Affiliations: [a] Center for Bioengineering and School of Electrical and Computer Engineering, University of Oklahoma, Norman, OK, USA | [b] Department of Radiology, University of Alabama at Birmingham, Birmingham, AL, USA
Correspondence:
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Corresponding author: Xizeng Wu, Department of Radiology, University of Alabama at Birmingham, Birmingham, AL 35249, USA. E-mail:[email protected]
Abstract: The objective of this study was to investigate the optimization of a high energy in-line phase sensitive x-ray imaging prototype under different geometric and operating conditions for mammography application. A phase retrieval algorithm based on phase attenuation duality (PAD) was applied to the phase contrast images acquired by the prototype. Imaging performance
was investigated at four magnification values of 1.67, 2, 2.5 and 3 using an
acrylic edge, an American College of Radiology (ACR) mammography phantom and
contrast detail (CD) phantom with tube potentials of 100, 120 and 140 kVp.
The ACR and CD images were acquired at the same mean glandular dose (MGD) of
1.29 mGy with a computed radiography (CR) detector of 43.75 μm pixel
pitch at a fixed source to image distance (SID) of 170 cm. The x-ray tube
focal spot size was kept constant as 7 μm while a 2.5 mm thick aluminum
(Al) filter was used for beam hardening. The performance of phase contrast
and phase retrieved images were compared with computer simulations based on
the relative phase contrast factor (RPF) at high x-ray energies. The imaging
results showed that the x-ray tube operated at 100 kVp under the
magnification of 2.5 exhibits superior imaging performance which is in
accordance to the computer simulations. As compared to the phase contrast
images, the phase retrieved images of the ACR and CD phantoms demonstrated
improved imaging contrast and target discrimination. We compared the CD
phantom images acquired in conventional contact mode with and without the
anti-scatter grid using the same prototype at 1.295 mGy and 2.59 mGy using
40 kVp, a 25 μm rhodium (Rh) filter. At the same radiation dose, the
phase sensitive images provided improved detection capabilities for both the
large and small discs, while compared to the double dose image acquired in
conventional mode, the observer study also indicated that the phase
sensitive images provided improved detection capabilities for the large
discs. This study therefore validates the potential of using high energy
phase contrast x-ray imaging to improve lesion detection and reduce
radiation dose for clinical applications such as mammography.
