Generators

Types of generators (e.g., 99Mo/99mTc, 82Sr/82Rb) a. Transient and secular b. Eluate c. Generator yield – volume and activity d. Quality control procedures i. Radionuclidic breakthrough (e.g., 99Mo breakthrough) ii. Chemical (e.g., Al+3 breakthrough) 2. Dose calibrator operation /units of radioactivity

What are the two most common radionuclide generators used in nuclear medicine?

Mo-99/Tc-99m generator and Sr-82/Rb-82 generator

What is the parent radionuclide in a Mo-99/Tc-99m generator?

Mo-99

What is the daughter radionuclide in a Mo-99/Tc-99m generator?

Tc-99m

What is the parent radionuclide in a Sr-82/Rb-82 generator?

Sr-82

What is the daughter radionuclide in a Sr-82/Rb-82 generator?

Rb-82

What type of equilibrium does a Mo-99/Tc-99m generator demonstrate?

Transient equilibrium

What type of equilibrium does a Sr-82/Rb-82 generator demonstrate?

Secular equilibrium

What is transient equilibrium?

Parent half-life is longer than daughter half-life but not extremely longer (approximately 10–50 times longer)

What is secular equilibrium?

Parent half-life is much longer than daughter half-life (>100 times longer)

What is the half-life of Mo-99?

66 hours

What is the half-life of Tc-99m?

6.02 hours

What is the half-life of Sr-82?

25 days

What is the half-life of Rb-82?

76 seconds

What is the half-life of Ge-68?

271 days

What is the half-life of Ga-68?

68 minutes

What is elution?

The process of removing the daughter radionuclide from a generator using an eluent solution

What is eluate?

The radioactive solution collected after elution containing the daughter radionuclide

What radionuclide is contained in Mo-99/Tc-99m generator eluate?

Tc-99m sodium pertechnetate (TcO4-)

What solution is used to elute a Mo-99/Tc-99m generator?

Sterile 0.9% sodium chloride (normal saline)

What column material is used in a Mo-99/Tc-99m generator?

Alumina

Where is Mo-99 concentrated in a generator?

On the alumina column

Why can Tc-99m be separated from Mo-99?

Tc-99m is less tightly bound to the alumina column and can be washed off with saline

What is generator yield?

The amount of daughter radionuclide activity obtained from an elution

What factors affect generator yield?

Time since last elution, parent activity, and elution volume

When is maximum Tc-99m generator activity available after elution?

Approximately 23–24 hours after previous elution

What happens to Tc-99m activity immediately after elution?

Tc-99m begins building back up from Mo-99 decay

What is a "milking" of a generator?

The process of eluting the daughter radionuclide from the generator

What is a dry column generator?

A generator where the daughter radionuclide is removed with a small amount of liquid and the column remains relatively dry

What is a wet column generator?

A generator where the column remains filled with liquid during storage and elution

What is a positive pressure generator?

A generator system where pressure pushes eluate through the column

What is a negative pressure generator?

A generator system where vacuum assists in drawing eluate through the column

What is radionuclidic breakthrough?

The presence of unwanted parent radionuclide in the daughter eluate

What is an example of radionuclidic breakthrough?

Mo-99 breakthrough in Tc-99m eluate

What is the acceptable Mo-99 breakthrough limit?

≤0.15 µCi Mo-99 per mCi Tc-99m

Why is Mo-99 breakthrough a concern?

It increases patient radiation dose due to higher-energy gamma emissions

When should Mo-99 breakthrough testing be performed?

After the first elution

What is chemical breakthrough?

The presence of non-radioactive contaminants from the generator column

What is an example of chemical breakthrough?

Aluminum (Al3+) breakthrough

Where does aluminum breakthrough originate?

Alumina column material

What is the acceptable aluminum breakthrough limit?

≤10 µg Al/mL eluate

How is aluminum breakthrough tested?

Aluminum ion test strip

What is the purpose of generator quality control testing?

To ensure eluate purity, patient safety, and proper radiopharmaceutical labeling

What QC tests are performed on generator eluate?

Radionuclidic purity, chemical purity, radiochemical purity, pH, and appearance

What is radionuclidic purity?

The percentage of total activity that is the desired radionuclide

What is chemical purity?

The absence of unwanted non-radioactive substances

What is radiochemical purity?

The percentage of radioactivity present in the desired chemical form

What is the parent of Tc-99m?

Mo-99

What is the parent of Rb-82?

Sr-82

What is the parent of Ga-68?

Ge-68