Ultra high-field SWI of the substantia nigra at 7T: reliability and consistency of the swallow-tail sign

Abstract

BackgroundThe loss of the swallow-tail sign of the substantia nigra has been proposed for diagnosis of Parkinson’s disease. Aim was to evaluate, if the sign occurs consistently in healthy subjects and if it can be reliably detected with high-resolution 7T susceptibility weighted imaging (SWI).MethodsThirteen healthy adults received SWI at 7T. 3 neuroradiologists, who were blinded to patients’ diagnosis, independently classified subjects regarding the swallow-tail sign to be present or absent. Accuracy, positive and negative predictive values (PPV and NPV) as well as inter- and intra-rater reliability and internal consistency were analyzed.ResultsThe sign could be detected in 81% of the cases in consensus reading. Accuracy to detect the sign compared to the consensus was 100, 77 and 96% for the three readers with PPV reader 1/2/3 = 1/0.45/0.83 and NPV = 1/1/1. Inter-rater reliability was excellent (inter-class correlation coefficient = 0.844, alpha = 0.871). Intra-rater reliability was good to excellent (reader 1 R/L = 0.625/0.786; reader 2 = 0.7/0.64; reader 3 = 0.9/1).ConclusionThe swallow-tail sign can be reliably detected. However, our data suggest its occurrence is not consistent in healthy subjects. It may be possible that one reason is an individually variable molecular organization of nigrosome 1 so that it does not return a uniform signal in SWI.

Susceptibility‐Weighted 3T MRI of the Swallow Tail Sign in Multiple Sclerosis: A Case Control Study

“…In line with previous studies, 1,2 we found an abnormal swallow tail sign in 17% of control patients, a finding that has been attributed to limited spatial resolution and lower signal-to-noise and contrast-to-noise ratios that are achievable at 3T MRI systems in reasonable scan time. 2 Finally, our cohort included only patients in the relapsing phase of the disease, whereas primary progressive and secondary progressive MS patients were not included. Future longitudinal studies, including more patients and different phases of the disease, may consolidate our findings.…”

Microvessels may Confound the “Swallow Tail Sign” in Normal Aged Midbrains: A Postmortem 7 T SW‐MRI Study

“…3 In their recent ultrahigh-field study on the reliability of the "swallow tail sign," Schmidt et al hypothesized that its inconsistent occurrence may, to a certain extent, be due to a variable molecular organization of nigrosome 1. 22 In the pathogenesis of PD, a decrease of neuromelanin-containing dopaminergic neurons and varying iron loads on neuromelanin are considered important factors. Therefore, transverse MR relaxometry may be an additional tool for the separate evaluation of neuromelanin and iron distributions with the progression of PD.…”

3D variable‐density SPARKLING trajectories for high‐resolution T2*‐weighted magnetic resonance imaging

“…Finally, a high resolution of 0.3 mm in the axial plane with a slice thickness of 1.5 mm was performed, similar to the protocols presented in the literature [23], [25], [32]. Here, the Cartesian reference was an iPAT 2 (24 references lines) with Partial Fourier 6/8 (phase and encode).…”