A pneumatic phantom for mimicking respiration-induced artifacts in spinal MRI

To design a phantom capable of mimicking human respiration to serve as a testing platform for correction of the static and time-evolving magnetic field distortions typically encountered in MRI of the spinal cord.

An inflation system to mimic the air variation of the human lungs was constructed. The inflation system was linked to a phantom containing synthetic lungs and an ex vivo human spine. The relationship between air pressure and phantom lung volume was evaluated via imaging experiment. The geometric distortion (pseudo-displacement) caused by the B0 inhomogeneities was measured on echo planar imaging slices for different air volumes.

Linear and quadratic relations linking air pressure to phantom lung volume were observed with a Pearson correlation coefficient of 0.99. Air distribution was uneven across the synthetic lungs, exhibiting a left-to-right lung volume ratio of up to 5/4. The pseudo-displacement artifact of the spine caused by the air-filled lungs was observed.

The proposed phantom can reproduce the lung volume variation of human respiration and thus can serve as a reliable testing platform for the correction of the associated time-varying B₀ field distortions. Details of the construction and code for the inflation system microcontroller are available for download as open source. Magn Reson Med 79:600-605, 2017. © 2017 International Society for Magnetic Resonance in Medicine.