Medical Physics Seminar – Monday, October 29, 2018
Determination of Lateral Half Value Layer Profiles in Computed Tomography
Robert Bujila (hosted by Dr. Timothy Szczykutowicz)
Medical Radiation Physics and Nuclear Medicine Karolinska University Hospital Stockholm, Sweden
Shaped (bowtie) filters are an integral component in Computed Tomography (CT). As the shape and composition of these filters are generally not known by clinical Medical Physicists, this information must be inferred (e.g., through measurements). A novel measurement rig was developed to determine lateral half value layer (HVL) profiles at different fan angles with a constant focal spot to ionization chamber distance under a narrow beam geometry. This rig was used to measure HVL profiles on 6 CT scanners from the four major CT vendors covering all shaped filters and radiation qualities on each scanner. The resulting HVL profiles have applications in, for example, source modeling.