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Development and validation of a bespoke phantom to test accuracy of Cobb angle measurements

Alrehily, F; Hogg, P; Twiste, M; Johansen, S; Tootell, AK

Development and validation of a bespoke phantom to test accuracy of Cobb angle measurements Thumbnail


Authors

F Alrehily

S Johansen

AK Tootell



Abstract

Introduction: Adolescent idiopathic scoliosis (AIS) is a spinal deformity that causes the spine to bend laterally. Patients with AIS undergo frequent X-ray examinations to monitor the progression of the disorder by through the measurement of the Cobb angle. Frequent exposure of adolescents poses the risk of radiation-induced cancer. The aim of this research was to design and build a bespoke phantom representing a 10-year-old child with AIS to allow optimisation of imaging protocols for AIS assessment through the accuracy of Cobb angle measurements.

Method: Poly-methyl methacrylate (PMMA) and plaster of Paris (PoP) were used to represent human soft tissue and bone tissue, respectively, to construct a phantom exhibiting a 15olateral curve of the spine. The phantom was validated by comparing the Hounsfield unit (HU)of its vertebrae with that of human and sheep. Additionally, comparisons of signal-to-noise ratio (SNR) to those from a commercially available phantom. An assessment of the accuracy of the radiographic assessment of the Cobb angle measurement was performed.

Results: The HU of the PoP vertebrae was 628 (SD= 56), human vertebrae was 598 (SD= 79) and sheep vertebra was 605 (SD= 83). The SNR values of the two phantoms correlated strongly (r = 0.93 (p = 0.00)). The measured scoliosis angle was 14 degrees.

Conclusion:The phantom has physical characteristics (in terms of spinal deformity) and radiological characteristics (in terms of HU and SNR values) of the spine of a 10-year-old child with AIS. This phantom has utility for the optimisation of x-ray imaging techniques in 10 year old children.

Implications for practice: A phantom to investigate new x-ray imaging techniques and technology in the assessment of scoliosis and to optimise currently used protocols.

Citation

Alrehily, F., Hogg, P., Twiste, M., Johansen, S., & Tootell, A. (2020). Development and validation of a bespoke phantom to test accuracy of Cobb angle measurements. Radiography, 26(2), e78-e87. https://doi.org/10.1016/j.radi.2019.11.002

Journal Article Type Article
Acceptance Date Nov 10, 2019
Online Publication Date Nov 25, 2019
Publication Date May 1, 2020
Deposit Date Nov 13, 2019
Publicly Available Date Nov 25, 2020
Journal Radiography
Print ISSN 1078-8174
Electronic ISSN 1532-2831
Publisher Elsevier
Volume 26
Issue 2
Pages e78-e87
DOI https://doi.org/10.1016/j.radi.2019.11.002
Publisher URL https://doi.org/10.1016/j.radi.2019.11.002
Related Public URLs https://www.radiographyonline.com/

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