Partial Block Technique for Radiation Therapy of Lung Cancer with Dynamic Multi-leaf Collimator

ABSTRACT

PURPOSE: A spinal cord partial block technique (PBT) with dynamic multileaf collimator (dMLC) for the reduction of the spinal cord dose while keeping the tumor dose unchanged has been developed and its effectiveness has been examined. MATERIALS AND METHODS: Conventional 3-D conformal therapy treatment plan is deigned prior to the PBT application. Beam parameters such as, number of beams, beam directions were determined during 3-D conformal therapy planning process. The shape and the weight of the partial block for optimizing the dose distribution are designed with the forward intensity modulated radiation therapy (fIMRT). Eight cases of lung cancer, in which it was found to be impossible to deliver enough doses to targets with the conventional technique because the doses of the normal lungs or the spinal cords were over the tolerance limit, are used to verify the usefulness of this technique. Comparison of the dose volume histogram (DVH) is performed to compare the treatment plan. RESULTS: PBT plan cauld reduce the maximum dose to the spinal cord up to 29.7% and the mean dose to the lungs up to 11.1%. CONCLUSION: All of the cases showed that the PBT plans are better than the conventional 3-D plans and the spinal cord doses or the normal lung doses can be reduced to tolerance limit