Korean J Radiol.  2019 May;20(5):812-822. 10.3348/kjr.2018.0545.

MRI Evaluation of Suspected Pathologic Fracture at the Extremities from Metastasis: Diagnostic Value of Added Diffusion-Weighted Imaging

• Park SY
• Lee MH
• Jeon JY
• Chung HW
• Lee SH
• Shin MJ

• KMID: 2442715
• DOI: http://doi.org/10.3348/kjr.2018.0545

Abstract

OBJECTIVE
To assess the diagnostic value of combining diffusion-weighted imaging (DWI) with conventional magnetic resonance imaging (MRI) for differentiating between pathologic and traumatic fractures at extremities from metastasis.
MATERIALS AND METHODS
Institutional Review Board approved this retrospective study and informed consent was waived. This study included 49 patients each with pathologic and traumatic fractures at extremities. The patients underwent conventional MRI combined with DWI. For qualitative analysis, two radiologists (R1 and R2) independently reviewed three imaging sets with a crossover design using a 5-point scale and a 3-scale confidence level: DWI plus non-enhanced MRI (NEMR; DW set), NEMR plus contrast-enhanced fat-saturated T1-weighted imaging (CEFST1; CE set), and DWI plus NEMR plus CEFST1 (combined set). McNemar's test was used to compare the diagnostic performances among three sets and perform subgroup analyses (single vs. multiple bone abnormality, absence/presence of extra-osseous mass, and bone enhancement at fracture margin).
RESULTS
Compared to the CE set, the combined set showed improved diagnostic accuracy (R1, 84.7 vs. 95.9%; R2, 91.8 vs. 95.9%, p < 0.05) and specificity (R1, 71.4% vs. 93.9%, p < 0.005; R2, 85.7% vs. 98%, p = 0.07), with no difference in sensitivities (p > 0.05). In cases of absent extra-osseous soft tissue mass and present fracture site enhancement, the combined set showed improved accuracy (R1, 82.9-84.4% vs. 95.6-96.3%, p < 0.05; R2, 90.2-91.1% vs. 95.1-95.6%, p < 0.05) and specificity (R1, 68.3-72.9% vs. 92.7-95.8%, p < 0.005; R2, 83.0-85.4% vs. 97.6-98.0%, p = 0.07).
CONCLUSION
Combining DWI with conventional MRI improved the diagnostic accuracy and specificity while retaining sensitivity for differentiating between pathologic and traumatic fractures from metastasis at extremities.

Keyword

Functional MRI; Diffusion; Fracture; Neoplasm metastasis; Extremities

MeSH Terms

Cross-Over Studies
Diffusion
Ethics Committees, Research
Extremities*
Fractures, Spontaneous*
Humans
Informed Consent
Magnetic Resonance Imaging*
Neoplasm Metastasis*
Retrospective Studies
Sensitivity and Specificity

Figure

• 

  Fig. 1 Study flowchart.CE = contrast-enhanced, CE set = NEMR plus CE fat-saturated T1-weighted imaging, Combined set = DWI plus CE set, DWI = diffusion-weighted imaging, DW set = DWI plus NEMR, MRI = magnetic resonance imaging, NEMR = non-enhanced MRI

• 

  Fig. 2 CE and combined sets demonstrate correct diagnosis of pathologic fracture by both readers at left femur in 55-year-old woman with multiple myeloma.(A) Axial T1-weighted, and (B) axial contrast-enhanced fat-saturated T1-weighted images show intramedullary enhancing single bone abnormality at fracture site with perilesional edema (asterisks). (C) Corresponding axial DWI shows high signal change at fracture site (b = 1400 s/mm2). (D) Axial ADC map shows impeded water diffusivity. ADC = apparent diffusion coefficients

• 

  Fig. 3 CE and combined sets demonstrate discordant interpretations of traumatic fracture at left femur in 56-year-old woman with vaginal cancer.Initial diagnosis of reader 1 from CE set was pathologic fracture due to focal bone abnormality on T1-weighted images with enhancement at fracture margin, in which DWI is added to CE set, reader 1 changed diagnosis to traumatic fracture. (A) Coronal T1-weighted and (B) axial contrast enhanced fat-saturated T1-weighted images show single bone abnormality with bone marrow enhancement at fracture site in left proximal femur, neck (arrows). (C) Corresponding axial DWI shows no high signal at fracture site (b = 1400 s/mm2). (D) Axial ADC map shows no impeded water diffusivity. This case was pathologically confirmed as intramedullary hemorrhage with traumatic fracture.

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