PMID: 9194128Jun 1, 1997Paper

What is the explanation for the changes to cobalt-60 tissue-air ratios in BJR Supplement 25?

Physics in Medicine and Biology
A L McKenzie

Abstract

Values of tissue-air ratio (TAR) in the recent British Journal of Radiology (BJR) Supplement 25 have been increased by nearly 2% over the values which have been accepted for the past 30 years. The need for this was shown by analysis of previous data using scaling laws, together with Monte Carlo calculations and careful re-measurement. However, it was not clear why previous determinations of TAR were in error: it was not, as some workers argued, because scattered radiation had been included in the absorbed dose in the miniphantom, because TAR data in BJR Supplement 17 had been derived from peak scatter factor (PSF), which is not based on the miniphantom concept. The purpose of this paper is to find the real explanation of why the PSF and, therefore, TAR were underestimated for so long. Two definitions of PSF are considered: one based on kerma and one based on dose. This paper relates PSF of either definition to measurements of air kerma by including in the derivation the scatter in the plug which replaces the chamber when it has been removed from the surface of the water phantom. The kerma-based PSF is found to be 2% higher than the simple ratio of chamber readings in phantom and in air. The value of the dose-based definition ag...Continue Reading

References

Mar 1, 1979·Health Physics·F H Attix
Jul 1, 1992·Physics in Medicine and Biology·A L McKenzie
Jan 1, 1988·Physics in Medicine and Biology·B E Bjärngard, P L Petti
Jan 1, 1974·Physics in Medicine and Biology·W H Henry
Jan 1, 1966·The British Journal of Radiology·S K Gupta, J R Cunningham
Jan 1, 1982·Physics in Medicine and Biology·W H Henry
May 1, 1981·Physics in Medicine and Biology·P M Pfalzner
Jan 1, 1995·Physics in Medicine and Biology·A L McKenzie, P H Stevens
Jul 1, 1996·Medical Physics·P S NizinR B Mooij
Aug 1, 1965·The British Journal of Radiology·J R CUNNINGHAMS K GUPTA

❮ 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.