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Mapping brain glucose uptake with chemical exchange-sensitive spin-lock magnetic resonance imaging.

Jin T, Mehrens H, Hendrich KS, Kim SG - J. Cereb. Blood Flow Metab. (2014)

Bottom Line: Several findings are apparent from in vivo glucoCESL studies of rat brain at 9.4 Tesla with intravenous injections.And third, with similar increases in steady-state blood glucose levels, glucoCESL responses are ∼2.2 times higher for 2DG versus Glc, consistent with their different metabolic properties.Overall, we show that glucoCESL MRI could be a highly sensitive and quantifiable tool for glucose transport and metabolism studies.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

ABSTRACT
Uptake of administered D-glucose (Glc) or 2-deoxy-D-glucose (2DG) has been indirectly mapped through the chemical exchange (CE) between glucose hydroxyl and water protons using CE-dependent saturation transfer (glucoCEST) magnetic resonance imaging (MRI). We propose an alternative technique-on-resonance CE-sensitive spin-lock (CESL) MRI-to enhance responses to glucose changes. Phantom data and simulations suggest higher sensitivity for this 'glucoCESL' technique (versus glucoCEST) in the intermediate CE regime relevant to glucose. Simulations of CESL signals also show insensitivity to B0-fluctuations. Several findings are apparent from in vivo glucoCESL studies of rat brain at 9.4 Tesla with intravenous injections. First, dose-dependent responses are nearly linearly for 0.25-, 0.5-, and 1-g/kg Glc administration (obtained with 12-second temporal resolution), with changes robustly detected for all doses. Second, responses at a matched dose of 1 g/kg are much larger and persist for a longer duration for 2DG versus Glc administration, and are minimal for mannitol as an osmolality control. And third, with similar increases in steady-state blood glucose levels, glucoCESL responses are ∼2.2 times higher for 2DG versus Glc, consistent with their different metabolic properties. Overall, we show that glucoCESL MRI could be a highly sensitive and quantifiable tool for glucose transport and metabolism studies.

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Related in: MedlinePlus

Simulations by Bloch–McConnell equations showing that small magnetic field (B0) shifts give large errors in chemical exchange saturation transfer (CEST), and very small errors in chemical exchange-sensitive spin lock (CESL). Large B0-dependent errors appear for (A) CEST asymmetric magnetization transfer ratio (MTRasym) in simulations for three radiofrequency offset (Ω) values, while negligible B0-dependent errors are present for (B) CESL contrast (ΔS/S0), and (C) CESL R1ρ values in simulations at three ω1 levels. Note the vastly different vertical axes scales in panel A versus panel B.
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fig3: Simulations by Bloch–McConnell equations showing that small magnetic field (B0) shifts give large errors in chemical exchange saturation transfer (CEST), and very small errors in chemical exchange-sensitive spin lock (CESL). Large B0-dependent errors appear for (A) CEST asymmetric magnetization transfer ratio (MTRasym) in simulations for three radiofrequency offset (Ω) values, while negligible B0-dependent errors are present for (B) CESL contrast (ΔS/S0), and (C) CESL R1ρ values in simulations at three ω1 levels. Note the vastly different vertical axes scales in panel A versus panel B.

Mentions: Computed errors owing to water resonance frequency variations in CEST and CESL experiments appear in Figure 3. Simulations for typical in vivo CEST saturation (i.e., B1=1.6 μT applied for 4 seconds) show that the asymmetric MT ratio signal at an irradiation offset (Ω) of 400 Hz has an error of 0.5% for the 2-Hz B0 shift often encountered in brain studies,28, 29 1.2% for a 5-Hz shift, and 5% for a 20-Hz shift (Figure 3A). Simulations for typical in vivo CESL studies (i.e., TSL ∼50 milliseconds) show that errors from B0 shifts are greatly reduced (versus CEST) for ω1⩾300 Hz, with negligible effects on either contrast (ΔS/S0; Figure 3B) or on calculated R1ρ values (Figure 3C), even for B0 shifts as large as 20 Hz.


Mapping brain glucose uptake with chemical exchange-sensitive spin-lock magnetic resonance imaging.

Jin T, Mehrens H, Hendrich KS, Kim SG - J. Cereb. Blood Flow Metab. (2014)

Simulations by Bloch–McConnell equations showing that small magnetic field (B0) shifts give large errors in chemical exchange saturation transfer (CEST), and very small errors in chemical exchange-sensitive spin lock (CESL). Large B0-dependent errors appear for (A) CEST asymmetric magnetization transfer ratio (MTRasym) in simulations for three radiofrequency offset (Ω) values, while negligible B0-dependent errors are present for (B) CESL contrast (ΔS/S0), and (C) CESL R1ρ values in simulations at three ω1 levels. Note the vastly different vertical axes scales in panel A versus panel B.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126103&req=5

fig3: Simulations by Bloch–McConnell equations showing that small magnetic field (B0) shifts give large errors in chemical exchange saturation transfer (CEST), and very small errors in chemical exchange-sensitive spin lock (CESL). Large B0-dependent errors appear for (A) CEST asymmetric magnetization transfer ratio (MTRasym) in simulations for three radiofrequency offset (Ω) values, while negligible B0-dependent errors are present for (B) CESL contrast (ΔS/S0), and (C) CESL R1ρ values in simulations at three ω1 levels. Note the vastly different vertical axes scales in panel A versus panel B.
Mentions: Computed errors owing to water resonance frequency variations in CEST and CESL experiments appear in Figure 3. Simulations for typical in vivo CEST saturation (i.e., B1=1.6 μT applied for 4 seconds) show that the asymmetric MT ratio signal at an irradiation offset (Ω) of 400 Hz has an error of 0.5% for the 2-Hz B0 shift often encountered in brain studies,28, 29 1.2% for a 5-Hz shift, and 5% for a 20-Hz shift (Figure 3A). Simulations for typical in vivo CESL studies (i.e., TSL ∼50 milliseconds) show that errors from B0 shifts are greatly reduced (versus CEST) for ω1⩾300 Hz, with negligible effects on either contrast (ΔS/S0; Figure 3B) or on calculated R1ρ values (Figure 3C), even for B0 shifts as large as 20 Hz.

Bottom Line: Several findings are apparent from in vivo glucoCESL studies of rat brain at 9.4 Tesla with intravenous injections.And third, with similar increases in steady-state blood glucose levels, glucoCESL responses are ∼2.2 times higher for 2DG versus Glc, consistent with their different metabolic properties.Overall, we show that glucoCESL MRI could be a highly sensitive and quantifiable tool for glucose transport and metabolism studies.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

ABSTRACT
Uptake of administered D-glucose (Glc) or 2-deoxy-D-glucose (2DG) has been indirectly mapped through the chemical exchange (CE) between glucose hydroxyl and water protons using CE-dependent saturation transfer (glucoCEST) magnetic resonance imaging (MRI). We propose an alternative technique-on-resonance CE-sensitive spin-lock (CESL) MRI-to enhance responses to glucose changes. Phantom data and simulations suggest higher sensitivity for this 'glucoCESL' technique (versus glucoCEST) in the intermediate CE regime relevant to glucose. Simulations of CESL signals also show insensitivity to B0-fluctuations. Several findings are apparent from in vivo glucoCESL studies of rat brain at 9.4 Tesla with intravenous injections. First, dose-dependent responses are nearly linearly for 0.25-, 0.5-, and 1-g/kg Glc administration (obtained with 12-second temporal resolution), with changes robustly detected for all doses. Second, responses at a matched dose of 1 g/kg are much larger and persist for a longer duration for 2DG versus Glc administration, and are minimal for mannitol as an osmolality control. And third, with similar increases in steady-state blood glucose levels, glucoCESL responses are ∼2.2 times higher for 2DG versus Glc, consistent with their different metabolic properties. Overall, we show that glucoCESL MRI could be a highly sensitive and quantifiable tool for glucose transport and metabolism studies.

Show MeSH
Related in: MedlinePlus