Transabdominal Ultrasound Guidance Versus Magnetic Resonance Image Guided Brachytherapy for Cervical Cancer, A comparative study.

Summary: MRI-based image-guided brachytherapy is associated with improved local control for cervical cancer. Many centers in rural USA do not have access to MRI for brachytherapy. US is used for guiding applicator placement but has not been widely adopted for planning. US presents time and cost benefits, may be an alternative to MRI guided planning. Our study compares HR-CTV dimensions on a single sagittal TAUS image to a T2 MRI sagittal image at midplane as an attempt to evaluate feasibility of utilizing US for brachytherapy planning. All patients with CA cervix treated with chemo-RT with MRI based planning between 2019- 2024 were identified. Sagittal TA US images during tandem insertion and post-insertion T2- MRI images from first HDR session were acquired. The HR-CTV was defined on the sagittal 2D image obtained from the US and MRI by two observers (1 resident, 1 attending). The maximum HR-CTV width in the AP and SI directions were measured on sagittal planes after fusing the images. The mean differences in the dimensions between the groups were compared 17 patients were identified for the study. US images were imported into MIM; however, fusion of US and MRI images was possible for 11 patients due to significant motion artifacts that affected image quality. The HR-CTV delineation US and MRI images were done on 11 patients by the Resident and Attending physician separately. The mean difference in the width of HR-CTV in the AP and SI directions for MRI and US images for Resident were 0.10 and 0.15 cm and for Attending were 0.37 and 0.25 cm respectively Transabdominal US may be an alternative for delineating HR-CTV in cervical cancer. Many challenges were associated with processing of US images in radiation planning systems. Potential remedies are: 1. identifying a method of indexing the image set in space to create a 3D image set (e.g. transrectal US acquisition at 5mm intervals) 2. Acquiring 2D images along defined objects like the sagittal image along tandem. A prospective pilot study using transabdominal ultrasound for image-guided brachy planning is being developed Ranjani Padmanabhan (she/her/hers), Resident (Presenting Author) - New york Presbyterian Brooklyn Methodist Hospital; John McKenna, Physicist (Co-Author) - NYP Brooklyn Methodist; Onyinye Balogun, Physician (Co-Author) - NYP Brooklyn Methodist