Phantom Design for Phase Contrast Breast Imaging
S Vedantham*, A Karellas, University of Massachusetts Medical School, Worcester, MASU-E-I-61 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall
Purpose: Phase contrast breast imaging has the potential to improve visualization of anatomic structures. While the physics is well-understood, there are several choices for implementation. In order to evaluate these choices, it is essential to design a phantom for phase contrast imaging with appropriate breast-equivalent materials.
Methods: Phantoms for mammography use materials that mimic the x-ray attenuation properties of breast tissue. Hence, the refractive index decrement (delta) was determined for breast tissues of varying glandular fraction [Hammerstein, Radiology 130(2):485-91, 1979] for the energy range (5-100 KeV) relevant to mammography and breast CT using XOP software (Version 2.3, ESRF, France) and compared to that of commonly used phantom materials. Delta for 50% and 70% glandular breast-equivalent material (CIRS Inc., Norfolk, VA), solid water, BR-12, polymethyl methacrylate (PMMA), beeswax (C46H92O2, density: 0.97 g/cm³) and paraffin wax (C25H52, density: 0.95 g/cm³) were determined. Microcalcifications in vivo are either of oxalate or phosphate composition. Delta of calcium oxalate monohydrate (COM) and calcium hydroxyapatite (CH) were determined and compared with that of calcium carbonate, gold and aluminum.
Results: In terms of delta, paraffin wax (4% higher) and beeswax (4% higher) best simulated 50% and 100% glandular breast, respectively. Delta of other commonly used phantom materials such as 50% and 70% glandular breast-equivalent material, solid water, and BR-12 were two orders of magnitude higher, and that of PMMA was 28% higher, than 50% glandular breast tissue. For microcalcifications, delta of gold was 4.6 to 6.5 times higher than that of COM and CH, respectively. Delta of aluminum and calcium carbonate were found to straddle that of COM and CH.
Conclusions: For phase contrast imaging, a phantom comprising paraffin wax to simulate 50% glandular background tissue, beeswax to simulate a mass equivalent to 100% glandular tissue, and calcium carbonate or aluminum to simulate microcalcifications is appropriate.