Purpose The goal of this work is to investigate the field width dependence of the volumetric modulated arc therapy (VMAT) plan quality and to propose a half field method to irradiate large volumes effectively with VMAT. Materials and methods We compared four different VMAT methods; namely three full field (3ff), four full field (4ff), three half field (3hf), four half field (4hf). To evaluate the impact of the field width on VMAT plan quality, 12 different size PTVs were created in the virtual phantom and treatment plans generated for each PTV were compared. The effectiveness of our half field method was tested using computed tomography (CT) data of 10 nasopharyngeal carcinoma patients. Results In the virtual phantom study, organs at risk (OAR) mean dose, the maximum point dose, and Homogeneity Index (HI) were found to be field width dependent. Conformation Number (CN) was not significantly affected. In the clinical study, 4hf plans obtained statistically significant dose reduction at brainstem (P < 0.001), right parotid (P = 0.034), oral cavity (P < 0.001), larynx (P = 0.003), cochlea (P = 0.017), lips (P = 0.024), and Body‐PTV (P = 0.04) compared to 4ff plans. Conclusion Our results indicate that VMAT plan quality is dependent on the field width. Half field VMAT method, with the help of reduced field width, shows a clear advantage for the irradiation of large size targets compared to traditionally used full field VMAT plans.
The main goal of the present article is to elucidate the wave-particle duality problem by giving an unambiguous mathematical expression of the origin of the wave nature of particles. It is indicated that the wave nature of particles is originated from the multidimensional universe approach and under the one-dimensional universe assumption the wave nature vanishes. The one-dimensional universe assumption also gives a deterministic explanation for the double-slit experiment and answers how a single electron can interfere with itself. The locality paradox is also discussed. It is demonstrated that the same principle shows how a local measurement can determine the state of a distant system. The theoretical framework presented here may help us to understand various quantum physics phenomena. i.e., the superposition principle, wave function collapse, and entanglement.
Aim: The purpose of the present study is to compare hybrid [three-dimensional conformal radiation therapy-volumetric-modulated arc therapy (3DCRT-VMAT)] and helical tomotherapy (HT) techniques in terms of both planning target volume (PTV) and organs at risk (OARs) in the plans we made in locally advanced non-small cell lung cancer (NSCLC) patients Material and methods: Radiotherapy was planned for 15 locally advanced NSCLC patients with 2 different techniques. Large tumours with positive mediastinal lymph nodes were preferred. The prescription dose was determined as 60 Gy at 30 fractions. Results: Mean PTV volume was 602·5 cc (range: 265–1461). Mean total lung volume was 4264 cc (range: 1885–6803). Homogeneity index, Dmean, Dmax, D2 and V105 were found to be lower in HT, V100, total monitor units (MU) and total beam on time were found to be lower in the hybrid plan. Total lung Dmean was found to be 17 Gy in both techniques. V10 value was 42·85 in the hybrid plan and 48·67 in HT (p = 0·037). Heart Dmean was 14·5 Gy in the hybrid plan and 18·7 in HT (p < 0·001), and V30 values were 18·1 and 22·9, respectively (p = 0·009). Conclusion: Suitable dose coverage and OAR doses can be provided with both techniques. Especially the opposite lung, heart and oesophagus doses can be kept lower with the hybrid plan, and lower MU and shorter beam on time can be provided.
Multi-leaf collimator dose leakage in intensity-modulated radiotherapy (IMRT) plans causes higher low dose volume which increases the long-term risks of radiotherapy. We have developed Fluence Map Analyzer (FMA) program that suggests the ideal field geometry to reduce low dose volume in locally advanced breast cancer IMRT plans. In this comparative experimental study, FMA has been applied to standard IMRT plans (STD-IMRT) of randomly selected 15 left and 15 right-sided locally advanced breast cancer patients. All patients underwent a modified radical mastectomy. The chest wall, IMN, axillary, and supraclavicular lymph nodes are included in planning target volume (PTV). The heart, lungs, contralateral breast, and medulla spinalis were delineated as organs at risk (OARs). Two sets of plans, namely STD-IMRT and FMA-IMRT, were generated for each patient. The dosimetric analysis was performed using dose-volume histogram (DVH) and standard evaluation parameters of PTV and OARs. No differences could be observed among the two techniques for PTV coverage. However, FMA-IMRT plans achieved significantly lower V5 volumes and mean doses of the heart, lungs, contralateral breast, and body contours. FMA-IMRT used a smaller number of sub-fields and fewer monitor units (MU). FMA automizes the field geometry determination process for locally advanced breast cancer IMRT planning while reducing low dose volume significantly.
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