Debus J, Pirzkall A, Schlegel W, Wannenmacher M
Deutsches Krebsforschungszentrum Heidelberg (DKFZ), Abteilung für Medizinphysik, Rupprecht-Karls-Universität, Heidelberg.
Strahlenther Onkol. 1999 Feb;175(2):47-56. doi: 10.1007/BF02753842.
Stereotaxy is a method to determine a point in the patient's body by an external coordinate system which is attached to the patient. Radiosurgery uses this method for precise delivery of a high single radiation dose to the patient. The aim is to destroy the tissue in the target and to spare surrounding unaffected normal tissue by a steep dose gradient.
Three techniques of percutaneous radiosurgery are available: radiosurgery with ion beams with a cyclotron, spherical arrangement of cobalt-60 sources, the so-called gamma knife, and an adapted linear accelerator. The availability and the good clinical experience lead to a wide spread use of linear accelerator for radiosurgery in recent years. A subsequent development is fractionated stereotactic radiotherapy which combines the precision of radiosurgery with the radiobiological advantage of fractionation.
Only a few indications for radiosurgery are proven by statistically valid studies. One of these is the treatment of small arteriovenous malformation, where obliteration rates of 80% to 100% are reported with only minor toxicity. However, the obliteration rate is reduced significantly in large arteriovenous malformations. A local control rate of 90% is obtained after radiosurgery of brain metastases which is comparable to the results of microsurgical resection followed by adjuvant whole brain radiotherapy. An ongoing EORTC study evaluates the role of adjuvant whole brain radiotherapy after radiosurgery. The survival of the patients with brain metastases is limited by the existence of progressive extracerebral disease. The role of radiosurgery in the treatment of benign tumors is currently evaluated in clinical studies which include: vestibular schwannomas, meningiomas, chordomas and chondrosarcomas and pituitary adenomas. Most of the published studies include only small tumors because radiosurgery is limited by the risk of radionecrosis of adjacent normal tissue, which shows a steep dose volume response relationship. Recent developments of stereotactic radiotherapy include the use of mini-multileaf-collimators and clinical studies on stereotactic radiotherapy of extracranial targets.
Stereotactic irradiation is a well established treatment technique for intracranial tumors and arteriovenous malformations. Methods are available that allow optimization of dose distributions to irregularly shaped tumors for single dose as well as fractionated stereotactic irradiations by linear accelerator. Therefore the therapeutic potential of this technique has increased and enables also the extracerebral application in controlled clinical studies.
立体定向是一种通过附着于患者身体的外部坐标系来确定患者体内某一点的方法。放射外科利用该方法向患者精确递送高单次辐射剂量。目的是破坏靶区内的组织，并通过陡峭的剂量梯度使周围未受影响的正常组织免受辐射。
经皮放射外科有三种技术：使用回旋加速器产生离子束的放射外科、钴 - 60源的球形排列（即所谓的伽马刀）以及适配的直线加速器。由于其可用性和良好的临床经验，近年来直线加速器在放射外科中的应用广泛。后续发展是分割立体定向放射治疗，它将放射外科的精确性与分割治疗的放射生物学优势相结合。
仅有少数放射外科适应证经统计学有效研究证实。其中之一是治疗小型动静脉畸形，据报道闭塞率为80%至100%，且毒性轻微。然而，大型动静脉畸形的闭塞率显著降低。脑转移瘤放射外科治疗后局部控制率达90%，这与显微手术切除后辅助全脑放疗的结果相当。一项正在进行的欧洲癌症研究与治疗组织（EORTC）研究评估了放射外科后辅助全脑放疗的作用。脑转移瘤患者的生存受进行性脑外疾病的限制。放射外科在良性肿瘤治疗中的作用目前正在临床研究中进行评估，这些研究包括：前庭神经鞘瘤、脑膜瘤、脊索瘤、软骨肉瘤和垂体腺瘤。大多数已发表的研究仅纳入了小型肿瘤，因为放射外科受相邻正常组织放射性坏死风险的限制，该风险呈现陡峭的剂量体积反应关系。立体定向放射治疗的最新进展包括使用微型多叶准直器以及对颅外靶区进行立体定向放射治疗的临床研究。
立体定向照射是一种成熟的颅内肿瘤和动静脉畸形治疗技术。现有方法可通过直线加速器对不规则形状肿瘤的单次剂量以及分割立体定向照射的剂量分布进行优化。因此，该技术的治疗潜力有所增加，并且在可控的临床研究中也能够应用于脑外疾病。
