Coordinate system of the RADPOS system.
PMMA phantom (distances are in cm), d is a variable distance between 2 and 4 cm. The source moves in the colpostats (C1 and C2) and tandem (T). r and θ are the distance and angle between one of the source positions and the detector.
Typical dose distribution during a GYN treatment and position of the measurement points.
Error on the position along the x-axis (a) and along the y-axis if the sensor is parallel to the x-axis (b) or perpendicular (c); error on the position along the x-axis in a PMMA phantom (d). Error bars are the standard deviation on repeated measurements. Dashed lines show the manufacturer’s recommended spatial range for the sensor.
MC calculated192Ir normalized photon spectra at different distances in PMMA (a) and energy absorption coefficients in water and SiO2 (b).
Variation of the MOSFET response with distance for two detectors, normalized to 1 cm distance. The mean photon energies in PMMA are given for distance of 1, 6, and 10 cm.
Radial dose function in PMMA (a) and anisotropy function at 0.5 cm (b) in water. Data in water are shown for comparison (Ref. 24).
Results of the dose measurements in the PMMA phantom. The third column presents the predicted TG43 dose to water in PMMA modified to take into account the mean photon energy. The values in brackets give the range of the measurements.
Simulation of organ motion in a phantom. The RADPOS detector is at a position simulating the Foley balloon. The detector is moved by up to 4 mm away from three different reference positions. The differences between the dose measured during the translation of the source in each catheter in the reference conditions and the same delivery when the motion is applied are reported. Numbers in bold signify that the error would be detected.
Simulation of source position error. Differences are between the dose delivered with the error on the position of the tip and the dose delivered if the treatment is correct.
Simulation of the effect of errors on the delivery times in the tandem on the dose to the MOSFET.
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