Tissue Strain Mapping via Magnetic Resonance Elastography Can Be Used to Detect Active Lesion Expansion

PURPOSE: Active lesion expansion is clinically important because it can indicate disease progression and influence management and treatment planning. However, sequential imaging is often unavailable, and rapid growth can only be inferred from indirect findings such as active perilesional tissue injury. This study aimed to implement and test the feasibility of an MR elastography (MRE)-based technique for assessing the expansile nature of mass lesions by detecting stiffness changes caused by mechanical strain manifestations in adjacent tissues. METHODS: A tissue strain mapping (TSM) algorithm was developed using spatial-temporal directional filtering to reveal the presence of perilesional latent strain that is not apparent in conventional MRE inversions. The technical feasibility was tested in tissue-simulating phantoms containing a mass that was progressively expanded. Preliminary feasibility for clinical application was also demonstrated in representative in vivo examples. Resulting TSM maps were compared with conventional MRE stiffness maps. RESULTS: In the phantom experiments, TSM revealed the presence of local strain at the periphery of the expanding mass, with the effect increasing proportionally to the degree of expansion. Conventional MRE did not demonstrate comparable localized stiffening patterns. In vivo examples showed similar perilesional strain features that were not apparent on conventional MRE maps. CONCLUSION: The feasibility of the proposed MRE-based TSM technique was demonstrated in phantom and preliminary in vivo studies. These findings suggest that the technique is a promising tool for assessing the expansile nature of mass lesions and motivate further development of the TSM processing and exploration of potential clinical applications.