1. Thursday Case of the Day
Physics
Author: Karen Brown, MHP
Penn State College of Medicine, Hershey PA
History: A 72 yo patient with myeloma in remission has a bone survey to rule out new lytick lesions. Lumbar spine images are compared to a previous study acquired on the same x-ray unit. What is the possible cause of image quality degradation in the current study as compared to the previous study?
A. Use of higher kV setting
B. Reduced source-to-image distance
C. Decreased field of view
D. Insufficient mAs
Previous study
Current study

2. Findings:
Reduced source-to-image distance would result in increased magnification in the current study as compared to the previous study. The current study does not appear to be magnified compared to the previous study.
The field of view in the current study is slightly decreased compared to the previous study however use of tighter collimation (smaller field of view) would reduce the amount of scatter radiation produced resulting in improved image quality.
Insufficient mAs would result in more quantum mottle (noise) which is not observed in the current study.

3. Diagnosis: A. Use of higher kV setting

4. Discussion:
The previous study was acquired using 85 kV and 200 mAs. The current study was acquired using 95 kV and 310 mAs. The lower kV used in the previous study produced an image with greater contrast as compared to the current study.
Previous study
Current study