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.
KEYWORDS: Signal to noise ratio, Modulation transfer functions, Systems modeling, Imaging systems, Sensors, Tissues, Digital breast tomosynthesis, Breast imaging, X-rays, Interference (communication)
Contrast enhanced (CE) breast imaging has been proposed as a method to increase the sensitivity and specificity of
breast cancer detection. Because malignant lesions often exhibit angiogenesis, the uptake of radio-opaque contrast agents (e.g. iodine) results in increased attenuation compared to the background tissue. Both planar CE digital mammography (CE-DM) and digital breast tomosynthesis (CE-DBT) have been proposed, using temporal or dual energy (DE) subtraction to remove tissue backgrounds. In the current study, we apply a cascaded linear systems model approach to analyze CE techniques with DE subtraction for designing a diagnostic imaging study, including the effects of contrast dynamics. We apply the model for both CE-DM and CE-DBT to calculate the ideal observer signal-to-noise ratio (SNR)
for the detection of I contrast objects of different sizes and concentrations. The calculation of this figure-of-merit (FOM) was be used to optimize CE clinical imaging protocols.
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.
KEYWORDS: Signal to noise ratio, Digital breast tomosynthesis, Iodine, Tissues, X-rays, Breast, X-ray imaging, Sensors, Dual energy imaging, 3D image processing
Digital breast tomosynthesis (DBT) is a three-dimensional (3D) x-ray imaging modality that has recently been employed
to increase lesion conspicuity through the removal of overlying tissue. Recently, a great deal of work has been devoted
to the development of contrast enhanced (CE) DBT. Radio-opaque contrast agents (e.g. iodine) are injected into patients
with suspicious breast lesions, with the goal of differentiating malignant tumors from benign by imaging the contrast
uptake signature associated with angiogenesis. Either temporal subtraction (TS) or dual energy (DE) subtraction may be
performed to further remove structural noise from the images. The current work quantifies the change in power-law
noise after either DE subtraction or TS using structured breast tissue equivalent phantoms. Additionally, iodine contrast
filled phantoms were used to determine the effect of x-ray energy and image subtraction technique on the signaldifference-
to-noise ratio (SDNR). Finally, we investigate the improvement in imaging performance of an amorphous
selenium (a-Se) direct conversion flat panel detector with increased a-Se thickness.
KEYWORDS: Digital breast tomosynthesis, 3D modeling, Signal to noise ratio, Interference (communication), X-rays, Systems modeling, Breast, Tissues, Optimization (mathematics), 3D image processing
Digital breast tomosynthesis (DBT) is a three-dimensional (3D) x-ray imaging modality that has been shown to decrease
the obscuring effect of breast structural noise, thereby increasing lesion conspicuity. To further improve breast cancer
detection, much recent work has been devoted to the development of contrast enhanced DBT (CEDBT). Taking
advantage of angiogenesis in malignant tissue, CEDBT involves the injection of radio-opaque material (i.e. iodine) and
measures the relative increase in uptake of contrast in breast cancer. Either temporal or dual energy subtraction
techniques may be used to implement CEDBT. Our present work is to develop a cascaded linear system model for DBT
with a CEDBT option to calculate the ideal observer signal to noise ratio (SNR) of lesions in the presence of structural
noise, evaluate the efficacy of CEDBT in the removal of structural noise, and examine the associated increase in x-ray
quantum noise. Our model will include the effects of dual energy subtraction on signal and noise transfer, and transfer of
power-law form anatomical noise through a DBT system using a modified filtered backprojection (FBP) algorithm. This
model will be used for the optimization of x-ray techniques and reconstruction filters in CEDBT.
KEYWORDS: Digital breast tomosynthesis, Advanced distributed simulations, Signal to noise ratio, Image filtering, Modulation transfer functions, 3D modeling, X-rays, Electronic filtering, Breast, Tissues
Digital breast tomosynthesis (DBT) has been shown to decrease breast structural noise thus improving the detection of
masses. However decreased detectability of microcalcifications was observed, and several studies have been performed
to investigate the benefit of taking an additional central projection view after a DBT scan. Our study investigates the
effect of variable angular dose distribution within a single DBT scan. Using a prototype DBT system with uniform
angular dose distribution, several DBT scans (25 projection views over 40 degree angular range) were performed using
different glandular doses. A subset of projection images was selected from each scan to form composite DBT scans (25
views each) with different angular dose distribution schemes (ADS). Two examples of ADS were: 1) seven central views
with four times the dose of periphery; and 2) five central projections with six times the dose of periphery. The total dose
for each ADS was the same as a reference scan with uniform dose distribution (1.5 mGy). They also had the same
number of views and angular range, and were reconstructed using identical reconstruction filter settings. The
detectability of calcifications, the 3D MTF and NPS of the system, and the ideal observer object detectability index for
all cases were compared. The results showed that higher dose for the central views improve the detectability of
calcifications. However magnitude of improvement depends on the reconstruction method and the size of the object.
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