A study on rectal dose measurement in phantom and in vivo using Gafchromic EBT3 film in IMRT and CyberKnife treatments of carcinoma of prostate

Abstract

The objective of this study is to check the feasibility of in vivo rectal dose measurement in intensity-modulated radiotherapy (IMRT) and CyberKnife treatments for carcinoma prostate. An in-house pelvis phantom made with bee's wax was used in this study. Two cylindrical bone equivalent materials were used to simulate the femur. Target and other critical structures associated with carcinoma prostate were delineated on the treatment planning images by the radiation oncologist. IMRT treatment plan was generated in Oncentra Master Plan treatment planning system and CyberKnife treatment plan was generated in Multiplan treatment planning system. Dose measurements were carried out in phantom and in patient using Gafchromic EBT3 films. RIT software was used to analyze the dose measured by EBT3 films. The measured doses using EBT3 films were compared with the TPS-calculated dose along the anterior rectal wall at multiple points. From the in-phantom measurements, it is observed that the difference between calculated and measured dose was mostly within 5%, except for a few measurement points. The difference between calculated and measured dose in the in-patient measurements was higher than 5% in regions which were away from the target. Gafchromic EBT3 film is a suitable detector for in vivo rectal dose measurements as it offers the possibility of analyzing the dose at multiple points. In addition, the method of extending this in vivo rectal dose measurement technique as a tool for patient-specific quality assurance check is also analyzed.

Feasibility of a dual detector system to perform transit dosimetry and MV imaging in-vivo

“…A key limitation of QA with the detectors aforementioned is that they measure either surface/exit dose upon a patient or inside body cavities but only for a single point. GAFChromic film can be used to measure a tissue equivalent, high spatial resolution 2D dose map [7,8] but does not provide real time readout and the response is optical scanner and user dependent [9]. The complexity of modern intensity-modulated radiation therapy (IMRT) requires dose measurements throughout the treatment area with high spatial resolution and real-time verification of the treatment.…”

Dosimetric and radiobiological comparison of CyberKnife M6TM InCise multileaf collimator over IRISTM variable collimator in prostate stereotactic body radiation therapy

“…[ 6 7 8 ] This has established the CyberKnife (CK) robotic system as a standard treatment modality for prostate stereotactic body radiation therapy (SBRT) due to its wide range of noncoplanar beams for a confined dose coverage to planning tumor volume (PTV) and normal tissue dose sparing, as well as its ability for intrafractional tumor tracking. [ 9 10 11 ] CK with dose scheme of 35 Gy or 36.25 Gy in five fractions has been proven to be one of the best options for prostate SBRT due to its excellent clinical outcome with a high local tumor control and low-grade toxicities. [ 12 13 14 15 ]…”

In-vivo dosimetry with Gafchromic films for multi-isocentric VMAT irradiation of total marrow lymph-nodes: a feasibility study

“…The EBT3 films were processed with an Epson10000XL scanner and compared with the TPS- calculated dose along the patient support (see Figure 2 ), using I’mRT OmniPro software (Scanditronix). For further information about absolute dose calibration we refer to the bibliography [ 23 , 24 ].…”

“…In our study we decided to use GafChromics EBT3 films because they allow the detection of large field areas with an adequate dose response in terms of energy dependence, linearity, and reproducibility. GafChromics EBT3 are radiation-induced auto-developing photon and electron-beam analysis films and are available for therapeutic radiation dosimetry in radiotherapy applications to provide accurate in-vivo dosimetry measurements [ 23 , 24 ]. In particular, the ability to offer a bidimensional evaluation of the dose, is an attractive option for TMI-TMLI in-vivo dosimetry as the integral delivered dose is originated by different arcs with separate isocenter positions.…”