Impact of Arm Movement on CT Scan of Abdomen
Moving your arm during a CT scan of the abdomen can significantly degrade image quality and potentially conceal life-threatening injuries. 1
Effects of Arm Movement and Position on Abdominal CT Scans
- Arm movement during CT scanning creates motion artifacts that can severely compromise image quality and diagnostic accuracy 2
- Arms positioned alongside the torso (arms-down position) during abdominal CT significantly degrades image quality and creates artifacts that might conceal potentially life-threatening injuries 1
- In one documented case, liver hemorrhage was missed in the initial CT because of arm artifacts, only to be revealed by follow-up imaging 1
Optimal Arm Positioning for Abdominal CT
- For optimal image quality, patients should position their arms above the head during abdominal CT scanning 1, 3
- If raising both arms is not possible, raising at least one arm significantly improves image quality compared to having both arms down 1
- When arms must remain down, positioning them on a pillow on the pelvis rather than alongside the torso can reduce radiation dose by approximately 8.42% 3
Technical Considerations
- Modern multidetector CT scanners have faster tube rotation times and increased number of detectors, allowing faster table speeds and quicker scanning 2
- Faster scanning is important because patients are holding their breath and may experience discomfort as the colon is maximally inflated during abdominal CT 2
- The use of multidetector CT results in better colonic distention and fewer respiratory artifacts compared with single slice helical CT 2
Motion Artifacts and Image Quality
- Patients need to remain motionless in the CT scanner throughout the exam to avoid motion artifacts 2
- Motion artifacts can distort anatomical structures, decreasing their detectability and adversely affecting measurement accuracy 2
- With multidetector helical CT, scanning of the abdomen can be accomplished in a single breath hold, eliminating most respiratory and bulk motion artifacts 2
Special Considerations
- For patients who cannot hold their breath (such as those on mechanical ventilation), faster scan times (0.6 sec vs 1.0 sec) can significantly reduce motion artifacts and improve overall image quality 4
- Algorithm-based artifact reduction techniques are being developed to improve image quality in cases where arms-down positioning cannot be avoided 5
- Patients should void immediately prior to CT examination to reduce bladder activity and minimize artifacts 2
Practical Recommendations
- Follow the technologist's breathing instructions carefully during the scan to minimize respiratory motion 2
- Remain as still as possible throughout the entire examination 2
- If you have shoulder problems that prevent raising your arms above your head, inform the technologist before the scan so they can adjust your positioning for optimal image quality 3
- For patients undergoing PET/CT, staying seated or lying down and quiet following the administration of radiopharmaceuticals helps limit muscle uptake and improves scan quality 2