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2.
Radiol Med ; 125(11): 1148-1166, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32948928

RESUMO

Aortic valve stenosis (AS) is a common valvular heart disease. Recently, transcatheter aortic valve implantation (TAVI) has changed the treatment of severe AS in elderly patients with contraindications to traditional surgical replacement. Echocardiography is conventionally used as the first imaging modality to assess the presence and severity of AS and to provide anatomical and functional information. Nowadays, imaging techniques play a crucial role in the planning of TAVI to define suitable candidates. Computed tomography (CT) is essential to display the anatomy of the aortic valve complex (including aortic annulus, Valsalva sinuses, coronary arteries ostia, sinotubular junction), thoracoabdominal aorta, and vascular access. Cardiac CT may also provide the evaluation of coronary arteries in alternative to conventional coronary angiography. Magnetic resonance imaging may be alternative or supplementary in selected cases, providing detailed information of cardiac function and myocardial wall characteristics. More recently, advanced computer modeling image-based techniques can be used to support the evaluation of the feasibility and safety of TAVI procedures.


Assuntos
Estenose da Valva Aórtica/cirurgia , Tomografia Computadorizada por Raios X/métodos , Substituição da Valva Aórtica Transcateter/métodos , Idoso , Estenose da Valva Aórtica/diagnóstico por imagem , Angiografia Coronária , Ecocardiografia , Humanos , Achados Incidentais , Imageamento por Ressonância Magnética/tendências
3.
Br J Radiol ; 93(1115): 20200562, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32822545

RESUMO

Whole-body MRI (WB-MRI) has evolved since its first introduction in the 1970s as an imaging technique to detect and survey disease across multiple sites and organ systems in the body. The development of diffusion-weighted MRI (DWI) has added a new dimension to the implementation of WB-MRI on modern scanners, offering excellent lesion-to-background contrast, while achieving acceptable spatial resolution to detect focal lesions 5 to 10 mm in size. MRI hardware and software advances have reduced acquisition times, with studies taking 40-50 min to complete.The rising awareness of medical radiation exposure coupled with the advantages of MRI has resulted in increased utilization of WB-MRI in oncology, paediatrics, rheumatological and musculoskeletal conditions and more recently in population screening. There is recognition that WB-MRI can be used to track disease evolution and monitor response heterogeneity in patients with cancer. There are also opportunities to combine WB-MRI with molecular imaging on PET-MRI systems to harness the strengths of hybrid imaging. The advent of artificial intelligence and machine learning will shorten image acquisition times and image analyses, making the technique more competitive against other imaging technologies.


Assuntos
Predisposição Genética para Doença , Imageamento por Ressonância Magnética/métodos , Neoplasias/diagnóstico por imagem , Imagem Corporal Total/métodos , Imagem de Difusão por Ressonância Magnética/tendências , Feminino , História do Século XXI , Humanos , Achados Incidentais , Imageamento por Ressonância Magnética/tendências , Masculino , Imagem Multimodal/métodos , Neoplasias/genética , Tomografia por Emissão de Pósitrons/métodos , Exposição à Radiação/prevenção & controle , Fatores de Tempo
4.
Br J Radiol ; 93(1115): 20200514, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32795180

RESUMO

Takotsubo cardiomyopathy (TC) is a reversible condition in which there is transient left ventricular (LV) dysfunction characterised most commonly by basal hyperkinesis and mid-apical LV ballooning and hypokinesia. It is said to be triggered by stress and mimics, such as acute coronary syndrome (ACS) clinically. Diagnosis is usually suspected on echocardiography due to the characteristic contraction pattern in a patient with symptoms and signs of ACS but normal coronary arteries on catheter angiography. Cardiac magnetic resonance (CMR), with its latest advancements, is the diagnostic modality of choice for diagnosis, prognosis and follow-up of patients. The advances in CMR (including T1, T2, ECV mapping and threshold-based late gadolinium enhancement (LGE) measurements have revolutionised the role of CMR in tissue characterisation and prognostication in patients with TC. In this review, we highlight the current role of CMR in management of TC and enumerate the CMR findings in TC as well the current advances in the field of CMR, which could help in prognosticating these patients.


Assuntos
Algoritmos , Imageamento por Ressonância Magnética/métodos , Cardiomiopatia de Takotsubo/diagnóstico por imagem , Circulação Coronária , Edema Cardíaco/diagnóstico por imagem , Fibrose/diagnóstico por imagem , Gadolínio , Humanos , Aumento da Imagem/métodos , Imageamento por Ressonância Magnética/tendências , Imagem Cinética por Ressonância Magnética , Contração Miocárdica , Miocárdio/patologia , Cardiomiopatia de Takotsubo/etiologia , Cardiomiopatia de Takotsubo/fisiopatologia
5.
J Headache Pain ; 21(1): 93, 2020 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-32723299

RESUMO

BACKGROUND: Post-traumatic headache (PTH) is one of the most frequent symptoms following mild traumatic brain injury (mTBI). Neuroimaging studies implicate hypothalamic function connectivity (FC) disruption as an important factor in pain disorders. However, it is unknown whether there are alterations in the hypothalamus-based resting state FC within PTH following mTBI at the acute stage and its relationship with headache symptom measurement. METHODS: Forty-four mTBI patients with PTH, 27 mTBI patients without PTH and 43 healthy controls who were well matched for age, gender, and years of education were enrolled in this study. All participants underwent resting-state functional magnetic resonance imaging (fMRI) scanning as well as headache symptom measurement and cognitive assessment. Hypothalamic resting state networks were characterized by using a standard seed-based whole-brain correlation method. The bilateral hypothalamic FC was compared among the three groups. Furthermore, the correlations between hypothalamic resting state networks and headache frequency, headache intensity and MoCA scores was investigated in mTBI patients with PTH using Pearson rank correlation. RESULTS: Compared with mTBI patients without PTH, mTBI patients with PTH at the acute stage presented significantly decreased left hypothalamus-based FC with the right middle frontal gyrus (MFG) and right medial superior frontal gyrus (mSFG), and significantly decreased right hypothalamus-based FC with the right MFG. Decreased FC of the right MFG was significantly positively associated with headache frequency and headache intensity (r = 0.339, p = 0.024; r = 0.408, p = 0.006, respectively). Decreased FC of the right mSFG was significantly positively associated with headache frequency and headache intensity (r = 0.740, p < 0.0001; r = 0.655, p < 0.0001, respectively). CONCLUSION: Our data provided evidence of disrupted hypothalamic FC in patients with acute mTBI with PTH, while abnormal FC significantly correlated with headache symptom measurement. Taken together, these changes may play an essential role in the neuropathological mechanism of mTBI patients with PTH.


Assuntos
Concussão Encefálica/diagnóstico por imagem , Hipotálamo/diagnóstico por imagem , Rede Nervosa/diagnóstico por imagem , Cefaleia Pós-Traumática/diagnóstico por imagem , Adulto , Concussão Encefálica/epidemiologia , Concussão Encefálica/fisiopatologia , Estudos Transversais , Feminino , Seguimentos , Humanos , Hipotálamo/fisiopatologia , Imageamento por Ressonância Magnética/métodos , Imageamento por Ressonância Magnética/tendências , Masculino , Pessoa de Meia-Idade , Rede Nervosa/fisiopatologia , Cefaleia Pós-Traumática/epidemiologia , Cefaleia Pós-Traumática/fisiopatologia , Estudos Prospectivos
6.
Neurology ; 95(11): e1528-e1537, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32641526

RESUMO

OBJECTIVE: The disconnectivity hypothesis postulates that partial loss of connecting white matter fibers between brain regions contributes to the development of dementia. Using diffusion MRI to quantify global and tract-specific white matter microstructural integrity, we tested this hypothesis in a longitudinal population-based study. METHODS: Global and tract-specific fractional anisotropy (FA) and mean diffusivity (MD) were obtained in 4,415 people without dementia (mean age 63.9 years, 55.0% women) from the prospective population-based Rotterdam Study with brain MRI between 2005 and 2011. We modeled the association of these diffusion measures with risk of dementia (follow-up until 2016) and with changes on repeated cognitive assessment after on average 5.4 years, adjusting for age, sex, education, macrostructural MRI markers, depressive symptoms, cardiovascular risk factors, and APOE genotype. RESULTS: During a median follow-up of 6.8 years, 101 participants had incident dementia, of whom 83 had clinical Alzheimer disease (AD). Lower global values of FA and higher values of MD were associated with an increased risk of dementia (adjusted hazard ratio [95% confidence interval (CI)] per SD increase for MD 1.79 [1.44-2.23] and FA 0.65 [0.52-0.80]). Similarly, lower global values of FA and higher values of MD related to more cognitive decline in people without dementia (difference in global cognition per SD increase in MD [95% CI] was -0.04 [-0.07 to -0.01]). Associations were most profound in the projection, association, and limbic system tracts. CONCLUSIONS: Structural disconnectivity is associated with an increased risk of dementia and more pronounced cognitive decline in the general population.


Assuntos
Encéfalo/diagnóstico por imagem , Demência/diagnóstico por imagem , Demência/epidemiologia , Rede Nervosa/diagnóstico por imagem , Vigilância da População , Idoso , Feminino , Seguimentos , Humanos , Estudos Longitudinais , Imageamento por Ressonância Magnética/tendências , Masculino , Pessoa de Meia-Idade , Países Baixos/epidemiologia , Vigilância da População/métodos , Fatores de Risco
7.
Stroke ; 51(8): 2495-2504, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32646333

RESUMO

BACKGROUND AND PURPOSE: Luminal imaging (degree of stenosis) currently serves as the gold standard to predict stroke recurrence and guide therapeutic strategies in patients with intracranial large artery diseases (ILADs). We comparatively evaluated the importance of vessel wall and luminal changes in predicting stroke occurrence. METHODS: Consecutive patients with ILAD in the proximal middle cerebral artery or distal internal carotid artery without proximal sources of embolism from the carotid and heart underwent time-of-flight magnetic resonance angiography, high-resolution magnetic resonance imaging, and the ring finger protein 213 (RNF213) gene variant test. Patients were followed up for >3 months. RESULTS: Of the 675 patients, 241 (35.7%) had atherosclerotic ILAD and 434 (64.3%) showed nonatherosclerotic ILAD (315 [46.7%] moyamoya disease cases and 119 [17.6%] dissection cases). The RNF213 variant was detected in 74.9%, 33.6%, and 3.4% patients with moyamoya disease, atherosclerosis, and dissection, respectively. Three hundred (44.4%) patients had asymptomatic ILAD, whereas 375 (55.6%) patients had symptomatic ILAD. Multivariate analysis showed that vessel enhancement and etiological subtypes, not degree of stenosis, determined by high-resolution magnetic resonance imaging and RNF213 gene variant analysis were independently associated with symptomatic ILAD. The presence of the RNF213 variant was also independently associated with recurrent cerebrovascular events. CONCLUSIONS: This study demonstrates the prevalence of nonatherosclerotic ILAD in East Asian patients with ILAD. Unlike luminal changes, wall changes determined by high-resolution magnetic resonance imaging and presence of the RNF213 variant could predict stroke occurrence in patients with ILADs.


Assuntos
Endotélio Vascular/diagnóstico por imagem , Doenças Arteriais Intracranianas/diagnóstico por imagem , Doença de Moyamoya/diagnóstico por imagem , Acidente Vascular Cerebral/diagnóstico por imagem , Adulto , Extremo Oriente/epidemiologia , Feminino , Humanos , Doenças Arteriais Intracranianas/epidemiologia , Imageamento por Ressonância Magnética/tendências , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Estudos Prospectivos , Acidente Vascular Cerebral/epidemiologia
9.
Spine (Phila Pa 1976) ; 45(15): E917-E926, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32675603

RESUMO

STUDY DESIGN: A retrospective study with prospectively-collected data. OBJECTIVE: To determine how type, location, and size of endplate lesions on magnetic resonance imaging (MRI) may be associated with symptoms and clinical outcomes after anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: Structural endplate abnormalities are important, yet understudied, phenomena in the cervical spine. ACDF is a common surgical treatment for degenerative disc disease; however, adjacent segment degeneration/disease (ASD) may develop. METHODS: Assessed the imaging, symptoms and clinical outcomes of 861 patients who underwent ACDF at a single center. MRI and plain radiographs of the cervical spine were evaluated. Endplate abnormalities on MRI were identified and stratified by type (atypical, typical), location, relation to operative levels, presence at the adjacent level, and size. These strata were assessed for association with presenting symptoms, patient-reported, and postoperative outcomes. RESULTS: Of 861 patients (mean follow-up: 17.4 months), 57.3% had evidence of endplate abnormalities, 39.0% had typical abnormalities, while 18.2% had atypical abnormalities. Patients with any endplate abnormality had greater odds of myelopathy irrespective of location or size, while sensory deficits were associated with atypical lesions (P = 0.016). Typical and atypical abnormalities demonstrated differences in patient-reported outcomes based on location relative to the fused segment. Typical variants were not associated with adverse surgical outcomes, while atypical lesions were associated with ASD (irrespective of size/location; P = 0.004) and reoperations, when a large abnormality was present at the proximal adjacent level (P = 0.025). CONCLUSION: This is the first study to examine endplate abnormalities on MRI of the cervical spine, demonstrating distinct risk profiles for symptoms, patient-reported, and surgical outcomes after ACDF. Patients with typical lesions reported worsening postoperative pain/disability, while those with atypical abnormalities experienced greater rates of ASD and reoperation. This highlights the relevance of a degenerative spine phenotypic assessment, and suggests endplate abnormalities may prognosticate clinical outcomes after surgery. LEVEL OF EVIDENCE: 3.


Assuntos
Vértebras Cervicais/anormalidades , Vértebras Cervicais/diagnóstico por imagem , Pessoas com Deficiência , Discotomia/efeitos adversos , Degeneração do Disco Intervertebral/diagnóstico por imagem , Dor Pós-Operatória/diagnóstico por imagem , Fusão Vertebral/efeitos adversos , Adulto , Vértebras Cervicais/cirurgia , Discotomia/tendências , Feminino , Seguimentos , Humanos , Degeneração do Disco Intervertebral/etiologia , Degeneração do Disco Intervertebral/cirurgia , Imageamento por Ressonância Magnética/tendências , Masculino , Pessoa de Meia-Idade , Dor Pós-Operatória/etiologia , Dor Pós-Operatória/cirurgia , Estudos Prospectivos , Reoperação/tendências , Estudos Retrospectivos , Fusão Vertebral/tendências
10.
Neurology ; 95(11): e1582-e1589, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32690782

RESUMO

OBJECTIVE: To assess the predictive value of T2 appearance as a defining criterion of T2-fluid-attenuated inversion recovery (FLAIR) mismatch sign (T2FM), further characterize tumors that display the marker, and describe its radiographic evolution. METHODS: Records from 64 patients with astrocytomas were assessed for age at diagnosis, sex, tumor characteristics on pretreatment CT, MRI, and pathology, documentation of T2FM, treatment course, and temporal changes in tumor appearance. Cases were divided into those meeting classic criteria (homogenous T2, hyperintense FLAIR rim), those considered geographic (heterogeneous T2, hyperintense FLAIR rim), and those that were negative (no FLAIR rim). Groups were compared using χ2, estimate of effect, and qualitative analyses. RESULTS: Including geographic tumors increased T2FM sensitivity 30% among astrocytomas without decreased specificity for IDH mutation. Tumors with T2FM characteristics were more cystic, less enhancing, and affected younger patients. T2FM persisted in residual tumors following subtotal resection and disappeared with radiotherapy, persisted in 5/8 recurrent tumors that were originally T2FM-positive, and was identified in tumors with high-grade characteristics. T2FM was able to predict IDH mutation status on sequencing when antibody testing was negative. CONCLUSIONS: The presence of a hyperintense FLAIR rim, regardless of T2 appearance, is a reliable indicator of IDH mutation among astrocytomas. Tumors with a FLAIR rim are more cystic and this may lend to their characteristic appearance on MRI. T2FM demonstrates distinctive temporal radiographic changes, may be seen in high-grade gliomas, and may be used in combination with other variables to strengthen prediction of IDH status.


Assuntos
Astrocitoma/diagnóstico por imagem , Astrocitoma/genética , Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/genética , Isocitrato Desidrogenase/genética , Mutação/genética , Adulto , Estudos Transversais , Feminino , Humanos , Imageamento por Ressonância Magnética/tendências , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
11.
Neurology ; 95(3): e291-e298, 2020 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-32576636

RESUMO

OBJECTIVE: To determine whether deep white matter and periventricular hyperintensities affect the motor symptoms of Parkinson disease (PD) differently, we analyzed MRI and dopamine transporter imaging. METHODS: We analyzed the medical records of patients with de novo PD who underwent dopamine transporter PET scanning and MRI at their first visit. Deep white matter and periventricular hyperintensities were scored with a visual rating scale, and motor symptoms were assessed by Unified Parkinson's Disease Rating Scale motor score and tremor, rigidity, bradykinesia, and axial symptom subscores. The influence of white matter hyperintensity on motor symptoms was explored using multivariable linear regression models. RESULTS: A total of 93 patients (mean age, 67.2 ± 9.9 years; 44 male) were included and the mean motor score was 25.0 ± 10.8. Subscores for bradykinesia and axial symptoms were correlated with both deep white matter and periventricular hyperintensities scores. Multivariable linear regression models revealed that deep white matter hyperintensities score was significantly associated with subscore for bradykinesia and periventricular hyperintensities score was associated with subscores for bradykinesia and axial symptoms after adjusting for putaminal dopamine transporter availability and clinical factors. CONCLUSIONS: These results demonstrate that deep white matter hyperintensities are associated with bradykinesia and periventricular hyperintensities are associated with bradykinesia and axial symptoms in patients with PD independently of the severity of dopaminergic depletion.


Assuntos
Transtornos das Habilidades Motoras/diagnóstico por imagem , Transtornos das Habilidades Motoras/metabolismo , Doença de Parkinson/diagnóstico por imagem , Doença de Parkinson/metabolismo , Substância Branca/diagnóstico por imagem , Substância Branca/metabolismo , Idoso , Feminino , Humanos , Imageamento por Ressonância Magnética/tendências , Masculino , Pessoa de Meia-Idade , Tomografia por Emissão de Pósitrons/tendências
12.
Magy Onkol ; 64(2): 139-144, 2020 Jun 10.
Artigo em Húngaro | MEDLINE | ID: mdl-32520007

RESUMO

Modern imaging processes, with CT and MRI diagnostics among them, play an increasingly important role in the early diagnosis and determination of the extent and nature of illnesses and the evaluation of their response to therapy. The authors review the technical and technological improvements that have recently been realised in CT and MRI diagnostics and are being adopted in clinical practice. Relying on the results achieved so far, they are analysing the potential for further development. In both modalities, the primary aim is incessant hardware and software upgrades, the implementation of cost-efficient solutions by increasing efficiency and cutting back maintenance and operational costs. The reduction in examination time, the ever-improving image quality and the increased comfort level of the examination environment are of outstanding significance to both the patient and the staff. The interpretation of the generated data is highly dependent on the level of expertise and experience and the knowledge of clinical data and technical opportunities of the person issuing the findings. This process is going to be assisted by artificial intelligence (AI) that the authors also discuss in terms of CT and MRI diagnostics.


Assuntos
Inteligência Artificial , Imageamento por Ressonância Magnética , Tomografia Computadorizada por Raios X , Humanos , Imageamento por Ressonância Magnética/tendências , Software , Tomografia Computadorizada por Raios X/tendências
13.
Br J Radiol ; 93(1111): 20200113, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32496816

RESUMO

MRI developed during the last half-century from a very basic concept to an indispensable non-ionising medical imaging technique that has found broad application in diagnostics, therapy control and far beyond. Due to its excellent soft-tissue contrast and the huge variety of accessible tissue- and physiological-parameters, MRI is often preferred to other existing modalities. In the course of its development, MRI underwent many substantial transformations. From the beginning, starting as a proof of concept, much effort was expended to develop the appropriate basic scanning technology and methodology, and to establish the many clinical contrasts (e.g., T1, T2, flow, diffusion, water/fat, etc.) that MRI is famous for today. Beyond that, additional prominent innovations to the field have been parallel imaging and compressed sensing, leading to significant scanning time reductions, and the move towards higher static magnetic field strengths, which led to increased sensitivity and improved image quality. Improvements in workflow and the use of artificial intelligence are among many current trends seen in this field, paving the way for a broad use of MRI. The 125th anniversary of the BJR is a good point to reflect on all these changes and developments and to offer some slightly speculative ideas as to what the future may bring.


Assuntos
Invenções/tendências , Imageamento por Ressonância Magnética/tendências , Inteligência Artificial/tendências , Meios de Contraste , Aprendizado Profundo/tendências , Humanos , Imageamento por Ressonância Magnética/instrumentação , Imageamento por Ressonância Magnética/métodos , Magnetismo , Fluxo de Trabalho
14.
Int J Cardiovasc Imaging ; 36(9): 1737-1747, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32394180

RESUMO

Cardiovascular magnetic resonance (CMR) is a non-invasive imaging technology, gradually playing an irreplaceable role in the diagnosis and treatment of cardiovascular diseases. This review demonstrates the progress and research highlights of Chinese CMR publications of the last more than 30 years. At initial stage (1988 to 1997), CMR was introduced to evaluate cardiac anatomy, blood flow and ventricular function roughly in China. In the development stage (1998-2007), CMR began to play an important role in the diagnosis of cardiovascular and pericardial disease with the emergence of new techniques, such as myocardial perfusion imaging and magnetic resonance angiography. Since 2008, the development of CMR in China has reached a prosperous period. Cardiovascular disease can be both qualitatively and quantitatively assessment by CMR "one-stop" multi-parameter imaging, including the morphology, function, myocardial perfusion, tissue characteristics, metabolism and even the microstructure of myocardial fibers, which provides comprehensive assessment of the severity, risk stratification and prognosis of cardiovascular disease. Although CMR in China developed very rapidly in recent years, China still needs to put more efforts in CMR research and make greater contributions to the development of CMR in the world.


Assuntos
Pesquisa Biomédica/tendências , Doenças Cardiovasculares/diagnóstico por imagem , Imageamento por Ressonância Magnética/tendências , Animais , Pesquisa Biomédica/história , Doenças Cardiovasculares/história , Doenças Cardiovasculares/patologia , Doenças Cardiovasculares/fisiopatologia , China , Difusão de Inovações , História do Século XX , História do Século XXI , Humanos , Imageamento por Ressonância Magnética/história , Miocárdio/patologia , Valor Preditivo dos Testes , Prognóstico
15.
Rofo ; 192(6): 537-548, 2020 Jun.
Artigo em Inglês, Alemão | MEDLINE | ID: mdl-32396945

RESUMO

BACKGROUND: For more than two decades, the focus of technological progress in MRI was restricted to systems with a field strength of 1.5 T and higher. Low- and mid-field MRI systems, which offer some specific advantages, are vanishing from the market. This article is intended to initiate a re-evaluation of the factor 'field strength' in MR imaging. METHOD: Literature review was carried out using MEDLINE database (via Pubmed) over a time span from 1980 to 2019 using free-text and Medical Subject headings (MeSH). Article selection was based on relevance and evidence. RESULTS AND CONCLUSION: Low-field MR systems are meanwhile rare in clinical imaging. MRI systems with a lower field strength provide a reduced signal-noise ratio (SNR) and spectral differentiation. However, these systems offer a variety of advantages: Shorter T1 relaxation, better T1 contrast, fewer metal artifacts, reduced susceptibility and chemical shift artifacts, fewer dielectric effects, better tissue penetration, less RF-power deposition, fewer 'missile effects', reduced effect on biomedical implants such as shunt valves, less energy and helium consumption. If we free ourselves from the constraints of high-field strength, we are able to offer multiple medical, economic and ecologic advantages to our patients. The development of high-quality low-field MRI is possible and necessary. KEY POINTS: · Static magnetic field strength is only one of many parameters influencing image quality in MR imaging.. · Lower field strength results in a lower signal-to-noise ratio (SNR).. · Modern MR systems offer technical tools to improve signal strength and reduce noise. This makes it possible to provide a diagnostic SNR at a lower field strength.. · Low-field MR systems offer important advantages which have to be made available to our patients.. CITATION FORMAT: · Klein H-M. Low-Field Magnetic Resonance Imaging. Fortschr Röntgenstr 2020; 192: 537 - 548.


Assuntos
Aumento da Imagem/métodos , Imageamento por Ressonância Magnética/métodos , Previsões , Física Médica , Humanos , Imageamento por Ressonância Magnética/tendências , Segurança do Paciente , Razão Sinal-Ruído
16.
J Neuroimmunol ; 344: 577247, 2020 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-32388192

RESUMO

OBJECTIVES: There is a delicate homeostatic balance between the central nervous system and immune system. Stroke triggers an immunodepressive state to suppress a potential immune reaction directed against neuroglial tissue; however, this supposedly protective response inadvertently results in an infection-prone, and thereby a pro-inflammatory setting. In this study, we assessed the magnitude of cerebral volume loss in the unaffected contralateral hemisphere following stroke, and determined its relationship with inflammatory cascades. METHODS: The volume of the hemisphere contralateral to the ischemic insult was measured on admission and follow-up MRI's in 50 ischemic stroke patients. Information related to clinical features, infectious complications, and markers of inflammation (erythrocyte sedimentation rate, neutrophil/lymphocyte ratio, C-reactive protein) were prospectively collected, and their relationship with hemispheric volume change was evaluated using bivariate and multivariate statistics. RESULTS: The contralateral hemisphere volume decreased by a median (interquartile range) of 14 (4-32) mL after a follow-up duration of 101 (63-123) days (p < .001); the volume reduction was 0.8 (0.2-1.8) % per month with respect to baseline. Old age, atrial fibrillation, stroke severity, C-reactive protein level, neutrophil/lymphocyte ratio, and development of infections during hospitalization were significantly associated with volume loss (p < .05). Stroke severity (NIHSS score or infarct volume) and inflammation related parameters (neutrophil/lymphocyte ratio or systemic infections) remained independently and positively associated with volume loss in multivariate regression models. CONCLUSIONS: Cerebral tissue changes following stroke are not limited to the ischemic hemisphere. Apart from stroke severity, a pro-inflammatory state and post-stroke infections contribute to cerebral volume loss in the non-ischemic hemisphere.


Assuntos
Isquemia Encefálica/sangue , Isquemia Encefálica/diagnóstico por imagem , Cérebro/diagnóstico por imagem , Mediadores da Inflamação/sangue , Acidente Vascular Cerebral/sangue , Acidente Vascular Cerebral/diagnóstico por imagem , Idoso , Feminino , Seguimentos , Humanos , Imageamento por Ressonância Magnética/tendências , Masculino , Pessoa de Meia-Idade , Tamanho do Órgão , Estudos Prospectivos
17.
Neural Netw ; 128: 248-253, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32454369

RESUMO

Transform learning is a new representation learning framework where we learn an operator/transform that analyses the data to generate the coefficient/representation. We propose a variant of it called the graph transform learning; in this we explicitly account for the correlation in the dataset in terms of graph Laplacian. We will give two variants; in the first one the graph is computed from the data and fixed during the operation. In the second, the graph is learnt iteratively from the data during operation. The first technique will be applied for clustering, and the second one for solving inverse problems.


Assuntos
Imageamento por Ressonância Magnética/métodos , Aprendizado de Máquina não Supervisionado , Algoritmos , Análise por Conglomerados , Humanos , Imageamento por Ressonância Magnética/tendências , Resolução de Problemas , Aprendizado de Máquina não Supervisionado/tendências
18.
J Clin Neurosci ; 78: 246-251, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32340842

RESUMO

Stagnant blood flow and organizing thrombus are intralesional components of patients with cerebral cavernous malformations (CCM). Stasis and inflammation are mechanisms of growth, lesional instability and acute hemorrhages with or w/o symptoms. We evaluate the association of pre-diagnostic aspirin and/or statin use with acute hemorrhages at diagnosis. Patients with a CCM diagnosis were identified and categorized according to their medications on admission into four groups (no therapy, statin, aspirin, combined). The primary outcome was an acute hemorrhage (with or w/o symptoms) at diagnosis reported in a standardized manner from the T2 weighted magnetic resonance image. A multivariate generalized linear mixed models (GLMM) was utilized to conduct per-lesion analysis. We identified 446 patients with 635 lesions. An acute hemorrhage at diagnosis was observed in 31% of the patients. There were 328 patients without statin or aspirin therapy, 34% of whom presented with acute hemorrhage. Of patients on aspirin therapy at diagnosis, 25% presented with hemorrhage. Of patients on statin therapy, 26% had a hemorrhage at diagnosis. Combined therapy in 44 patients demonstrated a lower proportion of patients with acute hemorrhages (7 patients, 16% incidence). A GLMM showed that patients in the combined therapy group to have significantly lower odds of having an acute hemorrhage at diagnosis compared to the reference group of no therapy (OR 0.24; 95% CI 0.09-0.59; P = 0.002). Patients with a CCM receiving therapy with both aspirin and statins were less likely to present at diagnosis with acute hemorrhage.


Assuntos
Fístula Arteriovenosa/diagnóstico por imagem , Fístula Arteriovenosa/tratamento farmacológico , Aspirina/uso terapêutico , Inibidores de Hidroximetilglutaril-CoA Redutases/uso terapêutico , Malformações Arteriovenosas Intracranianas/diagnóstico por imagem , Malformações Arteriovenosas Intracranianas/tratamento farmacológico , Adulto , Idoso , Hemorragia Cerebral/diagnóstico por imagem , Hemorragia Cerebral/prevenção & controle , Estudos Transversais , Feminino , Humanos , Imageamento por Ressonância Magnética/tendências , Masculino , Pessoa de Meia-Idade , Inibidores da Agregação Plaquetária/uso terapêutico , Estudos Retrospectivos
19.
J Clin Neurosci ; 78: 284-290, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32331940

RESUMO

Intracranial peripherally enhancing lesions in immunosuppressed solid organ transplant recipients represent a unique diagnostic and management dilemma due to the vast array of differentials that demand consideration. Diagnosis of the underlying pathology is often guided by the use of magnetic resonance imaging (MRI). We present the first published case series of three cardiac transplant recipients with significantly atypical neuroradiological findings contrary to the tenets of contemporary literature. Our rare case series consists of: (1) A sterile Mycobacterium pyogenic abscess mimicking glioblastoma multiforme due to an immunosuppressed state (2) Epstein Barr Virus encephalitis masquerading as Central Nervous System Post-Transplant Lymphoproliferative Disorder (3) An unusual case of partially treated disseminated Nocardiosis warning of the need to consider the immunosuppressed state and partial treatment response obfuscating classical MRI appearances. We utilise these unprecedented cases as the basis of a literature review to understand the pathophysiology behind the peculiar imaging findings in this rarefied cohort of transplant recipients, and rationalise why the MRI findings in each instance contradicts the accepted imaging patterns. In the setting of potential unreliability of neuroradiology in this immunosuppressed unique subgroup, we hope to impart to clinicians that definitive diagnosis obtained by emergent neurosurgical intervention may be necessary to accurately and expediently guide further medical management.


Assuntos
Encefalite Viral/diagnóstico por imagem , Infecções por Vírus Epstein-Barr/diagnóstico por imagem , Transplante de Coração/efeitos adversos , Transtornos Linfoproliferativos/diagnóstico por imagem , Nocardiose/diagnóstico por imagem , Transplantados , Idoso , Encefalite Viral/imunologia , Infecções por Vírus Epstein-Barr/imunologia , Transplante de Coração/tendências , Humanos , Hospedeiro Imunocomprometido/imunologia , Transtornos Linfoproliferativos/imunologia , Imageamento por Ressonância Magnética/tendências , Masculino , Pessoa de Meia-Idade , Nocardiose/imunologia
20.
Neural Netw ; 127: 67-81, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32334342

RESUMO

In the domain of machine learning, Neural Memory Networks (NMNs) have recently achieved impressive results in a variety of application areas including visual question answering, trajectory prediction, object tracking, and language modelling. However, we observe that the attention based knowledge retrieval mechanisms used in current NMNs restrict them from achieving their full potential as the attention process retrieves information based on a set of static connection weights. This is suboptimal in a setting where there are vast differences among samples in the data domain; such as anomaly detection where there is no consistent criteria for what constitutes an anomaly. In this paper, we propose a plastic neural memory access mechanism which exploits both static and dynamic connection weights in the memory read, write and output generation procedures. We demonstrate the effectiveness and flexibility of the proposed memory model in three challenging anomaly detection tasks in the medical domain: abnormal EEG identification, MRI tumour type classification and schizophrenia risk detection in children. In all settings, the proposed approach outperforms the current state-of-the-art. Furthermore, we perform an in-depth analysis demonstrating the utility of neural plasticity for the knowledge retrieval process and provide evidence on how the proposed memory model generates sparse yet informative memory outputs.


Assuntos
Eletroencefalografia/métodos , Aprendizado de Máquina , Imageamento por Ressonância Magnética/métodos , Redes Neurais de Computação , Plasticidade Neuronal , Atenção/fisiologia , Neoplasias Encefálicas/diagnóstico por imagem , Bases de Dados Factuais/tendências , Eletroencefalografia/tendências , Humanos , Aprendizado de Máquina/tendências , Imageamento por Ressonância Magnética/tendências , Memória/fisiologia , Plasticidade Neuronal/fisiologia
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