Design and testing of an MRI-compatible cycle ergometer for non-invasive cardiac assessments during exercise

We aimed to design a portable and relatively inexpensive MRI cycle ergometer capable of continuously measuring pedalling workload while patients exercise to maintain target heart rates.We constructed and tested an MRI-compatible cycle ergometer for a 1.5 T MRI scanner. Resting and sub-maximal exercise images (at 110 beats per minute) were successfully obtained in 8 healthy adults.The MRI-compatible cycle ergometer constructed by our research group enabled cardiac assessments at fixed heart rates, while continuously recording power output by directly measuring pedal force and crank rotation.Magnetic Resonance Imaging (MRI) and echocardiography are the most common non-invasive methods for assessing left ventricular function and structure. Previous studies have highlighted the advantages of MRI over echocardiography [1,2]. MRI scanning allows for three-dimensional estimation that is not affected by preload conditions, geometric assumptions, or the skill of the operator [3]. The use of MRI technology provides clear definitions of endocardial and epicardial borders, allowing an accurate and reproducible evaluation of left ventricular mass and volume throughout the cardiac cycle. For these reasons MRI scanning is considered the "gold standard" for cardiac function and structure evaluation.Magnetic resonance imaging has become an important tool for cardiac research, and resting cardiac assessments are now routinely performed. Dobutamine stress tests during MRI scanning are commonly used to evaluate the cardiac function at a target heart rate [4]. However, this is an invasive procedure with risk of severe side effects and therefore not always suitable for a research environment, especially if the research involves children and adolescents [4]. Research into MRI-based exercise cardiac evaluation is limited [5-9], even though it can unmask abnormalities that are not seen at rest. Commercially available ergometers use 'fixed workloads', where the pedalling resistance is mainta