The Current State of Susceptibility-Weighted Imaging and Quantitative Susceptibility Mapping in Head Trauma.

Susceptibility-weighted imaging (SWI) is a MR imaging technique suited to detect structural and microstructural abnormalities in traumatic brain injury (TBI). This review article provide an insight in to the physics principles of SWI and its clinical application in unraveling the complex interaction of the biophysical mechanisms of head injury. Literature evidences support SWI as the most ideal sequence in detection of microbleeds, which is the "tip of the iceberg" biomarker of microvascular injuries. The review also detailed the emerging advance techniques of Quantitative susceptibility mapping (QSM) and artificial intelligence offer the ability to detect and follow the evolution of microbleeds in patient with chronic TBI. These new techniques offers a unique insight into the acute and chronic state of TBI.

Meta-analysis assessing the sensitivity and specificity of 18F-FDG PET/CT for the diagnosis of prosthetic valve endocarditis (PVE) using individual patient data (IPD).

IMPORTANCE: The use of 18F-FDG PET/CT in diagnostic algorithms for PVE has increased since publication of studies and guidelines advocating its use. The assessment of test accuracy has been limited by small study sizes. We undertook a systematic review using individual patient data (IPD) meta-analysis techniques. OBJECTIVE: To estimate the summary sensitivity and specificity of 18F-FDG PET/CT in diagnosing PVE. We also assessed the effect of patient factors on test accuracy as defined by changes in the odds ratios associated with each factor. The effect of the PET/CT study on the final diagnosis was also assessed when compared to the preliminary Duke classification to determine in which patient group 18F-FDG PET/CT had the greatest utility. STUDY SELECTION: Studies were included if PET/CT was performed for suspicion of PVE and IPD of both the PET/CT result and final diagnosis defined by a gold-standard assessment was available. There were 3 possible final diagnoses ("definite PVE," "possible PVE," and "rejected PVE"). RESULTS: Seventeen studies were included with IPD available for 537 patients (from 538 scans). The summary sensitivity and specificity were 85% (95% CI 74.2%-91.8%) and 86.5% (95% CI 75.8%-92.9%) respectively when patients with final diagnosis of "possible PVE" were classified as positive for PVE. When this group was classified as negative for PVE, sensitivity was 87.4% (95% CI 80.4%-92.1%) and specificity was 84.9% (95% CI 71.5%-92.6%). Patients with a known pathogen (especially coagulase negative staphylococcal species), elevated CRP, a biological or aortic valve infection appeared more likely to have an accurate PET/CT diagnosis. Those with a mechanical valve, prior antibiotic treatment or a transcatheter aortic valve replacement valve were less likely to have an accurate test. Time since valve implantation and the presence of surgical adhesive did not appear to affect test accuracy. Of the patients with a preliminary Duke classification of "possible PVE," 84% received a more conclusive final diagnosis of "definite" or "rejected" PVE after the PET/CT study. CONCLUSIONS AND RELEVANCE: 18F-FDG PET/CT has high sensitivity and specificity in diagnosing PVE and the diagnostic utility is greatest in patients with a preliminary Duke classification of "possible PVE." Some patient factors appear to affect test accuracy, though these results should be interpreted with caution given low patient numbers for subgroup analyses.

Yellow droopy eyes: A case of obstructive jaundice from Burkitt's lymphoma with involvement of bilateral cavernous sinus.

Burkitt's lymphoma follows a lymphogenous spread early in the disease. The central nervous system can be involved via a hematogenous route but involvement of the cavernous sinus (CS) is rare and can be misdiagnosed as other pathology of primary neoplastic, infective, or vascular origin. We present a case of a 73-year-old gentleman with painless jaundice and subjective heaviness to his eyes that progressed to partial ptosis of the left eye, complete ptosis of the right eye with diplopia, found to have disseminated Burkitt's lymphoma with bilateral deposits to the CS. Early recognition of Burkitt's lymphoma with CS involvement is important as it often signifies disseminated disease with implications on chemotherapy regimen, treatment outcomes, and survival.

Susceptibility weighted imaging for qualitative grading of persistent arteriovenous shunting in deep-seated arteriovenous malformations after stereotactic radiation surgery.

BACKGROUND AND PURPOSE: To investigate Susceptibility Weighted Imaging (SWI) signal changes in the draining vein of deep-seated arterio-venous malformations (AVMs) following stereotactic radiosurgery (SRS). METHODS AND MATERIALS: This is a retrospective study of 32 patients with deep-seated AVMs who were treated with SRS. Pre-SRS treatment and post-SRS treatment MRI were performed at 6, 12, and 24-month intervals. Deep-seated AVMs were classified based on their anatomical location and venous drainage pattern. AVM nidal volume (cm3) was estimated using the ABC/2 method. AV shunting of the AVM draining veins were graded according to its SWI signal intensity: hyperintense (grade III), mixed signal intensity (grade II), hypointense (grade I) and absent (grade 0). Conventional time-of-flight (TOF)-MRA and contrast enhanced (CE)-MRA sequences were performed to document the patency of the vein. RESULTS: Pre-SRS treatment AVM draining veins were either grade III 18/32 (56%) or grade II 14/32 (44%). Using mixed effects analysis, we demonstrate that each month following the SRS treatment nidal volumes decreased at the rate of 0.51 cm3/per month (CI -0.61 to (-0.40)) p =.00. Following the treatment, there was a clinically significant relationship between the signal and nidal volume: signal 0 corresponded with average nidal volume of 1.81 cm3 (CI 1.40-2.21), signal 1 with nidal volume of 2.06 cm3 (CI 1.69-2.44), signal 2 with nidal volume 2.73 cm3 (CI 2.35-3.11) and signal 3 with nidal volume 3.13 cm3 (CI 2.70-3.56) p = .00. CONCLUSION: Post-SRS AVM draining veins shows a stepwise regression of the SWI signal grades which can be reliably used as a surrogate to monitor the reduction of AV shunting.

18F-FDG PET/CT in Osteoradionecrosis of the Hyoid.

Osteoradionecrosis (ORN) is a well-documented complication following radiation treatment for head and neck malignancy. Facial bones, mainly the mandible, laryngeal cartilage, and skull, are frequently involved sites for ORN. A rare site for ORN is the hyoid, with very limited cases described in the literature. Recognition of the imaging pattern of hyoid ORN is critical to avoid misdiagnosis of recurrent disease, prompting early treatment.

Susceptibility and Volume Measures of the Mammillary Bodies Between Mild Cognitively Impaired Patients and Healthy Controls.

PURPOSE: To investigate the baseline values and differences for susceptibility and volume of the mammillary bodies between mild cognitively impaired (MCI) patients and healthy controls (HCs), and further explore their differences in relation to gender, MCI subtypes and apolipoprotein E (APOE) genotypes. METHODS: T1-weighted and multi-echo gradient echo imaging sequences were acquired on a 3T MR scanner to evaluate the T1W based volume and susceptibility differences in the mammillary body for 47 MCI and 47 HCs. T-tests were performed to compare volume and susceptibility between groups, and right and left hemispheres. Correlation analysis was used to relate the volume and mean susceptibility as a function of age in MCI and HC groups separately, and to investigate the relationship of susceptibility with the neuro-psychological scales in the MCI group. RESULTS: Susceptibility was found to be elevated within the right mammillary body in MCI patients compared to HCs (p < 0.05). There were no differences for the mammillary body volumes between the MCI and HC groups, although there was a reduction in volume with age for the MCI group (p = 0.007). Women showed decreased mammillary body volume compared to men in the HC group (p = 0.004). No significant differences were found in relation to MCI subtypes and APOE genotypes. No significant correlations were observed between mammillary body susceptibility with neuro-psychological scales. CONCLUSION: This work provides a quantitative baseline for both the volume and susceptibility of the mammillary body which can be used for future studies of cognitive impairment patients underlying the pathology of the Papez circuit.

Developmental anomalies of the lateral portion of the cervical neural arch: Multimodal imaging and clinical implications.

OBJECTIVE: This study aimed to describe the imaging spectrum of developmental anomalies of the lateral portion of the cervical neural arch. METHOD: This was a five-year retrospective review of consecutive computed tomography (CT) scans of the cervical spine for structural anomalies of the cervical vertebral pedicle and facets. CT, radiographs and, when available, magnetic resonance imaging studies were independently reviewed. Anomalies were grouped into the following three categories: the absence of a pedicle, clefts in the vertebral arch or isolated dysmorphism of the facet. Clinical data on demographics and neurological outcomes were documented. RESULTS: Among 9134 consecutive patients undergoing a CT scan of the cervical spine, 18 (0.2%) patients were found to have developmental anomalies of the pedicle and facets. Findings included 7/18 (39%) with congenital absence of a pedicle, 8/18 (44%) with clefts in the vertebral arch and 3/18 (17%) with isolated dysmorphism of the articular facets. No acute neurological deficits or spinal cord injuries were reported. Associated chronic symptoms included neck pain 10/18 (56%), radiculopathy 7/18 (39%) and myelopathy 1/18 (6%). CONCLUSION: Developmental anomalies of the pedicle and facet may mimic traumatic spinal pathologies. Recognising a diverse spectrum of imaging findings is vital to prevent misdiagnosis and unnecessary intervention.

Quantitative Susceptibility Mapping for Characterization of Intraplaque Hemorrhage and Calcification in Carotid Atherosclerotic Disease.

BACKGROUND: Carotid artery intraplaque hemorrhage (IPH), an unstable component of atherosclerosis, is associated with an increased risk of stroke. PURPOSE: To investigate quantitative susceptibility mapping (QSM) as a tool for the evaluation of IPH and calcification in vivo. STUDY TYPE: Prospective. POPULATION: Ten healthy volunteers and 15 patients. FIELD STRENGTH/SEQUENCE: 3.0T Susceptibility-weighted imaging (SWI), magnetization-prepared rapid acquisition with gradient echo (MP-RAGE), T1 -weighted sampling perfection with application of optimized contrasts using different flip angle evolution (T1 -SPACE), T2 -weighted turbo spin-echo (T2 WI), and time-of-flight (TOF) sequences. ASSESSMENT: The vessel wall area of the carotid artery was measured with QSM and compared with T1 -SPACE on healthy volunteers. Four radiologists, blinded to clinical history and patient identity, determined the presence and area of IPH on MP-RAGE and QSM, as well as the area of calcification on T1 -SPACE and QSM. STATISTICAL TESTS: Bland-Altman analysis, Pearson correlation coefficients, linear regression analyses were performed to evaluate the concordance of area measurements. Cohen's kappa (κ) was analyzed to determine the agreement between IPH detections. The paired t-test was used to compare the group differences. RESULTS: In 423 matched slices, 20.1% (85/423) and 19.6% (83/423) were detected to have IPH on MP-RAGE and QSM, respectively. IPH detection by QSM and MP-RAGE showed good agreement (κ = 0.822, P < 0.001) between the two methods. There was no significant difference in IPH area measurements between QSM and MP-RAGE (7.28 mm2 ± 6.41 vs. 7.16 mm2 ± 5.99, P = 0.575). There was no significant difference in calcification area measurement between QSM and T1 -SPACE (3.51 mm2 ± 1.78 vs. 3.41 mm2 ± 2.02, P = 0.783). DATA CONCLUSION: QSM is a novel imaging tool for the identification of IPH in patients with carotid atherosclerosis and enables differentiation of IPH and calcification. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 1 J. Magn. Reson. Imaging 2020;52:534-541.

Magnetic Resonance Imaging Criteria for Post-Concussion Syndrome: A Study of 127 Post-Concussion Syndrome Patients.

The purpose of this study was to assess the frequency of structural lesions on conventional magnetic resonance imaging (MRI) of the brain in a large prospective cohort of post-concussion syndrome (PCS) patients. Conventional 3T MRI was used to evaluate 127 prospectively enrolled PCS patients and 29 controls for non-specific white matter hyperintensities (WMH) and traumatic structural lesions, including encephalomalacia, atrophy, microhemorrhage, subarachnoid hemorrhage, and cortical siderosis. All PCS patients had a clinical diagnosis of one or more concussions based on the Concussion in Sport Group (CISG) consensus statements. Patients with recognized intracranial hemorrhage on prior head computed tomography (CT) and MRI were excluded. The differences between the PCS and control groups were analyzed. Four patients in the PCS group (3.1%) had positive findings, which included microhemorrhages in two patients and encephalomalacia in another two patients. None of these lesions was present in the control group, but there was no statistical difference between the two groups (p = 0.5 for microhemorrhage and p = 0.5 for encephalomalacia). In the PCS group, 28 patients (22%) had WMH (15.7% had 1-10 lesions and 6.3% had >10 lesions), and these results did not differ from the age-matched control (20.6%, all with 1-10 lesions; p = 0.9) The location of the WMH showed no significant difference in the number of juxtacortical WMH between the PCS and control groups (p = 0.5). Structural lesions were rare in PCS in this study, and the presence of such findings suggests a more severe form of traumatic brain injury. Our data support the role for MRI in the diagnosis of PCS by exclusion of atrophy, encephalomalacia, and all forms of intracranial hemorrhage. The presence of WMH irrespective of number is not an exclusion. This is the first description of the MRI criteria for PCS.

High-Resolution MRI Vessel Wall Imaging in Acute Aneurysmal Subarachnoid Hemorrhage : Spatiotemporal Pattern and Clinicoradiologic Implications.

PURPOSE: The spatiotemporal pattern of vessel wall changes was investigated on two time point magnetic resonance images (MRI) in patients with aneurysmal subarachnoid hemorrhages (aSAH) and its association with clinicoradiologic severity score and delayed cerebral ischemia (DCI) was analyzed. METHODS: A total of 32 prospectively enrolled patients with aSAH (mean age 56.94 years; 9 male and 23 female) underwent vessel wall imaging (VWI) MRI. Of the patients 20 completed two time point MRIs early and late during the admission, 10 patients only had early MRI and 2 patients only had late MRI. Timing of early MRI had a mean of 2.5 days (range 1-6 days) and late MRI had a mean of 10.5 days (range 7-16 days) from time of admission. Spatiotemporal pattern of vessel wall enhancement (VWE), vasospasm, diffusion-weighted imaging (DWI) lesion burden (grade 0-III) and infarcts were analyzed against the clinicoradiologic severity score (high-risk: vasograde red and yellow, low-risk: vasograde green) and DCI. RESULTS: On the early MRI, mild VWE alone was significantly more frequent in the high-risk group (36.7% versus 20.0%; P = 0.024). On the late MRI, vasospasm was significantly more frequent in the high-risk group (27.2% versus 4.5%; P = 0.022). Vasospasm infrequently showed mild VWE (6.67% on early MRI and 9.09% on late MRI). Both mild VWE alone on early MRI and on late MRI were significantly associated with development of DCI during the admission (P = 0.034 and P = 0.035, respectively). CONCLUSION: Mild VWE on early MRI and vasospasm on late MRI were significantly more prevalent in high-risk and DCI patients suggesting VWI might enable imaging of early neuroinflammatory changes which are part of the pathomechanism of vasospasm and DCI.

Iodine-stained fragmented thromboembolism.

AIM: Iodine-stained fragmented thromboembolism (ISFT) is a rare phenomenon encountered in the immediate aftermath of mechanical thrombectomy or rarely as a complication of post-carotid stenting. The aim was to describe the imaging appearance and discuss its pathophysiology. METHOD: This is a retrospective review of patients who underwent mechanical thrombectomy for acute stroke at a single institution over the period of one year. All patients underwent the standard acute stroke imaging protocol (CT head, CT angiogram (CTA) and CT brain perfusion) and when clinically appropriate followed by catheter angiogram and mechanical thrombectomy. ISFT was defined as an arterial luminal filling defect with Hounsfield density equal to or greater than iodine seen on the biplanar CT or conventional CT. The presence and location of ISFT were documented. Standard CT angiogram (CTA) or magnetic resonance angiogram (MRA) was performed 24-48 hours after the neurointerventional procedure to assess for recanalization, volume of infarction and the fate of the ISFT. RESULTS: ISFTs were identified in eight (five males and three females, age range 18-80 years) out of 49 patients in the following locations: distal M1 (n = 1), M2 (n = 4), M3 (n = 1), A1 (n = 1), distal A2 (n = 1). ISFT and vessel recanalization occurred in five patients on follow-up. ISFT and vessel occlusion persisted in two patients. CONCLUSION: ISFT is likely the result of mechanical disruption of a thromboembolus, and porosity of the thromboembolus fragment may transiently retain iodinated contrast. Recognition of this entity may be important to aid detection of residual thromboembolism and avoid misinterpretation as calcified thromboembolism.

High resolution magnetic resonance imaging for exposing facial nerve zonal vulnerability to microbleeds: A rare cause of facial palsy.

Background We report a case of hypertensive microbleeds strategically located at the attached segment (AS) and root entry zone (REZ) at the left facial nerve causing facial paralysis. Case Report A 60-year-old woman presented with sudden onset left facial paralysis. Medical history was significant for poorly controlled hypertension secondary to bilateral adrenal hyperplasia (primary hyperaldosteronism). The patient was initially treated for presumptive Bell's palsy. Subsequent magnetic resonance imaging of the brain and internal auditory canal showed two microbleeds at the left cerebellopontine angle. Dedicated coronal T1 magnetization prepared rapid acquisition gradient echo and T2 sampling perfection with application optimized contrasts using different flip angle evolution sequences revealed two acute microbleeds located at the attached AS and REZ of the left facial nerve. The patient experienced only partial recovery from House-Brackmann grade IV facial paralysis at presentation to a House-Brackmann grade III facial paralysis at 1 year of follow up. Conclusions To the best of the authors' knowledge, this is the first reported case of facial paralysis caused by microbleeds directly affecting the vulnerable AS and REZ facial nerve segments. We discuss the zonal microanatomy of the facial nerve and the crucial role of high resolution MRI for diagnosis.

Susceptibility weighted imaging in acute cerebral ischemia: review of emerging technical concepts and clinical applications.

Susceptibility weighted imaging (SWI) is an essential magnetic resonance imaging sequence in the assessment of acute ischemic stroke. In this article, we discuss the physics principals and clinical application of conventional SWI and multi-echo SWI sequences. We review the research evidence and practical approach of SWI in acute ischemic stroke by focusing on the detection and characterization of thromboembolism in the cerebral circulation. In addition, we discuss the role of SWI in the assessment of neuroparenchyma by depiction of asymmetric hypointense cortical veins in the ischemic territory (surrogate tissue perfusion), detection of existing microbleeds before stroke treatment and monitoring for hemorrhagic transformation post-treatment. In conclusion, the SWI sequence complements other parameters in the stroke magnetic resonance imaging protocol and understanding of the research evidence is vital for practising stroke neurologists and neuroradiologists.