1. The strength of the flux density at the Earth’s surface ranges from less than 30μT in an area including most of South America and South Africa to over 60μT in northern Canada and south of Australia.
Why does it vary?
Comment on the strength of the magnetic field inside an MRI scanner

2. Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI

3. Precession Larmor Frequency Relaxation Time
Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI
What do the following terms mean?
Precession
Larmor Frequency
Relaxation Time
What does the process have to do with resonance?

4. Be able to describe the main components of an MRI scanner
Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI

5. Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI
Apparatus used in MRI

6. This varies the Larmor frequency at different points
Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI
There is a high constant magnetic field across the imaging section (Approx 90cm long) The field strength is typically 1.4 T
This is produced by a super-cooled electromagnet kept at a temperature of 4.2K
Additional magnets are used to alter the magnetic field strength very slightly throughout the scanner
This varies the Larmor frequency at different points

7. An RF coil transmits the RF pulse into the body.
Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI
An RF coil transmits the RF pulse into the body.
An RF receiver coil detects the signal emitted by the nuclei as they relax to their original orientation. This may be the same coil as the transmitter coil.
A computer controls the magnetic field strength throughout the scanner and the RF pulses as well as storing and analysing the received signals.
The image formed represents areas of different relaxation times as different shades / colours

8. At what distance from X is the Larmor frequency:
Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI
The magnetic field due to the main magnet in a MRI scanner is 1.400T. Using subsidiary magnets, the total field is increased linearly from 1.400T at point X to 1.440T at point Y a distance of 0.500m along the length of the patient.
At what distance from X is the Larmor frequency:
59.5 MHz
61.2 MHz
60.0 MHz?

9. Be able to describe the main components of an MRI scanner
Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI

10. What are the pros and cons of MRI scans?
Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI
What are the pros and cons of MRI scans?
- Sort the statements and explain why

11. Does not use ionising radiation
Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI
Does not use ionising radiation
Good distinction between types of soft tissue
Radiowaves can travel through bone
Metallic objects would heat up if placed in scanner
Scans take around 45 minutes
The receivers can detect radiowaves from any sources
Machines are very expensive

12. Patient does not receive a dose of ionising radiation
Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI
The upside…
Patient does not receive a dose of ionising radiation
Staff are not exposed to ionising radiation
High quality image with clear contrast between tissue type
The brain can be imaged

13. Many people suffer from claustrophobia when having a scan done
The downside…
Patients cannot be scanned if they have a pace maker or metal pins in joints
Many people suffer from claustrophobia when having a scan done
Equipment must be screened to eliminate any stray fields
Scanners cost millions of pounds and cannot have a fast throughput of patients because each scan takes so long
Learning Objectives
By the end of this lesson you should…
Be able to describe the main components of an MRI scanner
Be able to outline the use of MRI to obtain diagnostic information about internal organs
Be able to outline the benefits and limitations of MRI