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Objective To compare the effects of 6MV and 10MV-X-ray intensity modulated radiotherapy (IMRT) on non-small-cell lung cancer (NSCLC) . Methods We randomly selected 20 patients with NSCLC, 6MV and 10MV X-ray were used respectively for each NSCLC patient with IMRT plan design, the ADAC Pinnacle 8.0f treatment planning system was applied to provide the convolution/iteration algorithm, for the same target IMRT plan design with two kinds of energy. By comparing the dose volume histogram (DVH),PTV parameter (Dmean, Dmin and Dmax), conformal index (CI) and homogeneity index (HI),we analyzed the metrology parameters . Results 6MV and 10MV radiation therapy plan DVH, PTV parameters,CI,HI and isodose line was similar,no statistically significant differences. But target dose homogeneity and the degree of target coverage in high dose of 6MV plan was better than that in 10MV plan. Endanger organs (OAR) such as normal lung tissue, heart, esophagus and spinal cord had basically same dose amount. Conclusion 6MV X-ray plan may be the better choice of radiotherapy on NSCLC.
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PURPOSE: In order to improve dose homogeneity and to reduce acute toxicity in tangential whole breast radiotherapy, we evaluated two treatment techniques using multiple static fields or universal compensators. MATERIALS AND METHODS: 1) Multistatic field technique : Using a three dimensional radiation treatment planning system, Adac Pinnacle 4.0, we accomplished a conventional wedged tangential plan. Examining the isodose distributions, a third field which blocked overdose regions was designed and an opposing field was created by using an automatic function of RTPS. Weighting of the beams was tuned until an ideal dose distribution was obtained. Another pair of beams were added when the dose homogeneity was not satisfactory. 2) Universal compensator technique : The breast shapes and sizes were obtained from the CT images of 20 patients who received whole breast radiation therapy at our institution. The data obtained were averaged and a pair of universal physical compensators were designed for the averaged data. DII (Dose Inhomogeneity Index : percentage volume of PTV outside 95-105% of the prescribed dose), Dmax (the maximum point dose in the PTV) and isodose distributions for each technique were compared. RESULTS: The multistatic field technique was found to be superior to the conventional technique, reducing the mean value of DII by 14.6% ( p value<0.000) and the Dmax by 4.7% ( p value<0.000). The universal compensator was not significantly superior to the conventional technique since it decreased Dmax by 0.3% ( p value=0.867) and reduced DII by 3.7% ( p value=0.260). However, it decreased the value of DII by maximum 18% when patients' breast shapes fitted in with the compensator geometry. CONCLUSION: The multistatic field technique is effective for improving dose homogeneity for whole breast radiation therapy and is applicable to all patients, whereas the use of universal compensators is effective only in patients whose breast shapes fit inwith the universal compensator geometry, and thus has limited applicability.