E1710. Sono-Elastography of Cervix in Pregnancy: Hope or Hype?
Mirror Health Pvt Ltd
Sono-elastography of cervix determines the stiffness of cervix non-invasively and can be complimentary to cervical length measurement.
Cervical softening / weakening, a final common pathway in varied conditions, like previous mid-trimester abortions / preterm delivery, elderly primigravida, clinically suspect cervical incompetence due to prior intervention, recurrent infections due to uncontrolled gestational diabetes, collagen vascular diseases, dynamic os etc, even without a short cervix. Soft cervix in 'at risk' women increases the risk further (even with adequate cervical length) without appropriate management. Color-coded elastography image is used to obtain the parameters elasticity contrast index (ECI), elasticity at the internal os (IOS), elasticity at the externa os (EOS), Hardness ratio, elasticity ratio (IOS/EOS) and the cervix length. ECI and hardness ratio correlate with consistency of the cervix, with the higher and lower values respectively of these two parameters corresponding to a soft cervix.
This is a more objective and reproducible evaluation method of cervical consistency in pregnant women.
Educational Goals / Teaching Points
Introduction to elastography - palpation imaging.
Basic physics and types - compressibility of tissues in response to external force (strain technique) and velocity of shear waves in the tissue (shear wave technique).
Physical basis to cervical sono-elastography - softer cervix is more compressible by external forces. Harder the cervix, lesser risk of spontaneous preterm delivery.
Techique - how do I do it? - Hardware, image acquisition, processing and interpretation of information with examples.
Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Uterine cervix sustains the stress of enlarging uterine contents only till it remains hard and long. Non-invasive parameters like cervical length and assessment of the utero-cervical angles are morphological. Stiffness (and ripening), the other significant component of the cervix is assessed objectively by sono-elastography.
Cervical softening is the final common pathway in response to varied conditions with clinical dilemma in a pregnant woman, particularly in high risk obstetrics practice, which can lead to opening up of internal os and abortion / preterm delivery if not treated.
Transvaginal ultrasound is performed and color-coded elastography image is used to obtain the elastography parameters ECI, IOS, EOS, Hardness ratio, ratio of elasticity at the internal and external os (IOS/EOS) and the cervix length.
The color ranges between red to purple, red being hard and purple being soft. Cervix is considered to be soft when ECI is higher and hardness ratio is lower.
While today’s clinical practice involves subjective digital examination of the cervix and cervical length assessment, the available literature supports integration of various quantitative parameters like sono-elastography to directly and robustly evaluate characteristics of an individual cervix. Standardization of the methods and equipments and regular use with development of specific institutional reference values for the elastography parameters may be the way forward.