Diffusion-time dependent diffusion MRI: effect of diffusion-time on microstructural mapping and prediction of prognostic features in breast cancer.

OBJECTIVES

This study aimed to evaluate the effect of achievable t on the accuracy of microstructural mapping based on simulation and patient experiments, and investigate the feasibility of t-dMRI in distinguishing prognostic factors in breast cancer patients.

METHODS

Simulation was performed using different t settings. Patients with breast cancer were enrolled prospectively between November 2020 and January 2021, who underwent oscillating and pulsed gradient encoded dMRI on a 3-T scanner using short-/long-t protocol with oscillating frequency up to 50/33 Hz. Data were fitted with a two-compartment model to estimate cell diameter (d), intracellular fraction (f), and diffusivities. Estimated microstructural markers were used to differentiate immunohistochemical receptor status and the presence of lymph node (LN), which were correlated with histopathological measurements.

RESULTS

Simulation results showed that d fitted from the short-t protocol significantly reduced estimation error than those from long-t (2.07 ± 1.51% versus 3.05 ± 1.92%, p < 0.0001) while the estimation error of f was robust to different protocols. Among a total of 37 breast cancer patients, the estimated d was significantly higher in HER2-positive and LN-positive (p < 0.05) groups compared to their negative counterparts only using the short-t protocol. Histopathological validation in a subset of 6 patients with whole slide images showed the estimated d was highly correlated with measurements from H&E staining (r = 0.84, p = 0.03) only using the short-t protocol.

CONCLUSIONS

The results indicated the necessity of short-t for accurate microstructural mapping in breast cancer. The current t-dMRI with a total acquisition time of 4.5 min showed its potential in the diagnosis of breast cancer.

KEY POINTS

• Short t is important for accurate microstructural mapping in breast cancer using the t-dMRI technique, based on simulation and histological validation. • The 4.5-min t-dMRI protocol showed potential clinical value for breast cancer, given the difference in cell diameter between HER2/LN positive and negative groups.