Answer to Question #6043 Submitted to "Ask the Experts"

Q

I would like to make a comparison among x-ray machines to show the relative level of danger associated with the beams they create. I would like to do this by comparing the dose rates given by the x-ray beams of various machines. I've had a hard time finding this information. Could you suggest where I might be able to find information for typical x-ray beam dose rates for machines used for airport baggage scanners, cargo scanners, medical x ray (that is, chest x ray), and cancer treatment (that is,  betatron type >1 MeV range machines)?

A

In answer to your question on the various dose rates from a variety of x-ray and gamma ray devices, I would recommend the following references:
For cargo and passenger screening devices:

1. Hupe O, Ankerhold U. Determination of ambient and personnel dose equivalent for personnel and cargo security screening. Radiation Protection Dosimetry 121(4):429-37; 12 May 2006 (Abstract URL: http://rpd.oxfordjournals.org/cgi/content/abstract/ncl047v1)

2. Kassiday D. Radiation protection activities related to security products that use ionizing radiation, Presentation at the 2004 annual meeting of the CRCPD. Available at: http://www.crcpd.org/AnnualMeeting-04/05-25-04_1330_Kassiday.pdf

3. Khan SM, Nicholas PE, Terpilak MS. Radiation dose equivalent to stowaways in vehicles. Health Physics Journal 86(5):483-92; May 2004 (Abstract URL: http://www.ncbi.nlm.nih.gov/entrez/ query.fcgicmd=Retrieve&db=PubMed&list_uids=15083143&dopt=Abstract)

4. NCRP Commentary No. 16 - Screening of humans for security purposes using ionizing radiation scanning systems. NCRP Publications 2003 http://www.ncrppublications.org/index.cfm? fm=Product.AddToCart&pid=8182473315

For diagnostic medical applications I would recommend:

5. US Food and Drug Administration, Nationwide Evaluation of X-ray Trends (NEXT) Survey Data http://www.fda.gov/cdrh/radhealth/next-datasum.html

6. Conference of Radiation Control Program Directors (CRCPD) NEXT Survey Data http://www.crcpd.org/NEXT.asp

For therapeutic medical applications, linear accelerators can generate dose rates as high as 10 Gy/min (1,000 rad/min) at the isocenter, usually located at 1 meter from the focal source. However, clinical dose rates are usually around 2 to 6 Gy/min (200 to 600 rad/min). The typical daily dose to a tumor volume is about 2 to 6 Gy/day (200 to 600 rad/day) and total tumor dose ranges between 20 to 100 Gy (2,000 to 10,000 rad).

7. The US Department of Energy, Office of Science, has developed a nice chart in both SI and traditional units which you might also find helpful. Available at: http://lowdose.tricity.wsu.edu/resources_pics/images/Dose-Ranges-pdf.pdf

Mike Bohan, RSO
Yale-New Haven Hospital