title: Challenging the in-vivo assessment of biomechanical properties of the uterine cervix: A critical analysis of ultrasound based quasi-static procedures.
abstract: Measuring the stiffness of the uterine cervix might be useful in the prediction of preterm delivery, a still unsolved health issue of global dimensions. Recently, a number of clinical studies have addressed this topic, proposing quantitative methods for the assessment of the mechanical properties of the cervix. Quasi-static elastography, maximum compressibility using ultrasound and aspiration tests have been applied for this purpose. The results obtained with the different methods seem to provide contradictory information about the physiologic development of cervical stiffness during pregnancy. Simulations and experiments were performed in order to rationalize the findings obtained with ultrasound based, quasi-static procedures. The experimental and computational results clearly illustrate that standardization of quasi-static elastography leads to repeatable strain values, but for different loading forces. Since force cannot be controlled, this current approach does not allow the distinction between a globally soft and stiff cervix. It is further shown that introducing a reference elastomer into the elastography measurement might overcome the problem of force standardization, but a careful mechanical analysis is required to obtain reliable stiffness values for cervical tissue. In contrast, the maximum compressibility procedure leads to a repeatable, semi-quantitative assessment of cervical consistency, due to the nonlinear nature of the mechanical behavior of cervical tissue. The evolution of cervical stiffness in pregnancy obtained with this procedure is in line with data from aspiration tests.
authors: Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland. Electronic address: maurer@imes.mavt.ethz.ch.
authors: M M
authors: MM
authors: Maurer
authors: Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
authors: S
authors: S
authors: Badir
authors: Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
authors: M
authors: M
authors: Pensalfini
authors: Department of Obstetrics and Gynecology, University Hospital Zurich, 8091 Zurich, Switzerland.
authors: M
authors: M
authors: Bajka
authors: Hospital Laufenburg, 5080 Laufenburg, Switzerland.
authors: P
authors: P
authors: Abitabile
authors: Department of Obstetrics and Gynecology, University Hospital Zurich, 8091 Zurich, Switzerland.
authors: R
authors: R
authors: Zimmermann
authors: Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland; EMPA, Swiss Federal Laboratories for Materials Testing and Research, 8600 Dubendorf, Switzerland.
authors: E
authors: E
authors: Mazza
mesh_terms: D001696:Biomechanical Phenomena; D002584:Cervix Uteri / Q000000981:diagnostic imaging / Q000502:physiology*; D054459:Elasticity Imaging Techniques; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008954:Models, Biological; D019047:Phantoms, Imaging; D011247:Pregnancy
keywords: Cervical consistency index; Quasi-static elastography; Ultrasound; Uterine cervix