MARS spectral molecular imaging of lamb tissue: data collection and image analysis

Abstract

In this experiment, a meat specimen was prepared from a fresh lamb chop, which included muscle (water-like), fat (lipid-like) and bone (calcium-like) regions, and scanned. We used a 2 mm thick CdTe sensor (128×128), bump bonded at 110 µm to Medipix3RX readout chip and installed in the MARS-CT4 scanner. In charge summing mode (CSM), 720 circular projections over 360° were acquired using a Source-Ray SB-80-1K x-ray tube (Source-Ray Inc, Ronkonkoma, NY) with a tungsten anode having 1.8-mm-Al equivalent intrinsic filtration. Several vertical positions of the CdTe Medipix3RX camera were used to create a virtual detector to cover the 23 mm field of view (FOV). The source to detector distance (SDD) was 131.8mm and object to detector distance (ODD) was 48mm. Camera readout was performed using the MARS readout system. Before the measurements, threshold equalization with respect to the noise edge, and energy calibration of the detector, were performed. Flat-field measurements (500 flat-fields per energy bin) were taken before specimen scanning to correct for variations in pixel response. Dark-field images (50 dark-fields per energy bin) were also acquired before and after the scan. The tube was operated at 50 kVp with a current of 120 μA and using four low energy thresholds (15, 20, 25, 30 keV). The exposure time of each acquisition was 40 ms. For data analysis and HU calibration, a phantom having CaCl2 (320 mg/ml) and lipid (vegetable oil), along with air and water, was also scanned with the same parameters mentioned earlier. The raw data in DICOM format from the scanner was processed using the MARS Image Processing Suite. More detail can be found from the relevant paper data paper.