Prospective and Retrospective Data Collection Modes
©Walter Rasmussen, R.D.C.S.
Current ultrasound machines are capable of recording clips using two types of capture: Prospective and Retrospective Data Collection. Prospective Capture mode sets the machine to record whatever happens immediately after the image store button is pushed. Retrospective Capture mode sets the machine to record what happened immediately prior to pushing the store button. The ultrasound machine must be set-up to do either prospective or retrospective capture. For most ultrasound machines, the capture mode and number of beats captured can be changed at any time during the exam by visiting the Utility or Setup menu.
Sonographers vary in their preferences for either prospective or retrospective capture however; there are many advantages to using retrospective capture. For example, in prospective capture, it cannot be predicted exactly what will be recorded after the acquire button is pushed, while with retrospective capture, the sonographer knows exactly what will be recorded. With retrospective capture, events or features that are seen only on one or several beats during the course of the exam and which may not be possible to find again, are successfully recorded. Retrospective Capture can also save time because the sonographer knows exactly what has been captured and does not have to spend as much time reviewing the study.
A more extended version of retrospective capture is available regardless of which capture mode is set-up on the machine by pressing the Freeze button and then accessing the Cine video loop buffer. With this feature, it is possible to scroll back to a section which contains the sequence of interest, and then store it. This type of capture is more labor intensive than retrospective capture, but is quite effective to use when trying to record fleeting events/views or long clips.
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