Use of 3D/4D Ultrasound in the Evaluation of Fetal Anomalies
Condition: Homozygous αº-thalassemia; Hb Bart's Disease
MeSH terms: Thalassemia; Congenital Abnormalities
Study type: Observational

Summary: 
      Volumetry measurements can be a potential clinical use as non-invasive tools in prenatal
      diagnosis and screening and helps to reduce the risk and complications of invasive
      procedures. 3DUS volumetry gives more precise results than 2DUS volumetry measurements,
      particularly, of irregularly shaped objects.
    

Detailed description: 
      Conventionally volume measurements can be made by using multiplanar or VOCALTM (Virtual Organ
      Computer-aided AnaLysis). Recently, a new technique, XI VOCALTM (eXtended Imaging VOCAL) has
      been described. Combined with the inversion mode, measurements for the liquid-filled
      structures can also be made. The potential use in clinical diagnosis and prediction of
      pathologies of volume measurements particularly in the first trimester are yet to be
      investigated.

      3D ultrasound is found to be superior to 2D parameter in volumetry measurement. However,
      currently, there are still very few studies done to evaluate the potential use of volumetry
      measurement in clinical practice, especially of the validity and reproducibility of XI
      VOCALTM; and the variation of results obtained within different ultrasound machines. Due to
      the potential use of volumetry measurements in clinical practice, the accuracy in volumetry
      measurement is very important and the development of new technique need to be fully explored
      so that its benefits can be fully used for the contribution of clinical practice.

      So far no research has been done to evaluate the difference in the results obtained between
      different ultrasound machines, in particularly for volumetry measurements. This is important
      because if there is no significant difference in results between difference machines, we can
      accumulate the results from these machines for a study, which can include a more variety of
      samples. Furthermore, it will be much easier to compare results of one machine with another
      for similar studies.

      Both Voluson 730 and Accuvix have been used widely in research studies on 3D volumetry but
      comparison of the results obtained from these two machines have not been done. We do not know
      whether the results generated from one machine can be extrapolated to the other machine for
      clinical or research purpose. Thus more research needs to be done in this area.

      Thus, this study is carried out to evaluate the potential use of the new modality of XI
      VOCALTM in the volumetry measurement of regular and irregular shaped objects, comparison of
      results obtained between different widely used machines, and the potential used of volumetry
      measurements in the prediction of common and important clinical pathologies such as
      αº-thalassemia.
    

Observational model: Case-Control
Sampling method: Probability Sample
Study population: 
        1. Use of XI VOCALTM in 3D fetal volumetry measurements,comparison with multiplanar and
             VOCALTM

             -restropective(2005-2007),30 singleton pregnancies,11-14 weeks' gestation, at risk of
             homozygous αº-thalassaemia.

          2. Use of XI VOCALTM in 3D placental volumetry measurements,comparison with multiplanar
             and VOCALTM

             -retrospective(2005-2007), 32 singleton pregnancies,11-14 weeks' gestation at risk of
             homologous alphaº thalassaemia.

          3. Comparison of 3DUS volumetry measurement between two models of ultrasound machine
             -prospective(December 2007-June 2008),30 singleton normal pregnancies,11-14 weeks'
             gestation.

          4. Use of 3DUS in fetal, gestational sac and placenta quotient measurement, fetuses at
             risk of homozygous αº-thalassemia(Hb Bart's disease) -retrospective(datasets July
             2007-Dec 2008),singleton pregnancies,11-14 weeks' gestation,26 affected cases,34
             unaffected cases,43 normal control.
      
Keywords: 3D, 2D, ultrasound, volumetry, multiplanar, VOCALTM, XI VOCALTM, fetal, gestational sac, placenta