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INTRODUCTION - Cross-sectional data note lower levels of testosterone and sex hormone-binding globulin (SHBG) levels in men with nonalcoholic fatty liver disease (NAFLD). Whether sex hormone levels in young men are predictive of later risk of NAFLD is not known.
METHODS - Among men in the prospective population-based multicenter Coronary Artery Risk Development in Young Adults study (mean age 50; n = 837), we assessed whether testosterone and SHBG levels measured at study year 10 (median age 35 years) were associated with prevalent NAFLD at study year 25. NAFLD was defined using noncontrast abdominal computed tomography (CT) scan after excluding other causes of hepatic steatosis. The association of testosterone and SHBG with prevalent NAFLD was assessed by logistic regression.
RESULTS - Total testosterone levels in young men were inversely associated with subsequent prevalent NAFLD on unadjusted analysis (odds ratio [OR] 0.64, 95% confidence interval 0.53-0.7, P < 0.001), although no longer significant after adjustment for year 10 metabolic covariates as well as change in metabolic covariates from years 10 to 25 (OR 0.99, 95% confidence interval 0.76-1.27). In contrast, there was a significant inverse association of SHBG with prevalent NAFLD, independent of testosterone and metabolic covariates (OR 0.68, OR 0.51-0.92, P = 0.013). On formal mediation testing, visceral adiposity was found to explain ∼41.0% (95% confidence interval 27%-73%) of the association of lower SHBG with prevalent NAFLD.
CONCLUSIONS - Lower levels of SHBG in young men are associated with increase in prevalent NAFLD in middle age, independent of comprehensive metabolic risk factors. SHBG may provide a novel marker of NAFLD risk in young men.
OBJECTIVE - This work evaluates current 3-D image registration tools on clinically acquired abdominal computed tomography (CT) scans.
METHODS - Thirteen abdominal organs were manually labeled on a set of 100 CT images, and the 100 labeled images (i.e., atlases) were pairwise registered based on intensity information with six registration tools (FSL, ANTS-CC, ANTS-QUICK-MI, IRTK, NIFTYREG, and DEEDS). The Dice similarity coefficient (DSC), mean surface distance, and Hausdorff distance were calculated on the registered organs individually. Permutation tests and indifference-zone ranking were performed to examine the statistical and practical significance, respectively.
RESULTS - The results suggest that DEEDS yielded the best registration performance. However, due to the overall low DSC values, and substantial portion of low-performing outliers, great care must be taken when image registration is used for local interpretation of abdominal CT.
CONCLUSION - There is substantial room for improvement in image registration for abdominal CT.
SIGNIFICANCE - All data and source code are available so that innovations in registration can be directly compared with the current generation of tools without excessive duplication of effort.
Abdominal segmentation on clinically acquired computed tomography (CT) has been a challenging problem given the inter-subject variance of human abdomens and complex 3-D relationships among organs. Multi-atlas segmentation (MAS) provides a potentially robust solution by leveraging label atlases via image registration and statistical fusion. We posit that the efficiency of atlas selection requires further exploration in the context of substantial registration errors. The selective and iterative method for performance level estimation (SIMPLE) method is a MAS technique integrating atlas selection and label fusion that has proven effective for prostate radiotherapy planning. Herein, we revisit atlas selection and fusion techniques for segmenting 12 abdominal structures using clinically acquired CT. Using a re-derived SIMPLE algorithm, we show that performance on multi-organ classification can be improved by accounting for exogenous information through Bayesian priors (so called context learning). These innovations are integrated with the joint label fusion (JLF) approach to reduce the impact of correlated errors among selected atlases for each organ, and a graph cut technique is used to regularize the combined segmentation. In a study of 100 subjects, the proposed method outperformed other comparable MAS approaches, including majority vote, SIMPLE, JLF, and the Wolz locally weighted vote technique. The proposed technique provides consistent improvement over state-of-the-art approaches (median improvement of 7.0% and 16.2% in DSC over JLF and Wolz, respectively) and moves toward efficient segmentation of large-scale clinically acquired CT data for biomarker screening, surgical navigation, and data mining.
Copyright © 2015 Elsevier B.V. All rights reserved.
PURPOSE - The treatment of ventral hernias (VH) has been a challenging problem for medical care. Repair of these hernias is fraught with failure; recurrence rates ranging from 24% to 43% have been reported, even with the use of biocompatible mesh. Currently, computed tomography (CT) is used to guide intervention through expert, but qualitative, clinical judgments, notably, quantitative metrics based on image-processing are not used. The authors propose that image segmentation methods to capture the three-dimensional structure of the abdominal wall and its abnormalities will provide a foundation on which to measure geometric properties of hernias and surrounding tissues and, therefore, to optimize intervention.
METHODS - In this study with 20 clinically acquired CT scans on postoperative patients, the authors demonstrated a novel approach to geometric classification of the abdominal. The authors' approach uses a texture analysis based on Gabor filters to extract feature vectors and follows a fuzzy c-means clustering method to estimate voxelwise probability memberships for eight clusters. The memberships estimated from the texture analysis are helpful to identify anatomical structures with inhomogeneous intensities. The membership was used to guide the level set evolution, as well as to derive an initial start close to the abdominal wall.
RESULTS - Segmentation results on abdominal walls were both quantitatively and qualitatively validated with surface errors based on manually labeled ground truth. Using texture, mean surface errors for the outer surface of the abdominal wall were less than 2 mm, with 91% of the outer surface less than 5 mm away from the manual tracings; errors were significantly greater (2-5 mm) for methods that did not use the texture.
CONCLUSIONS - The authors' approach establishes a baseline for characterizing the abdominal wall for improving VH care. Inherent texture patterns in CT scans are helpful to the tissue classification, and texture analysis can improve the level set segmentation around the abdominal region.
Lung cancer screening computed tomographies (CTs) differ from traditional chest CT scans in that they are performed at very low radiation doses, which allow the detection of small nodules but which have a much higher noise content than would be acceptable in a diagnostic chest CT. The technical parameters require a great deal of attention on the part of the user, because inappropriate settings could result in either excess radiation dose to the large population of screened individuals or in low-quality images with impaired nodule detectability. Both situations undermine the main goal of the screening program, which is to detect lung nodules using as low a radiation dose as can reasonably be achieved. Once an image has been obtained, there are unique interpretive issues that must be addressed mainly because of the very high noise content of the images and the high prevalence of incidental findings in the chest unrelated to the sought-after pulmonary nodules.
BACKGROUND - An electromagnetic tube placement device (ETPD) monitors tip position of feeding tubes (FT) during placement in the digestive tract. It helps to avoid airway misplacement and permits positioning into the small bowel (SB). This study compares the overall agreement between FT tip location as determined by an ETPD vs an abdominal radiograph of the kidneys, ureter, and bladder (KUB).
METHODS - Using an ETPD, A nurse placed postpyloric FTs in ICU patients. We included all patients in whom the ETPD was used for FT placement. Data were prospectively recorded for 255 days on the rate of successful postpyloric placement, ETPD estimated tip location, and KUB location.
RESULTS - 860 tubes were placed in 616 patients, 719 (83.6%) of which recorded for ETPD and KUB. According to the KUB, 81% of tubes were in the SB; however, ETPD suggested 89% were beyond the pylorus. There was moderate agreement beyond what could be attributed to chance between KUB and ETPD tip locations (475 [66.1%], κ score 0.62 [95% confidence interval 0.58-0.67]). More tubes by KUB were distal (134[18.6%]) vs proximal (110[15.3%]) to the suspected location by ETPD (P < .0001. Tubes in or distal to the second half of the duodenum, according to ETPD were rarely in the stomach (<1%). No tubes were proximal to the stomach or placed into the airway.
CONCLUSIONS - The strong agreement between KUB and ETPD, when tubes were believed to be in the second part of the duodenum or beyond, suggests that KUB is necessary only when the FT tip is suspected to be in the proximal duodenum.
OBJECTIVE - The objective of our study was to correlate the location of radiologic presentation and time to onset of posttransplantation lymphoproliferative disorder (PTLD) with the allograft type received in a population of pediatric heart, lung, liver, kidney, and bone marrow transplant recipients.
CONCLUSION - Symptomatic PTLD in children manifests earliest in lung recipients and can involve any organ system. However, PTLD in the thorax is most common after lung transplantation, and PTLD in the abdomen most commonly follows kidney transplantation.
OBJECTIVES - To develop a method and evaluate the performance of thoracic bone mineral density (BMD) measurement using cardiac gated quantitative computed tomography (QCT).
METHODS - A total of 762 participants (57% female) with a mean age of 61 years had a CT examination of the heart using prospective cardiac gating. A subset of 443 participants had replicate CT examinations of the heart. Another, nonindependent subset of 464 participants had CT examination of the abdomen. A QCT calibration phantom was included in all scans. Trabecular BMD was measured in the thoracic (T6-T11) and lumbar (T11-L4) spine. Tests of calibration and refinement and simple correlations between replicate thoracic BMD measurements and between thoracic and lumbar BMD measurements were calculated.
RESULTS - There was high correlation between replicated thoracic BMD measurements in men (r = 0.995, P < 0.0001) and in women (r = 0.995, P < 0.0001). There was high correlation between thoracic and lumbar BMD in men (r = 0.90, P < 0.0001) and in women (r = 0.94, P < 0.0001). The mean BMD was higher in the thoracic spine than the lumbar spine in men (137.58 mg/cm3 vs. 126.94 mg/cm3, P < 0.0001) and in women (152.07 mg/cm3 vs. 133.44 mg/cm3, P < 0.0001). In both genders, thoracic and lumbar BMD was inversely associated with age (all P < 0.05).
CONCLUSIONS - Cardiac gated CT, primarily intended for measurement of coronary vascular calcium, can be used to measure thoracic BMD with high precision. Thoracic BMD measurements using this method are highly correlated with QCT measurements in the lumbar spine.