Introduction

The advent of neuroimaging techniques that yield physiological in addition to structural information are of particular interest in the scientific and clinical investigations of neurodegenerative and psychiatric disorders. These are groups of conditions where any structural changes that are evident on anatomical imaging sequences generally correlate poorly with clinical diagnostic categories, underlying pathophysiology, and disease severity.

The T1- and T2-dependent MR sequences, on which most routine clinical neuroimaging relies, are frequently insensitive to the underlying pathological processes in these diseases. Focal or global atrophy from associated neuronal loss is also frequently subtle or absent, particularly early in the course of disease. As a result, clinical brain imaging using standard techniques is frequently normal, or non-specifically abnormal.

Physiological imaging can be considered to have two main purposes in this context. The first is clinical: to provide diagnostic information which augments that available from clinical examination, laboratory tests, and conventional structural brain imaging. The aim here is to increase the sensitivity and/or specificity of the imaging examination as a whole and to improve diagnostic confidence, which will ultimately guide clinical management. In this context, the technique must provide a surrogate marker of disease that is of predictive value in diagnosis or prognosis for an individual patient.

Introduction

The socioeconomic impact of adult primary brain neoplasms is disproportionate to their incidence; they often affect young adults, cause significant morbidity, and are usually ultimately fatal. Moreover, advances in treatment of primary malignancies outside the CNS has led to more aggressive clinical management of brain metastases.

Reliable characterization of intracranial masses is, therefore, essential for rational clinical management: in initial diagnosis and prognosis, stratification and planning of therapy for individual patients, and evaluating outcome with established and novel treatment regimens.

The relatively high risk of performing invasive procedures in the brain places particular emphasis on neuroimaging in the evaluation of brain masses. Conventional structural MRI and computed tomography (CT) are widely used in clinical practice but provide limited biological specificity and diagnostic and prognostic information. Non-invasive physiological imaging techniques that augment the information available from structural imaging and inform clinical management are clearly desirable.

Preface to the first edition

The advent of clinical MR imaging (MRI) in the 1980s heralded a new era in the ability to image the brain in vivo. MRI allows the detailed depiction of brain anatomy and pathology with unprecedented spatial resolution and soft-tissue contrast. It is also relatively safe and completely non-invasive. Nevertheless, the sensitivity and specificity with which structural MRI alone can define the wide range of neurological disease is limited.

The last decade has also seen the development of physiological MR techniques, whereby information concerning tissue function as well as structure is obtained. These techniques include diffusion, perfusion, and MR spectroscopy, which provide information on tissue ultra-structure, blood flow, and biochemistry, respectively. Information of this type supplements and complements that from clinical or structural imaging investigations, often providing important surrogate markers of disease pathophysiology or therapeutic response.