CT Registry Certification Test Quiz!

Pitch is defined by how much the table moves during the time it takes to cover 360 degrees divided by the width of the beam.

Changing the filter in the filtered back-projection allows more or less high-frequency features. High frequencies (just like the periphery of k-space in MRI) are responsible for image sharpness - but also noise.

High-pitch techniques are useful for fast scans because they allow for rapid image acquisition. This is particularly beneficial in situations where quick imaging is required, such as in emergency cases or when scanning patients who are unable to hold their breath for an extended period. By reducing the scan time, high-pitch techniques help to minimize motion artifacts and improve image quality. Additionally, fast scans can enhance patient comfort and throughput in busy clinical settings.

Decreasing kV in CT is advantageous because it improves tissue contrast. Lowering the kV setting allows for better differentiation between different types of tissues in the body, making it easier to identify abnormalities or diseases. This is because lower kV settings result in a higher absorption of X-rays by the tissues, leading to greater contrast between them. By enhancing tissue contrast, healthcare professionals can obtain clearer and more accurate images, aiding in diagnosis and treatment planning.

The Dose-length product (DLP) is the best reflection of the total amount of radiation delivered to the patient. The DLP takes into account both the dose of radiation delivered during each scan (dose) and the length of the scan (length). By multiplying these two factors together, the DLP provides a comprehensive measure of the total radiation exposure the patient received during the entire scan. The other options listed, such as CT Dose Index (CTDI), Pitch, and Effective mAs, do not provide a complete measure of the total radiation delivered to the patient.

Performing a CT scan for stroke has several advantages, such as rapid execution, easy exclusion of hemorrhage, and assessment of parenchymal damage. However, it is not always possible to distinguish between old and new infarcts using a CT scan. This is because the appearance of infarcts on a CT scan may not provide enough information to determine their age accurately. Therefore, the inability to distinguish between old and new infarcts is not an advantage of performing a CT scan for stroke.

CT is actually most sensitive in the acute phase of a subarachnoid hemorrhage, typically within the first 24 hours. As time passes, the blood can become less dense and more difficult to detect on CT scans. Therefore, the statement that CT becomes more sensitive days to weeks after the acute phase of a subarachnoid hemorrhage is not true.

The filter in filtered back-projection compensates for blurring or smearing inherent to the process of back-projection.

Automated exposure compensation is used to adjust the exposure settings in order to achieve consistent image quality across patients of different sizes. Since larger patients may require more radiation dose to obtain a diagnostic image, automated exposure compensation ensures that the noise level in the image remains similar regardless of patient size. This helps in maintaining image quality and reducing the need for repeat scans.

In helical CT, the scanner never images a single slice. Instead, the slice is reconstructed by averaging CT projections taken 180 degrees apart - which are separated along the scan-axis based on the value of the pitch.