Improved visualization of breast cancer features in multifocal carcinoma using phase-contrast and dark-field mammography: an ex vivo study

Abstract

Objectives: Conventional X-ray attenuation-based contrast is inherently low for the soft-tissue components of the female breast. To overcome this limitation, we investigate the diagnostic merits arising from dark-field mammography by means of certain tumour structures enclosed within freshly dissected mastectomy samples.

Methods: We performed grating-based absorption, absolute phase and dark-field mammography of three freshly dissected mastectomy samples containing bi- and multifocal carcinoma using a compact, laboratory Talbot-Lau interferometer. Preoperative in vivo imaging (digital mammography, ultrasound, MRI), postoperative histopathological analysis and ex vivo digital mammograms of all samples were acquired for the diagnostic verification of our results.

Results: In the diagnosis of multifocal tumour growth, dark-field mammography seems superior to standard breast imaging modalities, providing a better resolution of small, calcified tumour nodules, demarcation of tumour boundaries with desmoplastic stromal response and spiculated soft-tissue strands extending from an invasive ductal breast cancer.

Conclusions: On the basis of selected cases, we demonstrate that dark-field mammography is capable of outperforming conventional mammographic imaging of tumour features in both calcified and non-calcified tumours. Presuming dose optimization, our results encourage further studies on larger patient cohorts to identify those patients that will benefit the most from this promising additional imaging modality.

Key points: • X-ray dark-field mammography provides significantly improved visualization of tumour features • X-ray dark-field mammography is capable of outperforming conventional mammographic imaging • X-ray dark-field mammography provides imaging sensitivity towards highly dispersed calcium grains.

Keywords: Breast cancer; Grating interferometry; Mammography; X-ray dark-field imaging; X-ray phase-contrast imaging.

Fig. 1

Dark-field mammography reveals radiographically undetectable tumour nodules. Clinical ex vivo mammography in craniocaudal (cc) projection at 31 kVp, 45 mAs and 0.56 mGy average glandular dose (silver filter) (a), experimental absorption-contrast mammography (abs-Mx, b), phase-contrast mammography (PC-Mx, c) and dark-field mammography (DF-Mx, d) of patient 1 at 40 kVp, 70 mA and 66 mGy mean glandular dose (per scan direction); representative section from the in vivo MRI (e) including contrast-enhanced T1 weighted gradient-echo sequence after manual injection of 0.2 ml/kg meglumine gadopentetate (Magnograf ® 0.5 mmol/ml) (e, left) and the corresponding first subtraction image after 2 min (e, right) in an axial view using a dedicated sensitivity-encoding-enabled bilateral breast coil with a 3.0-Tesla system (voxel size 0.7 × 0.7 × 2.0 mm), field of view 360 mm; base resolution 512; flip angle 15°; repetition time 6.5 ms; echo time 2.47 ms. Ultrasound (f); vertical line plots quantifying superior depiction of tumor (TU) 1, 2 and 3 in DF-Mx (g, bottom) in comparison with abs-Mx (g, top) as indicated by arrows; in vivo mammography of patient 1 in cc projection at 29 kVp, 11 mAs and 0.41 mGy average glandular dose (aluminium filter) (h); exemplary histological image (haematoxylin–eosin staining) of one calcified tumour nodule (i and j), arrows indicating microcalcifications. The rectangles in a–d and h indicate TU 1–3. The crossed arrows in b–d indicate bidirectional measurements

Fig. 2

Dark-field mammography reveals pervasion of breast with partially tumorous soft-tissue strands. Clinical ex vivo mammography in craniocaudal (cc) projection at 29 kVp, 120 mAs and 1.22 mGy average glandular dose (rhodium filter) (a), experimental absorption-contrast mammography (b), phase-contrast mammography (c) and dark-field mammography (d) at 40 kVp, 70 mA and 66 mGy mean glandular dose (per scan direction); in vivo mammography in cc projection at 29 kVp, 105 mAs and1.27 mGy average glandular dose (rhodium filter) (e) of patient 2 in craniocaudal projection; blue rectangles in a and e indicate the trifocal carcinoma; white rectangles in a–e indicate partially infiltrated tissue strands emerging from the tumour; exemplary histological image (haematoxylin–eosin staining) of partially tumour-infiltrated tissue strands (f) and (g) indicated by arrows. The arrows in b–d indicate one-directional measurements

Fig. 3

Phase-contrast and dark-field mammography reveal tumour margins. Clinical ex vivo mammography in craniocaudal (cc) projection at 27 kVp, 120 mAs and 1.18 mGy average glandular dose (rhodium filter) (a), experimental absorption-contrast mammography (b), phase-contrast mammography (c) and dark-field mammography (d) at 40 kVp, 70 mA and 70 mGy mean glandular dose (per scan direction); in vivo mammography in cc projection at 29 kVp, 125 mAs and 1.26 mGy average glandular dose (rhodium filter) (e) of patient 3 in craniocaudal projection; white rectangle indicating tumour 1; ultrasound of tumour 1 (f); histological image (haematoxylin–eosin staining) of tumour 1 (g); the posterior margin of tumour 1 is indicated by black arrows in c, d and g. The crossed arrows in b–d indicate bidirectional measurements

Fig. 4

Comparison of low- and high-dose dark-field mammography. Low-dose (22 mGy mean glandular dose) dark-field mammography of patient 1 conducted in one scan direction and 3 s exposure time per phase step (a) and corresponding high-dose measurements (66 mGy mean glandular dose per scan direction) conducted in two scan directions and 9 s exposure time per phase step (b) at 40 kVp/70 mA, respectively. Both images offer equal quality in the detection of the tumour nodules