Farnsworth, Paul

Aberrant internal carotid artery (ICA) is a vascular anomaly in which a segment of the ICA courses through the middle ear. The association of aberrant ICAs and pseudoaneurysm formation is not well known and can be an important finding to recognize on imaging. In this series, we present three cases of aberrant ICAs having asymmetric contour deformities consistent with pseudoaneurysms diagnosed utilizing CT of the temporal bone.

AbstractBackgroundCochlear implants (CIs) are used to rehabilitate moderate to profound sensorineural hearing loss and stimulate the auditory system via a multichannel electrode array positioned in the scala tympani. Imaging evaluation of CIs is substantially degraded by metallic artifacts. Photon‐counting detector (PCD)‐CT has the potential to minimize such artifacts, though this has not been convincingly established in prior studies. This study compared the visualization of CI electrodes on PCD‐CT to conventional energy integrating detector (EID)‐CT.Materials and MethodsFive patients with CIs were prospectively recruited to undergo temporal bone imaging on both EID‐CT and PCD‐CT scanners yielding 2D and 3D Volume Rendering Technique (VRT) images. Three nonblinded neuroradiologists reviewed 2D and 3D VRT images for the ability to resolve CI electrode leads using a Likert scale. The average Likert scores of PCD‐CT versus EID‐CT were calculated for each reader for both 2D and 3D VRT images. (Likert scores 1–5 based on inferior to superior rating of PCD‐CT compared to EID‐CT). Inter‐rater agreement was assessed using Krippendorff's alpha with ordinal weights. ResultsFive patients underwent temporal bone CT for CI array evaluation. As evidenced by 5‐point Likert scales that were independently used by the three reviewers, this study demonstrated superior resolution of CI electrode array using PCD‐CT as compared to EID‐CT with an average score of 4.2 ± 0.8 for 2D images and 4.9 ± 0.4 for 3D VRT images.ConclusionsPCD‐CT is superior to EID‐CT in the visualization of CI electrodes, particularly in 3D VRT imaging.

AbstractBackground and PurposeTo compare the performance of the photon‐counting detector (PCD)‐CT against a cutting‐edge energy‐integrated detector (EID)‐CT to visualize different segments of the chorda tympani nerve.Materials and MethodsAn IRB‐approved protocol prospectively enrolled patients for temporal bone CT on both EID‐CT and PCD‐CT scanners. Fellowship‐trained neuroradiologists compared visualization of chorda tympani segments on each scanner using a 5‐point Likert scale (1 indicating EID is far superior to PCD, 3 indicating they are equivalent, and 5 indicating PCD is far superior to EID). Scores were averaged across segments and tested using a one‐sample Wilcoxon signed‐rank test with a one‐sided alternative hypothesis.ResultsForty temporal bones were evaluated. Average Likert scores for visualization of chorda tympani segments‐chorda tympani canal/proximal segment, middle ear/posterior tympanic segment, and petrotympanic fissure/distal segment‐ on the PCD compared to EID scanner were 4.2 (SD = 0.4), 4.4 (0.5), and 4 (0.0), respectively. The anterior tympanic segment of the chorda tympani was not well visualized on either platform or therefore not scored. PCD compared to the EID scanner had better overall performance (Median = 4.2, 95% CI: [4.1, 5.0], p‐value < .001).ConclusionPCD‐CT improves visualization of the petrous and intratympanic chorda tympani nerve segments, chorda tympani canaliculus, and petrotympanic fissure compared to comparable EID‐CT examinations. The improved visualization of the chorda tympani is important for the characterization of middle ear pathology involving this structure and presurgical planning to determine the size of the facial recess for cochlear implantation and to estimate the risk of nerve injury.

Background and Purpose Recent introduction of photon counting detector (PCD) computed tomography (CT) scanners into clinical practice further improve CT angiography (CTA) depiction of orbital arterial vasculature compared to conventional energy integrating detector (EID) CT scanners. PCD-CTA of the orbit can provide a detailed arterial roadmap of the orbit which can de diagnostic on its own or serve as a helpful planning adjunct for both diagnostic and therapeutic catheter-based angiography of the orbit. Methods For this review, EID and PCD-CT imaging was obtained in 28 volunteers. The volume CT dose index was closely matched. A dual-energy scanning protocol was used on EID-CT. An ultra-high-resolution (UHR) scan mode was used on PCD-CT. Images were reconstructed at 0.6 mm slice thickness using a closely matched medium-sharp standard resolution (SR) kernel. High-resolution (HR) images with the sharpest quantitative kernel were also reconstructed on PCD-CT at the thinnest slice thickness of 0.2 mm. A denoising algorithm was applied to the HR image series. Results The imaging description of the orbital vascular anatomy presented in this work was derived from these patients’ PCD-CTA images in combination with review of the literature. We found that orbital arterial anatomy is much better depicted with PCD-CTA, and this work can serve primarily as an imaging atlas of the normal orbital vascular anatomy. Conclusion With recent advances in technology, arterial anatomy of the orbit is much better depicted with PCD-CTA as opposed to EID-CTA. Current orbital PCD-CTA technology approaches the necessary resolution threshold for reliable evaluation of central retinal artery occlusion.

Abstract Background and Purpose Artifact from cochlear implant electrodes degrades image resolution on CT. Here, we describe the use of coregistered pre‐ and postoperative CT images to reduce metallic artifact from the electrodes to assess its position more accurately within the cochlear lumen. Methods Pre‐ and postoperative CTs were reviewed after coregistration/overlay of both exams. Images were evaluated by two neuroradiologists for scalar location of electrodes tip (± scalar translocation), tip fold over, and angular depth of insertion. Results Thirty‐four patients were included in the final cohort. Transscalar migration was present in three (8.8%) cases (one case demonstrated tip fold over), with initial disagreement regarding transscalar migration in 1 out of 34 patients (2.9%). Agreement regarding depth of insertion was present in 31 (91.1%) cases. Five‐point Likert scales were used to compare the ability to resolve the proximity of electrodes to the lateral/outer cochlear wall without and with overlay, which is a qualitative measure of artifact from the array. Likert scores showed definitive benefit of metal artifact reduction using overlayed images with an average score of 4.34. Conclusion This study demonstrates a novel technique of using fused coregistration of pre‐ and postoperative CTs for the purpose of artifact reduction/electrode localization. It is anticipated that this technique will permit more accurate localization of the electrodes for improvement in surgical technique and electrode array design.