title: Properties of a commercial PTW-60019 synthetic diamond detector for the dosimetry of small radiotherapy beams.
abstract: A CVD based radiation detector has recently become commercially available from the manufacturer PTW-Freiburg (Germany). This detector has a sensitive volume of 0.004 mm(3), a nominal sensitivity of 1 nC Gy(-1) and operates at 0 V. Unlike natural diamond based detectors, the CVD diamond detector reports a low dose rate dependence. The dosimetric properties investigated in this work were dose rate, angular dependence and detector sensitivity and linearity. Also, percentage depth dose, off-axis dose profiles and total scatter ratios were measured and compared against equivalent measurements performed with a stereotactic diode. A Monte Carlo simulation was carried out to estimate the CVD small beam correction factors for a 6 MV photon beam. The small beam correction factors were compared with those obtained from stereotactic diode and ionization chambers in the same irradiation conditions The experimental measurements were performed in 6 and 15 MV photon beams with the following square field sizes: 10 × 10, 5 × 5, 4 × 4, 3 × 3, 2 × 2, 1.5 × 1.5, 1 × 1 and 0.5 × 0.5 cm. The CVD detector showed an excellent signal stability (<0.2%) and linearity, negligible dose rate dependence (<0.2%) and lower response angular dependence. The percentage depth dose and off-axis dose profiles measurements were comparable (within 1%) to the measurements performed with ionization chamber and diode in both conventional and small radiotherapy beams. For the 0.5 × 0.5 cm, the measurements performed with the CVD detector showed a partial volume effect for all the dosimetric quantities measured. The Monte Carlo simulation showed that the small beam correction factors were close to unity (within 1.0%) for field sizes ≥1 cm. The synthetic diamond detector had high linearity, low angular and negligible dose rate dependence, and its response was energy independent within 1% for field sizes from 1.0 to 5.0 cm. This work provides new data showing the performance of the CVD detector compared against a high spatial resolution diode. It also presents a comparison of the CVD small beam correction factors with those of diode and ionization chamber for a 6 MV photon beam.
authors.affiliation: Departamento de Física, Universidad Autónoma Metropolitana, Unidad Iztapalapa, México D.F., Mexico. Laboratorio de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, C.P. 14269, México, D.F., Mexico. Unidad de Radioneurocirugía, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, C.P. 14269, México, D.F., Mexico.
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Lárraga-Gutiérrez
authors.forename: Paola
authors.initials: P
authors.lastname: Ballesteros-Zebadúa
authors.forename: Miguel
authors.initials: M
authors.lastname: Rodríguez-Ponce
authors.forename: Olivia Amanda
authors.initials: OA
authors.lastname: García-Garduño
authors.forename: Olga Olinca Galván
authors.initials: OO
authors.lastname: de la Cruz
mesh_terms: D018130:Diamond / Q000032:analysis* / Q000737:chemistry*; D006801:Humans; D009010:Monte Carlo Method; D010315:Particle Accelerators; D017785:Photons / Q000627:therapeutic use*; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D011878:Radiotherapy / Q000295:instrumentation* / Q000379:methods*
chemical_list: D018130:Diamond