Three-Dimensional Quantification of Cam Resection Using MRI Bone Models: A Comparison of 2 Techniques

Morphometric and clinical comparison of MRI-based synthetic CT to conventional CT of the hip in children

BACKGROUND

MRI-based synthetic CT (sCT) generates CT-like images from MRI data.

OBJECTIVE

To evaluate equivalence, inter- and intraobserver reliability, and image quality of sCT compared to conventional (cCT) for assessing hip morphology and maturity in pediatric patients.

MATERIALS AND METHODS

We prospectively enrolled patients <21 years old with cCT and 3T MRI of the hips/pelvis. A dual-echo gradient-echo sequence was used to generate sCT via a commercially available post-processing software (BoneMRI v1.5 research version, MRIguidance BV, Utrecht, NL). Two pediatric musculoskeletal radiologists measured seven morphologic hip parameters. 3D surface distances between cCT and sCT were computed. Physeal status was established at seven locations with cCT as reference standard. Images were qualitatively scored on a 5-point Likert scale regarding diagnostic quality, signal-to-noise ratio, clarity of bony margin, corticomedullary differentiation, and presence and severity of artifacts. Quantitative evaluation of Hounsfield units (HU) was performed in bone, muscle, and fat tissue. Inter- and intraobserver reliability were measured by intraclass correlation coefficients. The cCT-to-sCT intermodal agreement was assessed via Bland-Altman analysis. The equivalence between modalities was tested using paired two one-sided tests. The quality parameter scores of each imaging modality were compared via Wilcoxon signed-rank test. For tissue-specific HU measurements, mean absolute error and mean percentage error values were calculated using the cCT as the reference standard.

RESULTS

Thirty-eight hips in 19 patients were included (16.6 ± 3 years, range 9.9-20.9; male = 5). cCT- and sCT-based morphologic measurements demonstrated good to excellent inter- and intraobserver correlation (0.77

CONCLUSION

sCT is equivalent to cCT for the assessment of hip morphology, physeal status, and radiodensity assessment in pediatric patients.

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Key Words

• Hip imaging
• Hip morphology
• Hounsfield units
• MRI based
• Quality
• Synthetic CT

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MESH Headings

• Humans
• Male
• Child
• Female
• Magnetic Resonance Imaging/methods
• Prospective Studies
• Reproducibility of Results
• Adolescent
• Tomography, X-Ray Computed/methods
• Hip Joint/diagnostic imaging
• Child, Preschool
• Imaging, Three-Dimensional/methods

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Affiliation(s)

Jade Iwasaka-Neder Department of Radiology, Boston Children's Hospital, 300 Longwood Ave, Boston, MA, 02115, USA.
M Alejandra Bedoya Department of Radiology, Boston Children's Hospital, 300 Longwood Ave, Boston, MA, 02115, USA
James Connors Department of Radiology, Boston Children's Hospital, 300 Longwood Ave, Boston, MA, 02115, USA
Simon Warfield Computational Radiology Laboratory, Boston Children's Hospital, 401 Park Drive, Boston, MA, 02215, USA
Sarah D Bixby Department of Radiology, Boston Children's Hospital, 300 Longwood Ave, Boston, MA, 02115, USA

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