is attributable to background fluctuation, underlying disease, or treatment.