A GE multileaf collimator (MLC) has been recently installed on a Saturne 43 and is used with 6, 18 and 25 MV photon beams. In the integrated GE MLC the lower pair of jaws in the X direction is replaced by 32 pairs of computer controlled opposed tungsten leaves. The influence of each set of leaves on the output ratio is smaller than the influence of the jaws it replaces (8% instead of 10%). For irregular fields it is necessary to evaluate the influence on the output ratio of each independent leaf. It is assumed that each leaf and each jaw have an independent influence on the output ratio. According to this assumption leaf correction functions are derived from measurements as a function of their X position. A second-order correction (less than 1%) has to be applied for the jaw positions. The output ratio in a mini-phantom for a given irregular field can be calculated by the product of the 64 leaf and two jaw correction factors. The formalism is applied to symmetric square and rectangular fields, asymmetric and irregular fields. For all fields checked, the calculated and the measured output ratios agree within 1%. Furthermore the simple formula suggested by Vadash and Bjărngard for square field sizes equivalent to rectangular fields can be used with a good accuracy with an A value of 1.6 for the three energies used. The proposed formalism to calculate the output ratio in a mini-phantom is restricted to fields including the collimator axis with a minimum distance of 2 cm between any leaf and the collimator axis.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1088/0031-9155/42/3/006 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Probing spin effects in phycocyanin using Janus-like ferromagnetic microparticles.
Phys Chem Chem Phys
January 2025
Department of Applied Physics, Hebrew University, Jerusalem, Israel.
In an era of interdisciplinary scientific research, new methodologies are necessary to simultaneously advance several fields of study. One such case involves the measurement of electron spin effects on biological systems. While magnetic effects are well known in biology, recent years have shown a surge in published evidence isolating the dependence on spin, rather than magnetic field, in biological contexts.
View Article and Find Full Text PDFClinical Outcomes with High- versus Low-Dose Tranexamic Acid Infusion in Patients Undergoing Cardiac Surgery: A Systematic Review and Meta-Analysis.
Thorac Cardiovasc Surg
January 2025
Department of Medicine, MedStar Health, Baltimore, Maryland, United States.
Objectives: Antifibrinolytics, such as tranexamic acid (TXA), are widely used in cardiac surgery to reduce bleeding risks; however, the optimal dosage for TXA infusion remains a subject of debate. Hence, this study aims to evaluate the safety and efficacy of high-dose compared with low-dose TXA infusion in cardiac surgery patients.
Methods: PubMed, SCOPUS, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched until June 10, 2023, for studies assessing efficacy outcomes (e.
Pulse power supply based on Marx-pulse transformer hybrid architecture with MOSFET-resistor-diode magnetic reset control method for dielectric barrier discharge application.
Rev Sci Instrum
January 2025
College of Electrical Engineering and Control Science, Nanjing Tech University, Nanjing 211816, Jiangsu, China.
Nanosecond pulse power has many driving advantages in the dielectric barrier discharge (DBD) application field, including better discharge effect, higher discharge efficiency, and lower electrode temperature. A high-voltage pulse voltage power supply (HV-PVPS) with a multi-turn ratio linear pulse transformer (PT) based on Marx circuit and PT topologies are suitable for most DBD plasma applications with fewer expansion modules, lower cost, smaller volume, and higher reliability comparing with the all-solid-state Marx nanosecond pulse power supply. However, during the process of DBD driven by an HV-PVPS based on Marx and PT topologies, the PT is prone to magnetic core saturation, which limits the application for DBD.
View Article and Find Full Text PDFThe safety of cyclosporine and tacrolimus in pediatric nephrotic syndrome patients: a disproportionate analysis based on the FAERS database.
Front Pediatr
January 2025
Department of Urology, The Affiliated Children's Hospital of Xiangya School of Medicine, Central South University (Hunan Children's Hospital), Changsha, China.
Objective: This study aimed to systematically evaluate the safety of cyclosporine (CsA) and tacrolimus (TAC) in pediatric nephrotic syndrome (NS) patients using real-world data from the FDA Adverse Event Reporting System (FAERS).
Methods: We analyzed adverse event (AE) reports from the FAERS database between Q4 2003 and Q2 2024, focusing on AEs associated with CsA and TAC in NS patients aged 18 years and younger. We employed three signal detection methods-Proportional Reporting Ratio (PRR), Relative Reporting Ratio (RRR), and Reporting Odds Ratio (ROR)-to assess the risk of drug-related AEs.
Detection of cervical precancerous lesions and cancer by small-scale RT-qPCR analysis of oppositely deregulated mRNAs pairs in cytological smears.
Front Oncol
January 2025
AO Vector-Best, Novosibirsk, Russia.
Background: Cervical screening, aimed at detecting precancerous lesions and preventing cancer, is based on cytology and HPV testing. Both methods have limitations, the main ones being the variable diagnostic sensitivity of cytology and the moderate specificity of HPV testing. Various molecular biomarkers are proposed in recent years to improve cervical cancer management, including a number of mRNAs encoded by human genes involved in carcinogenesis.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!