KEYWORDS: Iodine, Breast, Digital breast tomosynthesis, Sensors, Mammography, Dual energy imaging, Tumors, Lead, Data acquisition, Reconstruction algorithms
Dual-Energy Contrast Enhanced Digital Breast Tomosynthesis (DE-CE-DBT) has the potential to deliver diagnostic
information for vascularized breast pathology beyond that available from screening DBT. DE-CE-DBT involves a
contrast (iodine) injection followed by a low energy (LE) and a high energy (HE) acquisitions. These undergo weighted
subtraction then a reconstruction that ideally shows only the iodinated signal. Scatter in the projection data leads to
“cupping” artifacts that can reduce the visibility and quantitative accuracy of the iodinated signal. The use of filtered
backprojection (FBP) reconstruction ameliorates these types of artifacts, but the use of FBP precludes the advantages of
iterative reconstructions. This motivates an effective and clinically practical scatter correction (SC) method for the
projection data. We propose a simple SC method, applied at each acquisition angle. It uses scatter-only data at the edge
of the image to interpolate a scatter estimate within the breast region. The interpolation has an approximately correct
spatial profile but is quantitatively inaccurate. We further correct the interpolated scatter data with the aid of easily
obtainable knowledge of SPR (scatter-to-primary ratio) at a single reference point. We validated the SC method using a
CIRS breast phantom with iodine inserts. We evaluated its efficacy in terms of SDNR and iodine quantitative accuracy.
We also applied our SC method to a patient DE-CE-DBT study and showed that the SC allowed detection of a
previously confirmed tumor at the edge of the breast. The SC method is quick to use and may be useful in a clinical
setting.
Contrast enhanced digital breast tomosynthesis can yield superior visualization of tumors relative to conventional
tomosynthesis and can provide the contrast uptake kinetics available in breast MR while maintaining a higher image
spatial resolution. Conventional dual-energy (DE) acquisition protocols for contrast enhancement at a given time point
often involve two separate continuous motion sweeps of the X-ray tube (one per energy) followed by weighted
subtraction of the HE (high energy)and LE (low energy) projection data. This subtracted data is then reconstructed.
Relative to two-sweep acquisition, interleaved acquisition suffers from a lesser degree of patient motion artifacts and
entails less time spent under uncomfortable breast compression. These advantages for DE interleaved acquisition are
reduced by subtraction artifacts due to the fact that each HE, LE acquisition pair is offset in angle for the usual case of
continuous tube motion. These subtraction artifacts propagate into the reconstruction and are present even in the absence
of patient motion. To reduce these artifacts, we advocate a strategy in which the HE and LE projection data are
separately reconstructed then undergo weighted subtraction in the reconstruction domain. We compare the SDNR of
masses in a phantom for the subtract-then-reconstruct vs. reconstruct-then-subtract strategies and evaluate each strategy
for two algorithms, FBP and SART. We also compare the interleave SDNR results with those obtained with the
conventional dual-energy double-sweep method. For interleave scans and for either algorithm the reconstruct-thensubtract
strategy yields higher SDNR than the subtract-then-reconstruct strategy. For any of the three acquisition modes,
SART reconstruction yields better SDNR than FBP reconstruction. Finally the interleave reconstruct-then-subtract
method using SART yields higher SDNR than any of the double-sweep conventional acquisitions.
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