Body composition measures were assessed by centrally trained researchers from CT scans obtained during routine clinical care, using the scan that was taken within six months and nearest to diagnosis, and prior to chemotherapy or radiation treatment (median: 1.2 months, range: ±5.9 months). Our analysis did not include stage I patients because they do not routinely receive CT scans, and thus those who did might be a non-representative sample of those patients. From the CT scan, we measured body composition at the third lumbar vertebra (L3), and calculated cross-sectional area in centimeters squared (cm2) of adipose tissue (SAT, VAT) and skeletal muscle index (SMI, cm2 from rectus abdominus, erector spinae muscles, quadratus lumborum, psoas, and internal, transverse and external oblique muscle groups divided by height in m2) by tissue-specific Hounsfield Unit ranges using SliceOmatic Software version 5.0 (TomoVision, Montreal, Quebec, Canada).18 These quantities have been previously shown to be valid proxies for whole body volumes of muscle and adipose tissue.19 (link) The coefficients of variation (CV%) for 30 images randomly selected and colored by both readers were 0.79 and 6.72, and 0.66, for SAT, VAT, and SMI, respectively.
Sliceomatic software version 5
Manufactured by Tomovision
Sourced in Canada
SliceOmatic Software version 5.0 is a lab equipment product designed for image processing and analysis. It provides core functionalities for visualizing, segmenting, and quantifying 2D and 3D images. The software supports a variety of file formats and enables users to perform essential image processing tasks.
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Lab products found in correlation
12 protocols using sliceomatic software version 5
1
Body Composition Assessment from CT Scans
2
Abdominal Tissue Segmentation Using CT
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As part of the SCANS studies, two centrally trained researchers using SliceOmatic Software version 5.0 (TomoVision, Montreal, Quebec, Canada) selected a single slice at L3 and segmented the cross‐sectional area in centimetres squared (cm2) of each tissue area, distinguishing muscle and visceral from subcutaneous adipose tissues using anatomic knowledge and tissue‐specific Hounsfield Units (HU) ranges: −29 to 150 for skeletal muscle, −190 to −30 for subcutaneous and inter‐muscular adipose, and −150 to −50 for visceral adipose. Each CT scan was manually segmented following the Alberta protocol.20 The first segmentation was used as the reference in this analysis. In inter‐rater reliability analysis in a subset of 50 scans, coefficients of variation (CV%) were 1.2%, 2.7%, 1.1%, and 9.0% for muscle and subcutaneous, visceral, and inter‐muscular adipose tissues between the two human raters, respectively.
Of note, a limitation of ABACS is that the algorithm for inter‐muscular adipose tissue segmentation is still in beta‐testing. By default, ABACS treats inter‐muscular adipose tissue (adipose tissue deposits within skeletal muscle) as subcutaneous adipose tissue. Thus, for comparability, we combined the manual labels for subcutaneous and inter‐muscular adipose tissue in this study; this combined tissue area is henceforth referred to as subcutaneous adipose tissue.
Of note, a limitation of ABACS is that the algorithm for inter‐muscular adipose tissue segmentation is still in beta‐testing. By default, ABACS treats inter‐muscular adipose tissue (adipose tissue deposits within skeletal muscle) as subcutaneous adipose tissue. Thus, for comparability, we combined the manual labels for subcutaneous and inter‐muscular adipose tissue in this study; this combined tissue area is henceforth referred to as subcutaneous adipose tissue.
3
Quantifying Sarcopenia Using CT Imaging
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The cross-sectional areas of lumbar skeletal muscles at the third lumbar vertebra (L3) level were analyzed using electronically stored CT images. LBM and SMI were analyzed using slice-O-matic software version 5.0 (Tomovision, Montreal, Canada) and calculated based on the equations provided by Mourtzakis et al. [35 (link)] as reported in detail in the Supplementary file (Methods S1) .
The SMI cut-off values used for the definition of sarcopenia were set at <55 cm2/m2 and <39 cm2/m2 for men and women, respectively, according to the international consensus for the definition of cancer cachexia [18 (link)].
The SMI cut-off values used for the definition of sarcopenia were set at <55 cm2/m2 and <39 cm2/m2 for men and women, respectively, according to the international consensus for the definition of cancer cachexia [18 (link)].
4
Quantifying Muscle Mass Using CT Scans
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As part of the C‐SCANS study, muscle was quantified using standard analysis from an axial CT scan that had been taken before chemotherapy or radiation, if received, and archived within the electronic medical record. The median time from diagnosis to scan in this study sample was 6 days (range: −2 to 4 months; 79% pre‐surgical). A single, trained researcher with anatomical knowledge selected the L3 and analysed the total cross‐sectional area of muscle in centimetres squared (cm2) according to tissue‐specific Hounsfield units ranges using Slice‐O‐Matic Software version 5.0 (Tomovision, Quebec, Canada).31 We computed the skeletal muscle index as the total cross‐sectional area in centimetres squared scaled to height in metres squared. Figure 1 A shows the CT scans of an example patient in this cohort with the total cross‐sectional muscle area analysed using standard analysis implemented in Slice‐O‐Matic.
5
Quantifying Muscle and Adipose Tissue from CT
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In a first step, centrally trained researchers assessed the quality of the original Digital Imaging and Communications in Medicine (DICOM) images at level T12 and L3. In a second step, the research assistants evaluated the CT scans and selected a single slice at level T12. For this purpose, we used SliceOmatic Software version 5.0 (TomoVision, Montreal, Quebec, QC, Canada). We excluded all images with incomplete depiction of T12 and in case that the muscle tissue was out of range and/or if contrast did not allow discrimination. There were no anatomical variations that led to exclusion.
Muscle and visceral tissue were distinguished from subcutaneous adipose tissue using tissue-specific Hounsfield Unit (HU) ranges and anatomical knowledge. We followed the Alberta protocol [23 (link)] and set Hounsfield ranges to −29 to 150 HU for skeletal muscle, −190 to −30 HU for subcutaneous and intramuscular adipose tissue, and −150 to −50 HU for visceral adipose tissue. Muscles included in the cross-sectional measurements at T12 with different muscle groups, including the erector spinae, latissimus dorsi, external and internal oblique, rectus abdominis and external and internal intercostal muscles. Every slice was evaluated twice to improve the interrater reliability with the aim to achieve >99%. Researchers improved the slicing and measuring criteria after the first round.
Muscle and visceral tissue were distinguished from subcutaneous adipose tissue using tissue-specific Hounsfield Unit (HU) ranges and anatomical knowledge. We followed the Alberta protocol [23 (link)] and set Hounsfield ranges to −29 to 150 HU for skeletal muscle, −190 to −30 HU for subcutaneous and intramuscular adipose tissue, and −150 to −50 HU for visceral adipose tissue. Muscles included in the cross-sectional measurements at T12 with different muscle groups, including the erector spinae, latissimus dorsi, external and internal oblique, rectus abdominis and external and internal intercostal muscles. Every slice was evaluated twice to improve the interrater reliability with the aim to achieve >99%. Researchers improved the slicing and measuring criteria after the first round.
6
Abdominal CT Scans for Body Composition
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Abdominal CT scans routinely performed at diagnosis were used to assess body composition. These CT scans were analyzed by trained researchers following standardized procedures. Skeletal muscle, VAT, and SAT cross-sectional areas were quantified on CT images at the level of the 3rd lumbar vertebrae with the use of Slice-O-Matic software version 5.0 (Tomovision, Montreal, Canada). To identify the different tissues, standard density thresholds, measured in Hounsfield units (HU) were used.
The standard density threshold for skeletal muscle mass was − 29 to 150 HU, for VAT − 150 to − 50 HU, and for SAT and intermuscular adipose tissue (IMAT) − 190 and − 30 HU. Total adipose tissue (TAT) (cm2) was calculated as the sum of VAT, SAT, and IMAT (cm2). SMD was assessed as the mean radiographic density (HU) of the total skeletal muscle cross-sectional area. To adjust for height, the skeletal muscle mass index (SMI) (cm2/m2) was calculated by dividing the skeletal muscle cross-sectional area (cm2) by squared height (m2). Body mass index (BMI) (kg/m2) was calculated by dividing body weight (kg) by squared height (m2). Body height and weight were self-reported.
The standard density threshold for skeletal muscle mass was − 29 to 150 HU, for VAT − 150 to − 50 HU, and for SAT and intermuscular adipose tissue (IMAT) − 190 and − 30 HU. Total adipose tissue (TAT) (cm2) was calculated as the sum of VAT, SAT, and IMAT (cm2). SMD was assessed as the mean radiographic density (HU) of the total skeletal muscle cross-sectional area. To adjust for height, the skeletal muscle mass index (SMI) (cm2/m2) was calculated by dividing the skeletal muscle cross-sectional area (cm2) by squared height (m2). Body mass index (BMI) (kg/m2) was calculated by dividing body weight (kg) by squared height (m2). Body height and weight were self-reported.
7
Quantifying Adipose Tissue Radiodensity from CT Scans
8
Body Composition Assessment from CT Scans
9
CT-Based Body Composition Analysis in Cancer
10
Quantifying Muscle and Adipose Tissue
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The area and radiodensity of muscle and adipose tissue were measured using computed tomography before and after treatment. Two experienced radiologists used SliceOmatic Software version 5.0 (TomoVision) for calculating the cross-sectional area of the muscle and adipose tissue in centimeters squared at the third lumbar vertebra (L3) (15 (link)). Muscle area (MA), muscle density (MD), visceral adipose tissue area (VAA), subcutaneous adipose tissue area (SAA), and total adipose density (TAD) were quantified separately. Total adiposity tissue area (TAA) was calculated as the sum of VAA and SAA.
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