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Jul 21 2008, 1:06 AM EDT AndyC

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Common image recording devices used in ultrasound


Multiformat (MF) Camera- From the 1970’s to early 1990’s this was the most common IRD used in ultrasound departments, they remain in more limited use today. An internal cathode ray tube (CRT) is employed to expose transparency film with a copy of the image on the monitor. Transparency film is a stable image recording medium with good gray-scale characteristics. The film is contained within a cassette and each film can hold between 1 and 9 images but 6 is the most common format. The multiformat camera is slow and labor-intensive to use in comparison to more modern IRD’s. There is a delay time between exposures and the cassette must be changed after every 6 exposures and then the films processed manually. Images stored in error can’t be erased and the spatial resolution is not as good as the more modern laser camera or dry processing systems.

Laser Camera- Through the 1990’s the Laser camera replaced the MF camera as the most common IRD used in ultrasound departments. Transparency film is again employed as the storage medium but instead of a CRT a very thin laser is used to exposure the film. The laser beam diameter is often in the order of 0.1mm indicating the excellent spatial resolution potential of these systems. A digital copy of the image frozen on the viewing monitor is stored in the computer memory of the camera until a full sheet of images is complete, the film is then exposed and processed either automatically or manually. These systems have many advantages over the MF camera. There is no delay time for image storage, film and cassette handling is significantly reduced, images are erasable and a variety of image formats can be used. Multiple imaging modalities (i.e. CT, MRI, NM, Fluoroscopy and Ultrasound can be interfaced to a single laser camera. In addition to excellent spatial resolution, there is also excellent contrast resolution and the area between images is exposed which improves visual perception of contrast in comparison to MF camera images. The biggest disadvantage of the laser camera is their expense in comparison to the MF camera but this can be offset by use with multiple systems.

Dry-Processing with Transparency Film- Their spatial resolution ability is comparable to that of a laser camera by virtue of the fact that a laser is generally used to ‘write’ the image on the film. In many cases exposure with the laser actually removes carbon from the film to varying degrees to achieve varying shades of grey, but this is not the only operating principle employed in these systems. The main advantage of these systems is that no darkroom is needed to process the film and the need to use traditional photographic chemicals and all the problems that go with them is removed. For this reason ongoing running costs with these systems is often less than a laser camera even though the initial outlay is similar. The film quality varies between manufactures particularly in the area of contrast resolution, with some systems struggling to achieve a true black background. Other systems produce films with an annoying odour or that are prone to rapid fading. It would certainly be advised that you ‘test-drive’ these systems before purchase to find the system that best suits the needs of your department.

Video



Paper Printer
Black and white thermal paper printer

PACS
Dicom storage


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