The National Council of Radiation Protection and Measurements
Report No. 49, originally issued on September 15, 1976, has been the
primary design guide for diagnostic x-ray structural shielding in the
United States. To further protect the public from various areas of
medical radiation exposure, NCRP issued Report 116 in 1987 to
decrease the public exposure limits. These new limits used in
conjunction with NCRP 49 to determine shielding requirements for
diagnostic radiological rooms can be shown to over-shield based on
current technologies and protocols.
This paper explores the NCRP conservative assumptions that
physicists specifying barrier requirements for diagnostic x-ray facilities
normally utilize. These evaluated assumptions, which are incorporated
in the methodology and attenuation data presented in NCRP Report 49
formulas, include relatively high single kVp's, a "one size fits all"
workload default, and the lack of attenuation factors by the patient, the
wall, and the film. In essence, an analysis of the conservative nature of
NCRP 49 is demonstrated.
An example of Primary and Secondary Shielding Methodology
utilizing NCRP 49 and NCRP 116 dose limits is provided as well as the
cost factors associated with the results. These examples are further
evaluated using a Monte Carlo software program.
In addition, an analysis of actual current radiographic conditions
in an imaging room is performed. This is done to determine first, the
actual mA utilized for specific exams; secondly, the actual mA-min
weekly workload; and thirdly, the tangible exams performed per week
in small and large medical facilities.
Based on the information and analysis presented, this paper
concludes that the formulas for NCRP 49 and NCRP 116 need to be
reexamined. Furthermore, this paper also demonstrates once again
that NCRP 49, utilizing NCRP 116 dose limits is extremely
conservative. / Graduation date: 2004
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/30865 |
| Date | 11 December 2003 |
| Creators | Mallory, Stacy L. |
| Contributors | Hamby, David M. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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