Fan-beam scanning laser optical CT system for large volume 3D dosimetry

Introduction: Optical CT scanning of radiochromic gel dosimeters is a method for true 3D dosimetry, which is becoming increasingly needed as radiation therapy techniques become more advanced. Optical CT has developed from slow pencil beam laser scanners to fast cone-beam scanners using cameras. However, scattered light perturbs these broad-beam scanners, resulting in cupping artifacts and loss of accuracy, especially as we move to larger volumes. In fact, the single-ray, single-detector geometry of the original systems will allow for the best stray light rejection and therefore the most accurate measurements. Thus our objective was to design and build a scanning-laser system with high accuracy and sufficient speed for 3D dosimetry.