1 A historical account on stereotactic radiosurgery might be given in more than one way. One alternative would be to describe how this new therapeutic conception, arising from and firmly rooted in profound clinical experience, emerged in the minds of the pioneers and, in the same minds, gave rise to seminal driving forces behind technical design processes. Another way of writing radiosurgical history would be just to give a panorama of equipment and machinery, that is, the substantial realization of technical ideas. In this introductory chapter, I will try to use the former of these two narrative approaches. Radiosurgery as a new therapy was introduced into the clinical setting with the development of the Gamma Knife (GK, Elekta AB, Stockholm, Sweden), invented by professor Lars Leksell in Stockholm, Sweden.1 In its present design, it is probably still the most sophisticated radiosurgical tool built so far. The launch in 1967 of this first GK prototype represents the “birth” of intracranial radiosurgery, at least in a more limited sense. Intracranial precision irradiation has been in use since at least the 1940s. Stereotactic, surgical introduction of solid (and liquid) radioactive sources into the pituitary gland and eloquently located brain tumors was more or less routine management at several centers, primarily in Germany and France (for a review, see the reports from a symposium in Paris in 1979).2 The goal of avoiding these invasive alternatives gave rise to the idea that external cross-firing of intracranial targets, by narrow high-energy ionizing beams, could take the place of these “bloody” techniques, in addition to being completely without surgical risks. Moreover, satisfying—or even better—dose and field parameters would be possible using focused external irradiation. Beginning in the 1950s, multiportal techniques using protons were explored at several centers (for a thorough review, see Larsson3). In Sweden, Lars Leksell and Börje Larsson were conducting such studies using the 185 MeV proton beam at the Gustav Werner Institute in Uppsala. Interestingly, an early key paper from this group4 became seminal (“a crucial flash of inspiration”) in the mind of Allan Cormack when thinking out the computed tomography (CT) technique (for which he later won the Nobel prize together with Godfrey Hounsfield). Thus, the radiosurgical cross-firing concept seems to have fertilized Cormack’s thoughts while he was designing the first CT machine. The Gustav Werner Institute became the cradle of neurosurgical radiosurgery. Irradiation with heavy particles was also practiced by Lawrence’s group in Berkeley, California, however, without the use of stereotactic technique in its limited sense. Raymond Kjellberg, a neurosurgeon using the cyclotron at Harvard, started to explore the applicability of the proton beam Bragg peak in pituitary irradiation. From the standpoint of a practically working neurosurgeon, these early attempts to develop radiosurgery soon necessitated an analysis of possible clinical applications. This gave rise to the formulation of new therapeutic arguments, rationales, and principles, tracks of thought that were less obvious for the great majority of brain surgeons. For example, when it came to advocating radiosurgical treatment of benign intracranial tumors, the new radiosurgical therapeutic principle was not removing but inactivating and possibly obliterating the neoplasm. Such thoughts proved provocative to the devoted supporters of microsurgery as a superior method of management and were even insulting to its great masters. It is an understatement to claim that the use of high-energy beams, for example, from a synchrocyclotron, in the exclusive clinical setting is a less convenient, if not impossible, technique. Thus, Leksell’s idea of a more handy “beam knife” was conceived. In this, a large number (i.e., as many as technically possible) of cobalt 60 radiation sources, distributed in a half-sphere around the patient’s head, would safely allow a simultaneous firing of beams from all these sources, collimated as well as possible, and directed to a preselected intracranial target (volume). An absolute prerequisite was that a clinically well-proven stereotactic technique should be employed. Importantly, Leksell’s focus from the very beginning was on the possible destruction (or stimulation) of deeply located tracts and nuclei in the brain, within the functional brain surgery. The development of “psychosurgical procedures without opening the skull” was a first technical goal in his early considerations. Similarly, a “nonbloody” thalamotomy for parkinsonism (or pain) was another beckoning application. Thus, in the first GK, the technical aim was to obtain slit-formed beam apertures, making the composite ionization pattern in the tissue as “cutlike” as possible. Therefore, during the period of the unit’s construction, its nickname was “the beam knife.” There are strong reasons to assume that Leksell, a clinical surgeon himself, made manifest the term radiosurgery when inventing the GK. Already in 1951 he had introduced the term.5 For him, the GK was nothing but “a surgical tool,” in many aspects analogous to the cautery loop, the instrument for cutting or digging out tissue, normal or neoplastic, in traditional surgery. This comparison is what he himself often made. Moreover, it fixed his standpoint that radiosurgery should remain surgery, essentially without overlap radiotherapy, except for the fundamental fact that the same physical agent was used, beams of ionizing radiation.
Stereotactic Radiosurgery from Notion to Practice
Erik Olof Backlund
The Development of Radiosurgery
The Development of Neurosurgical Radiosurgery
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