Diffusion Tensor Imaging Investigation of Uncinate Fasciculus Anatomy in Healthy Controls: Description of a Subgenual Stem.

The uncinate fasciculus is the largest white matter association tract connecting the prefrontal cortex and the anteromedial temporal lobe. The traditional anatomical description outlines a temporal stem that hooks around the posterior insula, a subinsular body, and 2 prefrontal stems extending to the lateral orbital gyri and the frontopolar cortex. Recent imaging studies of the white matter tracts deep to the subgenual cingulate gyrus (Brodmann area 25: BA25) suggest the presence of white matter fibers extending from BA25 to the amygdala, via a route that would run in close proximity to the uncinate fasciculus, that are of functional importance in mood disorders. We hypothesized that these fibers represent a third, medial prefrontal stem of the uncinate fasciculus. Using diffusion tensor imaging in 74 healthy volunteer humans, we seeded the uncinate fasciculus using 2 regions of interest centered over the temporal stem and the caudal body of the uncinate fasciculus in the coronal plane at the level of the anterior commissure. A medial prefrontal stem extending to the subgenual cingulate gyrus was demonstrated in 65/74 left and 70/74 right cerebral hemispheres, and had a mean fractional anisotropy value of 0.43 (95% CI 0.40-0.47). The medial subgenual stem fibers were inseparable from the caudal body and temporal stem of the main uncinate fasciculus and followed the same hook-shaped morphology. A probable medial subgenual prefrontal stem of the uncinate fasciculus was demonstrated in a cohort of healthy volunteers and is of potential significance in our understanding of neuropsychiatry and mood disorders.

SPECT-CT/VQ versus CTPA for diagnosing pulmonary embolus and other lung pathology: Pre-existing lung disease should not be a contraindication.

INTRODUCTION: Single Photon Emission Computed Tomography-Ventilation-Perfusion (SPECT-VQ) with low-dose CT (SPECT-CT/VQ) has equivalent diagnostic accuracy to CTPA for diagnosing pulmonary embolus (PE) while using lower radiation doses, but is underutilized owing to perceived inaccuracy of scintigraphy in the setting of pre-existing lung disease. This study assesses the accuracy of SPECT-CT/VQ compared with CTPA for the diagnosis of PE, including in patients with pre-existing lung disease. METHODS: Retrospective non-inferiority cohort study of all patients who underwent SPECT-CT/VQ scanning at St Vincent's Hospital, NSW, from June 2012 to November 2013, who also had a CTPA within the same admission and <72 h apart (n = 102). RESULTS: SPECT-CT/VQ had 100% sensitivity and 94.4% specificity when compared with CTPA. Of the 102 patients, 14 were lung transplant patients, and 27 had other pre-existing lung disease (41/102, 40.2%), with SPECT-CT/VQ having a sensitivity of 100% and specificity of 97.2% in this patient group. Non-inferiority of SPECT-CT/VQ was demonstrated at a significance level of 0.005. CONCLUSION: SPECT-CT/VQ has high sensitivity and specificity for diagnosing PE compared with CTPA, even among patients with pre-existing lung disease, with lower radiation doses.