SU-FF-T-260: In Vivo Dose Measurements for Total Body Irradiation Using Optically Stimulated Luminescent Dosimeters

Abstract

Purpose: In vivo dose measurements for Total Body Irradiation using optically stimulated luminescent dosimeters Method and Materials: The institution's standard of care for total body irradiation uses a 6 MV Varian 600C linac with the gantry angle at 90 degrees and field size of 40×40 cm2. The patient's midline is at 350 cm. A 1.2 cm acrylic spoiler is place 40 cm from the surface of the patient and an acrylic tray holding lead compensators is at the head of the gantry. Phantom measurements were made to determine suitability of optically stimulated luminescence dosimeters (OSLDs) for in vivo dosimetry of patients undergoing total body irradiation (TBI). A 30×30×30 cm3 solid water phantom was placed at 350 cm SAD. A calibrated plane parallel ROOS ion chamber was placed at the center of the phantom under 1 cm of build up. OSLDs and TLDs were also place on the phantom adjacent to the ROOS chamber at 1 cm depth. A treatment plan was created to deliver 100 cGy to the midplane of the phantom for 1 field. All three dosimeters were irradiated. A similar setup was created using an anthropomorphic phantom at 350 SAD, TLDs and OSLDs at three different locations. In addition, in vivo measurements were made for three patients undergoing total body irradiation at nine different body points. Results: OSLD phantom measurements were in agreement of the ROOS chamber (2.6%) and TLDs (3.8%) when using the solid water phantom. Comparative measurements between TLDs and OSLDs differed by as much as 4.5% for the anthropomorphic phantom irradiation. In vivo dosimetry using OSLDs for the three patients agreed within (7.6%) for TLDs. Conclusions: Results for both the phantom and patient measurements confirm that OSLDs are both suitable and recommended for required in vivo dosimetry in Total Body Irradiation.

Review of the results of the in vivo dosimetry during total skin electron beam therapy

“…For example, some institutions have explored IVD using OSL or MOSFET as a pioneering approach to patient safety protection instead of reserving them only for radiation protection. 24,[34][35][36] The integration of related data with routine tools and other medical devices could undeniably open new frontiers for in vivo dosimetry. We actually report here some experiences of IVD for TSEB using semiconductor diode technology, 1,8,9 although some authors conclude that these devices, contrary to some suggestions, could be actually convenient for real-time dose delivery verification, but with some anomalies.…”

“…Measurement tools for in vivo TSEB conditions: an overview During many years (starting from the eighties), in vivo TSEB dosimetry has concentrated upon clinical use of thermoluminescent dosimeters and -somewhat later -diode dosimeters (see Van Dam and Marinello, 4 chapters III and IV for an extended review; Furetta and Weng 32 for a comprehensive description of the dosimetric technique; and Furetta 33 for a general physical treatise about this mostly consolidated technique). More recent dosimetric alternatives (and more expensive too, but usually much less cumbersome and much less time-consuming, particularly in comparison with thermoluminescent dosimeters) are given by MOSFET Dosimeters (see Bloemen-van Gurp -particularly Chapter 3 -for an extended Review about the use of MOSFET devices 34 ), by optically stimulated dosimeters (OSL) (see Esquivel et al 35 for general IVD using these devices; and Viamonte et al 36 for an example of a commercially available OSL system, used for general external beam radiotherapy) and by electron paramagnetic resonance (EPR) dosimeters (see Shultka el al. for the comparison between l-alanine EPR dosimetry measurements and data from a clinical TPS, reporting discrepancies within a range of about 0.6% 37 ; and Schauer et al for a general review of this technique in medical dosimetry 38 ).…”