The evolution of stereotactic radiosurgery in neurosurgical practice.

INTRODUCTION: Stereotactic radiosurgery (SRS) was born in an attempt to treat complex intracranial pathologies in a fashion whereby open surgery would create unnecessary or excessive risk. To create this innovation, it was necessary to harness advances in other fields such as engineering, physics, radiology, and computer science. METHODS: We review the history of SRS to provide context to today's current state, as well as guide future advancement in the field. RESULTS: Since time of Lars Leksell, the young Swedish neurosurgeon who pioneered the development of the SRS, the collegial and essential partnership between neurosurgeons, radiation oncologists and physicists has given rise to radiosurgery as a prominent and successful tool in neurosurgical practice. CONCLUSION: We examine how neurosurgeons have helped foster the SRS evolution and how this evolution has impacted neurosurgical practice as well as that of radiation oncology and neuro-oncology.

Historical Aspects of Stereotactic Radiosurgery: Concepts, People, and Devices.

Stereotactic radiosurgery is a modern discipline that emerged after World War II. It represents a synthesis of an approach to patient care that was not immediately embraced by either neurosurgeons or radiation oncologists, but which has been shown, time and again, to be advantageous for the treatment of intracranial pathology. Indeed, stereotactic radiosurgical techniques are now being rapidly adapted and adopted for the treatment of extracranial malignant and benign disease. Any examination of the individuals, devices, and technological advances that permitted stereotactic radiosurgery to become a preferred approach for patient care cannot be absolutely comprehensive but can provide insights into the evolution of the specialty and potential future prospects for further improvements in patient care. As Shakespeare wrote in The Tempest, "What's past is prologue."

The First North American Clinical Gamma Knife Center.

A decision to develop a stereotactic radiosurgery center and install the first 201 cobalt-60 Gamma Knife in Pittsburgh was made in 1981 after gathering regional and leadership support. This was part of a 7-year quest that required overcoming barriers to a new technology unfamiliar to US regulatory authorities and insurance companies. The first patient was treated in August 1987. Since that time our center has installed each succeeding Gamma Knife device developed. During an initial 30-year experience we performed more than 14,750 patient procedures. In addition to patient care our Center's goal was to develop a major teaching and clinical research program that eventually led to the training of more than 2,500 physicians and medical physicists, the publication of more than 600 peer-reviewed clinical outcome research studies, and 4 books. This report summarizes the rationale for acquisition, the challenges and the early years, and then the evolution of our center which installed the first US 201 source Gamma Knife.

Stereotactic ablative radiotherapy for hepatocellular carcinoma: History, current status, and opportunities.

A variety of surgical and other local-regional approaches to the management of hepatocellular carcinoma (HCC) are in clinical use. External beam radiation therapy is a relative newcomer to the portfolio of treatment options. Advances in planning and delivery of radiation therapy, developing in parallel with and inspiring changing paradigms of tumor management in the field of radiation oncology, have led to growing interest in radiation therapy as a viable treatment option for HCC as well as other liver tumors. In this review, we discuss these advances, current trends in liver radiotherapy, as well as avenues of future clinical and basic research. Liver Transplantation 24 420-427 2018 AASLD.

Background knowledge in the early days.

The purpose of this chapter is to outline the medical facilities that were available to the inventors of radiosurgery at the time when the technique was being developed. This is achieved by describing in brief the timeline of discoveries relevant to clinical neurology and the investigation of neurological diseases. This provides a background understanding for the limitations inherent in the early days when investigations and imaging in particular were fairly primitive. It also helps to explain the choices that were made by the pioneers in those early days. The limitations of operative procedures and institutions designed to treat neurological diseases are also mentioned.

Some physics from 550 BC to AD 1948.

This chapter outlines terminology and its origins. It traces the development of physics ideas from Thales of Miletus, via Isaac Newton, to the nuclear physics investigations at the beginning of the twentieth century. It also outlines the evolving technology required to make the discoveries that would form the basis of radiosurgery. Up to the 1920s, all experiments on atomic structure and radioactivity had involved the use of vacuum tubes and naturally occurring radioactive substances. There was a need to make useable subatomic particles to obtain better understanding of the interior structure of atoms. Because of this, machines that could make atoms move at high speed were invented, known as particle accelerators. A new era had dawned. There is a brief mention of the effect of radiation on living tissue and of the units used to measure it.

Stereotactic and radiosurgery concepts in Sweden.

This chapter mentions again the requirements for a radiosurgery delivery system. There is a brief biography of the Swedish neurosurgeon Lars Leksell. Leksell's stereotactic frame and system is outlined. In 1951, Leksell wrote a seminal paper on radiosurgery that was a statement of concepts, all of which were remarkably well understood. The first cases treated with an available industrial X-ray machine are recounted. These early cases were successful enough to stimulate further efforts to improve the method.

From particle accelerator to radiosurgery.

This chapter outlines the requirements for machines that could perform radiosurgery. It also outlines the characteristics of the narrow beams used for this method. The reasons for limiting human treatments to the pituitary fossa are justified. The experiments, the results of which determined what was possible clinically, are outlined. The two methods of delivery of focused radiation are discussed: Bragg peak and beam crossover.

Stereotactic and radiosurgery research in Sweden.

This chapter starts with some comments upon the man who after Leksell was most instrumental in developing the Gamma Knife, the physicist Börje Larsson. Radiobiology experiments were carried out on rabbits and goats to determine and quantify the effects of focused fine beam radiation on the brain. The aim was to destroy the normal brain with a view to treating functional disease in the brain using focused radiation. The results in a few early patients are mentioned. The reasons for dissatisfaction with proton radiosurgery are presented.

The journey from proton to gamma knife.

It was generally accepted by the early 1960s that proton beam radiosurgery was too complex and impractical. The need was seen for a new machine. The beam design had to be as good as a proton beam. It was also decided that a static design was preferable even if the evolution of that notion is no longer clear. Complex collimators were designed that using sources of cobalt-60 could produce beams with characteristics adequately close to those of proton beams. The geometry of the machine was determined including the distance of the sources from the patient the optimal distance between the sources. The first gamma unit was built with private money with no contribution from the Swedish state, which nonetheless required detailed design information in order to ensure radiation safety. This original machine was built with rectangular collimators to produce lesions for thalamotomy for functional work. However, with the introduction of dopamine analogs, this indication virtually disappeared overnight.

The earliest gamma unit patients.

The inventors were very excited and drove the first patient from Stockholm over 100 km for the first treatment. The treatment was a technical success. The new machine was transported to Sophiahemmet (a private Stockholm hospital) and installed. A further eight patients were treated and assessed. At the start, there was no computerized treatment planning program, but this was soon developed and named KULA after the Swedish word for a sphere, since the actual treatment unit was spherical. The term Gamma Knife was first used later by the Pittsburgh group.

Stockholm radiosurgery developing 1968-1982.

For 14 years, Stockholm was the only location where a gamma unit was in use. During this period, a variety of indications were treated. The original machine had been designed with a view to treating functional disease. This was impractical as new medicines had tried up the referrals. So, the machine was used for certain tumors and vascular lesions. A new gamma unit was made this time with round collimators more suited to the task in hand. All in all, 762 patients were treated during this time with 209 vascular, 342 tumor, and 177 functional indications. There were also 34 diverse cases. All these cases were treated before the introduction of computerized imaging.

From Stockholm to Pittsburgh.

Leksell's conservatism led him to underestimate the demand for new gamma units. When two of his students wanted machines in, respectively, Buenos Aires and Sheffield, there was no possibility for manufacture in Sweden. Arrangements were made for a Swiss company to make two machines that were installed in the two centers but not without problems. Eventually, since the demand was there, arrangements were made to continue manufacture in Sweden by Elekta, the company that still makes them today. When these matters were settled, the first US model was installed in Pittsburgh. This became a crucial development, not only because the machine was now established in the United States but also because of the quality of the publishing from Pittsburgh, which was of the highest quality, honest and believable, and thus a potent impulse in the spread of Gamma Knife treatment.

Changing times and early debates.

The machine was soon being called the Gamma Knife. Its spread led to increasing numbers of papers from different centers but particularly Pittsburgh. As mentioned in the preface, the introduction of new methods in medicine is seldom without problems. There were a number of squabbles about the treatment of various indications. It was suggested that for AVMs, the GKS was unnecessary. For meningiomas, there was marked skepticism within the milieu itself in the early days. Metastases were not treated in Stockholm because of Leksell's opposition to the treatment of malignant disease, and indeed, these tumors became generally popular indications rather later. There was a thought that pituitary adenomas could be better treated with GKS but it proved too unreliable, and for these tumors, GKS remains an ancillary treatment method. The most marked disagreements were with respect of the vestibular schwannomas. This discussion continues to the present.

The development of dose planning.

In the very earliest days, there was no computerized dose-planning system. However, it was not long that the first dose-planning system KULA was developed in the mid-1980s. It soon became apparent that while this was geometrically accurate, it was not as visually attractive as programs used by other technologies. It had been designed in the era prior to computerized imaging and had only limited capacity for dosimetry. It was followed by GammaPlan, which has evolved over the years into a sophisticated multiparameter system with very advanced graphic features.

Changing the gamma knife.

The first Gamma Knife used helmets containing collimators of different diameters that increase the flexibility of the treatment. Changing these helmets was time-consuming and tedious. The original model that was introduced into the United States was the U model where the patient was inserted into the machine inward and upward, using hydraulics. A new simpler machine was devised called the B model where the patient simply moved in and out, but there was still the problem of changing helmets. Then, the C model was introduced, with a robot called the automatic positioning system that permitted the patient's position to be moved automatically. However, the helmets still had to be changed when collimators of different sizes were required. Finally, an entirely redesigned model called Perfexion was introduced where there were no helmets and the patient once placed in the machine would be treated completely following a single pressure on a button.

Supplementing the neurosurgical virtuoso: evolution of automation from mythology to operating room adjunct.

A central concept of scientific advancement in the medical and surgical fields is the incorporation of successful emerging ideas and technologies throughout the scope of human endeavors. The field of automation and robotics is a pivotal representation of this concept. Arising in the mythology of Homer, the concept of automation and robotics grew exponentially over the millennia to provide the substrate for a paradigm shift in the current and future practice of neurosurgery. We trace the growth of this field from the seminal concepts of Homer and Aristotle to early incorporation into neurosurgical practice. Resulting changes provide drastic and welcome advances in areas of visualization, haptics, acoustics, dexterity, tremor reduction, motion scaling, and surgical precision.