Fig. 6
From: Quantifying the reduction of respiratory motion by mechanical ventilation with MRI for radiotherapy
Example of the calculation of drift velocity during prolonged breath-hold (PBH). The diaphragm displacement during a PBH is measured at six time points, shown for volunteer 6. The drift velocity is determined by the slope of the linear fit (solid: PIBH, dashed: PEBH) through the measurements with diaphragm displacement in CC direction (mm) versus time (minutes). This example shows that drift velocity during PBH from inhalation (PIBH) is smaller than during PBH from exhalation (PEBH) for this volunteer