[18F]FDG PET accurately differentiates infected and non-infected non-unions after fracture fixation.

PURPOSE: Complete fracture healing is crucial for good patient outcomes. A major complication in the treatment of fractures is non-union. The pathogenesis of non-unions is not always clear, although implant-associated infections play a significant role, especially after surgical treatment of open fractures. We aimed to evaluate the value of [18F]FDG PET in suspected infections of non-union fractures. METHODS: We retrospectively evaluated 35 consecutive patients seen between 2000 and 2015 with suspected infection of non-union fractures, treated at a level I trauma center. The patients underwent either [18F]FDG PET/CT (N = 24), [18F]FDG PET (N = 11) plus additional CT (N = 8), or conventional X-ray (N = 3). Imaging findings were correlated with final diagnosis based on intraoperative culture or follow-up. RESULTS: In 13 of 35 patients (37 %), infection was proven by either positive intraoperative tissue culture (N = 12) or positive follow-up (N = 1). [18F]FDG PET revealed 11 true-positive, 19 true-negative, three false-positive, and two false-negative results, indicating sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of 85 %, 86 %, 79 %, 90 %, and 86 %, respectively. The SUVmax was 6.4 ± 2.7 in the clinically infected group and 3.0 ± 1.7 in the clinically non-infected group (p <0.01). The SUVratio was 5.3 ± 3.3 in the clinically infected group and 2.6 ± 1.5 in the clinically non-infected group (p <0.01). CONCLUSION: [18F]FDG PET differentiates infected from non-infected non-unions with high accuracy in patients with suspected infections of non-union fractures, for whom other clinical findings were inconclusive for a local infection. [18F]FDG PET should be considered for therapeutic management of non-unions.

Functional imaging with laser speckle contrast analysis: vascular compartment analysis and correlation with laser Doppler flowmetry and somatosensory evoked potentials.

Laser Speckle Contrast Analysis (LASCA), a novel, high-resolution blood flow imaging method, was performed on rat somatosensory cortex during functional activation. In the same animals, cerebral blood flow (CBF) was measured with Laser Doppler Flowmetry. To obtain a quantitative estimate of the underlying neuronal activity, somatosensory evoked potentials were recorded simultaneously with an epidural EEG. Our results show that: 1. CBF changes measured by LASCA or LDF are nonlinearly dependent on the magnitude of electrical neural activity revealed by somatosensory evoked potentials. 2. The magnitude of relative CBF changes measured by LASCA and LDF shows a strong correlation. 3. LASCA imaging localizes the highest relative changes of CBF in microcirculatory areas, with a smaller contribution by larger vessels. This study demonstrates that LASCA is a reliable method that provides 2D-imaging of CBF changes that are comparable to LDF measurements. It further suggests that functional neuroimaging methods based on CBF enhance areas of microcirculation and thus might prove more accurate in localizing neural activity than oxygenation related methods like BOLD-fMRI.