151751-Najiba-Chargi

34 CHAPTER 2 PATIENTS AND METHODS ETHICAL CONSIDERATIONS The design of this study was approved by the Medical Ethical Research Committee of the Uni - versity Medical Center Utrecht (approval ID 16/595 C). All data was retrieved retrospectively and processed in an anonymized fashion. STUDY POPULATION Patients who were diagnosed at the University Medical Center Utrecht, The Netherlands be - tween 2010 and 2018 with a primary head and neck squamous cell carcinoma were evaluated for this study. Since the effect of previous treatments of the neck on SMA measurement at the level of C3 is not known, patients previously treated with surgery or radiotherapy of the neck were excluded. Patients were included if a pre-treatment whole body FDG-PET/CT scan in radiationmould (as part of radiotherapy treatment planning) was available. Other relevant parameters, including length and weight at the time of imaging, sex, age, tumor localization and clinical TNM stage (7 th and 8 th edition) were retrospectively retrieved. In total, 200 patients were selected. ASSESSMENT OF CROSS-SECTIONAL SKELETAL MUSCLE AREA Pre-treatment FDG-PET/CT-imaging was performed in all patients according to a standard - ized protocol. Muscle tissue was identified using Hounsfield Unit (HU) range settings from -29 to +150 HU, which is specific for muscle tissue. Muscle tissue was delineated at the level of the third lumbar vertebra (L3) and the third cervical vertebra (C3). The SMA was defined as the pixel area within the delineated area with a radiodensity between -29 and +150 HU. 15,16 Delineation of muscle tissue was manually performed using the Volumetool v.1.6.5 Research Software Package, designed in our center as an image evaluation, registration and delineation system for radiotherapy planning. 17 For delineation of muscle tissue at the level of L3, the first slide when scrolling from caudal to cranial direction to show the entire vertebral arc and both transverse processes was selected. The contours of the abdominal wall and paraspinal mus - cles were manually traced. SMA at the level of L3 was calculated by adding up the abdominal wall and paraspinal muscle area. For delineation of muscle tissue at the level of C3, the first slide when scrolling from caudal to cranial direction to show both transverse processes and the entire vertebral arc was selected. The contours of the paravertebral muscles and both sternocleidomastoid muscles were manually traced. The SMA at the level of C3 was calculat - ed as the sum of the paravertebral muscle and both sternocleidomastoid muscles. If evident lymph nodemetastasis hindered accurate delineation of one sternocleidomastoidmuscle, the SMA of the contralateral sternocleidomastoidmuscle was used as an estimation of the SMA of the affected sternocleidomastoidmuscle. 7 After delineation, SMA was automatically retrieved from Volumetool. First, all head and neck CT scans (C3) were delineated, and afterwards all abdominal scans (L3). Figure 1 shows muscle tissue delineation at the level of C3 and L3.