:: dosimetry and scanner testing
There are a number of pages relating to CT scanner dosimetry and scanner testing on the ImPACT web site.
ImPACT co-ordinated a nationwide database of scanner dose characteristics. Results from this work include a summary article on the methods used, originally produced for RAD magazine. Scanner matching data and tables of CTDI for a wide range of scanners are available, including information on relative values of CTDI100 and CTDIFDA. The data has been combined in the ImPACT CT dosimetry spreadsheet system which allow Monte Carlo based dosimetry techniques to be used for even the most modern CT equipment. This spreadsheet alows the estimation of effective doses to patients from CT examinations.
ImPACT produce CTDI phantoms for measurement of CT dosimetry characteristics.
We have produced a document on acceptance testing of CT scanners, which puts an emphasis on pratical information and considerations for multi-slice scanners.
This report replaces IPEM Report 77 and provides essential guidance for anyone responsible for diagnostic X-ray equipment. This document gives clear advice on which routine performance tests are essential and which are desirable, where to get information on how to do them, who should be doing them and how often they should be done. For many tests it also gives guidance as to when the results indicate further action should be taken. This second edition takes into account the introduction of new technologies in medical imaging including CR, DDR and image display devices.
Chapter 12 covers the topic of Computed Tomography; the preface to this chapter reads
Since the publication of IPEM Report 77 (IPEM, 1997a), the performance of regular simple QC tests has become the norm. However, the technological developments that have taken place in CT scanners have introduced more complexity, with implications for more detailed testing as performed by Medical Physics Departments. During 2002, the CT Users Group conducted a survey of diagnostic CT QA practice in the UK and Ireland. The aim of the survey was to establish a consensus on core performance tests carried out by Medical Physics Departments during routine testing of a CT scanner. The survey results were used to form the basis of the revision of this chapter. Further discussion with CT Users Group members together with advice from ImPACT has tailored recommendations to reflect the importance of certain tests in the context of constancy testing in a limited amount of time. For the majority of the tests described, it will be sufficient to acquire and evaluate the images using a sequential (axial) scan for both single and multislice scanners. The IPEM (2003) reference (Report 32 part III) gives advice on the appropriateness of spiral mode for each test. The tests describe diagnostic CT tests, and consideration should be given to further tests if the scanner is used for radiotherapy purposes. Guidance is given in IPEM Report 81 Physics Aspects of Quality Control in Radiotherapy (IPEM,1999).
IPEM 91 and other reports can be purchased from the IPEM web site