Back to Top1. Introduction

Back to TopTable of Contents

1. Introduction
2. Intracavitary Implants
   • Preparation for Intracavitary Implants
   • Type of Intracavitary Implants at CET
   1. CET's Multichannel Vaginal Cylinder
   2. CET's Demanes-Rodriguez Tandem and Ovoids Applicator
3. Interstitial Implants
4. Consideration

Back to Top2. Intracavitary Implants

Intracavitary implants differ by the type of applicator used. The applicators are specially designed to deliver the radiation according to the tumor site. Patients treated with intracavitary applicators receive 3 to 6 treatments, delivered on an out-patient basis.

Preparation for Intracavitary Implants

On the evening before an applicator insertion, the patient is requested to have a light dinner (broth, jello) and not to eat or drink after midnight. A little water is permissible to take medications. The patient performs a Fleet enema the night before and the morning of the insertion. At the clinic, the patient lies supine (on the back) on the padded treatment couch in the treatment position with feet in stirrups. The nurse will administer conscious sedation to relax the patient, if necessary. Local anesthetic may also be given at the beginning of the insertion. The nurses gently wash the perineal and genital area. Sterile drapes are placed around the vaginal area. Catheters are inserted into the bladder and rectum for the introduction of contrast liquid. This contrast is necessary to visualize the bladder and rectum on radiographs so that radiation doses to these structures can be calculated.

CET Offers 2 Types of Intracavitary Implants

1. CET's Multichannel Vaginal Cylinder
2. CET's Demanes-Rodriguez Tandem and Ovoids Applicator

Back to Top2.1 CET's Multichannel Vaginal Cylinder

Fig 1: CET's Multichannel Vaginal Cylinder Applicator Setup

Postoperative brachytherapy may be needed following a hysterectomy for endometrial (uterine) cancer. Treatment is delivered with brachytherapy to the upper vaginal area, an area at high risk for recurrence. The CET vaginal cylinder is a smooth, plastic cylinder, measuring a little over 1 inch in diameter. It has 7 channels through which the radioactive source can travel. The multichannel cylinder allows for greater dose control and radiation dose shaping than the central channel only cylinder. CET published a study (The Use and Advantages of a Multichannel Vaginal

Cylinder in High-Dose-Rate Brachytherapy, Int. Journal Radiation Oncology, Biology, Physics, 1999 Vol.44, pps 211-219) which demonstrated the multichannel cylinder can reduce bladder and rectal doses by 15% more than the commonly used central channel cylinder. The physician inserts the cylinder and secures it in position. Special x-ray films are taken that show the cylinder in relationship to the surrounding organs. Using these films, a computerized treatment plan is then created by the dosimetrist, who tailors the radiation doses to treat the areas at risk to the prescribed doses while sparing the nearby normal structures from excessive radiation dose. Only after the plan is reviewed and approved by the physician is the treatment given. The radioactive source travels in and out of the 5 to 7 channels in the cylinder, delivering the radiation dose according to the approved treatment plan. The treatment takes approximately 30-90 minutes depending upon the size and complexity of the implant and the activity of the source. After the treatment, the vaginal cylinder, bladder and rectal catheters are removed. The nurses make sure the patient has recovered from any sedation before the patient leaves the clinic.

Back to Top2.2 CET's Demanes-Rodriguez Tandem and Ovoids Applicator

Fig 2 : Demanes-Rodriguez Tandem and Ovoids Applicator Setup

Brachytherapy for early stage cervix cancer is delivered using an applicator called a tandem and ovoids. Prior to the first treatment is the intraoperative placement of a Smitt sleeve. The Smitt sleeve is a hollow plastic tube, custom fitted to the uterine cavity. It is inserted through the cervical opening into the uterus then sutured in place onto the cervix. This sleeve stays in the uterus for the duration of the treatments. The purpose of the Smitt sleeve is to keep the cervix open which

allows for comfortable and reproducible positioning of the tandem. The tandem is a hollow metal tube that is inserted into the Smitt sleeve. The two ovoids are positioned on either side of the cervix. There are tiny radiation shields in the ovoids that reduce the radiation doses to the bladder and rectum. CET's applicator also has a rectal retractor that pushes the rectum away from the applicator, further reducing rectal doses. After placement of the applicator, special x-ray films are taken for the treatment planning calculations. After the treatment plan has been approved by the physician, the treatment is given. Following each treatment, the tandem and ovoids, and bladder and rectal catheters are removed. Generally, six treatments are given, twice weekly. After the final treatment, the the Smitt sleeve is removed.

Back to Top3. Interstitial Implants

Fig 3: Interstitial Implants: dummy radiation source appears as a dotted line.

Interstitial implants are required for more advanced stage gynecologic malignancies. Generally, two implants are performed, a week apart, with each implant receiving two to three HDR treatments. The implants are done under spinal anesthesia in the operating room. Hollow plastic catheters are inserted through the perineum, guided with ultrasound, fluoroscopy and endoscopy, to fully encompass the tumor.

The catheter placement is secured by a rubber template which is sutured against the perineum. The patient is transferred to the recovery room and following recovery, transported to our clinic for the simulation radiography, computerized treatment planning and treatment. After the first treatment, the patient goes to her hospital room, stays overnight, and the next one or two treatments are given the next day. After the last treatment, the implant is removed and the patient is discharged with home care instructions. The procedure is repeated for the second implant. Expected side effects from interstitial brachytherapy for gynecologic malignancy include a temporary increase in urinary frequency, some burning with urination, and possibly blood-tinged urine for 2-3 days following implant removal. Bowel function may also be affected by radiation, antibiotics and pain medications. Perineal or pelvic discomfort is treated with oral pain medication as needed and sitz baths. Possible long term side effects are related to the radiation dose delivered to surrounding organs and will be discussed with the patient at the time of consultation.

Back to Top4. Consideration

High dose rate brachytherapy allows precise delivery of the radiation dose prescribed by the physician. The ability to shape the radiation doses to maximize tumor dose and minimize dose to surrounding normal tissues is a great advantage over low dose rate methods and excellent tumor control rates and low side effect rates are being realized in our clinic. The short treatment times, outpatient visits, and accurate radiation delivery are all advantages of the HDR system.