Pilot study of a computed tomography-compatible shielded intracavitary brachytherapy applicator for treatment of...

The traditional Fletcher-Williamson tandem and ovoid brachytherapy applicators for treatment of cervical cancer have ovoid shields that reduce the dose to the bladder and rectum. However, these shields produce artifact on computed tomography (CT) that prevents acquisition of high-quality images. To address this limitation, we designed and tested a novel CT-compatible applicator with movable shields, called MDA(3).

Fifteen patients with stage IB1-IIB cervical cancer requiring definitive radiation therapy were enrolled in a prospective pilot study to evaluate image quality with the MDA(3). Image quality was assessed by comparing an initial scan obtained with the shields shifted to minimize shield artifact to a second scan obtained with the shields in treatment position. The 2 scans were then compared by a radiation oncologist blinded to the image source. In addition, image quality was assessed by analysis of Hounsfield values in the normal tissues.

The MDA(3) was successfully employed for intracavitary brachytherapy in 15 patients. CT images obtained with the shields shifted were superior to CT images obtained with the shields in treatment position in every case as evaluated by the radiation oncologist (P < .0001). The presence of the shields in the treatment position significantly increased the mean Hounsfield values within the bladder (P = .002) and rectum (P = .001) due to high-density image artifact.

This novel applicator provides a clinically feasible solution to overcome the limitation of lack of ovoid shields on currently available CT-compatible applicators.