Definition edge scanner

Most exams were performed as part of an initial trauma evaluation and scanned on either a Siemens Flash scanner or Siemens Definition Edge scanner. Standard CT parameters for the trauma protocol were 2.0 mm slice thickness with 1.2 mm slice increment for the chest, with both a vascular optimized kernel (B30f) axial reconstruction and a dedicated high spatial resolution kernel for fracture evaluation (B70). The abdominopelvic portion of the exam was reconstructed with 3.0 mm slice thickness at 2.0 mm slice increment, with soft tissue kernel (I30) and a medium strength setting for SAFIRE. The chest and the abdominopelvic portions of the exam were reconstructed in both sagittal and coronal planes as well. The chest and the abdominopelvic acquisitions are done at fixed 120kVP, with Quality reference mAs of 240.

There are 5 CT scanners in service at the Department of Radiation Oncology at the University of Maryland. There are 4 Brilliance Big Bore scanner (Philips Medical Systems, Best, the Netherlands) and 1 Definition Edge scanner (Siemens, Erlangen, Germany). All the Philips CT scanners are located in the photon clinic, and the Siemens CT scanner is located in the proton clinic. To establish the HU values with known materials, an electron density phantom (model 062M, CIRS, Carlton, Victoria, Australia) containing 7 tissue-equivalent electron density plugs and 1 water vial [8 ] in an abdominal configuration, with 2 nested disks combined, was imaged with all 5 CT scanners. Elemental composition and the density of the plugs were obtained from the phantom manufacturer. All 5 CT scanners used similar scanning protocols; 120 peak kilovoltage, 3-mm slice thickness, and 500-mm field of view. All the images were transferred to the Varian Eclipse TPS (version 13.7) to obtain the measured HU values from the plugs. We obtained 6 sets of HU values for the electron density phantom: 5 from the CT scanners, and 1 from the averaged HU values from the 5 CT scanners.