Quantitative contrast‐enhanced spectral mammography based on photon‐counting detectors: A feasibility study

Abstract

Purpose To investigate the feasibility of accurate quantification of iodine mass thickness in contrast-enhanced spectral mammography. Materials and Methods A computer simulation model was developed to evaluate the performance of a photon-counting spectral mammography system in the application of contrast-enhanced spectral mammography. A figure-of-merit (FOM), which was defined as the decomposed iodine signal-to-noise ratio (SNR) with respect to the square root of the mean glandular dose (MGD), was chosen to optimize the imaging parameters, in terms of beam energy, splitting energy, and pre-filtrations for breasts of various thicknesses and densities. Experimental phantom studies were also performed using a beam energy of 40 kVp and a splitting energy of 34 keV with 3 mm Al pre-filtration. A two-step calibration method was investigated to quantify the iodine mass thickness, and was validated using phantoms composed of a mixture of glandular and adipose materials, for various breast thicknesses and densities. Finally, the traditional dual-energy log-weighted subtraction method was also studied as a comparison. The measured iodine signal from both methods was compared to the known value to characterize the quantification accuracy and precision. Results The optimal imaging parameters, which lead to the highest FOM, were found at a beam energy between 42 to 46 kVp with a splitting energy at 34 keV. The optimal tube voltage decreased as the breast thickness or the Al pre-filtration increased. The proposed quantification method was able to measure iodine mass thickness on phantoms of various thicknesses and densities with high accuracy. The root-mean-square (RMS) error for cm-scale lesion phantoms was estimated to be 0.20 mg/cm2. The precision of the technique, characterized by the standard deviation of the measurements, was estimated to be 0.18 mg/cm2. The traditional weighted subtraction method also predicted a linear correlation between the measured signal and the known iodine mass thickness. However, the correlation slope and offset values were strongly dependent on the total breast thickness and density. Conclusion The results of the current study suggest that iodine mass thickness for cm-scale lesions can be accurately quantified with contrast-enhanced spectral mammography. The quantitative information can potentially improve the differential power for malignancy.

Investigation of spectral performance for single‐scan contrast‐enhanced breast CT using photon‐counting technology: A phantom study

“…In the FE image, the position of the sagittal slice is marked by a dashed line. ml) 19,22,50 and conventional breast CT (2 mg/ml) using energy-integrating detectors. 51 The VNC image provides additional information that can serve as a reliable substitute for a native CT image, making it possible to avoid an additional CT scan.…”

“…Using photon‐counting technology in a whole‐body CT, it has been demonstrated that the performance is comparable to conventional dual‐source CT scanners 33 . Investigations on CEM with a photon‐counting detector and DE subtraction also showed promising results 11,19,22 . High energy (HE) and low energy (LE) images are acquired simultaneously from a single x‐ray exposure and are used to perform DE subtraction.…”

“…6 In order to improve detection rates, contrast-enhanced imaging of the breast has been developed. This method is already established in breast MRI [7][8][9][10] and is also increasingly used in mammography [11][12][13][14][15][16][17][18][19][20][21][22] and breast CT (BCT). [23][24][25] To ensure the best possible contrast agent visibility, subtraction images are used in contrast-enhanced digital mammography (CEM), contrast-enhanced MRI, and contrastenhanced BCT.…”

“…33 Investigations on CEM with a photon-counting detector and DE subtraction also showed promising results. 11,19,22 High energy (HE) and low energy (LE) images are acquired simultaneously from a single x-ray exposure and are used to perform DE subtraction. This obviates incorrect registration between images and does not require additional radiation dose.…”

Cascaded systems analysis of charge sharing in cadmium telluride photon‐counting x‐ray detectors

“…Spectroscopic x‐ray imaging detectors are under development in academic and industry laboratories. Advantages of spectroscopic detectors over energy‐integrating detectors include improved dose efficiency and the potential for single‐exposure, material‐specific imaging …”