Prospective MR image alignment between breath-holds: Application to renal BOLD MRI.
To present an image registration method for renal blood oxygen level-dependent (BOLD) measurements that enables semiautomatic assessment of parenchymal and medullary R2* changes under a functional challenge.



In a series of breath-hold acquisitions, three-dimensional data were acquired initially for prospective image registration of subsequent BOLD measurements. An algorithm for kidney alignment for BOLD renal imaging (KALIBRI) was implemented to detect the positions of the left and right kidney so that the kidneys were acquired in the subsequent BOLD measurement at consistent anatomical locations. Residual in-plane distortions were corrected retrospectively so that semiautomatic dynamic R2* measurements of the renal cortex and medulla become feasible. KALIBRI was tested in six healthy volunteers during a series of BOLD experiments, which included a 600- to 1000-mL water challenge.



Prospective image registration and BOLD imaging of each kidney was achieved within a total measurement time of about 17 s, enabling its execution within a single breath-hold. KALIBRI improved the registration by up to 35% as found with mutual information measures. In four volunteers, a medullary R2* decrease of up to 40% was observed after water ingestion.



KALIBRI improves the quality of two-dimensional time-resolved renal BOLD MRI by aligning local renal anatomy, which allows for consistent R2* measurements over many breath-holds. Magn Reson Med 77:1573-1582, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
Inge M
IM
Kalis
Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
David
D
Pilutti
Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany.|German Cancer Consortium, Heidelberg, Germany.|German Cancer Research Center, Heidelberg, Germany.
Axel J
AJ
Krafft
Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
Jürgen
J
Hennig
Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
Michael
M
Bock
D000465:Algorithms; D062485:Breath Holding; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007668:Kidney / Q000033:anatomy & histology / Q000378:metabolism*; D007677:Kidney Function Tests / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000378:metabolism*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique
D010100:Oxygen
BOLD; R2*; image registration; prospective motion correction; renal oxygenation measurement