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Intensity-Modulated Radiotherapy (IMRT)

 In radiotherapy, a method is often needed that can adjust the dose distribution in all three dimensions as exactly as possible to the macroscopic or inferred microscopic boundaries between the tumor and normal healthy tissue. That is, the highest possible degree of what is termed conformity to the tumor shape is sought. Recently, in addition to the elaborate and until now not widely available therapy with heavy accelerated particles (for example, protons), "Intensity-modulated Radiotherapy" (IMRT) has also become available. Conventional linear accelerators equipped with so-called multileaf collimators (MLC) can utilize this technique to generate highly complex dose distributions.

Figure 1: Multileaf collimator (MLC)

Essentially, IMRT uses several small radiation fields with as much diversity in the field directions as possible to generate irregular irradiation intensities in the target area that yield a dose distribution with the maximal degree of conformity when superimposed on one another in three dimensions.
The example of an advanced paranasal sinus tumor shows how a high dosage can be applied to the extensive region covered by the tumor while the sensitive structures responsible for vision receive a much lower dosage.

Figure 2:  Paranasal sinus tumor

Another advantage of IMRT is the ability to administer different dosages to different sections of the target area based on their differing likelihoods of tumor infection.

Figure 3: Head and neck tumor

This method strives to reduce the amount of undesired radiation delivered to the rectum when treating prostate cancer.

Figure 4: Prostate tumor

IMRT has the advantage of being an effective treatment for numerous tumors in the head and neck region, abdomen and pelvis, while at the same time reducing the risk of side effects. This technique is currently used at the Mannheim Clinic to treat tumors in the head and neck, as well as advanced stomach and prostate cancer.

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last modified: 17-Apr-15
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