Evaluation of low-energy contrast-enhanced spectral mammography images by comparing them to full-field digital mammography using EUREF image quality criteria

Abstract

Objective: Contrast-enhanced spectral mammography (CESM) examination results in a low-energy (LE) and contrast-enhanced image. The LE appears similar to a full-field digital mammogram (FFDM). Our aim was to evaluate LE CESM image quality by comparing it to FFDM using criteria defined by the European Reference Organization for Quality Assured Breast Screening and Diagnostic Services (EUREF).

Methods: A total of 147 cases with both FFDM and LE images were independently scored by two experienced radiologists using these (20) EUREF criteria. Contrast detail measurements were performed using a dedicated phantom. Differences in image quality scores, average glandular dose, and contrast detail measurements between LE and FFDM were tested for statistical significance.

Results: No significant differences in image quality scores were observed between LE and FFDM images for 17 out of 20 criteria. LE scored significantly lower on one criterion regarding the sharpness of the pectoral muscle (p < 0.001), and significantly better on two criteria on the visualization of micro-calcifications (p = 0.02 and p = 0.034). Dose and contrast detail measurements did not reveal any physical explanation for these observed differences.

Conclusions: Low-energy CESM images are non-inferior to FFDM images. From this perspective FFDM can be omitted in patients with an indication for CESM.

Key points: • Low-energy CESM images are non-inferior to FFDM images. • Micro-calcifications are significantly more visible on LE CESM than on FFDM. • There is no physical explanation for this improved visibility of micro-calcifications. • There is no need for an extra FFDM when CESM is indicated.

Fig. 1

A typical contrast-enhanced spectral mammography (CESM) examination (only right mediolateral oblique view shown), consisting of a low-energy (a), high-energy (b) and recombined (c) image. A suspicious lesion is seen on the low-energy image, showing enhancement on the recombined image (white arrows). Histopathology showed invasive ductal carcinoma. The high-energy image is not for diagnostic purposes but is used for construction of the recombined image

Fig. 2

Average glandular dose (AGD) of the complete patient group values plotted against compressed breast thickness for the full-field digital mammography (FFDM) (open red circles) and low-energy (LE) (solid black triangles) exposures

Fig. 3

Threshold gold thickness detected as a function of gold disk diameter for a range of phantom thicknesses corresponding to breast thicknesses from (A) 32 mm to (E) 90 mm. The solid and dashed lines are data fits. In (C) the acceptable and achievable limits of the EUREF guidelines are also shown

Fig. 4

A 54-year-old female recalled from the breast cancer screening program (full-field digital mammography (FFDM) image) for a round mass in the left breast (*), also visible on the low-energy contrast-enhanced spectral mammography (CESM) image. On the recombined image, an ‘eclipse sign’ is visible, suggesting a cyst, and confirmed by targeted ultrasound. In this case, the sharpness of the pectoral muscle was scored ‘5’ on the FFDM image. On the low-energy CESM image, the delineation of the pectoral muscle was lost (white arrows), resulting in a score of ‘3’ from both radiologists