ABSTRACT
I. Introduction 162
II. MRI Methodology 162
A. Sequence Design and k-Space Sampling 162
Multishot Sequences 162
Single Shot Sequences 164
B. Spin Polarization 167
C. Breathing Factors 168
D. Local Static Magnetic Field Homogeneity 169
E. Localized Diffusion 170
III. Quantitative Evaluation 170
A. Spatio-Temporal Parametric Analysis 170
IV. Clinical Applications 171
A. Cystic Fibrosis 173
B. Asthma 174
C. Chronic Obstructive Pulmonary Disease 174
D. Hemidiaphragm 175
V. Dynamic Imaging Using Proton MRI 175
References 177
I. Introduction
Hyperpolarized (HP) gas magnetic resonance imaging (MRI) has shown to be
effective at visualizing breath-hold images of ventilation in humans (1).
Optical pumping techniques permit high nuclear spin polarization levels of the
noble gas nuclei, irrespective of the strength of the MRI scanner static field
(B0). As the polarization is not constrained by the processes of saturation
recovery, but more so by radio-frequency (RF) depletion, imaging with very
fast repetition times at high signal-to-noise ratio (SNR) is a realistic prospect
in vivo. This has enabled the dynamic study of gas inhalation and visualization
of the respiratory cycle with fast imaging techniques. Aside from providing visu-
ally striking cinematic movies of ventilation in the lungs, the study of ventilation
dynamics may give insights into lung pathophysiology such as obstruction and air
trapping.
