Twin-twin transfusion syndrome (TTTS) can arise in monochorionic, diamniotic (MoDi), those identical twins arising from division of a single fertilized ovum at 4-8 days gestational age (GA) or monochorionic, monoamniotic (MoMo or Mono-Mono) twins, arising from division on day 8-13 GA.
In monochorionic twin pregnancies sharing a single placenta often unevenly, anastomoses \[connections\] artery to artery (AA), vein to vein (VV), and artery to vein (AV) can occur.
AV anastomoses usually flow unilaterally, shunting blood unevenly towards one twin and away from the other. This can lead to fluid overload and polyhydramnios along with many other pathologies in one twin while the other twin suffers from inadequate blood flow and oligohydramnios, along with secondary pathologies arising from these conditions.
TTTS will affect approximately 8-10% of MoDi twins while 6% of MoMo twins will suffer with this condition.
Treatment for TTTS is necessary, with the donor or 'pump' twin having around an 80% chance of death without medical intervention.
The aim of this single arm, unblinded, feasibility study of the Verasonics Vantage 256 device is to leverage the devices ultrafast power Doppler imaging (uPDI) to perform microvascular mapping of the placenta in healthy, non-anomalous, 18-26 week gestational age (GA), monochorionic, diamniotic (MoDi) or monochorionic, monoamniotic (MoMo/MonoMono) pregnancies without TTTS, twin reversed arterial perfusion sequence (TRAP), or maternal vascular disease.
Participants will be recruited in the Maternal Fetal Medicine department of Carilion Clinic, which specializes in high risk or complicated pregnancies. Pregnant subjects carrying monochorionic twins and scheduled for appointments at the clinic, who meet study eligibility criteria, will be approached between weeks 18 and 26 for study enrollment.
Those providing informed consent will undergo a single, transabdominal ultrasound examination by a licensed ultrasonographer or obstetrician with the Verasonics Vantage 256 ultrasound machine, with imaging focused on mapping the vasculature of the placenta with ultrafast power Doppler imaging (uPDI). The ultrasound exam will last about 15 minutes and occur immediately after the subject's standard-of-care appointment at the clinic so as not to inconvenience subjects more than necessary. Similar to commercially marketable ultrasounds in the US, the Verasonics ultrasound will use the principle of 'As Low As Reasonably Achievable (ALARA) to output the lowest acoustic waves possible to achieve the ultrasound imaging.
After the single ultrasound scan, subjects' electronic medical records will be used to source demographic, medical, obstetric, and other historical datapoints to better characterize the 10-subject study population and their babies.
No follow-up contact with subjects is expected after the single research ultrasound visit.
Subject is 18 to 45 years of age at screening
Non-anomalous, monochorionic, diamniotic (MoDi) or monochorionic, monoamniotic (MoMo) twin gestation without suspected genetic disorders
Low-risk aneuploidy screening, if performed
Intention to deliver at Carilion Roanoke Memorial Hospital (CRMH) or Carilion New River Valley Medical Center (CNRVMC)
Suspected fetal genetic disorder(s)
Suspected fetal infection(s), twin-twin transfusion syndrome (TTTS), twin reversed arterial perfusion sequence (TRAPS), or maternal vascular disease
Non-English reading and speaking
Unstable housing or transportation
Single group
Verasonics Vantage 256 Ultrasound
DeviceHealthy, pregnant subjects with nonanomalous, monochorionic twins will undergo a single transabdominal ultrasound evaluation of the placenta using the Verasonics 256 device which uses ultrafast power Doppler imaging (uPDI) as well as quantitative ultrasound (QUS) to take detailed images of the placental microvasculature.
Ultrafast Power Doppler Imaging (uPDI) Achieved with the Verasonics Vantage 256 System
Obtain 10 subjects' ultrafast power Doppler imaging (uPDI) with the Verasonics Vantage 256 research ultrasound machine that successfully visualize the placenta's microvasculature. The ability to appreciate the placental microvasculature will be determined \[Y/N\] by perinatologists working as investigators on the study.
Comparison of uPDI Ultrasound Image Resolution, Quality, and Visualization of Tertiary Villous Capillary Doppler Signals Versus Standard-of-Care Philips Ultrasound Imaging
Assessment of placental ultrasound image resolution, overall image quality, anatomical detail, and visualization of tertiary villous capillary Doppler flow obtained using the uPDI imaging system compared with images obtained using a standard-of-care Philips ultrasound device. Images will be evaluated using qualitative and descriptive assessment by perinatologists.
Feasibility of High-Quality Placental Vascular Mapping in MoDi/MoMo Twin Pregnancies Using the Verasonics Vantage 256 Ultrasound System
Assessment of the ability of the Verasonics Vantage 256 ultrasound machine to generate high-quality vascular maps of the placenta in monochorionic diamniotic (MoDi) and monochorionic monoamniotic (MoMo) twin pregnancies. Feasibility of generating these maps with the the Verasonics system and using ultrafast power Doppler imaging (uPDI) will be deemed successful if visualization of the tertiary placental vascular architecture and vessel delineation can be appreciated by perinatologists.
Ability of the Verasonics Vantage 256 Ultrasound System to Distinguish Individual Twin Placental Vasculature
Assessment of whether the placental vasculature associated with each twin can be separately identified and delineated using the Verasonics Vantage 256 ultrasound system in monochorionic twin pregnancies. Evaluation will be based on perinatologist expert evaluation of qualitative imaging criteria, assessing successful visualization and differentiation of individual vascular territories within the shared placenta.
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Carilion Clinic
Lead sponsor
Virginia Polytechnic Institute and State University
Collaborator
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