Objective: To evaluate if the T1 value (measured in ms) in the substantia nigra (SN) is reduced in Parkinson disease (PD) patients as compared with healthy controls (HC).

Background: The death of dopaminergic neurons in the substantia nigra (SN) pars compacta is the pathological hallmark of Parkinson disease. Although numerous imaging techniques have been used to evaluate PD, most of them are based in Magnetic Resonance (MR) qualitative images rather than quantitative MR images. Qualitative MR are very sensitive of acquisition parameters and the way of the analysis is performed. We propose to study this anatomical region using quantitative T1 maps that estimate the spin relaxation time for each pixels which could be related with the integrity of the tissue.

Methods: PD patients diagnosed according to the London brain Bank criteria were included. Exclusion criteria were atypical Parkinsonism, dementia or use of dopamine blockers in the last six months. Patients were scanned in a 1.5T Achieva Philips scan and a T1 mapping was performed using a sequence that employs two non­selective inversion pulses with inversion times ranging from 20ms to 2000ms, followed by eight segmented readouts for eight individual images. T1 values were computed on a pixel ­by ­pixel basis using an in-­house software (Matlab, Natick, MA). Healthy volunteers were scanned as controls.

Results: Ten PD patients and 10 HC were included. T1 maps showed a different pattern between PD and healthy controls. The average T1 relaxation time of the whole SN between healthy controls and PD was significantly different. No differences were found in PD patients in the SN between more and less affected sides. Segmental analysis showed that the anterior third of the SN did not have difference in the T1 values compared with healthy volunteers. However the middle and posterior section showed significant differences between healthy volunteers and PD patients.

Conclusions: T1 map is a quantitative technique that could provide new information for the diagnosis and follow ­up of PD patients. Additionally its quantitative properties could allow to compare the results between patient and to track the evolution of patients in a quantitative and objective way. Larger and longer prospective studies are needed to confirm these findings. CJ is supported by FONDECYT 11130534. Presented in SFN 2017

References: [1] Mackenzie, BCMJ 2001. [2] Hutchinson, PLoS ONE 2014.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/substantia-nigra-t1-maps-for-the-diagnosis-of-parkinsons-disease/