:: ukrc 2002

The 2002 UK Radiological Congress (UKRC) was held at Wembley Exhibition Centre from 9-11 June 2002. ImPACT presented three papers at the Recent Developments in CT session at this meeting, the abstracts for the talks are as follows. Links to the slides in the talks follow each abstract title.

The new CT technology: what are the benefits? (view slides)

JF Barrett

Nearly all the CT scanners currently being purchased for UK hospitals are sub-second multi-slice models. Most can acquire 4 slices simultaneously, and may have the option of upgrading to 8, 16 or more slices in the future. Software packages are available which enable a variety of specialised scanning techniques to be performed, and some models incorporate dose-reduction features. Patients undergoing CT scans in these hospitals can expect to benefit in a number of ways from the new technology. Greater diagnostic accuracy may result from improvements in image quality, and a greater range of diagnostic capabilities is now available. Better patient comfort can be expected with faster scanning speeds and the need for less contrast. The high quality 3D images reconstructed from multi-slice acquisitions have important applications in subsequent surgical procedures. In addition, the advances in specialized techniques such as CT angiography, virtual endoscopy and gated cardiac imaging should spare some patients from having to undergo more invasive procedures. This presentation explores the technological developments which have brought about these potential benefits, investigates how far the potential is currently being realised, and examines the ways in which any drawbacks associated with the new technology are being addressed.

The Relationship Between Image Noise and Spatial Resolution of CT Scanners (view slides)

S Edyvean, N Keat, MA Lewis, JF Barrett and S Sassi

The established relationships that link CT scanner image noise and high contrast spatial resolution are based on early theoretical studies and state that noise squared is proportional to spatial resolution cubed. This is interpreted and applied in a variety of ways in text books, including being used to normalise parameters in low contrast detectability studies. The ImPACT group also use this relationship in their Q value, combining noise, dose and spatial resolution data for standard resolution scans. An integral part of an ImPACT scanner assessment is the investigation of the inter-relationship of imaging performance indicators over a wide range of scanning and reconstruction parameters. In this paper an empirical exploration of the relationship between image noise and spatial resolution is presented. This data demonstrates that the established power relationship is most closely followed in the range of standard resolution algorithms. When the full range of convolution kernels are considered, however, a higher power relationship exists.

Assessment of the Low Contrast Detectability of Multi-slice CT Scanners (view slides)

N Keat, MA Lewis, JF Barrett, S Edyvean

The assessment of parameters such as image noise, limiting spatial resolution, z-axis sensitivity and patient dose are well established, repeatable and objective methods of assessing and comparing CT scanner images. However, these techniques only tell part of the story that also includes the uncertainties involved in the human perception of images. As a large proportion of CT studies involve the differentiation of low contrast structures, it is important to also cover subjective aspects of scanner performance when assessing image quality. This study used the Catphan 500 phantom, which includes low contrast details from 0.3% to 1.0% contrast relative to the surrounding medium, over a range of sizes from 2 mm to 15 mm diameter. The phantom was scanned on multi-slice CT scanners from four equipment manufacturers, using comparable acquisition and reconstruction parameters, to enable the comparison of results. The randomly presented images were assessed by a number of observers, who scored the visibility of the low contrast objects. The results of these assessments will be presented. In addition, the inter- and intra-operator variation of image quality scores was examined, and the influence of factors such as scanner mAs setting, criteria for visibility of objects and viewing conditions were investigated.

Challenges in the Evalutation of 8 and 16 Slice Scanners (view slides)

S Edyvean

This was presented as part of a special Medical Devices Agency session on the evaluation of new technology.