Showing papers on "Digital mammography published in 2004"
TL;DR: It was shown in both phantom imaging and patient imaging that the BP algorithm provided the best SDNR for low-contrast masses but the conspicuity of the feature details was limited by interplane artifacts; the FBP algorithms provided the highest edge sharpness for microcalcifications but the quality of masses was poor.
Abstract: Three algorithms for breast tomosynthesis reconstruction were compared in this paper, including (1) a back-projection (BP) algorithm (equivalent to the shift-and-add algorithm), (2) a Feldkamp filtered back-projection (FBP) algorithm, and (3) an iterative Maximum Likelihood (ML) algorithm. Our breast tomosynthesis system acquires 11 low-dose projections over a 50 degree angular range using an a-Si (CsI:Tl) flat-panel detector. The detector was stationary during the acquisition. Quality metrics such as signal difference to noise ratio (SDNR) and artifact spread function (ASF) were used for quantitative evaluation of tomosynthesis reconstructions. The results of the quantitative evaluation were in good agreement with the results of the qualitative assessment. In patient imaging, the superimposed breast tissues observed in two-dimensional (2D) mammograms were separated in tomosynthesis reconstructions by all three algorithms. It was shown in both phantom imaging and patient imaging that the BP algorithm provided the best SDNR for low-contrast masses but the conspicuity of the feature details was limited by interplane artifacts; the FBP algorithm provided the highest edge sharpness for microcalcifications but the quality of masses was poor; the information of both the masses and the microcalcifications were well restored with balanced quality by the ML algorithm, superior to the results from the other two algorithms.
355 citations
TL;DR: FFDM allowed a higher cancer detection rate than did SFM in the group aged 50-69, although the difference did not reach statistical significance, and SFM and FFDM with soft-copy reading are comparable techniques for population-based screening mammography programs.
Abstract: PURPOSE: To prospectively compare cancer detection rates, recall rates, and positive predictive values at screen-film mammography (SFM) with those at full-field digital mammography (FFDM) with soft-copy reading in a population-based screening program in Norway. MATERIALS AND METHODS: Of 43,429 women invited, 25,263 women aged 45–69 years attended the screening program and were randomized, with adjustments for age and area of residence, to undergo SFM or FFDM. Two standard views of each breast were acquired. Independent double reading was performed with use of a five-point rating scale for probability of cancer. Recall rates, positive predictive values, and cancer detection rates were compared for two age groups (45–49 and 50–69 years) by using the χ2 test. RESULTS: Overall, 73 cancers in 17,911 women were detected at SFM (detection rate, 0.41%), compared with 41 cancers in 6,997 women at FFDM (detection rate, 0.59%; P = .06). In the group aged 50–69 years, 56 cancers in 10,304 women were detected at SFM (...
238 citations
TL;DR: It is shown that the square root model based approach which FFDM allows leads to a robust estimation of the high frequency image noise, which provides better microcalcification detection performance when compared to the film-screen noise equalization method developed by Veldkamp.
Abstract: Equalizing image noise is shown to be an important step in the automatic detection of microcalcifications in digital mammography. This study extends a well established film-screen noise equalization scheme developed by Veldkamp et al. for application to full-field digital mammogram (FFDM) images. A simple noise model is determined based on the assumption that quantum noise is dominant in direct digital X-ray imaging. Estimation of the noise as a function of the gray level is improved by calculating the noise statistics using a truncated distribution method. Experimental support for the quantum noise assumption is presented for a set of step wedge phantom images. Performance of the noise equalization technique is also tested as a preprocessing stage to a microcalcification detection scheme. It is shown that the square root model based approach which FFDM allows leads to a robust estimation of the high frequency image noise. This provides better microcalcification detection performance when compared to the film-screen noise equalization method developed by Veldkamp. Substantially better results are obtained than when noise equalization is omitted. A database of 124 direct digital mammogram images containing 28 microcalcification clusters was used for evaluation of the method.
95 citations
TL;DR: The evidence is currently insufficient to support the use of any of the new technologies proposed for breast cancer screening in population screening, but would support further evaluation.
Abstract: We systematically reviewed the literature on the accuracy of new technologies proposed for breast cancer screening Four potential tests were identified (ultrasound, magnetic resonance imaging (MRI), full-field digital mammography (FFDM), and computer-aided detection (CAD)) for which primary studies met quality and applicability criteria and provided adequate data on test accuracy These technologies have been assessed in cross-sectional studies of test accuracy where the new test is compared to mammography Ultrasound, used as an adjunct to mammography in women with radiologically dense breasts, detects additional cancers and causes additional false positives Magnetic resonance imaging may have a better sensitivity (but lower specificity) than mammography in selected high-risk women, but studies of this technology included small number of cancers Computer-aided detection may enhance the sensitivity of mammography and warrants further evaluation in large prospective trials One study of FFDM suggests that it may identify some cancers not identified on conventional mammography and may result in a lower recall rate The evidence is currently insufficient to support the use of any of these new technologies in population screening, but would support further evaluation
89 citations
TL;DR: This prototype system takes advantage of many synergies between the co-registered digital mammography and pulse-echo ultrasound image data used for breast cancer detection and diagnosis, and innovative combinations of advanced US and X-ray applications are being implemented and tested along with the basic modes.
Abstract: This paper describes work aimed at combining 3D ultrasound with full-field digital mammography via a semi-automatic prototype ultrasound scanning mechanism attached to the digital mammography system gantry. Initial efforts to obtain high x-ray and ultrasound image quality through a compression paddle are proving successful. Registration between the x-ray mammogram and ultrasound image volumes is quite promising when the breast is stably compressed. This prototype system takes advantage of many synergies between the co-registered digital mammography and pulse-echo ultrasound image data used for breast cancer detection and diagnosis. In addition, innovative combinations of advanced US and X-ray applications are being implemented and tested along with the basic modes. The basic and advanced applications are those that should provide relatively independent information about the breast tissues. Advanced applications include x-ray tomosynthesis, for 3D delineation of mammographic structures, and non-linear elasticity and 3D color flow imaging by ultrasound, for mechanical and physiological information unavailable from conventional, non-contrast x-ray and ultrasound imaging.
75 citations
TL;DR: Although the initial cost of an FFDM system is high compared with that of an SFM system, digital mammography has inherent advantages, such as wide dynamic range, reduction in recall rates, potential for reduction in radiation dose, increased patient throughput, postprocessing capability, and digital acquisition.
Abstract: Recent advances in digital detector technology have paved the way to full-field digital mammography (FFDM) systems. The performance of these systems has evolved to the point where replacement of screen-film mammography (SFM) systems is becoming realistic. Despite some commonality between the two techniques, there are fundamental differences in how images are recorded, displayed, and stored. These differences necessitate an understanding of the principles of detection and the characteristics of digital images. Several approaches have been taken in the development of FFDM systems: (a) slot scanning with a scintillator and a charge-coupled device (CCD) array, (b) a flat-panel scintillator and an amorphous silicon diode array, (c) a flat-panel amorphous selenium array, (d) a tiled scintillator with fiberoptic tapers and a CCD array, and (e) photostimulable phosphor plates (computed radiography). Although the initial cost of an FFDM system is high compared with that of an SFM system, digital mammography has inherent advantages, such as wide dynamic range, reduction in recall rates, potential for reduction in radiation dose, increased patient throughput, postprocessing capability, and digital acquisition. These advantages and the rapidly occurring technologic developments will help establish FFDM as a mainstay of breast evaluation.
74 citations
TL;DR: The main parameters that characterize the performances of the current systems and influence the quality of digital images are briefly explained: spatial resolution, detective quantum efficiency and modulation transfer function.
Abstract: This paper reviews the different techniques available and competing for full-field digital mammography. The detectors are described in their principles: photostimulable storage phosphor plates inserted as a cassette in a conventional mammography unit, dedicated active matrix detectors (i.e., flat-panel, thin-film transistor-based detectors) and scanning systems, using indirect and direct X-ray conversion. The main parameters that characterize the performances of the current systems and influence the quality of digital images are briefly explained: spatial resolution, detective quantum efficiency and modulation transfer function. Overall performances are often the result of compromises in the choice of technology.
70 citations
TL;DR: This study presents a methodology for estimating the normalized glandular dose to the uncompressed breast using the geometry proposed for flat-panel CT breast imaging, and a computer program to provide normalized glandsular dose values has been made available online.
Abstract: The development of new digital mammography techniques such as dual-energy imaging, tomosynthesis and CT breast imaging will require investigation of optimal camera design parameters and optimal imaging acquisition parameters. In optimizing these acquisition protocols and imaging systems it is important to have knowledge of the radiation dose to the breast. This study presents a methodology for estimating the normalized glandular dose to the uncompressed breast using the geometry proposed for flat-panel CT breast imaging. The simulation uses the GEANT 3 Monte Carlo code to model x-ray transport and absorption within the breast phantom. The Monte Carlo software was validated for breast dosimetry by comparing results of the normalized glandular dose (DgN) values of the compressed breast to those reported in the literature. The normalized glandular dose was then estimated for a range of breast diameters from 10 cm to 18 cm using an uncompressed breast model with a homogeneous composition of adipose and glandular tissue, and for monoenergetic x-rays from 10 keV to 120 keV. These data were fit providing expressions for the normalized glandular dose. Using these expressions for the DgN coefficients and input variables such as the diameter, height and composition of the breast phantom, the mean glandular dose for any spectra can be estimated. A computer program to provide normalized glandular dose values has been made available online. In addition, figures displaying energy deposition maps are presented to better understand the spatial distribution of dose in CT breast imaging.
64 citations
TL;DR: Current evidence questions the recent move toward magnetic resonance imaging as a single or multimodality strategy for breast cancer screening, but in a high-risk group the cost effectiveness of technical innovations may be justified.
62 citations
TL;DR: Qualitative evaluation of a DEDM technique for calcification imaging of dual-energy digital mammography, where separate low- and high-energy images are acquired and synthesized to cancel the tissue structures, finds the measured aluminium thicknesses were found to be approximately linear with the trueuminium thicknesses and independent of the underlying glandular-tissue composition.
Abstract: Dual-energy digital mammography (DEDM), where separate low- and high-energy images are acquired and synthesized to cancel the tissue structures, may improve the ability to detect and visualize microcalcifications. Under ideal imaging conditions, when the mammography image data are free of scatter and other biases, DEDM could be used to determine the thicknesses of the imaged calcifications. We present quantitative evaluation of a DEDM technique for calcification imaging. The phantoms used in the evaluation were constructed by placing aluminium strips of known thicknesses (to simulate calcifications) across breast-tissue-equivalent materials of different glandular-tissue compositions. The images were acquired under narrow-beam geometry and high exposures to suppress the detrimental effects of scatter and random noise. The measured aluminium thicknesses were found to be approximately linear with the true aluminium thicknesses and independent of the underlying glandular-tissue composition. However, the dual-energy images underestimated the true aluminium thickness due to the presence of scatter from adjacent regions. Regions in the DEDM image that contained no aluminium yielded very low aluminium thicknesses (<0.07 mm). The aluminium contrast-to-noise ratio in the dual-energy images increased with the aluminium thickness and decreased with the glandular-tissue composition. The changes to the aluminium contrast-to-noise ratio and the contrast of the tissue structures between the low-energy and DEDM images are also presented.
59 citations
Journal Article•
TL;DR: The most interesting technique offered by nuclear medicine today are PET and lymphoscintigraphy with the intraoperative detection of handled gamma probe and PET guided by tumor markers measurements shows to detect more lesions than other non nuclear medicine modalities.
Abstract: Breast tumors can be imaged by different modalities: mammography is the most widely used technique because of its diagnostic value, patient compliance and low costs. Some techniques such as ultrasound (US) are often indicated, while others, such as digital mammography and magnetic resonance imaging (MRI) are still under evaluation and seem to be very promising. Among the nuclear medicine techniques breast scintigraphy with (99m)Tc-labelled lipophilic cations (SestaMIBI or tetrofosmin), positron emission tomography (PET) with 18F-2-deoxy-2-fluoro-D-glucose (FDG) have been evaluated in many clinical trials. At present breast scintigraphy has limited applications due to its poor spatial resolution, which has a minimum of 8 mm. It is questionable whether single photon emission tomography (SPECT) can offer any substantially better information on the breast; however, SPECT is more accurate in detecting axillary lymph nodes. Recent approaches using breast dedicated collimators and cameras have greatly improved the SPECT resolution and sensitivity. The most interesting technique offered by nuclear medicine today are PET and lymphoscintigraphy with the intraoperative detection of handled gamma probe. The sentinel node detection has achieved a large consensus of reliability and at present it has an important place in the clinical management. In the same time many authors have acknowledged the value of PET in the differential diagnosis of breast lesions and in locoregional staging, since breast cancer is strongly avid for glucose. PET demonstrated also its efficacy in detecting axillary lymph node metastases. Even in some clinical trials its accuracy proved nearly comparable to that of lymphoscintigraphy with sentinel node biopsy, other studies showed that PET scanning does not currently have adequate spatial resolution to detect both micro- and small macrometastatic disease in axillary lymph nodes. The added value of PET in breast cancer staging is that with a single examination PET allows the characterisation of breast lesions, in addition to complete viewing of the entire body. Whole-body PET may substitute other diagnostic assessments by examining the various regions of potential tumour spread. The current diagnostic work-up for pre- and postoperative staging includes various examinations: chest X-rays, US of the abdomen, mammography of the contralateral breast. Bone scintigraphy with (99m)Tc-diphosphonates and laboratory tests can also be considered in women with large tumors or in symptomatic patients. Computed tomography (CT) and MRI may be used in order to resolve particular diagnostic problems. The current application of some of these modalities depends on the risk of the single patient of developing metastatic spread, which is revealed by a number of prognostic parameters of tumor aggressiveness and of course, clinical stage. Bone scintigraphy and PET may be useful in monitoring therapy response and in detecting tumour relapses during follow-up. In particular PET guided by tumor markers measurements shows to detect more lesions than other non nuclear medicine modalities.
TL;DR: This review aims to describe the different technologies, introduce concepts related to image quality and review the current evidence for the use of digital mammography systems in clinical practice.
11 Nov 2004-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The experimental results provide additional information on the performance of the mammographic system for a broader range of experimental conditions than have been reported in the past and demonstrate good agreement with theoretical estimates under various spectral conditions.
Abstract: The physical performance characteristics of a flat-panel clinical full-field digital mammography (FFDM) system were investigated for a variety of mammographic X-ray spectral conditions. The system was investigated using 26 kVp: Mo/Mo, 28 kVp: Mo/Rh, and 30 kVp: Rh/Rh, with polymethyl methacrylate (PMMA) “tissue equivalent material” of thickness 20, 45, and 60 mm for each of three X-ray spectra, resulting in nine different spectral conditions. The experimental results were compared with a theoretical cascaded linear systems-based model that has been developed independently by other investigators. The FFDM imager (Senographe 2000D, GE Medical Systems, Milwaukee, WI) uses an amorphous silicon (aSi:H) photodiode (100 μm pixel) array directly coupled to a cesium iodide (CsI) scintillator. The spatial resolution of the digital mammography system was determined by measuring the presampling modulation transfer function (MTF). The noise power spectra (NPS) of the system were measured under the different mammographic X-ray spectral conditions at an exposure of approximately 10 mR to the detector from which corresponding detective quantum efficiencies (DQE) were determined. The experimental results provide additional information on the performance of the mammographic system for a broader range of experimental conditions than have been reported in the past. The flat-panel imager exhibits favorable physical quality characteristics under the conditions investigated. The experimental results were compared with theoretical estimates under various spectral conditions and demonstrated good agreement.
TL;DR: No statistically significant difference in diagnostic accuracy between the Fischer Senoscan and screen-film mammography was detected in this study.
Journal Article•
TL;DR: While screening mammography is recognized as the most effective method for early detection of breast cancer, this modality has limitations that are the driving force behind efforts to refine existing mammography technologies and develop new ones offering improved detection of Breast cancer.
Abstract: While screening mammography is recognized as the most effective method for early detection of breast cancer, this modality has limitations that are the driving force behind efforts to refine existing mammography technologies and develop new ones offering improved detection of breast cancer. Full-field digital mammography (FFDM) systems use digital detectors to convert x-ray photons to digital signals for display on high-resolution monitors. These systems offer capabilities not provided by conventional film-screen mammography. Contrast-enhanced mammography utilizes the basic biological principle that aggressive cancers are associated with increased vascularity. Iodinated contrast agents--the same used in computed tomography (CT) examinations--are administered through an injection in a vein usually in the arm. They distribute throughout the blood system, and x-ray imaging shows increased contrast in areas where they concentrate. Tomosynthesis acquisition involves acquiring multiple images of a stationary compressed breast at different angles during a short scan. The individual images are then reconstructed into a 3D series of thin high-resolution slices. The slices can be displayed individually or in a dynamic cine mode. The individual slices reduce tissue overlap and structure noise relative to standard 2D projection mammography, with a total dose comparable to that required for standard screening mammography. Initial efforts are underway to develop prototype systems to achieve high-resolution, whole-breast 3D ultrasound images that are co-registered with digital mammograms. This technology has the potential to improve specificity in breast imaging studies, particularly in dense breasts. Computer-aided detection (CAD) programs are intended to help radiologists identify suspicious lesions that may otherwise be overlooked. CAD software works similarly to a spellchecker and has the potential to increase the detection of cancer Magnetic resonanace imaging (MRI) is a generally accepted diagnostic procedure for a number of breast related indications. Its greatest strength is that it is very sensitive to tumors. If a suspected area does not exhibit contrast agent uptake, the probability that it is malignant is very small. Conversely, its specificity is poorer. If the area does show enhancement, it may or may not be a tumor. Further imaging or biopsy may be needed to resolve the question. Ultrasound holds promise as a method for detection of cancers in women with dense breast tissue, which is often problematic with conventional film-screen mammography. Ultrasound has also assumed an important role in breast imaging, as an adjunct to diagnostic mammography for biopsy guidance, palpable mass evaluation, and serial evaluation of benign masses.
25 Jul 2004
TL;DR: This work proposes a neural-genetic algorithm for feature selection in conjunction with neural network based classifier and combined the computer-extracted statistical features from the mammogram with the human-extraction features for classifying different types of small breast abnormalities.
Abstract: Digital mammography is one of the most suitable methods for early detection of breast cancer. In uses digital mammograms to find suspicious areas. However, it is very difficult to distinguish benign and malignant cases, especially for the small size lesions in the early stage of cancer. This is reflected in the high percentage of unnecessary biopsies that are performed and many deaths caused by late detection or misdiagnosis. A computer based feature selection and classification system can provide a second opinion to the radiologists. This work proposes a neural-genetic algorithm for feature selection in conjunction with neural network based classifier. It also combined the computer-extracted statistical features from the mammogram with the human-extracted features for classifying different types of small breast abnormalities. It obtained 90.5% accuracy rate for calcification cases and 87.2% for mass cases with difference feature subsets. The obtained results show that different types of breast abnormality should use different features for classification.
TL;DR: In this article, the percent breast density was determined using computer-assisted interactive thresholding software from sixty consecutive mammograms of women undergoing digital screening mammography with a prior film-screen mammogram obtained within the last two years.
Abstract: Breast density is a moderate risk factor for breast cancer based on quantitative measurement of percent breast density from film-screen mammograms In this study, percent breast density was determined using computer-assisted interactive thresholding software from sixty consecutive mammograms of women undergoing digital screening mammography with a prior film-screen mammogram obtained within the last two years Observations were made regarding discrepancies in density readings Percent breast density was significantly lower for digital mammograms (mean 322%) compared to analog mammograms (mean 403%) (p 50% density) Differences in density readings between analog and digital mammography were largely observed to be due to better recognition of the skin line on digital mammograms resulting in inclusion of more subcutaneous fat D
TL;DR: Results of this study were compared with those of other surveys, showing that full-field digital mammography allows a significant clinical dose reduction compared with screen/film mammography.
Abstract: The aim of this study was to compare performance and patient dose of full-field digital mammography units for clinical use Measurements of linearity and automatic exposure control stability were performed on four units installed in as many Italian sites The tube output was also obtained by the same ionization chamber, permitting to evaluate ratios mGy/mAs for each available spectrum The entrance air-kerma was calculated over a sample of 800 cranio-caudal mammograms and the average glandular dose obtained, assuming two mean glandular compositions of 50 and 30%, respectively Digital systems showed very good linearity and comparable responses The stability of the automatic exposure control was better than 5% for all systems Regarding doses, the two mammography units that work mainly in contrast mode deliver, respectively, 17 and 28% more dose compared with those working in standard mode For the latter mode, the mean average glandular dose was in the range 125-137 mGy and 137-149 mGy for the 50 and 30% glandular composition, respectively Results of this study were compared with those of other surveys, showing that full-field digital mammography allows a significant clinical dose reduction compared with screen/film mammography
06 May 2004
TL;DR: The results indicate that the FPD-CBCTBI technique effectively removes structure overlap and significantly improves the detectability of small breast tumors, and demonstrates CBCTBI offers good image quality with the radiation dose level less than or equal to that of conventional mammography.
Abstract: Conventional film-screen mammography is the most effective tool for the early detection of breast cancer currently available. However, conventional mammography has relatively low sensitivity to detect small breast cancers (under several millimeters) owing to an overlap in the appearances of benign and malignant lesions, and surrounding structure. The limitations accompanying conventional mammography is to be addressed by incorporating a cone beam CT imaging technique with a recently developed flat panel detector. Computer simulation and preliminary studies have been performed to prove the feasibility of developing a flat panel detector-based cone beam CT breast imaging (FPD-CBCTBI) technique. A preliminary system characterization study of flat panel detector-based cone beam CT for breast imaging was performed to confirm the findings in the computer simulation and previous phantom studies using the current prototype cone beam CT scanner. The results indicate that the CBCTBI technique effectively removes structure overlap and significantly improves the detectability of small breast tumors. More importantly, the results also demonstrate CBCTBI offers good image quality with the radiation dose level less than or equal to that of conventional mammography. The results from this study suggest that FPD-CBCTBI is a potentially powerful breast-imaging tool.
TL;DR: In this investigation the effect of JPEG 2000 compression on the contrast-detail (CD) characteristics of digital mammography images was studied using an alternative forced choice (AFC) technique.
Abstract: In this investigation the effect of JPEG 2000 compression on the contrast-detail (CD) characteristics of digital mammography images was studied using an alternative forced choice (AFC) technique. Images of a contrast-detail phantom, acquired using a clinical full-field digital mammography system, were compressed using a commercially available software product (JPEG 2000). Data compression was achieved at ratios of 1:1, 10:1, 20:1, and 30:1 and the images were reviewed by seven observers on a high-resolution display. Psychophysical detection characteristics were first computed by fitting perception data using a maximum-likelihood technique from which CD curves were derived at 50%, 62.5%, and 75% threshold levels. Statistical analysis indicated no significant difference in the perception of mean disk thickness up to 20:1 compression except for disk diameter of 1 mm. All other compression combinations exhibited significant degradation in CD characteristics.
06 May 2004
TL;DR: The proposed method provides full Image Quality benefit of digital mammography while minimizing dose to patients in a controlled and predictive way.
Abstract: A method for the determination of optimal operating points of digital mammography systems is described. The digital mammography equipment uses a flat panel detector and a bi-metal molybdenum/rhodium x-ray tube. An operating point is defined by the selection of the x-ray tube target material, x-ray filtration, kVp and detector entrance dose. Breast thickness and composition are estimated from a low dose pre-exposure, then used to index tables containing sets of operating points. The operating points are determined using a model of the image chain, which computes contrast to noise ratio (CNR) and average glandular dose (AGD) for all possible exposure conditions and breast thickness and composition combinations. The selected operating points are those which provide the required CNR for the lowest AGD. An AGD reduction of 30% to 50% can be achieved for comparable Image Quality, relative to current operating points. Resulting from the optimization process, the rhodium target is used in more than 75% of cases. Measurements of CNR and AGD have been performed on various tissue equivalent materials with good agreement between calculated and measured values. The proposed method provides full Image Quality benefit of digital mammography while minimizing dose to patients in a controlled and predictive way.
06 May 2004
TL;DR: In this article, two new selenium large area detectors are introduced for full-field digital mammography applications, which are capable of both static and dynamic imaging, and are quantum noise limited over the exposure ranges.
Abstract: In this paper, two new selenium large area detectors are introduced. The first detector is a 24x30cm detector suitable for full-field digital mammography applications. The second detector is a new 43x43cm detector for general radiographic applications. Both detectors are capable of static and dynamic imaging, and are quantum noise limited over the exposure ranges intended for their typical use. For static imaging applications, ghost and lag were compared on both detectors, and no measurable artefacts were reported. On dynamic imaging sequences, lag was shown to be significant on both detectors, and a method for reducing the artifact due to lag was presented.
TL;DR: The test phantom presented in this work permits image quality parameters to be evaluated objectively for three different types of breast tissue, and is a useful tool for optimizing the patient dose-image quality relationship.
Abstract: Our objective is to describe a new test phantom that permits the objective assessment of image quality in conventional and digital mammography for different types of breast tissue. A test phantom, designed to represent a compressed breast, was made from tissue equivalent materials. Three separate regions, with different breast tissue compositions, are used to evaluate low and high contrast resolution, spatial resolution and image noise. The phantom was imaged over a range of kV using a Contour 2000 (Bennett) mammography unit with a Kodak MinR 2190-MinR L screen-film combination and a Senograph 2000D (General Electric) digital mammography unit. Objective image quality assessments for different breast tissue compositions were performed using the phantom for conventional and digital mammography. For a similar mean glandular dose (MGD), the digital system gives a significantly higher contrast-to-noise ratio (CNR) than the screen-film system for 100% glandular tissue. In conclusion, in mammography, a range of exposure conditions is used for imaging because of the different breast tissue compositions encountered clinically. Ideally, the patient dose-image quality relationship should be optimized over the range of exposure conditions. The test phantom presented in this work permits image quality parameters to be evaluated objectively for three different types of breast tissue. Thus, it is a useful tool for optimizing the patient dose-image quality relationship.
TL;DR: Clinical experience in an IRB-approved research trial has suggested that digital mammography with photostimulable storage phosphors and a dedicated CR reader is a viable alternative to conventional screen-film mammography.
Abstract: Over the past several years, digital mammography systems have been installed clinically across North America in small but growing numbers. A photostimulable phosphor-based full-field digital mammography image was evaluated in this investigation. Commonly known as computed radiography (CR), its use closely mimics the screen-film mammography paradigm. System performance using modulation transfer function (MTF) and detective quantum efficiency (DQE) metrics show MTF(2.5 mm(-1)) = 0.5, DQE(2.5 mm(-1)) = 0.3, and MTF(5.0 mm(-1)) = 0.2, DQE(5.0 mm(-1)) = 0.05, for a 26 kVp beam, 0.03 mm molybdenum tube filtration, 4.5 cm tissue attenuation, and 15 mR incident exposure to the detector. Slightly higher DQE values were measured at 32 kVp with 0.025 mm rhodium tube filtration. CR mammography advantages include the ability to use existing mammography machines, where multiple rooms can be converted to "digital" operation, which allows overall cost savings compared to integrated digital mammography systems. Chief disadvantages include the labor-intensive handling of the cassettes prior to and after the imaging exam, lack of a direct interface to the x-ray system for recording technique parameters, and relatively slow processing time. Clinical experience in an IRB-approved research trial has suggested that digital mammography with photostimulable storage phosphors and a dedicated CR reader is a viable alternative to conventional screen-film mammography.
TL;DR: First results obtained with a monochromator module mounted at the exit of the X-ray tube of a conventional clinical mammography unit are presented, suggesting thatmonochromatization has a potential for improving image quality or decreasing dose in X-rays.
Abstract: X-ray spectra are composed of a broad bremsspectrum and anode-characteristic emission lines. In mammography typically molybdenum (Mo), rhodium (Rh) or tungsten (W) anodes are used in combination with Mo, Rh or aluminium filters. Only the photons with energies between 17 and 22 keV of the resulting spectrum are suitable for the soft tissue imaging needed for mammography. The aim of this article is to present first results obtained with a monochromator module mounted at the exit of the X-ray tube of a conventional clinical mammography unit. The experimental setup consists of a Siemens Mammomat 300, an X-ray monochromator module and a linear array detector for image acquisition. The technique is similar to the slot-scan technique known from digital mammography. The experimental machine allows to obtain images both with polychromatic and monochromatic X-rays. Initial evaluation of the system was performed by examination of a contrast-detail phantom (CD-MAM-phantom, Nijmegen, The Netherlands). Images done with the new monochromatic technique were compared to images of the phantom done with polychromatic spectra, with film-screen mammography as well as with digital mammography. The new technique with monochromatic slot-scan mammography resulted in correct identification of 93% of the phantom. Digital slot-scan mammography with polychromatic beam resulted in correct identification of 87%, digital full-field mammography in 83% and conventional film-screen mammography in 70% of the phantom. The results suggest that monochromatization has a potential for improving image quality or decreasing dose in X-ray mammography.
06 May 2004
TL;DR: Investigation of glandular dose to the breast in mammography can significantly be reduced without compromising image quality, when using photon counting technology, in a multi-slit scanning photon counting detector, compared to a conventional film mammography system and commercial available digital mammography systems with TFT-array detectors.
Abstract: The purpose of this study was to investigate if the glandular dose to the breast in mammography can significantly be reduced without compromising image quality, when using photon counting technology, in a multi-slit scanning photon counting detector, compared to a conventional film mammography system and commercial available digital
mammography systems with TFT-array detectors. A CDMAM phantom study, with two different thicknesses of additional PMMA absorber, 4 cm and 7 cm respectively, has shown that multi-slit scanning photon counting detector technology can reduce the dose, without reducing the image quality. This comparison was made to two commercial available digital mammography systems Senographe 2000D (from GEMS) and Selenia (from Lorad). The results show that dose can be reduced with 63% to 77%, depending on object thickness, when using XCT for mammography. This dose reduction has also been verified clinically through a small pilot study with patients and specimen, where the comparison was made between XCT and film.
TL;DR: The experimental results show that the classification algorithm performs well, reaching over 93% in accuracy with less number of rules compared with well-known decision trees and neural network classifier models.
Abstract: In this paper, we present an enhanced rough set approach for attribute reduction and generating classification rules from digital mammogram datasets. For this purpose, the presented approach is described in a hierarchical fashion. First, the preprocessing phase is adopted to enhance the contrast and edges of the mammogram images; moreover image processing segmentation algorithm is used to extract the region of interest. In the next phase, five texture features from the co-occurrence matrix are extracted and represented in attribute vector, and the reducts with minimal number of attributes are extracted. In the third phase, the decision rules within the generated reduct sets are generated. In the last phase, the classifier model was built and quadratic distances similarly function is used for matching process. To evaluate the validity of the rules based on the approximation quality of the attributes, we introduce a statistical test to evaluate the significance of the rules. The experimental results show that the classification algorithm performs well, reaching over 93% in accuracy with less number of rules compared with a well-known decision trees and neural network classifier models.
Journal Article•
TL;DR: The newCR mammography system improved physical imaging properties and detection of simulated microcalcifications over conventional CR mammography over the course of this study.
Abstract: PURPOSE To investigate the physical imaging properties and detection of simulated microcalcifications of a new computed radiography (CR) system with a pixel size of 50 microm for digital mammography. MATERIALS AND METHODS New and conventional CR were employed in this study. The new CR system included a high-resolution imaging plate coupled with the FCR5000MA (50 microm pixel pitch) including transparent support and a dual-sided reader. The conventional CR system was coupled with the FCR9000 (100 microm pixel pitch). Modulation transfer functions (MTFs) and Wiener spectra (WS) of the new and conventional CR systems were measured. Observer performance tests were conducted to compare the effects of pixel size (50 microm vs. 100 microm) on the diagnostic accuracy of CR systems in the detection of simulated microcalcifications. RESULTS The presampling MTF of the new CR system was higher at high frequencies than the conventional CR system. The WS of the new CR system was comparable to that of the conventional CR system at all frequencies. The area under the receiver operating characteristic (ROC) curve (Az) obtained with the new CR and the conventional CR systems were 0.84 and 0.79, respectively. Results showed that the detection of simulated clustered microcalcifications was significantly improved by use of the new CR system compared with the conventional CR system (p<0.05). CONCLUSION The new CR mammography system improved physical imaging properties and detection of simulated microcalcifications over conventional CR mammography.
06 May 2004
TL;DR: Measured total S/P-ratios below 3% are reported for breast range 3-8 cm, and the scatter-DQE is used as figure-of-merit for comparison to other imaging geometries and scatter rejection schemes.
Abstract: Measurements and Monte Carlo simulations were used to investigate
the scatter properties of a scanned multi-slit digital mammography system. Scatter to primary ratio (S/P) in the center of the image field was calculated for different thickness of breast equivalent material and different tube potentials. The simulated model also varied the angular acceptance, the number of slits and the distance between the slits of a dedicated scatter rejection device.
In addition to the expected scatter from the breast equivalent material, scatter within the detector contributes to the S/P-ratio. The main part of the scatter is identified as coming from this process. Measured total S/P-ratios below 3% are reported for breast range 3-8 cm. The scatter-DQE is used as figure-of-merit for comparison to other imaging geometries and scatter rejection schemes.
Journal Article•
TL;DR: To investigate how the greater contrast of full-field digital mammography (FFDM) affects the detection of suspicious lesions in Japanese population-based screening, 480 women aged 50 years or more were performed.
Abstract: PURPOSE To investigate how the greater contrast of full-field digital mammography (FFDM) affects the detection of suspicious lesions in Japanese population-based screening. MATERIALS AND METHODS Screen-film mammography (SFM) and FFDM were performed in 480 women aged 50 years or more. A set of mediolateral oblique views was obtained with each modality. All mammograms were independently double-read. The five-scale category assessment and type of finding using the Breast Imaging Reporting and Data system (BI-RADS) nomenclature were given. Intraobserver variance, recall rates, and positive predictive value were calculated. RESULTS The findings between the two modalities were discordant. kappa-values for each reader were 0.619 and 0.385, respectively. Almost half of the microcalcifications were called with both modalities. The detection of masses was less concordant between the readers (27%). The masses were detected more frequently with FFDM (73%). Other findings were only detected with one modality. The recall rate was not significantly different (2.9% with SFM vs. 4.2% with FFDM; p=0.253). The positive predictive value was not significantly different (14% with SFM vs. 10% with FFDM; p=0.69), either. Two patients with breast cancer were detected with both modalities. CONCLUSION Recall rates and positive predictive value were not significantly different between SFM and FFDM. Cancers were detected with both modalities.