Magnetic Resonance Spectroscopy (MRS) is a powerful technique used to study the metabolism of the brain, providing insights into the molecular changes that occur during neurodegenerative diseases and psychiatric disorders. However, MRS requires non-invasive tracers that can be detected by the magnetic resonance imager. The use of radioactive tracers poses limitations in terms of safety and availability. In this context, α-D-Glucose emerges as a promising alternative – a non-radioactive MRS tracer that can accurately map the metabolic activity of the brain. In this article, we will review the properties of α-D-Glucose, its application in MRS, and its potential to improve our understanding of brain metabolism.
The methods used in this study were conducted according to relevant guidelines and regulations. The researchers simulated the spectra of α-d-glucose and β-d-glucose by solving a relaxation-free Liouville-von Neumann equation using in-house MATLAB (R2019b) code. They used a crystalline, water-free, α-D-glucose supplied by Thermo Fisher Scientific, Inc. for in vitro phantom measurements, which were dissolved in 500 ml water and filled into a spherical phantom. The first SLOW measurement was performed approximately 10 minutes after dissolving the glucose. For in vivo measurements, non-equilibrium α-D-glucose solution was obtained by dissolving 70 g in 500 ml tap water and administered orally during approximately 6 minutes. The equilibrium α/β-D-glucose solution was prepared by dissolving 70 g α-D-glucose in 500 ml tap water 650 minutes before the start of the in vivo measurements.
All MRI and MRSI acquisitions were performed on a Siemens 7T MR scanner in clinical mode using the Nova 1Tx 32Rx head coil. The single-shot SLOW-editing sequence was used for all spectroscopic recordings. The bandwidth of single-shot editing ranges from 5.0–7.4 ppm. In vitro phantom measurements were performed on a fresh pure α-D-glucose solution to evaluate the mutarotation process towards reaching the α/β-D-glucose equilibrium in vitro. A series of time interleaved measurements were made on the initial pure α-D-glucose solution. For in vivo measurements, the CSAP pulse duration for α-D-glucose detection was 30 ms and 20 ms for different measurements.
The researchers used two healthy male volunteers, one 30 years old and weighing 45 kg, and the other 57 years old and weighing 90 kg, for the in vivo measurements. The quantification of α-D-glucose was calculated using peak integration of 5.22 ppm and compared to the peak integration of the internal acquired water signal at 4.65 ppm. The data reconstruction and pre-post-processing were performed using the Metabolic Imaging Data Analysis System (MIDAS) and MATLAB R2019b.
All experimental protocols were approved by the local ethics committee, and informed consent was obtained from the subjects. The researchers concluded that the single-shot SLOW-EPSI sequence is suitable for mapping α-D-glucose dynamics in the human brain and can be used for future physiological and pathological studies.
In conclusion, the use of α-D-Glucose as a non-radioactive MRS tracer for metabolic studies of the brain holds tremendous potential in advancing our understanding of brain metabolism and neurological disorders. The ability to measure glucose metabolism in a non-invasive and precise manner has opened up new opportunities for research, diagnosis, and treatment of various brain-related diseases. With further research and refinement of this technique, it is certain that α-D-Glucose will continue to play a crucial role in the field of brain metabolism and pave the way for new breakthroughs in neuroscience.
