Toward Clinically Compatible Phase-Contrast Mammography

Abstract

Phase-contrast mammography using laboratory X-ray sources is a promising approach to overcome the relatively low sensitivity and specificity of clinical, absorption-based screening. Current research is mostly centered on identifying potential diagnostic benefits arising from phase-contrast and dark-field mammography and benchmarking the latter with conventional state-of-the-art imaging methods. So far, little effort has been made to adjust this novel imaging technique to clinical needs. In this article, we address the key points for a successful implementation to a clinical routine in the near future and present the very first dose-compatible and rapid scan-time phase-contrast mammograms of both a freshly dissected, cancer-bearing mastectomy specimen and a mammographic accreditation phantom.

Fig 1. Laboratory X-ray phase-contrast mammography setup.

(A) Longitudinal view of the revised, laboratory X-ray phase-contrast mammography setup with a dose-saving arrangement of phase grating and sample holder. A compact system length, rotating X-ray anode and conventional flat panel detector met the design criteria of clinical mammography systems. (B) Close-up view in the direction of the X-ray beam showing the phase-stepping instruments and breast equivalent incorporated for flat-field measurements. The combination of high-load actuator and nano-converter enables image acquisition times within 12 seconds.

Fig 2. Clinically compatible phase-contrast mammograms of a freshly dissected, cancerous mastectomy sample and the mammographic accreditation phantom Gammex 156.

Clinical ex-vivo mammography at 28 kVp, 86 mAs and 0.94 mGy mean glandular dose (Rhodium filter) (A), grating-based absorption (B), differential phase (C) and dark-field mammography (D) at 40 kVp, 70 mA and 2.2 mGy mean glandular dose of a freshly dissected mastectomy sample. Both absorption images are rated equivalent with respect to image quality and detection quality. Inlays show magnified view of the cancerous and micro-calcified tissue volume, with a superior contrast-to-noise ratio in the dark-field (10.6) in comparison to absorption channel (5.7). Notice that soft-tissue components of the tumor are exclusively detected within the dark-field signal, as indicated by the dashed blue line. Clinical mammography at 28 kVp, 159 mAs and 1.62 mGy mean glandular dose (Rhodium filter) (E), grating-based absorption (F), differential phase (G) and dark-field mammography (H) at 40 kVp, 70 mA and 2.07 mGy mean glandular dose of the mammographic accreditation phantom Gammex 156 (Gammex Inc., Middleton). The grating-based absorption image meets the standard criteria of clinical image quality, by resolving 4 of a minimum of 4 fibrils (#1–4), 3 of a minimum of 3 groups of simulated micro-calcifications (#7–9) and 4 of a minimum of 3 tumor masses (#12–15). The differential phase and dark-field channel provide complementary information by revealing an additional 5^th fibril (#5) and 5^th tumor mass (#16) as indicated by arrows.