In the Radiotherapy Centre of the National Institute of Oncology, Budapest, a 0.55
T MR scanner (MAGNETOM Free. Max) and a ring-like X-ray machine (ImagingRing) have
been in operation since 2022. The MR scanner has a tunnel diameter of 80 cm, the X-ray
machine has a ring diameter of 121 cm. The latter can also be used for cone-beam CT
(CBCT) imaging. The MR scanner is mainly used for planning gynaecological brachytherapy
(BT) treatments. Image distortions in MR imaging were investigated with a special
grid phantom. After head and neck and breast implant, image quality of ImagingRing
CBCT and planning CT was compared. The position of the radiation source was verified
by radiographs taken during treatment. Despite the lower field strength, the image
quality of the MR scanner was found to be adequate for treatment planning of gynaecological
BT. Image distortions were found to be clinically negligible. On CBCT images obtained
with ImagingRing, catheters could always be well identified, and anatomical organs
were adequately visualized for head and neck treatments, but not for breast implants.
The MR scanner is suitable for treatment planning for gynaecological BT due to its
good image quality and low image distortion. The image quality of the ImagingRing
is suitable for treatment planning for small body sizes, but not for larger sizes.
The device can be used to in vivo check of the radiation source position during treatment.
