With almost superb annotated radiographs and more than line diagrams, the book combines the best features of a high quality atlas and those of a detailed reference book. The normal radiographic anatomy of immature and mature horses is presented with normal variations, incidental findings and details of significant abnormalities. Remarks on clinical prognosis and treatment are also included.
The emphasis throughout is on practical tips, common pitfalls, and the techniques used to obtain the best radiographs of specific areas and conditions. Changes for the third edition: Significantly enlarged to include a chapter on digital radiography Includes descriptions of several new radiographic projections Many of the images have been replaced by digital images A wealth of new illustrations have been added Presents expanded information on processing and image quality Updated to include new information, knowledge gained from continued clinical experience and the most relevant references from recent literature CD included with the book presents all the radiographic images in electronic format Since publication of the Second Edition, there have been major advances in other imaging techniques, including scintigraphy, ultrasonography, computed tomography and magnetic resonance imaging.
This third edition still focuses on radiography and radiology, but acknowledges the limitations of radiography in some circumstances. In these situations, reference is made to other imaging techniques which may be appropriate, along with suggestions for further reading.
Skriv anmeldelse. Old screens are like old horses, they collect scars and lose performance as they age, and some should be replaced on a regular basis  chapter 1 General Principles in order to obtain the optimum level of performance. It is also important that screens are cleaned regularly, to prevent the build-up of dust and extraneous materials within the cassette, which results in white spots and lines on processed films. The image produced on the x-ray film is dependent on the ability of the x-ray beam to penetrate a given volume of a specific tissue. It is more difficult to penetrate bone than air, and therefore less x-rays will reach the film if they have to penetrate bone rather than air.
The areas of film exposed to unobstructed x-rays will be black, whereas the areas protected by bone, which absorbs or deflects a proportion of the x-rays, will be relatively white and unexposed. Intermediate densities of tissues produce variable shades of grey.
Fat is the least dense tissue, and will give almost black tones, with soft tissues and bone giving increasingly light tones. It is the juxtaposition of these tissues of varying densities that allow for differentiation of form and structure. It is advantageous to record the exposure settings used each time, and gradually to build up an exposure chart. This should include a record of the size and age of the horse, the area radiographed, and the exposures and the film—screen combination used. This allows better radiographs to be obtained, and also provides a basis for estimating the required exposures for animals of different sizes and ages.
Once this chart has been created, it is important to maintain a constant FFD. A reduction in FFD increases the radiation reaching the screen by a factor of the square of the change in distance necessitating a reduction in the exposure factors , whereas an increase in distance has the opposite effect.
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Generally in equine radiography a FFD of 75— cm is used. Note that single emulsion film is particularly sensitive: a slight change in FFD can have a relatively big effect on exposure. In a well-positioned radiograph, the x-ray beam is perpendicular to the cassette to avoid image distortion.
Most of the radiation passes through the tissues and exposes the film, or is absorbed by the tissues.
Clinical Radiology of the Horse : Janet A. Butler :
A grid is placed in front of a cassette to absorb scatter radiation when the thickness of the area being radiographed is sufficient to produce enough scatter to interfere with interpretation of the radiograph. This is usually when the body exceeds 11 cm in thickness. Thus equine extremities below the carpus and tarsus usually do not require the use of a grid. Grids are generally not required for soft-tissue evaluation, and may be contraindicated in this situation.
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There are numerous types of grid, but their function is always to reduce the effect of scatter on the film. In equine radiology, parallel grids are normally used. The disadvantages of a grid are that they increase the exposure required and produce lines on the films, which are sometimes found objectionable when reading the radiograph.
If a focused grid is used, the x-ray beam must be perpendicular to the grid, centred on it, and at the correct FFD.
When grids are of value, this is noted in the discussion of the projections described in the following text. In several parts of the following text, reference is made to an aluminium  chapter 1 General Principles Figure 1. The upper leaves of the filter placed in the x-ray beam reduce the exposure of the upper part of the beam. This is placed immediately in front of the x-ray tube, and absorbs a proportion of the x-rays. It allows the intensity of the beam to be reduced in specific areas.
It is of particular value when radiographing parts of the horse that show a marked change in soft-tissue thickness from one side of the film to the other, e. Preparation of the patient is essential to good radiography. Quiet and careful handling will reduce movement, and sedation may be beneficial in some cases. Cotton wool ear plugs, or background music, may make the horse less aware of the noise of the x-ray machine. Areas to be radiographed should be brushed to remove mud from the coat, which can produce confusing artefacts.
For radiographs of the feet, the shoes normally need to be removed and the feet trimmed to remove loose horn and dirt. A high-quality radiograph is also dependent upon good darkroom technique. The developer and fixer must be kept clean, replenished, and replaced regularly. When hand processing, the solutions should be agitated before and during processing a film. It is important that developing should be carried out at a constant temperature and for set times.
The film should be rinsed thoroughly after developing, and washed well in running water after completing fixing, before being dried. Automatic processing undoubtedly gives more consistent results than manual processing, and allows marked improvement in radiographic standards. The reader is urged to consider the use of automatic processing as soon as the volume of work permits it. Radiation safety, i. There are codes of practice available in different countries, but the basic principles can be summarized as follows: 1 Keep the number of people present when radiographing a horse to the absolute minimum required for its safe handling.
Sedation may be required in some cases. This may be justified if it reduces the repetition of radiographs or prevents the horse panicking. No part of any attending person, even if covered with protective clothing, should be placed in the primary beam. Protective lead clothing protects from scattered radiation only, not the primary beam. Remember that the primary beam will continue past the patient and cassette, and personnel standing on the opposite side of the patient are at risk.
With the increasing use of radiography, and the rise in litigation against veterinarians, it is essential that radiographs are carefully labelled. This should be done photographically on the film, either by the use of one of the special tapes produced for this purpose, attached to the cassette when the film is exposed, or by a labelling light-box system in the darkroom. Labels should include at least the identity of the horse, the limb radiographed, the date, and lateral or medial markers where relevant. Ideally the veterinary practice and view employed should also be identified.
It is also essential that a complete examination is carried out, with an adequate number of films and views of the area involved. The exposures must be correct to demonstrate the lesions present, and the radiographs must be of diagnostic quality. An inadequate examination may be at best inconclusive and at worst totally misleading.
The emulsion swells when wet and detail cannot be appreciated on wet films. It is helpful if radiographs are always viewed using the same orientation, i. This aids interpretation, as only one image need be remembered for each area radiographed.
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This varies slightly from the convention that any film should be viewed as if the examiner was looking at the patient face on, e. The number of views required for any area varies, and is mentioned in the text.