Modern stereotactic radiotherapy

Author: Chief Editor: Wang Yingxuan et al
Publisher:
Publish Date: 1999-05-01
Features: This book is a monograph on stereotactic radiosurgery in China, divided into 8 parts and 35 chapters. It systematically introduces the development and current status of stereotactic radiosurgery, the basic principles of radiobiology, and the types, structural characteristics, and operational methods of treatment equipment systems such as gamma knives and X-knives. It also covers the development overview, treatment characteristics, physical dosimetry, methodologies, and clinical applications of stereotactic radiosurgery, three-dimensional conformal radiotherapy, and stereotactic brachytherapy. Additionally, it discusses indications, contraindications, side effects, complications, efficacy, and evaluation, as well as the radiation damage to normal organs and tissues and its prevention, and the impact on the growth and development of children and adolescents. The primary readership includes physicians, staff, researchers, and graduate students in departments such as neurosurgery, oncology, and radiotherapy.
Excerpt: Chapter Stereotactic Radiosurgery: Development and Current Status
Stereotactic radiosurgery (SRS) refers to the single-fraction irradiation of high-energy radiation focused on a localized target area within the brain, causing a radiological response while sparing surrounding tissues due to the rapid dose reduction, thereby creating a sharp, knife-like interface at the edge of the target, achieving a surgical-like effect. This method differs from both surgical intervention and conventional radiotherapy as well as various brachytherapies. This technique integrates the theories and technologies of modern neurosurgery, tumor radiotherapy, radiophysics, and medical engineering, making it a comprehensive interdisciplinary field in clinical medical engineering. After 30 to 40 years of development, it has become a mature and significant branch of modern neurosurgery, capable of partially replacing modern microscopic neurosurgery. This minimally invasive treatment technique, after years of clinical medical practice and long-term patient follow-up, has been proven to be safe and reliable, and its efficacy is increasingly valued by neurosurgeons. Medical statistics indicate that currently, over 90 gamma knives using 60Co as the radiation source and over 300 linear accelerator-based stereotactic radiosurgery systems (commonly referred to as X-knives) have been installed worldwide, treating a large number of cases. In China, over 100 stereotactic radiosurgery treatment centers for neurosurgery have been established, and it is estimated that this trend will continue to grow.
Section Brief History
With the development of medicine and science, the methods and scope of clinical surgical treatment for diseases have undergone continuous changes, with neurosurgery showing particularly significant advancements in recent years. Initially, neurosurgeons primarily treated diseases by surgically destroying or removing certain intracranial lesions, but this often resulted in brain tissue damage and functional impairment. Through long-term experience and observation, people gradually gained a deeper understanding of the structures, nuclei, fiber bundles, and blood vessels of the brain and central nervous system. To improve and enhance the effectiveness of neurosurgery while preserving important functional neural tissues, surgeons began to focus on protecting these tissues during treatment. As a result, minimally invasive neurosurgical techniques such as microscopic neurosurgery and stereotaxy emerged. Stereotactic neurosurgery refers to surgery performed using a stereotactic instrument. Its principles were proposed by Clarke, Horslety, and others at the beginning of the 20th century and were subjected to early animal experiments. However, due to insufficient accuracy in positioning, it was not widely used in clinical practice. After 1947, Siegel and Wycis in the United States introduced new stereotactic instruments for the brain and used ventriculography to determine intracranial targets, successfully applying stereotactic surgery to treat patients for the first time. After nearly half a century of exploration, many neurosurgeons developed stereotactic instruments with unique features, among the most representative being those designed by Riechert, ToddWell, Gillingham, Leksell, BrownRobert-Wells, Talairach, and Sugita. In China, since the early 1960s, research on stereotactic neurosurgery has been conducted in cities such as Beijing, Shanghai, Anhui, and Xi'an, and stereotactic instruments designed by local teams have been introduced in Shanghai, Anhui, Xi'an, Nanjing, and Shandong. Most of these instruments operate on the same principle: designing a fixed frame to be mounted on the patient's skull, establishing a consistent spatial coordinate relationship between the frame and the patient's head structure. Using imaging techniques (X-rays, CT, MRI), the coordinates of the target within the frame are determined, and surgical instruments are then guided along the determined direction to reach the target. The stereotactic instrument consists of two parts: the orientation system and the guidance system. The orientation system fixes the frame on the patient's head and calculates the three-dimensional (X, Y, Z-axis) coordinates of the intracranial target through imaging. The guidance system directs the surgical instrument to the predetermined target for procedures such as needle insertion, electrophysiological examinations, and final destruction. This technique minimizes trauma and preserves more neural functions, improving the treatment outcomes for certain neurosurgical diseases and expanding the scope of practice. In recent years, with the advancement of research on neurotransmitters, endocrinology, and various receptors, people have gained new insights into functional disorders caused by dysfunction in the nervous system, leading to the emergence of functional neurosurgery. This approach uses surgical methods to destroy or reconstruct certain neural nuclei, adjusting the function of certain structures to alleviate symptoms and further advancing neurosurgery into the field of neurobiology. Over the decades, the development of this surgery has primarily revolved around two core issues: target localization and destruction methods. The advancement of these two aspects has driven the evolution of stereotactic radiosurgery and improved treatment outcomes. In terms of target localization, it initially relied on ventriculography, but with the introduction of diagnostic instruments such as DSA, CT, MRI, and PET, minimally invasive or non-invasive methods have gradually replaced it, enhancing the precision and safety of localization. Computer-based two-dimensional or three-dimensional image display has also been established, making it applicable to both visible and invisible targets, expanding clinical indications and enabling the treatment of various functional and organic diseases. In terms of target destruction methods, techniques such as corpus callosotomy, balloon compression, drug injection, cryotherapy, laser, and radiofrequency coagulation have been used. In 1951, Swedish neurosurgeon Leksell proposed the use of concentrated radiation, and through the efforts of several generations, the theoretical and technical foundations of stereotactic radiosurgery were established, achieving excellent clinical outcomes (Tables 1-1-1 and 1-1-2). The three most prominent methods are the gamma knife, the linear accelerator-based stereotactic system, and charged-particle radiation, which will be described separately below.