Dual-energy CT in sacral fragility fractures: defining a cut-off Hounsfield unit value for the presence of traumatic bone marrow edema in patients with osteoporosis.

BACKGROUND: Demographic change entails an increasing incidence of fragility fractures. Dual-energy CT (DECT) with virtual non-calcium (VNCa) reconstructions has been introduced as a promising diagnostic method for evaluating bone microarchitecture and marrow simultaneously. This study aims to define the most accurate cut-off value in Hounsfield units (HU) for discriminating the presence and absence of bone marrow edema (BME) in sacral fragility fractures. METHODS: Forty-six patients (40 women, 6 men; 79.7 ± 9.2 years) with suspected fragility fractures of the sacrum underwent both DECT (90 kVp / 150 kVp with tin prefiltration) and MRI. Nine regions-of-interest were placed in each sacrum on DECT-VNCa images. The resulting 414 HU measurements were stratified into "edema" (n = 80) and "no edema" groups (n = 334) based on reference BME detection in T2-weighted MRI sequences. Area under the receiver operating characteristic curve was calculated to determine the desired cut-off value and an associated conspicuity range for edema detection. RESULTS: The mean density within the "edema" group of measurements (+ 3.1 ± 8.3 HU) was substantially higher compared to the "no edema" group (-51.7 ± 21.8 HU; p < 0.010). Analysis in DECT-VNCa images suggested a cut-off value of -12.9 HU that enabled sensitivity and specificity of 100% for BME detection compared to MRI. A range of HU values between -14.0 and + 20.0 is considered indicative of BME in the sacrum. CONCLUSIONS: Quantitative analysis of DECT-VNCa with a cut-off of -12.9 HU allows for excellent diagnostic accuracy in the assessment of sacral fragility fractures with associated BME. A diagnostic "one-stop-shop" approach without additional MRI is feasible.

Dual-energy CT as an innovative method for diagnosing fragility fractures of the pelvic ring: a retrospective comparison with MRI as the gold standard.

INTRODUCTION: As the average age of society increases, so does the number of cases of fragility fractures of the pelvis (FFP). Magnetic resonance imaging (MRI) can visualise associated oedema and is thus the gold standard for diagnosing such fractures. MRI, however, is costly, not always available, and involves certain exclusion criteria. Dual-energy computed tomography (DECT) appears to be a promising alternative. It is unclear, however, whether it could be used for diagnosing FFP with similar sensitivity/specificity. The aim of our study was thus to compare conventional CT and DECT with MRI in cases of suspected FFP. MATERIALS AND METHODS: A total of 46 patients with suspected FFP underwent MRI, CT and DECT scans. There were three comparison groups for each of these patients: conventional CT image analysis without dual-energy modification (Arm 1), DECT analysis (Arm 2) and MRI as the gold standard (Arm 3). Diagnosis and FFP classification were performed by a radiologist in random order and without clinical information. The sensitivity and specificity of conventional CT and DECT were calculated in comparison with MRI as the reference standard. RESULTS: With 100% sensitivity and specificity, DECT is on par with MRI when it comes to diagnosing fragility fractures of the pelvis and is superior to conventional CT (90.3% sensitivity, 100% specificity). In terms of classification as well, there were no differences between DECT and MRI. On conventional CT, on the other hand, 16 patients were classified differently than they were on MRI. CONCLUSIONS: Our study shows DECT to be reliable and superior to conventional CT in terms of oedema detection and specific fracture classification in FFP. DECT thus combines the advantages of conventional CT (good visualisation of bone matter) and MRI (medullary cavity and visualisation of occult fractures).