Body composition analysis by radiological imaging - methods, applications, and prospects. / Radiologische Bestimmung der Gewebezusammensetzung im menschlichen Körper (Body Composition) ­ Methoden, Anwendungen und Aussichten.

BACKGROUND: This review discusses the quantitative assessment of tissue composition in the human body (body composition, BC) using radiological methods. Such analyses are gaining importance, in particular, for oncological and metabolic problems. The aim is to present the different methods and definitions in this field to a radiological readership in order to facilitate application and dissemination of BC methods. The main focus is on radiological cross-sectional imaging. METHODS: The review is based on a recent literature search in the US National Library of Medicine catalog (pubmed.gov) using appropriate search terms (body composition, obesity, sarcopenia, osteopenia in conjunction with imaging and radiology, respectively), as well as our own work and experience, particularly with MRI- and CT-based analyses of abdominal fat compartments and muscle groups. RESULTS AND CONCLUSION: Key post-processing methods such as segmentation of tomographic datasets are now well established and used in numerous clinical disciplines, including bariatric surgery. Validated reference values are required for a reliable assessment of radiological measures, such as fatty liver or muscle. Artificial intelligence approaches (deep learning) already enable the automated segmentation of different tissues and compartments so that the extensive datasets can be processed in a time-efficient manner - in the case of so-called opportunistic screening, even retrospectively from diagnostic examinations. The availability of analysis tools and suitable datasets for AI training is considered a limitation. KEY POINTS: · Radiological imaging methods are increasingly used to determine body composition (BC).. · BC parameters are usually quantitative and well reproducible.. · CT image data from routine clinical examinations can be used retrospectively for BC analysis.. · Prospectively, MRI examinations can be used to determine organ-specific BC parameters.. · Automated and in-depth analysis methods (deep learning or radiomics) appear to become important in the future.. CITATION FORMAT: · Linder N, Denecke T, Busse H. Body composition analysis by radiological imaging - methods, applications, and prospects. Fortschr Röntgenstr 2024; DOI: 10.1055/a-2263-1501.

Abdominal fat quantification using convolutional networks.

OBJECTIVES: To present software for automated adipose tissue quantification of abdominal magnetic resonance imaging (MRI) data using fully convolutional networks (FCN) and to evaluate its overall performance-accuracy, reliability, processing effort, and time-in comparison with an interactive reference method. MATERIALS AND METHODS: Single-center data of patients with obesity were analyzed retrospectively with institutional review board approval. Ground truth for subcutaneous (SAT) and visceral adipose tissue (VAT) segmentation was provided by semiautomated region-of-interest (ROI) histogram thresholding of 331 full abdominal image series. Automated analyses were implemented using UNet-based FCN architectures and data augmentation techniques. Cross-validation was performed on hold-out data using standard similarity and error measures. RESULTS: The FCN models reached Dice coefficients of up to 0.954 for SAT and 0.889 for VAT segmentation during cross-validation. Volumetric SAT (VAT) assessment resulted in a Pearson correlation coefficient of 0.999 (0.997), relative bias of 0.7% (0.8%), and standard deviation of 1.2% (3.1%). Intraclass correlation (coefficient of variation) within the same cohort was 0.999 (1.4%) for SAT and 0.996 (3.1%) for VAT. CONCLUSION: The presented methods for automated adipose-tissue quantification showed substantial improvements over common semiautomated approaches (no reader dependence, less effort) and thus provide a promising option for adipose tissue quantification. CLINICAL RELEVANCE STATEMENT: Deep learning techniques will likely enable image-based body composition analyses on a routine basis. The presented fully convolutional network models are well suited for full abdominopelvic adipose tissue quantification in patients with obesity. KEY POINTS: • This work compared the performance of different deep-learning approaches for adipose tissue quantification in patients with obesity. • Supervised deep learning-based methods using fully convolutional networks  were suited best. • Measures of accuracy were equal to or better than the operator-driven approach.

Anthropometric estimators of abdominal fat volume in adults with overweight and obesity.

BACKGROUND/OBJECTIVES: To evaluate anthropometric measures for the prediction of whole-abdominal adipose tissue volumes VXAT (subcutaneous VSAT, visceral VVAT and total VTAT) in patients with obesity. SUBJECTS/METHODS: A total of 181 patients (108 women) with overweight or obesity were analyzed retrospectively. MRI data (1.5 T) were available from independent clinical trials at a single institution (Integrated Research and Treatment Center of Obesity, University of Leipzig). A custom-made software was used for automated tissue segmentation. Anthropometric parameters (AP) were circumferences of the waist (WC) and hip (HC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR) and the (hypothetical) hip-to-height ratio (HHtR). Agreement was evaluated by standard deviations sd% of percent differences between estimated volumes (using results of linear AP-VXAT regression) and measured ones as well as Pearson's correlation coefficient r. RESULTS: For SAT volume estimation, the smallest sd% for all patients was seen for HC (25.1%) closely followed by HHtR (25.2%). Sex-specific results for females (17.5% for BMI and 17.2% for HC) and males (20.7% for WC) agreed better. VAT volumes could not be estimated reliably by any of the anthropometric measures considered here. TAT volumes in a mixed population could be best estimated by BMI closely followed by WC (roughly 17.5%). A sex-specific consideration reduced the deviations to around 16% for females (BMI and WC) and below 14% for males (WC). CONCLUSIONS: We suggest the use of sex-specific parameters-BMI or HC for females and WC for males-for the estimation of abdominal SAT and TAT volumes in patients with overweight or obesity.

Spectrum of qualitative and quantitative imaging of pilomyxoid, intermediate pilomyxoid and pilocytic astrocytomas in relation to their genetic alterations.

PURPOSE: Pilomyxoid astrocytomas (PMA) are pediatric brain tumors predominantly located in the suprasellar region, third ventricle and posterior fossa, which are considered to be more clinically aggressive than pilocytic astrocytomas (PA). Another entity, intermediate pilomyxoid tumors (IPT), exists within the spectrum of pilocytic/pilomyxoid astrocytomas. The 2021 WHO CNS classification refrained from assigning grade 1 or 2 status to PMA, thereby reflecting the need to further elucidate their clinical and imaging characteristics. METHODS: We included a total of 15 patients with PMA, IPT and suprasellar PA. We retrospectively evaluated immunohistochemistry, imaging findings and diffusion characteristics within these tumors as well as whole exome sequencing for three of the cases. RESULTS: 87% of the tumors were supratentorial with 11 cases suprasellar in location, 1 case located in the frontal white matter and 1 in the hippocampus. 6 cases demonstrated intraventricular extension. ADC values were higher in PMA and IPT than PA. 3 cases demonstrated KIAA1549-BRAF-fusion, 2 had BRAF[Formula: see text]-mutation and 6 were BRAF-wildtype. All cases had recurrence/progression on follow-up. CONCLUSION: PMA and IPT do not demonstrate aggressive imaging characteristics in respect to their diffusion imaging with ADC values being higher than PA. Lack of BRAF-alteration in PMA corresponded to atypical location of tumors with atypical driver mutations and mechanisms.

Dickkopf-Related Protein 1 as Response Marker for Transarterial Chemoembolization of Hepatocellular Carcinomas.

Background and Aims: In the treatment of hepatocellular carcinoma (HCC), response prediction to transarterial chemoembolization (TACE) based on serum biomarkers is not established. We have studied the association of circulating Dickkopf-related protein 1 (DKK-1) with baseline characteristics and response to TACE in European HCC patients. Methods: Patients with HCC treated with TACE from 2010 to 2018 at a tertiary referral hospital were retrospectively enrolled. Levels of DKK-1 were measured in serum samples collected before TACE. Response was assessed according to mRECIST criteria at week 12 after TACE. Results: Ninety-seven patients were enrolled, including seventy-nine responders and eighteen refractory. Before TACE, median DKK-1 serum levels were 922 [range, 199−4514] pg/mL. DKK-1 levels were lower in patients with liver cirrhosis (p = 0.002) and showed a strong correlation with total radiologic tumor size (r = 0.593; p < 0.001) and with Barcelona Clinic Liver Cancer stages (p = 0.032). Median DKK-1 levels were significantly higher in refractory patients as compared to responders (1471 pg/mL [range, 546−2492 pg/mL] versus 837 pg/mL [range, 199−4515 pg/mL]; p < 0.001), and DKK-1 could better identify responders than AFP (AUC = 0.798 vs. AUC = 0.679; p < 0.001). A DKK-1 cutoff of ≤1150 pg/mL was defined to identify responders to TACE with a sensitivity of 78% and specificity of 77%. DKK-1 levels were suitable to determine response to TACE in patients with low AFP serum levels (AFP levels < 20 ng/mL; AUC = 0.843; 95% CI [0.721−0.965]; p = 0.003). Conclusion: DKK-1 levels in serum are strongly associated tumor size and with response to TACE in European HCC patients, including those patients with low AFP levels.

High-intensity focused ultrasound (HIFU) hemiablation of the prostate: Late follow-up MRI findings in non-recurrent patients.

OBJECTIVES: Focal therapy with high-intensity focused ultrasound (HIFU) is an emerging option for the treatment of prostate cancer and often followed up by MRI. Image assessment of treatment failure, however, requires proper knowledge about typical procedure-related changes in prostate MRI, which is sparse, in particular for unilateral HIFU treatment and late follow up (beyond 6 months). The goal of this study was therefore to compile the type and frequency of such MRI findings in selected patients without recurrent cancer 12 months after prostate hemiablation. METHODS: Data from a prospective multicenter trial on HIFU hemiablation were reviewed retrospectively. Trial patients have had a late follow-up by MRI (at around 12 months) and either MRI/transrectal ultrasound (TRUS) fusion or standard TRUS-guided biopsy. This work deliberately included patients with non-recurrent cancer in the treated prostate lobe in per-protocol biopsy leaving 30 men with initial International Society of Urological Pathology (ISUP) Grade Group of 1 or 2. Six categories of potential HIFU-related MRI features were assessed by an expert committee and then evaluated by two readers in consensus: 1. shrinkage of the treated lobe, 2. residual prostate tissue, 3. fluid-filled cavity, 4. fibrosis, 5. hematoma residuals (in the prostate or seminal vesicles) and 6. contrast enhancement of the ablated area. RESULTS: Shrinkage of the ablated lobe was seen in 93% of the cases with an average percent volume change of -37% (range: -70% to +108%). In the contralateral lobe, the volume remained practically the same (-2% on average, p = 0.804). In the ablated lobe, the frequency of fibrosis was 97%. Residual prostate tissue was seen in 93% of the cases. The frequency for fluid-filled cavities was 97%, with the wide majority (90%) contiguous with the urethra. Hematoma residuals in the prostate and in seminal vesicles were found in 47% and 10% of the patients, respectively. Contrast enhancement was both rim-like (50%) as well as diffuse (33%) within the ablated area. CONCLUSION: In our case series of HIFU hemiablation in the prostate, shrinkage, residual prostate tissue, fluid-filled cavities contiguous with the urethra and fibrosis were very common late MRI findings of the ablated lobe in non-recurrent patients. Rim-like contrast enhancement or diffuse one within the ablated area were less frequent.

Defective Interfering Genomes and the Full-Length Viral Genome Trigger RIG-I After Infection With Vesicular Stomatitis Virus in a Replication Dependent Manner.

Replication competent vesicular stomatitis virus (VSV) is the basis of a vaccine against Ebola and VSV strains are developed as oncolytic viruses. Both functions depend on the ability of VSV to induce adequate amounts of interferon-α/ß. It is therefore important to understand how VSV triggers interferon responses. VSV activates innate immunity via retinoic acid-inducible gene I (RIG-I), a sensor for viral RNA. Our results show that VSV needs to replicate for a robust interferon response. Analysis of RIG-I-associated RNA identified a copy-back defective-interfering (DI) genome and full-length viral genomes as main trigger of RIG-I. VSV stocks depleted of DI genomes lost most of their interferon-stimulating activity. The remaining full-length genome and leader-N-read-through sequences, however, still triggered RIG-I. Awareness for DI genomes as trigger of innate immune responses will help to standardize DI genome content and to purposefully deplete or use DI genomes as natural adjuvants in VSV-based therapeutics.

Effects of Hyperthyroidism on Adipose Tissue Activity and Distribution in Adults.

Background: Positron emission tomography (PET) has provided evidence that adult humans retain metabolically active brown adipose tissue (BAT) depots. Thyroid hormones (TH) stimulate BAT thermogenesis by central and peripheral mechanisms. However, the effect of hyperthyroidism on BAT activity and BAT volume in humans is yet not fully understood. The aim of this study was to investigate the effect of TH on (i) the metabolic activity of brown and white adipose tissue (WAT) depots, (ii) on abdominal visceral and subcutaneous adipose tissue area, and (iii) on serum levels of metabolically active cytokines. Methods: Nineteen patients with overt hyperthyroidism were investigated through repeated 2-[18F]fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography (2-[18F]FDG PET/CT) in the hyperthyroid and in the euthyroid state. The 2-[18F]FDG uptake was calculated as standard uptake ratio with blood pool as reference. Fat areas were quantified by means of CT segmentation. Serum levels of fetuin A and B, fibroblast growth factor 21, adipocyte fatty acid-binding protein (AFABP), retinol-binding protein 4, pro-enkephalin, pro-neurotensin, and neuregulin 4 were determined in the hyperthyroid and in the euthyroid state for each subject. Results: 2-[18F]FDG uptake was increased in the hyperthyroid state in BAT in comparison with the euthyroid phase (p = 0.001). There was no correlation between serum free triiodothyronine (fT3) and free thyroxine (fT4) levels and 2-[18F]FDG uptake in BAT or WAT. In the hyperthyroid state, fT3 levels were positively associated with skeletal muscle standardized uptake value ratios. Areas of visceral adipose tissue and skeletal muscle were significantly decreased in hyperthyroidism. AFABP levels correlated positively with fT3 (p = 0.031, ß = 0.28) and fT4 (p = 0.037, ß = 0.27) in the hyperthyroid state. Conclusions: Our results suggest that the contribution of increased TH levels to the glucose uptake of BAT and WAT is low compared with that of the skeletal muscle. Hyperthyroid subjects have reduced areas of visceral adipose tissue and increased AFABP levels.

Toward a Routine Assessment of Visceral Adipose Tissue Volume from Computed Tomographic Data.

OBJECTIVE: The study's aim was to determine to what extent total visceral adipose tissue (VAT) volume (VVAT-T ) measured from segmented VAT areas (AVAT ) on all axial computed tomography (CT) sections (thickness of 5 mm) between the diaphragm and pelvic floor can be predicted by the AVAT of commonly selected landmark sections in patients with overweight or obesity. METHODS: A total of 113 patients (31 females, 82 males) with images of full abdominopelvic coverage and proper image quality were included (BMI = 25.0-64.1 kg/m2 , 29.5 ± 4.9 kg/m2 ). Linear regression between AVAT and VVAT-T (reference) was used to determine approximate equations for VAT volume for all parameters (single sex, different anatomical landmarks or lumbar intervertebral disc spaces, one or five axial sections). Agreement was evaluated by the multivariate coefficient of determination and by the SD of the percentage difference (sd% ) between the estimated VAT volume on one or five sections and VVAT-T . RESULTS: The VVAT-T was 0.9 to 8.4 (3.8 ± 2.2) L for females and 2.7 to 11.7 (5.6 ± 2.1) L for males. Best agreement was found at L2-3 (sd% = 14.3%-15.5%) for females and at L1-2 or L2-3 (11.7%-12.4%) for males. Agreement at the umbilicus or the femoral heads was poor (20.2%-57.9%). Segmentation of one or five sections was substantially faster (11/70 seconds) than whole-abdomen processing (15 minutes). CONCLUSIONS: VVAT-T can be rapidly estimated by VAT segmentation of axial CT sections at sex-specific lumbar intervertebral disc spaces.

Abdominal subcutaneous fat quantification in obese patients from limited field-of-view MRI data.

Different types of adipose tissue can be accurately localized and quantified by tomographic imaging techniques (MRI or CT). One common shortcoming for the abdominal subcutaneous adipose tissue (ASAT) of obese subjects is the technically restricted imaging field of view (FOV). This work derives equations for the conversion between six surrogate measures and fully segmented ASAT volume and discusses the predictive power of these image-based quantities. Clinical (gender, age, anthropometry) and MRI data (1.5 T, two-point Dixon sequence) of 193 overweight and obese patients (116 female, 77 male) from a single research center for obesity were analyzed retrospectively. Six surrogate measures of fully segmented ASAT volume (VASAT) were considered: two simple ASAT lengths, two partial areas (Ap-FH, Ap-ASIS) and two partial volumes (Vp-FH, Vp-ASIS) limited by either the femoral heads (FH) or the anterior superior iliac spine (ASIS). Least-squares regression between each measure and VASAT provided slope and intercept for the computation of estimated ASAT volumes (V~ASAT). Goodness of fit was evaluated by coefficient of determination (R2) and standard deviation of percent differences (sd%) between V~ASAT and VASAT. Best agreement was observed for partial volume Vp-FH (sd% = 14.4% and R2 = 0.78), followed by Vp-ASIS (sd% = 18.1% and R2 = 0.69) and AWFASIS (sd% = 23.9% and R2 = 0.54), with minor gender differences only. Other estimates from simple lengths and partial areas were moderate only (sd% > 23.0% and R2 < 0.50). Gender differences in R2 generally ranged between 0.02 (dven) and 0.29 (Ap-FH). The common FOV restriction for MRI volumetry of ASAT in obese subjects can best be overcome by estimating VASAT from Vp-FH using the equation derived here. The very simple AWFASIS can be used with reservation.

Estimation of abdominal subcutaneous fat volume of obese adults from single-slice MRI data - Regression coefficients and agreement.

PURPOSE: Cross-sectional imaging is increasingly used to quantify adipose tissue compartments in subjects with overweight or obesity. The lack of ionizing radiation makes magnetic resonance imaging (MRI) highly preferable to computed tomography (CT) although it is generally less standardized and time-consuming. Fat areas of single or stacks of neighboring slices have previously been considered as surrogates to avoid laborious processing of whole abdominal data-but studies are inconsistent in design and results. The present work therefore analyzed a relatively large number of overweight or obese adults and involved a total of eight landmarks and two surrogates (slice and stack). The goals were to identify the most reliable estimators of abdominal subcutaneous adipose tissue (ASAT) volume for both genders and to relate the findings to the pertinent literature. MATERIAL AND METHODS: Anthropometric and fat-sensitive 1.5 T MRI data of 193 patients (116 female, 77 male) from different IRB-approved studies at a single clinical research institution (IFB Adiposity Diseases, University Medicine Leipzig, Germany) were analyzed retrospectively. Mean (± SD) age and BMI were 51.5 (± 12.4) years and 33.7 (± 3.9) kg/m2 for females versus 57.6 (± 12.4) years and 32.1 (± 3.7) kg/m2 for males. Areas of selected axial slices (10 mm thick, 0.5 mm gap) and of stacks of five slices at common landmarks - intervertebral disc spaces L1/L2 to L5/S1, anterior superior iliac spine (ASIS), femoral head (FH) and umbilicus (UM) - were considered as estimators for ASAT volume (reference). Agreement between simple areas and reference volumes was asssessed by linear regression (coefficient of determination R2) as well as standard deviations of percent differences sd% between estimated and measured volumes. RESULTS: ASAT volumes ranged from 6.61 to 21.94 L for females (mean: 13.37 L) and from 5.42 to 17.90 L (mean: 9.89 L) for males. The smallest sd% (8.4 %-10.1 %) and largest R2 values (0.86-0.92) for single slices were observed for three candidate slice positions that were also associated with the highest ASAT volume fraction: L4/L5, L5/S1 and UM. The stack estimates for these landmarks were overall somewhat better (7.3 %-9.7 %, 0.88-0.94, respectively). The differences in sd% between genders ranged between 0.2 % and 1.1 %. CONCLUSION: ASAT volume in overweight or obese patients can be readily estimated with good accuracy from a single MRI slice centered at intervertebral disc space L5/S1 for both genders. Disc space L4/L5 or the umbilicus are nearly equivalent landmarks, in particular for male subjects. The extension to stack measures may yield too little improvement to justify the extra effort. Landmarks like ASIS, FH or the remaining lumbar disc spaces are considered as unreliable.

Identification of distinct transcriptome signatures of human adipose tissue from fifteen depots.

The functional and metabolic characteristics of specific adipose tissue (AT) depots seem to be determined by intrinsic mechanisms. We performed a comprehensive transcriptome profiling of human AT from distinct fat depots to unravel their unique features potentially explaining molecular mechanisms underlying AT distribution and their contribution to health and disease. Post-mortem AT samples of five body donors from 15 anatomical locations were collected. Global mRNA expression was measured by Illumina® Human HT-12 v4 Expression BeadChips. Data were validated using qPCR and Western Blot in a subset of ATs from seven additional body donors. Buccal and heel AT clearly separated from the "classical" subcutaneous AT depots, and perirenal and epicardial AT were distinct from visceral depots. Gene-set enrichment analyses pointed to an inflammatory environment and insulin resistance particularly in the carotid sheath AT depot. Moreover, the epicardial fat transcriptome was enriched for genes involved in extracellular matrix remodeling, inflammation, immune signaling, coagulation, thrombosis, beigeing, and apoptosis. Interestingly, a striking downregulation of the expression of leptin receptor was found in AT from heel compared with all other AT depots. The distinct gene expression patterns are likely to define fat depot specific AT functions in metabolism, energy storage, immunity, body insulation or as cushions. Improved knowledge of the gene expression profiles of various fat depots may strongly benefit studies aimed at better understanding of the genetics and the pathophysiology of obesity and adverse body fat composition.

Prognostic role of body composition parameters in gastric/gastroesophageal junction cancer patients from the EXPAND trial.

BACKGROUND: Body fat and/or muscle composition influences prognosis in several cancer types. For advanced gastric and gastroesophageal junction cancer, we investigated which body composition parameters carry prognostic information beyond well-established clinical parameters using robust model selection strategy such that parameters identified can be expected to generalize and to be reproducible beyond our particular data set. Then we modelled how differences in these parameters translate into survival outcomes. METHODS: Fat and muscle parameters were measured on baseline computed tomography scans in 761 patients with advanced gastric or gastroesophageal junction cancer from the phase III EXPAND trial, undergoing first-line chemotherapy. Cox regression analysis for overall survival (OS) and progression-free survival (PFS) included body composition parameters and clinical prognostic factors. All continuous variables were entered linearly into the model as there was no evidence of non-linear prognostic impact. For transferability, the final model included only parameters that were picked by Bayesian information criterion model selection followed by bootstrap analysis to identify the most robust model. RESULTS: Muscle and fat parameters formed correlation clusters without relevant between-cluster correlation. Mean muscle attenuation (MA) clusters with the fat parameters. In multivariate analysis, MA was prognostic for OS (P < 0.0001) but not for PFS, while skeletal muscle index was prognostic for PFS (P = 0.02) but not for OS. Worse performance status Eastern Cooperative Oncology Group (ECOG 1/0), younger age (on a linear scale), and the number of metastatic sites were strong negative clinical prognostic factors for both OS and PFS. MA remained in the model for OS (P = 0.0001) following Bayesian information criterion model selection in contrast to skeletal muscle index that remained prognostic for PFS (P = 0.009). Applying stricter criteria for transferability, MA represented the only prognostic body composition parameter for OS, selected in >80% of bootstrap replicates. Finally, Cox model-derived survival curves indicated that large differences in MA translate into only moderate differences in expected OS in this cohort. CONCLUSIONS: Among body composition parameters, only MA has robust prognostic impact for OS. Data suggest that treatment approaches targeting muscle quality are unlikely to prolong OS noticeably on their own in advanced gastric cancer patients, indicating that multimodal approaches should be pursued in the future.

Mean muscle attenuation correlates with severe acute pancreatitis unlike visceral adipose tissue and subcutaneous adipose tissue.

Background: Acute pancreatitis (AP) is a frequent disorder with considerable morbidity and mortality. Obesity has previously been reported to influence disease severity. Objective: The aim of this study was to investigate the association of adipose and muscle parameters with the severity grade of AP. Methods: In total 454 patients were recruited. The first contrast-enhanced computed tomography of each patient was reviewed for adipose and muscle tissue parameters at L3 level. Associations with disease severity were analysed through logistic regression analysis. The predictive capacity of the parameters was investigated using receiver operating characteristic (ROC) curves. Results: No distinct variation was found between the AP severity groups in either adipose tissue parameters (visceral adipose tissue and subcutaneous adipose tissue) or visceral muscle ratio. However, muscle mass and mean muscle attenuation differed significantly with p-values of 0.037 and 0.003 respectively. In multivariate analysis, low muscle attenuation was associated with severe AP with an odds ratio of 4.09 (95% confidence intervals: 1.61-10.36, p-value 0.003). No body parameter presented sufficient predictive capability in ROC-curve analysis. Conclusions: Our results demonstrate that a low muscle attenuation level is associated with an increased risk of severe AP. Future prospective studies will help identify the underlying mechanisms and characterise the influence of body composition parameters on AP.

Half-body MRI volumetry of abdominal adipose tissue in patients with obesity.

BACKGROUND: The purpose of this study was to determine to what extent the whole volumes of abdominal subcutaneous (ASAT) and visceral adipose tissue (VAT) of patients with obesity can be predicted by using data of one body half only. Such a workaround has already been reported for dual-energy x-ray absorption (DEXA) scans and becomes feasible whenever the field of view of an imaging technique is not large enough. METHODS: Full-body abdominal MRI data of 26 patients from an obesity treatment center (13 females and 13 males, BMI range 30.8-41.2 kg/m2, 32.6-61.5 years old) were used as reference (REF). MRI was performed with IRB approval on a clinical 1.5 T MRI (Achieva dStream, Philips Healthcare, Best, Netherlands). Segmentation of adipose tissue was performed with a custom-made Matlab software tool. Statistical measures of agreement were the coefficient of determination R2 of a linear fit. RESULTS: Mean ASATREF was 12,976 (7812-24,161) cm3 and mean VATREF was 4068 (1137-7518) cm3. Mean half-body volumes relative to the whole-body values were 50.8% (48.2-53.7%) for ASATL and 49.2% (46.3-51.8%) for ASATR. Corresponding volume fractions were 56.4% (51.4-65.9%) for VATL and 43.6% (34.1-48.6%) for VATR. Correlations of ASATREF with ASATL as well as with ASATR were both excellent (R2 > 0.99, p < 0.01). Corresponding correlations of VATREF were marginally lower (R2 = 0.98 for VATL, p < 0.01, and R2 = 0.97 for VATR, p < 0.01). CONCLUSIONS: In conclusion, abdominal fat volumes can be reliably assessed by half-body MRI data, in particular the subcutaneous fat compartment.

Comparison of PI-RADS v1 and v2 for multiparametric MRI detection of prostate cancer with whole-mount histological workup as reference standard.

PURPOSE: The aim of this study was to compare Prostate Imaging Reporting and Data System (PI-RADS) versions v1 and v2 for the detection of prostate cancer (PCa) in multiparametric MRI (mpMRI) using whole-mount histological workup as reference standard. MATERIAL AND METHODS: MRI data of 40 patients with positive transrectal ultrasound-guided biopsy were analyzed retrospectively by two blinded readers (5 and 4 years' experience) with PI-RADS v1 and v2 for cancer-suspicious lesions. Prior to radical prostatectomy, patients had undergone IRB-approved mpMRI at 3 T according to PI-RADS recommendations: T2-weighted (T2w), diffusion-weighted (DWI) and dynamic contrast-enhanced (DCE) imaging. The reference standard was provided by whole-mount sections of the prostatectomy specimens. Versions v1 and v2 were compared with respect to sensitivity and positive predictive value (PPV) per lesion. Subgroups stratified by tumor location (peripheral vs. transition zone) and aggressiveness (high vs. low grade) were also analyzed. We also evaluated the concordance of the dominant MRI sequence in v2 (DWI or T2w) and the highest individual score under v1. Interobserver agreement for PI-RADS v1 and v2 was assessed by Cohen's kappa statistics. RESULTS: Reader 1 (R1) described 66 and Reader 2 (R2) 72 MRI lesions. The average Gleason score of 58 PCa lesions was 6.5 (range: 6 = 3 + 3 to 8 = 4 + 4), most of them (65.5%) located in the peripheral zone. PI-RADS v2 showed a trend towards lower sensitivities, but differences were not significant for both readers: R1 72.4% (v1) vs. 63.8% (v2) (P = 0.426) and R2 77.6% (v1) vs. 69.0% (v2) (P = 0.402). The trends were more pronounced in the transition zone and for low-grade cancers but remained insignificant (p-values from 0.313 to 0.691). Likewise, the apparent PPV differences, overall as well as in each zone, were not significant. Agreement between high-score v1 and dominant v2 sequence was 48% for R1 and 53% for R2. Cohen's κ of PCa detection for two readers was 0.48 for both v1 and v2. CONCLUSION: Our findings indicate that the simplified, zone-specific approach of PI-RADS v2 (2015) for MRI assessment of prostate cancer may not necessarily be better than the original v1 criteria (2012). In specific cases, a strict interpretation of v2 criteria may even lead to false-negative findings. Therefore, the current PI-RADS criteria should be reconsidered, despite the low statistical evidence here.

In-bore biopsies of the prostate assisted by a remote-controlled manipulator at 1.5 T.

PURPOSE: To evaluate the technical and clinical utility of a fully MRI-compatible, pneumatically driven remote-controlled manipulator (RCM) for targeted biopsies of the prostate at 1.5 T. MATERIALS AND METHODS: The data of the first 22 patients that were biopsied under robotic assistance were analyzed. Interventional planning relied on T2-weighted (T2w) turbo spin-echo (TSE) images (axial and sagittal) with a high-b-value diffusion-weighted acquisition added in selected cases. Alignment of the needle guide was controlled with a short balanced SSFP sequence in two oblique planes along the MR-visible sheath. Signals were acquired with a combination of elements from a 30-channel body and a 32-channel spine coil. Biopsy samples were taken with a fully automatic 18-G biopsy gun with a length of 150 or 175 mm. RESULTS: Mean age was 66.6 years and average PSA level was 11.5 ng/ml. Fourteen out of 22 patients (63%) had received prior biopsies under transrectal ultrasound guidance. Diagnostic MRI reports (before biopsy) involved 17 cases with a single suspicious finding (four PI-RADS 3, one PI-RADS 3-4, eight PI-RADS 4 and nine PI-RADS 5 cases). The median effective procedure time was 33.9 (range 25.0-55.9) min for 16 cases with one CSR and 63.4 (52.7-81.8) min for 5 cases with two CSRs. The biopsy with three CSRs took 74.0 min. Histopathologic examination revealed prostate cancer in 14 of 22 cases. CONCLUSION: MR-targeted, transrectal biopsy of the prostate could be reliably performed with a robotic manipulator at a field strength of 1.5 T. Balanced SSFP imaging is considered a viable option for fast procedural control. Follow-up work needs to evaluate to what extent in-bore adjustments and workflow enhancements will contribute to shorter procedure times or higher patient comfort.

Power of computed-tomography-defined sarcopenia for prediction of morbidity after pancreaticoduodenectomy.

BACKGROUND: The goal of our study was to evaluate the current approach in prediction of postoperative major complications after pancreaticoduodenectomy (PD), especially symptomatic pancreatic fistula (POPF), using parameters derived from computed tomography (CT). METHODS: Patients after PD were prospectively collected in a database of the local department of surgery and all patients with CT scans available were assessed in this study. CT parameters were measured at the level of the intervertebral disc L3/L4 and consisted of the areas of the visceral adipose tissue (AVAT), the diameters of the pancreatic parenchyma (DPP) and the pancreatic duct (DPD), the areas of ventral abdominal wall muscle (AMVEN), psoas muscle (AMPSO), paraspinal muscle (AMSPI), total muscle (AMTOT), as well as the mean muscle attenuation (MA) and skeletal muscle index (SMI). Mann-Whitney-U Test for two independent samples and binary logistic regression were used for statistical analysis. RESULTS: One hundred thirty-nine patients (55 females, 84 males) were included. DPD was 2.9 mm (Range 0.7-10.7) on median and more narrow in patients with complications equal to or greater stadium IIIb (p < 0.04) and severe POPF (p < 0.01). DPP median value was 17 (6.9-37.9) mm and there was no significant difference regarding major complications or POPF. AVAT showed a median value of 127.5 (14.5-473.0) cm2 and was significantly larger in patients with POPF (p < 0.01), but not in cases of major complications (p < 0.06). AMPSO, AMSPI, AMVEN and AMTOT showed no significant differences between major complications and POPF. MA was both lower in groups with major complications (p < 0.01) and POPF (p < 0.01). SMI failed to differentiate between patients with or without major complications or POPF. CONCLUSION: Besides the known factors visceral obesity and narrowness of the pancreatic duct, the mean muscle attenuation can easily be examined on routine preoperative CT scans and seems to be promising parameter to predict postoperative complications and POPF.

MRI assessment of changes in adipose tissue parameters after bariatric surgery.

Bariatric surgery and other therapeutic options for obese patients are often evaluated by the loss of weight, reduction of comorbidities or improved quality of life. However, little is currently known about potential therapy-related changes in the adipose tissue of obese patients. The aim of this study was therefore to quantify fat fraction (FF) and T1 relaxation time by magnetic resonance imaging (MRI) after Roux-en-Y gastric bypass surgery and compare the resulting values with the preoperative ones. Corresponding MRI data were available from 23 patients (16 females and 7 males) that had undergone MRI before (M0) and one month after (M1) bariatric surgery. Patients were 22-59 years old (mean age 44.3 years) and their BMI ranged from 35.7-54.6 kg/m2 (mean BMI 44.6 kg/m2) at M0. Total visceral AT volumes (VVAT-T, in L) were measured by semi-automatic segmentation of axial MRI images acquired between diaphragm and femoral heads. MRI FF and T1 relaxation times were measured in well-defined regions of visceral (VAT) and subcutaneous (SAT) adipose tissue using two custom-made analysis tools. Average BMI values were 45.4 kg/m2 at time point M0 and 42.4 kg/m2 at M1. Corresponding VVAT-T values were 5.94 L and 5.33 L. Intraindividual differences in both BMI and VVAT-T were highly significant (p<0.001). Average relaxation times T1VAT were 303.7 ms at M0 and 316.9 ms at M1 (p<0.001). Corresponding T1SAT times were 283.2 ms and 280.7 ms (p = 0.137). Similarly, FFVAT differences (M0: 85.7%, M1: 83.4%) were significant (p <0.01) whereas FFSAT differences (M0: 86.1, M1: 85.9%) were not significant (p = 0.517). In conclusion, bariatric surgery is apparently not only related to a significant reduction in common parameters of adipose tissue distribution, here BMI and total visceral fat volume, but also significant changes in T1 relaxation time and fat fraction of visceral adipose tissue. Such quantitative MRI measures may potentially serve as independent biomarkers for longitudinal and cross-sectional measurements in obese patients.