Diagnostic imaging techniques

image of Diagnostic imaging techniques
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This chapter is designed to give information on veterinary radiography, including health and safety; principles; routine procedures; patient positioning; contrast techniques; film processing; care of radiographic equipment; and assessing radiographic quality. This includes sections on the X-ray room; the X-ray machine; positioning of exotic pets; and care of radiographic equipment.

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11.2 Film badge with the film removed and protected within its own envelope.
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11.3 Lead tunics can come in a range of colours. Keeping this equipment flat at all times is imperative in order to avoid damage or cracks within the lead.
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11.4 Various universally recognized X-ray radiation warning signs.
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11.6 The electromagnetic spectrum.
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11.7 Components of a tube head.
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11.8 The exposure button lead, in this case coming from the control panel on the left, allows the veterinary nurse to be positioned a safe distance away from the primary beam. A lead screen is giving additional protection. (Courtesy of E Mullineaux)
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11.9 X-ray paths. Absorption: photoelectric effect. Compton effect, or Compton scatter. Radiation through the patient to the cassette.
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11.10 The five radiographic opacities.
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11.11 Increasing the film focal distance (FFD) decreases the amount of penumbra, increasing radiographic detail and divergence of the primary beam. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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11.12 Increasing the object-to-film distance (OFD) increases the amount of penumbra, decreasing radiographic detail and thus increasing the magnification of the image. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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11.13 Newton’s inverse square law states that the intensity of an effect is reduced in inverse proportion to the square of the distance from the source. Thus, doubling the distance from the source will reduce intensity by ¼.
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11.14 Film structure.
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11.15 Measurement of patient thickness using callipers.
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11.16 Different grid designs.
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11.17 Positioning for BVA hip dysplasia scoring. A variety of restraint aids can be used to help prevent rotation of the patient and keep the femurs extended and parallel. In this case a trough, ties and sandbags stop rotation of the thorax, whilst a foam wedge and parcel tape help position the hindlimbs. (Courtesy of E Mullineaux)
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11.19 A selection of positioning aids (from top left, clockwise): foam wedges in several shapes and sizes; various forms of semi-adhesive tape; rope ties (calving and lambing ropes are soft and suitable for this purpose); sandbags in assorted weights. A sedated cat gently restrained using two lightweight sandbags. (Courtesy of E Mullineaux)
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11.20 A chemically restrained patient along with a variety of positioning aids.
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11.21 Collimation techniques: the unsuitable and the good.
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11.23 Positioning chart for the pelvis and hindlimb. (Drawings reproduced from , with the permission of the publisher)
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11.24 Positioning chart for the forelimb. (Drawings reproduced from , with the permission of the publisher)
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11.25 Positioning chart for the skull. (Drawings reproduced from , with the permission of the publisher)
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11.26 Positioning chart for the spine. (Drawings reproduced from , with the permission of the publisher)
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11.27 Positioning chart for soft tissue. (Drawings reproduced from , with the permission of the publisher)
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11.29 Using a channel hanger. The film should sit within the channels. At the top of the channel hanger there is a strip of metal that folds down to help secure the film in place.
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11.30 Using a clip hanger. Two clips located at the top and two at the bottom help to hold the film in a secure manner.
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11.32 Manual processing procedure. Exact timings will vary – follow the manufacturer’s recommendation.
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11.33 Automatic processor tanks and rollers, with lid removed. (Courtesy of R Dennis)
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11.35 Lateral view of the thorax and abdomen of a cat. The positioning is adequate, although the forelimbs could have been extended more cranially and the thorax is slightly rotated (a foam wedge would have decreased this rotation). It is unclear whether the desired view was of the lateral thorax or the lateral abdomen, since the radiograph is centred on the diaphragm. The thoracic inlet and thoracic vertebrae are missing from the image. The film is too pale overall, indicating underexposure. The anatomical structures are not clearly visible, especially caudal to the diaphragm. Collimation is not evident (0%) as the primary beam is off the film edges. There is no L/R marker or label. Brown coloration at the edges of the film suggests insufficient rinsing or fixer splashes. There is damage in the corners from clip hangers and water marks are evident.
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11.36 Lateral view of the femur of a cat. Positioning is poor, as the abdomen is overlying the proximal end of the femur and obscuring the bone. Exposure is good enough to enable a diagnosis to be made. Centring is poor—it should be on the mid-shaft of the femur. The radiograph is labelled but there is no L/R marker. Collimation is not evident, as the primary beam went beyond the edges of the film. The white areas on the left and at the top are due to light leakage, as a result of the cassette not being properly closed or incorrect storage of film prior to exposure. A brown tinge indicates poor or inadequate rinsing during processing.
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11.37 A damaged screen will affect the screen/film contact.
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11.38 Cleaning the cassette. The cassette should be kept on a flat surface at all times, even for drying.
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