"Stop – you have reached your destination."
With increasing traffic in healthcare centers, clinics face many challenges. Ultrasound-guided devices can allow clinicians without ultrasound expertise to easily integrate sonography into their workflow for needle placement, cannulas, and other invasive medical devices and procedures. Battery-powered, high-computing-power portable imaging systems allow for increased medical device flexibility, effectiveness, and safety.
Invasive procedures are common in operating theatres, intensive care units, emergency rooms, and diagnostics. Doctors use them to inject drugs such as painkillers and anaesthetics, or to take synovial fluid, blood, or tissue samples. These procedures are simply indispensable for medical diagnosis and treatment.
During an invasive procedure, a needle or other sharp instrument pierces the skin and enters into body tissue. It needs to travel past nerves, blood vessels, and other internal body parts to reach the often minute target area. But how can the needle accurately get to a deep-lying vein or the precise pain point? Even if the needle only penetrates the body a few centimetres, "flying blind" through the body is risky, with possible side effects ranging from bruising to a stroke.
The risk of injury is reduced if the needle’s path past blood vessels, nerves, and tendons is planned in advance and made visible (Figure 1). Navigated procedures are more successful and safer for the patient. They are recommended by national health organizations, such as the National Institute for Health and Care Excellence (NICE) or the Society of Cardiovascular Anesthesiologists. Successful treatment means faster recovery and greater patient satisfaction. As a result, patients leave the hospital sooner and with less complications, leading to cost savings.
Better imaging thanks to ultrasound
Ultrasound has been used in diagnostic tests for a long time. Almost every baby's size or position has been determined by ultrasound. In general, this technology is perceived as safe. The exposure to contrast agents or radiation that occurs with other imaging techniques is eliminated. During an ultrasound check, a transducer moves back and forth or rotates over the skin. It sends ultrasonic waves into the body and receives the reflected signals. These vary depending on the structure of the targeted tissue. From these signals, a 2D image (plane) showing vessels, organs, structures, and fluids is generated. Sounds easy? Unfortunately, it’s not always been plain sailing. In the past, astronomical prices and high training costs formed a barrier to the use of ultrasound-assisted technologies in the clinical setting.
Staying on course with coordination and skill
Ultrasound-guided procedures are complex and require a high degree of coordination and skill from the operator. While one hand sounds out the target area, the other hand drives the needle through the tissue. The success depends on the clinician’s skill and experience. The inexperienced find it difficult to track the needle with the help of the ultrasound image, and they run the risk of inserting the needle past its target point.
A 2D journey through the 3D maze
One of the challenges for the navigation system is that the needle is mapped in a 2D image plane as it makes its way through the 3D tissue (Figure 2). Traditionally, there are two approaches: the in-plane vs. the out-of-plane method.
With the in-plane approach, the needle moves parallel to the ultrasound beam. In other words, the angle between the needle and the plane is 0 degrees. The needle is visualized as a line. If the needle diverges from its parallel route or if it revolves along the axis, this is not visible in the picture. As a result, it is easy to underestimate the depth of penetration. The in-plane approach is therefore of limited use for deep-lying targets.
With the out-of-plane approach, a portion of the beam is deflected at an angle. This ensures that it is possible to track the needle even as it penetrates deeper into the tissue. While an angled beam makes it easier to visualize the needle, it remains difficult to assess the exact needle position. What exactly does the dot in the ultrasound image represent? Is it the tip of the needle or the point where the needle meets the ultrasound plane? Therefore, some procedures use modified needles with built-in sensors. These special needles are often thicker and manufacturer-specific. Proprietary needles limit clinicians in their choice of needle gauge, length, and bevel type. Another disadvantage of some special needles lies in the fact that they need to be manually disconnected from the sensor after reaching their target position in order to connect the syringe or injection tube. This may cause the needle to deviate from its original and optimal position, increasing the risk of injury in tricky procedures. Another option is needle guides that fix the needle’s direction and angle. The downside is a limited freedom of movement for the practitioner.
Exploring new methods
The traditional methods of using 2D imaging to find a 3D route requires great experience, skill, and coordination from the clinician. Until he masters this art, much training is needed and the risks remaining for the patient are not trivial. And because proprietary needle systems restrict the choice of the appropriate instrument, ultrasound-guided medical device company eZono has followed a different route.
A long requirements list
The interdisciplinary eZono team analysed the concerns and needs of hospital staff. Their ideal device needed to be compact and portable. It also had to be capable of battery operation in case there was no power outlet nearby. In point-of-care diagnostics, devices are often used at the bedside or in consulting rooms. Here, the need for a device that is easy to operate and can be used without much training was particularly strong. Additional requirements included a device that provides reliable information about the position and depth of the needle, and a device that eases the workload while using familiar syringes and instruments. All this needed to be done without the need to use additional plug-ins or extension modules. Plus the device needed to increase safety, both for the patient and for the inexperienced operator. The result was a completely new approach to ultrasound-guided navigation in the eZono 4000.
Magnetic route planning
Instead of special needles with built-in sensors, magnetized standard needles can be used. Most standard needles contain enough metal for them to be magnetized sufficiently. The magnetization process is simple: The needle is briefly placed into a small, sterile plastic cup with two built-in magnets.
Adaptive needle detection automatically calibrates the system for the selected needle. The transducer incorporates a needle tracking system that collects the position data of the magnetized needle and measures the signal strength of the reflected soundwaves. Algorithms convert the measured values into 3D data. In addition to tracking the needle’s path through the tissue, the depth of insertion is visualized. This requires complex algorithms to turn the raw measurement data of the hardware into a meaningful image in real time; computing in the eZono 4000 is conducted with congatec AG's conga-BAF module.
Visibility from any angle
As the needle moves through the tissue, eZono 4000's patented needle guidance technology eZGuide FreePlane Navigation visualizes its direction and the location of the tip of the needle relative to the imaging plane in real time. The operator can clearly see where the needle is and when it has reached the target area. Coloured indicators in the ultrasound image further facilitate needle guidance. A target corridor indicates whether the needle is on the right track. This makes precise needle positioning possible, both for the in-plane and out-of-plane approaches.
Meeting healthcare requirements
The ultra-sound guided needle system meets the healthcare setting needs of size, portability, functionality, and ease of use.
Compact and portable
Weighing in at 4.7 kg, the eZono 4000 meets the requirement for a small, portable device. It is reminiscent of a tablet PC (Figure 3).
Point-of-care diagnostics at the bedside or in practice rooms
The device can be mounted on a trolley or placed freestanding on any surface, supported by its rear stand. Accessories such as quick release VESA mounts or special trolleys are available.
To enable use on the move, the device comes with a battery. In battery mode, the device can operate for approximately 2.5 hours; this is long enough to carry out several consecutive procedures without recharging the battery. The compute-intensive graphics applications require high-performance processors while battery operation needs low power consumption. Both software and hardware are therefore optimized for energy efficiency – fulfilled by the conga-BAF-module's energy-efficient yet powerful AMD Embedded G-Series APU platform.
The system is operated via a multi-touch 12.1" display. Users are familiar with this type of interface from their tablets and smartphones. There are many soft keys to control important functions and settings. The display shows brilliantly sharp images; even when lighting conditions are poor, which is a common issue in point-of-care applications, the images are clear in 256 shades of grey. The device boots up in less than 20 seconds from standby mode, and even a full start up takes barely a minute. Preparation of the standard needles with the magnetizing cup is simple, sterile, and quick. The sealed surfaces can be disinfected efficiently; this is an important point when it comes to meeting the strict hygiene requirements of the medical environment. Easy cleaning and the use of standard needles also have a positive impact on the cost of ownership.
Short learning curve
Educational Cue Cards provide information and help for any kind of procedure (Figure 4). This integrated training method bridges the gap between teaching and practical clinical application. It covers the basics of ultrasound examinations, vascular access, local anaesthesia, rescue blocks, musculoskeletal system disorders, pain management, and many other topics. The Cue Cards can be expanded with new, customer-specific topics.
Reliable information about the position and depth of the needle
Adaptive needle tracking and a selection of display modes facilitate assessment. The position of the needle tip can be correctly identified both with the in-plane and out-of-plane method.
Benefits of a COM Express solution
Modern specialist medical devices require a high-performance computer, yet the computer in such a device is only the means to an end. The real know-how lies in the medical technical application. Designing a processor board is a complex job and a draw on resources that would be better used for application-specific tasks. When using computer-on-modules (COMs), the computer part is available off-the-shelf so the focus can shift back to core competencies. COM Express is one of the leading module standards and is supported by many module manufacturers. In addition to the processor, a COM module also contains the entire periphery and supply. The COM module is a full-fledged computer that is mounted onto a custom carrier board that contains the application-specific properties. This approach provides several advantages. The crucial know-how remains in-house while computer specialists such as congatec or other COM vendors develop and manufacture the ready-made, pre-integrated modules. Commercial challenges, such as product discontinuations or new processor generations, are easier to handle when using COM modules. The use of standard modules guarantees long-term device availability; it also saves time and money because tested, proven, and certified components in industrial quality are readily available.
A clever, low-power brain
The conga-BAF COM Express module provides a mix of computing performance, graphics features, and power efficiency. The low power draw allows battery operation and the unit also functions well without fan cooling. To deliver the complex tasks of needle navigation and visualization, high computing power and excellent graphics were an absolute must. The space-saving and power-efficient two-chip AMD Embedded G-Series APU platform includes a powerful multicore processor along with a graphics unit that offers the functionality of a dedicated graphics card at the chip level (Figure 5). This high level of integration also provides the basis for powerful image processing and quick visualization. With the APU architecture, certain computing tasks can be outsourced to the integrated graphics unit to relieve the CPU. This results in latency-free operation and display. Using standardized graphics libraries such as OpenGL and OpenCL, it is possible to outsource compute-intensive image processing algorithms to the graphics unit for user-friendly presentation.
Improving medical devices for invasive procedures
In invasive medical procedures, ultrasound-guided navigation increases patient safety by lowering the risk of complications. Treatment efficiency is increased because interventions can be carried out faster and more easily. The training effort is low and clinicians with little experience in ultrasound technology master this navigation technique safely after a short training period. The use of standard needles pays off twice: First, these are proven, familiar instruments; and second, their ready availability translates into a clear cost advantage. The treatment is faster, first attempt success rates are higher, and the incidence of artery injuries is lower than with straight landmark-based procedures.