Controlling Collimator Motion in Cobalt-60 Radiotherapy Machine by Converted Breathing Electrical Signal

Abstract

The respiration (Inhalation and Expiration) as physiological mechanism causes the internal human organs displaced partially away from the field size boundary area during radiotherapy; as the collimator of radiotherapy machine is fixed, hence the aim of the following study was to convert the breathing physiological motion into electric signal and further to set the collimator in real dynamic synchronized with breathing mechanism. With usage of pressure sensor; the mechanical motion of abdomen due to breathing has been converted into analog electrical signal in a real time sinusoidal mode, then with usage of a microcontroller; the analog signal has been converted to digital discrete sequence signals form with (0-5) volts {1100,0110,0011,1001}and {1001, 0011, 0110, 1100}, then these signals connected to the stepper motor in sequence form; via the driver circuit (ULN2003A) which link and gives enough voltage (0-12) volts to turn the stepper motor in clock wise direction (CW), in respect to signal {1100,0110,0011,1001} or counter clock wise (CCW), in respect to signal {1001, 0011, 0110, 1100} which is corresponding to collimator motion of radiotherapy machine (Co-60) in synchronized pattern to abdominal motion induced by breathing mechanism.