A major area of research for the physics group at TJU Hospital is intensity modulated dose delivery. Although introduced a number of years ago, it is interesting to note the Intensity Modulated Radiation Therapy (IMRT) is not yet a routine treatment modality.

Some reasons for the slow spread of this new technology through the RT community are:

1. Inverse treatment planning has not been integrated into existing planning systems and the only commercially available stand-alone system is expensive.
2. A steep learning curve must be overcome in order to implement this technology.
3. Extensive Quality Control is required for safe treatment using this new technique.
4. Treatment times remain relatively long.
5. There is a concern that increased head leakage from the accelerator can lead to a greater dose reaching both the patient and personnel outside the treatment room.
6. No good methods have been developed for verifying dose delivery for IMRT.
7. Intra-fraction organ motion can cause undetected dose errors.
8. Inverse plans tend to have a higher than expected dose hetrogeneity.
9. The intensity maps produced by inverse planning are busy and hard to model with a multileaf collimator.

The medical physics group at TJUH has concentrated on developing IMRT approaches that are relatively easy to implement and that avoid many of the problems listed.

A main focus of the IMRT research effort at TJU is the use of forward treatment planning instead of the inverse approach. One of the aims of this work is to use forward planning to develop benchmark plans that can be compared with inverse plans as a method of showing that the new planning method is performing adequately. A second part of this research examines the hypothesis that forward planning can eliminate many of the problems listed above. For example, research conducted at TJUH has demonstrated that inverse treatment planning can result in dose distributions that have large dose inhomogeneity compared to traditional plans, and that the intensity patterns produced by the inverse planning process are complex and hard to deliver. The forward planning methods developed at TJU tend to control both of these problems while achieving acceptable "dose conforming" plans for complex target shapes.

Many of the problems listed above are believed to be related to the complexity of the intensity pattern. An intensity pattern with numerous extrema is hard to verify, leads to increased monitor units and increased leakage radiation, complicates the normal use of margins to allow for moving structures, and is hard to deliver in a short amount of time. Members of the physics group at TJUH are developing a new inverse planning algorithm that controls the complexity of the intensity maps for each field during the optimization process. It is believed that this approach will greatly simplify IMRT and help us achieve our goal of making this new treatment modality a safe and reliable reality for the general radiation therapy community.

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