2D Monolithic silicon detectors for dosimetry in Small beam radiotherapy (Stereotactic Radiotherapy)

Radiation Therapy is one type of cancer’s treatment, which aims to kill or control tumour cells by using high energy radiation. However, it can affect both normal and tumour cells. Due to that, scientists worked to develop a new treatment technique of radiation delivery that focuses the high prescribed dose on the small localized area of tumour cells and protects the normal cells. This focal irradiation technique is called Stereotactic Radiosurgery (SRS). Using SRS allows the treatment of hard-to-reach lesions where surgery is not possible because of the risks resulting in the surgical procedures. The commissioning and Quality Assurance of SRS/SRT is complex and requires special dosimetry tools. Poor dosimetry of small-field characteristics may lead to reduced treatment efficacy, whether by under-dosage of targeted tumours or overirradiation of adjacent healthy tissues. Poor measurements of the small field characteristics, such as FWHM, penumbra width, output factors and percentage depth dose may result in pernicious health consequences, such as radiation-induced carcinogenesis. Hence, the dosimetry tool plays an important role in the SRS/SRT accuracy and precise delivery. Recently, silicon detectors have increased in popularity because they have high spatial resolution, small sensitive volume, high sensitivity to radiation, reasonable uniformity and provides real time measurements. The Centre for Medical Radiation Physics (CMRP) has developed two innovative monolithic silicon array detectors, DUO and OCTA, to be used in SRS/SRT for pretreatment quality assurance dosimetry. Therefore, the aim of this thesis is to characterise these two monolithic silicon detectors for small radiation field dosimetry employed in stereotactic radiotherapy

Today\u27s monolithic silicon array detector for small field dosimetry: The Octa

The dosimetry of small photon beams is challenging due to detector position uncertainties, dose averaging and lack of electronic equilibrium. Currently only few, single detectors are suitable for measurements in this context, and none is ideal. This study reports on the dosimetric characterization of small fields collimated by fixed cones, performed by a novel 2D monolithic silicon array detector, the Octa

Innovative detectors for quality assurance dosimetry in SBRT of stationary and movable targets

The high spatial and temporal resolution 2D monolithic silicon detector arrays M512 and DUO for quality assurance (QA) in real time motion adaptive radiotherapy (ART) have been developed. The DUO array possesses a spatial resolution of 0.2 mm and has demonstrated agreement within 5% with EBT3 film measurements of 6MV linac beam profiles for field sizes 1 × 1 cm2 and SRS cone diameter 0.5 cm. Dynamic characterisation of the M512 for QA in real time ART evaluated the performance of M512 for small fields while the detector experiences periodic motion. It was demonstrated with M512 that MLC tracking with Calypso electromagnetic array compensates for the periodic motion and improves the agreement between static and dynamic beam profiles for field size 1 × 1 cm2 from within 75% in the penumbra to within 11% agreement. The dynamic profile is returned to a similar distribution as the static case