What Is a Gamma Knife?

Gamma Knife is the main treatment method of Stereotactic Radiosurgery. According to the principle of stereo geometric orientation, the normal or diseased tissue in the skull is selectively identified as the target point. Gamma rays are focused and irradiated at once in large doses to cause focal necrosis or functional changes to achieve the purpose of treating diseases. ^[1]

Gamma Knife

Gamma Knife is the main treatment method of Stereotactic Radiosurgery. According to the principle of stereo geometric orientation, the normal or diseased tissue in the skull is selectively identified as the target point. Gamma rays are focused and irradiated at once in large doses to cause focal necrosis or functional changes to achieve the purpose of treating diseases. ^[1]

In 1951, Professor Leksell of Sweden first proposed the idea of radiosurgery and designed the first radiotherapy equipment. Connect the guide on the C-arm of the first-generation brain stereotactic instrument with a medium-voltage X-ray tube to rotate the emitted X-rays along the trajectory of the C-arm, so that the rays converge at the center point. The first patient treated was trigeminal neuralgia, and the target was the trigeminal neuralgia. The patient achieved good long-term pain relief and no longer needed surgery. Based on this, Leksell cooperated with physicist Larsson, using proton beams generated by cyclotrons and early linear accelerators as tools for radiosurgery, and conducted a series of animal experiments and clinical studies to find different treatment methods for radiosurgery. And the application of different radiation created a good start. ^[1]

During the treatment, a three-dimensional positioning system is used to locate the lesion. The stereotactic system is a special coordinate system. After the stereotactic system is relatively fixed, the patient's tomography by CT and MRI shows the relative position of the lesion and the reference points of the coordinate system. After positioning, the treatment planning system automatically processes the images scanned by CT and MRI, reconstructs the three-dimensional morphology of the skull, lesions, and surrounding tissues, and designs the treatment plan based on the prescription dose given by the doctor to calculate the number of targets needed for treatment, Target coordinates, irradiation time, collimator number used for each target, etc. After receiving the relevant parameters of the treatment planning system, the electrical control system sends each target point to the focus in turn, and opens the corresponding collimator for quantitative irradiation. ^[1]

Gamma Knife has obvious advantages in treating tumors. Specifically, it has the following characteristics ^[1] :

(1) The treatment is simple: it takes about several minutes to several tens of minutes.

(2) Convenient and safe: The patient does not have hair loss, no serious adverse reactions, no blood transfusion or medication after surgery, no restrictions on diet and activities, and generally no hospitalization.

(3) Accuracy: The entire treatment process is controlled by computer, which is reliable, accurate, accurate and safe, without damage to normal tissues.

(4) No obvious contraindications to surgery: hypertension, physical condition and heart disease, the treatment process is not affected by coexisting diseases such as age, diabetes and pneumonia, no contraindications to surgery, especially suitable for those who cannot tolerate surgery or anesthesia, Multiple metastases can be treated at once.

(5) No need for anesthesia: no special preparation, medication, no trauma, no bleeding are needed before the operation, and the operation is performed under sober and painless conditions.

The premise of ensuring that the Gamma Knife can accurately and effectively treat tumors is the accuracy of the Gamma Knife focus, the focus dose rate and absolute dose of the focus, and the relative dose of the reference point. These parameters are the basic prerequisites for ensuring the treatment of patients. Various mechanical, nuclear physics, dose, planning system and other parameters were repeatedly measured and verified, and the treatment parameters were determined and verified in combination with actual patients before they were applied to the clinic. ^[1]