Abstract
Abstract
Objective
To characterize MRI matrix signal and CT calcification patterns across WHO-IWGE stages, compare them with lesion mimicking cystic echinococcosis (CE), and derive an MRI-based subclassification for inactive cysts.
Materials and methods
This retrospective multicenter study included 105 patients (174 CE cysts) imaged between 2012 and 2024, plus 30 mimickers. Inclusion required axial T1-weighted imaging with chemical-shift in-phase/opposed-phase acquisitions and at least two T2-weighted sequences. Two radiologists independently reviewed all examinations, and a consensus was reached. Cysts were classified as inactive if no free-fluid T2 hypersignal was present on index MRI and corroborated by follow-up imaging and/or adjunct ultrasound in equivocal cases. Diagnostic performance indices were calculated to identify inactivity.
Results
Fatty T1 hyperintensity was more frequent in inactive than active/transitional cysts (20/97 (21%) vs 2/77 (3%);
p
p
p
p
= 0.006). Homogeneous non-fatty T1 hyperintensity characterized mimickers (23/30 (77%) vs 10/174 (6%);
p
Conclusion
Matrix MRI/CT features—particularly fatty foci and the matrix flip-flop sign—provide ancillary evidence of CE inactivity and help distinguish CE from mimickers. T2 signal supported an MRI-based framework for stage-adapted “watch-and-wait” follow-up.
Key Points
Question
MRI features of cystic echinococcosis remain insufficiently studied, particularly matrix signal abnormalities that may affect diagnosis and viability assessment on routine imaging.
Findings
T1- and T2-weighted matrix CE cysts analysis identified fatty foci and the newly described matrix flip-flop sign as specific features of inactive cysts.
Critical Relevance
Assessment of underrecognized MRI and CT cyst-matrix features can help stage cystic echinococcosis, assess viability, and distinguish cystic echinococcosis cysts from mimickers.