Quantified pH imaging with hyperpolarized (13) C-bicarbonate.

Area of Science:

• Medical Imaging
• Biophysics
• In Vivo Diagnostics

Background:

• Accurate in vivo pH measurement is critical for understanding and diagnosing various diseases.
• Current methods for pH monitoring often lack spatial resolution or are invasive.
• Developing noninvasive, spatially localized pH measurement techniques is a significant clinical need.

Purpose of the Study:

• To develop and validate a hyperpolarized Carbon-13 bicarbonate (¹³C-BiC) based pH mapping technique for in vivo applications.
• To assess method-based errors and optimize the technique for the biologically relevant pH range (6-8).
• To apply the developed pH mapping method in vivo in healthy and inflamed animal models.

Main Methods:

• Utilized in vitro and in vivo ¹³C magnetic resonance imaging (MRI) with spectral-spatial excitation and spiral readout.
• Optimized signal-to-noise ratio for hyperpolarized ¹³C-BiC.
• Induced acute subcutaneous sterile inflammation in rats to model disease conditions and measured pH and proton images.

Main Results:

• The developed method demonstrated low pH error (< 0.2) across the biologically relevant pH range of 6 to 8.
• Quantified pH maps showed negligible impact from residual bicarbonate signals.
• In vivo pH maps accurately reflected induced acute metabolic alkalosis and identified lower pH in inflamed regions.

Conclusions:

• Hyperpolarized ¹³C-BiC pH mapping is a sensitive and accurate technique for in vivo pH measurement within the biologically relevant range.
• The method was successfully applied to healthy organs and demonstrated utility in models of inflammation and metabolic alkalosis.
• This technique holds promise for noninvasive, spatially resolved pH monitoring in clinical settings.