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Term
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Definition
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External Beam Radiation Therapy
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Irradiation of tissue from sources at a distance (80-100cm) from the body using linear accelerators.
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Fiducial Markers
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Radiopaque markers used to mark the location of the prostate and other anatomy (lung,
breast) to track relative position of a tumor over the course of therapy.
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Field
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Refers to the radiation beam location or angle.
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Intensity Modulated Radiation Therapy (IMRT)
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A type of three-dimensional conformal radiation therapy (3D CRT) that requires detailed
treatment planning. The IMRT beam is individually prescribed for targeted patient
delivery. IMRT treatments are no longer in duration than standard 3D CRT treatments.
IMRT incurs different challenges than 3D CRT such as managing patient motion. Since
IMRT doses are more focused in delivery intense side effects may be seen in normal
tissues.
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Ionizing Radiation
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A type of radiation energy used in diagnostic and therapeutic radiology. All ionizing
radiation has the potential to damage human cells.
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Irradiate or Irradiation
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The act of exposing tissue to radiation therapy.
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Medical Physicist
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A medical physicist is responsible for the quality assurance and delivery of radiation
therapy. They qualify new equipment installations (commissioning) and oversee most
of the day-to-day patient treatment delivery. Physicists are also responsible for
the service and operation of their cancer center’s radiation medical equipment.
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Organ Motion
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Organs, which contain cancer cells or tumors, can be treated with radiation. Organs
may move during radiation therapy delivery. Organ motion occurs because physiologic
changes occur in the body from moment-to-moment (such as respiration and/or bladder
or rectal filling/emptying). Organ motion is important because it may prevent the
radiation beam to accurately focus on the tumor target during the course of radiation
therapy treatments.
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Organs at Risk
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Organs at risk (OAR) are defined as tissues that show a higher radio-sensitivity
than normal tissue. Therefore, they have to be spared over the course of the radiation
treatments. OAR may shift over time and their size and shape may not remain consistent.
Organ motion is considered during the treatment planning phase by adding a safe
margin in which to compensate for this uncertainty.
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Radiation Oncologist
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Physicians who are specialty-trained and board-certified in the treatment of cancer
patients with therapeutic radiation.
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Radiation Therapy
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Refers to the use of energy, in the form of x-rays, sent to target anatomy with
the intent to kill cancer cells.
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Radiation Therapist
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Healthcare professionals trained in the delivery of therapeutic ionizing radiation
to patients.
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Toxicity
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Side effects capable of causing injury or death, in this case, of ionizing radiation
to healthy tissues.
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Transrectal
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Refers to passing an introducer needle through the rectum to reach the prostate.
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Transrectal Ultrasound or TRUS
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A method of imaging the prostate when the imaging transducer is positioned in the
rectum.
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Treatment Couch
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A table commonly referred to as “the couch”. The couch is located in the treatment
room and the patient is positioned on the couch in a very precise and repeatable
fashion to align to isocenter. The couch is movable manually or electronically.
Some treatment couches have an indexing method or may have the capability to improve
reproducibility in patient positioning. There are internal encoders that indicate
movement of the table in millimeter measurements.
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Treatment Margin
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Treatment planning techniques that adds a safety margin around a tumor or target.
These margins assist in preventing irradiation of healthy tissues.
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Treatment Room
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A shielded room in a facility where a linear accelerator system is used to deliver
radiation therapy to a patient.
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Treatment Course
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The radiation delivery treatment schedule that is prescribed by the physician for
each patient based on that patient’s diagnosis. Typically, a two-month period of
time is required.
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Treatment Field
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A single surface area, as defined by the collimated radiation beam, delivered by
the treatment machine. Term often used synonymously with treatment port. A single
treatment region may have one or more treatment ports converging upon it.
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Treatment Plan
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An ensemble of radiation exposure beams or sources designed to produce a prescribed
dosage pattern in and for the patient; includes spatial and temporal distributions.
Planning radiation treatment is done on a computer system using CT, digitally reproduced
radiographs (DRRs) or diagnostic x-rays.
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X-Ray (x-ray)
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Ionizing radiation energy that can be used for therapeutic or diagnostic radiology
procedures. In the case of radiation therapy, the beams are therapeutic.
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