Improved counting efficiencies for measuring 239Pu in the lung in the sitting position

Area of Science:

• Nuclear physics
• Radiological protection
• Medical imaging

Background:

• Accurate lung deposition measurements are crucial for assessing internal radiation exposure.
• Previous lung counting techniques faced challenges with variable body positions affecting detector efficiency.

Purpose of the Study:

• To quantify the impact of body positioning on lung counting efficiency for inhaled radionuclides.
• To compare the effectiveness of Ge planar and Phoswich detector systems in different positions.

Main Methods:

• Lung deposition measurements of 92mNb were performed on 10 women in supine and sitting positions.
• Two detector systems, Ge planar and Phoswich, were utilized for counting.
• Chest wall thickness was measured to correlate with counting efficiency changes.

Main Results:

• Sitting position increased counting efficiency by an average of 108% (Ge) and 310% (Phoswich) compared to supine.
• Individual efficiency gains ranged from 15-260% (Ge) and 40-480% (Phoswich).
• Efficiency increase correlated with chest wall thickness, suggesting reduced tissue absorption and improved geometry.

Conclusions:

• The sitting position significantly enhances lung counting efficiency for inhaled radionuclides.
• Phoswich detectors showed a more substantial improvement in efficiency than Ge detectors with positional changes.
• Chest wall thickness and source-to-detector geometry are key factors influencing lung counting accuracy.