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ADC Maps (adc + map)
Selected AbstractsBrain Apparent Water Diffusion Coefficient Magnetic Resonance Image During a Prolonged Visual AuraHEADACHE, Issue 6 2010Robert Belvís MD (Headache 2010;50:1045-1049) Background., Reversible changes in brain magnetic resonance imaging (MRI) weighted in diffusion-weighted images (DWI) and apparent water diffusion coefficient (ADC) maps have been reported in acute stroke, epilepsy, eclampsia, and hypoglycemia, but they are contradictory regarding to migraine aura. Objective., A 41-year-old woman with known basilar migraine for 5 years consulted about a persistent visual aura (visual snow phenomenon) plus bilateral paresthesias in the extremities for 4 days. The headache was treated with success with 10 mg of wafer rizatriptan and 600 mg of ibuprophen. Methods., The neurologic and ophthalmologic examination were normal. An urgent brain MRI detected no lesions in T1, T2, fluid-attenuated inversion recovery, and DWI, but an abnormal signal appeared in the left occipital lobe in ADC and (r)ADC maps. The brain MRI angiography, carotid ultrasound study, transesophageal echocardiography, 24-hour cardiac Holter monitoring, and thrombophilia study were normal. Results., A new brain MRI 8 days after did not show any previous lesion in the same sequences. Conclusions., We present a patient with migraine and transitory abnormal signals in the ADC map of an occipital region during persistent visual aura. The clinical-radiological relationship is congruent. Some similar cases have showed these MRI signals during the aura, suggesting cytotoxic edema, without ischemic lesions in the MRI controls. Theses ADC images probably appear in complex auras. [source] The bootstrap and cross-validation in neuroimaging applications: Estimation of the distribution of extrema of random fields for single volume tests, with an application to ADC mapsHUMAN BRAIN MAPPING, Issue 10 2007Roberto Viviani Abstract We discuss the assessment of signal change in single magnetic resonance images (MRI) based on quantifying significant departure from a reference distribution estimated from a large sample of normal subjects. The parametric approach is to build a test based on the expected distribution of extrema in random fields. However, in conditions where the variance is not uniform across the volume and the smoothness of the images is moderate to low, this test may be rather conservative. Furthermore, parametric tests are limited to datasets for which distributional assumptions hold. This paper investigates resampling methods that improve statistical tests for signal changes in single images in such adverse conditions, and that can be used for the assessment of images taken for clinical purposes. Two methods, the bootstrap and cross-validation, are compared. It is shown that the bootstrap may fail to provide a good estimate of the distribution of extrema of parametric maps. In contrast, calibration of the significance threshold by means of cross-validation (or related sampling without replacement techniques) address three issues at once: improved power, better voxel-by-voxel estimate of variance by local pooling, and adaptation to departures from ideal distributional assumptions on the signal. We apply the cross-validated tests to apparent diffusion coefficient maps, a type of MRI capable of detecting changes in the microstructural organization of brain parenchyma. We show that deviations from parametric assumptions are strong enough to cast doubt on the correctness of parametric tests for these images. As case studies, we present parametric maps of lesions in patients suffering from stroke and glioblastoma at different stages of evolution. Hum Brain Mapp 2007. © 2007 Wiley-Liss, Inc. [source] Hyperpolarized 3He apparent diffusion coefficient MRI of the lung: Reproducibility and volume dependency in healthy volunteers and patients with emphysemaJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2008Sandra Diaz MD Abstract Purpose To measure the apparent diffusion coefficient (ADC) of hyperpolarized (HP) 3He gas using diffusion weighted MRI in healthy volunteers and patients with emphysema and examine the reproducibility and volume dependency. Materials and Methods A total of eight healthy volunteers and 16 patients with emphysema were examined after inhalation of HP 3He gas mixed with nitrogen (N2) during breathhold starting from functional residual capacity (FRC) in supine position. Coronal diffusion-sensitized MR images were acquired. Each subject was imaged on three separate days over a seven-day period and received two different volumes (6% and 15% of total lung capacity [TLC]) of HP 3He each day. ADC maps and histograms were calculated. The mean and standard deviation (SD) of the ADC at different days and volumes were compared. Results The reproducibility of the mean ADC and SD over several days was good in both healthy volunteers and patients (SD range of 0.003,0.013 cm2/second and 0.001,0.009 cm2/second at 6% and 15% of TLC for healthy volunteers, and a SD range of 0.001,0.041 cm2/second and 0.001,0.011 cm2/second, respectively, for patients). A minor but significant increase in mean ADC with increased inhaled gas volume was observed in both groups. Conclusion Mean ADC and SD of HP 3He MRI is reproducible and discriminates well between healthy controls and patients with emphysema at the higher gas volume. This method is robust and may be useful to gain new insights into the pathophysiology and course of emphysema. J. Magn. Reson. Imaging 2008. © 2008 Wiley-Liss, Inc. [source] Subacute sclerosing panencephalitis: Relationship between clinical stage and diffusion-weighted imaging findingsJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2006Alpay Alkan MD Abstract Purpose To investigate the relationship between clinical stages and apparent diffusion coefficient (ADC) changes in the brain of patients with subacute sclerosing panencephalitis (SSPE). Materials and Methods A total of 18 patients with stage II (N = 11) and III (N = 7) SSPE and 11 age-matched controls underwent routine MRI and diffusion-weighted imaging (DWI). The ADC values were automatically calculated. Seven distinct neuroanatomic structures (frontal, parieto-occipital, and cerebellar white matter; deep white matter; thalamus; basal ganglia; and brainstem) were selected for analysis in the patient and control groups. Results Hyperintensities in the periventricular and subcortical white matters on T2-weighted images and ADC maps were detected in 63.6% of patients with stage II and in all patients with stage III. There were significant differences between stage II and III patients and also between patients and control group in ADC values that obtained from all locations. The highest mean ADC values were calculated in stage III patients. Although MRI and DWI findings were normal in four patients with stage II disease, ADC values were significantly increased when compared with controls. Conclusion The stage of disorder may be independent of DWI appearance during the early stage (stages I and II), even though the brain is affected. Therefore, DWI and ADC values supplemental to routine MRI should also be utilized for lesion detection and definition to enhance diagnostic accuracy in patients with SSPE. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] Characterizing the diffusion/perfusion mismatch in experimental focal cerebral ischemiaANNALS OF NEUROLOGY, Issue 2 2004Xiangjun Meng MD Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) can rapidly detect lesions in acute ischemic stroke patients. The PWI volume is typically substantially larger than the DWI volume shortly after onset, that is, a diffusion/ perfusion mismatch. The aims of this study were to follow the evolution of the diffusion/ perfusion mismatch in permanent and 60- minute temporary focal experimental ischemia models in Sprague-Dawley rats using the intraluminal middle cerebral artery occlusion (MCAO) method. DWI and arterial spin-labeled PWI were performed at 30, 60, 90, 120, and 180 minutes after occlusion and lesion volumes (mm3) calculated At 24 hours after MCAO, and infarct volume was determined using triphenyltetrazolium chloride staining. In the permanent MCAO group, the lesion volume on the ADC maps was significantly smaller than that on the cerebral blood flow maps through the first 60 minutes after MCAO; but not after 90 minutes of occlusion. With 60 minutes of transient ischemia, the diffusion/perfusion mismatch was similar, but after reperfusion, the lesion volumes on ADC and cerebral blood flow maps became much smaller. There was a significant difference in 24- hour infarct volumes between the permanent and temporary occlusion groups. [source] Cerebellar apparent diffusion coefficient changes in patients with supratentorial ischemic strokeACTA NEUROLOGICA SCANDINAVICA, Issue 5 2010Y. Liu Liu Y, Nuutinen J, Laakso MP, Karonen JO, Könönen M, Vanninen E, Kuikka JT, Vanninen RL. Cerebellar apparent diffusion coefficient changes in patients with supratentorial ischemic stroke. Acta Neurol Scand: 2010: 122: 316,322. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Objectives,,, To evaluate apparent diffusion coefficient (ADC) in cerebellar subregions in patients with stroke. Materials and methods,,, The total counts and ADCs were bilaterally measured on cerebellar white matter, gray matters of medial (G1), intermediate (G2), and lateral zones (G3) on SPECT and ADC maps from 20 patients with supratentorial ischemic stroke within the first 48 h and on day 8 after onset. ADCs were also obtained from 15 age-matched controls. Results,,, Within 48 h, the ADCs were significantly increased bilaterally in the G3, and tended to be increased bilaterally in the white matter and G1, and contralateral G2 compared with controls. On day 8, the ADCs were significantly increased in all contralateral cerebellar subregions and in ipsilateral G1 and G2, and tended to be increased in ipsilateral G3. The ADC value was significantly higher in contralateral than in ipsilateral white matter on day 8. The interhemispheric asymmetry indices (AIs) of ADC and SPECT were significantly associated with each other in G2 and G3 within 48 h, but not on day 8. The AIs of ADC and SPECT were significantly related to each other in the G3 within 48 h and on day 8. Conclusions,,, Supratentorial ischemic stroke may cause mild cerebellar vasogenic edema. [source] | ||||||||||