Comparison of delivered and residual Technetium labeled Diethylenetriamine-pentaacetic acid when ventilating: corrugated vs. non-corrugated tubing

Objectives: The use of corrugated tubing during a lung aerosol exam results in the deposit of Technetium Diethylenetriamine-pentaacetic acid (Tc-DTPA) in the grooves of the tubing, reducing the amount of Tc-DTPA deposited in the lungs. This study examined whether non-corrugated tubing would allow more Tc-DTPA to be deposited into the lungs in comparison to the standard, corrugated tubing. An increase of Tc-DTPA delivered to the lungs could allow for a decrease in the prescribed dose, reducing the radiation exposure to patients and technologists. Methods: Utilizing the same ventilation kit, two non-clinical experiments were performed using corrugated and non-corrugated tubing. Three trials were conducted for each type of tubing. The length (68cm) and bore (2.3cm) of the tubing were held constant in each trial along with the activity (24.0 ±0.5mCi) and volume (4.0±0.1mL) of Tc-DTPA. An ambu bag was attached to the tubing during ventilation to simulate a lung reservoir and ensure a closed system. For each trial, the ventilation time was eight minutes with an oxygen flow of ten liters. Immediately following ventilation, the tubing and ambu bag were imaged on a gamma camera for two minutes, utilizing a Low Energy All Purpose collimator. The position of the tubing was held constant during ventilation utilizing a hand drawn outline of the tubing and ambu bag. Two regions were drawn for each trial, one around the tubing and the other around the ambu bag. During imaging, the boundaries of these regions were marked with cobalt markers. The regions were drawn six times and averaged to ensure accuracy. The counts of each region were recorded, and the corrugated and non-corrugated trials were compared. Results: The average counts yielded from the corrugated tubing and associated ambu bag regions were 112,655 and 320,228, respectively. The average counts yielded from the non-corrugated tubing and associated ambu bag regions were 45,119 and 701,835, respectively. Conclusions: This study proved that after ventilation, the non-corrugated tubing retained 149.7% less counts when compared to the corrugated tubing. In addition, the ambu bag attached to the non-corrugated tubing retained 119.2% more counts than the ambu bag attached to the corrugated tubing. A higher amount of Tc-DTPA delivered to the lungs would allow for a lower prescribed dose, while keeping the same image sensitivity. Further research should be conducted to see how much the prescribed dose of Tc-DTPA may be