Radiation Therapy is involved with the use of radiation
(mainly gamma and x-rays) for the treatment of malignant tumors. The medical
physicist plays a pivotal role in ensuring that the right radiation dose
is delivered to the patient. There have been several recent technological
developments in the field such as 3D conformal radiation therapy and intensity
modulated radiation therapy (IMRT).
IMRT is designed to address a major limitation of conventionally delivered
radiotherapy: its inability to restrict the treatment beam to the tumor-bearing
tissue. Unlike conventional treatment, with IMRT, the intensity of radiation
is made to vary across the beam. Inverse planning algorithms are used
to determine optimal intensity-modulation. A dynamic multileaf collimator
is used to sweep opposing pairs of tungsten leaves across the field.
In 3D conformal radiation therapy, the prescribed dose is shaped to match
the 3D target volume of cancer cells. Computers are also used to generate
beam’s eye-view (BEV) images that present a patient’s anatomy
as it would appear to a viewer located at the radiation source. BEV images
are used to aid in determining which x-ray beam orientation would yield
the best view of cancer cells without irradiating too much normal tissue.
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9-Field Head & Neck IMRT Case: Int J Radiat Oncol Biol Phys 2001;51:880-914 |
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