Abstract :
Particle accelerators have played a major role in a national effort to test the efficacy of neutrons and heavy charged particles in the treatment of human cancer. Clinical trials are being conducted with neutrons of several different spectra, negative pi-mesons, protons, alpha particles, and neon, argon and carbon ions. These particles offer the possibility of improving the therapeutic ratio between malignant tumors and normal tissues by having either highly localized dose distributions (charged particles only) and/or an increased differential in the biological effect between tumor cells and normal cells. Until recently all of the heavy particle clinical trials have utilized accelerators designed for physics experiments which have often been remote from hospitals and patient care facilities. These accelerators include cyclotrons, syncrocyclotrons, linear accelerators, the linac sections of the Fermilab accelerator, and the Lawrence Berkeley Laboratory Bevalac (Bevatron plus Super HILAC). This paper will discuss the various accelerators, their respective particle modalities, and their advantages and disadvantages as radiotherapy facilities. It has long been recognized that the disadvantages of these research accelerators imposed limitations on the ability to deliver optimized radiotherapy and have therefore compromised the clinical trials. New technology has fostered the development of hospital based accelerators which have treatment delivery capabilities comparable to modern electron accelerators. Hospital based cyclotrons for neutron production are now a reality. The key sections of a linear accelerator which can produce either protons, neutrons, or pi-mesons in a hospital environment is in prototype.
