Converting Dose-Length Product to Effective Dose at CT
- 1 September 2008
- journal article
- Published by Radiological Society of North America (RSNA) in Radiology
- Vol. 248 (3), 995-1003
- https://doi.org/10.1148/radiol.2483071964
Abstract
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. © RSNA, 2008Keywords
This publication has 21 references indexed in Scilit:
- National survey of doses from CT in the UK: 2003The British Journal of Radiology, 2006
- Assessment of tube current modulation in pelvic CTThe British Journal of Radiology, 2006
- Assessment of a theoretical formalism for dose estimation in CT: an anthropomorphic phantom studyEuropean Radiology, 2004
- National Conference on Dose Reduction in CT, with an Emphasis on Pediatric PatientsAmerican Journal of Roentgenology, 2003
- CT-Expo - ein neuartiges Programm zur Dosisevaluierung in der CTRöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, 2002
- Managing patient dose in computed tomographyAnnals of the ICRP, 2000
- CT scanning: patterns of use and doseJournal of Radiological Protection, 2000
- Calculation of effective doseMedical Physics, 2000
- Radiation dosimetry in diagnostic radiology.American Journal of Roentgenology, 1997
- Potential Biological Effects Following High X-ray Dose Interventional ProceduresJournal of Vascular and Interventional Radiology, 1994