Breast tissue characterization with photon-counting spectral CT imaging: a postmortem breast study

Abstract

Purpose: To investigate the feasibility of breast tissue characterization in terms of water, lipid, and protein contents with a spectral computed tomographic (CT) system based on a cadmium zinc telluride (CZT) photon-counting detector by using postmortem breasts.

Materials and methods: Nineteen pairs of postmortem breasts were imaged with a CZT-based photon-counting spectral CT system with beam energy of 100 kVp. The mean glandular dose was estimated to be in the range of 1.8-2.2 mGy. The images were corrected for pulse pile-up and other artifacts by using spectral distortion corrections. Dual-energy decomposition was then applied to characterize each breast into water, lipid, and protein contents. The precision of the three-compartment characterization was evaluated by comparing the composition of right and left breasts, where the standard error of the estimations was determined. The results of dual-energy decomposition were compared by using averaged root mean square to chemical analysis, which was used as the reference standard.

Results: The standard errors of the estimations of the right-left correlations obtained from spectral CT were 7.4%, 6.7%, and 3.2% for water, lipid, and protein contents, respectively. Compared with the reference standard, the average root mean square error in breast tissue composition was 2.8%.

Conclusion: Spectral CT can be used to accurately quantify the water, lipid, and protein contents in breast tissue in a laboratory study by using postmortem specimens.

Figure 1:

A schematic of the bench-top photon-counting spectral CT system.

Figure 2:

Graph shows experimentally measured tungsten anode spectrum at 100 kVp. The electronic noise floor and the splitting threshold between the low- and high-energy bins were noted as dashed lines at 22 and 42 keV, respectively.

Figure 3:

A, Low-energy CT image of a postmortem breast, and the corresponding decomposition images for, B, water, C, lipid, and, D, protein. The color scale represents the absolute volumetric fraction for different components in a given voxel.

Figure 4a:

Scatterplots show the right-left correlation of (a) water and (b) lipid contents measured from spectral CT by using dual-energy decomposition and (c, d) from chemical analysis. Linear fittings for all three contents are shown with dashed lines, which are in good agreement with the identity line.

Figure 4b:

Scatterplots show the right-left correlation of (a) water and (b) lipid contents measured from spectral CT by using dual-energy decomposition and (c, d) from chemical analysis. Linear fittings for all three contents are shown with dashed lines, which are in good agreement with the identity line.

Figure 4c:

Scatterplots show the right-left correlation of (a) water and (b) lipid contents measured from spectral CT by using dual-energy decomposition and (c, d) from chemical analysis. Linear fittings for all three contents are shown with dashed lines, which are in good agreement with the identity line.

Figure 4d:

Scatterplots show the right-left correlation of (a) water and (b) lipid contents measured from spectral CT by using dual-energy decomposition and (c, d) from chemical analysis. Linear fittings for all three contents are shown with dashed lines, which are in good agreement with the identity line.

Figure 5a:

Scatterplots show correlations of the volumetric fractions of (a) water, (b) lipid, and (c) protein contents derived from dual-energy images and chemical analysis. Linear fittings for all three components are shown with dashed lines, which are in good agreement with the identity line.

Figure 5b:

Scatterplots show correlations of the volumetric fractions of (a) water, (b) lipid, and (c) protein contents derived from dual-energy images and chemical analysis. Linear fittings for all three components are shown with dashed lines, which are in good agreement with the identity line.

Figure 5c:

Scatterplots show correlations of the volumetric fractions of (a) water, (b) lipid, and (c) protein contents derived from dual-energy images and chemical analysis. Linear fittings for all three components are shown with dashed lines, which are in good agreement with the identity line.