title: Diamond detector in absorbed dose measurements in high-energy linear accelerator photon and electron beams.
abstract: Diamond detectors (DD) are preferred in small field dosimetry of radiation beams because of small dose profile penumbras, better spatial resolution, and tissue-equivalent properties. We investigated a commercially available 'microdiamond' detector in realizing absorbed dose from first principles. A microdiamond detector, type TM 60019 with tandem electrometer is used to measure absorbed doses in water, nylon, and PMMA phantoms. With sensitive volume 0.004 mm3, radius 1.1mm, thickness 1 x10(-3) mm, the nominal response is 1 nC/Gy. It is assumed that the diamond detector could collect total electric charge (nC) developed during irradiation at 0 V bias. We found that dose rate effect is less than 0.7% for changing dose rate by 500 MU/min. The reproducibility in obtaining readings with diamond detector is found to be ± 0.17% (1 SD) (n = 11). The measured absorbed doses for 6 MV and 15 MV photons arrived at using mass energy absorption coefficients and stop-ping power ratios compared well with Nd, water calibrated ion chamber measured absorbed doses within 3% in water, PMMA, and nylon media. The calibration factor obtained for diamond detector confirmed response variation is due to sensitivity due to difference in manufacturing process. For electron beams, we had to apply ratio of electron densities of water to carbon. Our results qualify diamond dosimeter as a transfer standard, based on long-term stability and reproducibility. Based on micro-dimensions, we recommend these detectors for pretreatment dose verifications in small field irradiations like stereotactic treatments with image guidance.
authors.affiliation: National Oncology Center, Royal Hospital. ramamoorthy.ravichandranrama@yahoo.com.
authors.forename: Ramamoorthy
authors.initials: R
authors.lastname: Ravichandran
authors.forename: John Pichy
authors.initials: JP
authors.lastname: Binukumar
authors.forename: Iqbal
authors.initials: I
authors.lastname: Al Amri
authors.forename: Cheriyathmanjiyil Antony
authors.initials: CA
authors.lastname: Davis
mesh_terms: D002138:Calibration; D018130:Diamond / Q000737:chemistry*; D004583:Electrons; D006801:Humans; D009010:Monte Carlo Method; D010315:Particle Accelerators / Q000295:instrumentation*; D019047:Phantoms, Imaging; D017785:Photons
chemical_list: D018130:Diamond