Radiotherapy is one the most important medical treatment of cancer. It uses ionizing radiations to destory and/or limit the growth of carcinogenic cells. It is administered by a multidisciplinary team of specialists including radiotherapist doctors, medical physicists, radiology heatlh technicians, heathcare and administration specialists. It is a subject strictly related to oncology, which is also very important in cancer treatment. Radiotherapy can be performed using internal or external radiation source, basing on this distinction it is possible to find these subcategories.
External beam radiotherapy
In this radiotherapy technique the radiation is generated outside the patient and it is directed on him to hit the treatment area. Usually this radiation is generated by a complex medical equipment called linear accelerator (LINAC). The main steps to provide this kind of treatment are: – identifying the treatment target area, using a computer tomography scan. This step is performed by a radiotherapist doctor. – treatment planning. This step is performed by a medical physicist, using complex simulation tools, to show the radiotherapist doctor the different ways to have the radiation reach the target area without damaging healthy tissues. – once the treatment plan is completed and approved by the radiotherapist doctor, the patient is called and the treatment performed. Different systems, such as LINAC, Tomotherapy equipment, Cyberknife Gammaknife systems, can be used in external beam radiotherapy.
The brachytherapy technique uses small encased ionizing radiation sources that are directly placed in the treatment target tissues. This technique is considered to be more invasive than external beam technique as sources placement requires surgery. Steps needed to provide a treatment are similar to those of the external bean technique. There is a preliminary survey of the patient’s anatomy through computer tomography or similar techniques. Then the medical physicist elaborates the treatment plan, calculating radiation sources placement in order to hit target tissues and to spare healthy tissues. Finally the radiotherapist doctor approves the plan and the treatment is performed.
This radiotherapy techniques uses radiation sources that are injected in the patient’s blood circulation. This kind of sources are called radiopharmaceuticals. The radioactive source is conveyed towards the target tissue by the metabolism of the patient. This conveying happens because of the nature of the source or because the sourced is tied to a molecule that attaches to the tumoral tissue. Healthy tissues are anyway affected by the radiation due to radiopharmaceutical transit or to its parasitic deposit. Steps to providing a treatment start with an anthropometric survey of the patient (weight, height, ecc.). In some cases pre-treatment surveys can be deeper an include the experimental administration of small radiopharmaceutical doses to perform a customized assessment of its conveying inside the body. Using the collected data the nuclear medicine specialist, in collaboration with the medical physicist, calculates the radiopharmaceutical quantity needed to grant the best ratio between hitting target tissues and sparing healthy tissues. For this kind of treatments hospitalization of the patient is usually required. Hospitalization is necessary to grant population security as excretions of patients subject to such treatments are usually radioactive and could cause an unwanted irradiation of other family members as well as strangers.
Most used radiopharmaceuticals are:
– Yttrium microspheres