Virtual monoenergetic images by spectral detector computed tomography may improve image quality and diagnostic ability for ischemic lesions in acute ischemic stroke.

BACKGROUND: Acute ischemic lesions are challenging to detect by conventional computed tomography (CT). Virtual monoenergetic images may improve detection rates by increased tissue contrast. PURPOSE: To compare the ability to detect ischemic lesions of virtual monoenergetic with conventional images in patients with acute stroke. MATERIAL AND METHODS: We included consecutive patients at our center that underwent brain CT in a spectral scanner for suspicion of acute stroke, onset <12 h, with or without (negative controls) a confirmed cortical ischemic lesion in the initial scan or a follow-up CT or magnetic resonance imaging. Attenuation was measured in predefined areas in ischemic gray (guided by follow-up exams), normal gray, and white matter in conventional images and retrieved in spectral diagrams for the same locations in monoenergetic series at 40-200 keV. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Visual assessment of diagnostic measures was performed by independent review by two neuroradiologists blinded to reconstruction details. RESULTS: In total, 29 patients were included (January 2018 to July 2019). SNR was higher in virtual monoenergetic compared to conventional images, significantly at 60-150 keV. CNR between ischemic gray and normal white matter was higher in monoenergetic images at 40-70 keV compared to conventional images. Virtual monoenergetic images received higher scores in overall image quality. The sensitivity for diagnosing acute ischemia was 93% and 97%, respectively, for the reviewers, compared to 55% of the original report based on conventional images. CONCLUSION: Virtual monoenergetic reconstructions of spectral CIs may improve image quality and diagnostic ability in stroke assessment.

Minimal guidewire length for central venous catheterization of the right subclavian vein: A CT-based consecutive case series.

BACKGROUND: Central venous catheter (CVC) misplacement occurs frequently after right subclavian vein catheterization. It can be avoided by using ultrasound to confirm correct guidewire tip position in the lower superior vena cava prior to CVC insertion. However, retraction of the guidewire during the CVC insertion may dislocate the guidewire tip from its desired and confirmed position, thereby resulting in CVC misplacement. The aim of this study was to determine the minimal guidewire length required to maintain correct guidewire tip position in the lower superior vena cava throughout an ultrasound-guided CVC placement in the right subclavian vein. METHODS: One hundred adult patients with a computed tomography scan of the chest were included. By using multiplanar reconstructions from thin-sliced images, the distance from the most plausible distal puncture site of the right subclavian vein to the optimal guidewire tip position in the lower superior vena cava was measured (vessel length). In addition, measurements of equipment in common commercial over-the-wire percutaneous 15-16 cm CVC kits were performed. The 95th percentile of the vessel length was used to calculate the required minimal guidewire length for each CVC kit. RESULTS: The 95th percentile of the vessel length was 153 mm. When compared to the calculated minimal guidewire length, the guidewires were up to 108 mm too short in eight of eleven CVC kits. CONCLUSION: After confirmation of a correct guidewire position, retraction of the guidewire tip above the junction of the brachiocephalic veins should be avoided prior to CVC insertion in order to preclude dislocation of the catheter tip towards the right internal jugular vein or the left subclavian vein. This study shows that many commercial over-the-wire percutaneous 15-16 cm CVC kits contain guidewires that are too short for right subclavian vein catheterization, i.e., guidewire retraction is needed prior to CVC insertion.