Early Postoperative Magnetic Resonance Imaging Findings Related to Electrocauterization for Cerebellar Reduction During Chiari Decompression Surgery.

BACKGROUND: Cerebellar tonsillar reduction or resection can be performed as part of the surgical management of Chiari type 1 malformation when it is accompanied by symptomatic brainstem compression or syringomyelia. The purpose of this study is to characterize the early postoperative magnetic resonance imaging (MRI) findings in patients with Chiari type 1 malformations who undergo cerebellar tonsillar reduction via electrocautery. METHODS: The extent of cytotoxic edema and microhemorrhages demonstrated on MRI scans obtained within 9 days following surgery was assessed and correlated with neurological symptoms. RESULTS: Cytotoxic edema was found on all postoperative MRI examinations included in this series, with superimposed hemorrhage in 12 of 16 patients (75%) and was primarily located along the margins of the cauterized inferior cerebellum. Cytotoxic edema was present beyond the margins of the cauterized cerebellar tonsils in 5 of 16 patients (31%) and was associated with new focal neurological deficits in 4 of 5 patients (80%). CONCLUSION: Cytotoxic edema and hemorrhages along the cerebellar tonsil cautery margins can be expected findings in early postoperative MRI in patients who undergo Chiari decompression accompanied by tonsillar reduction. However, the presence of cytotoxic edema beyond these regions can be associated with new focal neurological symptoms.

Analysis of head CT scans flagged by deep learning software for acute intracranial hemorrhage.

PURPOSE: To analyze the implementation of deep learning software for the detection and worklist prioritization of acute intracranial hemorrhage on non-contrast head CT (NCCT) in various clinical settings at an academic medical center. METHODS: Urgent NCCT scans were reviewed by the Aidoc (Tel Aviv, Israel) neural network software. All cases flagged by the software as positive for acute intracranial hemorrhage on the neuroradiology worklist were prospectively included in this assessment. The scans were classified regarding presence and type of hemorrhage, whether these were initial or follow-up scans, and patient visit location, including trauma/emergency, inpatient, and outpatient departments. RESULTS: During the 2 months of enrollment, 373 NCCT scans were flagged by the Aidoc software for possible intracranial hemorrhage out of 2011 scans analyzed (18.5%). Among the flagged cases, 275 (72.4%) were positive; 290 (77.7%) were inpatient cases, 75 (20.1%) were trauma/emergency cases, and eight (2.1%) were outpatient cases, and 229 of 373 (62.5%) were follow-up cases, of which 219 (95.6%) inpatient cases. Among the 144 new cases flagged for hemorrhage, 66 (44.4%) were positive, of which 39 (58.2%) were trauma/emergency cases. The overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 88.7%, 94.2% and 73.7%, 97.7%, and 93.4%, respectively. The accuracy of the intracranial hemorrhage detection was significantly higher for emergency cases than for inpatient cases (96.5% versus 89.4%). CONCLUSION: This study reveals that the performance of the deep learning software for acute intracranial hemorrhage detection varies depending upon the patient visit location. Furthermore, a substantial portion of flagged cases were follow-up exams, the majority of which were inpatient exams. These findings can help optimize the artificial intelligence-driven clincical workflow.

Baseline Computed Tomography Radiomic and Genomic Assessment of Head and Neck Squamous Cell Carcinoma.

PURPOSE: To determine the relationship between computed tomography (CT) radiomic features and gene expression levels in head and neck squamous cell carcinoma (HNSCC). METHODS: This retrospective study included 66 patients with HNSCC primary lesions (36 oropharyngeal, 6 hypopharyngeal, 10 laryngeal, 14 oral cavity). Gene expression information for 6 targetable genes (fibroblast growth factor receptor [FGFR]1, epidermal growth factor receptor [EGFR], FGFR2, FGFR3, EPHA2, PIK3CA) was obtained via Agilent microarrays from samples collected between 1997 and 2010. Pretreatment contrast-enhanced soft tissue neck CT scans were reviewed, and 142 radiomics features were derived. R was used to calculate Pearson correlation coefficients were calculated between gene expression levels and each radiomic feature. P values were adjusted using the false discovery rate (FDR) method. RESULTS: There were significant correlations between FGFR1 and 5 gray level cooccurrence matrix (GLCM) features with FDR-adjusted P values less than 0.05: inertia (r = 0.366, FDR-adjusted P = 0.006), absolute value (r = 0.31, FDR-adjusted P = 0.024), contrast (r = 0.366, FDR-adjusted P = 0.006), difference average (r = 0.31, FDR-adjusted P = 0.024), and difference variance (r = 0.37, FDR-adjusted P = 0.005). There was 1 correlated feature for FGFR2 with an FDR-adjusted P value less than 0.05: fractal dimension box-coarse (r = 0.33, FDR-adjusted P = 0.018). There was 1 correlated feature for EPHA2 with an FDR-adjusted P value less than 0.05: GLCM entropy (r = -0.28, FDR-adjusted P = 0.049). Six of the 7 features that showed significant correlation belonged to the GLCM class of features. CONCLUSIONS: The CT radiomic features demonstrate correlations with FGFR1 status in HNSCC and should be further investigated for their potential to predict FGFR1 status.

Normative measurements of parotid lymph nodes on CT imaging.

PURPOSE: The goal of this study is to characterize the normal size of parotid lymph nodes among healthy adult patients on CT. METHODS: This was a single-center retrospective observational study of 543 patients who underwent maxillofacial CT scans between January 2019 and July 2019. The long and short axis diameters of the largest lymph nodes in the bilateral superficial parotid glands were measured. RESULTS: Among the 543 patients, 407 subjects with a mean age of 47.0 ± 18.4 years had a total of 719 detectable intraparotid lymph nodes. The mean patient age was 47.0 ± 18.4 years. Of all 719 measured intraparotid lymph nodes, the measured long and short axis diameter means were 4.4 ± 1.4 mm and 3.3 ± 1.1 mm, respectively. In our study, 96% (689/719) of all lymph nodes had a long axis diameter of 7 mm or less and 93% (671/719) of all lymph nodes had a short axis diameter of 5 mm or less. Younger patients had significantly larger lymph nodes than older patients in both long axis (4.5 vs 4.3 mm; P = 0.03) and short axis (3.4 vs 3.1 mm, P = 0.01) measurements. CONCLUSION: Our findings suggest 5 mm as an upper limit of normal for the short axis diameter of superficial intraparotid lymph nodes.

Imaging Review of the Temporal Bone: Part II. Traumatic, Postoperative, and Noninflammatory Nonneoplastic Conditions.

The first part of this review of the temporal bone discussed anatomy of the temporal bone as well as inflammatory and neoplastic processes in the temporal bone region (1). This second part will first discuss trauma to the temporal bone and posttraumatic complications. The indications for common surgical procedures performed in the temporal bone and their postoperative imaging appearance are then presented. Finally, a few noninflammatory nonneoplastic entities involving the temporal bone are reviewed. They are relatively uncommon diagnoses compared with infectious or inflammatory diseases. However, because patients present with symptoms that are either common (hearing loss) or distinctive (sensorineural hearing loss in a child), they are important for the radiologist to be aware of and recognize.

CT and MRI of congenital nasal lesions in syndromic conditions.

Congenital malformations of the nose can be associated with a variety of syndromes, including solitary median maxillary central incisor syndrome, CHARGE syndrome, Bosma syndrome, median cleft face syndrome, PHACES association, Bartsocas-Papas syndrome, Binder syndrome, duplication of the pituitary gland-plus syndrome and syndromic craniosynsotosis (e.g., Apert and Crouzon syndromes) among other craniofacial syndromes. Imaging with CT and MRI plays an important role in characterizing the nasal anomalies as well as the associated brain and cerebrovascular lesions, which can be explained by the intimate developmental relationship between the face and intracranial structures, as well as certain gene mutations. These conditions have characteristic imaging findings, which are reviewed in this article.

Discriminating parathyroid adenoma from local mimics by using inherent tissue attenuation and vascular information obtained with four-dimensional CT: formulation of a multinomial logistic regression model.

PURPOSE: To identify a set of parameters, which are based on tissue enhancement and native iodine content obtained from a standardized triple-phase four-dimensional (4D) computed tomographic (CT) scan, that define a multinomial logistic regression model that discriminates between parathyroid adenoma (PTA) and thyroid nodules or lymph nodes. MATERIALS AND METHODS: Informed consent was waived by the institutional review board for this retrospective HIPAA-compliant study. Electronic medical records were reviewed for 102 patients with hyperparathyroidism who underwent triple-phase 4D CT and parathyroid surgery resulting in pathologically proved removal of adenoma from July 2010 through December 2011. Hounsfield units were measured in PTA, thyroid, lymph nodes, and aorta and were used to determine seven parameters characterizing tissue contrast enhancement. These were used as covariates in 10 multinomial logistic regression models. Three models with one covariate, four models with two covariates, and three models with three covariates were investigated. Receiver operating characteristic (ROC) analysis was performed to determine how well each model discriminated between adenoma and nonadenomatous tissues. Statistical differences between the areas under the ROC curves (AUCs) for each model pair were calculated, as well as sensitivity, specificity, accuracy, negative predictive value, and positive predictive value. RESULTS: A total of 120 lesions were found; 112 (93.3%) lesions were weighed, and mean and median weights were 589 and 335 mg, respectively. The three-covariate models were significantly identical (P > .65), with largest AUC of 0.9913 ± 0.0037 (standard error), accuracy of 96.9%, and sensitivity, specificity, negative predictive value, and positive predictive value of 94.3%, 98.3%, 97.1%, and 96.7%, respectively. The one- and two-covariate models were significantly less accurate (P < .043). CONCLUSION: A three-covariate multinomial logistic model derived from a triple-phase 4D CT scan can accurately provide the probability that tissue is PTA and performs significantly better than models using one or two covariates.

Imaging review of the temporal bone: part I. Anatomy and inflammatory and neoplastic processes.

From a clinical-radiologic standpoint, there are a limited number of structures and disease entities in the temporal bone with which one must be familiar in order to proficiently interpret a computed tomographic or magnetic resonance imaging study of the temporal bone. It is helpful to examine the region in an organized and systematic fashion, going through the same checklist of key structures each time. This is the first of a two-part review that provides a practical approach to understanding temporal bone anatomy, localizing a pathologic process with a focus on inflammatory and neoplastic processes, identifying pertinent positives and negatives, and formulating a differential diagnosis.

Imaging after direct and indirect extracranial-intracranial bypass surgery.

OBJECTIVE: The purpose of this article is to describe the imaging features of different types of surgical cerebral revascularization techniques. CONCLUSION: Surgical cerebral revascularization involves direct and indirect techniques. Direct revascularization entails anastomosing a branch of the external carotid artery to a cerebral artery. Indirect revascularization involves delivering an extracranial vascular supply in proximity to the surface of the brain. The results of these techniques have distinctive imaging features.

Nasal hamartoma associated with duplicated pituitary.

Nasal hamartomas are rare congenital lesions. We describe a case of nasal hamartoma associated with pituitary duplication and other midline anomalies. A 40-year-old female with a history of breast cancer presented with nasal obstruction. Computed tomography and magnetic resonance imaging revealed a mass arising from the nasal septum, as well as duplication of the pituitary and a skull base canal that extended from the margin of the left pituitary fossa to the nasal mass. The mass was subsequently resected via a transnasal endoscopic approach and histology confirmed the presence of hamartoma. Nasal hamartomas are benign lesions that can be associated with other midline anomalies, such as duplicated pituitary, and can be managed conservatively.

Radiographic patterns of orbital involvement in IgG4-related disease.

PURPOSE: Immunoglobin G4 (IgG4)-related disease is a systemic condition characterized by lymphoplasmacytic infiltrates that can involve the orbit. The purpose of this study was to identify the various patterns of orbital IgG4-related disease on imaging. METHODS: Retrospective review of radiologic examinations including CT, MRI, and positron emission tomography was performed in patients with proven cases of IgG4-related disease. RESULTS: A total of 9 patients with orbital IgG4-related disease were identified, including 9 with CT, 4 with MRI, and 4 with 18-fluorodeoxyglucose positron emission tomography. Patterns of involvement included lacrimal gland enlargement, lacrimal sac involvement, extraocular muscle thickening, preseptal involvement, orbital fat involvement, and cranial nerve involvement, many of which occurred simultaneously. Associated demineralization of the orbital wall was evident on CT in 2 cases. On T2-weighted MRI, the lesions appeared as hypointense in 2 cases, heterogeneously hypointense to isointense in 1 case, and hyperintense in 1 case. Diffuse enhancement was present in all 3 cases in which postcontrast T1-weighted sequences were available. The lesions were hypermetabolic on positron emission tomography in 3 of 4 cases. There was definite extraorbital involvement by IgG4-related disease in 3 of the 9 patients and suspected involvement in another 3 of the 9 patients. CONCLUSIONS: IgG4-related disease displays a wide variety of imaging manifestations in the orbit. Extraorbital disease is often present and can help suggest the diagnosis.

MRI radiomics and potential applications to glioblastoma.

MRI plays an important role in the evaluation of glioblastoma, both at initial diagnosis and follow up after treatment. Quantitative analysis via radiomics can augment the interpretation of MRI in terms of providing insights regarding the differential diagnosis, genotype, treatment response, and prognosis. The various MRI radiomic features of glioblastoma are reviewed in this article.

Advances in the Radiological Evaluation of and Theranostics for Glioblastoma.

Imaging is essential for evaluating patients with glioblastoma. Traditionally a multimodality undertaking, CT, including CT cerebral blood profusion, PET/CT with traditional fluorine-18 fluorodeoxyglucose (18F-FDG), and MRI have been the mainstays for diagnosis and post-therapeutic assessment. However, recent advances in these modalities, in league with the emerging fields of radiomics and theranostics, may prove helpful in improving diagnostic accuracy and treating the disease.

Diffusion-weighted imaging for differentiating benign from malignant skull lesions and correlation with cell density.

OBJECTIVE: The objective of our study was to determine the utility of diffusion-weighted imaging (DWI) and cell density for differentiating benign from malignant skull lesions. MATERIALS AND METHODS: A retrospective review was performed. Minimum apparent diffusion coefficient (ADC) values were measured and normalized to white matter, which we refer to as "normalized ADC," in 24 skull lesions (12 malignant and 12 benign) in 18 patients. In addition, cell densities were measured in 15 cases and correlated with ADC values. RESULTS: The average minimum ADC in malignant tumors was 0.70 × 10(-3) mm(2)/s versus 1.11 × 10(-3) mm(2)/s in benign tumors (p = 0.0037). Similarly, the average normalized ADC for malignant tumors was 1.03, whereas the average normalized ADC for benign tumors was 1.65 (p = 0.0012). Receiver operating characteristic curve analysis yielded optimal normalized ADC and ADC thresholds of 1.23 (accuracy, 84.6%; sensitivity, 75.0%; specificity, 92.3%) and 1.01 × 10(-3) mm(2)/s (accuracy, 83.7%; sensitivity, 83.3%; specificity, 84.6%), respectively. There was a significant inverse correlation between cell density and normalized ADC (r = -0.58; p = 0.023). The low cellularity in chordoma and low-grade chondrosarcoma and high cellularity in eosinophilic granuloma may explain the DWI features of these lesions. CONCLUSION: ADC values in skull lesions correlate with cell density and can potentially narrow the differential diagnoses for indeterminate skull lesions. Understanding the histopathologic features of skull lesions can refine interpretation of DWI.

Intracranial lesions with high signal intensity on T1-weighted MR images: differential diagnosis.

Various substances, including methemoglobin, melanin, lipid, protein, calcium, iron, copper, and manganese, are responsible for the intrinsically high signal intensity observed in intracranial lesions at T1-weighted magnetic resonance (MR) imaging. Many of these substances have physical properties that lead to other specific imaging features as well. For example, lipid-containing lesions frequently produce chemical shift artifact, and some melanin-containing lesions exhibit a combination of high signal intensity on T1-weighted images and low signal intensity on T2-weighted images. The location and extent of a region of abnormal signal hyperintensity may be helpful for identifying rare diseases such as an ectopic posterior pituitary gland near the floor of the third ventricle, bilateral involvement of the dentate and lentiform nuclei in Cockayne syndrome, and involvement of the anterior temporal lobe and cerebellum in neurocutaneous melanosis. In cases in which diagnostically specific T1-weighted imaging features are lacking, findings obtained with other MR pulse sequences and other modalities can help narrow the differential diagnosis: An elevated glutamine or glutamate level at MR spectroscopy is suggestive of hepatic encephalopathy; a popcorn ball-like appearance at T2-weighted imaging, of cavernous malformations; and hyperattenuation at computed tomography, of mineral deposition disease. In many cases, a comparison of imaging features with clinical measures enables a specific diagnosis.

Multimodality imaging of hydrogel scleral buckles.

BACKGROUND: Hydrogel scleral buckles were used for treating retinal detachment in the 1980s and early 1990 s. However, these devices have a propensity to degrade over time and cause several long-term complications, including hydration and overexpansion, fragmentation, extrusion, intrusion, and intraocular erosion, and the potential to mimic mass lesions. METHODS: The imaging features of hydrogel scleral buckles and their complications are reviewed in this article. RESULTS: Radiographic imaging plays an important role in managing patients with complications of hydrogel buckles. Hydrated buckles display attenuation intermediate between fluid and soft tissue on computed tomography, demonstrate approximately fluid signal on magnetic resonance imaging, and are anechoic on ultrasonography. Linear margins and peripheral dystrophic calcification are characteristic. CONCLUSION: The constellation of imaging features helps distinguish expanded hydrogel buckles from other orbital diseases. Imaging also serves to precisely localize hydrogel scleral buckle components requiring removal.

Postoperative imaging of vestibular schwannomas.

Symptomatic vestibular schwannomas can be treated with resection (translabyrinthine, retrosigmoid [suboccipital], or middle cranial fossa approaches) or stereotactic radiosurgery. When appropriate, auditory brainstem stimulators can also be implanted in patients with current or impending hearing loss due to bilateral vestibular schwannomas. Imaging plays a prominent role in determining management following these procedures. In this article, the expected postoperative imaging appearances are depicted. The radiological features of complications are also reviewed, including recurrent tumor, fat graft necrosis, CSF leakage, infection, hydrocephalus, cerebral infarction, venous sinus thrombosis, hemorrhage, and temporal lobe and cerebellar contusions.

Implants and Foreign Bodies on Head and Neck Imaging.

A wide variety of foreign bodies can be encountered on head and neck imaging. These foreign bodies might include comestible foreign bodies, retained foreign bodies from trauma, and surgically implanted devices. The imaging features of these items are reviewed in this article.

Imaging of the Postoperative Eye and Orbit.

There is a plethora of surgical procedures that are performed in the eye and orbit. The consequences of these procedures can often be observed on diagnostic imaging through the presence of various implants and altered anatomy. The expected postoperative changes in the eye and orbit, the impact of implants on image quality and safety, and potential associated complications are reviewed in this article. Conventional computed tomography and MR imaging scans are useful for the postoperative assessment of the eye and orbit. The computed tomography and MR imaging findings related to the postoperative eye and orbit are reviewed in this article.

Postsurgical and Postradiation Findings in the Head and Neck Imaging.

Surgical procedures and radiation therapy can have recognizable features on diagnostic imaging that should be recognized by the radiologist. Although it is a good practice to reference the surgical and clinical notes regarding any procedures that may have been performed in the head and neck, this information is not always available. Selected examples of posttreatment findings and potential mimics are described and depicted in the following sections.