ESTRO 2022 - Abstract Book

S1658

Abstract book

ESTRO 2022

At a distance of 3m from the axis of the radiation beam and at a 6cm plaster wall, a general population may spend 262 minutes per year. For one treatment, which takes about 1 minute, we have 262 operations per year. For B-category, this number is 1576, and for A-category-5253. For rooms located above the operating room, a person from the general population may stay in the area of the beam axis for more than 410 minutes, category B-2462 minutes, and for category A- 8207 minutes. Conclusion The analysis of air kerma measurements confirmed the assumptions that the AQURE mobile intraoperative accelerator is a safe device and can be used without additional covers during surgery in ordinary operating rooms. However, the placement of the device in the operating room must be taken into account when planning accelerator procedures. Following a risk analysis, recommendations were proposed for users and staff responsible for radiological safety in the operating room using the AQURE mobile intraoperative accelerator. These recommendations are indicative only and should be updated following environmental research at the target facility where the AQURE mobile intraoperative accelerator will be used.

Poster (digital): RTT treatment planning, OAR and target definitions

PO-1871 Viscous Aqueous Gel Illustrating Natural Anatomy; the VAGINA method in gynaecological MRI simulation

K. Skehan 1 , M. Richardson 1 , K. Martin 1 , S. Dickson 2 , G. Govindarajulu 1 , S. Sridharan 1

1 Calvary Mater Newcastle, Radiation Oncology, Newcastle, Australia; 2 Calvary Mater Newcastle, Radiaiton Oncology, Newcastle, Australia Purpose or Objective Accurate anatomical identification is critical in gynaecological radiotherapy (RT). In our departmental clinical practice, gynaecological patients have received two CT scans at simulation; one full bladder scan and one empty bladder scan with tampon in-situ. This was complimented with a full and empty bladder sagittal and axial T2-weighted MRI scan. Diagnostic MRI exams have generated vaginal opacification using ultrasound gel to distend and delineate the vagina due to its low viscosity and high signal on T2 weighting. This is not recommended for gynaecological RT planning scans, as a distended vaginal volume is not accurately reproduced at treatment. Fusion of planning CT and MRI scans led us to ponder if tampons do not reveal the true shape and extent of the anatomy. We theorised a method to improve visualisation of the true extent of the vaginal vault, without deforming the natural anatomy using MRI simulation for RT planning. Materials and Methods We modified the diagnostic opacification technique for use in MRI simulation with the alternative goal of delineation and visualisation without distension. The standard diagnostic 60cc of ultrasound gel, considered the correct amount for distension, was then tested in varying lesser amounts. Aquasonic 100® ultrasound transmission gel was warmed to 36 ᵒ C and delivered vaginally on the MRI couch by a Radiation Oncologist using a sterile 50ml catheter tip syringe pre imaging. During testing both CT + tampon and MRI + vaginal gel simulation scans were acquired for comparative qualitative imaging.

Results After trialling varying volumes of ultrasound gel, 10-15cc was found to be optimal for most patients (Fig. 1).