How effective can optical-CT 3D dosimetry be without refractive fluid matching?

Abstract

Achieving accurate optical CT 3D dosimetry without the use of viscous refractive index (RI) matching fluids would greatly increase convenience. Software has been developed to simulate optical CT 3D dosimetry for a range of scanning configurations including parallel-beam, point and converging light sources. For each configuration the efficacy of 3 refractive media were investigated: air, water, and a fluid closely matched to Presage (RI = 1.00, 1.33 and 1.49 respectively). The results revealed that the useable radius of the dosimeter (i.e. where data was within 2% of truth) reduced to 68% for water-matching, and 31% for dry-scanning in air. Point source incident ray geometry produced slightly more favourable results, although variation between the three geometries was relatively small. The required detector size however, increased by a factor six for dry-scanning, introducing cost penalties. For applications where dose information is not required in the periphery, some dry and low-viscous matching configurations may be feasible.

Water equivalent PRESAGE® for synchrotron radiation therapy dosimetry

“…The dosimeter was immersed in a tank of ethyl benzoate as the refractive index matching medium. Ethyl benzoate has a refractive index of 1.504 which closely matches the refractive index of PRESAGE ® which is approximately 1.51 …”

Validation of the fabricated cast nylon head phantom for stereotactic radiosurgery end-to-end test using alanine dosimeter

“…[ 6 7 8 ] In addition, several studies on SRS have been conducted along with the investigation of anthropomorphic phantoms utilized for complex radiotherapy treatment quality assurance, audits, and trials. [ 9 10 11 12 ] Since alanine has a good response in high dose, it has been reported to benefit a SRS of the intracranial treatment using radiation dose of 15–24 Gy. [ 13 ] Furthermore, an alanine dosimeter has been used in high-dose dosimetry to calculate a wide range of radiation doses across various published studies on SRS.…”