What is a fraction in radiotherapy?
Radiotherapy fractions The full dose of radiation is usually divided into a number of smaller doses called fractions. This allows healthy cells to recover between treatments. You have the fractions as a series of treatment sessions that make up your radiotherapy course.
Why is fractionation used in radiotherapy?
Fractionation in the context of radiotherapy is the process of dividing a dose of radiation into multiple “fractions”. This practice seeks to maximize the destruction of malignant cells while minimizing damage to healthy tissues.
How many fractions are in radiation therapy?
There are five different radiation dose fractionation schedules now under active investigation in clinical radiotherapy: (1) hyperfractionation, in which conventional radiation doses per fraction (150–300 rad) are given two to three times daily; (2) superfractionation, in which small radiation doses per fraction (55– …
What does radiotherapy mean?
Radiotherapy means the use of radiation, usually x-rays, to treat cancer. You might have radiotherapy from inside the body, called internal radiotherapy. Or external radiotherapy, which is from outside the body.
What is radiotherapy measured in?
Standard dose Gray (Gy) is the unit used to measure the total amount of radiation that the patient is exposed to. This can also be recorded as centigray (cGy), which is 0.01 of a single Gy unit. Adjuvant therapy doses typically range from 45 to 60 Gy for the treatment of breast, head, and neck cancers.
What element is used in radiotherapy?
Because of this, radioactive iodine (also called radioiodine or iodine-131) can be used to destroy the thyroid gland and thyroid cancer with little effect on the rest of the body. This treatment is often used after thyroid cancer surgery to destroy any thyroid cells left behind.
What is the principle of radiotherapy?
Radiotherapy ionises chemicals within cells. The crucial lesion is DNA strand breakage which may be repaired or fixed and lead to apoptotic or mitotic cell death. Different types of normal and malignant cells vary in their susceptibility to ionising radiation.
What is fractionation sensitivity?
The dependence of the iso-effective radiation dose on the dose per fraction. Usually quantified by the α/β ratio – a high fractionation sensitivity is characterised by a low α/β ratio.
What is fractionation in pharmacology?
A laboratory test or process in which blood or another fluid is broken down into its components. Fractionation can be used to assess the proportions of the different types of cholesterol in a blood sample. Mentioned in: Cholesterol Test, Radiation Therapy. Gale Encyclopedia of Medicine.
What is fractionation in biology?
Cell fractionation is a procedure that allows different parts of a cell to be separated from each other using centrifugation. The process relies on differences in size and density of the organelles.
How do you calculate radiation absorption?
Absorbed dose (D) is defined as the mean amount of energy deposited per unit of mass (dm) as a result of the interaction of ionising radiation and matter. The unit of absorbed dose is the gray (Gy): 1 Gy = 1 J/kg. An old but still used unit of absorbed dose is rad: 1 rad = 0.01 Gy.
What is the main principle of radiotherapy?
Radiation works by making small breaks in the DNA inside cells. These breaks keep cancer cells from growing and dividing and cause them to die. Nearby normal cells can also be affected by radiation, but most recover and go back to working the way they should.
How are electrons used in radiation therapy?
Electron beam radiotherapy is treatment using a radiation beam of particles called electrons. This radiation is strong enough to kill cancer cells but does not penetrate more than a few centimetres beyond the surface of the skin. It is given using equipment similar to a large x-ray machine.
What are early responding tissue?
Based on their time course, early reactions in tissues are defined as those observed within weeks after the (onset of) radiation exposure, e.g. within the first 90 days after the start of radiotherapy.
What is cell fractionation in biochemistry?
Cell fractionation is the process used to separate cellular components while preserving individual functions of each component. This is a method that was originally used to demonstrate the cellular location of various biochemical processes.
What is radiotherapy fractionation?
Radiation therapy is usually divided or “fractionated” over a treatment course lasting multiple weeks. Fractionation in the context of radiotherapy is the process of dividing a dose of radiation into multiple “fractions”.
Is fractionation of the radiation dose necessary for tumor control?
The reasoning may be flawed, but the conclusion proved to be valid: Fractionation of the radiation dose produces, in most cases, better tumor control for a given level of normal tissue toxicity than a single large dose. Now, more than 80 years later, we can account for the efficacy of fractionation based on more relevant radiobiologic experiments.
When was multifraction radiotherapy first used?
FIGURE 23.1 Conventional multifraction radiotherapy was based on experiments performed in Paris in the 1920s and in the 1930s. Rams could not be sterilized with a single dose of x-rays without extensive skin damage, whereas if the radiation were delivered in daily fractions over a period of time, sterilization was possible without skin damage.
What is the effect of dose fractionation on radiosensitivity?
Dose fractionation increases the radiosensitivity of tumor tissue, as increased oxygenation of hypoxic tumor cells occurs between fractions. Sheldon Kwok,