Basic MRI Chapter 1 Lecture Introduction MRI uses

Basic MRI Chapter 1 Lecture

Introduction MRI uses radio waves and a magnetic field to make images n Other methods make images in other ways n Radiography – x-ray attenuation n CT – x-ray with computer n NM – gamma rays from radionuclides n US – sound waves n

MR Images n n The image is a display of the radiofrequency (RF) signal intensity The source of the RF signal from the patient is the “condition of magnetization produced when the patient is placed in the magnetic field. ” Magnetization occurs when magnetic nuclei (like H nuclei or protons) are present Magnetization is changed during imaging, and the rate of change depends on tissue characteristics

Tissue Characteristics PD n T 1 n T 2 n Flow n Diffusion n Spectroscopy/chemical shift n

Major Tissue Characteristics PD– proton density n T 1– longitudinal relaxation time; spin-lattice relaxation time n T 2– transverse relaxation time; spin-spin relaxation time n

Minor Tissue Characteristics Flow n Diffusion n Spectroscopy/chemical shift n

What do you see on an MR image? n RF signal intensity, influenced by Tissue magnetization, including saturation pulses n Proton (hydrogen nuclei) density n Relaxation effects from T 1 and T 2 n