Department of Veterinary Clinical Sciences, Purdue University, West Lafayette, IN, USA
Radiographic investigation of joint diseases is very important in small animal practice. The radiographic changes may be very subtle such as slightly increased in synovial effusion to total bone destruction. Thus, good-quality radiographs are important and needed for every case.
The basis role of a veterinary technician is to produce good-quality radiographs for interpretation. In most universities, dedicated technician(s) of diagnostic imaging perform all of the procedures. They have extra training in the basic principles of diagnostic imaging as well as positioning of the animals. It is always very challenging for technicians in private practices to perform radiography, as they may not have enough training or experience. In more private practices, the veterinarians are not well trained in radiography, thus may not be able to determine what is a good-quality radiograph, thus may not be able to help the technicians.
In this lecture, we will discuss something very familiar to technicians - the important qualities of joint radiography. These qualities include the advantages and disadvantages of digital radiography, contrast, density, technique chart, table top versus using a grid, and also positioning.
Digital radiography has become more commonly available in private practices.1 The important advantages such as larger latitude of exposure and the ability to view in shorter time and easily repeat without extra cost. However, not all digital systems will produce good joint and musculoskeletal radiographs. Theoretically, the resolution of digital radiography is slightly inferior to conventional radiography. However, due to the vast technologies of digital radiography from different vendors currently available in the market, there is a large difference in the quality when comparing different digital systems. Some digital systems will be able to produce very good-quality images of the thorax and abdomen but less optimum for joint and musculoskeletal images. In principle, the resolution of conventional radiography is slightly superior to the digital system. However, a good knowledge of the principles of conventional radiography is needed to produce good-quality radiographs.
Contrast and density are important radiographic qualities. For digital systems, most veterinary technicians are able to perform minor alterations and adjustments of the contrast and density. The service technicians and engineers of the digital systems have the knowledge of tweaking the system to change the contrast and density. For joints, it is similar to any musculoskeletal radiography; a higher contrast image is preferred (lower kVp technique). It is more challenging and demanding for the veterinary technician who has a conventional radiography system. The contrast and density of the radiograph really depends on the technique chart used in the practice; thus the technicians should be able to prepare a good technique chart.2
In conventional radiography, most of the joints should be performed using a table top technique except for pelvis and shoulder. As for digital radiography, it depends on the digital system used. Some digital systems require the use of a grid for every image.
A minimum of two orthogonal views of each joint is needed for a full interpretation.3 Some lesions of the joint may only be visible on one view but not the other. Sometimes, multiple oblique views may be needed. Intra-articular non-displacing fractures are very difficult to visualize if the fracture line is not tangent to the X-ray beam. Proper positioning of the joint is very important. Any obliquity of the images may produce false lesions. Most patients with joint disease experience pain when the joint is manipulated. Thus, a deep sedation or general anesthesia is needed to aid in proper positioning of the joint. Every joint has a different important anatomy landmark; thus the veterinary technicians need to be able to recognize the specific anatomy landmarks.
1. Drost WT. Preface. Vet Radiol Ultrasound. 2008;49:s1.
2. Kirberger RM. Radiographic quality evaluation for exposure variables - a review. Vet Radiol Ultrasound. 1999;40:220–226.
3. Allan G, Nicoll R. Joints - general. In: Barr FJ, Kirgerger RM, eds. BSAVA Manual of Canine and Feline Musculoskeletal Imaging. 2006:71.