INTERRELATION BETWEEN PREOPERATIVE TESTS, INTRAOPERATIVE FINDINGS AND OUTCOMES OF 99M-TECHNETIUM-SESTAMIBI SCAN IN PRIMARY HYPERPARATHYROIDISM

Context

Primary hyperparathyroidism is one of the most common endocrinological disorder and surgery of parathyroid glands is the main therapy of this disease. Minimally invasive surgery is getting more prominent in these days and its success in parathyroid surgery mostly depends on accuracy of the localization studies.

Objective

The aim of this study is to understand the relationship between preoperative biochemical tests, intraoperative findings and Technetium-99m-methoxyisobutylisonitrile (MIBI) scan results.

Design

Retrospective clinical study.

Subjects and Methods

A total of 185 patients, who have been diagnosed with primary hyperparathyroidism (PHPT) and operated between January, 2010 and October, 2018, were included to the study. Patients with less than 6 months of follow up are excluded from the study.

Results

Patients were divided into two groups according to their scintigraphy results; with positive scintigraphy findings as group 1 (n:135) and negative scintigraphy findings as group 2 (n:50). Mean preoperative serum parathyroid hormone (PTH) values were significantly different between the two groups (p<0.02). Mean preoperative serum calcium, creatinine, magnesium, phosphorus, alkaline phosphatase, 25-OH Vitamin D3 levels of both groups were analyzed and there were no statistical differences between the two groups considering these parameters. Also, mean diameter and mean volume of parathyroid adenomas were significantly higher in group 1 (2.1±1.0 cm vs. 1.55±0.72 cm, respectively, p<0.0001; 2.66±5.35 cm3 vs. 1±1.9 cm3, respectively, p<0.0001). Optimal cut-off values of parathyroid adenoma diameter for MIBI scan positivity were 1.55 cm, parathyroid volume for MIBI scan positivity were 0.48 cm3, preoperative serum PTH for MIBI scan positivity were 124.5 ng/L.

Conclusions

Preoperative serum PTH levels, diameter and volume of adenomas might be helpful for the prediction of MIBI scan accuracy and possible need of another localization studies.

Feasibility of clinical evaluation of individuals with increased risk for HPV-associated oropharynx cancer

BACKGROUND

Human papillomavirus-associated oropharynx squamous cell carcinoma (HPV-OPSCC) has no known pre-malignant lesion. While vaccination offers future primary prevention, there is current interest in secondary prevention. The feasibility of clinical evaluation of individuals at increased risk for HPV-OPSCC is unclear.

METHODS

Individuals with risk factors for HPV-OPSCC were enrolled in a prospective study (MOUTH). Participants positive for biomarkers associated with HPV-OPSCC were eligible for a clinical evaluation which comprised a head and neck examination and imaging with ultrasound and/or magnetic resonance imaging (MRI). This study was designed to evaluate feasibility of clinical evaluation in a screening study.

RESULTS

Three hundred and eighty-four participants were eligible for clinical evaluation. Of the 384, 204 (53%) completed a head and neck examination or imaging. Of these, 66 (32%) completed MRI (n = 51) and/or ultrasound (n = 64) studies.

CONCLUSIONS

Clinical evaluations, including head and neck examination and imaging, are feasible in the context of a screening study for HPV-OPSCC.

Multi-perspective region-based CNNs for vertebrae labeling in intraoperative long-length images

PURPOSE

Effective aggregation of intraoperative x-ray images that capture the patient anatomy from multiple view-angles has the potential to enable and improve automated image analysis that can be readily performed during surgery. We present multi-perspective region-based neural networks that leverage knowledge of the imaging geometry for automatic vertebrae labeling in Long-Film images - a novel tomographic imaging modality with an extended field-of-view for spine imaging.

METHOD

A multi-perspective network architecture was designed to exploit small view-angle disparities produced by a multi-slot collimator and consolidate information from overlapping image regions. A second network incorporates large view-angle disparities to jointly perform labeling on images from multiple views (viz., AP and lateral). A recurrent module incorporates contextual information and enforce anatomical order for the detected vertebrae. The three modules are combined to form the multi-view multi-slot (MVMS) network for labeling vertebrae using images from all available perspectives. The network was trained on images synthesized from 297 CT images and tested on 50 AP and 50 lateral Long-Film images acquired from 13 cadaveric specimens. Labeling performance of the multi-perspective networks was evaluated with respect to the number of vertebrae appearances and presence of surgical instrumentation.

RESULTS

The MVMS network achieved an F1 score of >96% and an average vertebral localization error of 3.3 mm, with 88.3% labeling accuracy on both AP and lateral images - (15.5% and 35.0% higher than conventional Faster R-CNN on AP and lateral views, respectively). Aggregation of multiple appearances of the same vertebra using the multi-slot network significantly improved the labeling accuracy (p < 0.05). Using the multi-view network, labeling accuracy on the more challenging lateral views was improved to the same level as that of the AP views. The approach demonstrated robustness to the presence of surgical instrumentation, commonly encountered in intraoperative images, and achieved comparable performance in images with and without instrumentation (88.9% vs. 91.2% labeling accuracy).

CONCLUSION

The MVMS network demonstrated effective multi-perspective aggregation, providing means for accurate, automated vertebrae labeling during spine surgery. The algorithms may be generalized to other imaging tasks and modalities that involve multiple views with view-angle disparities (e.g., bi-plane radiography). Predicted labels can help avoid adverse events during surgery (e.g., wrong-level surgery), establish correspondence with labels in preoperative modalities to facilitate image registration, and enable automated measurement of spinal alignment metrics for intraoperative assessment of spinal curvature.

High resolution 3D magnetic resonance imaging of Gruber's ligament: a pilot study

INTRODUCTION

Gruber's ligament (GL), a surgical landmark, extends from the lateral upper clivus to the petrous apex (PA), forming the superior boundary of Dorello's canal (DC). It overlies the interdural segment of the abducens nerve (CN VI). High-resolution 3D skull base MRI (SB-MRI) demonstrates anatomic details visible to the surgeon, but not well seen on traditional cross-sectional imaging. The aim of this study was to demonstrate visualization of the GL and its relationship to CN VI utilizing contrast enhanced high-resolution SB-MRI.

METHODS

Two neuroradiologists retrospectively reviewed in consensus the SB-MRIs of 27 skull base sides, among 14 patients. GL detection rate, confidence of detection, and GL length were recorded. When GL was successfully identified, the position of the interdural segment of CN VI within DC was recorded.

RESULTS

GL was readily identified in 16 skull base sides (59%), identified with some difficulty in 2 skull base sides (7%), and failed to be identified in 9 skull base sides (33%). The mean GL length was 7.1 mm (4.5-9.3 mm). Among the 18 cases where GL was successfully identified, CN VI was readily identified in all cases (100%), coursing the lateral third of DC in 72% of sides, and middle third in the remaining 28% of sides.

CONCLUSION

GL can be identified in approximately two-thirds of cases utilizing 3D high resolution SB-MRI. CN VI passes most commonly along the lateral third of DC. This is the first report demonstrating visualization of GL and its relation to CN VI, on imaging.

The effect of strap muscle transection on voice and swallowing changes after thyroidectomy in patients without laryngeal nerve injury

INTRODUCTION

Voice and swallowing symptoms are frequently reported after thyroidectomy even without laryngeal nerve injury. We aimed to evaluate the effect of strap muscle transection on voice and swallowing outcome after thyroidectomy.

METHODS

Group 1 (G1) consisted of 17 patients who had their strap muscles transected during thyroidectomy and group 2 (G2) consisted of 17 patients who had their strap muscles preserved during thyroidectomy. None of the patients had laryngeal nerve injury. Voice impairment scores (VIS) and swallowing impairment scores (SIS) were obtained preoperatively and at 1 week and 1, 3 and 6 months postoperatively. Pre- and postoperative vocal cord examinations were performed for all patients. The external branch of the superior laryngeal nerve (EBSLN) was evaluated by intraoperative cricothyroid muscle electromyography.

RESULTS

There was no significant difference in VIS and SIS between the two groups. At postoperative week 1, the VIS and SIS for each group were above preoperative values (G1: p = 0.005 and p = 0.035; G2: p = 0.031, p = 0.346, for VIS and SIS respectively). The VIS and SIS scores at 6 months postoperatively were significantly lower than those of the first week postoperatively (G1: p = 0.04 and p = 0.001; G2: p = 0.022 and p = 0.034 respectively) and similar to preoperative values (G1: p = 0.924 and p = 0.086; G2: p = 0.822 and p = 0.187 respectively).

CONCLUSION

Although voice and swallowing complaints increased in the early postoperative period even without recurrent laryngeal nerve and EBSLN injuries, these symptoms are not related with the strap muscle transection.

Model-based pulse pileup and charge sharing compensation for photon counting detectors: A simulation study

Purpose

We aim at developing a model‐based algorithm that compensates for the effect of both pulse pileup (PP) and charge sharing (CS) and evaluates the performance using computer simulations.

Methods

The proposed PCP algorithm for PP and CS compensation uses cascaded models for CS and PP we previously developed, maximizes Poisson log‐likelihood, and uses an efficient three‐step exhaustive search. For comparison, we also developed an LCP algorithm that combines models for a loss of counts (LCs) and CS. Two types of computer simulations, slab‐ and computed tomography (CT)‐based, were performed to assess the performance of both PCP and LCP with 200 and 800 mA, (300 µm)² × 1.6‐mm cadmium telluride detector, and a dead‐time of 23 ns. A slab‐based assessment used a pair of adipose and iodine with different thicknesses, attenuated X‐rays, and assessed the bias and noise of the outputs from one detector pixel; a CT‐based assessment simulated a chest/cardiac scan and a head‐and‐neck scan using 3D phantom and noisy cone‐beam projections.

Results

With the slab simulation, the PCP had little or no biases when the expected counts were sufficiently large, even though a probability of count loss (PCL) due to dead‐time loss or PP was as high as 0.8. In contrast, the LCP had significant biases (>±2 cm of adipose) when the PCL was higher than 0.15. Biases were present with both PCP and LCP when the expected counts were less than 10–120 per datum, which was attributed to the fact that the maximum likelihood did not approach the asymptote. The noise of PCP was within 8% from the Cramér–Rao lower bounds for most cases when no significant bias was present. The two CT studies essentially agreed with the slab simulation study. PCP had little or no biases in the estimated basis line integrals, reconstructed basis density maps, and synthesized monoenergetic CT images. But the LCP had significant biases in basis line integrals when X‐ray beams passed through lungs and near the body and neck contours, where the PCLs were above 0.15. As a consequence, basis density maps and monoenergetic CT images obtained by LCP had biases throughout the imaged space.

Conclusion

We have developed the PCP algorithm that uses the PP–CS model. When the expected counts are more than 10–120 per datum, the PCP algorithm is statistically efficient and successfully compensates for the effect of the spectral distortion due to both PP and CS providing little or no biases in basis line integrals, basis density maps, and monoenergetic CT images regardless of count‐rates. In contrast, the LCP algorithm, which models an LC due to pileup, produces severe biases when incident count‐rates are high and the PCL is 0.15 or higher.

Predictors of survival and time to progression following operative management of intramedullary spinal cord astrocytomas

PURPOSE

Surgical resection is considered standard of care for primary intramedullary astrocytomas, but the infiltrative nature of these lesions often precludes complete resection without causing new post-operative neurologic deficits. Radiotherapy and chemotherapy serve as potential adjuvants, but high-quality data evaluating their efficacy are limited. Here we analyze the experience at a single comprehensive cancer center to identify independent predictors of postoperative overall and progression-free survival.

METHODS

Data was collected on patient demographics, tumor characteristics, pre-operative presentation, resection extent, long-term survival, and tumor progression/recurrence. Kaplan-Meier curves modeled overall and progression-free survival. Univariable and multivariable accelerated failure time regressions were used to compute time ratios (TR) to determine predictors of survival.

RESULTS

94 patients were included, of which 58 (62%) were alive at last follow-up. On multivariable analysis, older age (TR = 0.98; p = 0.03), higher tumor grade (TR = 0.12; p < 0.01), preoperative back pain (TR = 0.45; p < 0.01), biopsy [vs GTR] (TR = 0.18; p = 0.02), and chemotherapy (TR = 0.34; p = 0.02) were significantly associated with poorer survival. Higher tumor grade (TR = 0.34; p = 0.02) and preoperative bowel dysfunction (TR = 0.31; p = 0.02) were significant predictors of shorter time to detection of tumor growth.

CONCLUSION

Tumor grade and chemotherapy were associated with poorer survival and progression-free survival. Chemotherapy regimens were highly heterogeneous, and randomized trials are needed to determine if any optimal regimens exist. Additionally, GTR was associated with improved survival, and patients should be counseled about the benefits and risks of resection extent.

Predictive Factors for Concurrent Tegmen Dehiscence in Superior Canal Dehiscence Syndrome

OBJECTIVES

To describe factors predictive of tegmen dehiscence in subjects with superior semicircular canal dehiscence syndrome (SCDS).

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary referral center.

PATIENTS

Subjects with SCDS who underwent middle fossa craniotomy (MFC) for plugging/resurfacing.

MAIN OUTCOME MEASURES

Operative and radiographic findings of tegmen dehiscences, preoperative low frequency air-bone gaps (LF-ABGs), ocular vestibular evoked myogenic potential (oVEMP) amplitudes, size of superior semicircular canal dehiscence (SCD), and history of obesity or obstructive sleep apnea (OSA).

RESULTS

One hundred thirty six patients (avg. age, 50.6 yr, 55.1% female) underwent MFC for repair of SCDS. Tegmen dehiscences were commonly found intraoperatively (tegmen tympani dehiscence [TTD] in 19.9% [11% with dural contact of ossicles], tegmen mastoideum dehiscence [TMD] in 28.7%). There were no differences in preoperative LF-ABGs and preoperative oVEMP amplitudes with respect to tegmen status. The sensitivity and specificity of computed tomography (CT) for predicting an intraoperatively confirmed TTD was 85 and 74%, respectively, and 44 and 79% for TMD. History of obesity and OSA did not differ between those with and without tegmen dehiscences. The presence of contralateral SCD and increasing cross-sectional area of SCD were both significantly associated with concurrent tegmen defects.

CONCLUSIONS

Obesity, OSA, preoperative oVEMP, and LF-ABG do not differ between those with SCD alone and those with SCD and concurrent tegmen dehiscences. Likewise, CT scans have relatively low sensitivity for identifying tegmen dehiscences. The presence of concurrent tegmen defects is more common in subjects with larger SCD cross-sectional areas and contralateral SCD.

Utility of 18F-fluorodeoxyglucose positron emission tomography in presurgical evaluation of patients with epilepsy: A multicenter study

OBJECTIVE

18F-Fluorodeoxyglucose positron emission tomography (FDG-PET) is widely used in presurgical assessment in patients with drug-resistant focal epilepsy (DRE) if magnetic resonance imaging (MRI) and scalp electroencephalography (EEG) do not localize the seizure onset zone or are discordant.

METHODS

In this multicenter, retrospective observational cohort study, we included consecutive patients with DRE who had undergone FDG-PET as part of their presurgical workup. We assessed the utility of FDG-PET, which was defined as contributing to the decision-making process to refer for resection or intracranial EEG (iEEG) or to conclude surgery was not feasible.

RESULTS

We included 951 patients in this study; 479 had temporal lobe epilepsy (TLE), 219 extratemporal epilepsy (ETLE), and 253 epilepsy of uncertain lobar origin. FDG-PET showed a distinct hypometabolism in 62% and was concordant with ictal EEG in 74% in TLE and in 56% in ETLE (p < .001). FDG-PET was useful in presurgical decision-making in 396 patients (47%) and most beneficial in TLE compared to ETLE (58% vs. 44%, p = .001). Overall, FDG-PET contributed to recommending resection in 78 cases (20%) and iEEG in 187 cases (47%); in 131 patients (33%), FDG-PET resulted in a conclusion that resection was not feasible. In TLE, seizure-freedom 1 year after surgery did not differ significantly (p = .48) between patients with negative MRI and EEG-PET concordance (n = 30, 65%) and those with positive MRI and concordant EEG (n = 46, 68%). In ETLE, half of patients with negative MRI and EEG-PET concordance and three quarters with positive MRI and concordant EEG were seizure-free postsurgery (n = 5 vs. n = 6, p = .28).

SIGNIFICANCE

This is the largest reported cohort of patients with DRE who received presurgical FDG-PET, showing that FDG-PET is a useful diagnostic tool. MRI-negative and MRI-positive cases with concordant FDG-PET results (with either EEG or MRI) had a comparable outcome after surgery. These findings confirm the significance of FDG-PET in presurgical epilepsy diagnostics.

Imaging of the Postoperative Skull Base and Cerebellopontine Angle

For pathologic conditions affecting the skull base and cerebellopontine angle, imaging techniques have advanced to assess for residual disease, disease progression, and postoperative complications. Knowledge regarding various surgical approaches of skull base tumor resection, expected postoperative appearance, and common postsurgical complications guides radiologic interpretation. Complexity of skull base anatomy, small size of the relevant structures, lack of familiarity with surgical techniques, and postsurgical changes confound radiologic evaluation. This article discusses the imaging techniques, surgical approaches, expected postoperative changes, and complications after surgery of the skull base, with emphasis on the cerebellopontine angle, anterior cranial fossa, and central skull base regions.

Parotid Warthin's tumor: novel MR imaging score as diagnostic indicator

OBJECTIVES

Despite known characteristic radiologic and clinical features, differentiation between Warthin's tumor (WT) and other parotid tumors remains challenging. The purpose of this study was to more precisely assess the MR imaging features of WT and to develop a scoring system combining the most specific characteristics.

METHODS

A total of 208 patients with parotid gland tumors and presurgical MRI were included. Tumors were divided into 5 histological subtypes, and different MRI features were compared between groups. An MRI scoring test was developed including MR parameters that contributed significantly in distinguishing WT from other tumors.

RESULTS

The best MRI features for differentiating between WTs from other tumors included bilaterality (P = 0.002), multifocality (P < 0.001), ADC values <905.1 (P < 0.001), and high signal intensity on T1-W images (P < 0.001). Six or more points on the 14-point scoring MRI scale was associated with an area under the curve of 0.99 (Accuracy of 98%), while a cut-off value of 7 indicated 100% specificity and 100% positive predictive value.

CONCLUSIONS

Ill-defined margins, low T1-W signal, and location in the upper 2/3 of the parotid gland excluded WTs in 100% of cases. The proposed scoring method allows WTs to be distinguished from other tumors with high accuracy.

KEY POINTS

Pembrolizumab for patients with leptomeningeal metastasis from solid tumors: efficacy, safety, and cerebrospinal fluid biomarkers

Background

The benefit of immune checkpoint inhibitors (ICIs) in patients with leptomeningeal metastases (LMM) is unknown.

Methods

We undertook a phase II trial of pembrolizumab in patients with LMM from solid tumors. Eligible patients had radiologic/cytologic LMM and Eastern Cooperative Oncology Group performance status 0–1. Pembrolizumab was administered intravenously at 200 mg q3W until disease progression/unacceptable toxicity. The primary endpoint was central nervous system (CNS) response after four cycles, defined radiologically/cytologically/clinically. Serial cerebrospinal fluid (CSF) was assessed for tumor-derived DNA (t-DNA) aneuploidy and cytokines.

Results

Thirteen of a planned 16 patients were treated between April 2017 and December 2019. The study closed early for poor accrual. Median age was 57 years (range: 22–79). Sixty-two percent of patients had tumors not traditionally ICI-responsive (hormone-receptor (HR)-positive breast carcinoma=39%; high-grade glioma=23%), while 38% had ICI-responsive tumors (non-small cell lung cancer (NSCLC)=23%, head and neck carcinoma=8%, cutaneous squamous carcinoma (CSC)=8%). CNS response was observed in 38% of patients at 12 weeks (95% CI 13.9% to 68.4%) by pre-defined criteria and LM-RANO, and 2 achieved durable complete responses (CSC=1, overall survival (OS) 3+ years; NSCLC=1, OS 9 months). Median CNS progression-free survival and OS was 2.9 months (95% CI 1.3 to NR) and 4.9 months (95% CI 3.7 to NR), respectively. Grade 3+ treatment-related adverse events occurred in 15% of patients. Sensitivity for LMM detection by t-DNA and cytopathology was 84.6% (95% CI 54.6% to 98.1%) and 53.9% (95% CI 25.1% to 80.8%), respectively. Pre-therapy and on-therapy CSF cytokine analysis demonstrated complete responders clustered together.

Conclusions

Pembrolizumab conferred a 38% CNS response rate in patients with LMM, a tolerable safety profile, and deep responses in selected patients with ICI-responsive tumors. CSF t-DNA may be sensitive for LMM detection, and immunologic subsets of CNS response warrant further study.

Trial registration number

NCT03091478

3D vertebrae labeling in spine CT: an accurate, memory-efficient (Ortho2D) framework

Purpose.Accurate localization and labeling of vertebrae in computed tomography (CT) is an important step toward more quantitative, automated diagnostic analysis and surgical planning. In this paper, we present a framework (called Ortho2D) for vertebral labeling in CT in a manner that is accurate and memory-efficient.Methods. Ortho2D uses two independent faster R-convolutional neural network networks to detect and classify vertebrae in orthogonal (sagittal and coronal) CT slices. The 2D detections are clustered in 3D to localize vertebrae centroids in the volumetric CT and classify the region (cervical, thoracic, lumbar, or sacral) and vertebral level. A post-process sorting method incorporates the confidence in network output to refine classifications and reduce outliers. Ortho2D was evaluated on a publicly available dataset containing 302 normal and pathological spine CT images with and without surgical instrumentation. Labeling accuracy and memory requirements were assessed in comparison to other recently reported methods. The memory efficiency of Ortho2D permitted extension to high-resolution CT to investigate the potential for further boosts to labeling performance.Results. Ortho2D achieved overall vertebrae detection accuracy of 97.1%, region identification accuracy of 94.3%, and individual vertebral level identification accuracy of 91.0%. The framework achieved 95.8% and 83.6% level identification accuracy in images without and with surgical instrumentation, respectively. Ortho2D met or exceeded the performance of previously reported 2D and 3D labeling methods and reduced memory consumption by a factor of ∼50 (at 1 mm voxel size) compared to a 3D U-Net, allowing extension to higher resolution datasets than normally afforded. The accuracy of level identification increased from 80.1% (for standard/low resolution CT) to 95.1% (for high-resolution CT).Conclusions. The Ortho2D method achieved vertebrae labeling performance that is comparable to other recently reported methods with significant reduction in memory consumption, permitting further performance boosts via application to high-resolution CT.

Segmental Imaging of the Trochlear Nerve: Anatomic and Pathologic Considerations

BACKGROUND

The trochlear nerve (the fourth cranial nerve) is the only cranial nerve that arises from the dorsal aspect of the midbrain. The nerve has a lengthy course making it highly susceptible to injury. It is also the smallest cranial nerve and is often difficult to identify on neuroimaging.

EVIDENCE ACQUISITION

High-resolution 3-dimensional skull base MRI allows for submillimeter isotropic acquisition and is optimal for cranial nerve evaluation. In this text, the detailed anatomy of the fourth cranial nerve applicable to imaging will be reviewed.

RESULTS

Detailed anatomic knowledge of each segment of the trochlear nerve is necessary in patients with trochlear nerve palsy. A systematic approach to identification and assessment of each trochlear nerve segment is essential. Pathologic cases are provided for each segment.

CONCLUSIONS

A segmental approach to high-resolution 3-dimensional MRI for the study of the trochlear nerve is suggested.

Immune-mediated ototoxicity associated with immune checkpoint inhibitors in patients with melanoma

Immune checkpoint inhibitors (ICIs) are associated with a range of organ-specific toxicities known as immune-related adverse events (irAEs). Immune-mediated ototoxicity from ICIs is poorly described. Herein, we describe the clinical presentation, diagnostic evaluation and management of six ICI-treated patients who developed immune-mediated ototoxicity, identified by a multidisciplinary immune-related toxicity team. This is the largest case series to date and identifies bilateral high-frequency hearing loss and tinnitus as the most common reported symptoms and can be associated with abnormal speech reception thresholds and word recognition ability on audiogram in select patients. We propose multidisciplinary evaluation of patients with suspected otologic irAEs including referral to otolaryngology, audiometry evaluation±magnetic resonance imaging for evaluation of suspected immune-mediated ototoxicity.

MRI features of intra-axial histiocytic brain mass lesions

AIM

To describe MRI features, including diffusion-weighted imaging (DWI), magnetic resonance spectroscopy (MRS), and perfusion-weighted imaging (PWI), of intra-axial tumour-like presentations of four different subtypes of histiocytosis.

MATERIAL AND METHODS

The brain MRI findings of 23 patients with histologically proven histiocytosis were reviewed retrospectively (11 Langerhans cell histiocytosis [LCH], eight Erdheim-Chester disease [ECD], one overlap form LCH/ECD, two Rosai-Dorfman disease [RDD], and one haemophagocytic lymphohistiocytosis [HLH]) with single or multiple enhancing intraparenchymal brain lesions.

RESULTS

Histiocytic brain mass lesions show some similar MRI features including Supra and/or infratentorial and/or paraventricular subcortical well-delineated masses, linear ependymal enhancement along the ventricles and brain stem lesions. Masses always present with mixed hyper- and hypointense signal on T2-weighted imaging (WI). Their enhancement is often homogeneous. Apparent diffusion coefficient (ADC) values are often normal or elevated.

CONCLUSION

The presence of multiple periventricular and subcortical enhancing lesions with mixed signal intensity on T2WI and normal or high ADC values should lead radiologists to consider the diagnosis of histiocytic lesions and search for associated systemic lesions.

Nonepithelial Tumors of the Larynx: Single-Institution 13-Year Review with Radiologic-Pathologic Correlation

Nonepithelial tumors of the larynx are rare and represent a minority of all laryngeal neoplasms. Imaging has an important role in the diagnosis, treatment planning, and surveillance of these entities. However, unfamiliarity with these neoplasms can cause diagnostic difficulties for radiologists, especially because many of the imaging findings are nonspecific. By using a systematic approach based on clinical history, patient age and gender, lesion location, endoscopic results, and specific imaging findings, the differential diagnosis can often be narrowed. These tumors typically affect the submucosal layer, so if a tumor has an intact mucosa at endoscopy, a nonepithelial neoplasm is the most likely diagnosis. Nonepithelial tumors of the larynx can arise from the laryngeal cartilage or muscle or from the surrounding lymphoid tissue or blood vessels. Consequently, imaging findings typically correspond to the specific cell type from which it originated. Recognizing specific features (eg, metaplastic bone formation, macroscopic fat, or enhancement pattern) can often help narrow the differential diagnosis. In addition, identification of noncircumscribed borders of the lesion and invasion of the adjacent structures is key to diagnosis of a malignant process rather than a benign neoplasm. Understanding the pathologic correlation is fundamental to understanding the radiologic manifestations and is ultimately crucial for differentiation of nonepithelial laryngeal neoplasms. Online supplemental material is available for this article. ^©RSNA, 2020.

Predictors of Free Flap Volume Loss in Nonosseous Reconstruction of Head and Neck Oncologic Defects

OBJECTIVES

Free tissue reconstruction of the head and neck must be initially overcorrected due to expected postoperative free flap volume loss, which can be accelerated by adjuvant radiation therapy. In this study, we aim to identify patient and treatment-specific factors that may significantly contribute to this phenomenon and translate these characteristics into a predictive model for expected percent free flap volume loss in a given patient.

METHODS

Patients with a history of oral cavity and/or oropharyngeal cancer who underwent nonosseous free flap reconstruction were reviewed between January 2009 and November 2018 at a tertiary care center. Demographics/characteristics, total radiation dose, radiation fractionation (RF), and pre/postradiation free flap volume as evaluated by computed tomography imaging were collected. Free flap volume was measured by a fellowship-trained neuroradiologist in all cases. Only patients receiving adjuvant radiotherapy with available pre/postradiation imaging were included. Multivariable linear regression modeling for prediction of free flap volume loss was performed with optimization via stepwise elimination.

RESULTS

Thirty patients were included for analysis. Mean flap volume loss was 42.7% ± 17.4%. The model predicted flap volume loss in a significant fashion (P = .004, R² = 0.49) with a mean magnitude of error of 9.8% ± 7.5%. Age (β = 0.01, P = .003) and RF (β = -0.01, P = .009) were individual predictors of flap volume loss.

CONCLUSIONS

Our model predicts percent free flap volume loss in a significant fashion. Age and RF are individual predictors of free flap volume loss, the latter being a novel finding that is also modifiable through hyperfractionation radiotherapy schedules.

Cone-beam CT for imaging of the head/brain: Development and assessment of scanner prototype and reconstruction algorithms

PURPOSE

Our aim was to develop a high-quality, mobile cone-beam computed tomography (CBCT) scanner for point-of-care detection and monitoring of low-contrast, soft-tissue abnormalities in the head/brain, such as acute intracranial hemorrhage (ICH). This work presents an integrated framework of hardware and algorithmic advances for improving soft-tissue contrast resolution and evaluation of its technical performance with human subjects.

METHODS

Four configurations of a CBCT scanner prototype were designed and implemented to investigate key aspects of hardware (including system geometry, antiscatter grid, bowtie filter) and technique protocols. An integrated software pipeline (c.f., a serial cascade of algorithms) was developed for artifact correction (image lag, glare, beam hardening and x-ray scatter), motion compensation, and three-dimensional image (3D) reconstruction [penalized weighted least squares (PWLS), with a hardware-specific statistical noise model]. The PWLS method was extended in this work to accommodate multiple, independently moving regions with different resolution (to address both motion compensation and image truncation). Imaging performance was evaluated quantitatively and qualitatively with 41 human subjects in the neurosciences critical care unit (NCCU) at our institution.

RESULTS

The progression of four scanner configurations exhibited systematic improvement in the quality of raw data by variations in system geometry (source-detector distance), antiscatter grid, and bowtie filter. Quantitative assessment of CBCT images in 41 subjects demonstrated: ~70% reduction in image nonuniformity with artifact correction methods (lag, glare, beam hardening, and scatter); ~40% reduction in motion-induced streak artifacts via the multi-motion compensation method; and ~15% improvement in soft-tissue contrast-to-noise ratio (CNR) for PWLS compared to filtered backprojection (FBP) at matched resolution. Each of these components was important to improve contrast resolution for point-of-care cranial imaging.

CONCLUSIONS

This work presents the first application of a high-quality, point-of-care CBCT system for imaging of the head/ brain in a neurological critical care setting. Hardware configuration iterations and an integrated software pipeline for artifacts correction and PWLS reconstruction mitigated artifacts and noise to achieve image quality that could be valuable for point-of-care detection and monitoring of a variety of intracranial abnormalities, including ICH and hydrocephalus.

Automatic analysis of global spinal alignment from simple annotation of vertebral bodies

Purpose: Measurement of global spinal alignment (GSA) is an important aspect of diagnosis and treatment evaluation for spinal deformity but is subject to a high level of inter-reader variability. Approach: Two methods for automatic GSA measurement are proposed to mitigate such variability and reduce the burden of manual measurements. Both approaches use vertebral labels in spine computed tomography (CT) as input: the first (EndSeg) segments vertebral endplates using input labels as seed points; and the second (SpNorm) computes a two-dimensional curvilinear fit to the input labels. Studies were performed to characterize the performance of EndSeg and SpNorm in comparison to manual GSA measurement by five clinicians, including measurements of proximal thoracic kyphosis, main thoracic kyphosis, and lumbar lordosis. Results: For the automatic methods, 93.8% of endplate angle estimates were within the inter-reader 95% confidence interval ( CI 95 ). All GSA measurements for the automatic methods were within the inter-reader CI 95 , and there was no statistically significant difference between automatic and manual methods. The SpNorm method appears particularly robust as it operates without segmentation. Conclusions: Such methods could improve the reproducibility and reliability of GSA measurements and are potentially suitable to applications in large datasets-e.g., for outcome assessment in surgical data science.

Subperiosteal Hematoma of the Orbit: A Variety of Presentations

Subperiosteal hematoma of the orbit is an uncommon radiologic finding. Most typically, the hemorrhage is in the superior aspect of the orbit, however, location within the orbit may vary. Subperiosteal hematoma of the orbit may be associated with trauma. Nontraumatic etiology has also been well documented. We present a series of three cases, to illustrate typical and atypical radiologic findings of subperiosteal hematoma of the orbit, both traumatic and nontraumatic. Review of the pertinent radiologic literature and its relation to the cases presented here is also provided.

From presumed benign neck masses to delayed recognition of human papillomavirus-positive oropharyngeal cancer

OBJECTIVES/HYPOTHESIS

To describe patients with delayed diagnosis of human papillomavirus-positive oropharyngeal squamous cell carcinoma (HPV-OPC) after initial incorrect diagnosis of branchial cleft cyst or nondiagnostic workup of unilateral neck mass.

STUDY DESIGN

Retrospective case series.

METHODS

Patients with delayed diagnosis of HPV-OPC after initial nondiagnostic workup for unilateral neck mass were eligible. Medical record abstraction was performed to describe clinical characteristics at initial presentation and later diagnosis of HPV-OPC. To estimate nodal growth rates, the short axis diameter of the lymph nodes was determined from imaging reports.

RESULTS

Six patients met eligibility criteria. After a median interval of 42 months (range, 3 months-7 years) from initial presentation with unilateral neck mass, patients were diagnosed with HPV-OPC. At the time of HPV-OPC diagnosis, five were AJCC eighth edition overall stage I, and one was stage II. Primary tumors were T0 or T1 in the majority (83.3%, n = 5). Among five patients with available serial imaging, despite diagnostic delay, three of five still had a single lymph node without involvement of additional nodes, whereas the remaining two developed additional suspicious nodes (ipsilateral and contralateral). Two of five developed evidence of extranodal extension. Median lymph node growth was 9.5% per year (range, -6% to 32%).

CONCLUSIONS

Although the natural history of HPV-OPC is not well understood, this case series suggests that it can be slow growing and mimic benign processes, leading to diagnostic delays. Adults presenting with neck masses should undergo complete diagnostic evaluation.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:392-397, 2020.

Does the Presence or Absence of DESH Predict Outcomes in Adult Hydrocephalus?

BACKGROUND AND PURPOSE

The DESH (disproportionately enlarged subarachnoid-space hydrocephalus) pattern of "tight high-convexity and medial subarachnoid spaces, and enlarged Sylvian fissures with ventriculomegaly" is used to determine which patients undergo an operation for adult hydrocephalus at many centers. Our aim was to review adult hydrocephalus cases when DESH has not been a criterion for an operation to determine the prevalence of DESH among the cohort and compare the surgical outcomes in the presence or absence of DESH.

MATERIALS AND METHODS

A retrospective cohort study was conducted at a single institution (Johns Hopkins Hospital) to include patients surgically treated for adult hydrocephalus between 2003 and 2014 drawn from a data base of patients who had undergone standardized hydrocephalus protocol MR imaging. Preoperative imaging was reviewed by 2 blinded neuroradiologists to characterize the presence of DESH. Preoperative and postoperative clinical symptomatology was recorded. Frequencies were compared using the Fisher exact test, and nonparametric means were compared using the Mann-Whitney U Test.

RESULTS

One hundred thirty-three subjects were identified and included (96 DESH absent, 37 DESH present). Shunting led to significant improvement in gait and urinary and cognitive symptoms for the overall cohort and for patients with and without DESH (P < .05). The Fisher exact test did not demonstrate any significant differences in either gait or urinary or cognitive symptom improvement between patients with or without DESH (P > .05).

CONCLUSIONS

The current study demonstrated symptom improvement in patients with adult hydrocephalus following shunting, with no significant differences between subjects with and without DESH. Thus, shunt insertion for patients with adult hydrocephalus should not rely solely on the presence of preoperative DESH findings.

Utility of the Vidian Canal in Endoscopic Skull Base Surgery: Detailed Anatomy and Relationship to the Internal Carotid Artery

OBJECTIVE

To investigate key anatomic features of the vidian canal that have a critical role in planning and performing endoscopic skull base surgeries.

METHODS

We reviewed skull base computed tomographic images of 640 consecutive subjects. Studies were analyzed in axial, coronal and sagittal planes.

RESULTS

The mean (±SD) length of the vidian canal was 15.4 ± 2.0 mm in female subjects and 16.6 ± 1.7 mm in male subjects, and the difference between genders was statistically significant (P < 0.001). The most common rostral-caudal course of the vidian canal was medial to lateral and was followed by the straight course, tortuous course, and lateral-to-medial course. The frequency of pneumatization pattern from most common to least common was types 0, III, II and I. Of 342 evaluated sides, the vidian canal was located below the level of the anterior genu of petrous ICA in 303 (89%) sides, at same level with the anterior genu of petrous ICA in twenty-five(7%) sides, and above the level of the anterior genu of petrous ICA in fourteen(4.1%) sides.

CONCLUSIONS

A variety of previously undefined features of the vidian canal that can alter the course of surgical procedure were defined. The position of the vidian canal with respect to the petrous internal carotid artery (ICA) was extensively described. From a surgical standpoint, a working room inferior and medial to the vidian canal might not always be a safe approach, because the vidian canal could be located superior to the level of the anterior genu of petrous ICA according to our findings in the present study.

Contrast-Enhanced CISS Imaging for Evaluation of Neurovascular Compression in Trigeminal Neuralgia: Improved Correlation with Symptoms and Prediction of Surgical Outcomes

BACKGROUND AND PURPOSE

Thin-section MR imaging through the posterior fossa is frequently used for trigeminal neuralgia. Typical heavily T2-weighted imaging methods yield high anatomic detail and contrast between CSF and neurovascular structures, but poor contrast between vessels and nerves. We hypothesized that the addition of gadolinium-based contrast material to 3D-constructive interference in steady-state imaging would improve the characterization of trigeminal compression.

MATERIALS AND METHODS

Retrospective review of high-resolution MRIs was performed in patients without prior microvascular decompression. 3D-CISS imaging without contrast and with contrast for 81 patients with trigeminal neuralgia and 15 controls was intermixed and independently reviewed in a blinded fashion. Cisternal segments of both trigeminal nerves were assessed for the grade of neurovascular conflict, cross-sectional area, and degree of flattening. Data were correlated with symptom side and pain relief after microvascular decompression using the Fisher exact test, receiver operating curve analysis, and a paired t test.

RESULTS

Contrast-enhanced CISS more than doubled the prevalence of the highest grade of neurovascular conflict (14.8% versus 33.3%, P = .001) and yielded significantly lower cross-sectional area (P = 8.6 × 10^-6) and greater degree of flattening (P = .02) for advanced-grade neurovascular conflict on the symptoms side compared with non-contrast-enhanced CISS. Patients with complete pain relief after microvascular decompression had significantly lower cross-sectional area on contrast-enhanced CISS compared with non-contrast-enhanced CISS on preoperative imaging (P = 2.0 × 10^-7). Performance based on receiver operating curve analysis was significantly improved for contrast-enhanced CISS compared with non-contrast-enhanced CISS.

CONCLUSIONS

The addition of contrast material to 3D-CISS imaging improves the performance of identifying unilateral neurovascular compression for symptomatic trigeminal neuralgia and predicting outcomes after microvascular decompression.

Clinical Translation of the LevelCheck Decision Support Algorithm for Target Localization in Spine Surgery

Recent work has yielded a method for automatic labeling of vertebrae in intraoperative radiographs as an assistant to manual level counting. The method, called LevelCheck, previously demonstrated promise in phantom studies and retrospective studies. This study aims to: (#1) Analyze the effect of LevelCheck on accuracy and confidence of localization in two modes: (a) Independent Check (labels displayed after the surgeon's decision) and (b) Active Assistant (labels presented before the surgeon's decision). (#2) Assess the feasibility and utility of LevelCheck in the operating room. Two studies were conducted: a laboratory study investigating these two workflow implementations in a simulated operating environment with 5 surgeons, reviewing 62 cases selected from a dataset of radiographs exhibiting a challenge to vertebral localization; and a clinical study involving 20 patients undergoing spine surgery. In Study #1, the median localization error without assistance was 30.4% (IQR = 5.2%) due to the challenging nature of the cases. LevelCheck reduced the median error to 2.4% for both the Independent Check and Active Assistant modes (p < 0.01). Surgeons found LevelCheck to increase confidence in 91% of cases. Study #2 demonstrated accuracy in all cases. The algorithm runtime varied from 17 to 72 s in its current implementation. The algorithm was shown to be feasible, accurate, and to improve confidence during surgery.

Reconstruction-of-difference (RoD) imaging for cone-beam CT neuro-angiography

Timely evaluation of neurovasculature via CT angiography (CTA) is critical to the detection of pathology such as ischemic stroke. Cone-beam CTA (CBCT-A) systems provide potential advantages in the timely use at the point-of-care, although challenges of a relatively slow gantry rotation speed introduce tradeoffs among image quality, data consistency and data sparsity. This work describes and evaluates a new reconstruction-of-difference (RoD) approach that is robust to such challenges. A fast digital simulation framework was developed to test the performance of the RoD over standard reference reconstruction methods such as filtered back-projection (FBP) and penalized likelihood (PL) over a broad range of imaging conditions, grouped into three scenarios to test the trade-off between data consistency, data sparsity and peak contrast. Two experiments were also conducted using a CBCT prototype and an anthropomorphic neurovascular phantom to test the simulation findings in real data. Performance was evaluated primarily in terms of normalized root mean square error (NRMSE) in comparison to truth, with reconstruction parameters chosen to optimize performance in each case to ensure fair comparison. The RoD approach reduced NRMSE in reconstructed images by up to 50%-53% compared to FBP and up to 29%-31% compared to PL for each scenario. Scan protocols well suited to the RoD approach were identified that balance tradeoffs among data consistency, sparsity and peak contrast-for example, a CBCT-A scan with 128 projections acquired in 8.5 s over a 180°  +  fan angle half-scan for a time attenuation curve with ~8.5 s time-to-peak and 600 HU peak contrast. With imaging conditions such as the simulation scenarios of fixed data sparsity (i.e. varying levels of data consistency and peak contrast), the experiments confirmed the reduction of NRMSE by 34% and 17% compared to FBP and PL, respectively. The RoD approach demonstrated superior performance in 3D angiography compared to FBP and PL in all simulation and physical experiments, suggesting the possibility of CBCT-A on low-cost, mobile imaging platforms suitable to the point-of-care. The algorithm demonstrated accurate reconstruction with a high degree of robustness against data sparsity and inconsistency.

Task-based statistical image reconstruction for high-quality cone-beam CT

Task-based analysis of medical imaging performance underlies many ongoing efforts in the development of new imaging systems. In statistical image reconstruction, regularization is often formulated in terms to encourage smoothness and/or sharpness (e.g. a linear, quadratic, or Huber penalty) but without explicit formulation of the task. We propose an alternative regularization approach in which a spatially varying penalty is determined that maximizes task-based imaging performance at every location in a 3D image. We apply the method to model-based image reconstruction (MBIR-viz., penalized weighted least-squares, PWLS) in cone-beam CT (CBCT) of the head, focusing on the task of detecting a small, low-contrast intracranial hemorrhage (ICH), and we test the performance of the algorithm in the context of a recently developed CBCT prototype for point-of-care imaging of brain injury. Theoretical predictions of local spatial resolution and noise are computed via an optimization by which regularization (specifically, the quadratic penalty strength) is allowed to vary throughout the image to maximize local task-based detectability index ([Formula: see text]). Simulation studies and test-bench experiments were performed using an anthropomorphic head phantom. Three PWLS implementations were tested: conventional (constant) penalty; a certainty-based penalty derived to enforce constant point-spread function, PSF; and the task-based penalty derived to maximize local detectability at each location. Conventional (constant) regularization exhibited a fairly strong degree of spatial variation in [Formula: see text], and the certainty-based method achieved uniform PSF, but each exhibited a reduction in detectability compared to the task-based method, which improved detectability up to ~15%. The improvement was strongest in areas of high attenuation (skull base), where the conventional and certainty-based methods tended to over-smooth the data. The task-driven reconstruction method presents a promising regularization method in MBIR by explicitly incorporating task-based imaging performance as the objective. The results demonstrate improved ICH conspicuity and support the development of high-quality CBCT systems.

Magnetic Resonance Imaging at 1.5 Tesla With a Cochlear Implant Magnet in Place: Image Quality and Usability

OBJECTIVE

To study the quality and usability of magnetic resonance imaging (MRI) obtained with a cochlear implant magnet in situ.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary care center.

PATIENTS

All patients who underwent brain MRI with a cochlear implant magnet in situ from 2007 to 2016.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Grade of view of the ipsilateral internal auditory canal (IAC) and cerebellopontine angle (CPA).

RESULTS

Inclusion criteria were met by 765 image sequences in 57 MRI brain scans. For the ipsilateral IAC, significant predictors of a grade 1 (normal) view included: absence of fat saturation algorithm (p = 0.001), nonaxial plane of imaging (p = 0.01), and contrast administration (p = 0.001). For the ipsilateral CPA, significant predictors of a grade 1 view included: absence of fat saturation algorithm (p = 0.001), high-resolution images (p = 0.001), and nonaxial plane of imaging (p = 0.001). Overall, coronal T1 high-resolution images produced the highest percentage of grade 1 views (89%). Fat saturation also caused a secondary ring-shaped distortion artifact, which impaired the view of the contralateral CPA 52.7% of the time, and the contralateral IAC 42.8% of the time. MRI scans without any usable (grade 1) sequences had fewer overall sequences (N = 4.3) than scans with at least one usable sequence (N = 7.1, p = 0.001).

CONCLUSION

MRI image quality with a cochlear implant magnet in situ depends on several factors, which can be modified to maximize image quality in this unique patient population.

Technical assessment of a prototype cone-beam CT system for imaging of acute intracranial hemorrhage

PURPOSE

A cone-beam CT scanner has been developed for detection and monitoring of traumatic brain injury and acute intracranial hemorrhage (ICH) at the point of care. This work presents a technical assessment of imaging performance and dose for the scanner in phantom and cadaver studies as a prerequisite to clinical translation.

METHODS

The scanner incorporates a compact, rotating-anode x-ray source and a flat-panel detector (43 × 43 cm²) on a mobile U-arm gantry with source-axis distance = 550 mm and source-detector distance = 1000 mm. Central and peripheral doses were measured in 16 cm diameter CTDI phantoms using a 0.6 cm³ Farmer ionization chamber for various scan techniques and as a function of longitudinal position, including out of field. Spatial resolution, contrast, noise, and image uniformity were assessed in quantitative and anthropomorphic head phantoms. Two reconstruction protocols were evaluated, including filtered backprojection (FBP) for high-resolution bone imaging and penalized weighted least squares (PWLS) reconstruction for low-contrast soft tissue (ICH) visualization. A fresh cadaver was imaged with and without simulated ICH using the scanner as well as a diagnostic multidetector CT (MDCT) scanner using a standard head protocol. Images were interpreted by a fellowship-trained neuroradiologist for imaging tasks of ICH detection, gray-white-CSF differentiation, detection of midline shift, and fracture detection.

RESULTS

The nominal scan protocol involved 720 projections acquired over a 360° orbit at 100 kV and 216 mAs, giving a dose (weighted CTDI) of 22.8 mGy (∼1.2 mSv effective dose). Out-of-field dose decreased to <10% within 6 cm of the field edge (approximate to the thyroid position). Image uniformity demonstrated <1% variation between the edge of the field (near the cranium) and center of the image. The high-resolution FBP reconstruction protocol showed ∼0.9 mm point spread function (PSF) full-width at half-maximum (FWHM). The smooth PWLS reconstruction protocol yielded ∼1.2 mm PSF FWHM and contrast-to-noise ratio exceeding 5.7 in ∼50 HU spherical ICH, resulting in conspicuous depiction of ICH down to ∼2 mm (the smallest diameter investigated). Cadaver images demonstrated good differentiation of brain and CSF (sufficient, but inferior to MDCT, recognizing that the CBCT dose was one-third that of MDCT), excellent visualization of cranial sutures and fracture (potentially superior to MDCT), clear detection of midline shift, and conspicuous detection of ICH.

CONCLUSIONS

Technical assessment of the prototype demonstrates dose characteristics and imaging performance consistent with point-of-care detection and monitoring of head injury-most notably, conspicuous detection of ICH-and supports translation of the system to clinical studies.

Factors Determining Scientific Paper Productivity by Neuroradiology Fellows

RATIONALE AND OBJECTIVES

We sought to determine (1) whether United States Medical Licensing Examination (USMLE) scores predict academic productivity in neuroradiology fellows as measured by publications and citations, and (2) what factors predict such productivity.

MATERIALS AND METHODS

We reviewed the USMLE scores, gender, medical school location attended, publication record before and during fellowship, fellowship evaluation ratings and subsequent practice site (private vs academic) of neuroradiology fellows from 2004 to 2014 to determine relationships with publications and citations after fellowship. Spearman's correlation and Poisson regression analyses were performed to assess the association between these factors and quantity of publications and citations per year after fellowship.

RESULTS

USMLE scores and fellowship evaluation scores correlated inversely with radiology publications and citations. There were strong correlations between publication records before or during fellowship and after fellowship. Fellows from international medical schools, with PhD degrees, and those fellows proceeding to academic practice had more publications before or during and after neuroradiology fellowship.

CONCLUSIONS

The best predictors of whether a graduating neuroradiology fellow will publish and have high citation rates is prior publication record, a PhD degree, and staying in academics. USMLE scores and evaluations during the fellowship were inversely correlated with publication measures of academic productivity.

Joubert syndrome: neuroimaging findings in 110 patients in correlation with cognitive function and genetic cause

BACKGROUND

Joubert syndrome is a clinically and genetically heterogeneous ciliopathy. Neuroimaging findings have not been systematically evaluated in a large cohort of patients with Joubert syndrome in correlation with molecular genetic cause and cognitive function.

METHODS

Brain MRI of 110 patients with Joubert syndrome was included in this study. A comprehensive evaluation of brain MRI studies for infratentorial and supratentorial morphological abnormalities was performed. Genetic cause was identified by whole-exome sequencing, and cognitive functions were assessed with age-appropriate neurocognitive tests in a subset of patients.

RESULTS

The cerebellar hemispheres were enlarged in 18% of the patients, mimicking macrocerebellum. The posterior fossa was enlarged in 42% of the patients, resembling Dandy-Walker malformation. Abnormalities of the brainstem, such as protuberance at the ventral contour of the midbrain, were present in 66% of the patients. Abnormalities of the supratentorial brain were present in approximately one-third of the patients, most commonly malrotation of the hippocampi. Mild ventriculomegaly, which typically did not require shunting, was present in 23% of the patients. No correlation between neuroimaging findings and molecular genetic cause was apparent. A novel predictor of outcome was identified; the more severe the degree of vermis hypoplasia, the worse the neurodevelopmental outcome was.

CONCLUSIONS

The spectrum of neuroimaging findings in Joubert syndrome is wide. Neuroimaging does not predict the genetic cause, but may predict the neurodevelopmental outcome. A high degree of vermis hypoplasia correlates with worse neurodevelopmental outcome. This finding is important for prognostic counselling in Joubert syndrome.

Multi-resolution statistical image reconstruction for mitigation of truncation effects: application to cone-beam CT of the head

A prototype cone-beam CT (CBCT) head scanner featuring model-based iterative reconstruction (MBIR) has been recently developed and demonstrated the potential for reliable detection of acute intracranial hemorrhage (ICH), which is vital to diagnosis of traumatic brain injury and hemorrhagic stroke. However, data truncation (e.g. due to the head holder) can result in artifacts that reduce image uniformity and challenge ICH detection. We propose a multi-resolution MBIR method with an extended reconstruction field of view (RFOV) to mitigate truncation effects in CBCT of the head. The image volume includes a fine voxel size in the (inner) nontruncated region and a coarse voxel size in the (outer) truncated region. This multi-resolution scheme allows extension of the RFOV to mitigate truncation effects while introducing minimal increase in computational complexity. The multi-resolution method was incorporated in a penalized weighted least-squares (PWLS) reconstruction framework previously developed for CBCT of the head. Experiments involving an anthropomorphic head phantom with truncation due to a carbon-fiber holder were shown to result in severe artifacts in conventional single-resolution PWLS, whereas extending the RFOV within the multi-resolution framework strongly reduced truncation artifacts. For the same extended RFOV, the multi-resolution approach reduced computation time compared to the single-resolution approach (viz. time reduced by 40.7%, 83.0%, and over 95% for an image volume of 600³, 800³, 1000³ voxels). Algorithm parameters (e.g. regularization strength, the ratio of the fine and coarse voxel size, and RFOV size) were investigated to guide reliable parameter selection. The findings provide a promising method for truncation artifact reduction in CBCT and may be useful for other MBIR methods and applications for which truncation is a challenge.

Evaluation of detector readout gain mode and bowtie filters for cone-beam CT imaging of the head

The effects of detector readout gain mode and bowtie filters on cone-beam CT (CBCT) image quality and dose were characterized for a new CBCT system developed for point-of-care imaging of the head, with potential application to diagnosis of traumatic brain injury, intracranial hemorrhage (ICH), and stroke. A detector performance model was extended to include the effects of detector readout gain on electronic digitization noise. The noise performance for high-gain (HG), low-gain (LG), and dual-gain (DG) detector readout was evaluated, and the benefit associated with HG mode in regions free from detector saturation was quantified. Such benefit could be realized (without detector saturation) either via DG mode or by incorporation of a bowtie filter. Therefore, three bowtie filters were investigated that varied in thickness and curvature. A polyenergetic gain correction method was developed to equalize the detector response between the flood-field and projection data in the presence of a bowtie. The effect of bowtie filters on dose, scatter-to-primary ratio, contrast, and noise was quantified in phantom studies, and results were compared to a high-speed Monte Carlo (MC) simulation to characterize x-ray scatter and dose distributions in the head. Imaging in DG mode improved the contrast-to-noise ratio (CNR) by ~15% compared to LG mode at a dose (D 0, measured at the center of a 16 cm CTDI phantom) of 19 mGy. MC dose calculations agreed with CTDI measurements and showed that bowtie filters reduce peripheral dose by as much as 50% at the same central dose. Bowtie filters were found to increase the CNR per unit square-root dose near the center of the image by ~5-20% depending on bowtie thickness, but reduced CNR in the periphery by ~10-40%. Images acquired at equal CTDIw with and without a bowtie demonstrated a 24% increase in CNR at the center of an anthropomorphic head phantom. Combining a thick bowtie filter with a short arc (180°  +  fan angle) scan centered on the posterior of the head reduced dose to the eye lens by up to 90%. Acquisition in DG mode (without a bowtie filter) was beneficial to the detection of small, low contrast lesions (e.g. subtle ICH) in CBCT. While bowtie filters were found to reduce dose, mitigate sensor saturation at the periphery in HG mode, and improve CNR at the center of the image, the image quality at the periphery was slightly reduced compared to DG mode, and the use of a bowtie required careful implementation of the polyenergetic flood-field correction to avoid artifacts.

Imaging Appearance of SMARCB1 (INI1)-Deficient Sinonasal Carcinoma: A Newly Described Sinonasal Malignancy

SMARCB1 (INI1)-deficient sinonasal carcinomas were first described in 2014, and this series of 17 cases represents the first imaging description. This tumor is part of a larger group of SMARCB1-deficient neoplasms, characterized by aggressive behavior and a rhabdoid cytopathologic appearance, that affect multiple anatomic sites. Clinical and imaging features overlap considerably with other aggressive sinonasal malignancies such as sinonasal undifferentiated carcinoma, which represents a common initial pathologic diagnosis in this entity. SMARCB1 (INI1)-deficient sinonasal tumors occurred most frequently in the nasoethmoidal region with invasion of the adjacent orbit and anterior cranial fossa. Avid contrast enhancement, intermediate to low T2 signal, and FDG avidity were frequent imaging features. Approximately half of the lesions demonstrated calcification, some with an unusual "hair on end" appearance, suggesting aggressive periosteal reaction.

High-Resolution MRI Findings following Trigeminal Rhizotomy

BACKGROUND AND PURPOSE

Patients with trigeminal neuralgia often undergo trigeminal rhizotomy via radiofrequency thermocoagulation or glycerol injection for treatment of symptoms. To date, radiologic changes in patients with trigeminal neuralgia post-rhizotomy have not been described, to our knowledge. The aim of this study was to evaluate patients after trigeminal rhizotomy to characterize post-rhizotomy changes on 3D high-resolution MR imaging.

MATERIALS AND METHODS

A retrospective review of trigeminal neuralgia protocol studies was performed in 26 patients after rhizotomy compared with 54 treatment-naïve subjects with trigeminal neuralgia. Examinations were reviewed independently by 2 neuroradiologists blinded to the side of symptoms and treatment history. The symmetry of Meckel's cave on constructive interference in steady-state and the presence of contrast enhancement within the trigeminal nerves on volumetric interpolated breath-hold examination images were assessed subjectively. The signal intensity of Meckel's cave was measured on coronal noncontrast constructive interference in steady-state imaging on each side.

RESULTS

Post-rhizotomy changes included subjective clumping of nerve roots and/or decreased constructive interference in steady-state signal intensity within Meckel's cave, which was identified in 17/26 (65%) patients after rhizotomy and 3/54 (6%) treatment-naïve patients (P < .001). Constructive interference in steady-state signal intensity within Meckel's cave was, on average, 13% lower on the side of the rhizotomy in patients posttreatment compared with a 1% difference in controls (P < .001). Small regions of temporal encephalomalacia were noted in 8/26 (31%) patients after rhizotomy and 0/54 (0%) treatment-naïve patients (P < .001).

CONCLUSIONS

Post-trigeminal rhizotomy findings frequently include nerve clumping and decreased constructive interference in steady-state signal intensity in Meckel's cave. Small areas of temporal lobe encephalomalacia are encountered less frequently.

Task-Based Regularization Design for Detection of Intracranial Hemorrhage in Cone-Beam CT

Prompt and reliable detection of acute intracranial hemorrhage (ICH) is critical to treatment of a number of neurological disorders. Cone-beam CT (CBCT) systems are potentially suitable for detecting ICH (contrast 40-80 HU, size down to 1 mm) at the point of care but face major challenges in image quality requirements. Statistical reconstruction demonstrates improved noise-resolution tradeoffs in CBCT head imaging, but its capability in improving image quality with respect to the task of ICH detection remains to be fully investigated. Moreover, statistical reconstruction typically exhibits nonuniform spatial resolution and noise characteristics, leading to spatially varying detectability of ICH for a conventional penalty. In this work, we propose a spatially varying penalty design that maximizes detectability of ICH at each location throughout the image. We leverage theoretical analysis of spatial resolution and noise for a penalized weighted least-squares (PWLS) estimator, and employ a task-based imaging performance descriptor in terms of detectability index using a nonprewhitening observer model. Performance prediction was validated using a 3D anthropomorphic head phantom. The proposed penalty achieved superior detectability throughout the head and improved detectability in regions adjacent to the skull base by ~10% compared to a conventional uniform penalty. PWLS reconstruction with the proposed penalty demonstrated excellent visualization of simulated ICH in different regions of the head and provides further support for development of dedicated CBCT head scanning at the point-of-care in the neuro ICU and OR.

Evaluation: Imaging Studies

The malignant or benign nature of a salivary gland (SG) tumor can be predicted with reasonably high accuracy by imaging. There is some overlap between the imaging findings of benign and malignant tumors, particularly for low-grade malignancies, and tissue diagnosis remains necessary for definitive diagnosis. Magnetic resonance imaging is the modality of choice for the evaluation of salivary neoplasms, as it allows for delineation of local infiltration, perineural spread and intracranial extension. This review will focus on the advanced imaging techniques that help to characterize SG tumors. A brief overview of the conventional imaging features of SG neoplasms is necessary before a discussion of the advanced imaging methods.