PMID: 9434299Jan 22, 1998Paper

Blocked field effects on collimator scatter factors

Physics in Medicine and Biology
P D HigginsA S Ahuja

Abstract

In routine dosimetry we assume separability of the collimator (Sc) and phantom (Sp) scatter components that together comprise the total scatter factor (Sc,p). In practice, the addition of blocking also affects the photon fluence attributable to the treatment head and flattening filter in a complicated way. The reduced aperture blocks out some of the head scatter contribution, while the block and tray add back secondary scatter. In the following we present techniques for directly measuring the aperture effect on Sc in air or in a full-scatter phantom. The change in Sc is found to be a scaleable quantity that can be modelled as a simple linear fit to the ratio of projected open-to-blocked equivalent square fields. Measurements have been made for 6, 18 and 24 MV photon beams on one Varian 2500 and two Varian 2100c accelerators. Results indicate a progressive loss of collimator scatter contribution with increased field blocking that is amplified with increasing energy. Block and tray scatter only contribute significantly to Sc for large fields and treatment distances of 80 cm or less. Application of these corrections in monitor unit calculations is presented.

References

Nov 1, 1992·Medical Physics·P B Dunscombe, J M Nieminen
May 1, 1992·Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology·J Van DamA Dutreix
Apr 1, 1991·Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology·J J van GasterenC F Westermann
Aug 1, 1990·The British Journal of Radiology·A R Hounsell, J M Wilkinson
Jan 1, 1988·Medical Physics·G Luxton, M A Astrahan
Mar 1, 1987·Medical Physics·G Krithivas, S N Rao
Feb 1, 1995·Medical Physics·D M FryeP Jursinic
Jun 1, 1995·Medical Physics·T C ZhuH Shackford
Sep 1, 1994·Medical Physics·E L ChaneyT A Gabriel
May 1, 1993·Medical Physics·P Vadash, B Bjärngard
Jan 1, 1993·Medical Physics·M Tatcher, B E Bjarngard
Jul 1, 1996·Medical Physics·K L Lam, R K Ten Haken

❮ Previous
Next ❯

Citations

Aug 11, 2006·Medical Physics·P D Higgins, P Alaei
Jul 17, 2010·Medical Physics·Parham Alaei, Patrick Higgins
Dec 10, 2009·Medical Physics·Timothy C ZhuUNKNOWN AAPM Therapy Physics Committee Task Group 74

❮ Previous
Next ❯

Related Concepts

Trending Feeds

COVID-19

Coronaviruses encompass a large family of viruses that cause the common cold as well as more serious diseases, such as the ongoing outbreak of coronavirus disease 2019 (COVID-19; formally known as 2019-nCoV). Coronaviruses can spread from animals to humans; symptoms include fever, cough, shortness of breath, and breathing difficulties; in more severe cases, infection can lead to death. This feed covers recent research on COVID-19.

Blastomycosis

Blastomycosis fungal infections spread through inhaling Blastomyces dermatitidis spores. Discover the latest research on blastomycosis fungal infections here.

Nuclear Pore Complex in ALS/FTD

Alterations in nucleocytoplasmic transport, controlled by the nuclear pore complex, may be involved in the pathomechanism underlying multiple neurodegenerative diseases including Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. Here is the latest research on the nuclear pore complex in ALS and FTD.

Applications of Molecular Barcoding

The concept of molecular barcoding is that each original DNA or RNA molecule is attached to a unique sequence barcode. Sequence reads having different barcodes represent different original molecules, while sequence reads having the same barcode are results of PCR duplication from one original molecule. Discover the latest research on molecular barcoding here.

Chronic Fatigue Syndrome

Chronic fatigue syndrome is a disease characterized by unexplained disabling fatigue; the pathology of which is incompletely understood. Discover the latest research on chronic fatigue syndrome here.

Evolution of Pluripotency

Pluripotency refers to the ability of a cell to develop into three primary germ cell layers of the embryo. This feed focuses on the mechanisms that underlie the evolution of pluripotency. Here is the latest research.

Position Effect Variegation

Position Effect Variagation occurs when a gene is inactivated due to its positioning near heterochromatic regions within a chromosome. Discover the latest research on Position Effect Variagation here.

STING Receptor Agonists

Stimulator of IFN genes (STING) are a group of transmembrane proteins that are involved in the induction of type I interferon that is important in the innate immune response. The stimulation of STING has been an active area of research in the treatment of cancer and infectious diseases. Here is the latest research on STING receptor agonists.

Microbicide

Microbicides are products that can be applied to vaginal or rectal mucosal surfaces with the goal of preventing, or at least significantly reducing, the transmission of sexually transmitted infections. Here is the latest research on microbicides.

© 2021 Meta ULC. All rights reserved