What's New?
.	Fukushima Decontamination Report
.	CRCPD & CDC Grants for Volunteer Corps
.	America's Nuclear Future
.	February Newsletter
.	Boice Nominated President of NCRP
.	February Journal
.	February ORS
.	Schauer Given the Butterfly Award from Image Gently
.	Kase President's Report to IRPA
.	IRPA13 Accepting Posters

Upcoming Events
.	HPS Midyear - Issues in Waste Management 5-8 February 2012 Dallas, Texas
.	NRC Regulatory Information Conference NRC Regulatory Information Conference 13-15 March 2012 Rockville, Maryland
.	NCRP Annual Meeting 12-13 March 2012 Washington, DC
.	James E. Turner Memorial Symposium Call for Abstracts 18-19 April 2012 Oak Ridge Associated Universities, Pollard Auditorium, Oak Ridge, Tennessee
.	IRPA13 13-18 May 2012 Glasgow, Scotland
.	Canadian Radiation Protection Association (CRPA) Annual Meeting 27-30 May 2012 Halifax, Nova Scotia
.	ACS Undergrad Summer Schools 10 June- 20 July 2012
.	Nuclear Regulatory Commission Meeting Webcasts February 2012 Bethesda, Maryland

09 February 2012

Answer to Question #1035 Submitted to "Ask the Experts"

Category: Nuclear Medicine Patient Issues — Diagnostic Nuclear Medicine

The following question was answered by an expert in the appropriate field:

What is the effective half-life of ^99mTc MAA when used for a lung V/Q scan in Nuclear Medicine?

If you are talking about injection of ^99mTc MAA (what is commonly suggested by the definition of the scan you mentioned), International Commission on Radiatiological Protection (ICRP) Publication 53 gives a rather complicated picture. The injected activity is taken up by the lungs, with 85 percent of the material having a six-hour biological half-time (three-hour effective half-time) and 15 percent having a three-day biological half-time (about a 5.5 hour effective half-time). There is some uptake of the released material by the liver (25 percent of the total, being held up there with a five-day biological, or a 5.7-hour effective, half-time). Some of the material entering the lung or liver, as well as any Tc that may have detached from the MAA, will be excreted from the body through the kidney/bladder pathway. Overall, the whole body effective half-time appears to be about 5.3 hours. If you are referring instead to inhalation of Tc aerosols (which could be done with DTPA, MAA, pertechnetate, or other compounds), the kinetic picture is quite different, but also covered in ICRP 53 if needed.

Michael G. Stabin, CHP, PhD

Answer posted on 3 August 2001. The information and material posted on this website is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Website. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.