Neuroimaging

Neuroimaging encompasses a set of techniques used to visualize the structure and function of the nervous system, primarily the brain. The field supports clinical diagnosis, treatment planning, and research into brain function. Imaging modalities are broadly categorized as structural, revealing anatomy, or functional, measuring brain activity or physiology. Structural imaging includes computed tomography (CT) and magnetic resonance imaging (MRI). CT uses X-rays to provide rapid images of brain anatomy and is often employed in acute injury. MRI uses strong magnetic fields and radiofrequency pulses to produce high-resolution images; specialized sequences yield information on tissue properties, and diffusion MRI maps white-matter tracts.

Functional imaging aims to measure neural activity. Functional MRI (fMRI) detects blood-oxygen-level-dependent (BOLD) signals as a proxy for neural activity, offering relatively good spatial resolution but limited temporal precision. Positron emission tomography (PET) uses radiotracers to measure metabolic processes, receptor binding, or blood flow; single-photon emission computed tomography (SPECT) provides similar information with different tracers. Other techniques include MR spectroscopy (MRS), which assesses chemical composition, and diffusion tensor imaging (DTI), used to characterize white matter integrity.

Applications include diagnosis and monitoring of stroke, tumors, epilepsy, and neurodegenerative diseases, pre-surgical planning, and mapping functional networks for research. Multimodal imaging combines data from several modalities to improve interpretation but introduces complexity and cost. Safety considerations include exposure to ionizing radiation with CT and PET, contrast agents, and the need for careful interpretation to avoid incidental findings. Limitations involve trade-offs between spatial and temporal resolution, susceptibility to artifacts, and the need for specialized analysis methods. Ongoing developments aim to improve resolution, speed, and accessibility, and to enhance quantitative interpretation of imaging data.