Abstract
PurposeTo compare and combine the diagnostic performance of the apparent diffusion coefficient (ADC) derived from diffusion-weighted imaging (DWI) and proton density fat fraction (PDFF) derived from chemical-shift encoding (CSE)-based water-fat magnetic resonance imaging (MRI) for distinguishing benign and malignant vertebral bone marrow lesions (VBML).MethodsA total of 55 consecutive patients with 53 benign (traumatic, inflammatory and primary) and 36 malignant (metastatic and hematologic) previously untreated VBMLs were prospectively enrolled in this IRB-approved study and underwent sagittal DWI (single-shot spin-echo echo-planar with multi-slice short TI inversion recovery fat suppression) and CSE-based MRI (gradient-echo 6‑point modified Dixon) in addition to routine clinical spine MRI at 1.5 T or 3.0 T. Diagnostic reference standard was established according to histopathology or imaging follow-up. The ADC = ADC (0, 800) and PDFF = fat / (water + fat) were calculated voxel-wise and examined for differences between benign and malignant lesions.ResultsThe ADC and PDFF values of malignant lesions were significantly lower compared to benign lesions (mean ADC 861 × 10−6 mm2/s vs. 1323 × 10−6 mm2/s, p < 0.001; mean PDFF 3.1% vs. 28.2%, p < 0.001). The areas under the curve (AUC) and diagnostic accuracies were 0.847 (p < 0.001) and 85.4% (cut-off at 1084.4 × 10−6 mm2/s) for ADC and 0.940 (p < 0.001) and 89.9% for PDFF (cut-off at 7.8%), respectively. The combined use of ADC and PDFF improved the diagnostic accuracy to 96.6% (malignancy if ADC ≤ 1118.2 × 10−6 mm2/s and PDFF ≤ 20.0%, otherwise benign).ConclusionQuantitative evaluation of both ADC and PDFF was useful in differentiating benign VBMLs from malignancy. The combination of ADC and PDFF improved the diagnostic performance and yielded high diagnostic accuracy for the differentiation of benign and malignant VBMLs.
Highlights
The spine is the most common site of osseous metastasis in the body
Utilizing simultaneous use of 1118.2 × 10–6 mm2/s apparent diffusion coefficient (ADC) cut-off and 20% proton density fat fraction (PDFF) cut-off resulted in correct diagnosis of the clinically uncertain vertebral bone marrow lesions (VBML). This prospective study evaluated the diagnostic performance of quantitative ADC and PDFF measurements to differentiate benign from malignant VBMLs
Owing to the excellent accuracy of the combined use of ADC and PDFF, our data strongly suggest that additional imaging studies and potentially harmful bone biopsies can often be avoided in patients with indeterminate VBMLs, with the potential advantage of improving overall patient health care and associated costs
Summary
The spine is the most common site of osseous metastasis in the body. In autopsy studies almost 40% of patients with metastatic solid primary tumors showed a spinal tumor manifestation, with an estimated 10% of cancer patients developing symptomatic bone metastases during the course of the disease [1]. Magnetic resonance imaging (MRI) plays a central role in the diagnostic work-up and preliminary etiologic characterization of VBMLs. Routinely used anatomic MRI sequences can provide a variety of signal intensity and morphologic patterns that may allow VBMLs to be distinguished from normal bone marrow with high diagnostic accuracy [3]; distinguishing between different entities of benign and malignant VBMLs can be more complex as the corresponding MRI signal characteristics may overlap, leading to misidentification of malignant VBMLs in 6–21% of cases [4]. Establishing a definitive diagnosis of VBMLs can become a diagnostic challenge, especially if there is no involvement of the paravertebral soft tissues in the early stages of malignant disease
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