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Report of AAPM Therapy Physics Committee Task Group 74: In-air output ratio, Sc, for megavoltage photon beams

Overview of attention for article published in Medical Physics, October 2009
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Title
Report of AAPM Therapy Physics Committee Task Group 74: In-air output ratio, Sc, for megavoltage photon beams
Published in
Medical Physics, October 2009
DOI 10.1118/1.3227367
Pubmed ID
Authors

Timothy C. Zhu, Anders Ahnesjö, Kwok Leung Lam, X. Allen Li, Chang-Ming Charlie Ma, Jatinder R. Palta, Michael B. Sharpe, Bruce Thomadsen, Ramesh C. Tailor

Abstract

The concept of in-air output ratio (Sc) was introduced to characterize how the incident photon fluence per monitor unit (or unit time for a Co-60 unit) varies with collimator settings. However, there has been much confusion regarding the measurement technique to be used that has prevented the accurate and consistent determination of Sc. The main thrust of the report is to devise a theoretical and measurement formalism that ensures interinstitutional consistency of Sc. The in-air output ratio, Sc, is defined as the ratio of primary collision water kerma in free-space, Kp, per monitor unit between an arbitrary collimator setting and the reference collimator setting at the same location. Miniphantoms with sufficient lateral and longitudinal thicknesses to eliminate electron contamination and maintain transient electron equilibrium are recommended for the measurement of Sc. The authors present a correction formalism to extrapolate the correct Sc from the measured values using high-Z miniphantom. Miniphantoms made of high-Z material are used to measure Sc for small fields (e.g., IMRT or stereotactic radiosurgery). This report presents a review of the components of Sc, including headscatter, source-obscuring, and monitor-backscattering effects. A review of calculation methods (Monte Carlo and empirical) used to calculate Sc for arbitrary shaped fields is presented. The authors discussed the use of Sc in photon dose calculation algorithms, in particular, monitor unit calculation. Finally, a summary of Sc data (from RPC and other institutions) is included for QA purposes.

Mendeley readers

The data shown below were compiled from readership statistics for 218 Mendeley readers of this research output. Click here to see the associated Mendeley record.

Geographical breakdown

Country Count As %
Spain 4 2%
Canada 2 <1%
United States 2 <1%
Japan 2 <1%
Iran, Islamic Republic of 1 <1%
India 1 <1%
United Kingdom 1 <1%
Unknown 205 94%

Demographic breakdown

Readers by professional status Count As %
Student > Ph. D. Student 42 19%
Other 39 18%
Researcher 37 17%
Student > Master 30 14%
Student > Postgraduate 11 5%
Other 36 17%
Unknown 23 11%
Readers by discipline Count As %
Physics and Astronomy 120 55%
Medicine and Dentistry 49 22%
Engineering 8 4%
Agricultural and Biological Sciences 3 1%
Computer Science 2 <1%
Other 7 3%
Unknown 29 13%

Attention Score in Context

This research output has an Altmetric Attention Score of 3. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 06 October 2022.
All research outputs
#7,318,956
of 22,408,829 outputs
Outputs from Medical Physics
#1,948
of 7,603 outputs
Outputs of similar age
#30,959
of 84,323 outputs
Outputs of similar age from Medical Physics
#17
of 42 outputs
Altmetric has tracked 22,408,829 research outputs across all sources so far. This one is in the 44th percentile – i.e., 44% of other outputs scored the same or lower than it.
So far Altmetric has tracked 7,603 research outputs from this source. They receive a mean Attention Score of 3.4. This one is in the 47th percentile – i.e., 47% of its peers scored the same or lower than it.
Older research outputs will score higher simply because they've had more time to accumulate mentions. To account for age we can compare this Altmetric Attention Score to the 84,323 tracked outputs that were published within six weeks on either side of this one in any source. This one is in the 21st percentile – i.e., 21% of its contemporaries scored the same or lower than it.
We're also able to compare this research output to 42 others from the same source and published within six weeks on either side of this one. This one is in the 4th percentile – i.e., 4% of its contemporaries scored the same or lower than it.