The three-dimensional scintillation dosimetry method: test for a¹⁰⁶Ru eye plaque applicator

Abstract

The need for fast, accurate and high resolution dosimetric quality assurance in radiation therapy has been outpacing the development of new and improved 2D and 3D dosimetry techniques. This paper summarizes the efforts to create a novel and potentially very fast, 3D dosimetry method based on the observation of scintillation light from an irradiated liquid scintillator volume serving simultaneously as a phantom material and as a dose detector medium. The method, named three-dimensional scintillation dosimetry (3DSD), uses visible light images of the liquid scintillator volume at multiple angles and applies a tomographic algorithm to a series of these images to reconstruct the scintillation light emission density in each voxel of the volume. It is based on the hypothesis that with careful design and data processing, one can achieve acceptable proportionality between the local light emission density and the locally absorbed dose. The method is applied to a Ru-106 eye plaque immersed in a 16.4 cm3 liquid scintillator volume and the reconstructed 3D dose map is compared along selected profiles and planes with radiochromic film and diode measurements. The comparison indicates that the 3DSD method agrees, within 25% for most points or within approximately 2 mm distance to agreement, with the relative radiochromic film and diode dose distributions in a small (approximately 4.5 mm high and approximately 12 mm diameter) volume in the unobstructed, high gradient dose region outside the edge of the plaque. For a comparison, the reproducibility of the radiochromic film results for our measurements ranges from 10 to 15% within this volume. At present, the 3DSD method is not accurate close to the edge of the plaque, and further than approximately 10 mm (<10% central axis depth dose) from the plaque surface. Improvement strategies, considered important to provide a more accurate quick check of the dose profiles in 3D for brachytherapy applicators, are discussed.

Novel, full 3D scintillation dosimetry using a static plenoptic camera

“…Many of these dosimeters make use of the concept of tomography to reconstruct a 3D scintillation volume from many different perspectives (or projections). [15][16][17] While these techniques have shown potential to perform accurate dosimetry on a whole 3D volume, their application to dynamic, modulated radiation delivery is not straightforward, since components of the dosimeter need to rotate during acquisition, a fact which limits their real-time capability. Some other approaches use only fixed components to image and reconstruct a scintillating volume in real-time.…”

Liquid scintillator for 2D dosimetry for high‐energy photon beams

“…Because the propagation of light due to Čerenkov radiation is forward peaked, the initial direction of the particle is important. In addition, Kirov et al 9 showed that when the detector is placed at 90°with respect to the photon beam, which is the case in our setup, the contribution from Čerenkov light is expected to be only a few percent. Further evaluation of the specific scintillation solution will allow for an accurate correction of the Čerenkov effect.…”

“…In this preliminary work we do not correct for this effect. A possible solution could be a collimator grid 9 or a special lens system. The background due to Čerenkov radiation was not explicitly accounted for in the present study.…”

“…This idea was further developed and applied successfully to a small 3D dosimetry system, which was optimized for brachytherapy application to eye plaques. 9 The authors concluded that this method would require further investigations for larger liquid scintillator ͑LS͒ volumes.…”

Dose Calculations of the Ru/Rh-106 CCA and CCB Eyes Applicators

“…Šolc recently published simulation results of the MCNPX code for a COB-type applicator only, and showed a good agreement between the simulated doses to measurements results (Šolc, 2008). Dose measurements were carried out using three-dimensional scintillation dosimetry for CCX-type eye applicators, and isodose maps were obtained (Kirov et al 2005). The measurements results were presented for 4 mm depth and higher only.…”