Estimation of neutron-equivalent dose in organs of patients undergoing radiotherapy by the use of a novel online digital detector

Abstract

Neutron peripheral contamination in patients undergoing high-energy photon radiotherapy is considered as a risk factor for secondary cancer induction. Organ-specific neutron-equivalent dose estimation is therefore essential for a reasonable assessment of these associated risks. This work aimed to develop a method to estimate neutron-equivalent doses in multiple organs of radiotherapy patients. The method involved the convolution, at 16 reference points in an anthropomorphic phantom, of the normalized Monte Carlo neutron fluence energy spectra with the kerma and energy-dependent radiation weighting factor. This was then scaled with the total neutron fluence measured with passive detectors, at the same reference points, in order to obtain the equivalent doses in organs. The latter were correlated with the readings of a neutron digital detector located inside the treatment room during phantom irradiation. This digital detector, designed and developed by our group, integrates the thermal neutron fluence. The correlation model, applied to the digital detector readings during patient irradiation, enables the online estimation of neutron-equivalent doses in organs. The model takes into account the specific irradiation site, the field parameters (energy, field size, angle incidence, etc) and the installation (linac and bunker geometry). This method, which is suitable for routine clinical use, will help to systematically generate the dosimetric data essential for the improvement of current risk-estimation models.

Study of Thermal Neutron Flux and Generated Energy from Linac using CR-39 Detector in Liquid Medium

“…Saat penyinaran pada fantom air, terjadi interaksi antara neutron cepat dengan air (H2O) yang mengakibatkan penurunan energi neutron cepat dari awal penyinaran, kemudian neutron mengalami termalisasi menjadi neutron termal. Neutron termal yang terbentuk dari reaksi ini kemudian akan mengurangi jumlah neutron termal yang berinteraksi dengan detektor, sehingga jejak yang terbaca lebih sedikit [9].…”

Estimation of Effective Dose Out of Fields in LINAC Radiotherapy Variant iX for Cervical Cancer

“…Berdasarkan penelitian Sanchez [5], maka dalam penelitian ini difokuskan hanya pada daerah abdomen dekat dengan target. Dalam tulisan ini akan dipaparkan estimasi out of field doseyang diterima organ-organ kritis di sekitar target dari pesawat LINAC yang dioperasikan pada energi 15 MV melalui pengukuran.…”

Improving the neutron-to-photon discrimination capability of detectors used for neutron dosimetry in high energy photon beam radiotherapy

“…2). Results from these measurements are routinely used for peripheral neutron dose estimations, using the methodology established in Sánchez-Doblado et al (2012). Negligible photon contribution to TNRD reading was expected at this location.…”

“…These doses have two main components: leakage/scattered photons and neutron contamination. Since dosimetric methods for photon doses are well-known Taddei et al, 2013), our group has focused on the neutron component, and established a methodology to estimate peripheral neutron doses (Sánchez-Doblado et al, 2012;Expósito et al, 2013;Romero-Expósito et al, 2015;VazquezLuque et al, 2013). Although this procedure was developed for a particular thermal neutron detector (Gómez et al, 2010), could be applicable to any other (Guardiola et al, 2013;Bedogni et al, 2014).…”

“…Although this procedure was developed for a particular thermal neutron detector (Gómez et al, 2010), could be applicable to any other (Guardiola et al, 2013;Bedogni et al, 2014). Specifically, one of these detectors, named TNRD (Thermal Neutron Rate Detector), designed and developed by Bedogni et al, was characterized for peripheral neutron dose measurements in radiotherapy environments, according to the methodology described in Sánchez-Doblado et al (2012). The TNRD showed satisfactory performances in terms of user friendliness and high sensitivity (Irazola et al, 2014).…”