A reliability and validity study for Scolioscan: a radiation-free scoliosis assessment system using 3D ultrasound imaging.
BACKGROUND
Radiographic evaluation for patients with scoliosis using Cobb method is the current gold standard, but radiography has radiation hazards. Several groups have recently demonstrated the feasibility of using 3D ultrasound for the evaluation of scoliosis. Ultrasound imaging is radiation-free, comparatively more accessible, and inexpensive. However, a reliable and valid 3D ultrasound system ready for clinical scoliosis assessment has not yet been reported. Scolioscan is a newly developed system targeted for scoliosis assessment in clinics by using coronal images of spine generated by a 3D ultrasound volume projection imaging method. The aim of this study is to test the reliability of spine deformity measurement of Scolioscan and its validity compared to the gold standard Cobb angle measurements from radiography in adolescent idiopathic scoliosis (AIS) patients.


METHODS
Prospective study divided into two stages: 1) Investigation of intra- and inter- reliability between two operators for acquiring images using Scolioscan and among three raters for measuring spinal curves from those images; 2) Correlation between the Cobb angle obtained from radiography by a medical doctor and the spine curve angle obtained using Scolioscan (Scolioscan angle). The raters for ultrasound images and the doctors for evaluating radiographic images were mutually blinded. The two stages of tests involved 20 (80 % females, total of 26 angles, age of 16.4 ± 2.7 years, and Cobb angle of 27.6 ± 11.8°) and 49 (69 % female, 73 angles, 15.8 ± 2.7 years and 24.8 ± 9.7°) AIS patients, respectively. Intra-class correlation coefficients (ICC) and Bland-Altman plots and root-mean-square differences (RMS) were employed to determine correlations, which interpreted based on defined criteria.


RESULTS
We demonstrated a very good intra-rater and intra-operator reliability for Scolioscan angle measurement with ICC larger than 0.94 and 0.88, respectively. Very good inter-rater and inter-operator reliability was also demonstrated, with both ICC larger than 0.87. For the thoracic deformity measurement, the RMS were 2.5 and 3.3° in the intra- and inter-operator tests, and 1.5 and 3.6° in the intra- and inter-rater tests, respectively. The RMS differences were 3.1, 3.1, 1.6, 3.7° in the intra- and inter-operator and intra- and inter-rater tests, respectively, for the lumbar angle measurement. Moderate to strong correlations (R(2) > 0.72) were observed between the Scolioscan angles and Cobb angles for both the thoracic and lumbar regions. It was noted that the Scolioscan angle slightly underestimated the spinal deformity in comparison with Cobb angle, and an overall regression equation y = 1.1797x (R(2) = 0.76) could be used to translate the Scolioscan angle (x) to Cobb angle (y) for this group of patients. The RMS difference between Scolioscan angle and Cobb angle was 4.7 and 6.2°, with and without the correlation using the overall regression equation.


CONCLUSIONS
We showed that Scolioscan is reliable for measuring coronal deformity for patients with AIS and appears promising in screening large numbers of patients, for progress monitoring, and evaluation of treatment outcomes. Due to it being radiation-free and relatively low-cost, Scolioscan has potential to be widely implemented and may contribute to reducing radiation dose during serial monitoring.
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
Yong-Ping
YP
Zheng
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
Timothy Tin-Yan
TT
Lee
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
Kelly Ka-Lee
KK
Lai
School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
Benjamin Hon-Kei
BH
Yip
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
Guang-Quan
GQ
Zhou
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
Wei-Wei
WW
Jiang
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
James Chung-Wai
JC
Cheung
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
Man-Sang
MS
Wong
Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
Bobby King-Wah
BK
Ng
Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
Jack Chun-Yiu
JC
Cheng
Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
Tsz-Ping
TP
Lam
3D ultrasound; AIS; Cobb angle; Scolioscan; Scoliosis; Volume projection imaging