Digital Radiography and PACS Flashcards

In digital radiography, 'exposure creep' refers to:

Answer: A gradual increase in patient exposure over time because digital processing masks overexposure by adjusting image brightness automatically

Exposure creep occurs when radiographers gradually increase mAs over time because the digital processing corrects for overexposure, masking the fact that patients are receiving excessive dose.

Which type of artifact in CR imaging appears as a faint previous image superimposed on the current image?

Answer: Ghost artifact (residual image artifact)

Ghost artifacts occur in CR when the PSP plate was not completely erased after the previous exposure — residual electrons release during the next scan, creating a faint superimposed image from the previous study.

The image matrix size in digital radiography refers to:

Answer: The number of pixels arranged in rows and columns that make up the digital image

The image matrix defines how many pixels are arranged in rows × columns to form the digital image — a larger matrix (more pixels) means higher spatial resolution.

In a PACS environment, the RIS (Radiology Information System) primarily manages:

Answer: Patient scheduling, order management, and radiology report generation

The RIS manages the administrative and workflow functions of the radiology department: scheduling, patient demographics, orders, billing, and report management — it interfaces with PACS for complete workflow.

What is the primary difference between lossy and lossless image compression in medical imaging?

Answer: Lossy compression permanently discards some image data (irreversible), while lossless compression preserves all original data (reversible)

Lossy compression (e.g., JPEG) permanently discards image data to achieve smaller file sizes, while lossless compression (e.g., JPEG 2000 lossless, RLE) preserves all original data perfectly.

When evaluating monitor quality for diagnostic radiology, the minimum luminance ratio (maximum to minimum luminance) and the maximum luminance for primary diagnostic displays should be:

Answer: Luminance ratio ≥ 250:1 and maximum luminance ≥ 350 cd/m²

AAPM TG-18 recommends primary diagnostic displays have a maximum luminance ≥ 350 cd/m² and a luminance ratio (Lmax/Lmin) ≥ 250:1 to adequately display the full diagnostic gray scale.