Illustration of extended CT number scales
Standard CT reconstruction data is stored using 12-bit unsigned integers (i.e. having possible values of 0 to 4095). These unsigned values are rescaled to a range encompassing -1024 through 3071 (using an offset, or intercept of -1024). However CT data can also…
CT Density Tables
The use of CT data within a planning system necessitates a conversion from the Hounsfield scale, with units (HU) describing the radiodensity of the imaged tissue (compared to water, for X-ray energies), into density values, which the planning system can…
Open Field Electron PDDs
The following percentage depth dose (PDD) values were obtained for “open-field” electron beams (that is, with jaws fully open at 40×40 cm² and no applicators attached). The beams were delivered using a Varian 21iX linear accelerator in the process of being…