The discovery of x-rays by Wilhelm Conrad Roentgen and natural radiation
by Henry Becquerel and Marie and Pierre Curie at the end of the 19th century was the
cornerstone for the development of a new discipline: Radiology. Soon after the
discovery of radiation, its diagnostic and therapeutic applications became evident and
for more than 100 years it has been utilized in the diagnosis and treatment of cancer.
During the last three decades the invention of computerized tomography, magnetic
resonance and the development of fractionated therapy have improved planning and
provided more accurate dosing. The current radiation techniques are capable of
delivering more individualized treatment with less harm to normal adjacent tissue;
therefore, more patients are treated with some form of radiation. Current radiation
treatment planning modalities include three-dimensional conformational radiation
therapy (3D-CRT), which accounts for tumor volume to approximate the radiation beam
to the shape of the tumor; intensity-modulated radiation therapy (IMRT), a more
advanced form of 3D-CRT, which utilizes varying intensities of radiation beams to
produce dosage distributions that are more precise than with 3D-CRT; and fourdimensional
radiation therapy (4D-RT) which not only accounts for volume and tumor
shape but also considers patient and organ motion. Radiation treatment modalities can
be divided into external beam radiation treatment, brachytherapy, and targeted
radiotherapy. This chapter will focus on the historical events that have led to the current
progress in radiation therapy, the generation of therapeutic radiation, mode of action,
current radiation planning and treatment modalities, and side effects.
Keywords: Cancer, radiation therapy, ionizing radiation, x-rays, threedimensional
conformational radiation therapy (3D-CRT), intensity-modulated
radiation therapy (IMRT), four-dimensional radiation therapy (4D-RT),
brachytherapy, external beam radiation treatment, targeted radiotherapy, radium,
nuclear reactors, particle accelerators, cycle accelerators, linear accelerator,
conformal radiotherapy, stereotactic radiotherapy, gamma knife, neutron beam
therapy, proton beam therapy, Bragg peak.
