A physical assessment of the imaging performance of a panel-type X-ray image intensifier

The performance of a commercial panel-type X-ray image intensifier has been investigated by physical methods, both objective and subjective. The objective measurements show that the manufacturer's claims are justified, except perhaps in regard to contrast loss. The subjective measurements reveal that the conversion factor ("gain") of the device is such that dark-adaptation is not necessary, though best results are obtained in a nearly dark room. Hence the device confers a significant advantage, both in information and in dose to the patient, over traditional fluoroscopy. However, the conversion factor is nearly three orders of magnitude smaller than that of a conventional X-ray image-intensifier television system. Therefore, at modern fluoroscopic exposure rates, the eye is operating at light levels at which its own deficiencies set a limit to the perceptible information. To equal the performance of modern fluoroscopy the exposure rate to the intensifier must be increased to about 20 times the value customary in modern fluoroscopy. This can be done only by increasing the X-ray factors (kV and mA), resulting in a corresponding increase in dose to the patient of about one order of magnitude. Such an increase is in many circumstance unacceptable.