Journal of Medical Physics
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Year : 2022  |  Volume : 47  |  Issue : 4  |  Page : 336-343

Does fluence smoothing reduce the complexity of the intensity-modulated radiation therapy treatment plan? A dosimetric analysis

1 Department of Radiotherapy, Alexis Multispecialty Hospital, Nagpur, Maharashtra; Department of Physics, Rabindranath Tagore University, Bhopal, Madhya Pradesh, India
2 Department of Radiation Oncology, Gandhi Medical College, Bhopal, Madhya Pradesh, India
3 Department of Physics, Rabindranath Tagore University, Bhopal, Madhya Pradesh, India

Correspondence Address:
Dr. Suresh Yadav
Department of Radiation Oncology, Gandhi Medical College, Bhopal - 462 001, Madhya Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jmp.jmp_81_22

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Background: Intensity-modulated radiation therapy (IMRT) may have too many peaks and valleys, making the treatment plan undeliverable. When there are too many fluency differences between adjacent pixels in the X or Y directions, the X and Y smoothing factors are utilized as weighting factors to penalize this behavior. Generally, a high degree of complexity is accompanied by many monitor units (MUs), large number of segments, small sized segments, and complex segment shapes. The degree of plan delivery uncertainty can all increase with a higher detailed fluence map. Aim: This study aims to evaluate the dosimetric effects of various smoothing levels on the planning target volume (PTV) and organs at risk (OARs) for cervix cancer. Materials and Methods: IMRT treatment plans were re-optimized by combining several values of the X and Y penalty between 0 and 100. The dose–volume histogram assessed various dosimetric indicators for PTV and OARs. Additionally, gamma passing rates were evaluated and noted as an indicator of the complex treatment plan. Results: At X = 60, Y = 60 fluence map penalty, the conformity index (CI) value reached its highest value of 0.996 ± 0.004. At X = 0, Y = 0, the homogeneity index (HI) was determined to have a maximum value of 0.0628 ± 0.0235. The highest and lowest MU values were 2424.30 ± 471.12 and 1087.80 ± 91.57, respectively, with X = 0, Y = 0 and X = 100, Y = 100. At X = 100, Y = 100, the gamma passing rate reaches its highest value of 99.28% ± 0.44% and minimum value of 85.93% ± 3.87% at X = 0, Y = 0. Conclusion: The CI and HI values showed no discernible fluctuation, and the OAR doses were barely affected as smoothing was increased. When the smoothing factor was raised, the number of MUs sharply dropped, and a decrease in the number of segments and higher gamma passing rates were also seen.

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