Radiology Special Reports

Radiology Special Reports http://radiology.rsnajnls.org Radiology RSS feed -- recent Special Reports articles 1527-1315 Radiology 0033-8419 Radiology http://radiology.rsnajnls.org/icons/banner/title.gif http://radiology.rsnajnls.org <![CDATA[[Special Reports] Converting Dose-Length Product to Effective Dose at CT]]> http://radiology.rsnajnls.org/cgi/content/short/248/3/995?rss=1 Purpose: To determine effective dose (ED) per unit dose-length product (DLP) conversion factors for computed tomographic (CT) dosimetry.

Materials and Methods: A CT dosimetry spreadsheet was used to compute patient ED values and corresponding DLP values. The ratio of ED to DLP was determined with 16-section CT scanners from four vendors, as well as with five models from one manufacturer that spanned more than 25 years. ED-to-DLP ratios were determined for 2-cm scan lengths along the patient axis, as well as for typical scan lengths encountered at head and body CT examinations. The dependence of the ratio of ED to DLP on x-ray tube voltage (in kilovolts) was investigated, and the values obtained with the spreadsheet were compared with those obtained by using two other commercially available CT dosimetry software packages.

Results: For 2-cm scan lengths, changes in the scan region resulted in differences to ED of a factor of 30, but much lower variation was obtained for typical scan lengths at clinical head and body imaging. Inter- and intramanufacturer differences for ED/DLP were generally small. Representative values of ED/DLP at 120 kV were 2.2 µSv/mGy · cm (head scans), 5.4 µSv/mGy · cm (cervical spine scans), and 18 µSv/mGy · cm (body scans). For head scans, ED/DLP was approximately independent of x-ray tube voltage, but for body scans, the increase from 80 to 140 kV increased the ratio of ED to DLP by approximately 25%. Agreement in ED/DLP data for all three software packages was generally very good, except for cervical spine examinations where one software package determined an ED/DLP ratio that was approximately double that of the other two.

Conclusion: This article describes a method of providing CT users with a practical and reliable estimate of adult patient EDs by using the DLP displayed on the CT console at the end of any given examination.

]]> 2008-08-18 info:doi/10.1148/radiol.2483071964 Radiological Society of North America 3 248 1003 2008-09-01 995 Special Reports <![CDATA[[Special Reports] Effective Doses in Radiology and Diagnostic Nuclear Medicine: A Catalog]]> http://radiology.rsnajnls.org/cgi/content/short/248/1/254?rss=1 Medical uses of radiation have grown very rapidly over the past decade, and, as of 2007, medical uses represent the largest source of exposure to the U.S. population. Most physicians have difficulty assessing the magnitude of exposure or potential risk. Effective dose provides an approximate indicator of potential detriment from ionizing radiation and should be used as one parameter in evaluating the appropriateness of examinations involving ionizing radiation. The purpose of this review is to provide a compilation of effective doses for radiologic and nuclear medicine procedures. Standard radiographic examinations have average effective doses that vary by over a factor of 1000 (0.01–10 mSv). Computed tomographic examinations tend to be in a more narrow range but have relatively high average effective doses (approximately 2–20 mSv), and average effective doses for interventional procedures usually range from 5–70 mSv. Average effective dose for most nuclear medicine procedures varies between 0.3 and 20 mSv. These doses can be compared with the average annual effective dose from background radiation of about 3 mSv.

]]> 2008-06-19 info:doi/10.1148/radiol.2481071451 Radiological Society of North America 1 248 263 2008-07-01 254 Special Reports