Dual-energy digital mammography for calcification imaging: scatter and nonuniformity corrections.

Mammographic images of small calcifications, which are often the earliest signs of breast cancer, can be obscured by overlapping fibroglandular tissue. We have developed and implemented a dual-energy digital mammography (DEDM) technique for calcification imaging under full-field imaging conditions using a commercially available aSi:H/CsI:Tl flat-panel based digital mammography system. The low- and high-energy images were combined using a nonlinear mapping function to cancel the tissue structures and generate the dual-energy (DE) calcification images. The total entrance-skin exposure and mean-glandular dose from the low- and high-energy images were constrained so that they were similar to screening-examination levels. To evaluate the DE calcification image, we designed a phantom using calcium carbonate crystals to simulate calcifications of various sizes (212-425 microm) overlaid with breast-tissue-equivalent material 5 cm thick with a continuously varying glandular-tissue ratio from 0% to 100%. We report on the effects of scatter radiation and nonuniformity in x-ray intensity and detector response on the DE calcification images. The nonuniformity was corrected by normalizing the low- and high-energy images with full-field reference images. Correction of scatter in the low- and high-energy images significantly reduced the background signal in the DE calcification image. Under the current implementation of DEDM, utilizing the mammography system and dose level tested, calcifications in the 300-355 microm size range were clearly visible in DE calcification images. Calcification threshold sizes decreased to the 250-280 microm size range when the visibility criteria were lowered to barely visible. Calcifications smaller than approximately 250 microm were usually not visible in most cases. The visibility of calcifications with our DEDM imaging technique was limited by quantum noise, not system noise.

[1]  A. Macovski,et al.  Energy-selective reconstructions in X-ray computerised tomography , 1976, Physics in medicine and biology.

[2]  W. Kalender,et al.  Evaluation of a prototype dual-energy computed tomographic apparatus. II. Determination of vertebral bone mineral content. , 1986, Medical physics.

[3]  Chris C Shaw,et al.  Dual-energy digital mammography: calibration and inverse-mapping techniques to estimate calcification thickness and glandular-tissue ratio. , 2003, Medical physics.

[4]  A Fenster,et al.  Dual-energy mammography: initial experimental results. , 1985, Medical physics.

[5]  H. Kundel,et al.  The influence of structured noise on the detection of radiologic abnormalities. , 1974, Investigative radiology.

[6]  J. Boone.  Normalized glandular dose (DgN) coefficients for arbitrary X-ray spectra in mammography: computer-fit values of Monte Carlo derived data. , 2002, Medical physics.

[7]  John M. Boone,et al.  Flat-field correction technique for digital detectors , 1998, Medical Imaging.

[8]  A. Macovski,et al.  Dual-energy x-ray projection imaging: two sampling schemes for the correction of scattered radiation. , 1988, Medical physics.

[9]  G S Shaber,et al.  Dual-energy mammography: a detector analysis. , 1990, Medical physics.

[10]  Xinming Liu,et al.  A dual-energy subtraction technique for microcalcification imaging in digital mammography--a signal-to-noise analysis. , 2002, Medical physics.

[11]  J M Boone.  Color mammography. Image generation and receiver operating characteristic evaluation. , 1991, Investigative radiology.

[12]  A Fenster,et al.  An accurate method for direct dual-energy calibration and decomposition. , 1990, Medical physics.

[13]  S Suryanarayanan,et al.  Full breast digital mammography with an amorphous silicon-based flat panel detector: physical characteristics of a clinical prototype. , 2000, Medical physics.

[14]  John M Lewin,et al.  Dual-energy contrast-enhanced digital subtraction mammography: feasibility. , 2003, Radiology.

[15]  E A Sickles,et al.  Mammographic detectability of breast microcalcifications. , 1982, AJR. American journal of roentgenology.

[16]  G T Barnes,et al.  An energy sensitive cassette for dual-energy mammography. , 1989, Medical physics.

[17]  Bernhard Erich Hermann Claus,et al.  Development and characterization of a dual-energy subtraction imaging system for chest radiography based on CsI:Tl amorphous silicon flat-panel technology , 2001, SPIE Medical Imaging.

[18]  W R Brody,et al.  A method for selective tissue and bone visualization using dual energy scanned projection radiography. , 1981, Medical physics.

[19]  Gary J. Whitman,et al.  Dual-energy digital mammography for calcification imaging: improvement by post-image processing , 2005, SPIE Medical Imaging.

[20]  E Samei,et al.  Detection of subtle lung nodules: relative influence of quantum and anatomic noise on chest radiographs. , 1999, Radiology.

[21]  A R Cowen,et al.  Dual-energy digital mammography utilizing stimulated phosphor computed radiography. , 1994, Physics in medicine and biology.

[22]  Jean-Marc Dinten,et al.  Evaluation of dual-energy radiography with a digital x-ray detector , 2001 .

[23]  S J Riederer,et al.  Dual-energy projection radiography: initial clinical experience. , 1981, AJR. American journal of roentgenology.

[24]  S. Kappadath,et al.  Quantitative evaluation of dual-energy digital mammography for calcification imaging. , 2004, Physics in medicine and biology.

[25]  G. Barnes,et al.  Normalized average glandular dose in molybdenum target-rhodium filter and rhodium target-rhodium filter mammography. , 1994, Radiology.

[26]  M Gambaccini,et al.  Dual-energy imaging in full-field digital mammography: a phantom study. , 2003, Physics in medicine and biology.

[27]  C A Mistretta,et al.  Single-exposure dual-energy computed radiography: improved detection and processing. , 1990, Radiology.

[28]  T. Ishigaki,et al.  One-shot dual-energy subtraction imaging. , 1986, Radiology.

[29]  R. Brooks.  A Quantitative Theory of the Hounsfield Unit and Its Application to Dual Energy Scanning , 1977, Journal of computer assisted tomography.

[30]  A. Macovski,et al.  Generalized image combinations in dual KVP digital radiography. , 1981, Medical physics.

[31]  M J Yaffe,et al.  Theoretical optimization of dual-energy x-ray imaging with application to mammography. , 1985, Medical physics.

[32]  Gary J. Whitman,et al.  Dual-energy digital mammography for calcification imaging: theory and implementation , 2004, SPIE Medical Imaging.

[33]  Elsa Arribas,et al.  Visibility of simulated microcalcifications--a hardcopy-based comparison of three mammographic systems. , 2005, Medical physics.

[34]  A. Fenster,et al.  Split-filter computed tomography: a simple technique for dual energy scanning. , 1980, Journal of computer assisted tomography.