A simple radioaerosol generator and delivery system for pulmonary ventilation studies

Details of a simple radioaerosol generator and delivery system are presented. Aerosol streams of 99mTc-DTPA solution of different distributions were produced. The most useful distribution had an activity median aerodynamic diameter (AMAD) of 0.9 micron with a geometric standard deviation of 1.5. This distribution also had more than 96% of aerosol particles with aerodynamic diameter less than 2 micron. The system has been used for patient lung ventilation studies. The aerosol breathing-in period to achieve a satisfactory count rate was 1.8 +/- 0.38 min. The radioaerosol images were excellent and comparable to those obtained with 81mKr gas.     

A rapid method for the evaluation of diagnostic radioaerosol delivery systems

The effective delivery (ED) in MBq/min of a 100 MBq/ml nebuliser solution was defined as the rate of delivery of droplets in the respirable size range (aerodynamic diameter below 3.3 m) to the mouthpiece of the aerosol delivery system (ADS). Wasted delivery (WD) was defined as the rate of delivery of droplets above 3.3 m. ED and WD were measured on four types of commercially available ADS. The aerosols were sampled at the mouthpiece of each system and droplet size distribution measured with a seven stage cascade impactor. The effect of ambient air humidity on the droplet size produced by the Cadema delivery system was also evaluated. The ED values ranged from 6 to 15 MBq/min and WD values from 0.01 to 15 MBq/min. Two ADS produced low ED and WD values (6.1–9.0 and 0.01–0.07 MBq/min, respectively) due to a low output, while another produced higher ED and WD values [11.3±0.2 (SD) and 15.4±0.5 (SD) MBq/min, respectively] due to a larger droplet size. The Cadema delivery system gave the optimum characteristics of high ED [13.9±0.8 (SD) MBq/min] and low WD [1.24±0.61 (SD) MBq/min] values. The mass median aerodynamic diameter (MMAD) of the Cadema ADS fell by 22% (P< 0.01) as the ambient dilution air was dried from a high relative humidity (RH) (88%–100%) to a low RH (12%–17%). The variability of both MMAD and geometric standard deviation (g) was increased with dry dilution air (P< 0.01).     

A rapid method for the evaluation of diagnostic radioaerosol delivery systems

The effective delivery (ED) in MBq/min of a 100 MBq/ml nebuliser solution was defined as the rate of delivery of droplets in the respirable size range (aerodynamic diameter below 3.3 micron) to the mouthpiece of the aerosol delivery system (ADS). Wasted delivery (WD) was defined as the rate of delivery of droplets above 3.3 microns. ED and WD were measured on four types of commercially available ADS. The aerosols were sampled at the mouthpiece of each system and droplet size distribution measured with a seven stage cascade impactor. The effect of ambient air humidity on the droplet size produced by the Cadema delivery system was also evaluated. The ED values ranged from 6 to 15 MBq/min and WD values from 0.01 to 15 MBq/min. Two ADS produced low ED and WD values (6.1-9.0 and 0.01-0.07 MBq/min, respectively) due to a low output, while another produced higher ED and WD values [11.3 +/- 0.2 (SD) and 15.4 +/- 0.5 (SD) MBq/min, respectively] due to a larger droplet size. The Cadema delivery system gave the optimum characteristic of high ED [13.9 +/- 0.8 (SD) MBq/min] and low WD [1.24 +/- 0.61 (SD) MBq/min] values. The mass median aerodynamic diameter (MMAD) of the Cadema ADS fell by 22% (P less than 0.01) as the ambient dilution air was dried from a high relative humidity (RH) (88%-100%) to a low RH (12%-17%). The variability of both MMAD and geometric standard deviation (sigma g) was increased with dry dilution air (P less than 0.01).     

A high efficiency ultrasound nebuliser for radioaerosol studies of the lungs

An ultrasound nebuliser with variable delivery temperature and nebulisation volume was tested for particle size distribution, efficiency, and application in a clinical environment. The results obtained comply with our criteria for a general purpose radioaerosol generating system for use in evaluating various parameters of lung function.     

A high efficiency ultrasound nebuliser for radioaerosol studies of the lungs

An ultrasound nebuliser with variable delivery temperature and nebulisation volume was tested for particle size distribution, efficiency, and application in a clinical environment. The results obtained comply with our criteria for a general purpose radioaerosol generating system for use in evaluating various parameters of lung function.     

Lung ventilation scanning with a new carbon particle radioaerosol (Technegas). Preliminary patient studies

A new Tc-99m labeled carbon particle aerosol ("Technegas") has been developed for lung ventilation scanning. This is the first reported clinical study of this agent in the United States. A total of 23 subjects were studied. Thirteen had comparative Xe-133 studies, and in seven patients pulmonary angiograms were available. The Technegas study agreed closely with the Xe-133 results in 10 out of 13 patients, while the pulmonary angiogram confirmed the Technegas and perfusion scan findings in seven out of seven cases. The Technegas scan was easily performed and well tolerated by all patients. If further clinical trials confirm these preliminary findings, Technegas may become the preferred agent for lung ventilation scanning.     

Mechanical delivery of aerosolized gadolinium-DTPA for pulmonary ventilation assessment in MR imaging

RATIONALE AND OBJECTIVES: To evaluate a new technique with mechanical administration of aerosolized gadolinium (Gd)-DTPA for MR visualization of lung ventilation. METHODS: Ten experimental procedures were performed in six domestic pigs. Gd-DTPA was aerosolized by a small-particle generator. The intubated animals were mechanically aerosolized with the nebulized contrast agent and studied on a 1.5-T MR imager. Respiratory gated T1-weighted turbo spin-echo images were obtained before, during, and after contrast administration. Pulmonary signal intensity (SI) changes were calculated for corresponding regions of both lungs. Homogeneity of aerosol distribution was graded independently by two radiologists. RESULTS: To achieve a comparable SI increase as attained in previous trials that used manual aerosol ventilation, a ventilation period of 20 minutes (formerly 30 minutes) was sufficient. Mean SI changes of 116% were observed after that duration. Contrast delivery was rated evenly distributed in all cases by the reviewers. CONCLUSIONS: The feasibility of applying Gd-DTPA as a contrast agent to demonstrate pulmonary ventilation in large animals has been described before. The results of this refined technique substantiate the potential of Gd-based ventilation MR imaging by improving aerosol distribution and shortening the nebulization duration in the healthy lung.     

Improved radioaerosol administration system for routine inhalation lung imaging.

An improved radioaerosol administration system has been developed to reduce the number of droplets larger than 2.0 micron in diameter which have caused abnormal hyperdeposition of inhaled aerosols in the large airways. The new system has achieved this goal by interposing a reservoir-setting bag in the aerosol delivery line between the nebulizer and the patient. The components are inexpensive, commercially available and easily assembled in any nuclear medicine service.     

81mKr gas generator for lung ventilation study

A generator of ^81mKr was designed and tested. The parent nuclide ⁸¹Rb was produced by the 70 MeV proton induced reactions on a Rb₂SO₄ target. ^81mKr was bubbled out with oxygen gas from the ⁸¹Rb solution, and collected in a reservoir for lung ventilation studies. The generator was continuously operated at the high flow rate up to 101/min. The generator efficiency was 86%. The collection rates in the reservoir were examined under several flow rates. The pure ^81mKr isomer was observed with a NaI (T1) detector at the reservoir.     

Xe-133 rebreathing system for ventilation studies on ventilator-assisted patients

We describe a manually operated system, simple to assemble, that will enable xenon-133 lung ventilation studies to be performed on ventilator-assisted patients. It can be constructed from items readily available. Radiation exposure levels to the operator were measured and are reported.     

Microbiological and radioactive contamination from radioaerosol ventilation scanning: is there a problem?

Radioaerosol lung imaging may result in (a) microbiological contamination of nebulizer circuits (a potential hazard to patients if the circuit is re-used), and (b) radioaerosol contamination of the atmosphere (a hazard to staff, particularly if inhaled, ingested or both). Altogether, 138 circuits were assessed for bacteriological contamination, 93 of which had been used for ventilation perfusion studies and 45 for lung permeability studies in human immunodeficiency virus (HIV) positive patients. The circuits used for ventilation/perfusion (V/Q) studies were re-used over a period of 1-5 days. The mouthpiece and Y-piece were changed between patients. The circuits used for permeability studies were changed in toto for each patient. Organisms belonging to normal respiratory flora were isolated from the Y-piece, mouthpiece or both in 9 of 138 cases. An additional case (from one of the HIV-positive patients) demonstrated a growth of methicillin-resistant Staphylococcus. We also demonstrated bacteriological growth, most likely of patient origin, in circuit tubing in 11 cases at the end of the first day's use and 9 cases by day 5. None of the circuits used for HIV-positive cases were culture-positive. Airborne radioactive contamination was assessed during radioaerosol inhalation with and without an air extractor device (Nederman) during 40 ventilation studies. The 20 studies with air extraction showed a large decrease in room air contamination. Nebulizer circuits can, and occasionally do, become contaminated with patients' organisms; this represents a potential infection control hazard and therefore re-use is contraindicated. The use of an air extractor will significantly reduce airborne radioaerosol contamination.     

Carbon dioxide angiography: a simple and safe system of delivery

Carbon dioxide (CO2) is an established alternate angiographic contrast agent, which can be delivered by pump or hand injection. We describe a simple, safe and inexpensive hand injection system that delivers a known volume of CO2 at atmospheric pressure and prevents contamination with room air.     

A simple dosimetry system for nuclear accidents

The paper describes a simple and inexpensive Nuclear Accident Dosimetry system for use in criticality accidents. It consists of activation detectors of gold, copper, indium and sulphur for neutron dose estimation and a suitable thermoluminescent material for gamma dose measurements. The method of interpreting the activation data for the derivation of neutron fluence and dose is described giving the actual calculations involved. The highly degraded neutron spectrum from the “Viper” reactor (Harwell, U.K.) provided a severe test of the system and the method of interpretation used and the results were very satisfactory.     

A simple classification system for mammographic reporting

A simple classification system for reporting mammograms is described, similar in format to a system formerly used for reporting Papanicolaou smears. Class 1 indicates an examination with normal findings. Class 2 indicates findings of a mass or masses that appear to be benign. Class 3 indicates findings of an indeterminate lesion, suggestive of possible malignancy. Class 4 indicates probable malignancy. Advantages of the classification system include effective triage of patients and easier computerized record keeping for long-term tracking.