Objectives

Proposes a single-day protocol for DaT-SPECT, cardiac MIBG scintigraphy, and FDG-PET to facilitate biomarker assessments for Parkinsonian syndromes.
Demonstrates the feasibility of the protocol by showing no relevant interference between tracers, maintaining image quality, and allowing quantitative analysis.
Suggests that the protocol aligns with the SyNeurGe biological classification of Parkinson's disease.

Methodology

Used standard protocols for MIBG scintigraphy and DaT-SPECT.
Performed cardiac imaging 3.5 hours after simultaneous injection of [123I]ioflupane and [123I]MIBG, followed by brain imaging at 4 hours.
Five patients also received FDG-PET brain scans after DaT and MIBG imaging.
Analyzed DaT-SPECT scans using Hermes BRASS and GE DaTQuant.
Obtained heart-to-mediastinum ratios (H/M-ratio) for MIBG scans.
Analyzed FDG-PET scans using 3D stereotactic surface projections (3DSSP).

Single tracer imaging confirmed no relevant uptake of [123I]ioflupane in the heart (mean SUV: 0.91 ± 0.07, H/M-ratio: 0.92 ± 0.10) or [123I]MIBG in the brain (mean SUV: 0.15 ± 0.06).
In the dual tracer group (n=10), 6 patients showed reduced DaT-SPECT binding (mean putaminal z-score: -4.01 ± 1.39), and 7 patients had a pathological H/M-ratio (mean: 1.12 ± 0.08).
No significant differences in SUV values were found between dual and single tracer acquisitions.
Strong correlation between SBR and z-scores from Hermes BRASS and GE DaTQuant (R2 > 0.76, p < 0.0001 for all comparisons).
FDG-PET scans in the triple tracer group (n=5) showed no interference.

The study is limited by a small sample size (n=10 for dual-tracer, n=5 for triple-tracer), which restricts the generalizability of the findings.
The study uses a cohort of patients with clinically suspected α-synucleinopathies, introducing potential selection bias.
While the study addresses potential interference, further investigation with larger sample sizes is needed to validate if adjustments to the H/M-ratio threshold are necessary.
The study could benefit from exploring variations of the protocol, such as starting with Iofupane SPECT at 3 hours post-injection, followed by the MIBG scan.