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SWI and T2*-GRE Microhemorrhage Counts in Anti-Amyloid Therapy Eligibility: A Real-World-Calibrated Simulation Study
Kenichiro Sato1,2, Ryoko Ihara2,3, Masanori Kurihara3,4
1Dementia Inclusion and Therapeutics, The University of Tokyo Hospital.
Introduction:
Anti-amyloid therapy eligibility excludes patients with five or more cerebral microhemorrhages (CMHs), but current guidance allows either T2*-GRE or the more sensitive SWI. This may create sequence-dependent differences in eligibility classification.
Methods:
We fitted a Bayesian right-censored zero-inflated Poisson model to single-center real-world SWI-based CMH counts from 130 memory clinic patients. We then simulated T2*-GRE counts under a directional binomial detection model across a range of relative detection probabilities and estimated two metrics: P(T2* <5 | SWI ≥5) and P(SWI ≥5 | T2* <5).
Results:
The model estimated a zero-inflation probability of 0.57 and a Poisson mean of 2.29 in the susceptible subpopulation. In the illustrative 60% relative-detection scenario, the model estimated nearly 80% under-detection among SWI-ineligible patients, whereas approximately 5% of T2*-GRE-eligible patients would have been classified as ineligible by SWI.
Discussion:
A uniform numeric CMH threshold may not be operationally equivalent across SWI and T2*-GRE. Standardized paired-sequence outcome studies are needed to determine whether SWI-defined and T2*-GRE-defined thresholds carry equivalent ARIA risk.
Insights
Magnetic resonance imaging sequences for anti-amyloid therapy eligibility may yield different results. Cerebral microhemorrhage (CMH) counts vary between SWI and T2*-GRE, impacting patient eligibility for treatment.
Area of Science:
- Neuroimaging
- Neurology
- Medical Imaging Analysis
Background:
- Patient eligibility for anti-amyloid therapies is limited by the presence of five or more cerebral microhemorrhages (CMHs).
- Current guidelines permit the use of either T2*-GRE or the more sensitive SWI sequence for CMH assessment.
- This discrepancy may lead to sequence-dependent variations in patient eligibility classification.
Purpose of the Study:
- To investigate the impact of different MRI sequences (SWI vs. T2*-GRE) on cerebral microhemorrhage (CMH) detection.
- To quantify the potential discrepancies in patient eligibility for anti-amyloid therapies based on CMH counts derived from SWI and T2*-GRE sequences.
- To evaluate the operational equivalence of CMH thresholds across SWI and T2*-GRE sequences.
Main Methods:
- A Bayesian right-censored zero-inflated Poisson model was fitted to real-world SWI-based CMH counts from 130 memory clinic patients.
- Simulations of T2*-GRE counts were performed using a directional binomial detection model.
- Key metrics P(T2* <5 | SWI ≥ 5) and P(SWI ≥ 5 | T2* <5) were estimated to assess eligibility discrepancies.
Main Results:
- The model indicated a zero-inflation probability of 0.57 and a Poisson mean of 2.29 in the susceptible subpopulation.
- In a scenario with 60% relative detection probability, nearly 80% of patients ineligible by SWI criteria were under-detected by T2*-GRE.
- Approximately 5% of patients eligible by T2*-GRE criteria would have been classified as ineligible by SWI.
Conclusions:
- A uniform numerical CMH threshold may not be operationally equivalent when using SWI and T2*-GRE sequences.
- Standardized studies comparing paired SWI and T2*-GRE sequences are necessary.
- Further research is needed to determine if SWI-defined and T2*-GRE-defined CMH thresholds correlate with equivalent ARIA risk.
