Cardiac Dye Injector Synchronizer

In radiographic diagnosis of heart disease, it is necessary to synchronize accurately the injection of radio-opaque dye into the circulation with the diastolic portion of the cardiac cycle. Because of the high-energy electrostatic and electromagnetic fields associated with radiographic apparatus, it was decided to make a photosensitive transducer to be clamped on the ear lobe to give an electric signal proportional to the blood flow through the ear. This signal is electronically shaped and amplified, and used to trigger a variable delay timing circuit which then operates the injector.