Technical recommendation on multiplex MR elastography for tomographic mapping of abdominal stiffness with a focus on the pancreas and pancreatic ductal adenocarcinoma

TL;DR

This study demonstrates that multiplex MR elastography with multiple drivers and frequencies significantly improves the ability to map tissue stiffness in the abdomen, especially the pancreas, which is challenging with conventional methods.

Contribution

The paper introduces a multiplex MRE technique using multiple drivers and frequencies, enhancing abdominal and pancreatic stiffness mapping over traditional single-driver approaches.

Findings

Multiplex MRE achieves near-complete coverage of abdominal organs.

Coverage in the pancreas exceeds 60% in all healthy subjects.

Patients with PDAC show high coverage, indicating clinical potential.

Abstract

Objectives: MR elastography (MRE) offers valuable mechanical tissue characterization, however, in deep abdominal organs like the pancreas conventional single-driver, single-frequency approaches often fail. This study evaluates whether multiplex MRE using multiple drivers and vibration frequencies can overcome these limitations. Methods: This study used single-shot spin-echo MRE in 18 healthy volunteers targeting the liver, pancreas, kidneys, and spleen. Each healthy volunteer underwent 16 MRE examinations with different sets of four vibration frequencies (30-60 Hz) and four driver combinations, and an additional null experiment without vibrations. Further, a cohort of 14 patients with pancreatic ductal adenocarcinoma (PDAC) were retrospectively assessed. The quality of shear-wave fields and stiffness maps was assessed by displacement amplitudes and image sharpness. Results: In healthy volunteers, abdominal coverage with displacement amplitudes above the pre-determined noise level of 4 {\mu}m varied between MRE configurations: 24.2% ([0.0%-56.2%], single-driver, 60 Hz), 66.9% ([24.8%-97.7%], single-driver, 30-60 Hz), 70.2% ([0.0%-92.5%], multi-driver, 60 Hz) and 99.9% ([89.4%-100%], multi-driver, 30-60 Hz). In the pancreas, >60% coverage was achieved in all subjects using four drivers and multiple frequencies. This was achieved in only 2/18 subjects using single-driver/single-frequency MRE. Patients with PDAC had 99.1% [91.4%-100%] coverage in the pancreas and 96.3% [63.1%-100%] abdominal coverage (multi-driver, 30-60 Hz). Conclusion: MRE with four drivers and multiple vibration frequencies between 30-60 Hz enables tomographic mapping of tissue stiffness across the entire abdomen, including the pancreas. Multiplex MRE offers a promising approach for generating detailed images of abdominal stiffness, potentially enhancing clinical diagnostics for abdominal and pancreatic diseases.