IMRT:Radiobiological Consideration
Abstract
Intensity-modulated radiation therapy (IMRT) is a technique of radiation delivery developed to improve target dose confornity and normal tissue sparing. The dose distributions conform tighty to the 3D shape of the target by varying the beam intensity across the shaped fields. The complexity of the technique requires the longer treatment time for one fraction especially in the step and shoot technique. The reported total treatment times are varied from 15 min to as long as 30 min. The impact of such prolonging of time on the biological effects should be concemed.
The doses to normal tissue in IMRT technique is another aspect to be considered. The use of multileaf collimator for shaping the beam that gives rise to more leakage radiation between the leaves, the use of more field that reflects the bigger volume of normal tissue exposed to low dose radiation, and the higher total body dose as the monitor unit in beam modulation increased, these all affect the normal tissue dose. As a consequence, the risks of second malignancies after IMRT are of concem.
Therefore, the benefit and risk of using the IMRT will be focused in this review. The incorporation of biological variable into the treatment planning process to maximize the efficacy of IMRT will be discussed.
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