Frame Grabber

A so-called frame-grabber is typically used to sample an analogue video signal and create a digital version of that image. This is often used for Ultrasound and some of the older digital modalities which do not have a DICOM interface. For Ultrasound, this is OK because of the relatively limited dynamic range. For CT images, technologists typically create two images for areas when a large dynamic range is needed, such as for the lungs to visualize soft tissue and bone separately. Using these frame grabbers vs. a true digital DICOM interface has several disadvantages, such as additional data entry steps, limited data range (typically only 8 bits), and potential image quality issues if the sample rate of the frame grabber is not configured correctly to match the initial image pixel characteristics. However, in some cases, there is no other option. When using secondary capture for frame-grabbing videos, such as from an Ultrasound, several vendors have implemented Optical Character Recognition (OCR) to automatically detect the patient’s name and other identification potentially eliminating the data entry step.