Magnetic Resonance Imaging




 In 1952, Bloch and Purcell won the Nobel Prize in Physics for the development of the analytical technique known as nuclear magnetic resonance (NMR). Magnetic resonance imaging (MRI) is an adaptation of NMR for medical diagnostic purposes.

Both NMR and MRI rely on the fact that some atomic nuclei have a magnetic moment associated with their spinning. The most common nuclei studied using NMR are H-1, C-13, F-19 and P-31. Most MRI studies involve the H-1 nuclei in water.

The isotopes listed above have two spin states. When these nuclei are exposed to an external magnetic field, their spins can be parallel or anti-parallel to this external field. Transitions between these two spin states can be induced with energy from radio waves of the proper frequency. A radio frequency (rf) signal is transmitted to the sample, which has been placed in a strong magnetic field. The nuclei of atoms in the sample interact with the rf signal. An rf receiver measures the signal after its interaction with the sample. The analysis of these measurements can help to identify the structure of the sample.

MRI instruments are massive pieces of equipment. Some representative specifications from an instrument manufacturer are collected in the table below.


Bruker Full-size whole-body MRI/MRS system

MEDSPEC 30/80 MEDSPEC 30/100 MEDSPEC 40/80
Magnet-field strength   3 Tesla  3 Tesla  4 Tesla
Bore, diameter of patient
instrument cavity
 80cm  94 cm  80 cm
Max. gradient strength  45 mT/m  30 mT/m  45 mT/m
 Magnet weight  7.8 tons  12 tons  13 tons
 Body region to be
 brain, extremities,
cardiac, and spine
 whole-body  brain, extremities,
cardiac, and spine

Other NMR/MRI web sites

 National Magnetic Resonance Facility at Madison

Magnetic Resonance Imaging (MRI) - Body

Magnetic resonance imaging - Wikipedia, the free encyclopedia 
 How Stuff Works: Magnetic Resonance Imaging (MRI) 
 The Basics of MRI 

Suppliers of MRI Equipment

General Electric Healthcare

 For the latest in MRI diagnostic equipment
 MRI diagnostic equipment
 MRI unit is used in the operating room during surgery.
This MRI unit is used in the operating room during surgery. For more information, see: