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Consider the range of clinical indications first when selecting an ultrasound system.
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The nature and location of your practice dictate the selection of stationary, mobile, or portable ultrasound systems.
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Ultrasound rooms should be appropriately designed with an ergonomic system to prevent strain injuries.
Ultrasound is a routine diagnostic tool in many countries, although many rheumatologists have not yet introduced it into their clinical practice. With a growing evidence base for applications of ultrasound in diagnosis and intervention, the initial skepticism about its clinical utility in rheumatology is no longer the principal obstacle to its use.
In a survey of British rheumatologists, the lack of training and the lack of equipment were identified as the two factors most likely to hinder the incorporation of ultrasound in their practice. Many formal training courses exist, but there is little published guidance on how to select ultrasound equipment. For many rheumatologists, the purchase of ultrasound equipment presents financial and technical challenges. In this chapter, we discuss the essential criteria for selecting ultrasound equipment.
Clinical Applications of Ultrasound
The clinical indications for the use of ultrasound in rheumatology and the technical complexity and imaging capability of ultrasound systems are increasing rapidly. The first question when purchasing an ultrasound system is this: What clinical indications will I use ultrasound for? The answer will determine the quality of machine and the specific capabilities that may be required. Most rheumatologists primarily require ultrasound imaging for the detection of articular and periarticular changes in inflammatory and degenerative arthritis and for the diagnosis of soft tissue pathology, such as tendinopathy, enthesitis, and tendon tears (particularly rotator cuff and Achilles pathology). Rheumatologists also use ultrasound for guidance of joint and soft tissue aspiration and injection and for monitoring therapeutic responses.
The range of peripheral joints—from the hip to the distal interphalangeal (DIP) joint—that will be imaged is an important consideration because joints of different sizes and locations have different technical imaging requirements. For example, ultrasound of the small joints of the hands and feet for synovitis in patients with inflammatory arthritis requires a higher specification system with a sensitive power Doppler tool than would be necessary for ultrasound of the hip in a patient with osteoarthritis. In some centers, there may be a specific interest in using ultrasound for assessment of nonmusculoskeletal tissues, such as arteries in temporal arteritis and vasculitis or salivary gland structure and function in Sjögren’s syndrome.
When choosing an ultrasound system, compile a list of all the proposed uses for ultrasound in the medical practice. A longer list of proposed uses demands higher technical specifications and a greater number of probes, which will increase the cost of the ultrasound system. It is important to be realistic about essential imaging requirements, and particularly for the beginner, the system should be principally chosen to suit everyday imaging needs (e.g., peripheral joint scanning) and not occasional needs, such as temporal artery scanning. If specific research is planned with the ultrasound system, purchase the most advanced ultrasound system the budget allows.
Mobility, Portability, and Siting of Ultrasound Equipment
The nature and location of the rheumatology practice is the next most important consideration in selecting ultrasound equipment ( Table 4-1 ) . Ultrasound systems can be broadly categorized as stationary, portable, or mobile ( Fig. 4-1 ).
| System | Image Quality and Technical Specification | Power or Color Doppler | Location | Cost Proportional to Image Quality |
|---|---|---|---|---|
| Stationary system | +++ | +++ | Single site best | High cost/high quality |
| Mobile system | ++/+++ | ++/+++ | Multiple locations at one site | Lower cost/medium to high quality |
| Portable system | +/++ ∗ | +/++ ∗ | Multiple locations at multiple sites | Medium cost/medium quality |
Stationary equipment usually refers to the larger, high-end, high-specification ultrasound systems traditionally found in a radiology department. They have a superior imaging capacity but usually are best sited in one location because of their size. They may generate significant heat and noise due to their cooling systems, and this needs to be taken into account in selecting a room to place them in. In too small a room, the noise from some systems can be intrusive when taking a history or discussing treatment with a patient. Poor ventilation combined with heat generation can make a small space uncomfortable for the patient and physician, and air conditioning may need to be factored into the budget. These machines are also very sensitive to sudden movements or knocks, as may happen when moved from room to room. The price range of these systems is $97,000 to $195,000.
Portable systems refer to compact systems approximately the size of a laptop computer. They usually have a single probe attached at one time. Hand-held pocket ultrasound systems have been developed, but they are inadequate for musculoskeletal work. Portables are suitable for use across sites and can be easily transported from clinic to bedside. They may be carried using a rucksack but also may be attached to a stand, although this may reduce the system’s portability. Portable systems are useful for large, medium, and small joints when assessing for fluid, synovial hypertrophy, bone, cartilage, and soft tissue pathology and for ultrasound-guided procedures. They do not have the same high-specification and imaging quality as the stationary systems, particularly for imaging small joint synovitis, although the imaging gap between portable and stationary systems is narrowing. Portables may be easily stolen. A premium is paid for portability because of the cost of miniaturization. The price range of these systems is $16,000 to $60,000.
Mobile systems refer to midrange machines that are smaller and more mobile than stationary systems but usually retain a higher specification and image quality than the portable systems at a lower price. The price range of these systems is $50,000 to $100,000.
If the rheumatology practice is based in a single hospital or clinic site and an ultrasound system will be sited in a single room, a stationary high-end or mobile midrange system is the most appropriate choice. Given that the size of ultrasound equipment with similar technical specifications is inversely proportional to the cost of equipment, there is no need to invest heavily in equipment portability if the system will be based in one room. If ultrasound is required for multiple locations at one site, a mobile or portable system will be more appropriate than a larger stationary system. Portable ultrasound systems are most appropriate for bedside examination and can be easily transported from clinic to the bedside or into the community.
Ideally, a department should have sufficient ultrasound systems to provide high-specification imaging, sensitive color and power Doppler, and a degree of mobility. One approach is to purchase two systems, such as a stationary system combined with a mobile or portable system. The stationary system provides extensive capabilities with several probes and a good power Doppler function that is suitable for small joint synovitis work and assessment of larger structures. The second system is a mobile or portable system that can be used at the bedside. These systems are particularly useful for very ill or immobile patients, for whom a trip down to the rheumatology department is not feasible. Portable systems are adequate for diagnosing most pathology but usually have inadequate power or color Doppler functions compared with larger systems. However, with advances in technology, the diagnostic quality is continually improving, and a portable system may be suitable for most scans, with only a small number of patients requiring a second scan on the larger system.
Financing Ultrasound Equipment
The amount of money available for purchasing a system determines the specifications to a large extent. Most manufacturers produce a high-end stationary model that is the most expensive system and a midrange system with concomitant reductions in cost and imaging capacity and quality. Depending on the assessed needs for imaging and where ultrasound will be performed, one midrange system and a portable system may be preferable to spending the entire budget on large, state-of-the-art, high-end equipment. Second-hand systems are also an option. Although they may become quickly outdated, many ultrasound companies provide upgrade software to enhance the capability of older systems ( Table 4-2 ).
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