ABSTRACT
Background: The dose-related effects of patient setup errors on bio-physical indices were evaluated for the conventional wedge [CW] and field-in-field [FIF] whole breast irradiation techniques [WBI]
Materials and Methods: The treatment plans of 10 patients receiving left WBI were retrospectively selected for evaluation. The bio-physical effects of dose variations were evaluated by shifting the isocenters and gantry-angles of the treatment plans. Dose-volume histograms of the planning target volume [PTV], heart, and lungs were generated, and the conformity index [Cl], homogeneity index [HI], tumor control probability [TCP], and normal tissue complication probability [NTCP] were determined
Results: The D95 of the PTV for an [isocenter shift plan] with a posterior direction decreased by approximately 15%, and the TCP of the PTV decreased by approximately 50% for the FIF technique and by 40% for the CW; however, the NTCPs of the lungs and heart increased for both techniques. Increasing the gantry-angle decreased the TCPs of the PTV by 24.4% [CW] and by 34% [FIF]. The NTCPs of the lungs and heart for the two techniques differed by only 3%. The CIs and His for the CW case were higher than the corresponding values obtained for the FIF case. Significant differences were observed between the two techniques [p<0.01]
Conclusion: Our results revealed that the biophysical properties of the FIF case were more sensitive to setup errors than those in the CW case. The radiobiological-based analysis could be detected significant dosimetric errors and provided a practical patient quality assurance method for guiding the bio-physical effects?
ABSTRACT
This study proposed a new discharge estimation method using a mean velocity formula derived from Chiu's 2D velocity formula of probabilistic entropy concept and the river bed shear stress of channel. In particular, we could calculate the mean velocity, which is hardly measurable in flooding natural rivers, in consideration of several factors reflecting basic hydraulic characteristics such as river bed slope, wetted perimeter, width, and water level that are easily obtainable from rivers. In order to test the proposed method, we used highly reliable flow rate data measured in the field and published in SCI theses, estimated entropy M from the results of the mean velocity formula and, at the same time, calculated the maximum velocity In particular, we obtained [phi][M] expressing the overall equilibrium state of river through regression analysis between the maximum velocity and the mean velocity, and estimated the flow rate from the newly proposed mean velocity formula. The relation between estimated and measured discharge was analyzed through the discrepancy ratio, and the result showed that the estimate value was quite close to the measured data