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12 Ultrasound Equipment andPurchase
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is not currently widespread. Probes on compact cart-based machines typically attach to the ultrasound machine through a set of ports (Fig.12.26) that allow switching of probes without physically changing the port. Laptop-sized machines usually require the probe to be physically interchanged (Fig.12.27). Pocket-carried machines often have a xed probe that cannot be changed, although recent models have combined more than one probe type in a single transducer (Fig.12.28). Innovative wireless probes have been developed by some companies, with control functions on the probe itself to allow one-handed operation (Fig.12.29) or use of Bluetooth and wi to transmit images to smartphones or tablets (Fig.12.30). All transducers have raised color-marked lines or dots called “indicators” which correspond to a marker on the screen for assisting operators’ spatial orientation. Probes generally cost between $7000 and $12,000 USD each, with warranties lasting 1–5years [5]. Vendors manu­facture their probes differently, inuencing their durability and degradation time. It is worth asking companies about their manner of probe construction.
Fig. 12.23 Phased array transducer
Fig. 12.24 Endocavity transducer
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cardiac imaging
• Exclusively for
• Best for
• Best for vascular,
• Potential POC US
transvaginal
imaging
• May be used for
MSK, ocular
applications
• Essential for the
applications
in cardiac resuscitation
intra-oral
peritonsillar abscess
evaluation
most common
procedures
(peripheral IV,
suprasternal notch
• May be used for
transabdominal OB,
central access)
• May be used for
aortic arch
assessment
bowel evaluations in
thin patients
• Variations exist that
R. Liu et al.
role in current
Probes are expensive
beyond normal current
• POC US training
• Requires training
consideration of
relatively specialist
• Needs specic
• Applications are
offer very high-
frequency imaging
typically does not
offer better
ergonomic form
factors like the
“hockey stick” probe
• New technologies
extend past 4cm
resuscitation care
• Unclear denitive
operator use/
prociency in the
clinical
environment
OB imaging
Phased array Curvilinear Linear Endocavitary TEE
Pros • Best for cardiac scanning Best for abdominal and
Table 12.2 Summary of the advantages of disadvantages of different probe types
May be used for
thoracic and MSK
imaging, particularly
of deeper structures
footprint
• Lower frequency with small
imaging for echo
• Contains ideal tissue harmonic
abdominal imaging too
• May be used for thoracic &
• May be used for transcranial
especially for eFAST
exams, rone to being
dropped or
• Due to heavy use,
• Larger footprint • Depth of eld
and image quality may degrade
non-cardiac presets
applications
obese patients
• Depending on vendor, crystals
• Image quality may be limited in
Limits • Image quality may be limited in
mistreated
relatively quickly
• Not good for supercial imaging
12 Ultrasound Equipment andPurchase
Fig. 12.25 TEE probe
Fig. 12.26 Probe ports
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Fig. 12.27 Probe connection into laptop
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Fig. 12.28 Plug in probe— pocket size
Fig. 12.29 Freestyle hand image
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Fig. 12.30 Smart phone controlled portable ultrasound
12 Ultrasound Equipment andPurchase
165
Linear transducers (also known as straight linear array probes) have a at, oblong rectangular surface (Fig.12.22). They are sometimes referred to as “vascular” probes as they are often used for this indication, although they have more diverse applications. The crystals are aligned parallel to each other in a straight line, and therefore produce sound waves that travel in straight lines. The eld of the image on screen is rectangular, like a box. This probe has a high-frequency range (5–13MHz) and so provides good resolution of images but less penetration into body cavities. Therefore, it is ideal for imaging supercial structures involved in soft tissue, musculoskeletal, vascular, pleu­ral, and ocular imaging. Of note, it is commonly used for procedural guidance.
Variations of the linear probe exist, like the “hockey stick” probe (Fig.12.31) that allows the probe to be gripped like a pencil. This can afford a more stable grip when performing procedures or applications that need ne motor action. In addi­tion, since 2016 vendors have developed ultrasound high-frequency probes with capabilities up to 70MHz (e.g., Sonosite Vevo MD transducers) that offer advance­ments in neonatal, vascular, and MSK examinations. The advantage of this in the point-of-care community has yet to be seen.
Curvilinear probes (Fig.12.21) (also called convex) have crystals arranged along a large curved surface and produce sound waves traveling in a fan-shaped arcing beam. This allows a eld of view that is wider than the probe’s footprint, so images appear narrower on top of the screen and wider at the bottom. This conguration is often referred to as a “sector” probe, which also refers to phased array and endo­cavitary probes, as distinct from linear. The frequency of a curvilinear abdominal probe typically ranges between 2 and 6MHz, allowing sound waves to penetrate
Fig. 12.31 Hockey stick probe
166
R. Liu et al.
deeper into the body but providing less resolution. Curvilinear probes are com­monly used to ultrasound the abdominal cavity, perform transabdominal fetal evalu­ation, evaluate the pelvis and bladder transabdominally, assess the pleural cavity, and perform certain musculoskeletal procedures (e.g. intra-articular shoulder injec­tion and reduction, lumbar puncture). Highly curved small curvilinear probes with mid-level frequencies (4–8MHz) are available for pediatric scanning (Fig.12.32 small short radius mid-frequency range curvilinear probe).
Phased array probes have a at, square surface shape and its crystals are grouped closely together in a point (Fig.12.23). Sound waves originate from this single point and spread outward, creating a triangular or sector image. The probe frequency is between 2 and 8MHz. As the footprint is smaller and atter than the curvilinear probe, it is easier to maneuver between rib spaces and use in smaller areas. It is ideal for cardiac imaging as well as abdominal evaluation of thinner, smaller patients. Users should be aware that when selecting the phased array probe the machine may default to a cardiology conven­tion, which may reverse the indicator-to-screen orientation from other indications.
The endocavitary probe (Fig.12.24) has a small circular curved face that is nar­rower than the curvilinear probe and produces higher frequencies (8–13MHz). Because of its small size, it is ideal for placement into smaller cavities (intra-oral or intra-vaginal) for evaluation of peritonsillar abscess and most commonly, for OBGYN applications [4]. It can also be used for central line placement and assess­ment of the aortic arch at the sternal notch.
A transesophageal probe (Fig.12.25) has the ultrasound face at the end of a exible apparatus designed to be inserted and manipulated to visualize the heart adjacent to the esophagus. These probes are uncommonly used in the emergency department setting, but have been adopted by intensivists particularly in Europe. The transesophageal probe is more expensive than other probes (typically about $20–30K), but provides unparalleled visualization of the heart.
In addition to TEE probes, there are many other probes that may be useful in POC imaging, such as biplanar probes and 3D probes (Fig.12.33—biplanar probe, and Fig.12.34 xplane 3D probe).
Fig. 12.32 Middle frequency curvilinear probe
12 Ultrasound Equipment andPurchase
Fig. 12.33 Biplane probe
167
Fig. 12.34 Xplane 3D probe
168
In an ideal situation, a clinical ultrasonographer will have access to all available types of probes. However, due to budgetary constraints it may be necessary to prioritize which probes are obtained. Transabdominal imaging can often be reasonably per­formed with a phased array probe. However, cardiac imaging is difcult with a large footprint curvilinear probe. Thus when programs are trying to economize, they may choose a phased array or microconvex probe instead of both a phased array and large footprint curvilinear. This will work, although the quality of abdominal imaging will be improved if a high quality curvilinear probe is available. A linear probe is required for vascular, ocular, and musculoskeletal imaging, and an endocavitary probe is required for transvaginal imaging. Most point-of-care ultrasound machines will require at least phased array and linear probes, with probe selection tailored to the uses intended.
R. Liu et al.

Equipment Purchase Considerations

The uniqueness of clinical ultrasonography is that it brings imaging to the patient bed­side and so the practice environment is frequently changing. An operator can work in a hospital, detach a machine, and bring it to an international site. Or, the provider may choose to work primarily with smaller machines for personal use at multiple sites. Whether in a hospital, the back of an ambulance, helicopter, cruise ship, campsite, on top of a mountain, or in space, all environments of practice can be harsh. Machines need adaptability to keep pace with growing demands while withstanding the elements.
Portability andDurability
Sizing of machines have been addressed above, and it would benet the buyer to physically measure the dimensions of patient care space and docking areas to ensure a machine ts.
While all buyers wish their units to be easily maneuverable and indestructible these characteristics will vary by manufacturer and model. Cart systems and hand­carried machines mounted on carts should be lightweight and easily turned. Wheels and wheel casings need to consist of durable material and perform multidirectional functions to enable movement. The composition of machine housing and articulating joints (e.g., height adjustment levers, monitor arms) need to be rugged, as machines run into walls during transport and are splashed by corrosive substances. Laptop-sized and smaller machines should have casing and screens that withstand being dropped.
Similarly, crystals within transducer footprints and seams in the probe casing need to be resilient if dropped accidentally. Cable management solutions that prevent cord entanglement and trampling are essential for transducer protection. If probe cables are run over by the machine, cables should withstand wear and tear to protect the wires inside. Wireless transducers are a way to combat this issue, but lead to concerns of probe misplacement or theft. Retractable cords have been proposed, but sterility, cleaning, and functionality have been problematic and to our knowledge there are no commercially available retractable probe connectors. Some companies have employed power stations to prevent power cord trampling, alleviate ergonomic issues
12 Ultrasound Equipment andPurchase
associated with machine charging, and avoid handling of dirty cords that have dragged on the oor. Machines should contain storage options for transducers, gel, cleaning solution, and accessories to provide further protection. All surfaces associated with a machine have to be easily accessible and cleaned with readily available solutions.
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Ease ofUse
In critical care situations, quick machine boot-up time is a must and this can be facilitated by a power sleep mode. Comparing “cold boot” and “awakening from sleep” times should be done prior to purchase. Battery life is also an important fea­ture, as situations arise where usage for 2–3h or more is needed away from a wall socket. Quick battery charge time or ability for battery replacement during transport is ideal. Critical features (e.g., power, gain, depth, measure, freeze, save image, change transducer) must be easy to nd and intuitively located. Keyboard and knobs should be backlit to accommodate imaging in darkened rooms. The machine’s fea­tures and controls need appeal to users of differing skill levels, easily upgraded when new software and advanced packages are desired. Machines using touch­screen keypads need to be responsive, without lag or oversensitivity.
Integration of particular equipment into current or future department workow should be considered. Some manufacturers and models will integrate better with par­ticular electronic health records and image management systems (including both “mid­dleware” or a more traditional picture archival and communication service—PACS). It may be very helpful to discuss machine integration with someone who uses a similar workow, and vendors are often able to provide prospective customers with these refer­ences. Patient demographics should be available for selection from a work list and convenient to enter manually if needed. Some companies have enabled automatic trans­fer of patient information to their machines using a patient identity band barcode reader. The ability to select a patient without manual entry facilitates correct documentation for electronic medical record transfer and quality assurance [3]. Likewise, “ending an exam” facilitates image storage and the ability to create a new patient. Most systems will do this automatically, but a cumbersome process will hinder workow. The pro­spective buyer should think carefully about how images will be stored and transferred from the machine and if possible discuss with someone using a similar conguration. Some ultrasound companies are now interfacing with middleware documentation com­panies to allow the completion of interpretation worksheets on their machines. This enhances operator compliance with documentation and speeds workow.
Image Storage andTransfer
Denitive image archival is required for ultrasound reimbursement, and effective image management can enhance quality assurance and communication with other practitio­ners. While thermal printing, VHS cassette, and even DVD recording of images are still performed in some places, current equipment is designed for digital transfer of still and moving images or “cineloops,” which are preferred by many users. Export of images in
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general formats such as jpeg or mp4 is typically available from the machine if desired, but most modern units will utilize the DICOM image storage format (a standard format that stands for Digital Imaging and Communication in Medicine). If manual export is anticipated, efcient export will prevent long download times and le corruption. Contemporary le storage options (USB drives, SD cards, wireless or cloud transfer) should be available. Wireless transfer of images is much more suited to the point-of-care environment if it can be congured. While most machines can have an external wi- adapter added, ideally this should be housed internally to ensure durability and function­ality. Machines using plug-in ethernet connectors need to secure them to protect against accidental dislodgement when attaching or removing ethernet cables. Ethernet standards offered on the machines need to follow hospital security protocols, and it is benecial to involve hospital IT during purchase discussions to ensure a machine is compatible with the hospital intranet system. Like computers, internal components and storage should be upgradeable and replaceable if needed (See Chap. 17 – Workow and Middleware).
R. Liu et al.

Service

Warranties or service contracts should be carefully reviewed prior to purchase, as they are essential for the maintenance of machines and probes. While some manu­facturers include a full 5-year warranty as part of the initial purchase price, most vendors will offer a 1-year warranty with a service plan to be purchased after the initial warranty period. Service plans should typically be budgeted at about 10% of the machine cost per year, and spending more money for higher service packages is often a wise decision [5]. They should include replacement of broken parts and loan of either parts or full machine support during repair, ideally with pickup and ship­ping included. The warranty coverage of probes should be explicitly addressed, as these are often the most vulnerable parts of the machine. Warranties may not cover a probe repair or replacement if there is evidence of “excessive wear and tear” (something that unfortunately may be difcult to avoid in the point-of-care setting), while other companies will do this once but not subsequently.
Company replies to service calls need to be prompt, since delay of service could impact patient care. As many clinical ultrasonography practitioners are in emer­gency settings that are open 24/7, repair services need to be available past typical business hours. It is worth questioning representatives on service technicians’ response times, methods of communication, location, and hours of service. This should ideally be veried by speaking with someone in your area who is working with similar equipment. The most convenient plans involve technicians investigat­ing defects at the hospital site itself. System software upgrades should be quickly performed via USB drive, CD, or remote internet connection without requiring full hardware replacement (See Chap. 14 – Equipment Maintenance).

Image Quality

Image quality overall has improved markedly over the last decade in the point-of­care market. Having good image quality across the spectrum of patients (thin and