Transverse relaxation‐based assessment of mammographic density and breast tissue composition by single‐sided portable NMR

Abstract

Purpose: Elevated mammographic density (MD) is an independent risk factor for breast cancer (BC) as well as a source of masking in X-ray mammography.High-frequency longitudinal monitoring of MD could also be beneficial in hormonal BC prevention, where early MD changes herald the treatment's success. We present a novel approach to quantification of MD in breast tissue using single-sided portable NMR. Its development was motivated by the low cost of portable-NMR instrumentation, the suitability for measurements in vivo, and the absence of ionizing radiation. Methods: Five breast slices were obtained from three patients undergoing prophylactic mastectomy or breast reduction surgery. Carr-Purcell-Meiboom-Gill (CPMG) relaxation curves were measured from (1) regions of high and low MD (HMD and LMD, respectively) in the full breast slices; (2) the same regions excised from the full slices; and (3) excised samples after H 2 O-D 2 O replacement. T 2 distributions were reconstructed from the CPMG decays using inverse Laplace transform. Results: Two major peaks, identified as fat and water, were consistently observed in the T 2 distributions of HMD regions. The LMD T 2 distributions were dominated by the fat peak. The relative areas of the two peaks exhibited statistically significant (P < .005) differences between HMD and LMD regions, enabling their classification as HMD or LMD. The relative-area distributions exhibited no statistically significant differences between full slices and excised samples. Conclusion: T 2 -based portable-NMR analysis is a novel approach to MD quantification. The ability to quantify tissue composition, combined with the low cost of instrumentation, make this approach promising for clinical applications. 1200 | ALI et AL. K E Y W O R D S breast cancer, mammographic density, NMR-MOUSE, nuclear magnetic resonance, single-sided portable NMR, transverse spin relaxation time constant (T 2 )

Quantification of breast tissue density: Correlation between single-sided portable NMR and micro-CT measurements

“…We have previously shown that a commercially available portable-NMR instrument, NMR-Mouse, enables discrimination between regions of high and low MD (HMD and LMD, respectively) via longitudinal spin-relaxation rate constants, T1, [12,13] and the relative amplitudes of fat and water peaks in T2 spectra [12,13]. However, there are notable limitations to those studies (summarised in Table 1), the most important of which is the binary nature of the HMD/LMD classification: the mammographic images used in those studies as a MD "gold standard" were used only to identify "HMD regions" and "LMD regions" within the samples and were not used to assess breast density as a continuous entity.…”

“…NMR-measured quantities T1 [12] and the relative area of the water T2 peak [13]. BI-RADS density scores were estimated from the pre-surgery mammogram.…”

“…(Magritek, Wellington, New Zealand), a single-sided NMR scanner using a permanent magnet with a horizontal magnetic field B0 = 0.31 T and a vertical permanent magnetic field gradient g = 7.5 T/m [12,13,15,16]. A surface coil was used to excite and detect the NMR signal.…”

Heparanase promotes Syndecan-1 expression to mediate fibrillar collagen and mammographic density in human breast tissue culturedex vivo

“…The curves were least-squares fitted with a three-parameter exponential fitting function, and the time constants of the recovery were taken as the respective T1 values. For SSTN treated explants, % water was measured using two approaches: (1) Carr-Purcell-Meiboom-Gill (CPMG) decay followed by an inverse Laplace transform, as described in (Ali, Tourell et al 2019). This approach yielded T2 relaxation spectra with two peaks (Fat and Water), whose relative areas were taken as the content of the respective chemical component within the tissue;…”

NMR CAPIBarA: Proof of Principle of a Low-Field Unilateral Magnetic Resonance System for Monitoring of the Placenta during Pregnancy

“…The NMR-MoUSE has been a commercial product for nearly two decades and has evolved into a suite of instruments offering different distances of sensitive regions above the surface from 2 mm with 5 µM resolution for the PM2 up to 25 mm away with 100 µM resolution for the PM25 [10]. Medical applications of this unilateral system have been appearing in the literature, including profiling of human skin [11], articular cartilage [12], bone volume-to-total volume ratio [13], T 1 -based mammographic density [14] and T 2 -based mammographic density [15].…”