Stereotactic radiosurgery (SRS)

The irradiation of tumors in the brain is challenging due to the proximity of radiation-sensitive critical structures and the tumors to be treated. In addition, irradiation above a certain level can cause irreversible damage to nerve tissue. The irradiation of benign and malignant brain tumors requires precise techniques to preserve critical structures while simultaneously administering a high radiation dose for maximum effectiveness. Therefore, stereotaxy, as a subspecialty of neurosurgery, has developed various irradiation techniques, e. g., intracerebral application of interstitial brachytherapy (SBT; stereotactic brachytherapy) and stereotactic radiosurgery (SRS). Due to the development of computer-controlled radiation techniques (e. g., Cyberknife) over the last 20 years, SRS has gained increasing importance 1).

By definition, the term “radiosurgery” refers to the delivery of a therapeutic radiation dose in a single fraction, not simply the use of stereotaxy. Multiple-fraction delivery is better termed “stereotactic radiotherapy.”

Is a form of radiation therapy that focuses high-power energy on a small area of the body. Despite its name, radiosurgery is a treatment, not a surgical procedure.

Four available stereotactic radiosurgery (SRS) modalities:

Leksell Gamma Knife Perfexion.

Novalis-Tx Dynamic-Conformal-Arc (DCA). Micro-multileaf collimator system of the Novalis linear accelerator (LINAC) (MML).

Dynamic-Multileaf-Collimation-Intensity-Modulated-radiotherapy (DMLC-IMRT)


see Gamma Knife stereotactic radiosurgery.

Stereotactic radiosurgery with an adapted linear accelerator (linac-SRS).

Gamma-Knife-Perfexion will comply with all SRS constraints (high conformity while minimizing low-dose spread). Multiple focal entries (Gamma-Knife-Perfexion and Cyberknife) will achieve better conformity than High-Definition-MLC of Novalis-Tx at the cost of treatment time. Non-isocentric beams (Cyberknife) or IMRT-beams (Novalis-Tx-DMLC-IMRT) will spread more low-dose than multiple isocenters (Gamma-Knife-Perfexion) or dynamic arcs (Novalis-Tx-DCA). Inverse planning and modulated fluences (Novalis-Tx-DMLC-IMRT and CyberKnife) will deliver the most homogeneous treatment. Furthermore, Linac-based systems (Novalis and Cyberknife) can perform image verification at the time of treatment delivery 2)

The multiple focal entry systems (Gamma Knife and Cyberknife) achieve higher conformity than the Novalis system. The Gamma Knife delivers the steepest dose gradient of all examined systems. However, the Gamma Knife is known to require long beam-on times, and despite worse dose gradients, LINAC-based systems (Novalis and Cyberknife) offer image verification at the time of treatment delivery 3).

see Intracranial stereotactic radiosurgery.

Rueß D, Kocher M, Treuer H, Ruge MI. [Computer-controlled high-precision radiation]. HNO. 2016 Jul 8. [Epub ahead of print] German. PubMed PMID: 27393294.
Gevaert T, Levivier M, Lacornerie T, Verellen D, Engels B, Reynaert N, Tournel K, Duchateau M, Reynders T, Depuydt T, Collen C, Lartigau E, De Ridder M. Dosimetric comparison of different treatment modalities for stereotactic radiosurgery of arteriovenous malformations and acoustic neuromas. Radiother Oncol. 2013 Feb;106(2):192-7. doi: 10.1016/j.radonc.2012.07.002. Epub 2012 Aug 10. PubMed PMID: 22884842.
Kaul D, Badakhshi H, Gevaert T, Pasemann D, Budach V, Tulaesca C, Gruen A, Prasad V, Levivier M, Kufeld M. Dosimetric comparison of different treatment modalities for stereotactic radiosurgery of meningioma. Acta Neurochir (Wien). 2015 Apr;157(4):559-64. doi: 10.1007/s00701-014-2272-9. Epub 2014 Nov 21. PubMed PMID: 25413163.
  • stereotactic_radiosurgery.txt
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