Data Collection and Definitions
Medical records of these patients were reviewed. Patients with missing
data and without abdominal CT were not included in the study. This study
screening, inclusion and exclusion flow chart is presented in Figure 1.
Radiological evaluation of the patients with abdominal CT was performed
by the same experienced radiologist using standard anatomical landmarks.
During abdominal CT the muscles at the level of L3 vertebra were
determined and the psoas, paraspinal muscles (erector spinae, quadratus
lumborum) and abdominal wall muscles (transverse abdominus, external and
internal obliques, rectus abdominus) were marked. The muscle
cross-sectional area at the level of L3 was used as it was linearly
associated with whole-body muscle mass, and by dividing this value by
the square of the height the skeletal muscle index was calculated for
each patient in cm2/ m2. CT scan
with 64-detector (Aquilion 64, Toshiba Medical Systems, Tochigi, Japan,
2011) was used in abdominal CT. Two mm section thickness, 64 x 0.5
collimation, 0.5 seconds rotation time, 120 kV and 300 mA were used in
CT investigations. The evaluation of the images was done on the OsiriX
(10.0, 64 bit, Switzerland) workstation. The evaluation was performed at
L3 vertebral level, in the axial section in which both transverse
projections were observed. Skeletal muscle area was measured by 2D/3D
segmentation tool at this level. In skeletal muscle area measurements,
pixels in the range of -30, +150 Hounsfield Unit (HU) density were
marked by automatic segmentation [14,15]. The necessary adjustments
in the marked contours of the fields have been made manually.