1. Instruments & Radiopharmaceutical Production
NM 4103 Section II
Instruments & Radiopharmaceutical Production

2. Gas Filled Detectors Ionization chambers Geiger-Muller counters
Operate on V
Dose Calibrator
Geiger-Muller counters
Operate around 1000V

3. Dose Calibrator Sealed chamber Filled with argon & halogen
Operating voltage
around 150 V
Used for measuring activity of radiopharmaceuticals

4. Geiger-Muller Counter
Used to detect beta and gamma radiations
Usually operates as a ratemeter
Readings can be given in:
uR/hour
mR / hour
R / hour
Cpm
Used for area survey (contamination)
Calibrated annually with 226Ra or 137Cs
Ur/hr = micro-roentgen per hour
mR/hr = Milli-roentgen per hour
R / hr = Roetngen per hour
Cpm = counts per minute

5. Scintillation Detectors
Well counter
Thyroid probe
Gamma camera
Gamma rays interact in the sodium iodide detector and light photons are emitted.

6. Detectors Sodium iodide crystals (most common)
Light generated in the crystal is then directed at the PM tube
Sodium Iodide crystals are very Fragile

7. Collimators Covers the sodium iodide detector
Purpose is to limit the field of view
Made of lead
Holes of different shapes and sizes
Increased number of holes = increased sensitivity (but loss of resolution)

8. Thyroid Probe Collimator
Single bore
Cylinder shaped
One PM tube

9. Scintillation Camera Collimators
Parallel : most common
Diverging : organ larger than the size of the detector
Pinhole : small organs/areas (thyroid)
Converging : organ smaller than the size of the detector

10. Parallel-hole Collimator
Can be high-resolution, all purpose or high-sensitivity
Size and number of holes the same, change thickness
High sensitivity = smallest thickness
High resolution = thickest
All purpose = middle
*want to imaged close to the patient *spatial resolution is best at the collimator face

11. Photomultiplier Tube Fixed to the sodium iodide crystal
Photocathode / series of dynodes / anode (all in a vacuum glass tube)
*when a pm tube goes out, you will see a dark circle on your daily uniformity flood

12. Cyclotron
Charged particles are accelerated in circular paths under vacuum by an electromagnetic field
Radionuclides are usually neutron deficient and decay by + emission or electron capture
Examples:
Gallium-67
Iodine-67
Indium-111
Thallium-201
PET radiopharmaceuticals
(Carbon-11,Nitrogen-13,Oxygen-15,Fluorine-18)
Elements in Nature with an atomic number greater than 83 are Radioactive
Radionuclides used in nuclear medicine are mostly artificial
B+ : Positron

14. Reactor Constructed with fuel rods that undergo spontaneous fission
Radionuclides are usually neutron rich and decay by - emission
Examples:
Iodine-131
Molybemum-99
Xenon-133
Cesium-137
Fission = breakup of a heavy nucleus into two fragments accompanied by the emission of two to three neutrons
B- : Beta

15. Specific Activity Radioactivity per unit mass Expressed in mCi / mg
Accurate only at the date and time of calibration
On the radipharmacy label

16. Concentration Radioactivity per unit volume Expressed in mCi / ml
Accurate only at the date and time of calibration
Found on the radiopharmacy label

17. Generator
Long lived parent radionuclide continually decays to a shorter lived daughter radionuclide
Chemical properties must be different, so they can be easily separated from one another
Generator must be sterile and pyrogen-free
Used for humans

19. Parent/Daughter relationship
Daughter grows as a result of the decay of the parent until equilibrium is reached
Daughter activity is eluted, leaving the parent on the column
After elution, the daughter activity starts to grow again

20. 99Mo - 99mTc Generator
99Mo has a half-life of 66 hours & decays by - emission
99mTc has a half-life of 6 hours & decays by isomeric transition
Liquid or solid column
Liquid is rarely used in nuclear medicine
B- : beta

21. Solid column generator
Alumina oxide on a column (encased in lead)
99mTc builds up until the maximum activity is reached (usually 4 half-lives)
Wet or dry column generators
Dry : after elution, the leftover saline in the column is drawn out with vial
4 half-lives is 24 hours = for maxiumum buildup

23. ~QC testing ~ 99Mo Breakthrough
Radionuclide purity
Molybdemum contamination in the elution
Limit:
0.15 uCi of 99Mo / 1 mCi of 99mTc

24. ~QC testing~ Aluminum Breakthrough
Aluminum contamination
Limit
10 ug Aluminum ion / ml 99mTc eluate
Aluminum interferes with tagging sulfur colloid and RBC’s

25. ~QC testing~ pH
Should be between 4.5 and 7.5