MAGNETIC RESONANCE IMAGING by PRADEEP V.EPAKAYAL. Mem.no L

INTRODUCTION Magnetic resonance imaging (MRI) medical imaging technique used in radiology to visualize detailed internal structures. MRI makes use of the property of nuclear magnetic resonance (NMR) to image nuclei of atoms inside the body.

DIFF.PARTS OF MRI

DIFF PARTS OF MRI con`t

GENERAL WORKING OF MRI  Put subject in big magnetic field  Transmit radio waves into subject [2~10 ms]  Turn off radio wave transmitter  Receive radio waves re-transmitted by subject0  Convert measured RF data to image

Many factors contribute to MRI Quantum properties of nuclear spins Radio frequency (RF) excitation properties Tissue relaxation properties Magnetic field strength and gradients Timing of gradients, RF pulses, and signal detection

Hydrogen atoms are best for MRI Biological tissues are predominantly 12 C, 16 O, 1 H, and 14 N Hydrogen atom is the only major species that is MR sensitive Hydrogen is the most abundant atom in the body The majority of hydrogen is in water (H 2 O) Essentially all MRI is hydrogen (proton) imaging

NUCLEAR SPIN EXCITATION RELAXATION

IMAGE CONTRAST MRI provides good contrast between the different soft tissues of the body, which makes it especially useful in imaging the brain, muscles, the heart, and cancers.

IMAGE CONTRAST con`t

ADVANTAGES Superior soft tissue contrast resolution - excellent pathological discrimination No ionizing radiation Direct multi-planar imaging (transverse, coronal, sagittal, any oblique) Non-invasive - vascular studies can be performed without contrast

DISADVANTAGES OF MRI Expensive Long scan times Audible noise (65-115dB) Isolation of patient (claustrophobia, monitoring of ill patients) Exclusion of patients with pacemakers and certain implants

APPLICATION OF MRI MRI is used to distinguish pathologic tissue (such as a brain tumor) from normal tissue It is used to examine a large variety of medical conditions. Diagnosing multiple sclerosis (MS) Diagnosing strokes in their earliest stages

CT SCAN CT, Computerized Axial Tomography, uses x rays to generate images of the body, including bone

PRINCIPLE OF CT CT scans use a series of X-ray beams It creates cross-sectional images, e.g. of the brain and shows the structure of the brain, but not its function.  Digital geometry processing is used to generate a three dimensional image of the internals of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation.

MRI VS CT MRI SCANNERCT SCANNER

MRI VS CT con`t MRI IMAGECT IMAGE

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