Design, implementation and bench evaluation of a system for automatic synchronization of chest X-ray radiography with peak lung inflation

The clinical diagnostic data in a chest radiograph is enhanced if chest motion is minimal and X-ray beam exposure occurs at or near peak lung inflation (PLI). Currently, for patients who cannot voluntarily hold a maximal inspiration, beam exposure is manually “synchronized” with PLI and is a hit or miss proposition. We implemented a system for automatically synchronizing beam exposure with PLI during chest radiography. Pressure and bi-directional flow at the airway of patients undergoing positive pressure ventilation are monitored by a personal computer. An algorithm coded in C looks for a zero flow crossing and a peak lung pressure to determine PLI. Custom-built interface electronics allow (a) the system to detect, in real time, which buttons on the X-ray machine handswitch are being pressed by the operator and (b) X-ray beam exposure to be triggered via the software. During bench validation using a mechanical test lung, the system worked consistently, without false triggering. Tests with human patients are currently under way, with IRE approval and informed consent. Preliminary human data indicate that higher quality and more consistent chest radiographs are possible with automatic synchronization of X-ray beam exposure with PLI