MRI

Imaging DivisionP.D. Hinduja National Hospital and

Research Centre

What Is It

• A test to obtain detailed images of the human body

• No ionizing radiation – so not harmful• Superb Soft tissue contrast• Imaging in multiple planes

• Magnetic - Powerful Magnetic Field• Resonance - Radiofrequency• Imaging - Visualization

Magnetic

• Powerful Magnet (Tesla – T)– Strength varies from 0.3 Tesla – 7 Tesla– Doughnut / Tunnel : Higher strength but

claustrophobic– Partially open : Lower strength, less

claustrophobic– Hydrogen ion – proton used most commonly

• Once in the magnet, protons line up in the direction of the magnetic field

Resonance

• Radiofrequency Pulse : low strength electromagnetic pulse, generated by RF coils, used to align these protons together

• After the pulse is switched off, the protons slowly return to the original state

• As they return, they give off energy in form of that is then received by special receiver coils, which convert it into a signal

Imaging

• The signal received is then converted to Images

• These are then looked at and analysed by the Radiologist

Application

• Brain• Spine• Musculoskeletal System• Body – especially Abdominal Organs• Heart• Blood vessels

Procedure

• Patient lies down on the table• Table then slides into the bore of the

magnet• Various ‘sequences’ are obtained• Intravenous contrast injection may be

given, depending upon the condition being investigated and the images obtained

• Patient comes out of the tunnel

Procedure

• As the images are obtained, lot of noise can be heard

• Generally ear plugs are provided. Some centres provide head phones and even music!

• No pain, no sensation.• Patient has to lie still, as movement during the

scan can result in artefacts which can compromise the quality of images

•MRI has allowed clinicians to treat, monitor, and learn about many different diseases and problems. •Also, to learn how the body functions, normally, without needing to resort to more invasive methods like surgery.

• MRI treatment is a wonderful option for most patients, but there are some people who are not candidates.

• Those include:– Patients with pacemakers: as the magnet from

the MRI interferes with the signal sent from the pacemaker, and deactivates it.

– Patients who are too tall, or too obese– Patients who have orthopedic hardware can get

distortion in the image, and the scan quality is not as high.

Future• The possibility of having very small machines that scan specific parts of the body.• The continuing improvements on seeing the venous and arterial systems.• Functional Imaging :Brain mapping while the

patient does specific tasks, allowing clinician’s to see what part of the brain is responsible for that task/activity.

• Improvements on the ability to do MRI’s of the lungs.