14 research outputs found
Impact of Dose Calculation Algorithms and Radiobiological Parameters on Prediction of Cardiopulmonary Complications in Left Breast Radiation Therapy
Background: Breast cancer requires evaluating treatment plans using dosimetric and biological parameters. Considering radiation dose distribution and tissue response, healthcare professionals can optimize treatment plans for better outcomes.
Objective: This study aimed to evaluate the effects of the different Dose Calculation Algorithms (DCAs) and Biologically Model-Related Parameters (BMRPs) on the prediction of cardiopulmonary complications due to left breast radiotherapy.
Material and Methods: In this practical study, the treatment plans of 21 female patients were simulated in the Monaco Treatment Planning System (TPS) with a prescribed dose of 50 Gy in 25 fractions. Dose distribution was extracted using the three DCAs [Pencil Beam (PB), Collapsed Cone (CC), and Monte Carlo (MC)]. Cardiopulmonary complications were predicted by Normal Tissue Complication Probability (NTCP) calculations using different dosimetric and biological parameters. The Lyman-Kutcher-Burman (LKB) and Relative-Seriality (RS) models were used to calculate NTCP. The endpoint for NTCP calculation was pneumonitis, pericarditis, and late cardiac mortality. The ANOVA test was used for statistical analysis.
Results: In calculating Tumor Control Probability (TCP), a statistically significant difference was observed between the results of DCAs in the Poisson model. The PB algorithm estimated NTCP as less than others for all Pneumonia BMRPs.
Conclusion: The impact of DCAs and BMRPs differs in the estimation of TCP and NTCP. DCAs have a stronger influence on TCP calculation, providing more effective results. On the other hand, BMRPs are more effective in estimating NTCP. Consequently, parameters for radiobiological indices should be cautiously used s to ensure the appropriate consideration of both DCAs and BMRPs
On Prediction of Cardio-Pulmonary Complications during Hypofractionated versus Conventional Fractionated Regimens of Left Breast Radiation Therapy Using Monte Carlo and Collapsed Cone Convolution Based Algorithms
Introduction: Due to the challenge of choosing the optimal treatment regimen as well as the accurate dose calculation algorithm (DCA), this study aimed to evaluate the DCAs to compare the conventional fractionation radiotherapy (CFRT) and hypofractionation radiotherapy (HFRT) of breast cancer (BC) in the prediction of cardio-pulmonary complications.
Material and Methods: For 19 patients with left-sided BC, treatment regimens, CFRT (50Gy/25frs) vs. HFRT (42.5Gy/16frs), were simulated. Normal tissue complication probability (NTCP) and tumor control probability (TCP) values for each regimen using radiobiological models were calculated via Monte Carlo (MC) and Collapsed Cone Convolution (CCC) algorithms. For statistical comparison of the results obtained from the regimens and algorithms, the t-test and Wilcoxon test were used in SPSS Statistics. Statistical significance was defined as p<0.05.
Results: The mean NTCP and TCP calculated in CFRT and HFRT were as follows: cardiac mortality (MC: CFRT=0.0374±0.0134 vs. HFRT=0.0173±0.0066; p<0.001) and (CCC: CFRT=0.0373±0.0134 vs. HFRT=0.0168±0.0064; p<0.001), pneumonitis (MC: CFRT=0.1201±0.0322 vs. HFRT=0.0756±0.0221; p<0.001) and (CCC: CFRT=0.1131±0.0310 vs. HFRT=0.0697±0.0120; p<0.010), and TCP (MC: CFRT=0.9979±0.0087 vs. HFRT=0.9997±0.0092; p=0.593) and (CCC: CFRT=0.9982±0.0029 vs. HFRT=0.9986±0.0016; p=0.821).
Conclusion: The comparison of CFRT and HFRT using MC and CCC algorithms showed that the risk of cardiac mortality and pneumonitis in CFRT was significantly higher than in HFRT, and TCP was not significantly different in the two regimens. Applications of MC-based DCAs along with suitable biological parameters can help physicists in the prediction of radiation-induced complications accurately and precisely
Patient dose from radiographic rejects/repeats in radiology centers of Urmia University of Medical Sciences, Iran
Collapsed cone superposition algorithm validation for chest wall tangential fields using virtual wedge filters
Background: Virtual wedge (VW) is used in radiotherapy to compensate for missing tissues and create a uniform dose distribution in tissues. According to TECDOC-1583 and technical reports series no. 430, evaluating the dose calculation accuracy is essential for the quality assurance of treatment planning systems (TPSs). In this study, the dose calculation accuracy of the collapsed cone superposition (CCS) algorithm in the postmastectomy radiotherapy of the chest wall for breast cancer was evaluated by comparing the calculated and measured dose in VW fields. Methods: Two tangential fields with the typical VW angles were planned using ISOgray TPS in a thorax phantom. The CCS algorithm was used for dose calculation at 6 and 15 MV photon beams. The obtained dose distributions from EBT3 film spaces and TPS were evaluated using the gamma index. Results: The measured and calculated dose values using VW in a heterogeneous medium with different beam energies were in a good agreement with each other (acceptance rate: 88.0%–93.4%). The calculated and measured data did not differ significantly with an increase/decrease in wedge angle. In addition, the results demonstrated that ISOgray overestimated and underestimated the dose of the soft tissue and lung in the planned volume, respectively. Conclusions: According to the results of gamma index analysis, the calculated dose distribution using VW model with the CCS algorithm in a heterogeneous environment was within acceptable limits
On prediction of the strength levels and failure patterns of human vertebrae using quantitative computed tomography (QCT)-based finite element method
Noninvasive Prediction of Vertebral Body Compressive Strength Using Finite Element Method and An Image Based Technique
peer reviewe
Prediction of Human Vertebral Compressive Strength Using Quantitative Computed Tomography Based Nonlinear Finite Element Method
Introduction: Because of the importance of vertebral compressive fracture (VCF) role in increasing the patients’ death rate and reducing their quality of life, many studies have been conducted for a noninvasive prediction of vertebral compressive strength based on bone mineral density (BMD) determination and recently finite element analysis. In this study, QCT-voxel based nonlinear finite element method is used for predicting vertebral compressive strength. Material and Methods: Four thoracolumbar vertebrae were excised from 3 cadavers with an average age of 42 years. They were then put in a water phantom and were scanned using the QCT. Using a computer program prepared in MATLAB, detailed voxel based geometry and mechanical characteristics of the vertebra were extracted from the CT images. The three dimensional finite element models of the samples were created using ANSYS computer program. The compressive strength of each vertebra body was calculated based on a linearly elastic-linearly plastic model and large deformation analysis in ANSYS and was compared to the value measured experimentally for that sample. Results: Based on the obtained results the QCT-voxel based nonlinear finite element method (FEM) can predict vertebral compressive strength more effectively and accurately than the common QCT-voxel based linear FEM. The difference between the predicted strength values using this method and the measured ones was less than 1 kN for all the samples. Discussion and Conclusion: It seems that the QCT-voxel based nonlinear FEM used in this study can predict more effectively and accurately the vertebral strengths based on every vertebrae specification by considering their detailed geometric and densitometric characteristics
Prediction of Human Vertebral Compressive Strength Using Quantitative Computed Tomography Based Nonlinear Finite Element Method
Introduction: Because of the importance of vertebral compressive fracture (VCF) role in increasing the patients’ death rate and reducing their quality of life, many studies have been conducted for a noninvasive prediction of vertebral compressive strength based on bone mineral density (BMD) determination and recently finite element analysis. In this study, QCT-voxel based nonlinear finite element method is used for predicting vertebral compressive strength. Material and Methods: Four thoracolumbar vertebrae were excised from 3 cadavers with an average age of 42 years. They were then put in a water phantom and were scanned using the QCT. Using a computer program prepared in MATLAB, detailed voxel based geometry and mechanical characteristics of the vertebra were extracted from the CT images. The three dimensional finite element models of the samples were created using ANSYS computer program. The compressive strength of each vertebra body was calculated based on a linearly elastic-linearly plastic model and large deformation analysis in ANSYS and was compared to the value measured experimentally for that sample. Results: Based on the obtained results the QCT-voxel based nonlinear finite element method (FEM) can predict vertebral compressive strength more effectively and accurately than the common QCT-voxel based linear FEM. The difference between the predicted strength values using this method and the measured ones was less than 1 kN for all the samples. Discussion and Conclusion: It seems that the QCT-voxel based nonlinear FEM used in this study can predict more effectively and accurately the vertebral strengths based on every vertebrae specification by considering their detailed geometric and densitometric characteristics
An Investigation of Mean Glandular Dose from Routine Mammography in Urmia, Northwestern Iran and the Factors Affecting It
Abstract: The objective of this study was to determine the Mean Glandular Dose (MGD) resulting from Craniocaudal (CC) and Mediolateral oblique (MLO) views in one breast and the total dose per woman in Urmia, northwestern Iran and to identify the factors affecting it. This study was conducted during 9 months to estimate the MGD for women undergoing mammography and to report the distribution of dose. The clinical data were collected from 460 mammograms taken from 230 women who were referred to radiology center of Imam Reza hospital in Urmia. The piranha system version 3.8A was used for determining the MGD in this work. The MGD values are based on measurements of ESAK (entrance surface air krema) and HVL. Significant differences were found between MGD from CC and MLO views. The mean±SD MGD per film was 1.18±0.38 mGy for craniocaudal and 1.39±0.51 mGy for mediolateral oblique views, (p<0.001). The mean±SD MGD per woman was 2.57±0.44 mGy. The mean± SD MGD per film in present study were lower than most of similar reports. The dose values obtained fall within the internationally acceptable dose range of 1-3mGy. This suggests mammography x-ray generators in this part of the country are capable of achieving acceptable dose levels for patient safety. Therefore, with considering the all other factors, the establishment of screening mammography program is achievable
Validation of a prototype optical computed tomography system
In radiation cancer treatments, the most of the side effects could be minimized using a proper dosimeter. Gel dosimeter is the only three-dimensional dosimeter and magnetic resonance imaging (MRI) is the gold standard method for gel dosimeter readout. Because of hard accessibility and high cost of sample reading by MRI systems, some other alternative methods were developed. The optical computed tomography (OCT) method could be considered as the most promising alternative method that has been studied widely. In the current study, gel dosimeter scanning using a prototype optical scanner and validation of this optical scanner was performed. Optical absorbance of the irradiated gel samples was determined by both of conventional spectrophotometer and the fabricated OCT system at 632 nm. Furthermore, these irradiated vials were scanned by a 1.5 T MRI. The slope of the curves was extracted as the dose-response sensitivity. The R2-dose sensitivity measured by MRI method was 0.1904 and 0.113 for NIPAM and PAGAT gels, respectively. The optical dose sensitivity obtained by conventional spectrophotometer and the fabricated optical scanner was 0.0453 and 0.0442 for NIPAM gels and 0.0244 and 0.0242 for PAGAT gels, respectively. The scanning results of the absorbed dose values showed that the new OCT and conventional spectrophotometer were in fair agreement. From the results, it could be concluded that the fabricated system is able to quantize the absorbed dose values in polymer gel samples with acceptable accuracy