Faculty Bibliography

BACKGROUND AND PURPOSE/OBJECTIVE:Photon-counting CT (PCCT) offers several advantages over conventional CT for cochlear implant (CI) imaging, including improved spatial resolution, and both signal-to-noise and contrast-to-noise ratios. However, the optimal PCCT reconstruction parameters for CI imaging has not been established. This study compared six PCCT reconstruction approaches for temporal bone CI imaging in a multi-reader design. MATERIALS AND METHODS/METHODS:20 patients with CIs (24 implants) underwent temporal bone PCCT on a NAEOTOM Alpha scanner. Raw data was reconstructed using six different algorithms, as follows: Hr84 0.2mm T3D (head-regular, sharpness level 84, polyenergetic), Hr84 0.4mm T3D, Qr56 0.4mm iMAR T3D (quantitative-regular, sharpness level 56, iterative metal artifact reduction), Qr76 0.4mm M_140 (virtual monoenergetic 140 keV), Qr76 0.4mm M_70 (virtual monoenergetic 70 keV), and Qr76 0.4mm T3D.Two fellowship-trained neuroradiologists independently rated electrode visibility and overall image quality for all implants, and wire visibility for implants with visible wires, on 0-2 Likert scales. Inter-reader agreement was assessed with quadratic weighted Cohen's kappa. A mixed effects model was used to evaluate reconstruction differences for each metric. RESULTS:Mean patient age was 50.9 ± 26 years; 8 were women. Inter-reader agreement was substantial for electrode visibility (κ = 0.66) and overall image quality (κ = 0.79), and moderate for wire visibility (κ = 0.52). Reconstruction type significantly affected all three metrics. The sharp kernel reconstructions (Hr84 0.2mm T3D and Hr84 0.4mm T3D) consistently ranked highest, with significantly greater scores than most other reconstructions. Qr56 0.4mm iMAR T3D was the lowest rated in every category, significantly worse than all other reconstructions. CONCLUSIONS:PCCT reconstruction parameters substantially influence postoperative CI image quality. Ultra-high-resolution reconstructions provided the best combination of artifact suppression and fine structural detail, while iterative MAR and high-keV monoenergetic reconstructions performed the worst. These findings can guide reconstruction selection to optimize PCCT protocols for CI evaluation.

The ACR Incidental Findings Committee presents recommendations for managing incidental pineal cysts on CT of the head or MRI of the brain. The Pineal Cyst Subcommittee is composed of neuroradiologists and a neurosurgeon who developed the algorithms presented. These recommendations represent a combination of current published evidence as well as expert experience and opinion and were finalized by a formal consensus-building process. The recommendations address commonly encountered incidental findings in the pineal gland and are not intended to be a comprehensive review of all pineal incidental findings. The goal is to improve the quality of care by providing guidance on management of incidentally detected pineal cysts.

Photon-counting computed tomography (PCCT) is a new imaging technology that has advanced diagnostic imaging by offering improved spatial and contrast resolution as well as novel spectral imaging capabilities. Unlike conventional CT, which uses energy-integrating detectors, PCCT employs photon-counting detectors that directly measure individual photon energies, enabling applications such as virtual monochromatic imaging (VMI) and material decomposition. These innovations allow for artifact reduction, better visualization of fine anatomic structures, and improved diagnostic accuracy, all while reducing radiation dose. This review explores select applications of PCCT in neuroimaging, focusing on the brain, temporal bone, and spine. In the brain, we discuss how PCCT demonstrates superior performance for evaluating aneurysms, metallic prostheses, and vessel stenosis, offering enhanced visualization of vascular structures and minimizing artifacts. For temporal bone imaging, we review assessment of both complex anatomy and potentially subtle pathologies such as otosclerosis, as well as visualization of implants like cochlear devices and their intricate components. In spinal imaging, we explore how PCCT improves precise detection of causes of cerebrospinal fluid leaks, improves localization of tiny vessels such as the artery of Adamkiewicz and spinal dural arteriovenous fistulas, and reduces metal artifacts associated with postoperative hardware. PCCT addresses limitations of conventional CT while unlocking new diagnostic possibilities across neuroimaging applications. As clinical adoption of PCCT grows, ongoing research and development will refine imaging protocols and expand its utility. The accumulating evidence underscores PCCT's transformative potential to improve diagnostic confidence in neuroimaging and beyond.

Photon-counting CT (PCCT), approved for clinical practice for over two years now, both improves on features of conventional energy-integrating detector (EID) CT and introduces new capabilities such as multienergy acquisition. PCCT is already transforming all domains of radiology, including head and neck imaging, and will become increasingly utilized in the approaching years. In this review, we first concisely explain the key physical principles distinguishing PCCT from EID-CT. We then discuss how the underlying physics leads to the novel features associated with PCCT, focusing on improved artifact reduction, spatial resolution, contrast-to-noise ratio, as well as multienergy acquisition and reduced contrast and radiation doses. Next, we review head and neck PCCT applications and comparison to EID-CT in dental imaging, sinus imaging, temporal bone, tumor imaging, and vascular imaging. Within the temporal bone applications, we explore normal anatomy, pathologic anatomy, and the appearance of protheses and implants. Representative imaging is provided to highlight differences between PCCT and EID-CT. Finally, we highlight areas of ongoing research in PCCT.

OBJECTIVE:Observe if metal artifact reduction (MAR) techniques applied to magnetic resonance imaging (MRI) performed on patients with cochlear implants (CI) or auditory brainstem implants (ABI) improves image quality. STUDY DESIGN/METHODS:Retrospective review. SETTING/METHODS:Tertiary care center. PATIENTS/METHODS:Patients with auditory implants who underwent clinical MRI before and after the application of MAR techniques previously described. INTERVENTIONS/METHODS:From September 2022 to March 2023, patients who underwent brain or internal auditory canal (IAC) MRI with and without MAR were identified. Sequences included T1 and T2 weighted with turbo-spin-echo (TSE) correction and fluid-attenuation inversion recovery (FLAIR). Images were analyzed for visualization of intracranial structures by two neuroradiologists. MAIN OUTCOME MEASURES/METHODS:Visibility of 14 structures graded on a four-point Likert scale. Average scores per structure and sequence were compared using paired two-tailed t-tests and change in mode score. RESULTS:Ten patients underwent pre- and post-MAR MRI. Six had a unilateral CI, three had a unilateral ABI, and one had an ABI and CI. Three patients had four devices with the internal magnet removed for both scans. All structures had significantly improved visibility on post-MAR scan except ipsilateral parietal and occipital lobes and contralateral inner ear. Mode score increased from 2 to 4 for the ipsilateral occipital lobe and from 3 to 4 for the ipsilateral semicircular canals, brainstem, and cerebellar peduncles. Significant improvement was seen in all sequences except for ipsilateral structures on T1w axial precontrast and contralateral structures on T1w coronal postcontrast. ABIs did not improve as much as CIs because they scored better on the pre-MAR scan. CONCLUSIONS:MAR techniques improve image quality for patients with MRI-compatible implants with magnets. Benefits may be more evident in CIs than ABIs.

OBJECTIVE/UNASSIGNED:To better characterize the cochlear apex in relation to surgically relevant landmarks to guide surgeons and improve procedural success of apical electrode placement. STUDY DESIGN/UNASSIGNED:Retrospective image analysis. SETTING/UNASSIGNED:Tertiary referral center. PATIENTS/UNASSIGNED:Cochlear implant recipients with available preoperative computed tomography (CT) imaging. INTERVENTION/UNASSIGNED:None. MAIN OUTCOME MEASURE/UNASSIGNED:Cochlear dimensions and cochlear apex distance measures to surgically relevant middle ear landmarks and critical structures. RESULTS/UNASSIGNED:Eighty-two temporal bone CT scans were analyzed utilizing multiplanar reformats. The average lateral width of promontory bone over the cochlear apex was 1.2 mm (standard deviation [SD], 0.3). The anteroposterior distance from the round window (avg, 4.2 mm; SD, 0.5), oval window (avg, 3.3 mm; SD, 0.3), cochleariform process (avg, 2.3; SD, 0.5), and superior-inferior distance from the cochleariform process (avg, -0.9; SD, 0.8) to the cochlear apex were measured. The relationship of the cochlear apex to critical structures was highly variable.A newly developed stapes vector was created and found to mark the posterior/superior boundary of the apex in 94% of patients. When a vector parallel to the stapes vector was drawn through the round window, it marked the anterior/inferior boundary of the cochlear apex in 89% of patients. CONCLUSIONS/UNASSIGNED:This study assists in characterizing cochlear apex anatomy and its relation to surrounding structures as a means of improving procedural accuracy and reducing trauma during apical cochleostomy. Understanding both distance relationships and expected boundaries of the apex could help to inform future surgical approaches.

OBJECTIVE:Imaging is crucial in the assessment of head and neck cancers for site, extension, and enlarged lymph nodes. Restriction spectrum imaging (RSI) is a new diffusion-weighted magnetic resonance imaging (MRI) technique that enhances the ability to differentiate aggressive cancer from low-grade or benign tumors and helps guide treatment and biopsy. Its contribution to imaging of brain and prostate tumors has been previously published. However, there are no prior studies using RSI sequence in head and neck tumors. The purpose of this study was to evaluate the feasibility of performing RSI in head and neck cancer. METHODS:An additional RSI sequence was added in the routine MRI neck protocol for 13 patients diagnosed with head and neck cancer between November 2018 and April 2019. Restriction spectrum imaging sequence was performed with b values of 0, 500, 1500, and 3000 s/mm 2 and 29 directions on 1.5T magnetic resonance scanners.Diffusion-weighted imaging (DWI) images and RSI images were compared according to their ability to detect the primary malignancy and possible metastatic lymph nodes. RESULTS:In 71% of the patients, RSI outperformed DWI in detecting the primary malignancy and possible metastatic lymph nodes, whereas in the remaining cases, the 2 were comparable. In 66% of the patients, RSI detected malignant lymph nodes that DWI/apparent diffusion coefficient failed to detect. CONCLUSIONS:This is the first study of RSI in head and neck imaging and showed its superiority over the conventional DWI sequence. Because of its ability to differentiate benign and malignant lymph nodes in some cases, the addition of RSI to routine head and neck MRI should be considered.

Brown syndrome is the inability to gaze upward beyond the horizontal level while adducting the eye due to an abnormality of the superior oblique tendon sheath complex. It is a rare extraocular muscular disorder, and its imaging is infrequently seen in radiologic practice. This article presents clinical characteristics and imaging of 5 patients with Brown syndrome and reviews the radiologic literature available, to familiarize the readers with its imaging findings.