march 2006 - stereotactic radiosurgery gordon, k

FACET - European Journal of Cancer CareMarch 2006

slides available at: www.blackwellpublishing.com/journals/ecc

Stereotactic radiosurgery Gordon, K.1

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What is stereotactic radiosurgery?

• Stereotactic radiosurgery is a non-surgical technique used to selectively destroy abnormalities within the brain.

• Using a machine called the Gamma Knife, 201 sources of Cobalt-60 are focused to a small point (isocentre) ranging from 4-18mm in diameter.

• This tiny area provides a very high dose of radiation which is used to irradiate a focal point within the brain with sub-millimetre accuracy.



Stereotactic radiosurgery (continued)S

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History



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Stereotactic radiosurgery (continued)

Clinical applications

• Tumours

• Benign

• Malignant

• Functional disorders

• Vascular disorders



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The procedure

Stereotactic radiosurgery is a four stage procedure:

1. Stereotactic frame fixation

2. Imaging procedures

3. 3D dose planning

4. Gamma Knife treatment.



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Frame fixation

To immobilise the patient, a frame is fixed to the outer layer of the skull under local anaesthetic using four pins.


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Imaging procedure

All patients will undergo some form of radiographic imaging study with the frame in place in order to localise the area to be treated.

This will either be:

• MRI

• CT

• Angiography


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3D dose planning

3D dose planning from the radiographic images.


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Gamma Knife treatment


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Side effects• Headaches (most common side

effect)

• Occasional hair loss

• Other symptoms due to raised intracranial pressure and oedema (nausea, vomiting)

• Effects of radiation damage to normal tissues:

• Cranial nerves

• Optic apparatus

• Brain stem

• Necrosis


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Acoustic neuroma

TV at treatment:

6.8cc

TV at 7 months follow-up: 7.4cc

TV at 1yr follow-up:

3.2ccN.B. cc = cubic centimetres


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Single melanoma metastasis

TV at treatment: 17.0cc TV at 5 month follow-up: 1.0cc

TV at 1year follow-up: 1.0cc

TV at 1yr 3month follow-up: 0.756cc


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Multiple metastases: breast

3D view at treatment10 metastases. Total volume = 13.9 cm3

3D View at 6 month follow-up. Only 3 metastases now visible on triple dose contrast enhanced MRITotal volume = 0.6 cm3


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Summary (1)

• Excellent treatment approach for a number of brain abnormalities

• Non invasive

• Single treatment requiring a short hospital stay


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Summary (2)

• Very few (if any) side effects

• Limitations – due to the nature of the radiation it is more effective when delivered to small areas. Therefore, there is limited use in large tumours and patients are referred for more conventional treatments.


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The future

• More research to realise the potential in areas such as Parkinson's disease and epilepsy.

• Publish results of such trials, raising awareness within the medical community therefore opening the treatment up to more patients.

• Open more centres around the world to make the treatment more available.


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References and further reading

• http://www.gammaknife.co.uk

• http://www.elekta.com

• http://www.irsa.org/radiosurgery.html

• Gordon K, Eddy D. (2006) The efficacy of Stereotactic Radiosurgery in the management of Vestibular Schwannomas - a retrospective analysis. Journal of Radiotherapy in Practice. 5 (1): 1-12.

• Hickey, K. (2004) Role of stereotactic radiosurgery in the management of single or multiple cerebral metastases. Journal of Radiotherapy in Practice. 3 (4): 197-203.

• Hickey, K. (2004) Conventional and contemporary management approaches for the treatment of vestibular schwannomas: Microsurgery versus radiosurgery, a literature review. Journal of Radiotherapy in Practice. 4 (1): 39-45.

march 2006 - stereotactic radiosurgery gordon, k

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high dose of radiation

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tiny area

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