Optimized method for in vivo dosimetry with small films in pelvic IOERT for rectal cancer.

Purpose: Intra-Operative Electron Radiation Therapy (IOERT) is used to treat rectal cancer at our institution, and in vivo measurements with Gafchromic EBT3® films were introduced as quality assurance. The purpose of this work was to quantify the uncertainties associated with digitization of very small EBT3 films irradiated simultaneously, in order to optimize in vivo dosimetry for IOERT.

Methods: Film samples of different sizes - M1 (5×5cm), M2 (1.

Automatic calculation of patient size metrics in computed tomography: What level of computational accuracy do we need?

Objectives: To compare the effectiveness of two different patient size metrics based on water equivalent diameter (D ), the mid-scan water equivalent diameter D , and the mean (average) water equivalent diameter in the imaged region, D , for automatic detection of accidental changes in computed tomography (CT) acquisition protocols.

Methods: Patient biometric data (height and weight) were available from a previous survey for 80 adult chest examinations, and 119 adult single-acquisition chest-abdomen-pelvis (CAP) examinations for two 16 slice scanners (GE LightSpeed and Toshiba Aquilion RXL) equipped with automatic tube current modulation (ATCM). D and D were calculated from the archived CT images.

The use of needle holders in CTF guided biopsies as a dose reduction tool.

Purpose: The purpose of this study was to evaluate the efficacy of needle holders in reducing staff hand exposure during biopsies guided by computed tomography fluoroscopy (CTF), through the analysis of data acquired during a detailed monitoring study, undertaken in parallel with an ongoing optimization process to reduce hand irradiation.

Methods: Hand monitoring was performed with 11 extremity detectors, two per finger (base and tip) and one on the back of the wrist, for the left (dominant) hand, during two series of biopsies with comparable characteristics. The first series (47 biopsies) were performed with only quick-check method (QC) and occasional side-handle (SH) manipulation of the needle.

Effects of shielding on pelvic and abdominal IORT dose distributions.

Purpose: To study the impact of shielding elements in the proximity of Intra-Operative Radiation Therapy (IORT) irradiation fields, and to generate graphical and quantitative information to assist radiation oncologists in the design of optimal shielding during pelvic and abdominal IORT.

Method: An IORT system was modeled with BEAMnrc and EGS++ Monte Carlo codes. The model was validated in reference conditions by gamma index analysis against an experimental data set of different beam energies, applicator diameters, and bevel angles.

In vivo dosimetry using Gafchromic films during pelvic intraoperative electron radiation therapy (IOERT).

Objective: To characterize in vivo dose distributions during pelvic intraoperative electron radiation therapy (IOERT) for rectal cancer and to assess the alterations introduced by irregular irradiation surfaces in the presence of bevelled applicators.

Methods: In vivo measurements were performed with Gafchromic films during 32 IOERT procedures. 1 film per procedure was used for the first 20 procedures.

Gafchromic XR-QA2 film as a complementary dosimeter for hand-monitoring in CTF-guided biopsies.

Computed tomography fluoroscopy (CTF) is a useful imaging technique to guide biopsies, particularly lung biopsies, but it also has the potential for very high hand exposures, despite use of quick-check method and needle holders whenever feasible. Therefore, reliable monitoring is crucial to ensure the safe use of CTF. This is a challenge, because ring dosimeters monitor exposure only at the base of one finger, while the fingertips may be exposed to the highly collimated CT beam.

Erratum: Attenuation measurements show that the presence of a TachoSil surgical patch will not compromise target irradiation in intra-operative electron radiation therapy or high-dose-rate brachytherapy.

After publication of this study [1], the authors noticed that the funding was incorrectly acknowledged. The correct Acknowledgements section can be found below: “This work was partly funded by Fundação para a Ciência e Tecnologia (FCT), in the framework of the project PTDC/SAU-ENB/117631/2010, which is cofinanced by FEDER, through Programa Operacional Fatores de Competitividade - COMPETE of QREN (reference FCOMP-01-0124-FEDER-021141).”

Assessment of clinically relevant dose distributions in pelvic IOERT using Gafchromic EBT3 films.

Purpose: In IOERT a single dose of radiation is delivered to the tumour site during surgery. Manual dose calculations are used and the irradiation target volume, electron energy and applicator are decided on site by the radiation oncologist. This work assesses the effect that irregular and curved surfaces, typical of pelvic IOERT, may have on the expected dose distribution.

Attenuation measurements show that the presence of a TachoSil surgical patch will not compromise target irradiation in intra-operative electron radiation therapy or high-dose-rate brachytherapy.

Background: Surgery of locally advanced and/or recurrent rectal cancer can be complemented with intra-operative electron radiation therapy (IOERT) to deliver a single dose of radiation directly to the unresectable margins, while sparing nearby sensitive organs/structures. Haemorrhages may occur and can affect the dose distribution, leading to an incorrect target irradiation. The TachoSil (TS) surgical patch, when activated, creates a fibrin clot at the surgical site to achieve haemostasis.

Kinetics of the atrazine degradation process using H2O2-UVC.

This work is concerned with the intrinsic reaction kinetic of the degradation of atrazine (ATZ) using H2O2-UVC. Experimental runs were carried out in annular photoreactor. The initial concentration of ATZ was 2.