Contrast-enhanced spectral mammography with a photon-counting detector.
OBJECTIVE
Spectral imaging is a method in medical x-ray imaging to extract information about the object constituents by the material-specific energy dependence of x-ray attenuation. The authors have investigated a photon-counting spectral imaging system with two energy bins for contrast-enhanced mammography. System optimization and the potential benefit compared to conventional non-energy-resolved absorption imaging was studied.


METHODS
A framework for system characterization was set up that included quantum and anatomical noise and a theoretical model of the system was benchmarked to phantom measurements.


RESULTS
Optimal combination of the energy-resolved images corresponded approximately to minimization of the anatomical noise, which is commonly referred to as energy subtraction. In that case, an ideal-observer detectability index could be improved close to 50% compared to absorption imaging in the phantom study. Optimization with respect to the signal-to-quantum-noise ratio, commonly referred to as energy weighting, yielded only a minute improvement. In a simulation of a clinically more realistic case, spectral imaging was predicted to perform approximately 30% better than absorption imaging for an average glandularity breast with an average level of anatomical noise. For dense breast tissue and a high level of anatomical noise, however, a rise in detectability by a factor of 6 was predicted. Another approximately 70%-90% improvement was found to be within reach for an optimized system.


CONCLUSIONS
Contrast-enhanced spectral mammography is feasible and beneficial with the current system, and there is room for additional improvements. Inclusion of anatomical noise is essential for optimizing spectral imaging systems.
Department of Physics, Royal Institute of Technology, AlbaNova, SE-106 91 Stockholm, Sweden. fberg@mi.physics.kth.se
Erik
E
Fredenberg
Magnus
M
Hemmendorff
Björn
B
Cederström
Magnus
M
Aslund
Mats
M
Danielsson
D019985:Benchmarking; D003287:Contrast Media; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008327:Mammography / Q000295:instrumentation / Q000379:methods*; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D017785:Photons; D011829:Radiation Dosage
D003287:Contrast Media