Optical CT imaging of solid radiochromic dosimeters in mismatched refractive index solutions using a scanning laser and large area detector

Abstract

The fiducial-based ray path measurement scheme, coupled with an iterative reconstruction algorithm, enabled optical CT scanning of PRESAGE® dosimeters immersed in mismatched refractive index solutions. However, improvements to PRESAGE® dose response uniformity are required.

Development of a 3D remote dosimetry protocol compatible with MRgIMRT

“…Varying sensitivity between small (4 ml) and large volumes (>1 kg) of the same formulation and batch has been noted, as well as a gradual decrease in OD, postirradiation (< 4% per day) . More recent works reported spatially nonuniform dose‐response in 1 kg PRESAGE ® , with variations ranging from 5% to 20% …”

Optical and X-ray computed tomography scanning of 3D dosimeters

“…Examples of ray position correction have been reported by several authors [10,12,13,20]. Scattered light in hydrogels is a common problem especially with broad beam geometries and small fields [17,[21][22][23][24].…”

“…This approach should minimize stray light. Simpler systems may have more optical aberrations but computations can sort actual ray paths through dosimeters [9][10][11][12][13]. Lowering acceptance angles is an effective method to reduce stray light.…”

“…Gelatin is optically active and can be a further source of polarization artifacts. Polymerization to form plastic dosimeters can also introduce spatially unique optical activity [13]. The effects of polarization need to be evaluated for each dosimeter.…”

“…In this approach, a matching solid aquarium is required for each dosimeter size. It is possible to scan PRESAGE® with low viscosity liquids than have much lower refractive indexes with specific scanner geometries that have large effective area detector and calibration of ray paths through the dosimeters [13].…”