Jane Hanford – Clinical Business Development Manager Women’s Health Ultrasound – Canon Medical Systems UK explores how the evolution of high-quality ultrasound and imaging innovation, particularly SMI technology, is helping sonographers to identify potential risks early on, and in doing so – allow for more effective treatment options.
Women’s health ultrasound – where do we start?
From routine screening to high-risk assessment in obstetrics, gynaecology and breast imaging, it is critical to start with, and maintain, high image quality across ultrasound for the benefit of women’s health. Every examination is important! If we look at multiple pregnancies, and the associated risks, it is clear that superior image quality and the use of advanced applications are making a real impact in aiding diagnosis and providing clinical confidence.
Multiple pregnancies are quite literally multiplying. As of 2021, reports suggest that 1.6 million twins are born worldwide each year[i], and due to increasing maternal age and the rise in assisted reproduction, this trend is showing no signs of slowing down.
These pregnancies carry greater risks than singleton pregnancies and are often associated with increased danger of perinatal mortality and morbidity[ii]. Not only are the risks of experiencing conditions such as premature labour, pre-eclampsia, placenta abruption, and fetal growth restrictions heightened, but further complications can also arise depending on type of multiples[iii]. For medical purposes, there are three types of twins: dichorionic diamniotic (DCDA), each has their own separate placenta and separate sac; monochorionic diamniotic (MCDA), share a single placenta but have their own separate sacs; and monochorionic monoamniotic (MCMA) twins, share both a placenta and a sac – this is a much rarer type of pregnancy[iv].
Assessment of the placenta in twins is therefore crucial, and one of the most serious conditions is Twin-to-Twin Transfusion Syndrome (TTTS) – an abnormality of the placenta resulting in an unequal flow of blood – affecting 10 to 15% of monochorionic (MC) twins[v], with the risk being greater for MCDA twins. Ongoing research suggests that MC twins are also at greater risk of additional complications affecting the placenta, including Twin Anemia Polycythemia Sequence (TAPS) and Selective Fetal Growth Restriction (sFGR)[vi].
Left undiagnosed and untreated, complications such as these can lead to devastating consequences, making close monitoring throughout gestation (as often as every two weeks)[vii] – via regular, high-quality ultrasound, vital to ensuring a healthy and successful pregnancy.
Why high-end modern equipment is a must
While entry-level 2D ultrasound equipment is sufficient in determining multiple pregnancies, and the type of placentation (chorionicity and amnionicity)[viii], a high-end ultrasound machine providing optimal clarity and high-resolution detail is recommended to efficiently identify symptoms associated with any complications or abnormalities. These cases can then be referred to a Fetal Medical Consultant for further investigation and diagnosis if required.
In addition to monitoring growth regularly to identify any growth discrepancy in TTTS, sonographers typically look at the amount of fluid each baby has in the amniotic sac by measuring the depth of the deepest vertical pocket. This is to identify if there is any Polyhydramnios (excessive amniotic fluid) due to volume overload, or Oligohydramnios, (reduced levels of amniotic fluid). In a recent webinar on the topic[ix], Dr Monique Haak cited the membrane, bladder, and placenta thickness in addition to amniotic fluid as the cornerstones for diagnosis. She also revealed a common pitfall when diagnosing TTTS in MCDA twins, warning that the condition can be easily interpreted as growth restrictions in an MCMA twin pregnancy due to a lack of visibility of the inner membrane.
This is where having the most up-to-date equipment, providing fine detail and high-resolution images, is extremely important. Several reports, including consensus statements from the College of Intensive Care Medicine, NHS England, and the British Medical Ultrasound Society (BMUS) cite five years as the optimal lifespan for all ultrasound equipment[x]. While this is just a guideline, implementing the latest imaging technologies should be a priority, not only for the effective monitoring of multiple pregnancies but across all clinical applications.
Delving deeper with SMI technology
Ultimately, high-quality 2D ultrasound, right from the beginning of the pregnancy through to the later stages, is critical when monitoring for any potential complications – such as TTTS. However, should a growth restriction or other abnormality be identified, then the use of colour Doppler imaging (CDI) technology can enable the sonographer to take a closer look and interrogate the tiny vessels in the umbilical cord and placenta.
Superb Micro-vascular Imaging (SMI) technology[xi] is an award-winning Doppler technology and is proving to be extremely effective in this area.Unlike traditional colour Doppler imaging, which removes clutter from images by suppressing low-velocity components, SMI expands the range of visible blood flow from low to high velocities with incredible sensitivity.
During the examination, clinicians can easily choose SMI with the press of a button. SMI separates blood flow from overlaying tissue motion effectively, while preserving even the subtlest low-flow components with superior detail and definition – meaning that clarity needn’t be sacrificed. Compared with other colour Doppler, SMI is found to be superior in terms of high frame rate, high sensitivity, high resolution, and less motion artifact – making blood flow easier to analyse, especially when visualising the microvasculature flow of the placenta.
Predicting risk with existing ultrasound technologies
Advanced ultrasound capabilities, such as SMI, along with the Myocardial Performance Index (MPI), and Speckle Tracking Echocardiography (STE), have enabled research that has led to a better understanding of fetal and maternal physiology and pathophysiology of many conditions, and has provided focus for further studies.
Prof. Christoph Lees is currently conducting research, funded by the Medical Research Council and the Wiseman Trust[xii], to understand whether existing ultrasound technology, including SMI, can be used to look at the blood vessels within the placenta of MCDA twins. The study aims to understand how and where they join to predict the risk of developing TTTS, along with other serious complications.
This ongoing research consists of a study carried out in London in May 2019, which used a Canon Aplio i-series ultrasound machine to map placental angioarchitecture (the arrangement and distribution of blood vessels)[xiii] in MC pregnancies using different colour Doppler filters. According to Lees, placental angioarchitecture is important to determine the vascular connections in an MCDA twin pregnancy but up until now, it is rarely examined prenatally. He argues, however, that the detection and characterisation of placental anastomoses (a connection between two structures)[xiv] within the angioarchitecture could be key to identifying conditions such as TTTS or other risks.
When examining the placental vessels through the different colour Doppler modalities the results varied. While traditional CDI was impacted by sonographic “noise”, Advanced Dynamic Flow (ADF), which combined a broadband frequency with a high frame rate, allowed for a more precise depiction of blood circulation, and blood flow to be characterised. With SMI and ADF, Lees was able to view microscopic blood flow, suggesting its potential for identifying risk earlier in the future.
Overall, the study concluded that a “multi-filter” approach to angioarchitecture sonographic examination (using different colour Doppler techniques) is of fundamental assistance when characterising anastomoses and determining vascular equator in twin MC placentas.
The benefits of early identification
According to guidance provided by Dr. Surabhi Nanda for Twins Trust UK [xv], as soon as there are signs that TTTS has progressed, the mother will be referred to their regional fetal medicine unit to discuss treatment options. Whilst the options available will depend on the stage of pregnancy, Fetoscopic Laser Ablation is a common, minimally invasive treatment. This procedure focuses on the connections in the placenta causing TTTS and methodically treats them using a laser.
Laser surgery, however, is not the only option for this condition. Innovation within the ultrasound space is providing potential alternative treatments. In fact, in 2021, doctors at Queen Charlotte’s and Chelsea Hospital, Institute for Cancer Research and Imperial College London were the very first in the world to complete a successful non-invasive procedure using high-intensity focused ultrasound (HIFU) energy to safely treat a case[xvi]. This phase 1 study is nearing its target of recruiting 10 women with early onset TTTS.
For the effective monitoring of twins, as well as the diagnosis of TTTS or any other complications, the right equipment and technologies must be used from the very start. That means using ultrasound equipment that can deliver crystal-clear images with enhanced resolution. This is not only important in the case of multiple pregnancies, but also for women’s health in general, from routine screening to clinical research, assisted reproduction to high-risk assessment, gynaecological imaging to interdisciplinary assessment, and ideally all via one dedicated system. If you can deliver the precise detail needed for clinical confidence when monitoring the earliest stages of multiple pregnancies, then just imagine what else could be possible. Clearer images can mean faster examination times and a more confident diagnosis for your patient, leading to reduced anxiety and better outcomes.
[i] BBC News (2021) ‘Twins peak with more born than ever before,’ BBC News, 12 March. https://www.bbc.co.uk/news/health-56365422.
[ii] Trust, T. (2023) New statistics show neonatal death risk five times greater for twin or triplet pregnancies compared to carrying one baby. https://twinstrust.org/resource/new-statistics-show-neonatal-death-risk-five-times-greater-for-twin-or-triplet-pregnancies.html.
[iii] Website, NHS. (2022) Antenatal care with twins. https://www.nhs.uk/pregnancy/your-pregnancy-care/antenatal-care-with-twins/.
[iv] Website, NHS. (2022) Antenatal care with twins. https://www.nhs.uk/pregnancy/your-pregnancy-care/antenatal-care-with-twins/.
[v] Website, NHS. (2022) Antenatal care with twins. https://www.nhs.uk/pregnancy/your-pregnancy-care/antenatal-care-with-twins/.
[vi] COMPLICATIONS IN YOUR PREGNANCY WITH TWINS, TRIPLETS AND MORE: A GUIDE FOR PARENTS (2021). https://twinstrust.org/static/db3ab122-bcee-42c4-ab8b8e2f80053e90/e4fc85cb-1c0b-4963-8c32a6a801c7c668/Twins-Trust-Complications-Guide.pdf (Accessed: November 14, 2023).
[vii] Website, NHS. (2022) Antenatal care with twins. https://www.nhs.uk/pregnancy/your-pregnancy-care/antenatal-care-with-twins/.
[viii] NICE (2013) Quality statement 1: Determining chorionicity and amnionicity | Multiple pregnancy: twin and triplet pregnancies | Quality standards | NICE. https://www.nice.org.uk/guidance/qs46/chapter/Quality-statement-1-Determining-chorionicity-and-amnionicity.
[ix] Canon Medical Systems Europe (no date) Women’s Health Care Live Webinar – June 15 | Canon Medical Systems Europe. https://eu.medical.canon/events_calendar/webinars/womens_health_care_live_webinar_jun_2022.
[x] AXREM (2022). Manifesto for Medical Ultrasound – “The modern-day stethoscope” https://www.bmus.org/static/uploads/resources/103216_Axrem_Ultrasound_Manifesto_Final.pdf
[xi] Canon Medical Systems Europe (2023) Aplio i-series / Prism Edition – Canon Medical Systems Ltd. https://uk.medical.canon/products/ultrasound/aplio-i-series-prism-edition/.
[xii] Twin placental mapping study (July 24th, 2019). https://www.wisemantrust.co.uk/twin-placental-mapping-study/.
[xiii] ‘angioarchitecture’ (no date) TheFreeDictionary.com. https://medical-dictionary.thefreedictionary.com/angioarchitecture.
[xiv] ‘anastomoses .’ (no date) TheFreeDictionary.com. https://medical-dictionary.thefreedictionary.com/anastomoses%20.
[xv] Trust, T. (no date a) Complications. https://twinstrust.org/information/pregnancy-and-birth/complications.html.
[xvi] Trust carries out world-first non-invasive procedure to safely treat twin pregnancy complications (no date). https://www.imperial.nhs.uk/about-us/news/trust-carries-out-world-first-non-invasive-procedure-to-safely-treat-twin-pregnancy-complications.
