Jeremy C. Ganz

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.

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.

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.

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 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.

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 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.

Medical physics - particle accelerators - the beginning

This chapter outlines the early development of particle accelerators with the redesign from linear accelerator to cyclotron by Ernest Lawrence with a view to reducing the size of the machines as the power increased. There are minibiographies of Ernest Lawrence and his brother John. The concept of artificial radiation is outlined and the early attempts at patient treatment are mentioned. The reasons for trying and abandoning neutron therapy are discussed, and the early use of protons is described.

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. Leksells 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.

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.