🎯 Types and Delivery Methods
Radiotherapy is primarily delivered in two ways, based on the location of the radiation source relative to the patient.
1. External Beam Radiation Therapy (EBRT)
This is the most common type. A machine outside the body directs high-energy beams at the tumor site.
Linear Accelerator (LINAC): The large machine used to generate and precisely aim the radiation beams. It rotates around the patient, delivering radiation from multiple angles.
Advanced Techniques (Conformal Therapy):
Intensity-Modulated Radiation Therapy (IMRT): Uses computer-controlled, customized beam shapes and varying intensities to precisely sculpt the radiation dose to the exact shape of the tumor, sparing critical nearby organs.
Image-Guided Radiation Therapy (IGRT): Uses imaging (like CT or X-rays) before and sometimes during the treatment session to ensure the patient and tumor are in the correct position, especially useful for tumors that move (like lung or prostate).
Stereotactic Radiosurgery (SRS) / Stereotactic Body Radiation Therapy (SBRT): Delivers extremely high doses of radiation with pinpoint accuracy in just 1 to 5 fractions. Used for small, well-defined tumors, particularly in the brain, spine, or lung.
Proton Therapy: Uses beams of protons instead of X-rays. Protons deposit most of their energy at a specific, controlled depth within the tissue (Bragg Peak), after which the dose drops sharply to zero, offering superior protection to tissues beyond the tumor.
2. Internal Radiation Therapy (Brachytherapy)
This involves placing a radioactive source directly in or near the tumor.
Mechanism: The radiation source (often tiny seeds, pellets, or wires) delivers a high dose directly to the cancer while the dose rapidly falls off outside the target area, minimizing impact on surrounding healthy tissue.
Types:
Permanent: Tiny radioactive seeds (often Iodine-125) are left in the body, typically for prostate cancer, where they slowly lose their radioactivity over time.
Temporary: High-dose rate (HDR) sources are placed inside a catheter or applicator for only a few minutes at a time and then removed. Used for cancers of the cervix, uterus, and breast.