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Radiation exposure to human trachea from xenon-133 procedures
I Prohovnik1, C D Metz, H L Atkins
1Department of Brain Imaging, New York State Psychiatric Institute, New York 10032, USA.
Summary
Radiation exposure to tracheal tissue from 133Xe inhalation or intravenous injection is low. This study quantizes Xenon-133 (133Xe) respiratory concentrations and calculates tracheal absorbed doses, confirming safety for human studies.
Area of Science:
- Nuclear Medicine
- Medical Physics
- Radiology
Background:
- Dosimetry of Xenon-133 (133Xe) for human studies is established.
- Radiation exposure to tracheal tissue from 133Xe is not well-characterized.
- Tracheal tissue is relevant due to primary elimination of 133Xe via exhalation.
Purpose of the Study:
- To determine actual 133Xe concentrations in respiratory air during regional cerebral blood flow (rCBF) measurements.
- To calculate the radiation absorbed dose to tracheal tissue following 133Xe administration.
- To assess the safety margin of 133Xe procedures.
Main Methods:
- Measured 133Xe respiratory concentrations in 102 patients undergoing rCBF studies.
- Administered 133Xe via inhalation (18 ± 4 mCi) and intravenous injection (15 ± 3 mCi).
- Calculated tracheal absorbed dose based on measured respiratory activity over 11 minutes.
Main Results:
- Average respiratory 133Xe concentrations were 1.80 mCi/L (inhalation) and 0.74 mCi/L (IV) during the first minute.
- Tracheal absorbed dose was approximately 28 mrad (inhalation) and 11 mrad (IV).
- Activity levels decreased rapidly, reaching negligible levels shortly after administration.
Conclusions:
- Calculated tracheal absorbed doses for 133Xe procedures are low.
- These findings indicate an excellent safety margin for 133Xe use in human studies.
- The results align with previous dosimetry estimates for 133Xe.