# Hybrid Tau-PET/MRI study: Quantitative susceptibility mapping in progressive supranuclear palsy and its correlation with Tau-PET

## TL;DR

This study explores how brain iron levels measured by MRI correlate with tau protein accumulation in patients with progressive supranuclear palsy, a rare Parkinsonian disorder.

## Contribution

The study is the first to assess correlations between QSM and tau-PET data in PSP patients, linking iron susceptibility to tau pathology.

## Key findings

- PSP patients showed higher QSM values in the caudate nucleus and dentate nucleus compared to healthy controls.
- PSP-RS subtype patients had elevated QSM values in the left dentate nucleus.
- A significant positive correlation was found between QSM and tau-PET data in PSP patients.

## Abstract

The atypical Parkinsonian disorder progressive supranuclear palsy (PSP) forms a diagnostic challenge, resulting in frequent misdiagnosis and delay in treatment. Although structural MRI can detect PSP signs at more advanced stages, emerging diagnostic tools such as tau-PET and quantitative susceptibility mapping (QSM) may allow for earlier detection. This exploratory study aimed to investigate differences in QSM data of patients with PSP and healthy controls (HCs) and for the first time assess possible correlations between QSM and tau-PET data in patients with PSP to explore the relationship between tau aggregation and iron susceptibility.

We retrospectively investigated differences in susceptibility values of brain structures, as assessed by QSM, between 11 HCs and 31 patients with PSP [Richardson’s syndrome (PSP-RS): n = 14; other subtypes (PSP-nonRS): n = 17]. Additionally, we examined co-registered [18F]PI-2620 PET and QSM data in the 31 patients with PSP to explore the relationship between tau accumulation and susceptibility changes.

Compared to HCs, patients with PSP showed higher QSM values in left nucleus caudate (p = 0.04) and bilateral dentate nucleus (p = 0.04, p = 0.01). Patients with the subtype PSP-RS showed higher QSM values than HCs in left dentate nucleus (p = 0.02). The association between the patients’ QSM and tau-PET data showed a significant positive correlation.

These results suggest distinct patterns of regional iron accumulation in patients with PSP and its subtypes and support an association between iron and tau pathology. The data encourage further investigation in longitudinal studies and validation in larger cohorts to examine the value of QSM as a possible diagnostic biomarker.

The online version contains supplementary material available at 10.1007/s00259-025-07600-9.