The practical disadvantages of decreasing the pitch in spiral CT scanning include:
- Increasing the radiation dose to the patient
- Decreasing the spatial resolution
Step-by-step explanation:
Pitch in spiral CT refers to the table travel per rotation divided by the beam width. A lower pitch means there is greater overlap between successive spiral rotations.
Decreasing the pitch will increase the radiation dose to the patient because there are more overlapping rotations exposing the patient.
It will also decrease the spatial resolution because having more overlapping data oversamples the imaging volume, leading to poorer resolution along the z-axis.
The other options are incorrect:
- Decreasing pitch does not decrease acquisition time, it increases it due to more overlapping rotations.
- It does not increase spatial resolution, it decreases it due to oversampling.
So in summary, the disadvantages of decreasing pitch are increased radiation dose to the patient and decreased spatial resolution. The key is understanding the effects of oversampling the imaging volume with a lower pitch factor.