Binding characteristics of [18F]PI-2620 distinguish the clinically predicted tau isoform in different tauopathies by PET

The novel tau-PET tracer [¹⁸F]PI-2620 detects the 3/4-repeat-(R)-tauopathy Alzheimer's disease (AD) and the 4R-tauopathies corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP). We determined whether [¹⁸F]PI-2620 binding characteristics deriving from non-invasive reference tissue modelling differentiate 3/4R- and 4R-tauopathies. Ten patients with a 3/4R tauopathy (AD continuum) and 29 patients with a 4R tauopathy (CBS, PSP) were evaluated. [¹⁸F]PI-2620 PET scans were acquired 0-60 min p.i. and the distribution volume ratio (DVR) was calculated. [¹⁸F]PI-2620-positive clusters (DVR ≥ 2.5 SD vs. 11 healthy controls) were evaluated by non-invasive kinetic modelling. R1 (delivery), k2 & k2a (efflux), DVR, 30-60 min standardized-uptake-value-ratios (SUVR_30-60) and the linear slope of post-perfusion phase SUVR (9-60 min p.i.) were compared between 3/4R- and 4R-tauopathies. Cortical clusters of 4R-tau cases indicated higher delivery (R1_SRTM: 0.92 ± 0.21 vs. 0.83 ± 0.10, p = 0.0007), higher efflux (k2_SRTM: 0.17/min ±0.21/min vs. 0.06/min ± 0.07/min, p < 0.0001), lower DVR (1.1 ± 0.1 vs. 1.4 ± 0.2, p < 0.0001), lower SUVR_30-60 (1.3 ± 0.2 vs. 1.8 ± 0.3, p < 0.0001) and flatter slopes of the post-perfusion phase (slope_9-60: 0.006/min ± 0.007/min vs. 0.016/min ± 0.008/min, p < 0.0001) when compared to 3/4R-tau cases. [¹⁸F]PI-2620 binding characteristics in cortical regions differentiate 3/4R- and 4R-tauopathies. Higher tracer clearance indicates less stable binding in 4R tauopathies when compared to 3/4R-tauopathies.

One-Stop Shop: 18F-Flortaucipir PET Differentiates Amyloid-Positive and -Negative Forms of Neurodegenerative Diseases

Tau protein aggregations are a hallmark of amyloid-associated Alzheimer disease and some forms of non-amyloid-associated frontotemporal lobar degeneration. In recent years, several tracers for in vivo tau imaging have been under evaluation. This study investigated the ability of ¹⁸F-flortaucipir PET not only to assess tau positivity but also to differentiate between amyloid-positive and -negative forms of neurodegeneration on the basis of different ¹⁸F-flortaucipir PET signatures. Methods: The ¹⁸F-flortaucipir PET data of 35 patients with amyloid-positive neurodegeneration, 19 patients with amyloid-negative neurodegeneration, and 17 healthy controls were included in a data-driven scaled subprofile model (SSM)/principal-component analysis (PCA) identifying spatial covariance patterns. SSM/PCA pattern expression strengths were tested for their ability to predict amyloid status in a receiver-operating-characteristic analysis and validated with a leave-one-out approach. Results: Pattern expression strengths predicted amyloid status with a sensitivity of 0.94 and a specificity of 0.83. A support vector machine classification based on pattern expression strengths in 2 different SSM/PCA components yielded a prediction accuracy of 98%. Anatomically, prediction performance was driven by parietooccipital gray matter in amyloid-positive patients versus predominant white matter binding in amyloid-negative patients. Conclusion: SSM/PCA-derived binding patterns of ¹⁸F-flortaucipir differentiate between amyloid-positive and -negative neurodegenerative diseases with high accuracy. ¹⁸F-flortaucipir PET alone may convey additional information equivalent to that from amyloid PET. Together with a perfusion-weighted early-phase acquisition (¹⁸F-FDG PET-equivalent), a single scan potentially contains comprehensive information on amyloid (A), tau (T), and neurodegeneration (N) status as required by recent biomarker classification algorithms (A/T/N).

Clinical Outcome After Mechanical Thrombectomy in Patients with Diabetes with Major Ischemic Stroke of the Anterior Circulation

BACKGROUND

Among patients with acute ischemic stroke treated with mechanical thrombectomy (MT), patients with diabetes (DP) show a poorer outcome compared with patients without diabetes (NDP). This study aims to provide a comprehensive analysis of factors associated with unfavorable outcome in DP receiving MT for stroke of the anterior circulation.

METHODS

This study included 317 of 498 consecutive patients who received interventional treatment for acute ischemic stroke in the terminal internal carotid artery and/or middle cerebral artery, including 46 DP. The study data included pre- and posttreatment stroke computed tomography, including perfusion data, collateral status, treatment data including treatment times, pre-existing cardiovascular risk factors, cerebrovascular events, comorbidities, laboratory parameters, and medication. Neurologic status was assessed at baseline (National Institute of Health Stroke Scale [NIHSS]/modified Rankin Scale [mRS]) and after 90 days (mRS 90).

RESULTS

Compared with NDP, DP showed a significantly poorer outcome (mRS90 >2) (P < 0.05). Collateralization and infarct core size did not differ between groups, whereas the penumbra was significantly smaller in DP than in NDP (P < 0.05). The poorer mRS90 outcome (mRS90 > 2) in DP was associated with poor collaterals (P = 0.01) and hyperglycemia on admission (P < 0.05). Shorter time to reperfusion was associated with favorable mRS90 in the NDP (P < 0.001) but not the DP (P = 0.49) group. In univariate logistic regression, the following parameters were significantly associated with mRS90: diabetes, hyperglycemia at admission, time to reperfusion, and the NIHSS score (P < 0.05 each). In multivariate analyses and partition regression models of all variables, DP with admission hyperglycemia (≥132 mg/dL) and older age (≥66 years) showed a particularly poor outcome.

CONCLUSIONS

The main factors for an unfavorable outcome of DP after MT are admission hyperglycemia, age, and NIHSS score.