Freehand 3-dimensional ultrasound imaging of midpalatal suture in maxillary transverse deficiency treatment: an ex vivo study

Abstract

Objective

Rapid maxillary expansion is widely regarded as the treatment of choice for correcting maxillary transverse deficiency (MTD), a significant concern in the facial growth of children and adolescents. A critical component of the rapid maxillary expansion treatment process involves the precise evaluation of the patency of the midpalatal suture (MPS). Ionizing radiation-based modalities are commonly employed to assess the status of the MPS. This study proposes a nonionizing radiation method to measure the MPS opening using freehand 3-dimensional intraoral ultrasound (US) reconstructed images.

Study Design

The US imaging system includes a portable customized high-frequency scanner, accompanied by 4 infrared cameras that record the corresponding image coordinates and orientation. A 3-month-old pig palate with a manmade defect mimicking the MPS expansion was freehand scanned and real-time reconstructed to generate 3-dimensional images. The palatal bone underlying the ruggae was then segmented to unveil the MPS expansion. A micro-computed tomography (μCT) scan was performed on the pig jaw to establish the ground truth. The widths of the MPS opening were measured 3 times at 10 different locations spaced 1.5-mm apart along the MPS on the US-reconstructed images. The results were validated by μCT data.

Results

The MPS width comparison between US and μCT measurements shows a strong correlation of R^b = 0.99 (P < .05) and absolute errors of less than 0.19 mm (6 %). In general, 95% of the difference between the measurements fell between -0.27 mm and 0.07 mm, which is clinically acceptable. The results revealed good accuracy in measuring MPS opening using US in comparison with μCT.

Conclusion

This study has demonstrated the feasibility of examining the MPS patency by 3D intraoral US-reconstructed images. The technique holds great promise in providing a low-cost, safe, and highly accurate modality for MTD treatment.