Topics in Magnetic Resonance Imaging最新文献

Objectives: Magnetic resonance imaging (MRI) is increasingly used in postmortem fetal imaging. Several factors influence the quality of MRI in this setting, such as small size, autolytic and maceration changes, and temperature. Knowing the fetal temperature at the time of scanning can improve the MRI interpretation. Temperature can be calculated using diffusion-weighted imaging with measurements of the apparent diffusion coefficient (ADC) in the cerebrospinal fluid (CSF). However, this is complicated by small ventricle size and hemorrhage and, therefore, may be unreliable in postmortem imaging. The current study evaluated the feasibility and reliability of using the ADC for temperature measurements of the vitreous body compared to that of CSF.

Materials and methods: Two lambs were scanned postmortem at five different time points over 28 hours. Furthermore, 10 stillborn fetuses were scanned once, at 4 to 62 hours after birth. The temperature was measured with a digital thermometer and calculated using the ADCs of the vitreous body (lambs and fetuses) and CSF (fetuses).

Results: There was an excellent correlation between measured and calculated temperatures in vitreous bodies of lambs (r = 0.997, P < 0.001) and fetuses (r = 0.970, P < 0.001). The correlation between measured and calculated temperatures in the CSF was poor (r = 0.522, P = 0.122).

Conclusion: The calculation of the temperature based on the ADC of the vitreous body is feasible and reliable for postmortem fetal imaging.

Background: Magnetic resonance elastography (MRE) allows noninvasive assessment of intracranial tumor mechanics and may thus be predictive of intraoperative conditions. Variations in the use of technical terms complicate reading of current literature, and there is need of a review using consolidated nomenclature.

Objectives: We present an overview of current literature on MRE relating to human intracranial neoplasms using standardized nomenclature suggested by the MRE guidelines committee. We then discuss the implications of the findings, and suggest approaches for future research.

Method: We performed a systematic literature search in PubMed, Embase, and Web of Science; the articles were screened for relevance and then subjected to full text review. Technical terms were consolidated.

Results: We identified 12 studies on MRE in patients with intracranial tumors, including meningiomas, glial tumors including glioblastomas, vestibular schwannomas, hemangiopericytoma, central nervous system lymphoma, pituitary macroadenomas, and brain metastases. The studies had varying objectives that included prediction of intraoperative consistency, histological separation, prediction of adhesiveness, and exploration of the mechanobiology of tumor invasiveness and malignancy. The technical terms were translated using standardized nomenclature. The literature was highly heterogeneous in terms of image acquisition techniques, post-processing, and study design and was generally limited by small and variable cohorts.

Conclusions: MRE shows potential in predicting tumor consistency, adhesion, and mechanical homogeneity. Furthermore, MRE provides insight into malignant tumor behavior and its relation to tissue mechanics. MRE is still at a preclinical stage, but technical advances, improved understanding of soft tissue rheological impact, and larger samples are likely to enable future clinical introduction.

Abstract: Numerous factors make the initial diagnostic evaluation of children with suspected arterial ischemic stroke (AIS) a relatively unsettling challenge, even for the experienced stroke specialist. The low frequency of pediatric AIS, diversity of unique age-oriented stroke phenotypes, and unconventional approaches required for diagnosis and treatment all contribute difficulty to the process. This review aims to outline important features that differentiate pediatric AIS from adult AIS and provide practical strategies that will assist the stroke specialist with diagnostic decision making in the initial phase of care.

Background and purpose: The diagnosis of childhood arteriopathy is complex. We present a Web-based, evidence-backed classification system to return the most likely cause(s) of a pediatric arterial ischemic stroke. This tool incorporates a decision-making algorithm that considers a patient's clinical and imaging features before returning a differential diagnosis, including the likelihood of various arteriopathy subtypes.

Methods: The Vascular Effects of Infection in Pediatric Stroke study prospectively enrolled 355 children with arterial ischemic stroke (2010-2014). Previously, a central panel of experts classified the stroke etiology. To create this tool, we used the 174 patients with definite arteriopathy and spontaneous cardioembolic stroke as the "derivation cohort" and the 34 with "possible" arteriopathy as the "test cohort." Using logistic regression models of clinical and imaging characteristics associated with each arteriopathy subtype in the derivation cohort, we built a decision framework that we integrated into a Web interface specifically designed to create a probabilistic differential diagnosis. We applied the Web-based tool to the "test cohort."

Results: The differential diagnosis returned by our tool was in complete agreement with the experts' opinions in 20.6% of patients. We observed a partial agreement in 41.2% of patients and an overlap in 29.4% of patients. The tool disagreed with the experts on the diagnoses of 3 patients (8.8%).

Conclusions: Our tool yielded an overlapping differential diagnosis in most patients that defied definitive classification by experts. Although it needs to be validated in an independent cohort, it helps facilitate high-quality, and timely diagnoses of arteriopathy in pediatric patients.

Abstract: Cerebral perfusion imaging provides useful information about the hemodynamic state of the brain that is relevant to a number of neurologic conditions, including stroke, epilepsy, and brain tumors. Multiple imaging modalities have been developed to evaluate brain perfusion, primarily by the use of different tracers to measure cerebral blood volume and cerebral blood flow. Here, we provide an overview of magnetic resonance imaging perfusion techniques; summarize the role of perfusion imaging in adult stroke; describe changes in cerebral blood flow over childhood; and discuss the relevance and future directions of perfusion imaging in pediatric cerebrovascular disorders and stroke.

Abstract: Modern hyperacute reperfusion therapies including intravenous thrombolysis and mechanical thrombectomy have transformed the management of arterial ischemic stroke (AIS) in adults. Multiple randomized clinical trials have demonstrated that these therapies enable remarkable improvements in clinical outcome for properly selected patients with AIS. Because pediatric patients were excluded from predicate clinical trials, there is a conspicuous lack of data to guide selection of therapies and inform age-adjusted and pathology-oriented treatment modifications for children. Specifically, technical guidance concerning treatment eligibility, drug dosing, and device implementation is lacking. This review aims to outline important features that differentiate pediatric AIS from adult AIS and provide practical strategies that will assist the stroke specialist with therapeutic decision making.