Hybrid Amyloid PET/3T Quantitative Susceptibility Mapping MRI in Dementia Patients and Healthy Controls

Ziel/Aim:

Post-mortem and in-vivo MRI data from several groups suggest an accumulation of iron in relation to beta-amyloid (Aß) plaques in the brains of patients with Alzheimer's disease (AD). The majority of stand-alone MRI studies in patients with clinical diagnosis of AD found an increase of iron-sensitive quantitative susceptibility mapping (QSM) signals in deeper brain structures. The aim of this exploratory study was to examine whether these results translate to simultaneously acquired hybrid amyloid PET/3T MRI.

Methodik/Methods:

We retrospectively analyzed the C-11-PiB PET/QSM MRI data of 11 HCs (7 female;, 65 ± 3yrs) as well as those of 16 Aβ-positive (12 female, 69 ± 9yrs)/10 Aβ-negative (6 female 73 ± 8yrs), dementia patients. The data were analyzed regionally using the AAL template (PMOD). Outcome measures for the PET data were regional SUVRs taking the cerebellar cortex as reference region, and regional QSM values for the MRI data.

Ergebnisse/Results:

The Aβ-positive patients showed higher QSM values in putamen compared to the HCs (0.049 ± 0.033 vs. 0.002 ± 0.031; p = 0.006), while the Aβ-negative patients showed lower QSM values in the caudate head compared to the HCs (0.003 ± 0.027 vs. 0.051 ± 0.039; p = 0.006). The regional QSM values were not correlated to the MMSE scores, neither in the Aβ-positive, nor in the -negative patient group. In the Aβ-positive patients, however, the composite [¹¹C]PiB SUVRs were significantly correlated with the putaminal QSM values (ρ=-0.602, p = 0.014).

Schlussfolgerungen/Conclusions:

Compared to the HCs, patients with amyloid biomarker-supported AD showed significantly higher QSM values in the putamen, and non-AD patients significantly lower QSM values in the caudate nucleus. These data indicate that QSM on hybrid PET/3T MRI has potential in determining the difference in iron content in disease specific brain regions and with relation to the pathophysiological process in Aβ load. The results encourage further investigations of larger patient cohorts.