Image Guided Brachytherapy
Image guided brachytherapy is a significant advance in the treatment of gynecologic malignancies but is highly technique dependent and is done best by centers that have a high volume of cases. Prior to image guided brachytherapy 2D images were taken with brachytherapy applicators and doses were prescribed to points.
In the images below for example on the right is an anterior-posterior view of a vaginal applicator inserted in the vagina. You can see the cylinder pushing up against the top of the vaginal apex. You can’t see the outline of the entire bladder and rectum but one way to approximate them is to place foley catheters in the bladder (yellow outline) and the rectum (brown outline) so they can be visualized.
An alternative to this is to use CT compatible applicators and to use CT imaging. The advantage of this is that CT imaging allows you to see the anatomy in more detail than on X-rays. For example, a CT image with a vaginal applicator in place looks like the following:
One can actually “see” the anatomy including the bladder (yellow) and rectum (brown). The cylinder is outlined in red. By being able to clearly see things we can more effectively optimize the radiation dose to the target and limit the dose to normal tissues.