32.3 Therapeutic Uses of Ionizing Radiation
3 min read•june 18, 2024
uses ionizing radiation to destroy cancer cells by damaging their DNA. It's measured in and typically given in fractions over weeks. The total dose varies from 20 to 80 Gy, depending on cancer type and stage.
There are two main types: (EBRT) and radioactive implants (). are also used, containing radioactive isotopes that target specific cancer cells. These methods aim to maximize tumor damage while minimizing harm to healthy tissue.
Radiotherapy Principles and Techniques
Principles of radiotherapy dosage
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- employs ionizing radiation to damage or destroy cancer cells by damaging their DNA, disrupting cell division and inducing cell death
- Cancer cells are more vulnerable to radiation damage compared to healthy cells due to their rapid division and impaired DNA repair mechanisms
- Radiotherapy dosage for cancer treatment is measured in (Gy), which represents the absorption of 1 joule of radiation energy per kilogram of matter (tissue)
- The total radiation dose is typically divided into smaller fractions administered over several weeks () to allow healthy cells to recover between treatments while continuously damaging cancer cells
- The total dose varies from 20 to 80 Gy, depending on the type and stage of cancer (early-stage breast cancer: 40-50 Gy over 3-5 weeks)
- is crucial to ensure optimal tumor coverage while minimizing damage to healthy tissues
External beam vs implant techniques
- External beam radiation therapy (EBRT) delivers radiation from an external source, usually a , directing high-energy or at the tumor site
- (3DCRT) shapes the radiation beam to conform to the tumor's shape, minimizing exposure to healthy tissue
- (IMRT) modulates the radiation intensity to deliver higher doses to the tumor while sparing surrounding healthy tissue
- Radioactive implants (brachytherapy) involve placing radioactive sources directly inside or near the tumor, allowing for high radiation doses to the tumor with minimal exposure to surrounding healthy tissue
- involves implanting radioactive seeds or pellets directly into the tumor (prostate cancer)
- involves placing radioactive sources in a body cavity near the tumor (cervical cancer)
Radiopharmaceuticals in cancer treatment
- Radiopharmaceuticals are drugs containing radioactive isotopes that can be administered orally, intravenously, or through direct injection into the tumor for targeted cancer therapy
- These drugs are designed to localize and accumulate in specific cancer cells through receptor binding (radiopharmaceuticals bind to receptors overexpressed on cancer cell surfaces) or metabolic uptake (increased uptake of compounds like glucose or amino acids by cancer cells)
- Radiopharmaceuticals emit radiation that damages cancer cell DNA, leading to cell death, and can be used alone or in combination with other cancer treatments (chemotherapy, external beam radiation therapy)
- Examples of radiopharmaceuticals used in cancer therapy include:
- Radioactive iodine (I-131) for thyroid cancer, as thyroid cells and thyroid cancer cells absorb iodine, allowing for targeted therapy
- for metastatic prostate cancer in the bones, as Radium-223 mimics calcium and is incorporated into bone, targeting bone metastases
Advanced Radiotherapy Techniques and Considerations
- focuses on using ionizing radiation to treat cancer and other diseases
- techniques improve the precision of radiation delivery to cancer cells while minimizing damage to healthy tissues
- , such as proton therapy, offers enhanced tumor targeting capabilities compared to traditional photon-based radiotherapy
- Managing is crucial for patient well-being and treatment compliance
- measures are implemented to safeguard patients, medical staff, and the public from unnecessary radiation exposure
Key Terms to Review (26)
3D Conformal Radiotherapy: 3D conformal radiotherapy is a type of external beam radiation therapy that uses advanced imaging and computer software to precisely shape the radiation beams to match the three-dimensional shape of the tumor. This technique aims to deliver a high dose of radiation to the cancer while minimizing exposure to surrounding healthy tissues.
Brachytherapy: Brachytherapy is a type of radiation therapy where a radioactive source is placed directly inside or next to the area requiring treatment. It is a targeted approach used in the treatment of various types of cancer, delivering a high dose of radiation to the tumor while minimizing exposure to surrounding healthy tissues.
Dose Planning: Dose planning is the process of determining the optimal radiation dose to be delivered during therapeutic uses of ionizing radiation. It involves carefully calculating and tailoring the radiation dose to effectively treat the target area while minimizing exposure to surrounding healthy tissues.
External Beam Radiation Therapy: External beam radiation therapy (EBRT) is a type of radiation therapy that uses high-energy particles or waves, such as X-rays or protons, to destroy cancer cells. It is a common treatment option for various types of cancer, where the radiation source is positioned outside the body and aimed directly at the tumor site.
Fractionation: Fractionation is the process of separating a complex mixture, such as radiation or a chemical compound, into its individual components or fractions. This technique is commonly used in various fields, including nuclear medicine, to isolate specific isotopes or radioisotopes for therapeutic applications.
Gamma rays: Gamma rays are a form of electromagnetic radiation with the highest photon energies and shortest wavelengths. They are typically produced by nuclear reactions, radioactive decay, and certain types of astronomical phenomena.
Gamma Rays: Gamma rays are a type of high-energy electromagnetic radiation with the shortest wavelength and highest frequency in the electromagnetic spectrum. They are produced by the radioactive decay of atomic nuclei and have the ability to penetrate deep into matter, making them useful in various applications.
Gray: Gray, in the context of ionizing radiation, refers to a unit of measurement that quantifies the amount of energy absorbed by living tissue when exposed to radiation. It is used to assess the biological effects and therapeutic applications of ionizing radiation.
Gray (Gy): Gray (Gy) is the SI unit for the absorbed dose of ionizing radiation, representing the absorption of one joule of radiation energy per kilogram of matter. It measures the amount of energy deposited by radiation in a substance.
Intensity-Modulated Radiotherapy: Intensity-Modulated Radiotherapy (IMRT) is a type of external beam radiation therapy that uses computer-controlled linear accelerators to deliver precise radiation doses to a tumor or specific area within the body. It is a highly advanced technique that aims to maximize the radiation dose to the target while minimizing exposure to surrounding healthy tissues.
Interstitial Brachytherapy: Interstitial brachytherapy is a type of internal radiation therapy where radioactive sources are placed directly inside or next to the tumor, allowing for targeted and localized delivery of radiation to the affected area. This technique is commonly used in the treatment of various types of cancer, including prostate, breast, and gynecological cancers.
Intracavitary Brachytherapy: Intracavitary brachytherapy is a type of radiation therapy where a radioactive source is placed directly inside a body cavity, such as the cervix, uterus, or vagina, to deliver targeted radiation treatment to tumors or cancerous growths. This technique allows for the precise delivery of high doses of radiation to the affected area while minimizing exposure to surrounding healthy tissues.
Iodine-131: Iodine-131 is a radioactive isotope of iodine that has a wide range of applications in both diagnostic and therapeutic uses of ionizing radiation in the medical field. It is a key term in the context of the topics 32.1 Diagnostics and Medical Imaging and 32.3 Therapeutic Uses of Ionizing Radiation.
Linear accelerator: A linear accelerator, or linac, is a device that uses electromagnetic fields to accelerate charged particles to high speeds along a straight path. It is commonly used in particle physics experiments and medical applications.
Linear Accelerator: A linear accelerator is a type of particle accelerator that uses electric and magnetic fields to accelerate charged particles, such as electrons or protons, in a straight line. This technology is widely used in various applications, including medical treatments, scientific research, and industrial processes.
Particle Therapy: Particle therapy is a type of radiation therapy that uses subatomic particles, such as protons, neutrons, or heavy ions, to treat various types of cancer. Unlike traditional radiation therapy that uses X-rays or gamma rays, particle therapy precisely targets the tumor while minimizing damage to surrounding healthy tissues.
Radiation Oncology: Radiation oncology is a medical specialty that uses ionizing radiation, such as x-rays, gamma rays, and charged particles, to treat various types of cancer and other diseases. It involves the precise delivery of radiation to target and destroy cancerous cells while minimizing damage to healthy surrounding tissues.
Radiation Protection: Radiation protection refers to the methods and practices employed to safeguard individuals and the environment from the harmful effects of ionizing radiation. It is a critical consideration in the therapeutic uses of ionizing radiation, ensuring the responsible and effective application of this technology for medical purposes.
Radiation Side Effects: Radiation side effects refer to the unintended and potentially harmful consequences that can arise from the therapeutic use of ionizing radiation. These effects occur when the radiation interacts with the body's cells and tissues, leading to various physiological and biological changes that can negatively impact an individual's health and well-being.
Radiopharmaceuticals: Radiopharmaceuticals are radioactive substances used in medical imaging and therapy. They are designed to interact with specific biological processes or target specific tissues in the body, allowing for the diagnosis and treatment of various medical conditions.
Radiotherapy: Radiotherapy is a medical treatment that uses ionizing radiation to kill or control the growth of cancer cells. It targets specific areas of the body to minimize damage to healthy tissues.
Radiotherapy: Radiotherapy, also known as radiation therapy, is a type of cancer treatment that uses high-energy radiation, such as x-rays, gamma rays, or charged particles, to destroy cancer cells. It is a widely used and effective approach in the therapeutic uses of ionizing radiation.
Radium-223 Dichloride: Radium-223 dichloride is a radioactive drug used in the treatment of certain types of cancer, particularly metastatic castration-resistant prostate cancer. It is a targeted alpha therapy that delivers targeted radiation directly to cancer cells, helping to reduce tumor size and alleviate pain associated with bone metastases.
Therapeutic ratio: The therapeutic ratio is the comparison between the amount of ionizing radiation that damages healthy tissue and the amount that destroys cancerous cells. A higher therapeutic ratio indicates a more effective and safer treatment.
Tumor Targeting: Tumor targeting refers to the process of selectively delivering therapeutic agents, such as drugs or radiation, to cancer cells while minimizing the impact on healthy tissues. This is a crucial aspect of cancer treatment, as it aims to enhance the efficacy of the therapy while reducing side effects.
X-rays: X-rays are a form of electromagnetic radiation with very short wavelengths, typically ranging from 0.01 to 10 nanometers. They are widely used in various applications, particularly in medical imaging and treatments, due to their ability to penetrate soft tissues while being absorbed by denser materials like bones.