Thermal Boost to Breast Tumor Bed-New Technique Description, Treatment Application and Example Clinical Results.

(1) Current breast-conserving therapy for breast cancer consists of a combination of many consecutive treatment modalities. The most crucial goal of postoperative treatment is to eradicate potentially relapse-forming residual cancerous cells within the tumor bed. To achieve this, the HDR brachytherapy boost standardly added to external beam radiotherapy was enhanced with an initial thermal boost. This study presents an original thermal boost technique developed in the clinic. (2) A detailed point-by-point description of thermal boost application is presented. Data on proper patient selection, microwave thermal boost planning, and interstitial hyperthermia treatment delivery are supported by relevant figures and schemes. (3) Out of 1134 breast cancer patients who were administered HDR brachytherapy boost in the tumor bed, 262 were also pre-heated interstitially without unexpected complications. The results are supported by two example cases of hyperthermia planning and delivery. (4) Additional breast cancer interstitial thermal boost preceding HDR brachytherapy boost as a part of combined treatment in a unique postoperative setting was feasible, well-tolerated, completed in a reasonable amount of time, and reproducible. A commercially available interstitial hyperthermia system fit and worked well with standard interstitial brachytherapy equipment.

3D printing of individual skin brachytherapy applicator: design, manufacturing, and early clinical results.

Purpose: One of the main challenges in facial region brachytherapy is fixation of vendor-delivered standard applicators. Reproducibility can be maintained; however, there are frequent problems with applicator fitting to the skin surface in pleated regions. Manually prepared individual moulds require technological facilities and highly-trained staff. This article presents 3D-printed applicator preparation for a particular patient skin brachytherapy, using low-cost equipment and free software. We described applicator preparation in a step-by-step workflow. Material and methods: This study demonstrated preparation of a skin brachytherapy applicator for a challenging recurrent tumor located in the nose bridge. During first visit of patient, fiducial markers were placed to enclose treated region. Patient was computed tomography (CT)-scanned, and reconstruction of target volume and surrounding organs at risk (OARs) were performed using treatment planning system (TPS). In TPS on patient's surface, a 1-cm thick bolus was added as a body of applicator. Inside the bolus, source paths were designed, and pre-plan was prepared. Using Beben - DICOM to standard triangle language (STL) software, the body of applicator and source-paths from pre-planning was transformed into an STL file, which was used as a solid definition in 3D printing. Results: The printed applicator fitted very well, and its' placement was quickly consistent regarding placing and securing. CTV was slightly broader in treatment plan (0.34 cm3 vs. 0.31 cm3), and doses given to CTV were lower, except for V150, which was higher for the realized plan (1.15% vs. 1.83%). All reported doses to OARs were lower in the realized plan. Conclusions: A low-cost 3D printer and widely available PLA filaments seem feasible to produce individual contact applicators for skin brachytherapy. Beben - DICOM to STL software and presented workflow appear to be convenient and simple tool.

HDR and PDR 192Ir source activity control procedures, as the part of the quality assurance system at Brachytherapy Department of Greater Poland Cancer Centre.

PURPOSE: One of the main causes of treatment failures in brachytherapy is incorrect source strength specification in planning system or treatment delivery console. Source strength control is the only scheme to avoid such mistakes. The main aim of this work was to present results of three years of HDR and PDR sources activity control. MATERIAL AND METHODS: Study was based on data from 14 192Ir HDR and PDR sources exchanges. Sources were checked three times: at the exchange day and after one and two months. Measurements were performed twice with thimble chamber (PMMA phantom), and well chamber. The source strength were measured as air - kerma and recalculated to activity. RESULTS: Source activities measured using well chamber and thimble chamber, as well as activities provided by planning system, were presented for PDR and HDR, respectively. Differences between results obtained using each chamber and activities from planning system were presented graphically. The calculated and measured activities differed less than 5%. Wilcoxon test was performed as well, no statistically significant differences were observed among HDR or PDR activities. CONCLUSIONS: Checking of source parameters is one of the most important parts of quality control system in brachytherapy facilities. Well chamber and thimble chamber based dosimetry systems are fast and reliable tools for 192Ir source parameters checking in working brachytherapy department conditions.

Comparison and verification of the reconstruction method of the catheters for interstitial brachytherapy.

PURPOSE: 1. Comparison and verification of accuracy of the implant reconstruction method based on images from IBU and CT. 2. Estimation of influence of the implant reconstruction method on dose disposition in selected reference points. MATERIAL AND METHODS: Paraffin-wax phantom with three catheters, central marker and control point were prepared. IBU unit were used for obtaining two series of images for reconstruction. The Earth magnetic field correction algorithm was used to correct S-shape distortions of the images. CT images (1 mm slice) were prepared. In the treatment planning system positions of 15 catheter points (MP, measure points), control point (CP) and central marker (CM) were reconstructed for each series of images. Distances between 15 catheter points and control point, and between catheter points and central marker were calculated. RESULTS: There were no statistically significant differences observed for IBU and CT based reconstructions for all orientations of the phantom (p > 0.05, U-Mann Whitney Test). There were no statistically significant differences observed between reconstruction based on IBU images with and without Earth magnetic field correction algorithm for phantom located perpendicular to the IBU table (p > 0.05, Wilcoxon Test). Statistically significant differences were observed only for images set with long axis of the phantom located parallel to the table (p < 0.05, Wilcoxon Test). There were no statistically significant differences observed for values doses in reference points for reconstruction based on IBU images and CT for all orientations of the phantom. CONCLUSIONS: 1. Obtained results showed that IBU (radiographs based) reconstruction of the catheter placement is the reliable and accurate method for interstitial implants when reconstruction based on CT "catheter tracking" is not possible or not necessary. 2. The Earth magnetic field correction algorithm should be always use to correct S-shape distortions; reconstruction will be more accurate in particular orientations of image intensifier of the imaging unit.