ABSTRACT
I. Introduction 114
II. Molecular MRI 115
A. Traditional CAs 115
B. Organ-Specific CAs 116
C. Targeted CAs 116
D. Activated CAs 116
E. Targeting Cellular Markers 117
F. Imaging Transgene Expression 117
G. Switchable CAs 119
H. Imaging Gene Products 119
III. MRI of Lung 119
A. Proton Imaging 120
B. Hyperpolarized Gas Imaging 121
C. Diffusion 124
D. Ventilation Imaging 125
E. Intrapulmonary pAO2 127
F. Perfusion Imaging 127
IV. Future Prospects 128
Acknowledgment 128
References 128
I. Introduction
Magnetic resonance imaging (MRI) is a powerful and versatile imaging modality
for the noninvasive, in vivo characterization of biological systems. The relatively
low tissue density and large number of air-tissue interfaces in lung present
several unique challenges to its study by magnetic resonance (MR). Nonetheless,
MR techniques have been developed to provide important insights into the struc-
ture and dynamics of lungs in humans and in small-animal models of lung
disease. These methods include both conventional MRI of the hydrogen atoms
in water in lung tissue and imaging of air spaces using hyperpolarized helium
gas. Molecular imaging can provide important insights into biological processes
at the cellular or subcellular level. The linking of specific targeted molecular
agents with the superb anatomical resolution provided by MRI forms a particu-
larly powerful combination. In this chapter, we provide an overview of MR mol-
ecular imaging and MRI of lung in both humans and small animals and discuss
the prospects for the development of MR-based molecular imaging techniques in
lungs.
