Qualitative evaluation of Crystal Vue rendering technology in the assessment of fetal lip and palate.
Authors: Andrea Dall’Asta1,2, Gowrishankar Paramasivam1, Christoph Lees1,3,4
1Centre for Fetal Care, Queen Charlotte's and Chelsea Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom.
2Obstetrics and Gynecology Unit, University of Parma, Parma, Italy
3Department of Surgery and Cancer, Imperial College London, London, United Kingdom
4Department of Development and Regeneration, KU Leuven, Leuven, Belgium
Address for correspondence:
Dr Christoph C. Lees, MD MRCOG
Centre for Fetal Care, Queen Charlotte’s and Chelsea Hospital, Imperial College Healthcare NHS Trust, Du Cane Road, London, W12 0HS, United Kingdom
Email:
Phone: +44 208383998
Word count in the abstract: 149
Word count in the text (references excluded): 967
Number of figures: 2
Number of supplementary figures: 7
Number of tables: 1
Conflict of interest statement
GP discloses no conflict of interest nor financial disclosures.
CCL has received honoraria for lecturing and/or consulting, loan machines and sponsorship of educational meetings by GE, Philips, Toshiba and Samsung Medison Ltd. He has research collaborations with Toshiba UK, Samsung Medison (ad hoc travel/subsistence expenses for fellows engaged on departmental research) and Medge Platforms Inc (loan of educational software).
AD has received a contribution to travel and subsistence through an unrestricted educational grant to Genesis Research Trust (registered charity n. 292518).
Abstract
Facial clefts of the lip and alveolar ridge are usually evaluated with conventional ultrasound imaging. However, assessment of the extension of the defect into the palate and the detection of isolated clefts of the secondary palate is often not always possible due to poor acoustic windows. Nevertheless, knowledge of the extent of the cleft has significant prognostic implications in terms of pregnancy choices, surgical and functional outcome.
Newly developed three-dimensional (3D) technologies offer the opportunity to develop novel imaging techniques for the evaluation of the secondary palate, although these have not been objectively compared. Crystal Vue (CV) is a recently developed ultrasound 3D post processing rendering technology based on image-contrast enhancement which is capable of preserving context and surface information. In this study we qualitatively describe its performance in the assessment of the fetal lip and palate and compare our findings to those reported using other 3D methods.
Keywords – 3D ultrasound, orofacial cleft, prenatal diagnosis, parental counseling
Orofacial clefts (OFCs) represent one of the most common fetal abnormalities, with an incidence of 1 in 500 to 1000 live births (1,2).
When there is a diagnosis of OFC, accurate antenatal counseling and assessment of the postnatal implications and management of the findings are of primary importance to the parents (3). Indeed, OFCs can be diagnosed in the context of genetic syndromes, particularly if bilateral, involving the secondary palate and associated with additional structural abnormalities or ultrasound markers (4).
The detection rate of cleft lip at screening by conventional two-dimensional (2D) US has increased over decades being as high as 65% today (4,5,6,7). Nevertheless, 2D sonography does not allow the clear visualization of the posterior or secondary palate (6,8,9). Cleft extension into the secondary palate has significant prognostic implications in terms of surgical and functional outcome (6). Three-dimensional (3D) technologies offer the unique opportunity to develop novel techniques to identify fetal facial features and allow more adequate counseling and preparation of the prospective parents. Several 3D US techniques for the assessment of the secondary palate, which comprises hard and soft palate, have been described (5,6,8,10-12) (Table 1), nevertheless no consensus exists as to the clinical superiority of any of them (10).
Crystal Vue (CV) is a rendering technology based on image-contrast enhancement which has proven to be potentially effective in differentiating between soft tissue and bony structures (13). In this descriptive imaging study we qualitatively evaluated the performances of this novel tool applied for the assessment of the fetal face.
3D US volumes from patients with known postnatal outcome were retrospectively assessed. All US scans were performed on clinical indication and volumes were anonymised. Two normal cases at 21 and 32 weeks, one antenatally diagnosed cleft lip, alveolar ridge, hard and soft palate referred at 31 weeks and one case of isolated cleft of the secondary palate postnatally diagnosed, scanned at 27 weeks for multiple fetal abnormalities, were included.
Volumes were acquired transabdominally on the midsagittal view using a 4-8 MHz probe Samsung WS-80 (Samsung Medison Co Ltd, South Korea) using criteria similar to those previously reported (5). Only datasets which were not affected by fetal movements were included for the study purposes.
Volumes were reconstructed on multiplanar mode and aligned on the axial, “reverse face” (8), coronal and sagittal plane (11). The Region Of Interest (ROI) was adjusted in order to obtain the thinnest slice. CV was overlapped to the surface rendered image; further post-processing, including Realistic Vue (RV) function, gain, transparency and light source was optimized at discretion of the examiner.
Qualitative assessment and comparison between 3D US multiplanar view and CV rendered pictures (Figures 1-2, S1-S7) was undertaken and included a dedicated questionnaire which was submitted to six European Fetal Medicine specialists.
On the coronal plane the normal hard palate, the tongue and the interpalatal suture could be imaged using CV (Figure S1). Interestingly, no differences were noted between frontal coronal view and reversed face view using CV in the normal and abnormal cases, as shown in figures S2a-c S3b respectively.
On the axial plane (figure 1), in the normal fetus, CV allowed a detailed view of the normal alveolar ridge, the hard palate with interpalatal suture and soft palate (figures 1a-c). In the abnormal case the cleft of the alveolar ridge and the palatal involvement could be imaged with higher definition using CV compared to multiplanar mode, though the soft palate could not be visualized (figure S4a-c).
On the sagittal plane, in the normal fetus at 32 weeks of gestation (figure 2), the tongue, the alveolar ridge and the hard palate were noted; the posterior portion of the secondary palate was highly likely to represent the soft palate and the oropharynx was clearly seen (figures 2a-b). Furthermore, in the second normal case, scanned at 21 weeks of gestation (figure S5), the nasal cavity, together with the nasopharynx and the base of the tongue were imaged with high accuracy using CV (figure S5b). On the other hand, in the abnormal case (figure 2c) imaging was impaired by the alveolar ridge or other abnormal echogenic structures.
Finally, the fetus with postnatal diagnosis of isolated cleft of the soft palate was retrospectively examined in coronal, sagittal, axial and coronal with reverse face planes (figures S6a-d). We could not identify the soft palate and diagnose the cleft using CV, even though a 2.7 mm gap within the secondary palate was noted (figure S7).
The same pictures were assessed and rated by six European Fetal Medicine experts. In the midsagittal plane they all agreed that the hard palate, the oropharynx, the nasopharynx, the soft palate and the root of the tongue could be imaged (figures 2b, S5b). On the axial plane, they all agreed that the soft palate was visualized (figure 1c). When assessing figure S6 they all agreed that the soft palate could not be assessed in coronal and sagittal views, and only 2/5 (40%) of them had the impression that the gap shown in figure S7 could have represented the abnormal soft palate.
Qualitative comparison between the techniques showed excellent visualization of the secondary palate using CV and particularly the soft palate could be seen with CV, but not with multiplanar view, in both the axial (figure 1c) and the sagittal planes (figs 2a,b and S5). In both cases, the presence of amniotic fluid inside the fetal mouth further improved the visualization of the anatomic details shown in figures 2b and S5b as previously reported (6).
In conclusion, in our case series imaging of the hard palate using CV appeared satisfactory in all the evaluated planes and the soft palate could be visualized. It is true that further studies are required to confirm such observations, however we believe that CV represents an advance in improving antenatal imaging of the fetal secondary hard and soft palates.
ACKNOWLEDGEMENTS
The Authors acknowledge the contribution of the Fetal Medicine experts who reviewed and rated the pictures presented in this paper: Amarnath Bhide (UK), Ilka Clemens (Norway), Torbjorn Moe Eggebo (Norway), Tullio Ghi (Italy), Tiziana Frusca (Italy), Dharmintra Pasupathy (UK).
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