title: Characterization of an orthovoltage biological irradiator used for radiobiological research.
abstract: Orthovoltage irradiators are routinely used to irradiate specimens and small animals in biological research. There are several reports on the characteristics of these units for small field irradiations. However, there is limited knowledge about use of these units for large fields, which are essential for emerging large-field irregular shape irradiations, namely total marrow irradiation used as a conditioning regimen for hematological malignancies. This work describes characterization of a self-contained Orthovoltage biological irradiator for large fields using measurements and Monte Carlo simulations that could be used to compute the dose for in vivo or in vitro studies for large-field irradiation using this or a similar unit. Percentage depth dose, profiles, scatter factors, and half-value layers were measured and analyzed. A Monte Carlo model of the unit was created and used to generate depth dose and profiles, as well as scatter factors. An ion chamber array was also used for profile measurements of flatness and symmetry. The output was determined according to AAPM Task Group 61 guidelines. The depth dose measurements compare well with published data for similar beams. The Monte Carlo-generated depth dose and profiles match our measured doses to within 2%. Scatter factor measurements indicate gradual variation of these factors with field size. Dose rate measured by placing the ion chamber atop the unit's steel plate or solid water indicate enhanced readings of 5 to 28% compared with those measured in air. The stability of output over a 5-year period is within 2% of the 5-year average.
authors.affiliation: Department of Radiation Oncology, University of Minnesota, 420 Delaware Street, SE MMC 494, Minneapolis, MN 55455, USA.
authors.forename: Rezvan
authors.initials: R
authors.lastname: Azimi
authors.affiliation: Department of Radiation Oncology, University of Minnesota, 420 Delaware Street, SE MMC 494, Minneapolis, MN 55455, USA.
authors.forename: Parham
authors.initials: P
authors.lastname: Alaei
authors.affiliation: Department of Medical Physics, Velindre Cancer Centre, Velindre Road, CF14 2TL, Cardiff, UK.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Spezi
authors.affiliation: Department of Radiation Oncology, University of Minnesota, 420 Delaware Street, SE MMC 494, Minneapolis, MN 55455, USA huixx019@umn.edu.
authors.forename: Susanta K
authors.initials: SK
authors.lastname: Hui
mesh_terms: D000818:Animals; D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D015233:Models, Statistical; D011829:Radiation Dosage; D011853:Radiobiology / Q000295:instrumentation*; D011874:Radiometry; D012542:Scattering, Radiation; D014916:Whole-Body Irradiation / Q000295:instrumentation* / Q000662:veterinary*
keywords: Monte Carlo; biological irradiator; dosimetry; orthovoltage