The selection of technical parameters for the machine and reconstruction algorithms are extremely important and often overlooked.44 There are 3 key parameters that impact interpretation of HRCT scans: slice thickness, reconstruction kernels or algorithms, and the radiation dose, as shown here. Slice thickness influences the resolution of the image and interpretation of fine CT details. Reconstruction filters or kernels are created by the manufacturer of the CT machine and are proprietary but include a soft body algorithm and a high-frequency lung algorithm. Finally, the conventional radiation dose is 260 mAs, and we will look at the influence that radiation dose has on image quality and interpretation.
In addition to machine settings, consider the impact that the machine, the technologist, and the patient have on obtaining HRCT scans. In order to obtain clear images, it is imperative that the machine is set to obtain images correctly and perform reconstructions correctly. Further, the technologist must know which studies are required to obtain appropriate, clinically relevant images, and how to properly instruct the patient. Finally, the patient must comply with the instructions given by the technologist, particularly with regard to breathing.
Next, we will review the impact that slice thickness, reconstruction kernel, and radiation dose have on image quality and identification of HRCT abnormalities. It is important to note that each image series was acquired from a single patient, and the raw data were then subjected to a model to simulate images acquired under these different conditions.
