Medical applications of nuclear physics

1. Medical Applications
of Nuclear Physics

2. Nuclear Physics
Medical Applications
Diagnostic Imaging

3. The First “Medical Application”
Source:Radiological Society of North America, Inc (http://www.radiologyinfo.org)

4. CAT scan
Computerized Axial Tomography
Source: Cutnell and Johnson, 7
th
edition image gallery

5. CAT scan
X-rays are produced and emitted in thin, fanned
out beams
Detected on the opposite side of the patient via
arrays of x-ray detectors
Scanner rotates to get the full 2-D picture
The patient is passed through the scanner in
small steps to get ‘slices’ for 3-D reconstruction
Computer control allows for high level of
precision yield very detailed images

6. CAT scan advantages
3-D reconstruction of the internal organs
High resolution giving doctors very good
details prior to grabbing a knife
CAT scans can image soft tissue, bone,
and blood vessels at the same time
Often less expensive than an MRI and
can be used with medical implants and
metal objects
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

7. CAT scan reconstructed
Source: Cutnell and Johnson, 7th edition image gallery

8. CAT scan image of lung
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

9. CAT scan dangers
Increased exposure to x-ray radiation
NBC Nightly News recently reported on an
article in the New England Journal of Medicine
that up to as much as 2% of new cancer cases
may be caused by CT scans
A CT scan of the chest involves 10 to 15
millisieverts versus 0.01 to 0.15 for a regular
chest X-ray
Nevertheless, it’s still a powerful tool … just
don’t over use it.
Source: http://www.msnbc.msn.com/id/22012569/

10. PET scan
Positron Emission Tomography
A radioactive source (positron emitter) is injected into the
patient usually attached to a sugar
Cancers have unusually high metabolic rates so the sugar
solution goes more to the cancer cells than the other
tissues
Emitted positron annihilates with an electron to produce
two gamma rays
Gamma rays leave traveling in opposite directions
Coincident detection of gamma rays can be computer
reconstructed to give high resolution images of the
internal organs
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)
Source: Cutnell and Johnson, 5
th
edition text

11. PET scan advantages
Very powerful imaging tool
Produces higher resolution images
Can detect changes in metabolic activity
before changes in the anatomy are seen
in CAT and MRI images
Can be used in combination with CT and
MRI images (CT/PET scans are
becoming more widely used)
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

12. PET scanner
Source: Cutnell and Johnson, 7th edition image gallery

13. PET scan image
Source: Cutnell and Johnson, 7th edition image gallery

14. CAT/PET scan combined
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

15. PET scan dangers and
limitations
PET scan dosages are very small (it’s an
efficient method for imaging) but its still
radiation
Must weigh the danger against the rewards
These radio-nuclides have short half-lives which
means they must be produced locally or pay
huge shipping costs
Sometimes gives false positives if there is
chemical imbalances in the patient
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

16. MRI imaging
Magnetic Resonance Imaging
Patient is placed in a powerful non-
uniform magnetic field
A electromagnetic wave is transmitted
into the body and at the right frequency it
is absorbed. This absorption is detected
by the machine.
A computer reconstructs the location of
the cells to develop 3-D images
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)
Source: Cutnell and Johnson, 5
th
edition

17. MRI imaging machine
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

18. MRI image of the knee
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

19. MRI dangers and limitations
Confined environment
No metals allowed!
Does not do well with lungs
The patient must lie perfectly still so
anxiousness may make the images
blurry
MRI’s can be expensive

20. Nuclear Physics
Medical Applications
Treatments

21. Gamma Knife Radio surgery
Use of gamma rays to treat cancerous
tumors
Directs gamma radiation from many
directions to a specific location to
delivery a powerful dose of radiation
Does not require surgery
Can treat cancers where conventional
surgery is not possible
Source: Cutnell and Johnson, 7th edition image gallary

22. Gamma Knife device
Source: Cutnell and Johnson, 7th edition image gallery

23. Gamma Knife disadvantages
Exposure to significant radiation
Must be aligned to within a millimeter for
accurate treatment
Is not guaranteed to destroy all the
cancer (it’s a treatment, after all)
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

24. Linear Accelerator
High energy electrons are crashed into a
heavy metal target and emit x-rays
Energy, intensity, and location of the x-
rays are controlled to deliver radiation to
a tumor
Precision and accuracy are very good
and getting better
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

25. Linear Accelerator in Operation
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

26. Linear Accelerator Drawbacks
X-ray radiation can damage healthy
tissue
Must be aligned correctly for good
accuracy
Movement of internal organs requires
larger beam area to get the cancer …
you don’t want to do this again
Equipment is expensive … but getting
much better

27. Proton Therapy
Similar to the linear accelerator therapy
except energetic protons are directed at
the tumor
Varying the energy of the protons results
in good deep control
Can be focused to the size of a pin
Usually results in less damage to healthy
tissue
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

28. Proton Therapy
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)

29. Proton Therapy Disadvantages
Radiation exposure to good tissues
Requires the cancer to remain still for
good precision and minimization of
collateral damage
Very expensive and only used at a few
locations in North America
Source: Radiological Society of North America, Inc (http://www.radiologyinfo.org)