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Feasibility of Single Voxel Proton Spectroscopy of Pineal Gland at 7T
Ravi Prakash Reddy Nanga1, Deepa Thakuri1, Sanjeev Chawla1, Dushyant Kumar1, Abigail T. J. Cember1, Hari Hariharan1, Cynthia Neill Epperson2, and Ravinder Reddy1

1Radiology, University of Pennsylvania, Philadelphia, PA, United States, 2Psychiatry, University of Colorado, Aurora, CO, United States

Synopsis

Taurine is an important metabolite present in the pineal gland and is involved in the regulation of melatonin, which is plays a key role in regulation of sleep-wake cycle, in endocrine metabolism and in depression. However, there have been no known in vivo studies that measured neuro-metabolites in the pineal gland. In this study, for the first time, we explored the feasibility of single voxel proton spectroscopy from pineal gland in vivo in healthy human volunteers at 7.0T MRI.

Introduction

Human pineal gland is a pea-sized gland located in the middle of the brain between two hemispheres, where the thalamus from two lobes join and is also known as the third eye (1). It is the major site for the indoleamine metabolism with the melatonin hormone primarily synthesized in this gland (2-8). Melatonin hormone is mainly involved in the sleep-wake regulation cycle also known as circadian rhythm, as well as in seasonal cycle (9-11). Pineal gland also regulates some of the endocrine hormones (apart from melatonin) involved in the sexual activity and also reproductive system in women (12,13). Biochemical analyses from 15 human pineal glands obtained post-mortem from patients aged 45-89 years old reveals a high concentration of taurine in this gland, which is also involved in the regulation of melatonin synthesis (14,15). However, spectroscopy studies localized on pineal gland in vivo in humans are limited owing due to its smaller anatomy (5-9 mm in length, 1-5mm in width and 3-5 mm in thickness) and signal to noise issues at low field strength MRI scanners. We explored the feasibility of single voxel spectroscopy localized on pineal gland at 7.0T using 32 channel RF coil and the preliminary results are presented in this study.

Methods

Three healthy volunteers aged 25(F), 38(M) and 68(M) years, participated in this IRB approved study. Single voxel proton spectroscopy of pineal gland (as shown in Figure 1) was acquired on each volunteer post noon using a 7.0T Siemens scanner with a 32-Channel phased-array head coil. In addition one of the volunteer had two additional spectroscopy scans from pineal gland acquired (one at 10am and the other at 6pm) to check the variability in taurine concentration based on the time of the scan. To get the identical spectroscopy voxel for the volunteer for the latter two scans, imscribe software (16) was used as shown in Figure 2. For 1H MRS, the parameters were: voxel size:5x5x5 mm3; TR:3000ms; TE:23ms; dummy scans:4; number of averages for water reference/water suppressed spectra:8/512. Total acquisition time for the spectroscopy was ~27min. Spectra obtained were processed using the LC Model software (17).

Results & Discussions

Representative spectrum from pineal gland of the volunteer is shown in Figure 3 with taurine peak represented at ~3.4 ppm. Mean absolute concentration of taurine from the LC model processed spectra was 3.74 +/- 1.2 mM (range 2.52-4.91 mM). For one of the volunteer the taurine concentrations obtained in the morning, post noon and in the evening (10:00am; 2.00pm and 6.00pm) were 3.91, 3.78 and 4.78 mM, respectively. While these preliminary results show the feasibility of single voxel spectroscopy on pineal gland, additional data from more volunteers and also the reproducibility of the measurements of taurine at the same time of the day needs to be established.

Summary

This preliminary study demonstrates for the first time the feasibility of singe voxel spectroscopy localized on pineal gland.

Acknowledgements

This project was supported by the National Institute of Biomedical Imaging and Bioengineering of the National Institute of Health under award number p41EB015893 and the National Institute of Drug Abuse of the National Institutes of Health under award number R01DA037289.

References

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16. Wolf DH, Satterhwaite TD, Loughead J, Pinkham A, Overton E, Elliott MA, Dent GW, Smith MA, Gur RC, Gur RE. (2011) Amygdala abnormalities in first-degree relatives of individuals with schizophrenia unmasked by benzodiazepine challenge. Psychopharmacology 218, 503-512.

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Figures

Figure 1: Anatomical location and the position of the spectroscopy voxel localized on pineal gland (inset) are shown on the T1-weighted image.

Figure 2: Snap-shot of the “Imscribe” software showing the co-registration process of the template and target T1-weighted images along with the new voxel information on the pineal gland in the target space.

Figure 3: One of the representative spectrum acquired from the localized voxel on pineal gland is shown with taurine located at ~3.4ppm.

Proc. Intl. Soc. Mag. Reson. Med. 27 (2019)
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