Avoiding radiography pitfalls to obtain the perfect image

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1 Vet Times The website for the veterinary profession Avoiding radiography pitfalls to obtain the perfect image Author : Charlotte Varga Categories : RVNs Date : July 1, 2012 Charlotte Varga RVN, takes readers through steps to producing high quality radiography a crucial aid to the patient s diagnosis Summary RADIOGRAPHY is an integral part of everyday veterinary practice, and quality images can provide the base for disease investigation using a non-invasive technique. Poor image production can influence the way films are interpreted and may, in some cases, lead to an incorrect diagnosis. Importantly, producing excellent images is essential to attain a correct diagnosis. This article will discuss the factors involved in producing the perfect radiographic image and how to avoid the pitfalls. WILHELM Roentgen, professor of experimental physics in Germany, discovered x-rays in 1895 while working on emissions from an electric current in a vacuum. Whenever a current was passed between the two electrodes in a charged cathode tube, a glow was noticed from a barium plantino-cyanide-coated screen, which was kept across the room (Bansall, 2006). Many developments have occurred over the years to enable this form of non-invasive diagnostic imaging to be readily available in practice and at low cost. The term radiography covers all procedures involved in producing and processing a radiograph (Aspinell, 2008). Producing high-quality radiographs is essential for achieving a correct diagnosis. 1 / 6

2 Image quality may be influenced by several factors, which include patient compliance, exposure, positioning technique, collimation, centring, the environment in which the radiographs are taken, and the experience of the radiographer. Radiographic faults are common in practice, and can result in repeated exposure and/or high-exposure factors, thereby compromising radiation safety. Under the Ionising Radiation Regulations 1999 (IRR99), all examinations must be clinically justified and all exposures must be kept to a minimum (Aspinell, 2008). Radiographic faults also have an economic impact, due to a prolonged and less efficient examination, as well as wasted films, chemicals and time (Agthe, 2008). Diagnostic imaging is continually advancing, with magnetic resonance imaging (MRI), computed tomography (CT) and ultrasonography all being available for our veterinary patients usually through a referral centre. However, radiography is readily available in general practice and can provide essential information to aid diagnosis. Conventional radiography versus digital techniques The art and science of radiology became an integral part of veterinary medicine and surgery shortly after the exposure of the first radiographic films (Burk and Ackerman, 1996). Two types of radiographic approaches exist the conventional approach in which a film is exposed to x-rays (electromagnetic radiation) and chemically processed to produce an image; and digital images produced in the following two ways. Computed radiography In computed radiography (CR), cassettes are used in a similar way to the traditional method. In the CR cassette, the image is recorded on to a phosphor plate that is read and digitised: the cassette is loaded into a computed reader, where the image is transferred from the phosphor plate in the form of a digital file and can be viewed on a computer (Watson, 2009). Direct digital radiography In direct digital radiography (DR) the cassette is directly connected to the computer to allow instant visualisation of the digital image. It is a quicker method than CR, as there is no cassette processing. Advantages of conventional radiography Avoids costs of installing and maintaining a digital system. Provides a greater image resolution, which may be lost with digital systems. Digital systems may use greater exposure factors up to 20 per cent higher in some cases 2 / 6

3 (Watson, 2009). Disadvantages of conventional radiography Cost of films, processing and chemicals. Storage space needed for films. Cleaning and maintenance of processor. Advantages of digital radiography No need for chemical processing. Space-saving for storing images. Quicker, as it takes less time to produce an image. Ability to zoom in and manipulate the image, such as the orientation, and to compensate for over or under exposure, brightness and contrast. An important advantage of digital radiography is that it has a much wider latitude, making it possible to achieve good images of soft tissue and skeletal structures using a single exposure setting (Crane et al, 2008). However, careful attention to the collimation should be undertaken. Disadvantages of digital radiography Expensive to install and maintain. Operator error. A good technique must be used and it is important not to rely on the digital system to correct faults, such as poor collimation and exposure ( Obtaining the perfect image Figure 1). To attain the perfect image it is important to prepare, position and process the radiograph correctly. The steps necessary to avoid common radiographic faults are discussed below. Prepare Definition of prepare make (something) ready for use or consideration (Oxford English Dictionary,2010). This includes the patient and equipment required for the procedure. 3 / 6

4 Ensure all equipment is ready for use: the x-ray machine, processing equipment and positioning aids, such as radiolucent troughs, sandbags, foam wedges, tapes and ties. Ensure the patient is ready for the procedure for example, if studies of the abdomen are being performed, has the patient been starved or given an enema (if necessary) for the procedure ( Figure 2 )? Set exposure factors ready for the first image. Always record the patient s details and exposure factors used in accordance with health and safety rules. TIP. Using previous successful exposure factors to make a quick reference chart for the practice is extremely useful, as it can make life in a busy veterinary practice easier and provides a base so all radiographers in the practice are following the same guidelines, especially when comparing previous radiographs with current ones. Restraint for radiography A clinical examination should be performed before any decisions are made regarding performing conscious, sedated or anaesthetised radiographic studies. Suitable chemical restraint should be used unless the patient is considered to be an anaesthetic risk. Manual restraint should only be used in extreme circumstances, as it poses a risk to the health and safety of personnel (Aspinell, 2008). If an animal does require manual restraint, IRR99 states this must be the decision of the veterinary surgeon, not nursing or auxillary staff. If it is not possible to sedate or anaesthetise a patient because it is contraindicated (for example, a respiratory-compromised patient), then with time, patience and a quiet working environment with good positioning aids it is possible to achieve good-quality conscious radiographs. Positioning Before positioning the patient, ensure all items, such as collars, leads and any other items that could cause artefacts on the radiograph are removed. Artefacts may lie over the point of interest and distract the focus of the reviewer. When positioning a conscious patient, make sure all positioning aids are easily available as you may only have seconds to capture the image be mindful of the patient. Calming techniques may be necessary within a quiet environment, which may well be forgotten in a busy veterinary practice. Always perform survey radiographs first before any obscure views, such as obliques. 4 / 6

5 Position the area of interest as close to the plate as possible to avoid magnification artefacts and blur. Use appropriate positioning aids for the view you require. Simply having a range of sandbag sizes and shapes to mould around the patient and hold it in place is advantageous. Foam blocks and wedges are especially useful when setting up for lateral radiographs to ensure no rotation. Ties and tapes can be used to extend limbs to ensure these do not obscure the area of interest. Think about the information required from the radiographs you are taking and remember the following key points. Thoracic radiographs. Always take the dorsoventral view first. If the patient has been lying in lateral recumbency for some time, the lungs will partially collapse. Thoracic views should always be exposed on inspiration well-aerated lungs will show better detail. Increasing the kilovolt (kv) and reducing the milliampere second (mas) produces a shorter exposure time and reduces motion blur (Martin, 2006; Figure 3). Spinal imaging. Support the vertebrae so they are all in the same horizontal plane to avoid distortion and magnification of individual vertebrae and of the intervertebral disc spaces (Aspinell, 2008; Figure 4 ). Abdominal views. Depending on the area of interest, starve the patient if necessary or perform an enema. A large amount of faeces can obscure the area of interest. Expose the image on expiration, as the diaphragm will relax into the characteristic dome shape and the lungs contract providing the maximum amount of space for the abdominal contents (Aspinell, 2008; Figure 5a ). Always extend the hindlimbs to prevent them being visible in the fields of interest ( Figures 5b, c ). Skeletal and joint imaging. For diagnosis of bone and joint disease, survey radiographs are usually required at right angles to each other. If joint disease is suspected, the patient must be positioned correctly, with no rotation, and the point of interest should be tightly collimated to provide a true representation of the joint. For example, when sending ventrodorsal (VD) extended hip position images to the BVA, the pelvis must be correctly positioned or the hips will not be scored and the radiographs returned ( Figure 6 ). Regarding centring, always centre over the main point of interest so the central beam is at right angles to the film to avoid geometric distortion. 5 / 6

6 Powered by TCPDF ( Collimation should always be performed so a four-sided, visible unexposed rim is evident on the film complying with health and safety rules to reduce scatter radiation. Scatter on a film can reduce contrast and lead to a poor-quality radiograph. Processing Label the film correctly, including the patient s name and the date. Film comparison is impossible if no date order can be established. Place a left or right marker where appropriate, so it is visible on the film, but not obtrusive to the area of interest. Unless a digital system is being used, films must be processed correctly to avoid underdevelopment (the unexposed rim of the film should be black with fingers behind the film not evident) and ensure correct fixing. To allow a comparison between radiographs taken at different stages of disease, it is important to have followed the same processing technique each time. In the darkroom, make sure the safe light is appropriate for the film type to avoid fogging (background film blackening). References Agthe P (2008). Common radiographic faults, Veterinary Times, 38(7): Aspinell V (2008). Clinical Procedures in Veterinary Nursing, Elsevier. Bansall G J (2006). Digital radiography, a comparison with modern conventional imaging, Postgrad Med J 82(969): Burk R and Ackerman N (1996). Small Animal Radiology and Ultrasonography: A Diagnostic Atlas and Text (2nd edn), W B Saunders, Pennsylvania, USA. Crane L et al (2008). In Hotston-Moore A and Rudd S (eds), BSAVA Manual of Canine and Feline Advanced Veterinary Nursing (2nd edn), BSAVA, Gloucester. Martin M and Corcoran B (2006). Cardiorespiratory Diseases of the Dog and Cat (2nd edn), Blackwell Publishing, Oxford. Watson T (2009). Technical revolution the pros and cons of digital radiography, VN Times 9(11). 6 / 6

Instructions. Print out all three tabs of the guide to be used as a reference.

Instructions. Print out all three tabs of the guide to be used as a reference. Instructions For the Learner 1) The purpose of the observation checklist is to help evaluate the skills obtained from the course. It is also a reference and reminder for what was learned in this course.