Patient Care

The Leksell Gamma Knife® Perfexion™ is an effective, non-invasive alternative to traditional brain surgery. This highly sophisticated technology directs precisely focused radiation to specific targets in the brain. Typically performed in a single outpatient treatment session without general anesthesia, the Gamma Knife helps patients avoid incision, scarring, and long hospital stays while minimizing surgical complications. For many conditions, Gamma Knife Perfexion treatment is the most accurate form of stereotactic radiosurgery available. 192 beams of Cobalt 60 radiation are delivered through the intact skull to a small and critically located intracranial volume, to arrest or alter tissue growth.

The Gamma Knife, which contains no blade and makes no incision, is exclusively designed for the treatment of malignant and benign brain tumors, vascular malformations and trigeminal neuralgia. As a non-invasive treatment for individuals with well-defined patient profiles, Gamma Knife surgery offers a low-risk, safe and cost-effective alternative.

The Gamma Knife Perfexion combines data from three-dimensional computer imaging studies with a stereotactic head frame to precisely focus radiation. It can destroy, arrest or reduce tumors, cause lesions to deteriorate, close arteriovenous malformations, and alter the conducting pain fibers in cases of trigeminal neuralgia.

At the time of treatment, the patient is fitted with a stereotactic head frame, which serves as a measuring guide and helps keep the head in a fixed position to assure maximum treatment accuracy. The frame’s external axis is used to determine coordinates for targeting the abnormality.

After the frame is attached, the patient receives an MRI, CT, or angiographic scan. Data from the imaging study is transferred into the state-of-the-art treatment planning computer, which enables the treatment team (a neurosurgeon, radiation oncologist, radiation physicist and technicians) to tailor radiation dose distribution to conform specifically to the lesion volume. Completing the treatment plan takes one to two hours, depending on the complexity and location of the disease.

When the treatment plan is completed, the patient is placed on the Gamma Knife couch and precisely positioned. Next, the patient is introduced headfirst into the Gamma Knife, and the procedure begins. The patient is treated with 192 sources of Cobalt 60 housed in the Gamma Knife. The 192 single doses of gamma rays converge at the target area and deliver a dose that is high enough to destroy the diseased tissue without damaging surrounding healthy tissue. This precisely focused radiation targets the lesion, sparing the surrounding healthy tissue.

USC Gamma Knife Team

Our Gamma Knife team at Keck Hospital of USC and the Keck School of Medicine of USC includes neurosurgeons, radiation oncologists, medical physicists, radiation therapists and nurses. Our multidisciplinary team evaluates each patient to determine whether Gamma Knife treatment is the best option. The patient’s medical history is reviewed, along with imaging studies and information provided by the patient’s physician. If Gamma Knife treatment is not considered appropriate, the team will suggest an alternate treatment option.

Gamma Knife treatment offers the following advantages:

• Non-invasive procedure.
• Delivered in a single treatment session.
• Precise mechanical accuracy of .3mm.
• Decreased risk: avoids risks and complications of traditional surgery.
• Minimal hospital stay: usually performed in an outpatient treatment session; patient can resume normal activities within days of procedure.
• Cost-effective: Reduced costs due to post-surgical complications; no expenses for disability and convalescence.
• Reimbursement by most insurance payors.

The Gamma Knife Perfexion System:

• Has new radiation shielding levels that are up to 100 times better than alternative technologies on the market.
• Provides unlimited reach to areas in the brain, and with future fixation devices, can reach into the cervical spine area.
• Being fully automated makes the treatment process more user friendly and efficient for both the treating physicians and patients.
• Includes added features to increase patient comfort while still providing the most accurate stereotactic radiosurgical procedures for the brain.

In 3D conformal radiotherapy, the radiation oncologist shapes and precisely delivers high-energy x-ray beams to the disease site while optimally protecting normal tissues. 3D conformal radiotherapy uses high-speed computers to extract the CT/MRI data, perform three-dimensional isodose calculations, and overlay the data for the radiation oncologist’s and medical physicist’s analysis. This technique allows more accurate and conformal treatment planning so that there is adequate coverage of the tumor with minimal toxicity to the adjacent healthy tissues.

Brachytherapy is the practice of placing radioactive material inside the body for the purpose of killing cancer cells. In low-dose rate brachytherapy, the radioactive material remains in the patient’s body and delivers radiation to the tumor over several days.

High-dose rate brachytherapy delivers a stronger dose of radiation, during one or more individual treatment sessions. The source of radiation is removed from the patient after each session.

Intracavitary brachytherapy

Intracavitary brachytherapy is commonly used to treat patients with cervical and uterine cancers by placing a radioactive source (such as cesium-137 or iridium-192) in a surgical or body cavity, near the area that requires treatment. This option delivers high doses of radiation to the tumor while having minimal impact on the surrounding healthy tissue.

Interstitial brachytherapy

Interstitial brachytherapy is the surgical implantation of radioactive needles or seeds directly into a tumor. It is widely used to treat cancers of the breast and prostate. The radioactive source may remain in the body permanently, even after all of the radiation has been given off.

While less than one-third of all radiation therapy facilities in the United States perform clinical brachytherapy, radiation oncologists at USC have been leaders in developing innovative clinical brachytherapy techniques since the 1970’s. In 2012, through the joint efforts of the USC Norris Comprehensive Cancer Center, Keck Hospital of USC, Los Angeles General Medical Center and Doheny Eye Hospital, special brachytherapy programs are being utilized for managing the most difficult, persistent and recurrent cancers.

Prior to the medical milestone of episcleral eye plaque therapy, the only form of treatment for ophthalmic tumors such as choroidal melanoma was enucleation (the removal of the eye). Episcleral eye plaque therapy is intended as an eye-conserving procedure in which a small metallic “plaque” containing sealed radioactive sources is temporarily placed on the eye adjacent to the tumor.

Eye Plaque Procedure Basics

First, the patient’s opthalmic tumor is measured using ultrasound. This is followed by a CT scan, which will indicate the exact size and shape of the patient’s eye. Photographic fundus imaging is also incorporated to create a highly accurate 3-D computer model showing the precise location of the tumor. This information allows the treatment team of radiation oncologists, ophthalmologists, and physicists to determine the proper dose rate, dose prescription, and the selection of the appropriate plaque and seeds, all of which will facilitate the delivery of a highly conformal dose of radiation to the tumor.

While the patent is under general anesthesia, a device called a “plaque” is attached to the eye. The plaque is about the size of an adult’s thumbnail and contains grooves which hold the radioactive seeds. Each seed is approximately a quarter of an inch long and is about the same diameter as the lead in a number 2 pencil.

The seed-loaded plaque is sewn to the eyeball under the top layer of the conjunctiva (the loose connective tissue that covers the white of the eye.) When the plaque is in place it is not visible from the outside, does not interfere with the patient’s vision, and seldom causes any discomfort.

The plaque is removed about a week after the initial surgery, and the size of the tumor is measured and monitored periodically over time, during subsequent patient visits.