6 Modern Imaging in Brachytherapy

140 Modern Imaging

Fig 5.11: CT guided brachytherapy (Somatom Plus, Siemens) for residual disease of a pelvic wall recurrence in a patient with cancer of the uterus as a boost treatment after 60 Gy to the pelvic wall and significant tumour shrinkage. Three round plastic needles with an obturator are forwarded by free hand technique retroperitoneally from the anterior lateral pelvic wall. For orientation transverse CT images are first taken, by which the position and the angle for the needle placement is determined (A). The needle is forwarded under the given angle a few cm and a control CT image is taken (B,C). The procedure is further supported by imaging, as appropriate for the precise positioning of the needles (D). At the end of the procedure transverse CT images are taken for the whole volume implanted and dose calculation is based on these images, which are directly introduced into the treatment planning system (E). (Three fractions of HDR brachytherapy were given in 24 hours with 6 Gy each to a total dose of 18 Gy with a treated volume of 15 cm 3 . No evidence of local tumour regrowth and of side effects 18 months after treatment with progressive disease at distant sites.)

A: CT image for orientation indicating the position and the angle for introducing the needle;

C: Two guide needles in place for orientation (right anterior pelvis, different patient, same procedure);

B: Needle placement at a computer tomograph (complete view);

D: CT image with 1 st and 2 nd plastic needle in place;