We have developed dual energy (DE) iodine contrast imaging functions with a commercial mammography and
tomosynthesis system. Our system uses a tungsten target x-ray tube and selenium direct conversion detector.
Conventional low energy (LE) images were acquired with existing Rh, Ag and Al filters at the screening doses while the
high energy images (HE) were acquired with new Cu filters at half of the screening doses. In DE 2D mode, a pair of LE
and HE images was taken with one second delay time between and with anti-scatter grid. In DE 3D mode, 22 views of
alternating LE and HE were taken over 15 degrees angle in seven seconds without grid while tube was scanned
continuously. We used log-subtraction algorithm to obtain clean DE images with the subtraction factor K derived
empirically. In 3D mode, the subtraction was applied to each pair of LE and HE slices after reconstruction. The x-ray
technique optimization was done with simulation and phantom study. We performed both phantom and patient studies to
demonstrate the advantage of iodine contrast imaging. Among several new things in our work, a selenium detector
optimized for DE imaging was tested and a large dose advantage was demonstrated; 2D and 3D DE images of a breast
under same compression were acquired with a unique DE combo mode of the system, allowing direct image quality
comparison between 2D and 3D modes. Our study showed that new DE system achieved good image quality. DE
imaging is be a promising modality to detect breast cancer.
A new generation of digital breast tomosynthesis system has been designed and is commercially available outside the US.
The system has both a 2D mode and a 3D mode to do either conventional mammography or tomosynthesis. Uniquely, it
also has a fusion mode that allows both 3D and 2D images to be acquired under the same breast compression, which results in co-registered images from the two modalities. The aim of this paper is to present a technical description on the design and performance of the new system, including system details such as filter options, doses, AEC operation, 2D and 3D images co-registration and display, and the selenium detector performance. We have carried out both physical and clinical studies to evaluate the system. In this paper the focus will be mainly on technical performance results.
Single Mo target, Mo / Rh, or Mo / W bi-track targets with corresponding Mo and Rh filters have provided optimal
target / filter combinations for traditional screen / film systems. In the advent of full-field digital mammography, similar
target / filter combinations were adopted directly for digital imaging systems with direct and indirect conversion based
detectors. To reduce the average glandular dose while maintaining the clinical image quality of FFDMs, alternative
target / filter combinations have been investigated extensively to take advantages of the digital detectors with high
dynamic range, high detection dose efficiency, and low noise level. This paper reports the development of a digital
FFDM system that is equipped with single tungsten target and rhodium and silver filters. A mathematical model was
constructed to quantitatively simulate x-ray spectra, breast compositions, contrast objects, x-ray scatter distribution, grid
performance, and characteristics of a-Se flat panel detector. Computer simulations were performed to select kV/filter for
different breast thickness and breast compositions through maximizing the contrast object detection dose efficiency. A
set of phantom experiments were employed to optimize the x-ray techniques within the constraints of exposure time and
required dose levels. A 50-micrometer rhodium filter was applied for thin and average breasts and a 50-micrometer
silver filter for thicker breasts. To meet our design requirements and EUREF protocol specifications, we finely adjusted
x-ray techniques for 0.45, 0.75, 1.0, 1.35 mGy dose modes with regards to ACR phantom scoring and PMMA phantom
SNR/CNR performance, respectively. The optimal x-ray techniques significantly reduce average glandular dose while
maintaining imaging performance.