99m-Tc RP QC P I Flashcards
Describe chemical purity
● Presence of undesirable nonradioactive chemical species in radiopharmaceuticals
○ i.e. Fraction of the material in the desired chemical form, whether labeled or not
- Al3+ breakthrough test
Chemical impurities are due to:
○ Breakdown of material before or after labeling
○ Unintentionally added during the labeling process
Al3+ breakthrough test
○ Performed prior to using eluate for injecting patients or preparing RPs
○ <10 ug Al3+/ml of eluate
Radioassay QC
● The total amount of activity that is measured on the 99mTc setting in the dose
calibrator
● The specific concentration of the RP is determined
○ Activity / Total Volume = mCi/ml or MBq/ml , etc.
● Label the ‘bulk vial’ of RP appropriately to include:
○ Name of RP
○ Calibration Date and Time
○ Lot #
○ Total Activity and Volume
○ Specific Concentration
○ Expiry Time
Radionuclidic purity QC
▪ Fraction of the total radioactivity in the source that is in the form of the desired
radionuclide
▪ Ie. only desire 99mTc in the eluate
▪ CNSC: Ratio of 99Mo to 99mTc must be < 0.03 uCi 99Mo per mCi of 99mTc to pass
Moly Breakthrough testing
▪ (can also be expressed as kBq/MBq)
▪ This limit is <0.15 uCi 99Mo/ mCi 99mTc as per US Pharmacopoeia (USP)
Radiochemical purity
▪ Fraction of the total radioactivity present in the desired chemical form
▪ Expressed as a percentage
▪ The % of 99mTc tagged (bound) to the
pharmaceutical
▪ Test is routinely determined by in vitro analytic methods
▪ Instant thin layer/paper Chromatography (ITLC)
▪ Column chromatography
▪ i.e. Sep-pak
Radiochemical purity QC
▪ Performed prior to releasing the RP for patient injection
▪ Most 99mTc RPs:
▪ ≥ 90% bound (radiochemical purity)
▪ If less than this amount, repeat
testing
▪ If fails again, discard kit and prepare a new one
Visual inspection
- color
- clarity
- particulate matter
Normal appearance of RPs
▪ MAA – cloudy/turbid, white (particles)
▪ Sulfur Colloid – slightly turbid, milky
▪ HMPAO – clear, blue (methylene blue) or amber (cobalt stabilizer)
▪ 131I-NaI – clear, amber (with time)
▪ All others: Clear and colorless
Particle sizing
○ MAA (by NM technologists)
○ SC (by manufacturer)
■ Average size: 100 – 1000 nm
■ Filtered SC: < 100-220 nm
MAA particle sizing
○ Use light microscope and hemocytometer
○ Confirms the particles are evenly dispersed and correct size
○ Should be between 10-90 um with none >150 um
○ If particles are not of proper size, do not use preparation
MAA particle count
○ Count the # of particles in the central square (400 squares)
■ Count only those touching the bottom and left sides to ensure uniformity
of the procedure in counting the particles on the line between squares
○ Calculate the # of particles per ml using the following formula:
■ # particles per ml = # particles x 1000 mm3
● 0.1 mm3 = 1 ml
■ Total # of particles = # particles x total volume of kit
- Depends on the physical decay
- normal: 400k
Why should MAA be diluted to decrease particle size/dose
■ 40 000 - 60 000 particles/dose:
● Pediatrics
■ 100 000-200 000 particles/dose:
● Pulmonary hypertension
● R → L shunts
● Pneumonectomy
● Pregnant patients
pH
▪ All RPs have an appropriate pH for their integrity and
stability
▪ Ideal pH: 7.4 (pH of blood) but varies between 2 and 9
▪ Most accurate method is to use a pH meter, however
pH paper is more commonly available
▪ pH paper uses colorimetric method
Stannous concentration
▪ Allows for the measuring of stannous levels (reducing agent) present in RPs
▪ Useful to know when labeling RBCs with PYP
▪ Not routinely performed
▪ Procedure:
▪ Place a drop of RP on stannous indicator paper
▪ Compare the intensity of the blue spot formed by the sample to a color chart
