Renal and systemic pH imaging by contrast-enhanced MRI

Area of Science:

• Biomedical Imaging
• Medical Diagnostics
• Renal Physiology

Background:

• Kidney diseases, like renal tubular acidosis, involve altered systemic and renal pH.
• Accurate imaging of tissue pH is crucial for assessing the severity of kidney conditions.
• Current diagnostic methods may not fully capture the dynamic pH changes in renal tissues.

Purpose of the Study:

• To develop and validate a novel Magnetic Resonance Imaging (MRI) method for mapping renal and tissue pH.
• To utilize a dual-contrast-agent strategy with pH-sensitive and pH-insensitive agents for quantitative pH imaging.
• To assess the feasibility of this technique in detecting pH alterations in conditions like metabolic acidosis.

Main Methods:

• A dual-contrast-agent approach using pH-insensitive GdDOTP(5-) and pH-sensitive GdDOTA-4AmP(5-) was employed.
• Dynamic T(1)-weighted MRI scans were acquired in mice following intravenous boluses of the contrast agents.
• Pharmacokinetic data and signal enhancements were analyzed pixel-wise to generate quantitative pH maps.
• Mice were pretreated with acetazolamide to induce systemic metabolic acidosis and urine alkalinization.

Main Results:

• The developed MRI technique successfully generated pH maps of kidneys and surrounding tissues.
• Acidic regions were identified in control mouse kidneys, corresponding to the renal papilla, calyx, and ureter.
• Acetazolamide-induced metabolic acidosis and subsequent urine alkalinization were clearly detected by the pH mapping method.

Conclusions:

• The dual-contrast-agent MRI strategy is effective for non-invasive imaging of tissue pH.
• This method holds promise for evaluating kidney diseases and metabolic disturbances.
• The technique provides valuable insights into localized pH changes within the renal system.