Abstract
Objectives To assess whether bone marrow edema in patients with acute vertebral fractures can be accurately diagnosed based on three-material decomposition with dual-layer spectral CT (DLCT).
Materials and methods Acute (n = 41) and chronic (n = 18) osteoporotic thoracolumbar vertebral fractures as diagnosed by MRI (hyperintense signal in STIR sequences) in 27 subjects (72 ± 11 years; 17 women) were assessed with DLCT. Spectral data were decomposed into hydroxyapatite, edema-equivalent, and fat-equivalent density maps using an in-house-developed algorithm. Two radiologists, blinded to clinical and MR findings, assessed DLCT and conventional CT independently, using a Likert scale (1 = no edema; 2 = likely no edema; 3 = likely edema; 4 = edema). For DLCT and conventional CT, accuracy, sensitivity, and specificity for identifying acute fractures (Likert scale, 3 and 4) were analyzed separately using MRI as standard of reference.
Results For the identification of acute fractures, conventional CT showed a sensitivity of 0.73–0.76 and specificity of 0.78–0.83, whereas the sensitivity (0.93–0.95) and specificity (0.89) of decomposed DLCT images were substantially higher. Accuracy increased from 0.76 for conventional CT to 0.92–0.93 using DLCT. Interreader agreement for fracture assessment was high in conventional CT (weighted κ [95% confidence interval]; 0.81 [0.70; 0.92]) and DLCT (0.96 [0.92; 1.00]).
Conclusions Material decomposition of DLCT data substantially improved accuracy for the diagnosis of acute vertebral fractures, with a high interreader agreement. This may spare patients additional examinations and facilitate the diagnosis of vertebral fractures.
Introduction
Vertebral compression fractures are a common pathology found in patients with reduced bone mineral density (BMD) caused by osteoporosis [1], but also in otherwise healthy patients after adequate trauma. With a prevalence of up to 26% in women and 24% in men older than 49 years [1], vertebral fractures are associated with an age-adjusted 32% increased risk of mortality [2]. Adequate management of fractures not only depends on accurate morphologic assessment, including the evaluation of the stability of the affected spinal units, but also on accurate assessment of fracture age. Although several CT-based classification criteria for spine injuries exist [3], CT in clinical routine lacks accuracy regarding the determination of the age of vertebral fractures. Therefore, MR imaging is often performed to identify edema-equivalent bone marrow changes, which are considered highly specific for acute trauma [4–6]. However, MR imaging is associated with additional examination times and substantial costs, and some patients are not eligible due to contra-indications such as pacemakers, other implants, or severe pain.
Discussion
In our study, the detection of bone marrow edema, and thus the identification of patients with acute thoracolumbar vertebral fractures, was feasible using three-material decomposition and material-specific density maps calculated from duallayer spectral CT. The accuracy, sensitivity, and specificity for the diagnosis of acute vertebral fractures was substantially higher with three-material decomposition generated from dual-layer spectral CT images compared to the conventional CT images, using MR imaging as standard of reference.
