Transcript 5. Medical Application Using Radioactivity

General, Organic, and
Biological Chemistry
Fourth Edition
Karen Timberlake
Chapter 4
Nuclear Chemistry
4.5
Medical Application
Using Radioactivity
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Lectures
Medical Applications
Radioisotopes with short halflives are used in nuclear
medicine because they
 have the same chemistry in
the body as the
nonradioactive atoms, and
 give off radiation that
exposes a photographic
plate (scan), giving an
image of an organ.
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Thyroid scan
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Medical Applications of Common
Radioisotopes
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Scans with Radioisotopes
After a person receives a radioisotope,
 the radiologist determines the level and location of
the radioactivity emitted by the radioisotope,
 a scanner is used to produce an image of the organ,
 gamma rays emitted from the radioisotope in the
organ can be used to expose a photographic plate
providing an image of the organ, and
 areas of decreased or increased radiation can
indicate the presence of a medical problem.
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Scans with Radioisotopes
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Positron Emission Tomography
(PET)
Positron Emission Tomography
 utilizes positron emitters with short half-lives, such as
carbon-11, oxygen-15, nitrogen-13, and fluorine-18.
 utilizes the positron emitter fluorine-18 to study brain
function, metabolism and blood flow.
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Positron Emission Tomography
(PET)
These PET scans of the brain show a normal brain
on the left and a brain affected by Alzheimer’s
disease on the right.
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Magnetic Resonance Imaging
(MRI)
Magnetic Resonance Imaging
 is a powerful imaging technique that does not
involve x-ray radiation.
 is the least invasive imaging method available.
 is based on the absorption of energy when the
protons in hydrogen atoms are placed in a strong
magnetic field.
 uses short pulses of energy to align the hydrogen
protons against the magnetic field.
 utilizes a scanner to convert the different energies
absorbed into an image.
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Magnetic Resonance Imaging
(MRI)
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Learning Check
Which of the following radioisotopes are likely to be
used in nuclear medicine?
A. K-40 (half-life – 1.3 x 109 years)
B. K-42 (half-life – 12 hours)
C. I-131 (half-life – 8 days)
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Solution
Which of the following radioisotopes are likely to be
used in nuclear medicine?
Radioisotopes with short half-lives are used in
nuclear medicine.
B. K-42 (half-life – 12 hours)
C. I-131 (half-life – 8 days)
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