Stanley H. Fox

Dose reduction on GE CT scanners.

There were about 40,000,000 CT procedures done in the US in 2001. CT procedures grew 16% between 2000 and 2001. About 5% of CT procedures are performed on patients under the age of 18 years. While the benefit to risk ratio for most individuals needing a CT study is not in question, there are concerns about the overall public health implications of the widespread and growing use of CT. The responsibility of CT manufacturers is to take practical steps to reduce the dose and therefore the risk. In this paper the steps being taken by GE Medical Systems to reduce CT dose are discussed. These measures include: SPR SEMINAR IN RADIATION DOSE REDUCTION 2002

Helical CT imaging performance of a new multislice scanner

The principles and operations of 4-slice helical CT are discussed. The SSP, image noise and artifacts of a 4-slice scanner are measured by phantom scans and compared with theoretical predictions and the measurements of single-slice CT. The evaluation of these physical attributes for all helical imaging modes of 4-slice scanner is summarized in an operation chart. The preliminary studies indicate that comparing with single-slice helical CT, the volume coverage speed of 4-slice helical CT can be at least twice as fast with fully comparable image quality, or, in many cases, 3 times as fast with diagnostically comparable image quality. Two examples are given to illustrate the clinical benefit of the speed performance improvement (and operation flexibility) provided by 4-slice helical CT.

Effect of helical pitch and collimation on tumor contrast and slice profile in helical CT imaging

In this paper, we present and validate a model that describes directly how the resulting object contrast in CT images is affected by (1) the x-ray collimation, (2) the table speed or helical pitch, (3) the size of the object, (4) the axial distance of the object to the reconstructed slice, (5) the distance of the object to the axis of rotation, and (6) the helical reconstruction algorithm employed. This model helps evaluate the trade-off between different helical scanning strategies and facilitates the selection of the optimal table speed and the x-ray collimation. With this model, the resulting tumor contrast can be predicted for given techniques. Besides the contrast, this model also provides the slice sensitivity profile. Several clinically important conclusions derived from this model are discussed.