Radiography and Digital Imaging

• Radiography involves a specific workflow from requesting the X-ray to the patient receiving results, including checking the request, payment, image acquisition, and quality control.

Introduction to Digital Imaging

• Digital imaging offers significant advantages over traditional screen-film radiography, leading to its increasing adoption.
• Early digital images were interpreted from film placed on lighted viewboxes, but now digital images are read directly on display devices.
• Computed Tomography (CT) in 1974 and Magnetic Resonance (MR) imaging in 1980 were the first widespread digital medical images.

Image Processing

• Pre-processing takes place in the computer, where the algorithms determine the image histogram.
• Post-processing is done by the technologist through various user functions.
• Digital pre-processing methods are vendor-specific.
• Computed Radiography (CR) and Digital Radiography (DR) Systems are being used.
• A histogram is produced by computing the frequency of the pixel values.
• Pixel values represent attenuated x-ray exposure and areas of non-exposure.

Pixel and Voxel

• A pixel, or picture element, is the basic 2-dimensional component of a digital image.
• A voxel, or volume element, is a 3-dimensional element that includes depth, essentially the end of the voxel. (ex. CT & MRI Images)

Matrix and Bit

• A matrix consists of pixels in rows and columns, with a larger matrix improving spatial resolution.
• A bit is the amount of gray scale in the image, with modern images typically using 10 or 12 bits.

Quality Control and Image Management

• Quality control is done after patient exposure to check image acceptability.
• Quality control procedures vary by hospital and machine manufacturer.
• Quality control done now by computer makes Radiography Processes easier.

Contrast Enhancement

• Contrast enhancement is not possible in analog radiography, where technical factors determine the final appearance.
• Digital imaging allows contrast enhancement, making images readable even with less-than-ideal technical factors.
• Window width and window level are responsible for contrast enhancement.

Image Manipulation

• Window width is the gray scale of the digital image. The larger the width, the more grays demonstrated the lower the contrast of the image.
• Window level is the density or brightness of the image; a higher number results in a brighter image.

Background Removal of Shutter

• Unexposed borders around the collimation edges can cause veil glare by allowing excess light to enter the eye.
• Veil glare causes oversensitization of rhodopsin, leading to temporary white light blindness.
• Automatic shuttering is used in CR to blacken out white collimation borders, eliminating veil glare.
• Shuttering is a viewing technique only and should not replace good collimation practices.
• Removing white unexposed borders reduces the number of pixels and the amount of stored information.

Image Orientation

• Image readers scan and read the image from the leading edge of the imaging plate to the opposite end.
• The image is displayed exactly as it was read.
• Cassettes must be oriented correctly for proper image processing and display.
• In digital radiography, the part position should align with the marked top and sides of the imaging plate.

Image Annotation

• Annotation functions allow using preset terms or manual text input.
• Annotations can be useful when additional information is necessary.
• Annotations overlay the image as bitmap images.
• Annotations for side markers should not be used

Magnification

• Two common magnification techniques are magnifying glass and zoom.
• The magnifying glass function magnifies a small area within a box.
• Zoom allows magnification of the entire image, with navigation via mouse.

PACS

• PACS (Picture Archiving and Communication System) stores X-ray images for access on multiple devices.
• PACS facilitates easy access to patient files without needing to find physical films.
• PACS is also known as DIMS (Digital Image Management System).

Conclusion

• Digital radiography requires quality education and understanding of radiology principles.
• Digital radiography requires additional learning to maximize its usefulness.