Commissioning optically stimulated luminescence in vivo dosimeters for fast neutron therapy

Journal Article · Fri Jan 15 04:00:00 EST 2016 · Medical Physics

DOI:https://doi.org/10.1118/1.4938262· OSTI ID:22579817

Sandison, George ^[1]; Yang, Fei ^[2]; Woodworth, Davis ^[3]; McCormick, Zephyr ^[4]

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1. Department of Radiation Oncology, University of Washington, Seattle, Washington 98115 (United States)
2. Sylvester comprehensive Cancer Center, University of Miami, Miami, Florida 33124 (United States)
3. Department of Physics, University of Reno, Reno, Nevada 89557 (United States)
4. Department of Physics, University of California, Santa Barbara, California 93106 (United States)

Purpose: Clinical in vivo dosimeters intended for use with photon and electron therapies have not been utilized for fast neutron therapy because they are highly susceptible to neutron damage. The objective of this work was to determine if a commercial optically stimulated luminescence (OSL) in vivo dosimetry system could be adapted for use in fast neutron therapy. Methods: A 50.5 MeV fast neutron beam generated by a clinical neutron therapy cyclotron was used to irradiate carbon doped aluminum oxide (Al{sub 2}O{sub 3}:C) optically simulated luminescence dosimeters (OSLDs) in a solid water phantom under standard calibration conditions, 150 cm SAD, 1.7 cm depth, and 10.3 × 10.0 cm field size. OSLD fading and electron trap depletion studies were performed with the OSLDs irradiated with 20 and 50 cGy and monitored over a 24-h period to determine the optimal time for reading the dosimeters during calibration. Four OSLDs per group were calibrated over a clinical dose range of 0–150 cGy. Results: OSLD measurement uncertainties were lowered to within ±2%–3% of the expected dose by minimizing the effect of transient fading that occurs with neutron irradiation and maintaining individual calibration factors for each dosimeter. Dose dependent luminescence fading extended beyond the manufacturer’s recommended 10 min period for irradiation with photon or electron beams. To minimize OSL variances caused by inconsistent fading among dosimeters, the observed optimal time for reading the OSLDs postirradiation was between 30 and 90 min. No field size, wedge factor, or gantry angle dependencies were observed in the OSLDs irradiated by the studied fast neutron beam. Conclusions: Measurements demonstrated that uncertainties less than ±3% were attainable in OSLDs irradiated with fast neutrons under clinical conditions. Accuracy and precision comparable to clinical OSL measurements observed with photons can be achieved by maintaining individual OSLD calibration factors and minimizing transient fading effects.

• OSTI ID: 22579817
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 1 Vol. 43; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
62 RADIOLOGY AND NUCLEAR MEDICINE
ACCURACY
ALUMINIUM OXIDES
CALIBRATION
CALIBRATION STANDARDS
COMMISSIONING
CYCLOTRONS
DOPED MATERIALS
DOSEMETERS
DOSIMETRY
ELECTRON BEAMS
FAST NEUTRONS
IN VIVO
IRRADIATION
LUMINESCENCE
MEV RANGE 10-100
NEUTRON BEAMS
NEUTRON THERAPY
PHANTOMS
RADIATION DOSES