What's New?
.	HPS and CRCPD Proclaim 8-14 November 2009 as National Radiation Protection Professionals Week
.	November Newsletter
.	NRC Academic Program Nuclear Education Grants, FY2010, Now Accepting Applications
.	November ORS
.	November Journal
.	EPA's STAR Graduate and GRO Undergraduate Fellowship Funding Now Accepting Applications

Upcoming Events
.	2010 HPS Midyear Topical Meeting Radiation Risk Communication to the Public 24-27 January 2010 Albuquerque, NM
.	2010 HPS Professional Development School Radiation Risk Communication: Issues and Solutions 27-29 January 2010 Albuquerque, NM

07 November 2009

Answer to Question #4743 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Diagnostic X Ray and CT

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

I had two head/brain CT scans in January (one week apart) for a sinus infection. I had the second one because my doctor wanted to see the sinuses only but the radiologist went ahead and took my whole head/brain. I called the radiologist at the CT scan department and the radiologist didn't know the amount of radiation that was given. I searched online and found different doses. Can you tell me the amount of radiation dosage for a head/brain CT scan? The CT scan was done at the hospital.

It is not unusual to see different dose numbers cited by different investigators for CT or other radiologic exams. The doses will vary considerably, depending on the machine and technique used. In ICRP Publication 62, a representative value of 1.8 mSv (180 mrem) effective dose is given for a head CT. That seems to be a reasonable representation for values I have seen on a number of machines at our institution. Now, this dose is a risk-weighted effective total-body dose (see a frequently asked question answer on the Health Physics Society Web site for more detail). As a head CT does not involve many body organs in the exposed field, the risk weighting factors involved are low. Thus some of the individual tissue in the head area may receive several times this dose value, but the weighted total body average is as shown. For comparison, an average American receives about 3.0 mSv (300 mrem) effective dose from exposure to natural background radiation each year.

Michael G. Stabin, PhD, CHP

Answer posted on 31 August 2005. The information and material posted on this Web site 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 Web site. 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.