|Author:||Lai, Ka Lee|
|Title:||Monitoring of spine curvature progression of adolescent idiopathic scoliosis (AIS) patients using three-dimensional ultrasound|
|Advisors:||Zheng, Yong-ping (BME)|
Spine -- Abnormalities -- Imaging
Three-dimensional imaging in medicine
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Biomedical Engineering|
|Pages:||xx, 91 pages : color illustrations|
|Abstract:||To detect curve progression of adolescent idiopathic scoliosis (AIS), X-ray examination using the Cobb method is the gold standard in clinical practice with a 5-degree increment being the cut-off threshold. Three-dimensional ultrasound imaging, which is radiation-free, has been validated for the assessment of spinal deformity in AIS by locating specific bony landmarks. Although replacing X-ray examination by ultrasound can potentially lead to significant reduction of radiation for scoliosis patients, there is a paucity of study defining the role of three-dimensional ultrasound in monitoring scoliosis progression. The objective of this study was to investigate whether three-dimensional ultrasound can provide comparable results to radiographic Cobb angle in assessing curve progression in AIS patients.|
In this study, the three-dimensional ultrasound system, Scolioscan, was first validated for its intra-rater and inter-rater reliability with 30 subjects respectively, and the results showed the measurement had excellent reliability. 200 subjects (62 male and 138 female subjects; 8-26 years of age, mean of 14.2 ± 2.8 years) with suspected AIS or diagnosed AIS of different severity (Cobb angle of 10 degrees to 85 degrees) were included for the evaluation of the feasibility of three-dimensional ultrasound in assessing scoliosis progression.
Each subject underwent bi-planar low-dose X-ray EOS and three-dimensional ultrasound Scolioscan scanning on the same date for each clinical visit. Subjects underwent second assessment with time intervals of 3-32 months. Manual measurement of scoliotic curvature was conducted by drawing lines along the transverse processes and laminae on the coronal ultrasound images obtained by the volume projection imaging method, as ultrasound transverse processes angle. Traditional Cobb measurement was conducted on X-ray images. Cobb angle and ultrasound transverse processes angle increments of five degrees or more on the maximum curvature for each subject represented scoliosis progression detected by X-ray assessment and ultrasound assessment, respectively.
The correlation between the measurements from the three-dimensional ultrasound and X-ray was examined. A strong correlation in terms of R2 value of 0.8679 was obtained between ultrasound transverse processes angle and radiographic Cobb angle for 432 curves. Using the radiographic Cobb angle as the gold standard, the sensitivity and specificity of the ultrasound transverse processes angle measurement for detecting scoliosis progression were presented. Among 200 subjects, 182 were found to possess scoliosis in the first visit or develop scoliosis in follow-up visits. Among 182 scoliosis subjects, 31 of them showed scoliosis progression in X-ray assessment while 27 of them showed scoliosis progression in both X-ray assessment and ultrasound assessment. The sensitivity and specificity of using three-dimensional ultrasound for detecting scoliosis progression were 0.87 and 0.93, respectively. The negative likelihood ratio of the diagnostic test for scoliosis progression by the three-dimensional ultrasound imaging system Scolioscan was 0.14. For the four false negative cases, the potential causes could be inconsistent postures between radiographs taken, the relatively poor ultrasound image quality on the transverse processes at the thoracic-lumbar region, and subject movement during ultrasound assessment.
This study indicated a strong correlation between the ultrasound transverse processes angle and radiographic Cobb angle with high sensitivity, specificity and low negative likelihood ratio of three-dimensional ultrasound imaging. Three-dimensional ultrasound imaging is sufficiently comparable to radiographs in monitoring scoliosis progression for the 200 subjects tested, indicating its potential for reducing AIS patient's exposure to radiation during follow-up examinations. Further studies with larger number of subjects for longer follow-up period are suggested.
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