Room: AAPM ePoster Library
The advanced gynaecological applicator (AGA) (Elekta, Sweden) designed for image-guided interstitial brachytherapy can cover the tumor for most patients. However, when advanced tumor extends to paravaginal tissue lateral to the level of lunar ovoids or to distal parametrium, the coverage of the target will be suboptimal due to the fixed design of needles. Therefore, perineal needles will be required, but it is highly difficult to travel a long distance to reach the tumor. 3D printing allows us to design and create a template to attach onto AGA to overcome the difficulty.
A cervical cancer patient with distal left parametrium involvement to the side wall 4cm from midline at brachytherapy, which cannot be well treated by AGA. A template was designed using Fusion 360 software (Autodesk, USA) to attach to AGA, allowed an extra layer of straight and oblique needles outside of the applicator, which could be fixed by attaching to the lunar ovoid tubes. The extra layer of straight needles was 5mm radially away from straight needles of the applicator. Meanwhile, the extra layer of oblique needles was located 5mm radially parallel to oblique needles and to be inserted 1cm below the lunar ovoids through the vagina. The design decreased the distance of the needles to reach the tumor when compared with the perineal needle.
After applying the template, the dose to 90% of high risk clinical target volume (HRCTV) increased from 6.8Gy to 8.3Gy per fraction while keeping the dose to bladder, rectum and sigmoid constant that within the respective dose constraints.
The template improves the coverage to advanced tumors and the parameters such as the insertion angle of oblique needles, the needle positions or the separation between needles in the template can be modified according to patient’s need as it can be easily amended.