Abstract：Objective In order to improve the accuracy of registration between CT simulated positioning image and conventional MRI scanning image, and improve the accuracy of delineation of radiotherapy target area, a set of CT-MRI simulative positioning device
for radiotherapy in the same body position was developed. Methods Design the device by measuring the relevant data which include the specification of CT simulation positioning fixture, bed surface size and aperture size of MRI scanner. Based on the measurement data, Kevlar, ABS plastic, and nylon screws were selected to manufacture CT-MRI orthotopic radiotherapy positioning device, which consists of a body MRI simulation positioning frame, a flat bed adapting bed plate for a concave bed, and an arch support frame of MRI body scanning coil. In the end, CT simulated positioning fixture and CT-MRI orthotopic radiotherapy positioning device were used to perform CT simulated positioning and MRI simulated positioning for patients respectively, to observe the registration and fusion effect of CT and MRI images. Results The CT-MRI orthotopic radiotherapy positioning device achieved the MRI simulation positioning scan successfully and safely. And the device can obtain better image registration and fusion results after 10 clinical trials. DICE: 0.988, HD: 3.340 mm; Non-isotopic head DIC: 0.947, HD: 6.445 mm. DICE in neck with the same body position: 0.847, HD: 3.803 mm; DICE in neck with non-consomatic position: 0.829, HD: 4.679 mm. Conclusion The CT-MRI orthotopic radiotherapy
positioning device satisfy clinical radiotherapy requirements, which can improve the precision of image registration effectively and improve the accuracy of the target delineation significantly.
