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Extracranial absorbed doses with Gamma Knife radiosurgery
H W Berk1, J M Larner, C Spaulding
1Lars Leksell Center for Radiosurgery, University of Virginia Health Sciences Center, Charlottesville.
Stereotactic and Functional Neurosurgery
|January 1, 1993
Summary
Stereotactic radiosurgery delivers radiation to treat brain lesions. This study measured extracranial absorbed doses in patients, finding low but measurable radiation levels in organs like the eye and thyroid.
Area of Science:
- Neurosurgery
- Radiation Oncology
- Medical Physics
Background:
- Stereotactic radiosurgery is increasingly used for various intracranial lesions, including arteriovenous malformations (AVMs), acoustic neuromas, meningiomas, pituitary adenomas, and metastases.
- While target volume dosimetry is well-studied, extracranial absorbed doses from radiosurgery are less understood.
Purpose of the Study:
- To quantify absorbed radiation doses in specific extracranial organs (eye, thyroid, sternum, gonads) of patients undergoing Gamma Knife radiosurgery.
- To compare these doses between adult and pediatric patient groups.
Main Methods:
- Thermoluminescent dosimetry (TLDs) was used to measure absorbed doses in 111 patients (100 adults, 11 children).
- Patients received Gamma Knife radiosurgery for various intracranial conditions, with target absorbed doses averaging 35 Gy in adults.
Main Results:
- Average absorbed doses in adults were: eye (9 cGy), thyroid (15 cGy), sternum (20 cGy), and gonads (3 cGy).
- Pediatric patients showed similar doses, except for a significantly higher gonadal dose.
- Use of multiple isocenters correlated with increased extracranial absorbed doses.
Conclusions:
- Extracranial absorbed doses from Gamma Knife radiosurgery are generally low but measurable.
- Particular attention should be paid to gonadal doses in pediatric patients.
- Optimizing isocenter selection may help minimize radiation exposure to non-target tissues.