M Mode Echocardiography
©Walter Rasmussen, R.D.C.S.
M Mode echocardiography, short for, “motion mode”, preceded two-dimensional imaging at a time when electronic technology was only capable of manufacturing a transducer with one ultrasonic crystal. The ultrasound probe projected a thin, stationary ultrasound beam with a fixed focal zone into the tissue and swept the reflections horizontally on an oscilloscope, producing tracings of motion that rapidly faded. The display was the only means for guiding the probe and the sonographer learned to move the probe and recognize cardiac structures through their patterns of motion. A strip chart recorder traced the images on rolls of photographic paper for a permanent record, which was folded-up and saved in a chart. Calibration marks allowed for accurate hand measurements.
On current ultrasound equipment, M-Mode is produced by positioning a cursor through the area of interest, thus isolating one scan line of a two-dimensional ultrasound image. A simulated strip chart recording is produced by computer software. The strip chart image can be frozen and measurements made directly on the screen. Standard views can be saved for later analysis and measurements taken can be incorporated in to a report template.
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