Respiratory monitor system for 4D CT image acquisition based on accelerometer. Design and implementation

Abstract

The use of 4D CT images in Radiotherapy planning is increasing. Some commercial systems use abdominal movement to correlate images with respiratory phase. An in-house developed system based on an accelerometer to register patient’s abdominal movement and a software to group 4D images in their corresponding respiratory phase is presented. A phantom test evaluates the capacity of the system to properly identify respiratory phases. A volunteers study compares breathing curves acquired by the accelerometer with those obtained using a commercial system. In the phantom images, maximum  difference between real and calculated phase is 0.2 s. In the volunteer study, position of the curve maxima found by both systems differs, on average, around 2% (SD = 2%) of the respiratory cycle period when volunteer’s breathing is regular. Only when breathe is very irregular, differences of up to 10% in the phase assignment are found.