The challenges of quantitative measurement of lung deposition using 99mTc-DTPA from delivery systems with very different delivery times.
In quantifying aerosol delivery, the drug is often mixed with a radiolabel such as (99m)Tc-DTPA whose deposition is used as a proxy for the drug. (99m)Tc-DTPA deposited in the lung is cleared by a combination of absorption into the pulmonary circulation and mucociliary clearance. If administration is not instantaneous, the image will not include that clearance during administration, a problem raised if comparing devices with different administration times. However, if rates of clearance are measured, it will be possible to "correct" the initial image for the clearance that occurred during administration and before counting. Five adult males inhaled a 5-mL solution containing (99m)Tc-DTPA from a breath enhanced jet nebulizer (LC Plus)over the course of 10 min and a 1.25-mL solution from a vibrating membrane device (eFlow), which was delivered in 2.5 min. Quality assurance was the radioactivity count balance (RCB) defined as the difference in the total radioactivity pre-nebulization less post, divided by pre, and expressed as a percentage. Attenuation calculations used a (57)Co flood source (Macey and Marshall). The "correction" for the clearance of (99m)Tc-DTPA was 0.91 +/- 0.04 (mean +/- SD) for the LC Plus) and 0.96 +/- 0.02 for the eFlow). RCB was -0.6 +/- 3.5% for the LC Plus and -4.7 +/- 6.4% for the eFlow, implying acceptable accuracy. For the LC Plus, lung deposition was 15.9(13.4, 18.4)% (mean and 95% CI) of the charge dose, and for the eFlow it was 32.0(29.0, 35.0)%. This technique gave an acceptable level of accuracy for quantitative planar imaging and allowed the comparison of delivery from devices with very different rates of delivery.
Coates
Allan L
AL
The Lung Biology Program, Research Institute of the Hospital for Sick Children, University of Toronto, Toronto, Canada. allan.coates@sickkids.ca
Green
Maria
M
Leung
Kitty
K
Louca
Emily
E
Tservistas
Markus
M
Chan
Jeffrey
J
Ribeiro
Nancy
N
Charron
Martin
M
D000280:Administration, Inhalation; D000328:Adult; D000336:Aerosols; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D016503:Drug Delivery Systems / Q000295:instrumentation*; D004867:Equipment Design; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008168:Lung / Q000000981:diagnostic imaging* / Q000378:metabolism; D008297:Male; D009330:Nebulizers and Vaporizers; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000008:administration & dosage*; D016284:Technetium Tc 99m Pentetate / Q000008:administration & dosage*; D013678:Technology, Pharmaceutical / Q000379:methods*; D013997:Time Factors; D014031:Tobramycin / Q000008:administration & dosage* / Q000378:metabolism; D014732:Vibration
D000336:Aerosols; D000900:Anti-Bacterial Agents; D019275:Radiopharmaceuticals; D016284:Technetium Tc 99m Pentetate; D014031:Tobramycin