S19
Brachytherapy - Gastro-intestinal, paediatric brachytherapy, miscellaneous
ESTRO 2026
the prototype, surrounded by a 1cm bolus, was taken using the planning CT scan (Philips Brilliance Big Bore Circular Edition), and the obtained DICOM images were sent to the Treatment Planning System (Oncentra Brachy 4.6.0.16) for virtual dose planning. The target contour was delineated into the bolus we wrapped around the applicator, and a dose of 10 Gy was prescribed. Maximum target depth was 1 cm. Results: The applicator image we designed is given in Figure 1a. The outer diameter was 40.06 mm, the height was 127.85 mm, and the inner length was 250 mm. These dimensions were selected for easier production with a 3D printer. The image of the virtual dose plan generated using the treatment planning system is shown in Figure 1b. For the target dose of 10 Gy, the number of activated Dwell positions was 43 (intervals were 3 mm), and the calculated total irradiation time was 821.1 seconds. Total Reference Air Kerma (TRAK) was 0.00657 Gy. D100, D98, D95, and D90 for the target volume were 9.03, 10.33, 10.82, and 11.28 Gy, respectively. D2cc for the delineated structure as “opposite rectal wall” was 6.33 Gy.
cases. Pnemonitis in the months following HDR- brachytherapy was classified as grade 1, 2 and 3 in 26 (57%), 4 (9%) and 3 (7%), in 19 cases in the first 3 months and 11 cases 3-8 months after HDR- brachytherapy. During follow-up, a pleural effusion was detected in 8 (17%) of cases, and a partial or complete lung atelectasis in 10 (22%) and 1 (2%) cases. Early changes include a spotted condensation in the majority of patients and ground glass opacity in about 40% of patients within the first six months. A partial atelectasis was observed in 10-20%, whereas a total atelectasis occurs only rarely (only a single patient in our patient population). A pleural effusion was diagnosed also in 10-20% of patients. The local control was 81% within the follow-up.In the period after 6 months, a streaky or dense condensation was noted in the majority of follow-up images. The lung tissue condensation progresses into a retraction with increasing follow-up intervals. A lung atelectasis occured in about 10% of patients. A pleural effusion was noted more rarely in comparison to the acute phase (<10% at all intervals). Conclusion: A single dose interstitial HDR-brachytherapy is an extremely conformal treatment with a high dose to a very small volume of the lung. It is associated with a risk of a pneumothorax. As a result of high focal doses of >100Gy in one fraction, a tissue condensation must be expected in all patients, with a progressive retraction predominantly in the second year after brachytherapy. There is a smaller risk of a partial atelectasis and pleural effusion. Keywords: brachytherapy; lung tumours; computed tomography Digital Poster 1106 Endorectal Helical Brachytherapy Applicator: A New Design Alaattin Ozen, Ezgi Melis Tufanyazici, Tugce Dursun Ucar, Tarik Bozlar Radiation Oncology, Basaksehir Cam ve Sakura City Hospital, Istanbul, Turkey Purpose/Objective: This project aims to design and produce a prototype of a helical (spiral) endorectal HDR brachytherapy applicator that can be used in patients diagnosed with rectal cancer, and to perform virtual dosimetric evaluation. Material/Methods: To meet the project objectives, a helical applicator was designed that allows the brachytherapy source to flow smoothly through it. The designed prototype was then fabricated from PLA (eSUN PLA+ 1.75 mm) material using a 3D printer (Original Prusa Mini+). A CT scan of
Figure 1a
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