Gamma Knife technology
Overview
Gamma Knife South Africa, based at Netcare’s Milpark Hospital, is home to the Leksell Gamma Knife® Icon™. It gives clinicians the option to perform single or fractionated, frame-based or frameless treatments, allowing for more individualised delivery, without sacrificing precision and accuracy.
Gamma Knife uses highly focused beams of radiation to target tumours and lesions in the brain with high accuracy, while sparing the surrounding normal tissue.
Stereotactic radiosurgery capabilities
Leksell Gamma Knife is widely accepted as the most accurate stereotactic platform for the management of a wide range of conditions of the brain. The advantage of this technology platform is that it uses a large number of beams of radiation (192) that converge on the target in the brain with pinpoint accuracy. This means that the healthy tissue it passes through is spared the damaging effects of the radiation.
Steep dose fall-off
A key safety consideration is that of the available stereotactic radiosurgery platforms, Gamma Knife radiosurgery has the steepest dose fall-off. This results in sparing of normal tissues in close proximity of the treated target in addition to the overall sparing of the brain.
Safety profile - accuracy and precision
The accuracy of the Leksell Gamma Knife® Icon™ gives it the best safety profile. This is particularly important when the treatment site is close to vital or critical brain structures. This accuracy is achieved regardless of the method of immobilisation – frame-based or frameless.
New innovations
The Leksell Gamma Knife® Icon™ is the latest in a long line of specialised brain stereotactic equipment from Elekta. It introduces new innovations such as:
- Integrated imaging and software which continuously controls dose delivery
- The treatment of certain patients without a minimally invasive fixation while assuring the consistent highest level of precision
- Head immobilisation of the patient with a mask as well as the traditional frame.
Gamma Knife - key components
Each system consists of key components:
- The radiation unit which produces the treatment beams
- The patient couch which is an electric bed system
- The control console
- The treatment planning computer system.
Conformal and selective radiosurgery
As with most biological systems, the treatment targets can have various shapes and volumes. Therefore, the planning systems need to allow the multidisciplinary radiation team to map out the treatment site as close to its natural shape as is technically possible. The treatment planning system integrated with Leksell Gamma Knife allows for a conformal dose distribution to the target.
Workflows
The Gamma Knife allows for patients to be treated using a rigid head frame or a frameless mask. Before treatment, a magnetic resonance imaging (MRI) image of the patient’s brain is taken, with or without a frame. The MRI is then sent to the treatment planning system where the treatment plan is created.
There are two different approaches or workflows:
- In framed cases, the frame placement, imaging, treatment plan and delivery are all completed on the same day and in a single treatment.
- The mask-based workflow allows for mask fabrication, imaging and treatment planning to take place before treatment and allows for multi-fraction treatments. A limitation of mask-based treatment is intra-fractional motion, which may interrupt and prolong the treatment.
Computerised treatment planning system
- Helps ensure the target in the brain is covered by a clinically significant dose (higher than the radiation dose in conventional radiotherapy)
- Spares healthy surrounding brain tissue
- Allows the creation of detailed and precise dose distributions.
Optimised workflows
Several optimised workflows are available that serve as a platform for the treatment team to adapt to the requirements of each patient. This improves efficiency without compromising accuracy. The online adaptive dose control setting allows the dose for each patient to be monitored in real-time during treatment.
Patient couch
Movement of the patient couch in and out of the radiation unit and opening of the shielding door is performed with high precision. The patient’s head is moved into the focus point using very precise robotics.
Robotic technology
Sophisticated robotic technology moves a patient in submillimetre increments during treatment to focus the radiation dose on all parts of the target in the brain. The source of radiation and target are in a fixed relationship during radiation delivery. Computer-guided dosimetry is specified to match the lesion.
Small lesions to complex and multiple metastases
The Leksell Gamma Knife® Icon™ can target the smallest, most complex lesions or multiple metastatic sites with:
- The highest accuracy and
- The lowest dose to normal tissue.
Dose margin reduced
Compared to other radiosurgery systems, the Leksell Gamma Knife® has the best ability to spare healthy brain tissue. Other systems deliver high doses of radiation to a selected margin of healthy tissue surrounding the lesion to ensure complete destruction of the lesion. The healthy tissue is therefore sacrificed to ensure optimal treatment. Accuracy of the Leksell Gamma Knife® Icon™ means that the margin of healthy tissue close to the treatment site is preserved and less healthy tissue is lost.
Cobolt-60 sources
During Gamma Knife radiosurgery, up to 192 radiation beams from Cobalt-60 sources accurately converge on the target treatment site. The point where the beams converge is called the isocenter. The radiation dose is concentrated in this isocenter to spare surrounding healthy brain tissue.
Optimising treatment to the need of each patient
No patient or radiosurgery treatment is exactly the same. Leksell Gamma Knife® Icon™ technology allows the treatment team to adapt and optimise treatment to the needs of each patient.
Ongoing technology developments
As technology improves and knowledge expands, ongoing improvements and refinements are being made. Other advantages of the latest Leksell Gamma Knife® Icon™ over earlier models include:
- It uses either a head frame or a frameless face mask to secure the head during treatment.
Changing clinical treatment paradigms
In the past few decades, stereotactic radiosurgery techniques have changed the clinical treatment paradigms in managing neuro-oncology patients.
Stereotactic radiosurgery:
- Offers improved treatment options for patients and
- Introduces a major shift away from the use of whole-brain radiation in many patients.
