Experimental demonstration of ultrahigh sensitivity Talbot-Lau interferometer for low dose mammography

Abstract

Objective: Even though the techniques used for breast cancer identification have advanced over the years, current mammography based on X-rays absorption, the "gold standard" screening test at present, still has some shortcomings as concerns sensitivity and specificity to early-stage cancers, due to poor differentiation between tumor and normal tissues, especially in the case of the dense breasts. We investigate a possible additional technique for breast cancer detection with higher sensitivity and low dose, X-ray phase-contrast or refraction-based imaging with ultrahigh angular sensitivity grating interferometers, having several meters length. Approach: Towards this goal, we built and tested on a mammography phantom, a table-top laboratory setup based on a 5.7 m long Talbot-Lau interferometer with angular sensitivity better than 1 µrad. We used a high-power X-ray tungsten anode tube with a 400 µm focal spot, operated at 40 kVp and 15 mA with a 2 mm aluminum filter. Main results: The results reported in our paper confirm the ultrahigh sensitivity and dose economy possible with our setup. The visibility of objects simulating cancerous formations is strongly increased in the refraction images over the attenuation ones, even at a low dose of 0.32 mGy. Notably, the smallest fiber of 400 µm diameter and calcifications specs of 160 µm in diameter are detected, even though the spatial resolution at the object of our magnification M~2 setup with a 400 µm source spot is only ~250 µm. Significance: Our experiments on a mammography phantom illustrate the capabilities of the proposed technique and can open the way toward low-dose interferometric mammography.

Towards high-sensitivity and low-dose medical imaging with laser x-ray sources

“…The broad synchrotron-like spectrum of the laser sources matches the broad spectral acceptance of high angular sensitivity interferometers, as shown by our experimental results and simulations ( [16] and Fig. 6).…”

“…At the same time, in the absorption images the fiber is faintly visible only at high dose, becoming invisible at low dose. The phase images of tumoral masses and of calcifications in the Gammex phantom also show much improved contrast compared to the absorption images [16].…”

“…A first key question is thus whether µm period, multi-meter length interferometers can have sufficient fringe visibility for high sensitivity and low dose phase contrast imaging. Our recent experiments at ELI-NP show that the answer is positive [16]. Thus, we built and studied the performance of symmetric interferometers with the smallest grating period commercially available G=2.4 µm, manufactured by Microworks GmbH, Germany [17], and with lengths in the 4-6 m range.…”

“…The fringe visibility is high and nearly constant up to ~6 m, beginning to mildly oscillate with distance after this value. The explanation for this useful effect is the spectral and spatial overlap of the interference patterns from many Talbot orders [14,16]. The simultaneous high angular sensitivity and fringe visibility of the 5.7 m interferometer enabled us to image medically relevant objects with reduced dose.…”

“…Operation at higher X-ray energy is highly desirable because the kinetic energy released in soft tissue has a steep decrease with photon energy till ~50 keV [19]. The radiation dose, evaluated as described in [16], decreases from ~5 mGy to ~0.5 mGy. For comparison, the typical radiation dose in mammography is ~2 mGy.…”