Analytical optimization of digital subtraction mammography with contrast medium using a commercial unit

Abstract

Contrast-medium-enhanced digital mammography (CEDM) is an image subtraction technique which might help unmasking lesions embedded in very dense breasts. Previous works have stated the feasibility of CEDM and the imperative need of radiological optimization. This work presents an extension of a former analytical formalism to predict contrast-to-noise ratio (CNR) in subtracted mammograms. The goal is to optimize radiological parameters available in a clinical mammographic unit (x-ray tube anode/filter combination, voltage, and loading) by maximizing CNR and minimizing total mean glandular dose (D(gT)), simulating the experimental application of an iodine-based contrast medium and the image subtraction under dual-energy nontemporal, and single- or dual-energy temporal modalities. Total breast-entrance air kerma is limited to a fixed 8.76 mGy (1 R, similar to screening studies). Mathematical expressions obtained from the formalism are evaluated using computed mammographic x-ray spectra attenuated by an adipose/glandular breast containing an elongated structure filled with an iodinated solution in various concentrations. A systematic study of contrast, its associated variance, and CNR for different spectral combinations is performed, concluding in the proposal of optimum x-ray spectra. The linearity between contrast in subtracted images and iodine mass thickness is proven, including the determination of iodine visualization limits based on Rose's detection criterion. Finally, total breast-entrance air kerma is distributed between both images in various proportions in order to maximize the figure of merit CNR2/D(gT). Predicted results indicate the advantage of temporal subtraction (either single- or dual-energy modalities) with optimum parameters corresponding to high-voltage, strongly hardened Rh/Rh spectra. For temporal techniques, CNR was found to depend mostly on the energy of the iodinated image, and thus reduction in D(gT) could be achieved if the spectral energy of the noniodinated image is decreased and the breast-entrance air kerma is evenly distributed between both acquisitions. Predicted limits, in terms of iodine concentration, are found to guarantee the visualization of common clinical angiogenic concentrations in the breast.

Clinical study of contrast-enhanced digital mammography and the evaluation of blood and lymphatic microvessel density

“…5 Our group has proposed a combination of both schemes called DE temporal (DET) 6 which offers advantages in the contrast-to-noise ratio of the resulting image; this proposal has been validated by data from a homogeneous phantom. 7 Under optimum performance of the technique, both subtraction modalities, SET and DET-if applied to the same set of images containing a given amount of iodine-should deliver equivalent results in terms of contrast, which under appropriate calibration can be translated into CM mass thickness.…”

Optimization of dual-energy subtraction for preclinical studies using a commercial MicroCT unit

“…To assess the impact of α on iodine detectability, contrast-to-noise ratio (CNR) was calculated in DE images with different α. The standard expression for CNR is ( 2 ) where V ρ , V 0 , σ ρ , σ 0 correspond to the mean HU and the standard deviation of resin with ρ and 0 mg/ml iodine concentration, respectively. A CNR expression explicitly dependent on α, and derived from the operational definition of the DE subtraction (Eq.…”

“…2 Usually in DE studies, an iodinated contrast medium (CM) is used to increase the contrast between uptake organs and surrounding tissue. The DE technique has been used to distinguish CM from bone, calcium and gold-based nanoparticles.…”

Phantom study to evaluate contrast‐medium‐enhanced digital subtraction mammography with a full‐field indirect‐detection system

“…In this work, we address the application of CEDM with a GE Senographe unit ͑GE Healthcare, Milwaukee, WI͒ because of its technical features ͑dual-track anode and wide voltage range͒ as well as the commercial prevalence in the U.S. and worldwide. 15 A recent work based on the analytical optimization of temporal and dual-energy applications of the CEDM technique with this commercial unit 16 has suggested that, although optimum spectral combinations were those including high-voltage strongly hardened Rh/Rh spectra, the use of Mo mammographic spectra for imaging the iodinated structure might provides a large advantage in contrast ͑of about 40%͒ over the optimized option. Due to this and the simplicity of use, low-energy spectra ͑below the iodine K edge͒ might represent an interesting alternative to higherenergy, hardened x-ray beams.…”