Radiation Therapy

Radiation oncology is the discipline of human medicine focused on generation, conservation, and dissemination of knowledge concerning etiology, prevention,rift gold and treatment of cancer and some benign diseases involving special expertise in the therapeutic applications of ionizing irradiation (Smith and McKenna, 2004). It addresses the therapeutic uses of ionizing irradiation given either alone or in combination with other treatment modalities, such as surgery or chemotherapy. Radiation oncology also includes investigation of basic principles of tumor biology, the biologic interaction of irradiation with tissues, normal or malignant, as well as the physical principles of therapeutic irradiation. As a medical profession, radiation oncology involves patient care, scientific research, and education of professionals within the discipline. Radiation therapy is a clinical modality dealing with the use of ionizing irradiation in the treatment of patients with cancer and occasionally benign disease (Smith and McKenna, 2004). Its aim is to deliver a precisely measured irradiation dose to a defined tumor volume with as minimal damage as possible to surrounding healthy tissue, thus resulting in tumor eradication, improved quality of life, and prolonged survival. Indications for radiation therapy include cases in which it can improve either local control, hence overall survival, or ameliorate symptoms of the disease.

The aim of therapeutic irradiation can be either curative or palliative (Price and Sikora, 2005). The aim of curative radiation therapy is to eradicate the tumor and cure the patient, in cases in which the patient is willing to accept a small risk of significant adverse events in return for the possibility of cure. Palliative radiation therapy has the aim of either ameliorating the symptoms of the disease or preventing it to increase the quality of life without a significant risk of serious adverse events. Specific issues of radiation oncology are the volume, techniques, and the dose (Halperin et al., 2004). Although the appropriate volume to be irradiated needs to be specified for achieving the desired goal, the appropriate technique to irradiate a specified volume of tissue must also be taken into account. There are two techniques: teletherapy, using either distant-positioned focal source of cobalt-60 machines or linear accelerators as external beam treatment machines, and brachytherapy, with various radioactive isotopes that could be used interstitially, intracavitary, or intraluminally, or as molds. Although teletherapy remains the standard technique for the majority of patients, there is an increasing interest in the use of novel brachytherapy applications in tumors such as prostate cancer. Finally, the irradiation dose must be chosen by taking into account total dose, total number of fractions, number of fractions per day, irradiation dose per fraction,rift gold and the overall treatment time. Choice of irradiation dose is therefore a complex issue encompassing treatment goals, volumes, and techniques, as well as knowledge of radiobiology, such as the dose–response relationship for a particular tumor type and normal tissue tolerance.