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At least 505 records · Page 28Linked to original sources
PubMed2003

Comparison of whole-body MRI with automatic moving table technique and bone scintigraphy for screening for bone metastases in patients with breast cancer.

The aim of this study was presentation of a whole-body MRI technique with a moving table as a screening tool for bone metastases in patients with breast cancer. Twenty-two patients with breast carcinoma underwent both a planar whole-body bone scintigraphy and whole-body MRI at 1.5 T. The MRI images were acquired with a moving table at six different anatomical positions within a measurement time of 20 min. Coronal images were acquired using a short-tau inversion recovery sequence, accomplished by an axial T2-weighted turbo-spin-echo sequence through the head, and a T1-weighted opposed-phase sagittal 2D fast low-angle shot sequence covering the whole spine. The MRI findings indicating bone metastases were compared with findings from bone scintigraphy. Metastatic lesions were confirmed by follow-up examinations over 1 year. Twelve patients showed bone metastases. Whole-body MRI was superior to bone scintigraphy in predicting lesion origin with a sensitivity of 92% (bone scintigraphy 83%), a specificity of 90% (scintigraphy 80%) and an accuracy of 91% (scintigraphy 82%). The MRI showed additional findings such as metastases of the lung and liver. Whole-body MRI with moving table technique may be an effective method of total body screening for bone in selected patients with breast carcinoma and a high risk of distant metastases, although with the higher costs of MRI bone scintigraphy must still be considered as the first method for screening patients with breast cancer.

Aged↗
PubMed1997

Bone marrow relaxation times in Gaucher disease before and after enzyme replacement therapy.

The aim of this work was to monitor the effectiveness of enzyme replacement therapy on the basis of the changes in T1 relaxation times in Gaucher patients. A total of 26 patients underwent MR before enzyme replacement therapy; of them, 18 have been followed-up. A total of 22 age-matched controls underwent the same MR study. Scans were focused on the femoral neck, and T1 relaxation times were measured by means of a mixed spin-echo inversion recovery sequence. The T1 relaxation times in Gaucher patients were significantly longer than normal (p < 0.05). After enzyme replacement therapy, T1 relaxation times gradually became closer to those of control subjects, and there was also a significant decrease (p < 0.01) with respect to values before therapy, probably due to an increase in the fat/water ratio. Evaluation of T1 relaxation time may supply a useful indication of Gaucher disease regression after enzyme replacement therapy particularly in those cases in which a normal skeletal appearance corresponds to prolonged T1 relaxation times.

Adolescent↗
PubMed2001

MR imaging in epilepsy that is refractory to medical therapy.

The aim of this study was the assessment of detection rate on MRI and description of MRI findings in patients with medically intractable epilepsy. Seventy-three patients with medically intractable epilepsy between the ages of 0 and 68 years old were evaluated by MRI, on three planes with spin-echo T1, fast spin-echo T2, and fluid-attenuated inversion recovery sequences, and, if necessary, with contrast-enhanced SE T1 sequences. Cerebral infarct regions with atrophy and gliosis in 8 patients, cerebral tumors in 5 patients, hippocampal sclerosis in 16 patients, radial microbrain in 1 patient, cortical dysplasia in 3 patients, pachygyria in 2 patients, subcortical heterotopia in 2 patients, schizencephaly in 3 patients, cerebral hemiatrophy in 2 patients, tuberous sclerosis in 1 patient, herpes encephalitis in 2 patients, Rasmussen's encephalitis in 1 patient, vascular malformations in 5 patients, and no abnormality in 22 patients were detected. Magnetic resonance imaging has a high success rate in detecting structural brain abnormalities, of both temporal and extratemporal locations, associated with medically intractable epilepsy syndromes. So MRI plays a primary role in planning of the treatment, primarily surgical therapy, by detecting structural epileptogenic lesions.

Adolescent↗
PubMed2006

Posttraumatic infarction in the territory supplied by the lateral lenticulostriate artery after minor head injury.

BACKGROUND: Occlusion of the intracranial arteries due to blunt head traumas has been less frequently observed in patients with minor head injuries. CASE REPORT: A 4-year-old boy presented with speech disturbance 2 h after minor head injury. An initial computed tomography (CT) scan showed a questionable finding of a focal punctate high density in the left basal ganglia. Hemiparesis developed on the right limbs 8 h post-injury, and a subsequent CT scan revealed a discrete low-density change around the focal high density. Diffusion-weighted images revealed a clearly demarcated high-signal intensity lesion in similar area on T2-weighted and fluid-attenuated inversion recovery sequences images, compatible with infarcted tissues on the territory supplied by the lateral lenticulostriate artery. His hemiparesis improved gradually, and by post-trauma day 10 he was able to walk briefly without assistance. He was discharged on foot at post-trauma day 14. DISCUSSION AND CONCLUSION: Children with minor head trauma who have normal findings on initial CT scan may rarely have basal ganglionic infarction resulting from arterial spasm or thromboembolism of the perforating arteries. Hospital admission and careful observation should be considered for patients with minor head injury and persistent neurologic deficits despite normal CT findings. Magnetic resonance study is valuable for the evaluation of posttraumatic infarction, differentiating from hemorrhagic diffuse axonal injuries.

Child, Preschool↗
PubMed2004

Development of a lipoprotein based molecular imaging MR contrast agent for the noninvasive detection of early atherosclerotic disease.

INTRODUCTION: Currently there are no clinically available means of noninvasively detecting early atherosclerotic disease because these lesions are characterized by an accumulation of extracellular lipid and foam cells, but a lack of significant wall thickening or architectural distortion. OBJECTIVE: We hypothesize that a paramagnetically labeled low density lipoprotein (LDL) could serve as a functional probe to detect sites of abnormal lipid metabolism in the vessel wall that represent sites of early disease. METHODS: Isolated LDL was first incubated with manganese-mesoporphyrin, a hydrophobic MR contrast agent (MnMeso). Size exclusion chromatography and absorption mass spectroscopy were performed on the resulting samples to prove that an association between the two occurred. Subsequently, foam cell cultures (n=7) were incubated (10-30 microg/ml for 48 h) with these labeled lipoproteins and the T1 relaxivity of centrifuged pellets of these cells was determined by using an inversion recovery sequence on a 1.5T scanner. These results were compared to control measurements made from foam cell cultures fed unlabeled lipoproteins (n=7). RESULTS: Measured T1 relaxation times of the cells fed the MnMeso-LDL (443.3 +/- 51.8 ms) was significantly different from the T1 relaxivity obtained from cells fed unlabeled lipoproteins (661.3 +/- 60.9 ms). These findings indicate that the amount of contrast bound to the constructed lipoproteins is sufficient to produce measurable MR signal changes noninvasively. CONCLUSIONS: The study results support the feasibility of future in vivo MR experiments with labeled lipoproteins to assess lipoprotein kinetics in the vessel wall, which will hopefully provide a means of detecting early atherosclerotic disease.

Animals↗
PubMed1992

MR imaging for measurements of ventricles and cerebral cortex in postnatal rats (H-Tx strain) with progressive inherited hydrocephalus.

As part of a wider investigation on brain structure and function in young rats with inherited hydrocephalus, this study was undertaken to develop a technique to monitor, and quantify, progressive changes in ventricle and cortical dimensions in hydrocephalic rats in vivo. Magnetic resonance images were obtained with a T1-weighted protocol and a multislice variant of the inversion recovery sequence which displayed optimal contrast between cerebrospinal fluid and brain parenchyma. Rats were imaged at 7, 14, and 21 days after birth by taking 10 contiguous 2.0-mm coronal slices. Area and distance measurements were taken from the displayed images, enabling calculation of ventricle volumes, cortical length, and cortical thickness. The lateral ventricle volume, which was already 100-fold larger than control at 7 days, increased to over 1000 mm3 at 21 days. The anterior-posterior length of the cortex was up to 27% larger in hydrocephalics and the cortical mantle was up to 75% thinner, particularly in the posterior cortex. Subsequent fixation and histological sectioning of two 21-day-old rats showed that the smaller dimensions, which were obtained from analysis of the sections, could be accounted for by shrinkage of the tissue during dehydration and wax embedding.

Aging↗
PubMed1995

Brain magnetic resonance imaging in non-alcoholic cirrhosis.

Twenty-six patients with stable non-alcoholic cirrhosis and normal neurological examination were investigated by brain MRI (inversion recovery sequences) and compared with 16 controls. Brain MRI findings were correlated with the clinical and metabolic status of the patients and analysis of variance and, when necessary, co-variance was performed. Five of the patients (19%) and all 16 controls showed no MRI changes. Twelve patients (46%) showed moderately high signal in the globus pallidus (score 1), and nine (35%) very high signal (score 2). Analysis of variance showed that age was the only significant variable (P = 0.038). Analysis of co-variance after adjustment for age showed that high pallidal signal was correlated only to ammonia level (P = 0.02) but not to any other clinical or biological parameter. We conclude that T1 high intensity pallidal signal is common in non-alcoholic cirrhosis even when neurological examination is normal, but its significance remains unclear.

Adult↗
PubMed1986

Evaluation of the prostate by magnetic resonance imaging.

Forty-seven male patients with suspected prostatic disease underwent magnetic resonance imaging (MRI) of the pelvis on a Picker resistive magnet operating at 0.15 T; 33 had histologically proved adenocarcinoma, 12 benign prostatic hypertrophy, 1 a transitional cell carcinoma, and 1 a seminoma. Eleven normal subjects also were included in the study. The study attempted to (1) define the MRI characteristics of the normal prostate, benign prostatic hypertrophy, and prostatic adenocarcinoma, (2) evaluate various pulse sequences in imaging the prostate, and (3) compare MRI findings with clinical, pathologic, and computed tomography results. Various pulse sequences, including inversion recovery and spin-echo with short and long TE and TR, were used. MRI was sensitive in detecting intracapsular and extracapsular prostatic disease. The finding of inhomogeneous signal texture throughout the gland was a sensitive but nonspecific finding for adenocarcinoma. A focal nodule with prolonged T1 and T2 relaxation times was the most specific MRI finding for adenocarcinoma. Extracapsular spread of neoplasm was often demonstrated, and because of its superior soft-tissue contrast ability, MRI was more accurate than computed tomography in delineating extracapsular extension.

Adenocarcinoma↗
PubMed1987

In vivo estimation of relaxation processes in benign hyperplasia and carcinoma of the prostate gland by magnetic resonance imaging.

Tissue characterization for separating malignant from benign tissue is a clinically very important potential of magnetic resonance imaging (MRI). In this study quantitative determination of T1- and T2-relaxation processes was accomplished in five healthy volunteers, 10 patients with benign hyperplasia of the prostate gland and eight patients with prostatic carcinoma. Histological verification was obtained in all the patients. The measurements were performed on a wholebody MR-scanner operating at 1.5 T using six inversion recovery sequences (TR = 4000 msec) for T1-determination and a 32 spin-echo sequence (TR = 3000 or 2000 msec) for T2-estimation. The T1-relaxation curves all appeared monoexponential, whereas the T2-curves in most cases showed a multiexponential behaviour. A considerable overlap of the relaxation curves was seen. Consequently, we found no statistically significant differences between the T1- or the T2-relaxation times of the three groups investigated. It is concluded that tissue characterization based on relaxation time measurements with MRI does not seem to have a clinically useful role in prostatic disease.

Adult↗
PubMed1992

In vivo evaluation of the reproducibility of T1 and T2 measured in the brain of patients with multiple sclerosis.

The precision (reproducibility) of relaxation times derived from magnetic resonance images of patients with multiple sclerosis (MS) were investigated. Measurements of 10 MS patients were performed at 1.5 T on two occasions within 1 wk. T1 and T2 was measured using a partial saturation inversion recovery sequence (6 points) and a Carr-Purcell-Meiboom-Gill phase alternating-phase shift multiple spin-echo sequence with 32 echoes. Regions of interest (ROI) were placed both in apparently normal white matter and plaques. The precision (+/- 1.96 SD) and the confidence intervals for T1 and T2 for white matter and plaques were calculated. The precision of T1 for white matter and plaques was respectively +/- 94 msec and +/- 208 msec. The precision of T2 for white matter and plaques was respectively +/- 18 msec and +/- 26 msec. For all measurements the coefficient of variation was about 9%. Judging from our own study and others as well, a precision better than 10% for T1 and T2 would seem unrealistic at present.

Adult↗
PubMedDate not supplied

The MR appearance of endovascular embolic agents in vitro with clinical correlation.

A spectrum of embolic agents including PVA, avitene, gelfoam, ethanol, IBCA, silicone microspheres, metal and platinum coils, and balloons containing contrast of HEMA were imaged in vitro at 0.3 Tesla using spin echo, gradient echo, and inversion recovery sequences. Signal intensities associated with these agents and changes created by addition of blood are presented. The in vitro model is also correlated with clinical MR material. Recognition of embolic materials is important to avoid confusion with persistent flow void, hemorrhage, or thrombus.

Adult↗
PubMed2005

Relation of end-diastolic wall thickness and the residual rim of viable myocardium by magnetic resonance imaging to myocardial viability assessed by fluorine-18 deoxyglucose positron emission tomography.

End-diastolic wall thickness (EDWT) and thickness of the residual non-contrast-enhanced myocardial rim have been suggested as markers for the assessment of myocardial viability by cardiovascular magnetic resonance (CMR) imaging. This study compared these parameters as derived from contrast-enhanced CMR images for the prediction of myocardial viability as determined by fluorine-18 deoxyglucose positron emission tomography (FDG-PET). Twenty-two patients with ischemic cardiomyopathy (ejection fraction 31 +/- 11%) were investigated. For contrast-enhanced CMR imaging, a standard inversion-recovery sequence was used. FDG-PET was performed using a hyperinsulinemic-euglycemic clamp. Data were analyzed with a 17-segment model. Of 146 severely dysfunctional segments, 112 were assessed as viable and 34 as nonviable by nuclear imaging. Using receiver-operator characteristic analysis, areas under the curve were 0.95 for unenhanced myocardial rim (95% confidence interval 0.92 to 0.98) and 0.86 for EDWT (95% confidence interval 0.80 to 0.93, p <0.001 vs unenhanced myocardial rim) for the prediction of viability as assessed by FDG-PET. Cutoffs of 5.4 mm for EDWT and 3.0 mm for unenhanced myocardial rim were found to optimally differentiate viability by FDG-PET. In 25 segments with divergent results, 94% of segments with an EDWT < or =5.4 mm and an unenhanced myocardial rim >3.0 mm were scored as viable by FDG-PET, whereas 57% of segments with an EDWT >5.4 mm and an unenhanced myocardial rim < or =3.0 mm were scored nonviable with the reference technique. In conclusion, unenhanced myocardial rim is superior to EDWT for the prediction of myocardial viability as determined by FDG-PET and may be clinically useful for assessment of myocardial viability in patients with ischemic cardiomyopathy and regional wall thinning.

Cardiomyopathies↗
PubMed2006

Delayed gadolinium-enhanced cardiac magnetic resonance in patients with chronic myocarditis presenting with heart failure or recurrent arrhythmias.

OBJECTIVES: We evaluated the effectiveness of contrast-enhanced cardiac magnetic resonance (CE-CMR) in detecting chronic myocarditis (CM). BACKGROUND: Chronic myocarditis represents a common evolution of acute myocarditis. Although CE-CMR has been revealed to be effective in identifying areas of myocardial damage in acute myocarditis, its role in the diagnosis of chronic myocardial inflammation has not yet been investigated. METHODS: Twenty-three patients with CM underwent CE-CMR and endomyocardial biopsy (EMB). Chronic myocarditis was defined by the presence of: 1) chronic (>6 months) heart failure symptoms and/or repetitive ventricular arrhythmias; 2) no history of recent flu-like symptoms or infections; and 3) histologic evidence of active myocarditis (AM) or borderline myocarditis (BM) according to Dallas criteria. Contrast-enhanced cardiac magnetic resonance included black-blood T2-weighted (BBT2w) images without and with fat saturation and delayed three-dimensional T1 turbo field-echo inversion-recovery sequences obtained 15 min after gadolinium injection. RESULTS: Histology showed AM in 14 patients and BM in 9 patients. FatSat BBT2w revealed the presence of edema in five (36%) patients with AM but not in BM patients. Areas of late enhancement (LE) were observed in 12 (84%) subjects with AM and in 4 (44%) cases with BM. A mid-wall LE pattern was the most frequent finding in both groups while a subepicardial distribution of LE was observed only in patients with AM. CONCLUSIONS: Contrast-enhanced cardiac magnetic resonance identified areas of myocardial inflammation in up to 70% of patients with biopsy-proven CM. We suggest that CE-CMR may be a useful non-invasive diagnostic tool in patients with CM, and it may indicate and even guide the execution of left ventricular EMB with relevant prognostic and therapeutic implications.

Adult↗
PubMed2006

Three-dimensional cylindrical X-band ESR imaging by a combined pulsed gradient Fourier and static gradient projection reconstruction method.

Static gradient electron spin echo projection reconstruction imaging is favourable for X-band material science applications requiring temperature variation with a metal cryostat. To prevent imaging artefacts due to the high conduction electron diffusion coefficient in the preferred conduction direction of quasi-one-dimensional conductors, only pulsed gradient phase encoding for that direction can be tolerated. We present results of an appropriate cylindrical imaging scheme combining both methods. Conduction electron spin density images with 13 x 13 x 17 microm(3) volume element size or spin-lattice relaxation time images with inversion recovery sequence and 13 x 13 x 68 microm(3) volume element size are presented for fluoranthene radical cation salt single crystals of typical sizes of 0.4 x 0.4 x 1 mm(3).

Journal Article↗
PubMed1988

Further technical development in magnetic resonance imaging of the brain in children.

Further technical developments implemented in magnetic resonance imaging (MRI) of the brain in children are described. These include the use of longer data collection periods, T2-dependent field echoes, susceptibility mapping, short inversion time inversion recovery sequences, very long echo time spin-echo sequences, and phase mapping techniques to detect tissue perfusion. These techniques are illustrated in selected cases and have increased the range of options available in MR examinations of children.

Brain↗
PubMed1999

Impact of the lysine-188 and aspartic acid-189 inversion on activity of trypsin.

The impact of the charge rearrangement on the specificity of trypsin was tested by an inversion of sequence K188D/D189K maintaining the integrity of the charges of the substrate binding pocket when switching their polarity. In native trypsin, aspartate 189 situated at the bottom of the primary substrate binding pocket interacts with arginine and lysine side chains of the substrate. The kinetic parameters of the wild-type trypsin and K188D/D189K mutant were determined with synthetic tetrapeptide substrates. Compared with trypsin, the mutant K188D/D189K exhibits a 1.5- to 6-fold increase in the Km for the substrates containing arginine and lysine, respectively. This mutant shows a approximately 30-fold decrease of its k(cat) and its second-order rate constant k(cat)/Km decreases approximately 40- and 150-fold for substrates containing arginine and lysine, respectively. Hence, trypsin K188D/D189K displays a large increase in preference for arginine over lysine.

Animals↗
PubMed1975

Preparation and antigenic properties of androsterone-7-BSA conjugate.

The 7-carboxymethoximino derivative of androsterone (1) has been prepared from dehydroisoandrosterone-17-ethyleneketal by a sequence involving inversion at C-3, introduction of a carbonyl at C-7, and reduction of the double bond at C-5. The substance was condensed with BSA by the carbodiimide procedure to afford a conjugate which produced anti-androsterone antiserum in innoculated rabbits. The antiserum is sufficiently active to be useful in radioimmunoassay procedures.

Androsterone↗
PubMed1999

Direct identification of ventrointermediate nucleus of the thalamus on magnetic resonance and computed tomography images.

OBJECTIVE: The ventro-intermediate (Vim) nucleus of the thalamus is a commonly used target for the treatment of tremor. The thalamic fasciculus contains myelinated fibers, believed to play a role in the generation of tremor, that converge into a dense bundle at the inferior aspect of the Vim nucleus, making it visible on magnetic resonance (MR) and computed tomography (CT) images. This structure, therefore, can be visualized directly and targeted for thalamotomy. METHODS: Thalamotomies were performed on nine patients (who have a follow-up of 13-23 months) with parkinsonian and essential tremors using MR and CT images. The tremor target was hypointense on MR images obtained in inversion recovery sequence and hypointense on CT images. It was therefore visualized, directly targeted, and probed. Stimulation studies were done to physiologically confirm accuracy of the probe placement and then a radiofrequency lesion was made. RESULTS: Stimulation of the target identified as the Vim nucleus on MR and CT images produced responses similar to those expected from the Vim nucleus. After this site was lesioned tremor disappeared in all nine patients. CONCLUSION: The Vim nucleus of the thalamus is visible on MR and CT images. Destruction of this target abolishes parkinsonian and essential tremors.

Aged↗