Nuclear medicine uses radioactive substances to diagnose and treat disease. In diagnostic nuclear medicine, a radiopharmaceutical is administered to the patient and detected by a gamma camera to produce images of organ function. Positron emission tomography (PET) uses radiopharmaceuticals that emit positrons to produce highly accurate images of metabolic activity in the body, making it effective for cancer diagnosis, staging, assessing treatment response, and detecting recurrence. PET's most common radiopharmaceutical is fluorodeoxyglucose (FDG), which is taken up by metabolically active cells including many cancers.

1. What is
Nuclear Medicine?
Todd Charge
Senior Nuclear Medicine Technologist
Hunter Health Imaging Service

2. What is Nuclear Medicine
• Branch of medicine that uses unsealed radioactive
substances in diagnosis and therapy
• These substances consist of pharmaceuticals
labelled with radioisotopes - “radiopharmaceuticals”
• In diagnosis, radioactive substances are administered
to patients and the radiation emitted is measured and
location recorded
• In therapy, radioisotopes are administered to treat
disease
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3. Administration of Radioactivity
• The routes of administration for radiopharmaceuticals
include:
• Intravenous injection: The radiopharmaceutical is
injected into a vein
• Subcutaneous injection: The radiopharmaceutical is
injected under the skin.
• Inhalation: Some radiopharmaceuticals and
radioisotopes are inhaled by the patient
• Ingestion: Radiopharmaceuticals can be ingested
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4. Diagnostic Nuclear Medicine
• In diagnostic nuclear medicine, a radiopharmaceutical
is chosen that is known to follow a particular desired
metabolic pathway
• After comparing the observed biodistribution with that
expected for a healthy person, a diagnosis is made
• Exploits the way that the body handles substances
differently when there is disease or pathology present
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5. Therapeutic Nuclear Medicine
• Nuclear Medicine therapy agents are usually based
on beta-emitting radioisotopes although not always
• Beta particles have a much shorter range in tissue
than do gamma rays so the radiation dose associated
with therapeutic radiopharmaceuticals is limited to the
treatment site
• Exploits the way that the body handles substances
differently when there is disease or pathology present
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6. Production of Radioactivity
• Radioisotopes for use in nuclear medicine are derived
from fission processes in reactors or cyclotrons
• The most commonly used liquid radioisotopes are:
 technetium-99m
 iodine-123 and 131
 thallium-201
 gallium-67
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7. Production of Radioactivity
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8. Production of Radioactivity
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9. Production of Radiopharmaceuticals
• In larger departments production is done in-house in
what is know as a “hot lab”
• For smaller departments specialist outside companies
can provide individual patient doses delivered to your
department
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10. Production of Radiopharmaceuticals
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11. Production of Radiopharmaceuticals
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12. Imaging
• The radiation emitted from the radionuclide inside the
body is detected using a gamma camera
• Gamma-cameras consist of a large sodium-iodide
scintillation crystal, coupled with an array of
associated electronics
• Resolution of approx. 4 to 6 mm and can capture
several hundred thousand gamma-ray 'events' per
second
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13. Imaging
• The gamma-camera will detect the X and Y position
of each gamma-ray event, and these coordinates will
be used to build an image
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14. Imaging
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15. Imaging
• Fundamentally different from radiology, magnetic
resonance imaging and ultrasound
• These modalities are capable of producing excellent
images of internal structural anatomy
• Nuclear medicine images display details of organ
function in terms of the uptake and clearance of
radiopharmaceuticals
• Research is directed towards the development of new
radiopharmaceuticals that follow unexplored
metabolic pathways
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16. Imaging
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17. Imaging
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18. Imaging
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19. Radiation Safety
• Fundamental difference in the source of radiation
exposure
• In Radiology the source of radiation exposure is the
imaging equipment eg x-ray tube, CT
• In Nuclear Medicine the source of exposure is the
radiopharmaceutical and after administration, the
patient
• A gamma-camera does not produce any radiation
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20. Radiation Safety - Patients
• A patient undergoing a nuclear medicine procedure
will receive a radiation dose
• Doses are adjusted by weight for children
• Some studies are performed on pregnant women
• Doses calculated to give just enough for imaging
• Estimated that every person in Australia will have at
least one Nuclear Medicine procedure in their lifetime
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21. Radiation Safety - Patients
Study Activity Effective Dose
Bone scan 800MBq HDP 4.6mSv
Lung scan 200MBq MAA 2.2mSv
Renal scan 200MBq MAG3 1.4mSv
Myocardial 300 / 1000MBq of MIBI 10.6mSv
perfusion scan
Gallium scan 200MBq of Ga 20.0mSv
CXR 0.04mSv
Abdo XRay 1.2mSv
Lumbar Spine 2.1mSv
CT chest 7.8mSv
Barium enema 8.7mSv
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22. Radiation Safety - Patients
• Natural background radiation in the Sydney area
• 1.4 – 2.5 mSv/y
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23. Radiation Safety - Staff
• Three principles
 Time
 Distance
 Shielding
• Staff still work whilst pregnant, right up to time of
choosing. Recommend pelvic shielding
• No infertility to staff
• All staff monitored monthly
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24. PET
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25. What is PET
• Positron Emission Tomography (PET) is rapidly
becoming a major diagnostic imaging modality
• Used predominantly in determining
 presence and severity of cancers
 neurological conditions
 cardiovascular disease
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26. What is PET
• PET camera measures the biodistribution of positron
emitting radionuclides after injection into the patient
• Positron emitting radionuclides are used for their
unique simultaneous emission of back to back
gamma rays
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27. What is PET
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28. What is PET
• Is currently the most effective way to check for cancer
recurrences
• Studies demonstrate that PET offers significant
advantages over other forms of imaging such as CT
or MRI scans in diagnosing disease
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29. PET
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30. PET Radiopharmaceuticals
• Most widely used is F-18 (Fluorine)
• F-18 is labelled to a glucose analog (DeoxyGlucose)
• Forming FDG
• Follows glucose pathway from plasma into cells
• Unlike glucose, FDG is not metabolised and is
trapped in cells allowing imaging
• Half-Life 109mins
• Produced in cyclotron
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31. Biodistribution
• Every cell in the body uses glucose
• After IV injection patients rest for 40-50mins to allow
organ uptake of FDG and clearance from blood
plasma into cells
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32. Biodistribution
• Any metabolically active muscles will show increased
uptake
• Many malignant tumours accumulate FDG due to
glycolysis and cell proliferation rate
• Benign tumours usually uptake less FDG so can be
potentially distinguished from malignant tumours
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33. Use
• Cancers for which PET is considered particularly
effective include
 Lung
 Head and Neck
 Colorectal
 Oesophageal
 Lymphoma
 Melanoma
 Breast
 Thyroid
 Cervical
 Pancreatic
 Brain
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34. Use
• PET is effective in identifying
 whether cancer is present or not
 if it has spread
 if it is responding to treatment
 if a person is cancer free after treatment
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35. Use
• Early Detection:
 Because PET images biochemical activity, it can
accurately characterise a tumour as benign or
malignant, thereby avoiding surgical biopsy when
the PET scan is negative. Conversely, because a
PET scan images the entire body, confirmation of
other metastasis can alter treatment plans in
certain cases from surgical intervention to
chemotherapy.
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36. Use
• Staging of Cancer:
 PET is extremely sensitive in determining the full
extent of disease, especially in lymphoma,
malignant melanoma, breast, lung, colon and
cervical cancers. Confirmation of metastatic
disease allows the physician and patient to more
accurately decide how to proceed with the patient's
management
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37. Use
• Assessing the Effectiveness of Chemotherapy:
 The level of tumour metabolism is compared on
PET scans taken before and after a
chemotherapy cycle. A successful response seen
on a PET scan frequently precedes alterations in
anatomy and would therefore be an earlier
indicator of tumour response than that seen with
other diagnostic modalities
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38. Use
• Checking for recurrences:
 PET is currently considered to be the most
accurate diagnostic procedure to differentiate
tumour recurrences from radiation necrosis or post-
surgical changes. Such an approach allows for the
development of a more rational treatment plan for
the patient.
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