Fanny Jeunehomme

Development of contrast digital mammography.

Development of breast tumors is often accompanied by angiogenesis--the formation of new blood vessels. It is possible to image the effects of this process by tracking the uptake and washout of contrast agents in the vicinity of a lesion. In this article, a method for carrying out contrast subtraction mammography on a full-field digital mammography unit is described. Spectral measurements and modeling were performed to optimize the choice of x-ray target, kilovoltage and x-ray beam filtration for contrast digital mammography (CDM) on an available digital mammography system. Phantom studies were carried out to determine the sensitivity of CDM to iodine. Detection of iodine area densities of 0.3 mg/cm2 is possible for a circular object with a radius of 1.3 mm, which allows detection of uptake levels in the breast typically seen with cancer and some benign breast conditions. It was found that with a molybdenum anode x-ray tube, copper filtration could be used to effectively shape the x-ray spectrum to maximize the proportion of x rays with energies above the k edge of iodine. Simple logarithmic subtraction was found to be adequate in suppressing background signals dependent on the x-ray beam intensity and background thickness of the breast. The total x-ray dose from the procedure ranges between 1 and 3 mGy, similar to that from a conventional single view film mammogram. A clinical pilot study is currently being carried out to evaluate this technique.

Digital mammography using iodine-based contrast media: initial clinical experience with dynamic contrast medium enhancement.

Purpose:We sought to evaluate the potential of dynamic contrast enhancement after the intravenous administration of an iodine-based contrast medium in full-field digital mammography. Material and Methods:A protocol for image acquisition was established for contrast-enhanced mammography and the mammography unit (Senographe 2000D, GE Healthcare, Buc, France) changed as required. The effect of the protocol parameters on imaging was investigated. Subsequently, 21 patients with 25 suspicious lesions of the breast (10 benign, 1 borderline, and 14 malignant) underwent mammography with administration of an iodine-based contrast medium (Ultravist 370, Schering AG, Berlin, Germany), after approval of ethical committee as well as permission of German federal office for Radiation protection, and informed consent from each patient was obtained. Three sequential digital mammographic images of the respective breast were acquired after administration of the contrast medium at a dose of 1 mL/kg body weight and a flow of 4 mL/s. The postcontrast images were acquired 60, 120, and 180 seconds after administration. Subsequently, the precontrast image was logarithmically subtracted from the postcontrast images. Enhancement of the lesions was measured in absolute terms as well as relative to the enhancement of the glandular tissue. The subtracted images were evaluated for lesion depiction and dynamic contrast enhancement. Lesion-enhancement kinetics were compared with the histologic findings. Results:All malignant lesions were identified on the contrast-enhanced images of digital mammography. Three of the tumors (2 malignant, 1 benign) were detected only by contrast-enhanced mammography and not by standard mammography. Dynamic enhancement curves of benign and malignant tumors in contrast-enhanced mammography look similar to the curves known from gadolinium-enhanced magnetic resonance imaging. Nevertheless differentiation between malignant and benign tumors based on the enhancement patterns cannot be directly taken over from magnetic resonance imaging, as suggested by our initial results. The results are somewhat better when tumor enhancement relative to surrounding glandular tissue is used instead of absolute enhancement. Conclusion:The results of this preliminary study suggest that contrast-enhanced digital mammography is a potentially useful tool for the detection and the differentiation of benign and malignant breast lesions.

Controlling gray-level variation in contrast-enhanced digital mammography: design of a calibration procedure

Ideally, the gray level changes in a Contrast-Enhanced Digital Mammography (CEDM) sequence reflect the uptake and wash-out of contrast medium in the breast. While insignificant in standard mammography, gray level variations with time caused both by patient and system related factors, have been observed in clinical CEDM sequences. We have acquired phantom image series on digital mammography systems using a Mo/Cu anode-filter combination and a tube voltage between 45 and 49 kVp, in order to derive a model for gray level change with time as a function of system parameters. The gray level variation exhibits a fair degree of inter-series repeatability, and strongly depends on the dose received by the detector and timing of the image acquisition series. Moreover, for tissue-equivalent compositions, the relative gray level change with respect to the first image does not depend on the composition. We designed a calibration procedure that can be used to compensate for the tiny system-dependent signal variation that has been observed. A global reduction of 80-93% of the variation has been demonstrated in sequences acquired on a breast shaped phantom. Local improvement is effective across the whole field of view. When imaging iodine inserts (0.5-2 mg/cm2 concentration), the calibration increases the constancy with time of iodine signal on subtracted sequences by a factor of 4 (median value).

Selection of technique factors for contrast digital mammography

Although screen-film mammography is the current standard for detecting abnormalities in the breast, the sensitivity can range from 40-95 percent. One of the reasons this occurs is because surrounding dense tissues obscure the visualization of cancers. To address this issue, we are investigating contrast digital mammography (CDM), which involves imaging the uptake of a non-ionic iodinated contrast agent with full-field digital mammography to detect and characterize masses in the breast. The technical aspects, including spectral optimization and image processing, for the implementation of CDM have been investigated and a clinical trial is being carried out to study the technique. This article describes an experimental study using an iodine detail phantom in combination with various breast equivalent plastics to evaluate technique parameters used when imaging patients. It is desirable to find the technique parameters that will maximize iodine contrast while delivering a reasonably low dose to the patient. It was found that the contrast can be increased up to 53 percent for thinner breasts by increasing the dose to a level that still remains lower than the dose that would be received by the breast from conventional screening images.