Characterization of the on-board megavoltage imager in a magnetic resonance-guided radiotherapy machine for beam output checks.

We characterized the on-board megavoltage imager (MVI) of a magnetic resonance-guided radiotherapy machine for beam output checks. Linearity and repeatability of its dose response were investigated. Alignment relative to the beam under clinical circumstances was evaluated for a year using daily measurements.

Dosimetric impact of contouring and image registration variability on dynamic I prostate brachytherapy.

Purpose: The quality of permanent prostate brachytherapy can be increased by addition of imaging modalities in the intraoperative procedure. This addition involves image registration, which inherently has inter- and intraobserver variabilities. We sought to quantify the inter- and intraobserver variabilities in geometry and dosimetry for contouring and image registration and analyze the results for our dynamic I brachytherapy procedure.

Cone-beam CT-based adaptive planning improves permanent prostate brachytherapy dosimetry: An analysis of 1266 patients.

Purpose: To evaluate adaptive planning for permanent prostate brachytherapy and to identify the prostate regions that needed adaptation.

Methods And Materials: After the implantation of stranded seeds, using real-time intraoperative planning, a transrectal ultrasound (TRUS)-scan was obtained and contoured. The positions of seeds were determined on a C-arm cone-beam computed tomography (CBCT)-scan.

Edema and Seed Displacements Affect Intraoperative Permanent Prostate Brachytherapy Dosimetry.

Purpose: We sought to identify the intraoperative displacement patterns of seeds and to evaluate the correlation of intraoperative dosimetry with day 30 for permanent prostate brachytherapy.

Methods And Materials: We analyzed the data from 699 patients. Intraoperative dosimetry was acquired using transrectal ultrasonography (TRUS) and C-arm cone beam computed tomography (CBCT).

An automated, fast and accurate registration method to link stranded seeds in permanent prostate implants.

The geometry of a permanent prostate implant varies over time. Seeds can migrate and edema of the prostate affects the position of seeds. Seed movements directly influence dosimetry which relates to treatment quality.

High-dose-rate prostate brachytherapy based on registered transrectal ultrasound and in-room cone-beam CT images.

Purpose: To present a high-dose-rate (HDR) brachytherapy procedure for prostate cancer using transrectal ultrasound (TRUS) to contour the regions of interest and registered in-room cone-beam CT (CBCT) images for needle reconstruction. To characterize the registration uncertainties between the two imaging modalities and explore the possibility of performing the procedure solely on TRUS.

Methods And Materials: Patients were treated with a TRUS/CBCT-based HDR brachytherapy procedure.

Objective automated assessment of time trends in prostate edema after (125)I implantation.

Purpose: To present an objective automated method to determine time trends in prostatic edema resulting from iodine-125 brachytherapy.

Methods And Materials: We followed 20 patients, implanted with stranded seeds, with seven consecutive CT scans to establish a time trend in prostate edema. Seed positions were obtained automatically from the CT series.

Intraoperative adaptive brachytherapy of iodine-125 prostate implants guided by C-arm cone-beam computed tomography-based dosimetry.

Purpose: (1) To demonstrate the feasibility of C-arm cone-beam computed tomography (CBCT)-based postplanning and subsequent adaptation of underdosed critical areas by adding remedial seeds during the transrectal ultrasound (TRUS)-guided implantation of (125)I seeds and (2) to assess the duration of this procedure.

Methods And Materials: After finishing the implant, three fiducial markers were implanted and a TRUS study was performed to delineate the prostate. A C-arm CBCT unit with isocentric design was used to generate a CT data set to localize the seeds.

Routine individualised patient dosimetry using electronic portal imaging devices.

Background And Purpose: To analyse the results of routine EPID measurements for individualised patient dosimetry.

Materials And Methods: Calibrated camera-based EPIDs were used to measure the central field dose, which was compared with a dose prediction at the EPID level. For transit dosimetry, dose data were calculated using patient transmission and scatter, and compared with measured values.

Clinical implementation of MOSFET detectors for dosimetry in electron beams.

Background And Purpose: To determine the factors converting the reading of a MOSFET detector placed on the patient's skin without additional build-up to the dose at the depth of dose maximum (D(max)) and investigate their feasibility for in vivo dose measurements in electron beams.

Materials And Methods: Factors were determined to relate the reading of a MOSFET detector to D(max) for 4 - 15 MeV electron beams in reference conditions. The influence of variation in field size, SSD, angle and field shape on the MOSFET reading, obtained without additional build-up, was evaluated using 4, 8 and 15 MeV beams and compared to ionisation chamber data at the depth of dose maximum (z(max)).

A Monte Carlo based three-dimensional dose reconstruction method derived from portal dose images.

The verification of intensity-modulated radiation therapy (IMRT) is necessary for adequate quality control of the treatment. Pretreatment verification may trace the possible differences between the planned dose and the actual dose delivered to the patient. To estimate the impact of differences between planned and delivered photon beams, a three-dimensional (3-D) dose verification method has been developed that reconstructs the dose inside a phantom.