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PubMed1999

[MRI features of lymphedema of the lower extremity: comparison with lymphangioscintigraphy].

OBJECTIVE: To investigate the features of chronic lymphedema of the extremity. METHODS: Magnetic resonance imaging (MRI) and lymphangioscintigraphy (LAS) examinations were performed on 12 patients with peripheral lymphedema. RESULTS: MRI characteristically showed diffusive subcutaneous edema, reticular lymphangiectasis and "channels" with sequestered lymph. MRI scan clearly displayed the proliferative and extended lymphatic vessels, trunks and chylocyst. LAS showed dermal diffusion (dermal backflow) or retention at the injection site of the tracer with poorly defined lymphatic trunks and delayed or no visualization of regional lymph nodes. CONCLUSION: MRI can visualise peripheral lymph trunks, lymph nodes and soft tissue. LAS is more helpful in ascertaining the condition of obstruction of lymphatic system. Using these two imaging modalities together is helpful for anatomical diagnosis and delineating the disarranged pattern of lymphedema.

Adolescent↗
PubMed2006

Watershed strokes after cardiac surgery: diagnosis, etiology, and outcome.

BACKGROUND AND PURPOSE: Watershed strokes are more prevalent after cardiac surgery than in other stroke populations, but their mechanism in this setting is not understood. We investigated the role of intraoperative blood pressure in the development of watershed strokes and used MRI to evaluate diagnosis and outcomes associated with this stroke subtype. METHODS: From 1998 to 2003 we studied 98 patients with clinical stroke after cardiac surgery who underwent MRI with diffusion-weighted imaging. We used logistic regression to explore the relationship between mean arterial pressure and watershed infarcts, between watershed infarcts and outcome, and chi(2) analyses to compare detection by MRI versus CT of watershed infarcts. RESULTS: Bilateral watershed infarcts were present on 48% of MRIs and 22% of CTs (P<0.0001). Perioperative stroke patients with bilateral watershed infarcts, compared with those with other infarct patterns, were 17.3 times more likely to die, 12.5 and 6.2 times more likely to be discharged to a skilled nursing facility and to acute rehabilitation, respectively, than to be discharged home (P=0.0004). Patients with a decrease in mean arterial pressure of at least 10 mm Hg (intraoperative compared with preoperative) were 4.1 times more likely to have bilateral watershed infarcts than other infarct patterns. CONCLUSIONS: Bilateral watershed infarcts after cardiac surgery are most reliably detected by diffusion-weighted imaging MRI and are associated with poor short-term outcome, compared with other infarct types. The mechanism may include an intraoperative drop in blood pressure from a patient's baseline. These findings have implications for future clinical practice and research.

Aged↗
PubMed2002

Diffusion weighted magnetic resonance imaging in the diagnosis of reversible ischaemic deficits of the brainstem.

OBJECTIVES: To evaluate the sensitivity of diffusion weighted magnetic resonance imaging (MRI) for the diagnosis of clinically suspected reversible ischaemic deficits of the brainstem. METHODS: A total of 158 consecutive patients presenting with acute signs of brainstem dysfunction were investigated using EPI diffusion weighted MRI within 24 hours of the onset of symptoms. High resolution T1 and T2 weighted imaging was performed as a follow up after a median of six days. RESULTS: Fourteen of the 158 patients had a complete clinical recovery within 24 hours (transitory ischaemic attack (TIA)), and 19 patients recovered in less than one week (prolonged reversible neurological deficit (RIND)). Diffusion weighted MRI showed acute ischaemic deficits in 39% of patients with transient neurological deficits. The detection rate seemed to be higher in patients with longer lasting symptoms, but the difference between patients with TIA (29%) and RIND (47%) was not significant. CONCLUSIONS: Diffusion weighted MRI is a sensitive indicator of acute ischaemic brainstem deficits even in patients with reversible neurological deficit. Early identification of patients with TIA and increased risk of stroke may influence acute management and improve patient outcome.

Acute Disease↗
PubMed2006

Dynamics of cerebral edema and the apparent diffusion coefficient of water changes in patients with severe traumatic brain injury. A prospective MRI study.

The distinction between intracellular (ICE) and extracellular edema (ECE) has a crucial prognostic and therapeutic importance in patients with severe traumatic brain injury (STBI). Indeed, ICE usually leads to cellular death, and maintenance of a cerebral perfusion pressure (CPP) above 70 mmHg is still under debate since this practice may increase ECE. The purpose of this study was to describe the ECE and ICE kinetics associated with STBI using quantitative diffusion MRI. Twelve patients were prospectively studied. The initial ADC in ICE measured on day 1.3+/-0.7 is significantly reduced compared to normal-appearing parenchyma (0.51+/-0.12 * 10(-3) mm2/s vs. 0.76+/-0.03 * 10(-3) mm2/s, n=12, P<0.0001) and reaches normality on MRI 3 performed on day 14.2+/-3.3. In patients presenting an extension of ICE on MRI 2 performed on day 6.7+/-1.4 (ADC(MRI2)=0.40+/-0.11 * 10(-3) mm2/s), ADC values in the extension area at the first MRI were slightly, but not significantly reduced compared to normal parenchyma (0.69+/-0.05 * 10(-3) mm2/s, P=0.29). Normalization occurred equally by day 14. ADC in ECE (1.34+/-0.22 * 10(-3) mm2/s) was elevated and stable with time under CPP therapy. Therefore, ECE is not worsened by CCP therapy, and ICE appears more relevant than ECE in STBI.

Adolescent↗
PubMed2005

[A case of spontaneous intracranial hypotension with multiple CSF leaks in the thoracic region].

A case of spontaneous intracranial hypotension (SIH) with multiple cerebrospinal fluid (CSF) leaks is reported. A 54-year-old man experienced a severe generalized headache associated with nausea and decreased hearing. The headache appeared when he was sitting or standing but was completely relieved by lying down. Cranial MRI with gadolinium infusion showed diffuse pachymeningeal enhancement. Spinal MRI demonstrated small amount of epidural fluid collection in the upper thoracic region. Radionuclide cisternography demonstrated CSF leaks at the Th2 and Th7 levels on the left side and at the Th3 through Th5 levels on the right side. Since bed-rest and intravenous transfusion for 10 days showed no beneficial effects, epidural blood patch (EBP) at the Th6/7 interspace was performed. After receiving EBP four times repeatedly, his symptoms entirely disappeared. SIH patients with multiple CSF leaks are rare in the literature. Although no consensus exists on the treatment strategy for such cases, our case suggests that at least 2 EBPs should be performed for each leak site before considering surgical treatment.

Blood Patch, Epidural↗
PubMed2003

The effect of water molecular self-diffusion on quantitative high-resolution MRI polymer gel dosimetry.

In polymer gel dosimetry, magnetic resonance imaging (MRI) is used to determine the spin-spin relaxation rate (R2) which in turn can be correlated with absorbed dose to provide a map of the spatial distribution of the absorbed dose in the irradiated dosimeter. High accuracy, precision and reproducibility of these dose maps are essential. Moreover, for dose verification around brachytherapy sources used for intravascular brachytherapy, a high spatial resolution is required (typically 0.01-0.1 mm). To achieve these microscopic resolutions, strong imaging gradients are applied. The Brownian motion of water molecules in the presence of these strong magnetic field gradients causes an attenuation of the MR signal. When using a multiple spin-echo sequence, this may result in a significant deviation in the measured R2. The diffusion-related change in R2 at high resolutions was investigated experimentally and correlated with predictions that were obtained numerically and algebraically. Diffusion weighting is determined by the self-diffusion coefficient D, and imaging parameters, quantified by the b-factor. The b-factor was calculated for a multiple spin-echo sequence for different gradient strengths and gradient pulse durations. The variations in R2 that were observed when changing the matrix size and slice thickness are explained. It is shown that a linear correlation between the matrix size and the variation in R2 is based on the diffusion weighting caused by the read-out gradients and slice selective gradients. In conclusion, the essence of taking into account molecular self-diffusion to quantify variations in the measured dose-R2 response when using high-resolution MRI in polymer gel dosimetry is emphasized.

Algorithms↗
PubMed2005

[Neuroimaging characteristics of cerebral infarcts].

Over the last years, technical advances in neuroimaging have allowed drastic improvements in the assessment of acute ischemic cerebral events. Beyond conventional morphological analysis, diffusion-weighted and perfusion-weighted MRI now enable routine functional assessment of brain tissue; spectroscopy and diffusion tensor imaging still remains in the domain of clinical research. During acute ischemia events, diffusion-weighted MRI can detect the movements of water molecules and cytotoxic edema related to cell injury enabling rapid diagnosis and early assessment of cerebral ischemia. In conjunction with perfusion imaging, which detects hypoperfusion areas, diffusion-weighted MRI provides a means to identify areas of penumbra ischemia. More recent multislice computed tomographic (CT) scans with multimodal analysis are also very competitive for assessment of cerebral ischemia (non-enhanced CT, CT angiography and perfusion CT). The purpose of this paper is to describe the CT and MRI patterns during the different stages of cerebral infarcts.

Acute Disease↗
PubMed1994

Incidence of apparent restricted diffusion in three different models of cerebral infarction.

High speed magnetic resonance imaging (MRI) and short diffusion times are used to investigate the appearance of restricted diffusion in three different models of cerebral infarction. The models are: the middle cerebral artery occlusion (MCAO) model in the rat, the carotid occlusion model in the gerbil, and the Rose Bengal microvascular occlusion model in the rat. All three were investigated for 16 b-values equally spaced between 10 and 1510 s/mm2 using two distinct experiments. In the ct (constant time) experiment, the diffusion time was held constant at 11.7 ms while the b-value was varied with the gradient strength. In the cg (constant gradient) experiment, the gradient strength was held constant and the b-value increased by varying the diffusion time from 4.4 to 11.7 ms. A monoexponential decay of the signal intensity with b-value in the ct experiment accompanied by nonmonoexponential (NME) decay in the cg experiment is indicative of restricted diffusion. As this phenomenon is detectable only at short diffusion times, it cannot be due to restriction by impermeable membranes, and we have thus termed this apparent restriction. For the MCAO model and the carotid occlusion model, apparent restriction was found both inside the infarct territory and in some regions outside it. No definite evidence for restriction was found for the Rose Bengal model, which was, however, only studied from 24 h post-insult.

Animals↗
PubMedDate not supplied

Proton magnetic resonance spectroscopy and diffusion-weighted imaging of central nervous system whipple disease.

A 72-year-old man presented with a 6-month history of dysphagia, fatigue, 60-lb weight loss, and central nervous system (CNS) deficits. Diffusion-weighted magnetic resonance imaging (MRI) of the brain showed mildly elevated nonrestricted apparent diffusion coefficients in the middle cerebellar peduncles, and magnetic resonance spectroscopy (MRS) showed decreased N-acetylaspartate and creatine with increased choline. Diffusion-weighted MRI and MRS offer noninvasive methods to help evaluate in vivo physiologic changes of CNS involvement in Whipple disease.

Aged↗
PubMed1994

The introduction and evaluation of MRI in Japan.

Not only is the number of computed tomography (CT) units relative to population in Japan the highest in the world, that of magnetic resonance imaging (MRI) units is second only to the United States. This study examines the diffusion pattern of MRI in Japan, as well as the factors that influence it. The number of MRI units has increased sharply, closely following CT, as has been the case in the United States. This pattern of diffusion in Japan was determined mainly by the following factors: the technological attributes of MRI; the market situation of the medical engineering industry; the reimbursement system of health insurance; and Japan's sociocultural background. However, the introduction of MRI in Japan was not linked to any formal assessment of its efficacy or effectiveness.

Japan↗
PubMed1998

Diffuse bilateral thalamic astrocytomas as examined serially by MRI.

We report the case of a 13-year-old girl with diffuse bilateral thalamic astrocytomas. Incoordination was observed at the onset. Cranial computed tomography (CT) showed enlarged thalami, and magnetic resonance imaging (MRI) revealed these lesions to be symmetrically enlarged with high intensity on the T2-weighted image. Owing to these atypical findings in the neuroimaging studies, we had difficulty in making the correct diagnosis of a brain tumor. After the diagnosis of diffuse bilateral thalamic astrocytomas was obtained, we performed hyperfractionated radiotherapy followed by chemotherapy. Radiation therapy was effective for a while, but the girl's condition deteriorated again and she died 8 months after admission. Although diffuse bilateral thalamic astrocytomas are difficult to diagnose because they do not resemble most other neoplasms on neuroimaging studies, pediatricians should keep this entity in mind in order to arrive at a precise and prompt diagnosis.

Adolescent↗
PubMed2006

Cerebral microembolism during cardiac catheterization and risk of acute brain injury: a prospective diffusion-weighted magnetic resonance imaging study.

BACKGROUND AND PURPOSE: Cerebral microembolism detected by transcranial Doppler occurs systematically during cardiac catheterization, but its clinical relevance remains unknown. Studies suggest that asymptomatic embolic cerebral infarction detectable by diffusion-weighted (DW) MRI might exist after percutaneous cardiac interventions, especially after retrograde catheterization of the aortic valve in patients with valvular aortic stenosis, with a frequency as high as 22% of cases. We investigated the incidence of new ischemic lesions on serial cerebral DW MRI after cardiac catheterization. METHODS: This prospective study involved 46 patients with severe aortic valve stenosis. To assess the occurrence of cerebral infarction, all patients underwent cerebral DW MRI and neurological assessment within 24 hours before and 48 hours after cardiac catheterization and retrograde catheterization of the aortic valve. A subgroup was monitored by transcranial power M-mode Doppler during cardiac catheterization to observe cerebral blood flow and track emboli. RESULTS: One patient had a focal diffusion abnormality on DW MRI before cardiac catheterization. After catheterization, we detected only 1 additional acute cerebral diffusion abnormality in a single case (2.2%), although cerebral microemboli were detected in all transcranial Doppler-monitored patients during cardiac catheterization, as expected. All patients remained asymptomatic. Based on these results a mid-point incidence of 5.9% (95% CI, 0.01 to 12.5) for abnormalities on DW MRI in asymptomatic cardiac catheterization patients in our center can be assigned. CONCLUSIONS: Unsuspected cerebral infarctions can be detected by DW MRI after cardiac catheterization, but this phenomenon remains unfrequent in our series. Further studies are needed to identify factors explaining the discrepancy between these results and those of previous studies.

Aged↗
PubMed2000

Acute and late changes in N-acetyl-aspartate following diffuse axonal injury in rats: an MRI spectroscopy and microdialysis study.

N-acetyl-aspartate (NAA) measured by proton nuclear magnetic resonance spectroscopy (1H-NMR) has been used as a marker of neuronal injury in many cerebral pathologies. Therefore, we evaluate the roles of microdialysis vs. 1H-NMR as techniques to assess NAA (NAAd; NAA/Creatine ratio) in the living brain, and compare the results with whole brain NAA (NAAw), analyzed by HPLC after diffuse traumatic brain injury (TBI). Acute (4 h post-injury survival) and late (48 h survival) changes were studied in a sham-operated group (Sham, n = 4), and two injured groups (TBI/4 h, n = 8; TBI/48 h, n = 7). Baseline NAAd was 8.17 +/- 1 microM, and there was no significant difference between groups. There was only a small (twice of control), but transient increase in NAAd in the TBI/4 h group after trauma. Baseline NAA/Cr ratio was 1.35 +/- 0.2, which did not change significantly between baseline, 1, 2, 3, 4 and 48 h or between groups after TBI. Whole brain NAAw (baseline 8.5 +/- 0.5 mmol kg-1 wet weight) did not differ significantly between groups before and after TBI. Diffuse TBI did not produce long-term changes in NAA, assessed by three different methods. These results may indicate that NAA is not a sensitive marker of the severity of diffuse axonal damage. However, further studies are needed to evaluate whether confounding factors such as microdialysis probe, voxel position and non-regional tissue homogenization might have influenced our data.

Animals↗
PubMed1990

[Diffuse bilateral periventricular hyperintensity of unknown origin on MRI spin-echo sequence. Cognitive function and regional cerebral blood flow].

Cognitive function and regional cerebral blood flow (rCBF) were studied in 26 patients (mean age 77.9) who showed bilaterally an ill-defined diffuse periventricular hyperintensity (PVH) on the magnetic resonance imaging (MRI) spin-echo sequence. Diffuse PVH was classified into two groups according to severity, group A (more severe) and group B (less severe); their cognitive impairment was classified into three stages, stage 1 (mildly impaired) through stage 3 (severely impaired). rCBF was assessed by single photon emission computed tomography (SPECT). The result showed that 6 of 7 MRI-group A patients were stage 3, but the stages of 19 group B patients varied. Five of 7 MRI-group A patients showed severe hypoperfusion, but rCBF of group B patients also varied. Nineteen patients had a hypertensive history, but only 10 patients complained of cerebrovascular incidents before admission. All 3 younger patients (one in his fifties and two in their sixties), however, showed hypertension, stepwise neurological deterioration as in Binswanger's disease. These results suggest that there might be various pathogenesis of diffuse bilateral PVH in the elderly and they are different from that of the classical "Binswanger's disease".

Aged↗
PubMed2006

Prenatal MR imaging of a meconium pseudocyst extending to the right subphrenic space with right lung compression.

Meconium pseudocyst results from a loculated inflammation occurring in response to spillage of meconium into the peritoneal cavity after a bowel perforation. Certain cystic lesions, such as abscesses and dermoid and epidermoid cysts, are known to show reduced water diffusion on DWI. MRI has recently become a valuable adjunct to ultrasonography for fetal gastrointestinal anomalies. Complementary to ultrasonography, prenatal MRI can help further characterize the lesion and can clearly demonstrate the anatomical relationship between the lesion and adjacent organs. We report a case of meconium pseudocyst that was prenatally imaged with ultrasonography and MRI, postnatally complicated by pneumoperitoneum, and proved by postnatal surgery and histopathology. We emphasize the MRI of the pseudocyst, particularly T1-weighted and diffusion-weighted imaging.

Adult↗
PubMedDate not supplied

An unusual periaqueductal glioma: A short report.

A rare case of periaqueductal glioma with an unusual radiological picture is presented. A forty-five year old male presented with progressive bilateral third and eighth nerve paresis. Magnetic resonance imaging (MRI) revealed a diffuse periaqueductal tumour with sparing of aqueduct and no hydrocephalus. MRI is a useful adjunct in such a situation for contemplating appropriate modality of treatment.

Brain Neoplasms↗
PubMed2006

Axial and radial diffusivity in preterm infants who have diffuse white matter changes on magnetic resonance imaging at term-equivalent age.

OBJECTIVE: Diffuse excessive high signal intensity (DEHSI) is observed in the majority of preterm infants at term-equivalent age on conventional MRI, and diffusion-weighted imaging has shown that apparent diffusion coefficient values are elevated in the white matter (WM) in DEHSI. Our aim was to obtain diffusion tensor imaging on preterm infants at term-equivalent age and term control infants to test the hypothesis that radial diffusivity was significantly different in the WM in preterm infants with DEHSI compared with both preterm infants with normal-appearing WM on conventional MRI and term control infants. METHODS: Diffusion tensor imaging was obtained on 38 preterm infants at term-equivalent age and 8 term control infants. Values for axial (lambda1) and radial [(lambda2 + lambda3)/2] diffusivity were calculated in regions of interest positioned in the central WM at the level of the centrum semiovale, frontal WM, posterior periventricular WM, occipital WM, anterior and posterior portions of the posterior limb of the internal capsule, and the genu and splenium of the corpus callosum. RESULTS: Radial diffusivity was elevated significantly in the posterior portion of the posterior limb of the internal capsule and the splenium of the corpus callosum, and both axial and radial diffusivity were elevated significantly in the WM at the level of the centrum semiovale, the frontal WM, the periventricular WM, and the occipital WM in preterm infants with DEHSI compared with preterm infants with normal-appearing WM and term control infants. There was no significant difference between term control infants and preterm infants with normal-appearing WM in any region studied. CONCLUSIONS: These findings suggest that DEHSI represents an oligodendrocyte and/or axonal abnormality that is widespread throughout the cerebral WM.

Brain↗
PubMed2002

[A case of brain ischemia presenting spectacular shrinking deficit in adult-onset Still's disease associated with antiphospholipid antibody syndrome].

A 63-year-old man presenting remittent fever and multiple arthralgia was diagnosed as adult-onset Still's disease (AOSD), and started with prednisolone treatment. However, he suddenly developed loss of consciousness, paresis of the right upper extremity and aphasia shortly after the treatment. We detected an increased signal of brain tissue lactate at the branch territory of left middle cerebral artery by MR spectroscopy (MRS), but no lesions by diffusion-weighted nor T2-weighted MRI, suggesting acute brain ischemia of embolic mechanism. Most of the symptoms resolved in a couple of hours after the onset, showing spectacular shrinking deficit (SSD). The patient also revealed complication of antiphospholipid antibody syndrome (APS), which may be associated with ischemic event. This is the first case of acute brain ischemia with SSD, which occurred in AOSD with APS. MRS was superior to diffusion MRI in detection of acute brain ischemia.

Antiphospholipid Syndrome↗