Sliceomatic 5

All patients received PG-SGA, abdominal CT, anthropometric measurements, laboratory biochemical testing, and bioelectrical impedance analysis (BIA) within 24 h of admission. Age, sex, height, weight, and albumin (ALB), pre-albumin (PA), neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) in the peripheral blood were recorded. BMI was calculated by weight (kg)/ height ² (m)². BIA is a technique for measuring body composition using capacitance (Xc) and resistance (R) of biological tissues. In this study, resistance and capacitance were directly measured in ohms at 50 kHz, 800 mA by Inbody S10 (Biospace Co®). As the equation generated an indicator of body composition, phase angle (PhA) (Resistance/Capacitance) * (180/π).
SliceOmatic 5.0 software (TOMOVISION Canada) was used to analyze abdominal CT images on two consecutive planes of the L3 level. The skeletal muscle areas were measured at each plan, and the average was adopted as skeletal muscle mass, including the psoas major, erector spinae, quadratus lumbar muscles, transverse abdominis, external oblique, and internal oblique. Then the L3 SMI was calculated by skeletal muscle area (cm²)/height²(m²).

SliceOmatic 5.0 software (TOMOVISION, Canada) was used to analyze abdominal CT images. According to the voxel values, –29 to + 150 Hu was identified as skeletal muscle mass and −190 to −30 Hu was identified as adipose tissue mass. Then, the skeletal muscle area (SMA) and VFA at the third lumbar vertebra were sketched. The SMA includes the psoas major, the erector spinae, the quadratus lumborum, the transverse abdominis, the external oblique, and the internal oblique. The VFA represents the intra-abdominal adipose tissue. Figure 1 displays the diagrammatic sketch illustrating two patients with the same BMI but different body compositions. SMI (cm²/m²) = SMA/height² (m²).

Demographic and clinical variables included age, sex, race, body mass index (BMI), per cent body weight (BW) loss in the 6 months prior to diagnosis, as well as serum albumin, bilirubin, haemoglobin and platelet count at the time of diagnosis. Computed tomography scans at the time of diagnosis were obtained and analysed using sliceOmatic ® 5.0 software (TomoVision, Magog, Canada) to compute skeletal muscle index (SMI), muscle radiation attenuation (MRA), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT) and intramuscular adipose tissue (IMAT) of axial images at the level of the L3 vertebra. Pathologic variables included tumour stage, tumour size, nodal stage, number of positive lymph nodes, lymph node positivity ratio, margin status, presence of perineural or lymphovascular invasion, and histologic differentiation. Overall survival time (months) from the date of surgery to death was calculated. Vital status was confirmed as of 15 March 2021.

Abdominal MRI examination was performed using a Philips Achieva 3.0-T magnetic resonance imaging system (Philips Medical Systems, Eindhoven, The Netherlands). Breath-hold fast imaging with a 40-ms repetition time, 2-ms echo time, 50-cm field of view, and 256 × 256 matrix was used to acquire the cross-sectional MR images. One 10-mm slice positioned at the L4 level with a clear outline was selected for analysis using SliceOmatic 5.0 software (TomoVision, Magog, Canada) by a medically trained technician. The psoas CSA, SFA, and VFA were measured using the following steps: regional threshold procedures were first applied using the “Region Growing” mode, after which manual delineation was used to draw borders among different tissues in the “edit mode” when necessary (10 (link)). The software calculated different colored areas and expressed the measurements in cm². VFA≥80cm² was defined as visceral obesity.

Cross-sectional areas (cm²) of skeletal muscle, VAT, and SAT were assessed using standard radiodensity thresholds measured in Hounsfield units (HU) in preoperative CT images at the level of the 3rd lumbar vertebrae using Slice-O-Matic 5.0 (Tomovision, Montreal, Canada). For skeletal muscle, the threshold values were between − 29 and + 150 HU, for VAT between − 150 and − 50 HU, and for SAT between − 190 and − 30 HU [22 (link), 23 (link)]. The skeletal muscle cross-sectional area was adjusted for height squared (cm²/m²) to calculate skeletal muscle index (SMI). SMR was assessed as the mean radiodensity of the total skeletal muscle cross-sectional area at the level of the 3rd lumbar vertebrae.