Practical time considerations for optically stimulated luminescent dosimetry (OSLD) in total body irradiation

Abstract

Total body irradiation (TBI) treatments are used to treat the whole body in preparation for hematopoietic stem cell (or bone marrow) transplantation. Our standard clinical regimen is a 12 Gy in 6 fraction, bi-daily technique using 6 MV X-rays at an extended Source-to-Surface distance (SSD) of 300 cm. Utilizing these characteristics, the beam dose rate is reduced below 7 cGy/min as is standard for TBI treatment. Dose received by the patient is monitored using optically stimulated luminescent dosimetry (OSLD). This work presents some practical calibration corrections based on time-dependant factors for OSLD calibration related to TBI procedure. Results have shown that a negligible difference is seen in OSL sensitivity for 6 MV X-rays irradiated in standard SSD (100 cm) and high dose rate (600 cGy/min) conditions compared to extended SSD (300 cm) and low TBI dose rate (6 cGy/min) conditions. Results have also shown that whilst short term signal fading occurs in the OSL after irradiation at a high dose rate (37% reduction in signal in the first 15 min), thereafter, negligible differences are seen in the OSL signal between 600 and 7 cGy/min irradiations. Thus a direct comparison can be made between calibration OSLs and clinical TBI OSLs between 15 min and 2 h. Finally a table is presented to provide corrections between calibration OSL readout and clinical TBI dose readout for a period up to 7 days. Combining these three results allows users to pre-irradiate their calibration OSLs at standard dose rate and SSD, up to 1 week prior to clinical treatment, and still provide accurate in-vivo dosimetry. This can help with time saving and work efficiency in the clinic.

Radiation dose in non-dental cone beam CT applications: a systematic review

“…The most significant practical correction factor (easily determinable) may be the one to account for the beam average kV. Contrary to the perception by some, signal fading is not a significant issue over a period of several days or weeks if the OSLDs are handled properly [44,45].…”

Technical note: Sources of systemic error in total body irradiation and total skin electron therapy in vivo measurements using nanoDot optically stimulated luminescence dosimeters within high‐efficiency clinics

“…[1][2][3][4] OSLD stands out as a convenient, high-throughput dosimeter for total body irradiation (TBI) and total skin electron therapy (TSET) in vivo measurements, due to its ease of use, rapid read-out, and reliability. [4][5][6] Dosimetric accuracy of OSLDs for both TBI and TSET, with proper corrections, is sufficient and appropriate within the dosimetry guidelines laid out in reports by AAPM task group 29 and 30. 7,8 Despite the advantages that OSLDs offer in TBI and TSET in vivo dosimetry, efficiency-driven clinical use of OSLDs may increase uncertainty in measured dose according to the report by AAPM task group 191 , mainly due to the difference between highefficiency versus high-accuracy methods to compensate for individual dosimeter response.…”

Development of a dosimetry system for therapeutic X‐rays using a flexible amorphous silicon thin‐film solar cell with a scintillator screen

“…In addition to verifying treatment doses to prevent accidents during RT, radiation detectors are used for quality assurance (QA) of the machines used for treatment. [1][2][3][4] Several types of detectors, including metal-oxide semiconductor field-effect transistors (MOSFETs) 5,6 ; 3D radiation dosimeters, such as polymers, radiochromic gels, and radiochromic plastics 7,8 ; thermoluminescent dosimeters (TLDs) 9,10 ; optically simulated luminescent dosimeters (OSLDs) 11,12 ; radio-photoluminescent dosimeters (RPLDs) 13,14 ; and radiochromic films, are used to measure doses for therapeutic X-rays. 15,16 However, passive detectors, including TLDs, OSLDs, radiochromic film, and RPLDs, do not provide measured values immediately, but require a few minutes to hours of postprocessing to provide results.…”