Association between visceral adiposity and colorectal polyps on CT colonography

Development of Multiscale 3D Residual U-Net to Segment Edematous Adipose Tissue by Leveraging Annotations from Non-Edematous Adipose Tissue

Data annotation is often a prerequisite for applying deep learning to medical image segmentation. It is a tedious process that requires substantial guidance from experienced physicians. Adipose tissue labeling on CT scans is particularly time-consuming because adipose tissue is present throughout the entire body. One possible solution is to create inaccurate annotations from conventional (non-deep learning) adipose tissue segmentation methods. This work demonstrates the development of a deep learning model directly from these inaccurate annotations. The model is a multi-scale 3D residual U-Net where the encoder path is composed of residual blocks and the decoder path fuses multi-scale feature maps from different layers of decoder blocks. The training set consisted of 101 patients and the testing set consisted of 14 patients. Ten patients with anasarca were purposely added to the testing dataset as a stress test to evaluate model generality. Anasarca is a medical condition that leads to the generalized accumulation of edema within subcutaneous adipose tissue. Edema creates heterogeneity inside the adipose tissue which is absent in the training data. In comparison with a baseline method of manual annotations, the Dice coefficient improved significantly from 73.4 ± 14.1% to 80.2 ± 7.1% (p < 0.05). The model trained on inaccurate annotations improved the accuracy of adipose tissue segmentation by 7% without the need for any manual annotation.

Technical Adequacy of Fully Automated Artificial Intelligence Body Composition Tools: Assessment in a Heterogeneous Sample of External CT Examinations

BACKGROUND. Clinically usable artificial intelligence (AI) tools analyzing imaging studies should be robust to expected variations in study parameters. OBJECTIVE. The purposes of this study were to assess the technical adequacy of a set of automated AI abdominal CT body composition tools in a heterogeneous sample of external CT examinations performed outside of the authors' hospital system and to explore possible causes of tool failure. METHODS. This retrospective study included 8949 patients (4256 men, 4693 women; mean age, 55.5 ± 15.9 years) who underwent 11,699 abdominal CT examinations performed at 777 unique external institutions with 83 unique scanner models from six manufacturers with images subsequently transferred to the local PACS for clinical purposes. Three independent automated AI tools were deployed to assess body composition (bone attenuation, amount and attenuation of muscle, amount of visceral and sub-cutaneous fat). One axial series per examination was evaluated. Technical adequacy was defined as tool output values within empirically derived reference ranges. Failures (i.e., tool output outside of reference range) were reviewed to identify possible causes. RESULTS. All three tools were technically adequate in 11,431 of 11,699 (97.7%) examinations. At least one tool failed in 268 (2.3%) of the examinations. Individual adequacy rates were 97.8% for the bone tool, 99.1% for the muscle tool, and 98.9% for the fat tool. A single type of image processing error (anisometry error, due to incorrect DICOM header voxel dimension information) accounted for 81 of 92 (88.0%) examinations in which all three tools failed, and all three tools failed whenever this error occurred. Anisometry error was the most common specific cause of failure of all tools (bone, 31.6%; muscle, 81.0%; fat, 62.8%). A total of 79 of 81 (97.5%) anisometry errors occurred on scanners from a single manufacturer; 80 of 81 (98.8%) occurred on the same scanner model. No cause of failure was identified for 59.4% of failures of the bone tool, 16.0% of failures of the muscle tool, or 34.9% of failures of the fat tool. CONCLUSION. The automated AI body composition tools had high technical adequacy rates in a heterogeneous sample of external CT examinations, supporting the generalizability of the tools and their potential for broad use. CLINICAL IMPACT. Certain causes of AI tool failure related to technical factors may be largely preventable through use of proper acquisition and reconstruction protocols.

Fully automated CT-based adiposity assessment: comparison of the L1 and L3 vertebral levels for opportunistic prediction

PURPOSE

The purpose of this study is to compare fully automated CT-based measures of adipose tissue at the L1 level versus the standard L3 level for predicting mortality, which would allow for use at both chest (L1) and abdominal (L3) CT.

METHODS

This retrospective study of 9066 asymptomatic adults (mean age, 57.1 ± 7.8 [SD] years; 4020 men, 5046 women) undergoing unenhanced low-dose abdominal CT for colorectal cancer screening. A previously validated artificial intelligence (AI) tool was used to assess cross-sectional visceral and subcutaneous adipose tissue areas (SAT and VAT), as well as their ratio (VSR) at the L1 and L3 levels. Post-CT survival prediction was compared using area under the ROC curve (ROC AUC) and hazard ratios (HRs).

RESULTS

Median clinical follow-up interval after CT was 8.8 years (interquartile range, 5.2-11.6 years), during which 5.9% died (532/9066). No significant difference (p > 0.05) for mortality was observed between L1 and L3 VAT and SAT at 10-year ROC AUC. However, L3 measures were significantly better for VSR at 10-year AUC (p < 0.001). HRs comparing worst-to-best quartiles for mortality at L1 vs. L3 were 2.12 (95% CI, 1.65-2.72) and 2.22 (1.74-2.83) for VAT; 1.20 (0.95-1.52) and 1.16 (0.92-1.46) for SAT; and 2.26 (1.7-2.93) and 3.05 (2.32-4.01) for VSR. In women, the corresponding HRs for VSR were 2.58 (1.80-3.69) (L1) and 4.49 (2.98-6.78) (L3).

CONCLUSION

Automated CT-based measures of visceral fat (VAT and VSR) at L1 are predictive of survival, although overall measures of adiposity at L1 level are somewhat inferior to the standard L3-level measures. Utilizing predictive L1-level fat measures could expand opportunistic screening to chest CT imaging.

Association of Apremilast With Vascular Inflammation and Cardiometabolic Function in Patients With Psoriasis: The VIP-A Phase 4, Open-label, Nonrandomized Clinical Trial

Importance

Psoriasis is an inflammatory condition associated with metabolic and cardiovascular disease. Apremilast, a phosphodiesterase 4 inhibitor, is commonly used for psoriasis and can cause weight loss.

Objective

To determine the association between apremilast and aortic vascular inflammation as assessed by 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), cardiometabolic markers (primary outcomes at week 16), and abdominal fat composition.

Design, Setting, and Participants

A single-arm, open-label, interventional, nonrandomized clinical trial in which the imaging and laboratory outcomes were measured by an investigator who was blinded to time was conducted between April 11, 2017, and August 17, 2021, at 7 dermatology sites in the United States. A total of 101 patients with moderate to severe psoriasis were screened, 70 enrolled, 60 completed week 16, and 39 completed week 52.

Intervention

Apremilast, 30 mg, twice daily.

Main Outcomes and Measures

Aortic vascular inflammation (measured by FDG-PET/CT), 68 cardiometabolic biomarkers, and abdominal fat composition (measured by CT) at week 16 and week 52 compared with baseline.

Results

The mean (SD) age of the 70 patients was 47.5 (14.6) years, 54 were male (77.1%), 4 were Black (5.7%), and 58 were White (82.9%). There was no change in aortic vascular inflammation at week 16 (target to background ratio, -0.02; 95% CI, -0.08 to 0.05; P = .61) or week 52 (target to background ratio, -0.07; 95% CI, -0.15 to 0.01; P = .09) compared with baseline. At week 16, potentially beneficial decreases in interleukin 1b, valine, leucine, isoleucine, fetuin A, and branched-chain amino acids were observed. At week 52 compared with baseline, potentially beneficial decreases in ferritin, β-hydroxybutyrate, acetone, and ketone bodies, with an increase in apolipoprotein A-1, were observed, but there was a reduction in cholesterol efflux. There was an approximately 5% to 6% reduction in subcutaneous and visceral adiposity at week 16 that was maintained at week 52.

Conclusions and Relevance

The findings of this nonrandomized clinical trial suggest that apremilast has a neutral association with aortic vascular inflammation, variable but generally beneficial associations with a subset of cardiometabolic biomarkers, and associations with reductions in visceral and subcutaneous fat, indicating that the drug may have an overall benefit for patients with cardiometabolic disease and psoriasis.

Trial Registration

ClinicalTrials.gov Identifier: NCT03082729.

Relationship between BMI, CT-derived body composition and colorectal neoplasia in a bowel screening population

Introduction

Obesity is associated with an increased risk of colorectal cancer (CRC). Unlike the indirect measures such as BMI, CT-Body composition (CT-BC) allows for the assessment of both volume and distribution of adipose tissue. Therefore, the aim of this study was to examine the relationship between host characteristics, BMI, CT-BC measurements and the incidence of colorectal neoplasia.

Methods

Patients undergoing CT Colonography (CTC) as part of the Scottish Bowel Screening Programme, between July 2009 and February 2016, were eligible for inclusion. Data were collected including demographic data, clinicopathological variables and CT-BC measurements including skeletal muscle index (SMI), subcutaneous fat index (SFI) and visceral fat area (VFA). CTC, colonoscopy, and pathology reports were used to identify CRC incidence. Associations between demographic data, clinicopathological variables, CT-BC measurements, colorectal neoplasia and advanced colorectal neoplasia were analysed using univariate and multivariate binary logistics regression.

Results

286 patients met the inclusion criteria. Neoplasia was detected in 105 (37%) of the patients with advanced neoplasia being detected in 72 (69%) of patients. On multivariate analysis sex (p < 0.05) and high VFA (p < 0.001) remained independently associated with colorectal neoplasia. On multivariate analysis a high SFI (p < 0.01) remained independently associated with advanced colorectal neoplasia. BMI was not associated with either colorectal neoplasia or advanced colorectal neoplasia.

Conclusion

When directly compared to BMI, CT derived fat measurements were more closely associated with the degree of neoplasia in patients undergoing colorectal cancer screening. In patients investigated with CT colonography, CT adipose measures may stratify the risk and grade of neoplasia.

Prognostic implications of visceral obesity on gastric adenocarcinoma: does it really matter?

PURPOSE

To evaluate the association of visceral adiposity measured on computed tomography (CT) in preoperative period with lymph node (LN) metastasis and overall survival in gastric adenocarcinoma patients.

METHODS

Preoperative CT scans of 246 gastric adenocarcinoma patients who did not receive neoadjuvant chemoradiotherapy were evaluated. Visceral fat area (VFA), subcutaneous fat area (SFA) and Total fat area (TFA), VFA/TFA ratio were quantified by CT. VFA/TFA > 29% was defined as visceral obesity. The differentiation, t-stage, n-stage and the number of harvested-metastatic LNs were noted. The maximum thickness of tumor and localization were recorded from CT. Chi-square, Student's t-test, multiple Cox regression, Spearman's correlation coefficient, and Kaplan-Meier algorithm were performed.

RESULTS

The overall survival (OS) rates and N-stage were not different significantly between viscerally obese and non-obese group (p = 0.994, p = 0.325). The number of metastatic LNs were weakly inversely correlated with VFA (r = -0.144, p = 0.024). Univariate analysis revealed no significant association between visceral obesity and OS or LN metastasis (p = 0.377, p = 0.736). In multivariate analyses, OS was significantly associated with poorly differentiation (HR = 1.72, 95% CI =1.04-2.84, p = 0.035), higher pathologic T and N stage (T4 vs T1 + T2 HR = 2.67, 95% CI =1.18-6.04, p = 0.019; T3 vs T1 + T2 HR = 1.98, 95% CI = 0.90-4.33, p = 0.089; N3b vs N0 HR = 2.97, 95% CI1.45-6.0, p = 0.003; N3 (3a+ 3b) vs N0 HR = 2.24 95% CI =1.15-4.36, p = 0.018).

CONCLUSION

Visceral obesity may not be a prognostic factor in resectable gastric adenocarcinoma patients.

Metabolic syndrome and its factors are associated with noncalcified coronary burden in psoriasis: An observational cohort study

BACKGROUND

Psoriasis is associated with a heightened risk of cardiovascular disease and higher prevalence of metabolic syndrome.

OBJECTIVE

Investigate the effect of metabolic syndrome and its factors on early coronary artery disease assessed as noncalcified coronary burden by coronary computed tomography angiography in psoriasis.

METHODS

This cross-sectional study consisted of 260 participants with psoriasis and coronary computed tomography angiography characterization. Metabolic syndrome was defined according to the harmonized International Diabetes Federation criteria.

RESULTS

Of the 260 participants, 80 had metabolic syndrome (31%). The metabolic syndrome group had a higher burden of cardiometabolic disease, systemic inflammation, noncalcified coronary burden, and high-risk coronary plaque. After adjusting for Framingham risk score, lipid-lowering therapy, and biologic use, metabolic syndrome (β = .31; P < .001) and its individual factors of waist circumference (β = .33; P < .001), triglyceride levels (β = .17; P = .005), blood pressure (β = .18; P = .005), and fasting glucose (β = .17; P = .009) were significantly associated with noncalcified coronary burden. After adjusting for all other metabolic syndrome factors, blood pressure and waist circumference remained significantly associated with noncalcified coronary burden.

LIMITATIONS

Observational nature with limited ability to control for confounders.

CONCLUSIONS

In psoriasis, individuals with metabolic syndrome had more cardiovascular disease risk factors, systemic inflammation, and noncalcified coronary burden. Efforts to increase metabolic syndrome awareness in psoriasis should be undertaken to reduce the heightened cardiovascular disease risk.

Chronic inflammation in psoriasis promotes visceral adiposity associated with noncalcified coronary burden over time

BACKGROUND

Psoriasis is a chronic inflammatory skin disease associated with increased obesity, noncalcified coronary artery burden (NCB), and incident myocardial infarction. Here, we sought to assess the relationship among inflammation, visceral adipose tissue (VAT), and NCB. Furthermore, we evaluated whether improvement in VAT would be associated with reduction in NCB over time in psoriasis.

METHODS

Consecutive psoriasis patients underwent coronary CT angiography to quantify NCB and abdominal CT to calculate VAT at baseline (n = 237), 1 year (n = 176), and 4 years (n = 50).

RESULTS

Patients with high levels of high-sensitivity C-reactive protein (hs-CRP) had significantly greater visceral adiposity (17,952.9 ± 849.2 cc³ vs. 13370.7 ± 806.8 cc³, P < 0.001) and noncalcified coronary burden (1.26 ± 0.03 vs. 1.07 ± 0.02 mm²) than those with low levels of hs-CRP. Those with higher levels of VAT had more systemic inflammation (hs-CRP, median [IQR], 2.5 mg/L [1.0–5.3 mg/L] vs. 1.2 mg/L [0.6–2.9 mg/L]), with approximately 50% higher NCB (1.42 ± 0.6 mm² vs. 0.91 ± 0.2 mm², P < 0.001). VAT associated with NCB in fully adjusted models (β = 0.47, P < 0.001). At 1-year follow-up, patients who had worsening hs-CRP had an increase in VAT (14,748.7 ± 878.1 cc³ to 15,158.7 ± 881.5 cc³; P = 0.03), whereas those who had improved hs-CRP improved their VAT (16,876.1 ± 915.2 cc³ to 16310.4 ± 889.6 cc³; P = 0.04). At 1 year, there was 10.3% reduction in NCB in those who had decreased VAT (β = 0.26, P < 0.0001), which persisted in a subset of patients at 4 years (β = 0.39, P = 0.003).

CONCLUSIONS

Inflammation drives development of VAT, increased cardiometabolic risk, and NCB in psoriasis. Reduction of inflammation associated with reduction in VAT and associated with longitudinal improvement in NCB. These findings demonstrate the important role of inflammation in the development of VAT in humans and its effect on early atherogenesis.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01778569.

FUNDING

This study was supported by the National Heart, Lung, and Blood Institute Intramural Research Program (HL006193-05), the NIH Medical Research Scholars Program, a public-private partnership supported jointly by the NIH and contributions to the Foundation for the NIH from the Doris Duke Charitable Foundation (no. 2014194), the American Association for Dental Research, the Colgate-Palmolive Company, Genentech, and Elsevier as well as private donors.

Inflammation is associated with development of visceral adiposity and coronary artery disease in humans.

Technical Note: Automatic segmentation of CT images for ventral body composition analysis

PURPOSE

Body composition is known to be associated with many diseases including diabetes, cancers, and cardiovascular diseases. In this paper, we developed a fully automatic body tissue decomposition procedure to segment three major compartments that are related to body composition analysis - subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and muscle. Three additional compartments - the ventral cavity, lung, and bones - were also segmented during the segmentation process to assist segmentation of the major compartments.

METHODS

A convolutional neural network (CNN) model with densely connected layers was developed to perform ventral cavity segmentation. An image processing workflow was developed to segment the ventral cavity in any patient's computed tomography (CT) using the CNN model, then further segment the body tissue into multiple compartments using hysteresis thresholding followed by morphological operations. It is important to segment ventral cavity firstly to allow accurate separation of compartments with similar Hounsfield unit (HU) inside and outside the ventral cavity.

RESULTS

The ventral cavity segmentation CNN model was trained and tested with manually labeled ventral cavities in 60 CTs. Dice scores (mean ± standard deviation) for ventral cavity segmentation were 0.966 ± 0.012. Tested on CT datasets with intravenous (IV) and oral contrast, the Dice scores were 0.96 ± 0.02, 0.94 ± 0.06, 0.96 ± 0.04, 0.95 ± 0.04, and 0.99 ± 0.01 for bone, VAT, SAT, muscle, and lung, respectively. The respective Dice scores were 0.97 ± 0.02, 0.94 ± 0.07, 0.93 ± 0.06, 0.91 ± 0.04, and 0.99 ± 0.01 for non-contrast CT datasets.

CONCLUSION

A body tissue decomposition procedure was developed to automatically segment multiple compartments of the ventral body. The proposed method enables fully automated quantification of three-dimensional (3D) ventral body composition metrics from CT images.

Technical and Clinical Factors Affecting Success Rate of a Deep Learning Method for Pancreas Segmentation on CT

PURPOSE

Accurate pancreas segmentation has application in surgical planning, assessment of diabetes, and detection and analysis of pancreatic tumors. Factors that affect pancreas segmentation accuracy have not been previously reported. The purpose of this study is to identify technical and clinical factors that adversely affect the accuracy of pancreas segmentation on CT.

METHOD AND MATERIALS

In this IRB and HIPAA compliant study, a deep convolutional neural network was used for pancreas segmentation in a publicly available archive of 82 portal-venous phase abdominal CT scans of 53 men and 29 women. The accuracies of the segmentations were evaluated by the Dice similarity coefficient (DSC). The DSC was then correlated with demographic and clinical data (age, gender, height, weight, body mass index), CT technical factors (image pixel size, slice thickness, presence or absence of oral contrast), and CT imaging findings (volume and attenuation of pancreas, visceral abdominal fat, and CT attenuation of the structures within a 5 mm neighborhood of the pancreas).

RESULTS

The average DSC was 78% ± 8%. Factors that were statistically significantly correlated with DSC included body mass index (r = 0.34, p < 0.01), visceral abdominal fat (r = 0.51, p < 0.0001), volume of the pancreas (r = 0.41, p = 0.001), standard deviation of CT attenuation within the pancreas (r = 0.30, p = 0.01), and median and average CT attenuation in the immediate neighborhood of the pancreas (r = -0.53, p < 0.0001 and r = -0.52, p < 0.0001). There were no significant correlations between the DSC and the height, gender, or mean CT attenuation of the pancreas.

CONCLUSION

Increased visceral abdominal fat and accumulation of fat within or around the pancreas are major factors associated with more accurate segmentation of the pancreas. Potential applications of our findings include assessment of pancreas segmentation difficulty of a particular scan or dataset and identification of methods that work better for more challenging pancreas segmentations.

Fully automated segmentation and quantification of visceral and subcutaneous fat at abdominal CT: application to a longitudinal adult screening cohort

OBJECTIVE

To investigate a fully automated CT-based adiposity tool, applying it to a longitudinal adult screening cohort.

METHODS

A validated automated adipose tissue segmentation algorithm was applied to non-contrast abdominal CT scans in 8852 consecutive asymptomatic adults (mean age, 57.1 years; 3926 M/4926 F) undergoing colonography screening. The tool was also applied to follow-up CT scans in a subset of 1584 individuals undergoing longitudinal surveillance (mean interval, 5.6 years). Visceral and subcutaneous adipose tissue (VAT and SAT) volumes were segmented at levels T12-L5. Primary adipose results are reported herein for the L1 level as mean cross-sectional area. CT-based adipose measurements at initial CT and change over time were analyzed.

RESULTS

Mean VAT values were significantly higher in males (205.8 ± 107.5 vs 108.1 ± 82.4 cm²; p < 0.001), whereas mean SAT values were significantly higher in females (171.3 ± 111.3 vs 124.3 ± 79.7 cm²; p < 0.001). The VAT/SAT ratio at L1 was three times higher in males (1.8 ± 0.7 vs 0.6 ± 0.4; p < 0.001). At longitudinal follow-up CT, mean VAT/SAT ratio change was positive in males, but negative in females. Among the 502 individuals where the VAT/SAT ratio increased at follow-up CT, 333 (66.3%) were males. Half of patients (49.6%; 786/1585) showed an interval increase in both VAT and SAT at follow-up CT.

CONCLUSION

This robust, fully automated CT adiposity tool allows for both individualized and population-based assessment of visceral and subcutaneous abdominal fat. Such data could be automatically derived at abdominal CT regardless of the study indication, potentially allowing for opportunistic cardiovascular risk stratification. Advances in knowledge: The CT-based adiposity tool described herein allows for fully automated measurement of visceral and subcutaneous abdominal fat, which can be used for assessing cardiovascular risk, metabolic syndrome, and for change over time.

Obesity Increases Prevalence of Colonic Adenomas at Screening Colonoscopy: A Canadian Community-Based Study

BACKGROUND AND AIMS

Obesity is a risk factor for colorectal neoplasia. We examined the influence of obesity and metabolic syndrome (MetS) on prevalence of neoplasia at screening colonoscopy.

METHODS

We evaluated 2020 subjects undergoing first screening colonoscopy. Body mass index (BMI) was calculated at enrolment. Hyperlipidemia (HL), hypertension (HT), and diabetes mellitus (DM) were identified. Details of colonoscopy, polypectomy, and histology were recorded. Odds for adenomas (A) and advanced adenomas (ADV) in overweight (BMI 25.1-30) and obese (BMI > 30) subjects were assessed by multinomial regression, adjusted for covariates. Analyses included relationships between HL, HT, DM, age, tobacco usage, and neoplasia. Discriminatory power of HT, HL, DM, and BMI for neoplasia was assessed by binary logistic regression. Odds were calculated for neoplasia in each colonic segment related to BMI.

RESULTS

A and ADV were commoner in overweight and obese males, obese females, older subjects, and smokers. HL, HT, and DM were associated with increased odds for neoplasia, significantly for A with hypertension. BMI alone predicted neoplasia as well as HT, HL, DM, or combinations thereof. All segments of the colon were affected. Multiple polyps were particularly prevalent in the obese.

CONCLUSIONS

Obesity and MetS are risk factors for colonic neoplasia in a Canadian population.

Anthropometry-based Obesity Phenotypes and Risk of Colorectal Adenocarcinoma: A Large Prospective Cohort Study in Norway

BACKGROUND

It is unclear whether obesity phenotypes measured by different anthropometric indices are associated with a risk of colorectal adenocarcinoma by anatomical location.

METHODS

We compiled harmonized population-based cohort studies (Cohort of Norway, CONOR) with 143,477 participants that were conducted between 1994 and 2010. General, abdominal, and gluteofemoral obesity were assessed by body mass index (BMI, kg/m(2)), waist circumference (cm), and hip circumference (cm). Other measures examined were waist to hip ratio, waist to height ratio, and body adiposity index. We performed Cox proportional hazards regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of obesity relative to a risk of colorectal adenocarcinoma.

RESULTS

In total, 2,044 incident cases of colorectal adenocarcinoma were identified. We observed a positive association between waist circumference (high versus low) and adenocarcinoma in the proximal colon (HR = 1.9, 95% CI = 1.5, 2.5) and distal colon (HR = 1.7, 95% CI = 1.3, 2.3) when adjusted for BMI. The association with waist circumference was especially strong in men. BMI was not associated with adenocarcinoma in the colon or rectum after adjusting for waist circumference. We found no association between hip circumference and colorectal adenocarcinoma. When adjusted for BMI plus waist circumference, body adiposity index was negatively associated with adenocarcinoma in the proximal or distal colon.

CONCLUSION

Abdominal obesity, but not general or gluteofemoral obesity, was associated with an increased risk of adenocarcinoma in the proximal and the distal colon, especially in men. Muscularity may be negatively associated with risk of colon adenocarcinoma.

Progress in Fully Automated Abdominal CT Interpretation

OBJECTIVE

Automated analysis of abdominal CT has advanced markedly over just the last few years. Fully automated assessment of organs, lymph nodes, adipose tissue, muscle, bowel, spine, and tumors are some examples where tremendous progress has been made. Computer-aided detection of lesions has also improved dramatically.

CONCLUSION

This article reviews the progress and provides insights into what is in store in the near future for automated analysis for abdominal CT, ultimately leading to fully automated interpretation.

Whole Abdominal Wall Segmentation using Augmented Active Shape Models (AASM) with Multi-Atlas Label Fusion and Level Set

The abdominal wall is an important structure differentiating subcutaneous and visceral compartments and intimately involved with maintaining abdominal structure. Segmentation of the whole abdominal wall on routinely acquired computed tomography (CT) scans remains challenging due to variations and complexities of the wall and surrounding tissues. In this study, we propose a slice-wise augmented active shape model (AASM) approach to robustly segment both the outer and inner surfaces of the abdominal wall. Multi-atlas label fusion (MALF) and level set (LS) techniques are integrated into the traditional ASM framework. The AASM approach globally optimizes the landmark updates in the presence of complicated underlying local anatomical contexts. The proposed approach was validated on 184 axial slices of 20 CT scans. The Hausdorff distance against the manual segmentation was significantly reduced using proposed approach compared to that using ASM, MALF, and LS individually. Our segmentation of the whole abdominal wall enables the subcutaneous and visceral fat measurement, with high correlation to the measurement derived from manual segmentation. This study presents the first generic algorithm that combines ASM, MALF, and LS, and demonstrates practical application for automatically capturing visceral and subcutaneous fat volumes.

Increased risk of colorectal polyps in patients with non-alcoholic fatty liver disease undergoing liver transplant evaluation

BACKGROUND

Screening colonoscopy is a standard part of the liver transplant (LT) evaluation process. We aimed to evaluate the yield of screening colonoscopy and determine whether non-alcoholic fatty liver disease (NAFLD) was associated with an increased risk of colorectal neoplasia.

METHODS

We retrospectively assessed all patients who completed LT evaluation at our center between 1/2008-12/2012. Patients <50 years old and those without records of screening colonoscopy, or with greater than average colon cancer risk were excluded.

RESULTS

A total of 1,102 patients were evaluated, 591 met inclusion criteria and were analyzed. The mean age was 60 years, 67% were male, 12% had NAFLD and 88% had other forms of chronic liver disease. Overall, 42% of patients had a polyp found on colonoscopy: 23% with adenomas, 14% with hyperplastic polyps and with 1% inflammatory polyps. In the final multivariable model controlling for age, NAFLD [odds ratio (OR) 2.41, P=0.001] and a history of significant alcohol use (OR 1.69, P=0.004) were predictive of finding a polyp on colonoscopy. In addition, NAFLD (OR 1.95, P=0.02), significant alcohol use (OR 1.70, P=0.01) and CTP class C (OR 0.57, P=0.02) were associated with adenoma, controlling for age.

CONCLUSIONS

Screening colonoscopy in patients awaiting LT yields a high rate of polyp (43%) and adenoma (22%) detection, perhaps preventing the accelerated progression to carcinoma that can occur in immunosuppressed post-LT patients. Patients with NAFLD may be at a ~2 fold higher risk of adenomas and should be carefully evaluated prior to LT.

Visceral adiposity and colorectal adenomas: dose-response meta-analysis of observational studies

BACKGROUND

Obesity-related hormonal and metabolic perturbations implicated in colorectal carcinogenesis are mainly driven by visceral adipose tissue (VAT) rather than subcutaneous adipose tissue (SAT). Yet, most epidemiologic studies have examined the relationship between excess adiposity and colorectal neoplasia using body mass index (BMI) and waist circumference (WC). Due to the inability of BMI and WC to distinguish VAT from SAT, they are likely to have underestimated the true association.

PATIENTS AND METHODS

We conducted a dose-response meta-analysis to summarize the relationships between VAT and colorectal adenomas and to examine the value of VAT as an independent risk factor beyond BMI, WC, and SAT. PubMed and Embase were searched through September 2014 to identify relevant observational studies. The summary odds ratio (OR) 95% confidence interval (CI) were estimated using a random-effects model.

RESULTS

In linear dose-response meta-analysis, the summary OR for each 25 cm(2) increase in VAT area was 1.13 (95% CI 1.05-1.21; I(2) = 62%; 6 studies; 2776 cases; range of VAT area = 30-228 cm(2)). The dose-response curve suggested no evidence of nonlinearity (Pnon-linearity = 0.37). In meta-analysis comparing the highest versus lowest category of VAT based on 12 studies, a positive association between VAT and adenomas remained statistically significant even after adjustment for BMI, WC, and SAT. In contrast, adjustment for VAT substantially attenuated associations of BMI, WC, and SAT with adenomas. Across the studies, VAT was more strongly associated with advanced adenomas than nonadvanced adenomas.

CONCLUSIONS

VAT may be the underlying mediator of the observed associations of BMI and WC with adenomas, increasing adenoma risk continuously over a wide range of VAT area. Considering that the joint use of BMI and WC better captures VAT than the use of either one, clinicians are recommended to use both BMI and WC to identify those at high risk for colorectal neoplasia.

Associations among pericolonic fat, visceral fat, and colorectal polyps on CT colonography

OBJECTIVE

To determine the association between pericolonic fat and colorectal polyps using CT colonography (CTC).

METHODS

A total of 1169 patients who underwent CTC and optical colonoscopy on the same day were assessed. Pericolonic fat was measured on CTC in a band surrounding the colon. Visceral adipose tissue volume was measured at the L2-L3 levels. Student's t-tests, odds ratio, logistic regression, binomial statistics, and weighted kappa were performed to ascertain associations with the incidence of colorectal polyps.

RESULTS

Pericolonic fat volume fractions (PFVF) were 61.5 ± 11.0% versus 58.1 ± 11.5%, 61.6 ± 11.1% versus 58.7 ± 11.5%, and 62.4 ± 10.6% versus 58.8 ± 11.5% for patients with and without any polyps, adenomatous polyps, and hyperplastic polyps, respectively (P<0.0001). Similar trends were observed when examining visceral fat volume fractions (VFVF). When patients were ordered by quintiles of PFVF or VFVF, there were 2.49-, 2.19-, and 2.39-fold increases in odds ratio for the presence of any polyp, adenomatous polyps, or hyperplastic polyps from the first to the fifth quintile for PFVF and 1.92-, 2.00-, and 1.71-fold increases in odds ratio for VFVF. Polyps tended to occur more commonly in parts of the colon that had more PFVF than the spatially adjusted average for patients in the highest quintile of VFVF.

CONCLUSIONS

Pericolonic fat accumulations, like visceral fat, are correlated with an increased risk of adenomatous and hyperplastic polyps.

Visceral fat quantification in asymptomatic adults using abdominal CT: is it predictive of future cardiac events?

PURPOSE

The purpose of this study was to determine if quantifying visceral adipose tissue (VAT) at CT in asymptomatic adults can predict the likelihood of future cardiac events.

METHODS

Subcutaneous and visceral fat volumes were obtained from abdominal CT utilizing a validated semi-automated software tool in 663 asymptomatic adults (mean age 57.3 years, 379F/284M) undergoing colorectal screening. Patients were followed for subsequent cardiac events, defined as myocardial infarction or coronary intervention for a mean follow-up interval of 7.0 ± 1.4 years. Relevant clinical data including Framingham risk score (FRS) were also collected. Statistical analysis included logistic regression, Pearson correlation coefficients, and Welch and Wilcoxon rank sum tests.

RESULTS

Cardiac events were documented in 32 subjects (4.8%) an average 3.0 years after index CT. FRS was predictive of future cardiac events, signified by a higher score (mean score 11.9 vs. 7.4; p < 0.001). HDL levels were significantly lower in the cardiac event cohort (mean 52.2 vs. 61.0; p < 0.01). None of the other clinical variables were predictive and none of the CT-based fat measurements (visceral, subcutaneous, and total adipose tissue; visceral fat %) correlated with future cardiac events (p = 0.561–0.886). Mean visceral fat % in the cardiac event cohort was 38.1% vs. 39.1% for the non-event group.

CONCLUSION

Quantification of VAT at abdominal CT was not predictive of future cardiac events in this asymptomatic cohort, whereas HDL levels and FRSs correlated well with risk.

Worse cardiometabolic health in African immigrant men than African American men: reconsideration of the healthy immigrant effect

BACKGROUND

The healthy immigrant effect is a phrase that has been used for decades to describe better cardiometabolic health in African immigrants than African Americans. The recent global increase in cardiometabolic diseases raises the possibility that immigrant health may be changing. Therefore, a new assessment of cardiometabolic health in African immigrants is warranted.

METHODS

Glucose tolerance status, blood pressure, and visceral adipose tissue (VAT) volume were compared in 214 self-identified healthy men comprised of 138 African immigrants, 76 African Americans, mean age 36±9 years [mean±standard deviation (SD); range 20-64 years]. Insulin resistance was defined by the lowest quartile of the insulin sensitivity index (SI≤2.28 mU/L(-1)·min(-1)). The waist circumference (WC) which predicts insulin resistance was determined using receiver operating characteristic curves and the Youden index.

RESULTS

Body mass index (BMI) and WC were lower in African immigrants than African Americans (BMI, 27.4±3.8 vs. 29.3±5.5 kg/m(2), P<0.01; WC, 91±11 vs. 97±16 cm, P<0.01). However, blood pressure, fasting glucose, and 2-hr glucose were higher in the African immigrants (all P<0.01). In addition, African immigrants had a higher prevalence of previously undiagnosed diabetes (8% vs. 0%, P<0.01) and prediabetes (35% vs. 22%, P<0.01). After adjusting for WC, African immigrants had more visceral adipose tissue (VAT) than African Americans (P<0.01). Consequently, the WC that predicted insulin resistance was 92 cm in African immigrants but 102 cm in African Americans.

CONCLUSION

African immigrants were less obese than African Americans but had worse cardiometabolic health, specifically higher glucose levels, more hypertension, and greater visceral adiposity. Overall, the healthy immigrant effect may no longer be valid.

Screening colonoscopy in the initial workup of bariatric surgery patients: guidelines are needed

BACKGROUND

Cancer is one of the most common causes of death among morbidly obese individuals. Obese individuals have a well-documented increased risk of colon cancer. No guidelines are available for the workup of bariatric surgery patients in relation to colon cancer.

METHODS

The indications for screening colonoscopy at the Bariatric and Metabolic Institute Abu Dhabi (BMI Abu Dhabi) include all patients older than 50 years [40 years if patients are United Arab Emirates (UAE) nationals] with unexplained abdominal symptoms, anemia of unknown cause, or a family or personal history of colonic pathology. This study retrospectively reviewed the charts of all the patients who had colonoscopy during the period January 2009 to January 2013. The patients were divided into two groups: group A [patients with a body mass index (BMI) > 30 kg/m(2)] and group B (patients with a BMI < 30 kg/m(2)). The demographics and the prevalence of polyps and cancer in the two groups were compared.

RESULTS

During the study period, 341 colonoscopies were performed: 137 for patients with a BMI higher than 30 kg/m(2) (mean age, 44 years) and 204 for patients with a BMI lower than 30 kg/m(2) (mean age, 46 years) (P > 0.05). The overall prevalence of adenomatous polyps was 6.74 % and that of cancer was 1.75 %. Further analysis showed that the prevalences of adenomatous polyps and cancer were respectively 12.4 and 2.1 % for the patients with a BMI higher than 30 kg/m(2), whereas the prevalences were respectively 2.9 and 0.9 % for the patients with BMI lower than 30 kg/m(2) (P < 0.001).

CONCLUSION

The risk for the development of colonic adenomatous polyps and cancer is high among young obese individuals in the Middle East. Guidelines are needed to establish criteria for screening in this group of individuals.

Association between Obesity, Serum Lipids, and Colorectal Polyps in Old Chinese People

Background. Colorectal cancer mostly arises from the polyps of colon. The aim of our study was to examine the association of body mass index (BMI) and serum lipids with the colorectal polyps in old Chinese people. Methods. The risk of developing colorectal polyps was studied in 244 subjects (212 men and 32 women, 74.63 ± 11.63 years old) who underwent colonoscopy for the first time from January 2008 to July 2012 at the Navy General Hospital, Beijing, China. According to the results of colonoscopy, all the subjects were divided into 112 normal control, 38 right colorectal polyps, 53 left colorectal polyps, and 41 both right and left colorectal polyps groups. The total plasma cholesterol, plasma triglyceride, plasma creatinine concentration, blood urinary nitrogen, and fasting glucose were determined using a multichannel analyzer. Results. There were significant differences among normal control, right colorectal polyps, left colorectal polyps, and both right and left polyps groups, which were the BMI, total cholesterol, triglycerides, creatinine, and urinary nitrogen. In binary logistic regression analysis, there were two risk factors associated with the occurrence of colorectal polyps, which included BMI and systolic blood pressure. Conclusions. Colorectal polyps were significantly associated with increased BMI, total cholesterol, and triglycerides levels.

Computed tomographic colonography for colorectal cancer screening: risk factors for the detection of advanced neoplasia

BACKGROUND

The objective of this study was to determine whether age, sex, a positive family history of colorectal cancer, and body mass index (BMI) are important predictors of advanced neoplasia in the setting of screening computed tomographic colonography (CTC).

METHODS

Consecutive patients who were referred for first-time screening CTC from 2004 to 2011 at a single medical center were enrolled. Results at pathology were recorded for all patients who underwent polypectomy. Logistic regression was used to identify significant predictor variables for advanced neoplasia (any adenoma ≥ 10 mm or with villous component, high-grade dysplasia, or adenocarcinoma). Odds ratios (ORs) were used to express associations between the study variables (age, sex, BMI, and a positive family history of colorectal cancer) and advanced neoplasia.

RESULTS

In total, 7620 patients underwent CTC screening. Of these, 276 patients (3.6%; 95% confidence interval [CI], 3.2%-4.1%) ultimately were diagnosed with advanced neoplasia. At multivariate analysis, age (mean OR per 10-year increase, 1.8; 95% CI, 1.6-2.0) and being a man (OR, 1.7; 95% CI, 1.3-2.2) were independent predictors of advanced neoplasia, whereas BMI and a positive family history of colorectal cancer were not. The number needed to screen to detect 1 case of advanced neoplasia varied from 51 among women aged ≤ 55 years to 10 among men aged >65 years. The number of post-CTC colonoscopies needed to detect 1 case of advanced neoplasia varied from 2 to 4.

CONCLUSIONS

Age and sex were identified as important independent predictors of advanced neoplasia risk in individuals undergoing screening CTC, whereas BMI and a positive family history of colorectal cancer were not. These results have implications for appropriate patient selection.