A comparative study of small field total scatter factors and dose profiles using plastic scintillation detectors and other stereotactic dosimeters: The case of the CyberKnife

• Published in: Medical physics (Lancaster) 2013-01, Vol.40 (1), p.011719-n/a
• Main Authors: Morin, Jonathan, Béliveau-Nadeau, Dominic, Chung, Eunah, Seuntjens, Jan, Thériault, Dany, Archambault, Louis, Beddar, Sam, Beaulieu, Luc
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; biomedical measurement; COMPUTERIZED SIMULATION; CyberKnife system; dose profiles; DOSEMETERS; dosimeters; DOSIMETRY; Dosimetry/exposure assessment; Electron scattering; ENERGY DEPENDENCE; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Measurement of nuclear or x‐radiation; Measuring for diagnostic purposes; Identification of persons; MONTE CARLO METHOD; Monte Carlo methods; Particle beam detectors; PLASTIC SCINTILLATION DETECTORS; Plastics; Position sensitive detectors; QUALITY ASSURANCE; RADIATION DOSES; RADIATION PROTECTION AND DOSIMETRY; radiation therapy; RADIOLOGY AND NUCLEAR MEDICINE; Radiometry; Radiosurgery; Radiosurgery - methods; RADIOTHERAPY; Radiotherapy Dosage; Scattering, Radiation; Scintillation Counting - methods; Scintillation detectors; Silicon; Silicon detectors; SILICON DIODES; solid scintillation detectors; SPATIAL RESOLUTION; stereotactic radiosurgery; SURGERY; Therapeutic applications, including brachytherapy; total scatter factors; Tubes for determining the presence, intensity, density or energy of radiation or particles
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.4772190

Purpose: Small-field dosimetry is challenging, and the main limitations of most dosimeters are insufficient spatial resolution, water nonequivalence, and energy dependence. The purpose of this study was to compare plastic scintillation detectors (PSDs) to several commercial stereotactic dosimeters by measuring total scatter factors and dose profiles on a CyberKnife system. Methods: Two PSDs were developed, having sensitive volumes of 0.196 and 0.785 mm3, and compared with other detectors. The spectral discrimination method was applied to subtract Čerenkov light from the signal. Both PSDs were compared to four commercial stereotactic dosimeters by measuring total scatter factors, namely, an IBA dosimetry stereotactic field diode (SFD), a PTW 60008 silicon diode, a PTW 60012 silicon diode, and a microLion. The measured total scatter factors were further compared with those of two independent Monte Carlo studies. For the dose profiles, two commercial detectors were used for the comparison, i.e., a PTW 60012 silicon diode and Gafchromics EBT2. Total scatter factors for a CyberKnife system were measured in circular fields with diameters from 5 to 60 mm. Dose profiles were measured for the 5- and 60-mm cones. The measurements were performed in a water tank at a 1.5-cm depth and an 80-cm source-axis distance. Results: The total scatter factors measured using all the detectors agreed within 1% with the Monte Carlo values for cones of 20 mm or greater in diameter. For cones of 10–20 mm in diameter, the PTW 60008 silicon diode was the only dosimeter whose measurements did not agree within 1% with the Monte Carlo values. For smaller fields (