Computer Assisted tomography analysis of Hounsfield units (HU)

CT scans were acquired on multiple trabecular bone cross sections of AVNFH patients (n = 7) and healthy controls (n = 4), using GE Discovery CT 750 HD GST FREEDom edition CT scanner at the Sri Sathya Sai Institute of Higher Medical Sciences Prasanthigram, India. Parameter used to acquire the CT image included: Tube voltage of the CT-scanner: 140 kV, current: 280 mA, slice thickness: 0.625 mm and interval between slices: 0.625 mm. CT acquisition was carried out in high resolution mode using the application software 13MW24.7 V40-PS HD64-G-GTL. CT images were saved in DICOM format using the Synapse software version 4.3.2 Fuji film medical system. U.S.A. Inc. Multiple elliptical Regions of Interest (ROI), each having an area of 50 mm² and perimeter size of 25 mm were superimposed on the reconstructed images of each of the bone slice using the synapse platform. CT intensities were computed in Hounsfield units (HU) for each of the ROIs. Median value of CT intensities was computed across all the bone slices independently for each patient/control sample.