Abstract
This study aimed to examine the resolution effects of breast thickness and lesion
location in magnification mammography by evaluating generalized modulation transfer
function (GMTF) including the effect of focal spot, effective pixel size, and the
scatter. Polymethyl methacrylate (PMMA) thicknesses ranging from 10 to 40 mm were
placed on a standard supporting platform that was positioned to achieve magnification
factors ranging from 1.2 to 2.0.
As the magnification increased, the focal spot MTF degraded, while the detector MTF
improved. The GMTF depended on the trade-off between the focal spot size and effective
pixel size. Breast thickness and lesion location had little effect on the resolution
at high frequencies. The resolution of small focal spot did improve slightly with
increasing PMMA thickness for magnification factors less than 1.8. In contrast, system
resolution decreased with increasing PMMA thickness for magnification factors greater
than 1.8 since focal spot blur begins to dominate spatial resolution. In particular,
breast thickness had a large effect on the resolution at lower frequencies. A low-frequency
drop effect increased with increasing PMMA thickness because of the increase in scatter
fraction. Hence, the effect of compressed breast thickness should be considered for
the standard magnification factor of 1.8 that is most commonly used in clinical practice.
Our results should provide insights for determining optimum magnification in clinical
application of digital mammography, and our approaches can be extended to a wide diversity
of radiological imaging systems.
Keywords
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Article info
Publication history
Published online: December 26, 2011
Accepted:
November 10,
2011
Received in revised form:
September 18,
2011
Received:
July 29,
2011
Footnotes
☆This work was supported by the Basic Atomic Energy Research Institute of the National Research Foundation of Korea funded by the Ministry of Education, Science & Technology (grant code: 2011-0006368).
Identification
Copyright
© 2012 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
