Dosimetric impact of different multileaf collimators on cardiac and left anterior descending coronary artery dose reduction.

Introduction: Radiotherapy (RT) may increase the dose of heart structure like left anterior descending coronary artery (LAD). The purpose of this paper was to evaluate the impact of various multileaf collimators (MLCs) in shielding organ at risks (OARs), especially LAD, of patients with left breast cancer. Materials and Methods: Forty-five patients with left breast cancer were selected. The treatment plans were created applying three techniques for all patients. In the first plan (uncovered LAD), the treatment plan was made without considering LAD as OARs. In the two other plans, two MLCs with different leaf widths (6.8 mm and 5 mm) were used to shield the LAD. For all plans, MLC was shielded as much of OAR as possible without compromising planning target volume (PTV) coverage. Dosimetric parameters of the heart, LAD, and ipsilateral lung were assessed. Results: Compared to other plans, the covered LAD plan 1(CL1) obtained lower lung, cardiac, and LAD doses with the same PTV coverage. On average, the mean heart dose decreased from 6.2 Gy to 5.4 Gy by CL1, and the average mean dose to the LAD was reduced from 36.4 Gy to 33.7 Gy, which was statistically significant. The average lung volume receiving >20 Gy was significantly reduced from 24.6% to 23.4%. Moreover, the results show that covered LAD plan 2(CL2) is less useful for shielding OARs compared to CL1. Conclusion: CL1 plans may reduce OAR dose for patients without compromising the target coverage. Hence, the proper implementation of MLC can decrease the side effects of RT.

The Efficacy of Multi-Leaf Collimator in the Reduction of Cardiac and Coronary Artery Dose in Left-Sided Breast Cancer Radiotherapy.

Background: Multi-leaf collimator (MLC) is one of the efficient and cost-effective methods for protecting sensitive tissues around the target. This study aimed to evaluate the protective effect of MLC on the protection of sensitive organs in patients with left breast cancer. Materials and Methods: This study was performed on computed tomography (CT) scans of 45 patients with left breast cancer. Two treatment plans were completed for each patient. Only the heart and left lung were considered organs at risk in the first treatment plan, and in the second treatment plan, the left anterior descending artery (LAD) was also considered the organ at risk. It was covered as much as possible by the MLC. Dosimetric results of tumor and organ at risk (OARs) were extracted from the dose-volume histogram and compared. Results: The results showed that more LAD coverage by MLC leads to a significant reduction in the mean dose of OARs (P-value <0.05). The mean dose for heart, LAD, and left lung decreased by 11%, 7.4%, and 4.9%, respectively. The values of V5 (volume received the dose of 5 Gy) and V20 for the lung, V10, V25, and V30 for LAD, and V5, V20, V25, and V30 for the heart also decreased significantly (P-value <0.05). Conclusions: In general, better protection of LAD, heart, and lungs can be achieved by maximal shielding organs at risk by MLC in radiation therapy for patients with left breast cancer.

The Design and Optimization of Extractive Distillation for Separating the Acetone/n-Heptane Binary Azeotrope Mixture.

Acetone and n-heptane are common solvents in the pharmaceutical industry and they have been found in wastewater. Under atmospheric conditions, the mixture of these compounds creates a minimum-boiling azeotrope. The extractive distillation process with a high boiling solvent is commonly utilized to separate the azeotropes in the industry to minimize waste, reuse resources, achieve clean production, and preserve the environment. In this work, extractive distillation was applied to separate the binary azeotropic system of acetone and n-heptane in wastewater using butyl propionate as a solvent. The characteristics of the process are designed and simulated via Aspen Plus. The simulation results showed that to get a distillate containing at least 99.5 mass% acetone, a solvent-to-feed ratio of 1.4, a reflux ratio of 1.5, a number of stages of 30, a feed stage of 26, a solvent stage of 10, and a solvent temperature of 298.15 K were required. The optimum operating parameters of the process were also obtained using the NLP optimization method, with the minimum total annual cost as the objective function. While the process was operating in optimal mode, CO2 emissions were calculated to be 0.0780 kg CO2/kg feed.

Efficient Production of Light Olefin Based on Methanol Dehydration: Simulation and Design Improvement.

BACKGROUND: Ethylene, propylene, and butylene as light olefins are the most important intermediates in the petrochemical industry worldwide. Methanol to olefins (MTO) process is a new technology based on catalytic cracking to produce ethylene and propylene from methanol. AIMS AND OBJECTIVE: This study aims to simulate the process of producing ethylene from methanol by using Aspen HYSYS software from the initial design to the improved design. METHODS: Ethylene is produced in a two-step reaction. In an equilibrium reactor, the methanol is converted to dimethyl ether by an equilibrium reaction. The conversion of the produced dimethyl ether to ethylene is done in a conversion reactor. Changes have been made to improve the conditions and get closer to the actual process design carried out in the industry. The plug flow reactor has been replaced by the equilibrium reactor, and the distillation column was employed to separate the dimethyl ether produced from the reactor. RESULT: The effect of the various parameters on the ethylene production was investigated. Eventually, ethylene is produced with a purity of 95.5 % in the improved design, and thermal integration was performed to minimize energy consumption. CONCLUSION: It was finally found according to the exothermic reaction of the dimethyl ether production, thermal integration in the process reduces the energy consumption in the heater and cooler.

Touch imprint and crash preparation intra operative cytology versus frozen section in thyroid nodule.

BACKGROUND: Intra operative cytology (IC), including touch imprint (TI) and crash preparations (CP), in general has been demonstrated to be a diagnostic tool for many organs but its validity and reliability for diagnosis of thyroid nodules remain controversial. We evaluate the diagnostic value of frozen section, touch imprint, crash preparation and the combination of touch imprint and crash preparation and the combination of frozen section, touch imprint and crash preparation. MATERIALS AND METHODS: [corrected] 55 intra operative specimens from patients with thyroid nodules who underwent thyroidectomy were evaluated at Alzahra and vali-Asr hospital laboratories. For all of the patients frozen section (FS), touch imprint (TI) and crash preparation (CP) was obtained and reviewed by two pathologists at the same time. Serial TI and CP, and FS, TI and CP were reviewed by the same pathologists. Sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio and accuracy were calculated according to the permanent section as the gold standard test. RESULTS: In our study sensitivity, specificity and accuracy for FS was 100%, 97.6% and 98.1% respectively; for TI they were 78.6%, 95% and 92.4%; for CP they were 78.6%, 92.7% and 89.9%; for serial TI and CP they were 85.7%, 92.7% and 90.9%; and for the combination of FS and TI and CP they were 100%, 97.6% and 98.18% respectively. CONCLUSIONS: Intra operative cytology (including TI and CP) seems to be a useful, valuable and inexpensive method in clinics, which do not have equipment for frozen sections. Intra operative cytology combined with FS increased the overall accuracy of diagnosis. Further studies are needed to validate the obtained results of this study.

High dose Senna or Poly Ethylene Glycol (PEG) for elective colonoscopy preparation: a prospective randomized investigator-blinded clinical trial.

BACKGROUND: The aim of this study was to determine the efficacy of two methods of colon preparation for colon cleansing in a randomized controlled trial. METHODS: In this prospective randomized investigator-blinded trial, consecutive outpatients indicated for elective colonoscopy were randomized into two groups. Patients in Senna group took 24 tablets of 11 mg Senna in two divided doses 24 hour before colonoscopy. In Poly Ethylene Glycol (PEG) group they solved 4 sachets in 4 liters of water the day before the procedure and were asked to drink 250 ml every 15 minutes. The overall quality of colon cleansing was evaluated using the Aronchick scoring scale. Difficulty of the procedure, patients' tolerance and compliance and adverse events were also evaluated. RESULTS: 322 patients were enrolled in the study. There was no significant difference in the quality of colon cleansing, patients' tolerance, compliance and the difficulty of the procedure between two groups (p > 0.05). The incidence of adverse effects was similar between two groups except for abdominal pain that was more severe in Senna group (p < 0.05) and nausea and vomiting that was more common in PEG group (p < 0.05) CONCLUSIONS: In conclusion we deduce that Senna has the same efficacy and patient's acceptance as Polyethylene glycol-electrolyte solution (PEG-ES) and it could be prescribed as an alternative method for bowel preparation.