Introduction to Functional MRI

This chapter gives an overview of how medical imaging, which started with X-rays over 100 years ago, has now progressed to high-quality noninvasive imaging encompassing X-ray, ultrasound, and MRI and has moved on to functional imaging of the brain. Functional MRI (fMRI) started with the discovery of the BOLD signal linked to neuronal activity in the brain. Initially, simple sensory motor activations were imaged (high-resolution color images were created) and subsequently more complex functions, like memory, recall, anger, and emotion, have also been imaged. Parallel to this, techniques for fMRI data analysis have been developed, and medical science has entered an era where we are learning to acquire and analyze a large quantity of data (in fMRI, there are 130,000 data points in the brain in one data set). This chapter gives an overview of fMRI techniques, such as activation-induced imaging, functional connectivity, and the arterial spin labeling technique for cerebral blood flow measurement. Techniques for data acquisition and analysis are introduced here and are covered in detail in the subsequent chapters. The present status of fMRI and its clinical applicability are discussed.