Copyright 2009
CT scanning is performed with the patient in the supine position during full inspiration
Intravenous contrast material can be administered depending on the indication of the examination.
Collimation should be thinnest possible, typically 0.75 to 1.5 mm.
The reconstruction algorithm determines the frequency with which the acquired data are recorded when creating the image data. Soft tissue reconstruction is of low spatial frequency resulting in decreased perception of image noise, smoother soft tissues and improved contrast resolution at a cost of degraded spatial resolution. However, spatial resolution is optimized with a high spatial frequency algorithm (bone or sharp) with reconstructing the scan data. There is no smoothing function. The trade off is increased perceived image noise and decreased contrast resolution.
Image spacing commonly is 10mm because HRCT is considered a sampling technique
The smallest pixel size possible provides the best spatial resolution, therefore the smallest field of view required to include the lung parenchyma and as little of the chest wall. Usually, this means a maximum matrix size of 512 X 512.
Contrast Injection
IV contrast material usually given at a rate of 3-4 cc/s. Exams can be performed after a fixed delay of 20-25 s but this can be inaccurate in patients with severe cardiac dysfunction. Timing can be performed using a timing bolus or bolus-triggering methods.