The quality and safety of our equipment is our top priority, and as a dedicated ultrasound company run by specialists, we take this responsibility seriously. Just as we source equipment through careful field testing by sonographers, feeding back necessary changes to manufacturers to ensure all of our machines are optimised for their intended use, we also make sure the safety readings on our scanners are true and accurate.
How is the mechanical index measured?
Ultrasound transducers send out pressure waves which oscillate between positive and negative pressures. It is this rapid pressure oscillation that has the potential to cause biological harm. Extreme negative pressures can bring gas out of solution in the blood and tissue, which can then explode as the pressure rapidly rises: similar in concept to the way that a diver gets ‘the bends’ from a rapid change in pressure.
The mechanical index is calculated from the peak negative pressure of the ultrasound beam (adjusted to account for the level of attenuation that would be expected in soft tissue), divided by the square of the frequency. It should be calculated and monitored by all ultrasound machines, should ideally be displayed on screen for the operator to monitor, and should never exceed 1.9 for normal ultrasound scans. For pregnancy scanning, users should be even more cautious.
An ultrasound transducer’s mechanical index (MI) is measured using a hydrophone in a water tank, which is lined up with the beam. An oscilloscope displays the waveform, pictured below. From this, you can see that it is true that an ultrasound transducer emits a pulse of ultrasound, consisting of more than one cycle.
The MI of the two scanners tested was well below 1, which makes them ideally suited for abdominal scanning in small animals.
Finger On Pulse Ltd. (trading as PortableUltrasoundMachines) was awarded its trademark on the 22nd of January 2021, protecting the ‘ScanX’ name for the next ten years.
The ScanX ultrasound machine utilises the much-loved ScanPad software and interface, but has been adapted for use on a portable, WiFi-enabled tablet device.
While no trademark or design right registration will ever prevent others from copying, this trademark can reassure customers and partners that they are buying “the real thing” and enables us to continue our work and investment in improving the ScanX® year upon year. The ScanX® project has already put together an international team of professionals from England, Egypt, Brazil, Romania and The Philippines, and the software and hardware is being improved all the time. Our goals for the next two years include:
- All software development and coding moved in-house, here in the United Kingdom
- Integration of new artificial intelligence systems to support users, developed in the United Kingdom in partnership with our most trusted users and partners in the UK, USA and Canada
- Sourcing of all transducer components from the UK, Europe and the United States.
The ScanX® ultrasound machine will be distributed directly through the portableultrasoundmachines.co.uk website, and through select partners/distributors. Please note that PortableUltrasoundMachines is a separate company to those whose systems we also distribute: i.e. we are separate and independent from SIUI, Kai Xin, or Vet Image Solutions (VIS).
A comparison of image quality between the ScanPad transducer and software (run via the ScanX interface), and Apogee 1000 Lite.
These two comparison scans were performed on the same pregnant guinea pig, just over one week apart. In the first set of images, pregnancy can be quickly and easily confirmed on the ScanX, but the higher resolution of the Apogee system really shows in the detail and crispness of the tissue boundaries.
In this next set of images taken eleven days later, strong heartbeats can be seen with the ScanX, with the skull and spines of the pups clearly visible. The Apogee 1000 Lite really takes things up a level when it comes to detail, however; highlighting every rib, and you can even see the brain inside the fetal skull.
It’s important to also stress that both of these scanners were operating at very low power settings. You can read more about how to safely scan very small animals in this article from the Animal Ultrasound Association.
This year saw the launch of the new ScanPad+ ultrasound machine – to the delight of some, and the dismay of others. It followed months of Coronavirus-induced supply issues, as parts suppliers of the original machine fell by the wayside or suffered unprecedented delays. This was by no means exceptional during this time, and was a phenomenon that affected supply chains all around the world. This was compounded by a surge in demand from online companies, overloading shipping and delivery companies, which only added to delays.
The only way to continue to produce the ScanPad was to raise prices significantly, and so VIS (the creators of this machine) decided that the only viable option was to introduce the ScanPad+. This machine saw the introduction of a number of improvements that North American clients, in particular, had been asking for.
Key differences between the ScanPad+ and ScanPad
The main goal behind the creation of the ScanPad+ was to change as little as possible. The ScanPad is arguably the best selling ultrasound machine for small animal pregnancy scanning worldwide, and the number of imitation products both at home and abroad is a testament to its success. For that reason, the software, main board and transducers remain completely unchanged in the new unit. The main differences are:
- Much sturdier case: This is something that people who tend to scan outdoors had been asking for for years, particularly goat breeders in the USA and dog breeders in Canada.
- Custom-made carry case: Finding an appropriate carry case for the ScanPad was always problematic, so the ScanPad+ can be ordered with a case designed especially for this machine.
Above: Original ScanPad (left), and the new ScanPad+ (right), launched 2020.
What about the ScanX?
The ScanX ultrasound machine is a new product that will officially launch in January 2021, although a few people have taken advantage of currently discounted pricing to buy theirs now (current lead time of one week). The aim of the ScanX is to improve upon two main weaknesses of the ScanPad or ScanPad+:
Portability: Some people argue that the increased robustness of the ScanPad+ comes at a price: it’s a bulkier, heavier machine than before (4.8kg / 10.5lbs). In addition, the battery life of the ScanPad series has never been impressive, nor is it meant to be. The battery is there as an emergency backup for a machine that’s designed to be run from the mains. The ScanX, in comparison, is super lightweight (well under 1kg / 2.2lbs), with a battery that will keep you scanning for at least five hours.
Service and repair: The collapse of global supply chains during the first wave of the Coronavirus pandemic was a huge wake-up call. In countries like the UK, USA and Canada, we rely heavily upon trade with other nations, and when component suppliers cease trading, increase prices or shipping gets delayed, it causes major problems. While the interconnectedness of our world means we can never eliminate this completely (nor would we want to), there are steps we can take to improve things:
1) On the computing side, the ScanX is powered by systems designed and supported by big companies with a strong presence in the United Kingdom and North America (e.g. Microsoft).
2) The ScanX software is coded and supported from right here in London.
3) Training and technical support can be delivered remotely, from London and from our amazing Clayton in Brazil who is on the same time zone as most of our American clients.
4) Our high resolution transducers are assembled and printed in Surrey, England.
This reduction in the number of external components also means that there is less to ‘go wrong.’ No more waiting on spare parts – both the tablet and transducer are individually warrantied and, in the event of a malfunction under warranty, you would simply receive a replacement. If your tablet device were ever to fail outside of warranty, the fantastic thing about the ScanX is that the software can be installed on any Windows or Android device, enabling you to carry on scanning.
Of course, the ScanX won’t suit everyone. One of the most popular features of the ScanPad range is the huge 15″ screen – something that is inevitably lost on a more portable unit (the ScanX screen is 10.5″). You can learn more about the ScanX Ultrasound Machine here.
Comparison of a feline kidney imaged first with a microconvex (at 5.2MHz, with harmonics turned on) and then with a linear probe (at 12MHz) on the Siui Apogee 1000 Lite.
Below is the same structure in a French Bulldog, imaged on three leading ultrasound machines, all of which are popular for abdominal scanning in small animals – and particularly for canine pregnancy scanning.
This highly portable machine is popular with fertility clinics and well-established mobile pregnancy scanning businesses who demand the best.
The below image was taken with harmonics turned on, at 4.5MHz.
The ScanX ultrasound machine comes with its own software app, allowing you to run it off any Windows laptop or Android device.
This was taken with a microconvex probe, at 6.5MHz.
The Elite 5600 is a popular entry level machine for dog pregnancy scanning due to it ease of use, reliability, and excellent image quality for a sub-£2000 scanner.
It was set at the highest frequency available with its default convex probe (higher frequency microconvex probes are available upon request).
We generally think of mechanical sector scanners as outdated technology. Yes; they’re still on the market and popular with people needing an ultrasound machine for pregnancy scanning on a limited budget, people who are new to scanning and unaware of the limitations of this technology, and a handful of loyal affectionados who simply want to stick with what they know. Compared to when I first began working with ultrasound ten years ago, though, they’ve very much fallen out of fashion.
Even their last remaining stronghold – farm use – is in sharp decline. Old school sheep scanning professionals with their trusty twenty year old machines are beginning to retire, and veterinarians who have scanned for decades have almost all updated their ultrasound machines at this point.
It came as a surprise to me, therefore, to read in the journal ‘Theriogenology’ that a mechanical sector rectal probe outperformed a linear array for ovum pickup in cows. Granted, the paper was published in 2004 and the resolution of electronic transducers is now far better, but even so, the fact that a mechanical probe allowed visualisation of a greater number of follicles under 5mm in size was surprising. How is this possible, when the spatial resolution of probes with electronic beamforming is invariably superior to fixed-focus mechanical probes?
Rather than having better resolution, it is likely that the mechanical sector probe is simply more practical for this application due to its wider field of view, allowing for better positioning and therefore visualisation of the ovary. Indeed, the authors report that previous studies found “a restricted view of some portions of the ovary using a linear array transducer.” Thus, the lower follicle count is likely not due to resolution, but to the ease of interrogation of the structure.
It is also worth noting that the researchers controlled for frequency, i.e. they set both transducers at 5MHz. However, one of the main strengths of electronic transducers is that they have a range of frequencies, and increasing the frequency on the linear array transducer may have improved performance.
What this study does highlight, however, is the fact that there is still a place for mechanical sector technology for niche applications, even if they’ve lost their place for mainstream uses like canine pregnancy scanning. Mechanical sector scanners like the MSU3 offer a tough, robust option for pig pregnancy scanning, for example – and also operate at just the right frequencies for this job.
Bols et al., 2004. A comparison of a mechanical sector and a linear array transducer for ultrasound-guided transvaginal oocyte retrieval (OPU) in the cow. Theriogenology 62(5):906-14.
Portable ultrasound devices are ideally suited for lung ultrasound, as they can be more easily disinfected between patients than full sized trolley-based machines. Machines like the Apogee 2300 and Apogee 1000 Lite have been at the forefront of lung imaging in China during the outbreak, and we will begin to see an increase in interest and demand across Europe. The Apogee 2300 has been extensively used to assess the lung, as well as to provide guidance during intubation and to avoid puncture injuries in patients in critical shock. This is the machine we have used to illustrate this article.
The most common findings so far reported in COVID-19 patients are:
- Consolidated lung
- An irregular pleural line
The best transducer types for lung ultrasound are phased array and convex probes. Linear probes can also be used, but will lack penetration much further than the pleura.
Normal lung ultrasound findings
In normal patients (as well as in other conditions like asthma and COPD – but not COVID-19), the bright white echogenic pleural line will be reverberated down the screen. Each A line is equidistant from the next.
In normal patients, lung ‘sliding’ can be seen with regular breathing. This is the parietal pleura sliding against the visceral pleura.
- B-lines: In patients with interstitial pneumonia and diffuse alveolar damage, B-lines will be seen. There are vertical lines which arise from the pleural line, and extend all the way down the screen, obscuring A-lines. Their number increases with decreasing air content. At least 3 B-lines must be seen between a single rib space for a positive diagnosis. See Gargani (2011) for example images. With pulmonary oedema, B-lines are seen universally, but a characteristic of Covid-19 appears to be its patchy distribution. It is important, therefore, to check the patient from multiple views.
- Thickened and irregular pleural lines have been reported in COVID-19 patients, which may also be accompanied by lack of sliding. There may also be hypoechoic (dark) regions within the pleura.
- Consolidated areas of lung have also been reported. This is also referred to as ‘lung hepatisation,’ because the lung appears similar in density to the liver. The alveoli become filled with fluid, allowing the ultrasound energy to pass through without excessive scattering and loss, returning to the probe to create an image.
Pleural effusions are less common in Coronavirus patients. If you discover pleural effusions, first consider an alternative diagnosis.
Gargani, L. (2011). Lung ultrasound: a new tool for the cardiologist. Cardiovascular Ultrasound, 9.