Image guided radiation therapy and Intensity modulated radiation therapy
Modern radiological techniques involve methods that enable radiation therapy to be offered to patients with precision and great accuracy. Radiotherapy kills cancer cells and stops the cancer from multiplication thereby eliminating the cancer. Radiotherapy may be used to shrink large tumors prior to surgery; after surgery to sterilize microscopic disease or with chemosensitization to cure certain cancers.
Image-guided radiation therapy (IGRT)
IGRT involves the use of in-room imaging during a course of radiation therapy. Machines that are used commonly are the linear accelerators, Brachytherapy, Cyberknife, Proton therapy, or Tomotherapy that have the ability to enable the treating Oncologists to view radiation therapy in a series of images in real-time. These highly specialized equipments used computer-based technology to derive these images. To protect normal tissues, necessary adjustments through radiation dose calculations are done by the Oncology team so that only the tumor receives the effects of radiation. Images may be in the form of kilovoltage or megavoltage reconstructed computerized tomography (CT) and magnetic resonance imaging (MRI) scanning. Other forms of imaging may also be used from ultrasound scanning and X-ray films.
The patient begins the procedure by markers placed on the body surface where radiation therapy has to be given. In certain cases, markers may be implanted within the body for the precise localization for radiation therapy especially in organs that move during treatment e.g.lungs and liver. Other more sophisticated methods may be used alongside IGRT to protect critical organs that may be located within close proximity to tumors. One such method is planning the treatment with intensity-modulated radiation therapy or IMRT.
Intensity-modulated radiation therapy (IMRT)
Intensity-modulated radiation therapy (IMRT) is an advanced method that is able to deliver accurate amount of radiation to the tumor alone without harming the areas surrounding the tumor. The radiation beam can be delivered in a controlled 3-dimensional mode adapting to the shape of the malignant growth with the aid of CT, PET-CT, and MRI imaging as described earlier. Technically, the beams come in different directions with adjustable dosages providing maximal radiation to the tumor itself and reductions in radiation dosage around the tumor. This type of radiotherapy is customized and requires careful and meticulous planning before administering to each patient. Most often a contrast is injected though veins of the patient during the planning CT/MRI to ensure better visualization by the specialists. Patients are scheduled for treatments for at least 5 times a week for at least 5-8 weeks depending on the type of tumor involved. Each treatment session can vary from about 10-30 minutes. Side-effects such as headache, hair loss and soreness to the mouth and treated areas, nausea, vomiting, diarrhea, urinary changes may occur during the course of treatment and are self-limiting. Patients can go through the treatment with minimal medication to manage the side effects. Most of the side effects of treatment with radiation resolve over 4-6 weeks post treatment and hair regrowth starts within 3 months after completion of therapy. Currently, IMRT is being used extensively to treat all types of cancers including prostate, head and neck, and the central nervous system. IMRT has also been used to treat breast, thyroid, and lung cancers, as well as in gastrointestinal, gynecologic malignancies, and certain types of sarcomas. IMRT may also be of benefit in treating childhood cancers.