ARRT Radiation Therapy key terms

The process of explaining a proposed treatment's purpose, risks, benefits, and alternatives so the patient can voluntarily agree to proceed, documented before therapy begins.

Skin reaction from radiation exposure ranging from redness and dryness to moist desquamation and ulceration in treated areas, managed with gentle cleansing, moisturizers, and avoidance of friction.

Painful inflammation and ulceration of the mouth and throat lining caused by radiation to the head and neck, which can impair eating and speaking and requires oral care and pain control.

A persistent, distressing sense of tiredness related to cancer or its treatment that is not relieved by rest and interferes with daily activities, managed with activity, sleep hygiene, and energy conservation.

A patient-education technique in which the patient restates information or demonstrates a skill in their own words, letting the therapist confirm understanding and correct misunderstandings.

Services and interventions that prevent or relieve treatment side effects and improve comfort and quality of life, such as nutrition support, pain management, skin care, and psychosocial counseling.

A radiation-protection principle meaning doses are kept As Low As Reasonably Achievable, considering economic and social factors, through shielding, good technique, and minimizing exposure time.

The three basic ways to reduce radiation exposure: limit time spent near a source, increase distance from it, and place appropriate absorbing material between the person and the source.

A badge or ring worn by radiation workers to record cumulative occupational dose, typically using optically stimulated luminescence or thermoluminescent technology, read periodically by a monitoring service.

The maximum permitted annual radiation dose for a radiation worker, set by regulators at 50 mSv (5 rem) to the whole body, intended to keep risk acceptably low.

The radiation dose received by a developing fetus; a declared pregnancy triggers dose estimates, extra shielding, and work-practice changes to keep exposure below regulatory limits.

A safety device that stops or prevents beam-on whenever the treatment room door is open, protecting staff and others from unintended exposure.

A clearly marked button inside the treatment room that immediately terminates beam-on or machine motion so the patient can be reached in an emergency.

A CT scan performed in the treatment position with immobilization and reference marks, producing images used to define anatomy and design the radiation plan.

The point in space where the rotation axes of the gantry, collimator, and couch intersect; treatment fields are usually planned to align with it.

The visible or palpable extent of tumor shown by imaging or clinical examination, defined before adding margins for microscopic spread or setup uncertainty.

The clinical target volume plus margins that account for organ motion and daily setup variation, ensuring the prescribed dose actually reaches the intended tissue.

Normal tissue or a critical structure near the target whose radiation tolerance may limit the dose that can be safely delivered.

A planning display showing anatomy as seen along the beam's central axis, used to choose beam angles and field shapes that avoid critical structures.

Tissue-equivalent material placed on the skin to build up dose in superficial tissue, used when the target lies near the surface or the beam would otherwise spare it.

A planning and delivery technique using non-uniform beam intensities, usually shaped by multileaf collimators, to wrap dose around the target while sparing nearby normal tissue.

A CT scan that records images at multiple phases of the breathing cycle, letting planners see how tumors and organs move with respiration.

A machine-specific unit of delivered output for a linear accelerator; the prescribed dose is converted to monitor units using depth-dose, output, and geometry data.

An imaging panel mounted opposite the beam source that captures images of the patient in the treatment position, used to verify field placement and anatomy.

An imaging system on the treatment machine that produces three-dimensional volumetric images at the treatment position, used for image-guided verification and repositioning before delivery.

A motion-management method in which the beam is delivered only during a selected portion of the breathing cycle, reducing the effect of tumor motion on the dose.

A brachytherapy technique in which a radioactive source is remotely driven into an implanted applicator after staff leave the room, delivering a high dose rate over a short time.

A shaped beam attenuator placed in the beam path to tilt the dose distribution across a field, compensating for missing tissue or producing a more uniform dose.

A brief pause before delivery in which staff confirm the patient's identity, treatment site, plan parameters, and imaging results all match the prescription.

A shaped piece of low-melting-point alloy placed in the electron applicator to define the treatment field and shield tissue outside the target.

The amount of radiation energy deposited per unit mass of tissue, expressed in gray, where one gray equals one joule per kilogram.

The dose at a given depth along the central axis, expressed as a percentage of the maximum dose, used to calculate dose at depth for a given field size.

The rule that radiation intensity from a point source decreases with the square of the distance, so doubling the distance reduces intensity to one quarter.

A widely used protocol for calibrating treatment machine output with an ionization chamber in water, converting measured charge into absorbed dose under reference conditions.

Tests performed at the start of each treatment day, such as output constancy, laser alignment, and safety checks, to confirm the machine works within tolerance.

A detector in which radiation ionizes gas and the resulting charge is collected to measure dose, commonly used for machine calibration and quality assurance.

A graph summarizing how much volume of a structure receives a given dose, used to evaluate target coverage and normal-tissue exposure.

A metric comparing two dose distributions using both dose difference and distance-to-agreement, with a pass rate showing how closely a measured plan matches the calculated plan.