Quantification of gas exchange-related upward motion of the liver during prolonged breathholding-potential reduction of motion artifacts in abdominal MRI

Abstract

Objective: To test the hypothesis that there is a measureable upward motion of the diaphragm during prolonged breath-holds that could have a detrimental effect on image quality in liver MRI and to identify factor that potentially influence the magnitude of this motion.

Methods: 15 healthy volunteers underwent MRI examination using prolonged breath-holds in the maximum inspiratory position and a moderate inspiratory position. Coronal T₁ weighted three-dimensional gradient echo sequences of the entire thorax were acquired every 6 s during breath-holding allowing the calculation of total lung volume and the measurement of the absolute position of the dome of the liver. The potential impact of subject's gender, body mass index, and total lung capacity on the change in lung volume/diaphragmatic motion was assessed using random coefficient regression.

Results: All volunteers demonstrated a slow reduction of the total lung volume during prolonged breath-holding up to 123 ml. There was a measurable associated upward shift of the diaphragm, measuring up to 5.6 mm after 24 s. There was a positive correlation with female gender (p = 0.037) and total lung volume (p = 0.005) and a negative association with BMI (p = 0.012) for the maximum inspiratory position only.

Conclusion: There is a measureable reduction of lung volumes with consecutive upward shift of the diaphragm during prolonged breath-holding which likely contributes to motion artifacts in liver MRI.

Advances in knowledge: There is a measureable gas exchange-related reduction of lung volumes with consecutive upward shift of the diaphragm during prolonged breath-holding which likely contributes to motion artifacts in liver MRI. Correcting for this predictable upward shift has potential to improve image quality.The magnitude of this effect does not seem to be related to gender, BMI or total lung capacity if a moderate inspiratory position is used.

Figure 1.

Illustration of different positions of the diaphragm. A 29-year-old volunteer, coronal T₁ weighted gradient echo MR images demonstrating the differing positions of the diaphragm in maximum and moderate inspiratory positions (in this case about 1.6 cm).

Figure 2.

Observed subject-specific pulmonary volume time profiles (A) and liver shift time profiles (B) on moderate and maximum inspiratory breath-hold positions. The dotted lines represent the individual subjects and the solid lines represent the average across all subjects.