The fact is, the Gamma Knife is not really a knife at all, but a non-invasive tool that replaces the scalpel with a focused array of 192 intersecting beams of high-intensity gamma radiation. Hoag Memorial Hospital is one of the first in the nation to have the absolute state-of-the art fully upgraded Gamma Knife Perfexion™. Treatment times are shorter, accuracy is even better than its most accurate predecessor and outcomes will be even better. The Perfexion™ delivers 100 times less radiation to normal tissue than the latest CyberKnife™. Worldwide, there is 10 times more experience with the Gamma Knife than with any other “knock-off.”



The new Gamma Knife Perfexion™



The Gamma Knife concept originated in Stockholm in 1951, when Dr. Lars Leksell, a prominent neurosurgeon, coined the term “Radiosurgery.” Dr. Leksell was a pioneer in “Stereotaxy,” a procedure which allows the neurosurgeon to locate and reach any point of the brain to within a single millimeter of accuracy, using trigonometry to navigate the brain’s 3-dimensional space.

Consequently, in lieu of performing open surgery on the brain, the neurosurgeon has the ability to precisely focus gamma radiation on a target tumor or vascular malformation. Focused radiation may also be used to treat “functional” disorders such as the tremors resulting from Parkinson’s disease, and the pain syndrome of trigeminal neuralgia.


The photon beams of the Gamma Knife intersect precisely on the target.



Contrary to conventional radiation therapy, which must be delivered in small fractions over time (often over as many as six weeks), and in which normal brain tissue is exposed to approximately the same amount of radiation as the tumor target, Gamma Knife radiosurgery employs a greater number of lower level radiation sources (201) arranged in a collimator Helmet. The neurosurgeon intersects these beams on the target.




Each beam is very weak, passing through an area of the brain different from all of the other beams. Thus each beam is safe to normal brain tissue but where they focus is 200 times as powerful as each individual beam.



In order to focus the beams precisely and accurately, the patient must be fitted with a painless “stereotactic frame” prior to the MRI and Gamma Knife procedure.


The painless stereotactic frame allows accurate focus. Upon removal, the pinsites are essentially invisible a week later.

The combined effect at the intersection of the beams is 201 times as powerful as each individual beam, and can obliterate tumors and vascular malformations in a single treatment.



Gamma Knife radiosurgery is not experimental. The first Gamma Knife treatment was recorded in Sweden in 1968, and since then nearly 20,000 patients per year are being successfully treated worldwide.

Gamma Knife radiosurgery has been performed on American soil since 1987 and by Dr. Duma in Southern California and the East Coast since 1990. He has performed approximately 220 Gamma Knife procedures per year since that time. The medical literature is replete with hundreds of articles relating to Gamma Knife radiosurgery that is considered the “gold standard” of radiosurgical technique.



The Gamma Knife treatment is usually performed in a single morning.

There is no pain, no noise (other than the MRI) and patients are invited to bring music of their choice for listening during the treatment. They may return to work the next day, or fly home on an airplane. There are no incisions, or sutures. The patient will usually be discharged that afternoon or if necessary, discharged on the following day. Almost all insurance company HMOs, PPOs, Medicare, Medical, etc. cover the cost of the procedure.

The typical day is as follows:

6:30 AM
Pre-op preparation

7:30 – 7:45
Stereotactic frame application (under “twilight” sedation)

8:00 – 9:00
MRI for targeting

9:00 – 10:00
Computer Planning

Gamma Knife treatment (depending on pathology, from 10 to 90 minutes)

Stereotactic frame is removed.

Patient returns to the hospital room in time for lunch, and goes home that afternoon.


Leading Edge Gamma Knife Radiosurgery

The leading edge technique is an innovative process developed to treat one of the most common types of glioma, glioblastoma multiforme. The leading edge treatment combines the functionality of the Gamma Knife radiosurgery technology with the advances in diagnostic radiology technology, which include Multivoxel MR-Spectroscopy scans. This unique combination targets the radiation beyond the local tumor volume to include the potential malignant tumor path. Prior to this technological spectroscopy breakthrough, it was impossible to detect where the tumor would or might spread.



Glioblastoma multiforme (GBM) is among the most common and devastating brain tumors affecting adults. The most successful treatment regimens for GBMs include surgical resection, radiation therapy and chemotherapy, followed by stereotactic radiosurgical boost (Gamma Knife radiosurgery) and immunotherapy. Despite aggressive therapies, the malignant nature of GBMs often results in tumor recurrence. Ninety percent of GBMs recur at the site of the original tumor. In addition to local recurrence, malignant gliomas frequently spread in predictable patterns along the white matter pathways in the brain. It is via this mechanism that long-fought battles against GBMs are often lost.


Predictable Patterns of Spread in Malignant Gliomas

Traditional radiosurgical techniques have focused solely on local tumor margins, as determined by gadolinium enhancement on MRI. However, recent data suggests that by targeting the “leading edge” of these tumors, their spread along white matter pathways can be more effectively halted. FLAIR sequences and Multivoxel MR-Spect scans can be utilized to define positive areas outside of the gadolinium T1-weighted enhancing zones. Targeting these zones with gamma knife is proving to be a successful method of blocking the path of malignant gliomas.


Targeting of MR-Spect positive zones outside of Gadolinium T1-weighted enhancing zones



MR-Spectrography of normal and neoplastic brain regions


Multivoxel MRS can distinguish normal areas from tumor


Initial results are optimistic, with a mean follow-up from diagnosis of 14.4 months (range = 2 to 58 months), and mean follow-up from the time of radiosurgery of 8.4 months (range = 1 to 24 months). Median projected Kaplan-Meier survival was 22 months for patients receiving leading edge therapy as their primary treatment, 15.5 months for patients with recurrent disease, and 23 months from the time of diagnosis for all patients.

Longer follow-up is necessary to determine the overall efficacy of “leading edge” radiosurgery. But these data suggest that targeting the white matter pathways along which GBMs are known to spread results in a survival advantage for patients with these aggressive, malignant gliomas.

In our series, 18 consecutive patients with amenable tumors (i.e. lobar, polar locations) were treated with our “leading edge” Gamma Knife procedure. Ages ranged from 21 to 72 years (median = 49). Eight of the 18 patients were being treated for recurrent disease. Most had received some form of prior treatment, including LAK cell therapy (6), chemotherapy (8) and prior GK treatments (3). However, no statistical difference was observed among these groups. Complications were comparable to those seen with traditionally radiosurgical targeting, and included a 44% mild edema rate requiring short-term steroid therapy, and 5% admission rate for mannitol and IV steroids for severe edema and radiation necrosis


Learn about the "Leading Edge©" Gamma Knife technigue. Read article.



Shown below there are the Indications and Results of Dr. Christopher Duma’s Personal Gamma Knife Radiosurgery Series in Los Angeles, Orange County, Newport Beach and City of Irvine.

All types of brain tumors may be treated using this technique because it does not rely on variable tissue sensitivity to radiation. All cells within a radiosurgical treatment volume receive a toxic dose of radiation creating cell kill. The DNA is destroyed and so are critical proteins responsible for cell division. However, because the amount of radiation delivered has to be decreased as target size increases, neurosurgeons are limited to treating tumors less than 3 or 4 cm. in average diameter.

Listed below are Dr. Duma’s personal results using Gamma Knife radiosurgery for various pathologies:


  • 94% tumor control rate
  • 10% edema risk 2% will require surgical removal of tumor for treatment of edema
  • 2% risk of permanent injury

Torcular meningioma, prior to, and 14 months after Gamma Knife radiosurgery only


Acoustic Neuromas:

  • 98% tumor control rate
  • 60% hearing preservation rate.

Acoustic neuroma before, 3 months, and 9 months after Gamma Knife Radiosurgery only


Brain Metastases: (regardless of tissue type)

  • 90% tumor control rate
  • 6% edema risk
  • 2% permanent deficit risk
  • 1/50 will require surgical removal despite GK treatment.
  • More than one tumor may be treated in one session.


Renal cell carcinoma brain metastasis before and 1 year after Gamma Knife radiosurgery only


Glioblastoma Multiforme: (Astrocytoma Grade 4) and Anaplastic Astrocytomas (Grade 3)

  • 93% response rate with median tumor progression free interval of 12 months
  • Improvement in overall survival. Synergistic when combined with immunotherapy. Some patients are now more than 8 years from their initial diagnosis treated with this powerful regimen. Patients and their family members of survivors of this disease using this regimen may be contacted.

Glioblastoma Multiforme (Grade 4 astrocytoma) Before and 3 1/2 years post immunotherapy. Biopsies of the residual mass on the right showed only dead, necrotic tissue.


Primary Low Grade Gliomas of the Brain:

  • 95% response rate.
  • 10-year follow-ups in most patients treated show no evidence of residual tumor.

Craniopharyngiomas, Pituitary Adenomas, Ependymomas, Medulloblastomas, Pineal tumors and other types:

  • From 80-98% tumor control rates.


Arteriovenous Malformations: (AVMs):

  • 80% complete obliteration by 2 years
  • 6% complication rate
  • 3% permanent complication rate, (stroke, or sustained neurologic deficit).

Arteriovenous malformation (AVM) before, and 2 years after Gamma Knife radiosurgery


Tremor of Parkinson’s Disease (Gamma Knife thalamotomy)

  • 80% Good to excellent relief of tremor occurring within 3 months of treatment

Trigeminal Neuralgia: (Tic Doulereux)

  • 85% Good to excellent relief of pain
  • 55% are pain-free off all medication. The rest are pain free with lowered dosages of medications.
  • The effect of treatment takes an average of 4 weeks to occur post Gamma Knife.
  • 8% risk of sensory loss on the face.
  • Near zero risk of anesthesia dolorosa.

The patient’s trigeminal nerve accurately targeted for a Gamma Knife radiosurgery treatment.



Christopher Duma, MD, FACS
3900 West Coast Highway, Suite 300
Newport Beach, CA 92663
Phone: 949-989-5894
Fax: 949.642.4833

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