Dosimetric evaluation of a newly designed low dose rate brachytherapy applicator for treatment of cervical cancer with extension into the lower vagina

Abstract

Currently, patients having cervical cancer with extension into the lower vagina are being treated with a combination of the Fletcher-Suit applicator, which treats the cervix, and a vaginal cylinder, which treats the lower vagina. With this method, patients receive two separate implants - a procedure that creates greater uncertainty in the dose distribution and unnecessary patient inconvenience. To reduce the uncertainty of the dose delivery and to eliminate patient inconvenience, a new applicator was designed and fabricated at the University of Kentucky for treatment of cervical cancer extending into the lower vagina. In addition, the geometric design of the new device allows for treatment of cervical cancer without extension into the lower vagina and simultaneously provides advantages relative to the commonly used Fletcher-Suit applicator. The dosimetric characteristics of this new applicator (hereafter called Meigooni applicator) were determined using experimental procedures. The measurements were performed using tissue-equivalent phantom material (Solid Water: Gammex RMI, Middleton, WI) that was machined to accommodate the applicator and LiF thermoluminescent dosimetry chips. The applicator was loaded with 137Cs brachytherapy sources in a standard loading scheme. A similar experimental procedure was performed using the currently available Fletcher-Suit mini-ovoid applicator. The results obtained with each applicator were compared with the values calculated by two commercially available treatment planning systems. The experiments showed that the Meigooni applicator allows for safe single treatment of cervical cancer that has extended into the lower vagina, eliminating the need for two separate treatment techniques. Moreover, the Meigooni applicator can function as an alternative to the Fletcher-Suit applicator for the treatment of patients with cervical cancer. © 2007 Am. Coll. Med. Phys.