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The purpose of this study was to evaluate the feasibility of spectral mammography using the dual-energy method to noninvasively distinguish between type I (calcium oxalate, CO) and type II (calcium hydroxyapatite, HA) microcalcifications. Two types of microcalcifications are difficult to distinguish due to a similar linear attenuation coefficient. In order to improve the detection efficiency of microcalcifications, we used the photon counting detector with energy discrimination capability and microcalcifications were classified into optimal energy bins. Two energy bins were used to obtain dualenergy images. In this study, photon counting spectral mammography system was simulated using Geant4 Application for Tomographic Emission (GATE) simulation tools. The thickness of the breast phantom was 3 cm and microcalcifications of various sizes ranging from 130-550 μm were embedded into the breast phantom. Microcalcifications were classified as being calcium hydroxyapatite or calcium oxalate based on score calculation with the dual-energy images. According to the results, the measured CNR of calcium hydroxyapatite (HA) was higher than that of the calcium oxalate (CO) in conventional single-energy image. In addition, two types of microcalcifications were distinguished using dual-energy analysis method. This classification represents better performance with a high energy of 50 kVp and an energy threshold of 30 keV. These results indicate that the classification performance was improved when the difference in the low energy image and high energy image was used. This study demonstrated the feasibility of photon counting spectral mammography for classification of breast microcalcifications. We expect that dual-energy method can reduce the frequency of biopsy and discriminate microcalcifications in mammography. These results are expected to potentially improve the efficiency of early breast cancer diagnosis.

Purpose: To investigate the potential of spectral mammography to distinguish between type I microcalcifications, consisting of calcium oxalate dihydrate compounds typically associated with benign lesions, and type II microcalcifications containing hydroxyapatite which are predominantly detected in malignant tumors. Methods: Simulation and phantom studies were carried out using polyenergetic spectra from a tungsten anode x-ray tube at low and high voltage (kVp) settings. Low- and high-energy attenuation ratios were calculated for microcalcifications of different types and thicknesses. Classification of type I or II calcifications was performed by using the attenuation ratio as a criterion. The results were evaluated using receiver operating characteristic (ROC) analysis. Results: In simulation studies, four combinations of dual (low and high kVp) energy exposure technique were investigated: 1) 30 kVp, 1 mm aluminum filtration and 50 kVp, 0.1 mm copper filtration; 2) 30 kVp, 1 mm Al and 50 kVp 0.2 mm Cu; 3) 30 kVp, 2 mm Al and 50 kVp, 0.1 mm Cu; and 4) 30 kVp 2 mm Al and 50 kVp, 0.2 mm Cu. In the ROC curve analysis, area under the curve (AUC) values were above 0.95 for all of the spectra with the exposure equivalent to 1.5 mGy of the mean glandular dose delivered to a 4 cm thick breast phantom. 30 kVp/2 mm Al and 50 kVp/0.1 mm Cu tube voltage/filter combinations demonstrated better performance compared to other combinations. In phantom studies, a 40 kVp setting paired with 1 mm Al filter and a 70 kVp setting paired with 0.1 mm Cu filter operated at 20 mAs technique were used. Obtained AUC value was also high (0.91), supporting the accuracy of the proposed classification method. Conclusion: The results of the current study suggest that dual energy mammography systems have potential to be used for discrimination between type I and type II microcalcifications to improve early breast cancer diagnosis and reduce the number of unnecessary breast biopsies.

Classification of clustered breast microcalcifications into benign and malignant categories is an extremely challenging task for computerized algorithms and expert radiologists alike. In this paper we present a novel method for feature selection based on mutual information (MI) criterion for automatic classification of microcalcifications. We explored the MI based feature selection for various texture features. The proposed method was evaluated on a standardized digital database for screening mammography (DDSM). Experimental results demonstrate the effectiveness and the advantage of using the MI-based feature selection to obtain the most relevant features for the task and thus to provide for improved performance as compared to using all features.

Imaging breast microcalcifications is crucial for early detection and diagnosis of breast cancer. It is challenging for current clinical ultrasound to image breast microcalcifications. However, new imaging techniques using data acquired with a synthetic-aperture ultrasound system have the potential to significantly improve ultrasound imaging. We recently developed a super-resolution ultrasound imaging method termed the phase-coherent multiple-signal classification (PC-MUSIC). This signal subspace method accounts for the phase response of transducer elements to improve image resolution. In this paper, we investigate the clinical feasibility of our super-resolution ultrasound imaging method for detecting breast microcalcifications. We use our custom-built, real-time synthetic-aperture ultrasound system to acquire breast ultrasound data for 40 patients whose mammograms show the presence of breast microcalcifications. We apply our super-resolution ultrasound imaging method to the patient data, and produce clear images of breast calcifications. Our super-resolution ultrasound PC-MUSIC imaging with synthetic-aperture ultrasound data can provide a new imaging modality for detecting breast microcalcifications in clinic without using ionizing radiation.

Ultrasound could be an attractive imaging modality for detecting breast microcalcifications, but it requires significant improvement in image resolution and quality. Recently, we have used tissue-equivalent phantoms to demonstrate that synthetic-aperture ultrasound has the potential to detect small targets. In this paper, we study the in vivo imaging capability of a real-time synthetic-aperture ultrasound system for detecting breast microcalcifications. This LANL's (Los Alamos National Laboratory's) custom built synthetic-aperture ultrasound system has a maximum frame rate of 25 Hz, and is one of the very first medical devices capable of acquiring synthetic-aperture ultrasound data and forming ultrasound images in real time, making the synthetic-aperture ultrasound feasible for clinical applications. We recruit patients whose screening mammograms show breast microcalcifications, and use LANL's synthetic-aperture ultrasound system to scan the regions with microcalcifications. Our preliminary in vivo patient imaging results demonstrate that synthetic-aperture ultrasound is a promising imaging modality for detecting breast microcalcifications.

A new method of acquiring and processing angular scatter data in ultrasonic imaging is presented. This method, based on the translating apertures algorithm, eliminates system-dependent changes in the received point spread function (psf) that are associated with more conventional methods of angular scatter measurement. This ensures that changes in the received echo are dominated by changes in the angular scattering behavior of insonified targets, and allows for the development of a variety of new imaging methods. Comparison of received echoes acquired at multiple interrogation angles serves to enhance the contrast of targets exhibiting variations in angular scattering behavior relative to the surrounding medium. Emphasis is placed on the improved ability to highlight biological targets that exhibit significant variations in compressibility or density relative to background tissue (e.g. breast microcalcifications, calcified atherosclerotic plaques). Simulation indicates the enhancement of breast microcalcification contrast by 10 - 30 dB over standard b-mode acquisition at 10 MHz. More sophisticated imaging methods involving the frequency dependence of angular scatter and angular speckle coherence are also discussed. Practical implementation and evaluation of this method on a modern imaging system is discussed, and expectations for the performance and utility of this algorithm in clinical diagnosis are investigated.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

False positive detections of microcalcifications by computer aided diagnosis (CADx) systems are a distraction to the radiologist and raise questions as to the eventual clinical utility of computer aided diagnosis systems. We have carefully analyzed the mammographic findings that appear in the locations of CADx detections and have counted and classified them.

The detection of breast microcalcifications is an important finding that can indicate the presence of breast cancer. Once detected, the radiologist attempts to classify the microcalcifications into patterns that are associated with benign or malignant processes. If they cannot be so classified they are considered indeterminate calcifications. Those characteristics of the microcalcifications that are used in this important distinction are the shape and number of calcifications and the presence or absence of any change from a prior mammogram. (1-4) Geometric magnification views are often obtained to provide better visualization of the microcalcifications. Although conventional screen film mammography has sufficient high contrast resolution (20 line pairs per mm (lplmm)) to demonstrate these findings and the type of hand held magnifying lens often used by Radiologists has sufficient power to demonstrate more than 30 lp/mm, in practice, the region containing the microcalcifications is often in a low contrast region of the image and the hand held magnifying lens does not suffice. We produce electronic magnification views of the breast by taking an existing screen film mammogram and digitizing it with a small pixel size. (5) The image is then displayed on a monitor or printed on a laser printer that has a larger pixel size, thereby resulting in magnification. The visibility of the calcifications is enhanced by changing the window level and window width to increase optical density or to decrease luminance and to increase contrast. The effect of these two actions is to correct in part for the low contrast in the original image. Three potential benefits results from electronic magnification: 1. The current film on which calcifications are seen can be magnified and evaluated without the patient having to return for a geometric magnification view. 2. The prior mammogram (if of suboptimal quality) can be digitized and re-displayed to better determine whether the microcalcifications have changed. 3. The digitized image may allow the reclassification of calcifications from benign appearance to a pattern suggestive of cancer, thereby resulting in an earlier decision to biopsy.