Prospective MR image alignment between breath-holds: Application to renal BOLD MRI

Area of Science:

• Medical Imaging
• Renal Physiology
• Magnetic Resonance Imaging

Background:

• Renal blood oxygen level-dependent (BOLD) MRI is crucial for assessing kidney function.
• Accurate R2* measurements are needed for evaluating parenchymal and medullary changes.
• Current methods face challenges with anatomical consistency during dynamic assessments.

Purpose of the Study:

• To introduce a novel image registration method for renal BOLD MRI.
• To enable semiautomatic assessment of R2* changes in the renal cortex and medulla.
• To facilitate dynamic R2* measurements under functional challenges.

Main Methods:

• Developed and implemented the Kidney Alignment for BOLD Renal Imaging (KALIBRI) algorithm.
• Utilized prospective image registration for consistent kidney positioning across breath-holds.
• Applied retrospective correction for residual in-plane distortions.
• Tested KALIBRI in six healthy volunteers during water-induced functional challenges.

Main Results:

• KALIBRI achieved prospective image registration and BOLD imaging within a single 17-second breath-hold.
• The algorithm improved image registration accuracy by up to 35%.
• Observed a significant decrease in medullary R2* (up to 40%) after water ingestion in four volunteers.

Conclusions:

• KALIBRI enhances the quality of time-resolved renal BOLD MRI through improved anatomical alignment.
• This method allows for consistent and reliable R2* measurements over multiple breath-holds.
• KALIBRI facilitates more accurate assessments of renal physiological changes.