Optimization in radiotherapy

Total body irradiation (TBI)

Diseases requiring bone marrow transplants, also called stem cell transplants, include leukemia, lymphoma, sickle cell disease and aplastic anemia, as well as some immunodeficiencies. As part of the conditioning process to prepare the patient for the bone marrow transplant, the patient may be treated with total body
irradiation (TBI). The purpose of TBI is to eliminate the underlying disease and to suppress the recipient's immune systems, thus preventing rejection of new donor stem cells. Once the conditioning treatment is complete, the patient receives the bone marrow transplant to restore healthy bone marrow function.

The goal for this research program is to design treatments that will not irradiate the whole body, but instead will only focus on the bone marrow. Such a treatments are no longer total body irradiation, but total marrow irradiation (TMI).

TMI treatment plans will be developed using a mathematical model that will provide for treatments resulting in the desired eradication of existing bone marrow cells while simultaneously avoiding organs and healthy tissues that do not require irradiation. This will be achieved by using intensity modulated radiation therapy (IMRT), a type of radiation therapy capable of delivering any distribution of radiation intensity from each beam. The resulting treatments will be better able to eradicate the patient's existing bone marrow with potentially fewer side effects from radiation overdose, thereby improving the patient's quality of life and preparation for a bone marrow transplant.

Elekta's Leksell Gamma Knife® PERFEXION™

The introduction of Elekta's Leksell Gamma Knife® PERFEXION™ has taken the field of stereotactic radiosurgery to a new level. Unlimited access to cranial volume and full automation approach open a new research area for the researchers who have been already working on the previous Lekshell Gamma Knife unit for years. Although this method is primarily designed to be performed on brain tumors, today, it is considered an effective treatment for several other conditions, including arteriovenous malformations and pituitary tumors.

The new capabilities of the PERFEXION™ unit require new methods of treatment plan design. In previous Gamma Knife® designs, the collimator (the component that adjusts the shape/location of the radiation delivery) had to be manually adjusted, rendering complex treatments too labor intensive for clinical viability. Because the movement of the collimator in the new PERFEXION™ unit is now automated, complex treatment plans that can very tightly conform to the targeted treatment area can be delivered in clinical settings.

In order to deliver a high quality treatment, we select collimator positions based on optimization methods. The optimization algorithms are designed to deliver an appropriate amount of dose to the target area while simultaneously avoiding sensitive healthy tissues, thereby leaving the patient with a high quality of life and fewer side effects after treatment.