Clinical results of entrance dose in vivo dosimetry for high energy photons in external beam radiotherapy using MOSFETs

Abstract

Thomson and Nielsen TN-502 RD MOSFETs were used for entrance dose in vivo dosimetry for 6 and 10 MV photons. A total of 24 patients were tested, 10 breast, 8 prostate, 5 lung and 1 head and neck. For prostates three fields were checked. For all other plans all fields were checked. An action threshold of 8% was set for any one field and 5% for all fields combined. The total number of fields tested was 56, with a mean discrepancy of 1.4% and S.D. of 2.6%. Breasts had a mean discrepancy of 1.8% and S.D. of 2.8%. Prostates had a mean discrepancy of 1.3% and S.D. of 2.9%. For 3 fields combined, prostates had a mean of 1.3% and S.D. of 1.8%. These results are similar to results obtained with diodes and TLDs for the same techniques.

Is the in vivo dosimetry with the OneDosePlusTM system able to detect intra-fraction motion? A retrospective analysis of in vivo data from breast and prostate patients

“…This means that the system is reproducible with respect to each TPS. This result is similar to those found in other institutions [5,24] using other measurement devices like different MOSFET or diode based dosimeters.…”

“…This part of the study was aimed at establishing an Action Threshold (AT) [5,24], defined as the maximum accepted discrepancy between the dose measured with the detector and the dose calculated with the TPS for a single field (in our procedure only one field at a time is verified). A single AT has been established, one specific for breast and one for prostate treatments, from the analysis of the tests in phantoms, and it has been used as an indicator of the correctness of breast and prostate treatments themselves.…”

Energy dependence corrections to MOSFET dosimetric sensitivity

“…As such, MOSFET detectors are finding applications in radiotherapy radiation dosimetry [9][10][11][12][13][14][15][16] . They have also been used commonly for in-vivo dosimetry [17][18][19] .…”

In-vivo dosimetry for conformal arc therapy using several MOSFET in stereotactic radiosurgery computed by an inverse model

“…The anisotropy of the MOSFET, as for other in-vivo dosimeters may be explained by the attenuation caused by the geometry of the detector and has been estimated at between 1% and 3 % from 0° to 180° for the most recent models TN-502-RD [17,28,29]. Therefore, when the angle of the beam is 0 ° to 25 ° on entry and between 0 ° to 30 ° at exit, the angular dependence may be considered as negligible.…”

“…Therefore, MOSFETs could be suitable for in-vivo assessment of radiosurgery microbeams [7,6,8]. In the literature their use has been described extensively for such in vivo procedures as: in vivo dosimetry for external radiotherapy [9,10,11], dose verification in intensity modulated radiotherapy (IMRT) [12,13,14], measurements in head and neck Tomotherapy [15], skin dose measurement [16], entry dosimetry [17], implantable detectors for in-situ testing during radiation therapy treatment [18], dose verification of permanent low-dose-rate implants [19] and as a dosimeter for imaging in radiological procedures [20]. Additional studies have reported excellent linearity, dosimetric accuracy in the build-up region and directional independence [9,21].…”