Search

Patient safety, workflow efficiency, and adhering to time constraints are imperative challenges in brachytherapy treatment. A novel mobile cone beam computed tomography (CBCT) imaging device (IRm, Elekta, Veenendaal, Netherlands), recently adopted for brachytherapy, can effectively improve these difficulties. Its compact size and mobility offer a safe, efficient, and quick method for imaging gynecological cases. This is the first study investigating the image quality and workflow required for GYN brachytherapy employing the mobile imaging ring. Commissioning of the device was carried out using CIRS HDR GYN phantom (Sun Nuclear Corp., Melbourne, Florida) and Venezia CT/MR applicator (Elekta) and end-to-end (E2E) testing was performed to determine appropriate clinical workflow and quality assurance procedure. The phantom is designed with contiguous tissue-like composition and material compatible with water making it ideal in brachytherapy simulations. Venezia CT/MR compatible gynecological applicator (15 degree, 70mm tandem, 22mm dia left and right lunar ovoids, and left vaginal cap) was inserted into the phantom. A 50mm Smit Sleeve, was added for applicator placement reproducibility and can be seen in Figure 1 C). The sleeve's tip was cut before insertion to distinguish between sleeve and tandem. For added complexity and completeness, four interstitial needles were implanted 5 cm deep, with 2 needles passing through the left lunar ovoid, and 2 needles in the left vaginal cap. Marker cables were inserted in select applicator channels and needles for position verification. The IRm system provided anterior/posterior (AP) and lateral orthogonal topo scans to determine proper field of view (FOV) and phantom positioning within the ring gantry and a CBCT was acquired. CBCT (Elekta ImagingRing v 2.5.2) images were acquired using 120 kVp, 3 mA, voxel size of 0.6 x 0.6 x 1.2 mm and CT-Sim (Siemens SOMATOM go.Open Pro) using department standard pelvis imaging protocol (120 kVp, voxel size 1.17 x 1.17 x 1 mm, 0.8 pitch). CBCT images were registered to CT images to assess both image quality and applicator geometry accuracy of CBCT relative to CT. A Venezia ring and tandem applicator, including 4 interstitial needles, were implanted in the GYN phantom. 2D and 3D volumetric images were acquired using CBCT and CT. Both image sets were reconstructed using metal artifact reduction algorithms. Artifacts were more pronounced in CBCT compared with CT images. Anatomical landmarks were identified in CBCT images and fused to CT using rigid registration in MIM. Registration of CBCT images to CT demonstrated agreeable distal dwell position (<1 mm) offering good verification of applicator placement and image quality was determined to be appropriate for efficient brachytherapy planning. Applicator models were employed in Oncentra as well as catheter reconstruction of needles and a simulated HDR treatment fraction was created for both CT and CBCT image sets demonstrating IRm to be an appropriate tool for brachytherapy treatment planning. E2E testing of the Venezia brachytherapy program was performed, along with implementation of an IRm to improve clinical workflow and patient safety using CIRS HDR GYN phantom. Given the versatility and complexity of the Venezia applicator, it provides a valuable layer of accuracy for QA implementation in a clinical brachytherapy setting. Adding IRm to brachytherapy suite improves patient safety and comfort, efficiency of HDR treatment, and sim time as there will be no need to transfer the patient from CT to the treatment room. The combination of equipment used in this work allows a reliable and detailed procedure to be constructed for brachytherapy specific QA tasks and doubles as a means of training residents, students, or other physicists within the clinic. [ABSTRACT FROM AUTHOR]