Journal of Medical Physics
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Year : 2011  |  Volume : 36  |  Issue : 1  |  Page : 29-34

Influence of photon energy on the quality of prostate intensity modulated radiation therapy plans based on analysis of physical indices

1 Department of Radiation Oncology, G. Kuppuswamy Naidu Memorial Hospital, India
2 Department of Physics, PSG College of Technology, India
3 Department of Radiation Physics, Kidwai Memorial Institute of Oncology, India

Correspondence Address:
Sundaram Thangavelu
V. N. Cancer Centre, G. Kuppuswamy Naidu Memorial Hospital, P. N. Palayam, Coimbatore - 641 037
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0971-6203.75469

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The goal of the present study was to study the effects of low- and high-energy intensity-modulated photon beams on the planning of target volume and the critical organs in cases of localized prostate tumors in a cohort of 8 patients. To ensure that the difference between the plans is due to energy alone, all other parameters were kept constant. A mean dose volume histogram (DVH) for each value of energy and for each contoured structure was created and was considered as completely representative for all patients. To facilitate comparison between 6-MV and 15-MV beams, the DVH-s were normalized. The different parameters that were compared for 6-MV and 15-MV beams included mean DVH, different homogeneity indices, conformity index, etc. Analysis of several indices depicts more homogeneous dose for 15-MV beam and more conformity for 6-MV beam. Comparison of all these parameters showed that there was little difference between the 6-MV and 15-MV beams. For rectum, 2 to 4 % more volume received high dose with the 6-MV beam in comparison with the 15-MV beam, which was not clinically significant, since in practice much tighter constraints are maintained, such that Normal Tissue Complication Probability (NTCP) is kept within 5 %. Such tighter constraints might increase the dose to other regions and other critical organs but are unlikely to increase their complication probabilities. Hence the slight advantages of 15-MV beam in providing benefits of better normal-tissue sparing and better coverage cannot be considered to outweigh its well-known risk of non-negligible neutron production.

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