CPAS CPAS Network & Connectivity 2 — Questions and Answers
Question 1: What compression ratio does JPEG 2000 lossy compression typically achieve for CT or MR images while maintaining diagnostic quality?
- 2:1
- 5:1 to 8:1
- 10:1 to 20:1 (Correct answer)
- 50:1 to 100:1
Correct answer: 10:1 to 20:1
JPEG 2000 lossy typically achieves 10:1 to 20:1 compression for CT/MR studies while retaining sufficient diagnostic quality for most clinical reads.
Question 2: In PACS performance measurement, what does 'latency' specifically refer to?
- The maximum rated data transfer speed of a connection
- The delay between requesting an image and its appearance on the diagnostic workstation (Correct answer)
- The total storage capacity of the PACS archive
- The number of simultaneous users supported
Correct answer: The delay between requesting an image and its appearance on the diagnostic workstation
Latency is the elapsed time from when a workstation requests an image to when it is fully rendered on screen, directly impacting radiologist reading efficiency.
Question 3: Which DICOM transfer syntax guarantees that no pixel data is altered during compression?
- JPEG Baseline (Process 1)
- JPEG 2000 Lossy
- JPEG-LS Lossless (Correct answer)
- MPEG-4
Correct answer: JPEG-LS Lossless
JPEG-LS Lossless preserves every original pixel value exactly, making it suitable for applications where any data alteration is clinically unacceptable.
Question 4: What is the primary clinical benefit of image prefetching in a PACS workflow?
- Reduces long-term archive storage costs
- Loads prior studies before the radiologist requests them, eliminating wait time during reading (Correct answer)
- Automatically deletes outdated or duplicate studies
- Compresses images for long-term archival
Correct answer: Loads prior studies before the radiologist requests them, eliminating wait time during reading
Prefetching anticipates which prior studies a radiologist will need based on the worklist and pre-loads them into cache, so images appear instantly when opened.
Question 5: What is the primary role of a PACS cache server in a multi-site hospital network?
- Encrypts all images before transmission to remote sites
- Stores frequently accessed recent images locally to reduce retrieval time from the central archive (Correct answer)
- Manages DICOM routing rules across all modalities centrally
- Generates compliance audit logs for regulatory reporting
Correct answer: Stores frequently accessed recent images locally to reduce retrieval time from the central archive
A PACS cache server at each site holds recently accessed studies locally, so radiologists retrieve images quickly without pulling every study from the central archive over the WAN.
Question 6: Which network performance metric best measures a PACS network's ability to sustain continuous image delivery for multiple simultaneous users?
- Latency
- Jitter
- Throughput (effective bandwidth) (Correct answer)
- Packet TTL (Time to Live)
Correct answer: Throughput (effective bandwidth)
Throughput measures actual sustained data delivery capacity, determining how many radiologists can simultaneously stream large image sets without performance degradation.
CPAS CPAS Network & Connectivity 2
What compression ratio does JPEG 2000 lossy compression typically achieve for CT or MR images while maintaining diagnostic quality?