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PubMed1985

[Magnetic resonance imaging of the pelvis. Methodological aspects].

Multiparametric choice is needed in Magnetic Resonance Imaging (MRI). In addition to matrix definition, section thickness, accumulation number, the repetition time TR, the echo time TE (for the spin echo technique) and the plane selection are of great importance. In pelvic examination, information supplied by T1 and by T2 weighted images is complementary. So, comparison between the three dimensional sections is of great interest. Although long acquisition times could, in theory, provide better images and therefore more clinical information, the patient comfort must be considered in choosing a reasonable examination time. We believe that it is possible, without great loss of information, not to make inversion recovery sequences. Using a 0.5 T superconducting magnet, sequences were done with TR of 1,200 ms for T2 weighted images and two echoes with TE of 40 or 50 ms. Twice repeated sequences (for averaging purpose) and 256(2) matrix (with a 42 cm field diameter) seem to be well adapted to MRI clinical applications.

Female↗
PubMed1983

[Visualization of cerebellopontine angle diseases by nuclear magnetic resonance imaging].

The preliminary results from the clinical use a prototype whole body nuclear magnetic resonance (NMR) machine constructed by Toshiba Inc. are presented. Cranial NMR scans were performed on more than 30 cases with broad spectrum of neurologic diseases using saturation-recovery and inversion-recovery sequences with a field strength of 1500 Gauss. Selective excitation sequence was used for the slice selection and filtered backprojection was used to reconstruct the images. They were displayed on a 256 X 256 matrix as 12 mm thick sections. Data acquisition time varied between 3 and 12 minutes. Our initial experiences with six cases harboring cerebellopontine angle lesions disclosed advantages and disadvantages of NMR imaging in comparison with X-ray CT. The advantages were the absence of linear artifacts from the surrounding bone, the marked gray-white matter differentiation, and the variety of tomographic planes available. The disadvantages included the lack of bone detail, the lack of visualization of the major intracranial vessels, and the long time required for scanning (several minutes per slice). Although much continued evaluation is necessary, NMR seems to have vast potential as a diagnostic tool.

Adult↗
PubMedDate not supplied

[Analysis of the reaction between nerve structures of the auditory, sensomotor, and visual zones of the cat neocortex according to summated evoked potentials to heteromodal stimuli].

Short-latency EPs in the auditory, sensorimotor and visual cat neocortical areas were analyzed in chronic experiments with interaction of two stimuli of different modalities (click plus electro-cutaneous stimulation of the circular eye muscle). In the auditory cortex the "click plus current" combination caused a blockade of the EP to the electric stimulation in the case of short intervals; with an inverse stimuli sequence "current plus click", and with all intervals, the EPs to clicks were recorded in an unreduced form. In the sensorimotor and visual areas, after both sequences of stimuli the EPs to the second stimulus were commensurable with the control ones. A conclusion is made on a difference in organization of sensory inputs for sound and electro-cutaneous stimuli of the studied cortical areas: with chosen stimuli intensities, in the auditory cortex, as compared to the visual and sensorimotor areas, there is a more pronounced interaction of two types of afferentation.

Animals↗
PubMed1994

Temporal lobe epilepsy: the various MR appearances of histologically proven mesial temporal sclerosis.

PURPOSE: To determine the frequency of appearance of various MR signs in mesial temporal sclerosis, to determine the optimal scanning planes for their visualization, and to propose a histologic explanation for the diminished demarcation between gray and white matter in the temporal lobe, a frequent MR finding in patients with mesial temporal sclerosis. METHODS: MR scans of 14 surgically treated patients with epilepsy and histologically proven mesial temporal sclerosis were assessed for the presence of six features: feature 1, high signal intensity in the hippocampus; 2, reduced hippocampal size; 3, ipsilateral atrophy of the hippocampal collateral white matter; 4, enlarged temporal horn; 5, reduced gray-white matter demarcation in the temporal lobe; and 6, decreased temporal lobe size. RESULTS: Feature 1 was present in 14 patients and was best appreciated on the T2-weighted images in planes parallel to the long axes of the hippocampi. Feature 2, present in 12 patients, and feature 6, present in 9 patients, were optimally seen in the coronal planes and on the inversion-recovery sequences in particular. Feature 3, present in 12 patients, was optimally seen on the coronal T2-weighted images. Feature 4, seen in 11 patients, was equally well seen in all planes (transverse, coronal, and parallel to the long axes of the hippocampi). Feature 5, seen in 10 patients, was best appreciated on the T2-weighted images in the planes of the long axes of the hippocampi. Histologic investigation of the temporal lobe white matter in the 10 patients with feature 5 demonstrated on the MR scan showed abnormalities in 7 cases. Oligodendroglia cell clusters were found in 6, with concomitant corpora amylacea in 1 case and perivascular macrophages with pigment a sole finding in another case. CONCLUSION: Of the six features found in cases of mesial temporal sclerosis on MR, increased hippocampal signal intensity is the most consistent. A decreased gray-white matter demarcation in the temporal lobe parenchyma is also a frequent feature of this disease. A combination of multiple scanning planes results in an optimal demonstration of lesions.

Adolescent↗
PubMed1993

Fe(III)-EHPG and Fe(III)-5-Br-EHPG as contrast agents in MRI: an animal study.

The development of specific agents for hepatobiliary magnetic resonance imaging (MRI), iron (III) ethylenebis-(2-hydroxyphenylglycinate) [Fe(EHPG)-] and its derivative iron (III)-N, N' ethylenebis[5-bromo-2-hydroxyphenyl)-glycinate] [Fe(5-Br-EHPG)-] was investigated. Test procedures included method of synthesis, identification, and a test for purity, lipophilicity, toxicity, relaxivity, biodistribution and animal MRIs. Free EHPG and free Fe3+ were undetectable in the purity test. The partition coefficient for the lipophilicity of Fe(EHPG)- was 0.007 and for Fe(5-Br-EHPG)- it was 1.785. The acute toxicity test of Fe(EHPG)- in mice revealed that the LD50 dose of Fe(EHPG)- was 8 mmol/kg. Their relaxivity values were 1.167 and 0.780 s-1mM-1 in an agarose gel system and 1.313 and 0.725 s-1mM-1 in an aqueous solution, respectively. Biodistribution was performed with 59Fe(EHPG)- in anesthetized dogs. There was 1.097% to 1.19% contrast excretion through the opened common bile duct and 54.29% to 61.45% through the urinary tract in a six-hour period. After six hours, the residual contrast agent was only evident in the kidney and liver. The MRIs of dogs with intravenous contrast administration showed significant opacification of the common bile duct within a 10-minute period. Complete opacification of the biliary system could be identified within 1.5 hours. There was no significant difference in the enhancement effect between the inversion recovery sequence and T1-weighted spin echo sequence. The change in signal intensity of the hepatobiliary system on MRIs was similar between Fe(EHPG)- and Fe(5-Br-EHPG)-. The recommended administration dose was 0.083 mmol/kg for both contrast agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

MR imaging of edematous limbs in lymphatic and nonlymphatic edema.

MR imaging reflects the water content of various tissues. To evaluate the role of MR imaging in the diagnosis of edema, various types of edema were examined with MR imaging. MR imaging of edematous limbs was performed on 60 patients (lymphatic edema 48, nonlymphatic edema 12) using T1- and T2-weighted spin-echo and short inversion time inversion recovery sequences. Thickness and signal intensity of the cutis, subcutis and subfascia were evaluated in the images. In all 48 cases with lymphatic edema, trabecular structures suggesting dilated collateral lymphatic vessels were observed in the swollen subcutis. Two cases with nephrotic syndrome showed similar findings. In 6 cases with venous edema, fatty intensity was found in the subfascia. In the remaining 4 cases, the subcutis exhibited only water intensity. MR imaging is a potential contributor to the diagnosis of various edematous diseases.

Adolescent↗
PubMed1993

[Nuclear magnetic tomography of the meniscus in asymptomatic probands].

In 82 asymptomatic subjects aged 8-62 years we evaluated the menisci by MRI [1.0 tesla; SE (spin-echo) 700/20, PS (partial saturation) 500/10, STIR (Short-Time-Inversion-Recovery-Sequence) 1600/130/30]. The meniscus was graded by means of a standard classification (grades 0-4). In SE sequences we found grade 0 in 45.5% of all cases, grade 1 in 33.2%, grade 2 in 16.1%, grade 3 in 4.5%, and grade 4 in 0.7%. In PS sequences we found grade 0 in 23.9%, grade 1 in 27.5%, grade 2 in 31.5%, grade 3 in 15.9%, and grade 4 in 1.1%. In STIR sequences we found grade 0 in 56%, grade 1 in 25.4%, grade 2 in 11.1%, grade 3 in 6%, and grade 4 in 1.6%. Correlation of meniscus degeneration with subjects' age showed relation of meniscus degeneration with subjects' age showed relation of meniscus degeneration with subjects' age showed an increase of grade 3 and grade 4 lesions with advancing age. Subjects older than 50 years presented grade 3 and 4 lesions in the SE sequence in 28.5% of the cases, in PS sequences in 40.7% of the cases, and in STIR sequences in 25% of the cases. MRI shows meniscal lesions in a significant proportion of asymptomatic patients, especially among subjects older than 50 years. The orthopedic surgeon has to test whether the clinical findings in patients with knee complaints coincide with the results of MRI.

Adolescent↗
PubMed1993

Inversion of carcinogen-promoter sequence: effects on mouse skin tumorigenesis and cellular growth kinetics.

To stimulate conditions wherein humans might be exposed to tumor promoters prior to carcinogenic stimulus, female S/RV Cri mice were treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) for 10 weeks followed by a sc injection of 3-methylcholanthrene (MCA). Six weeks after MCA administration, tissue alterations in different skin layers were analysed by histology, morphometry and autoradiography. Multiple application of TPA prior to MCA injection induced moderate to marked epidermal hyperplasia with an increase in the thickness of nucleated cell layers and stratum granulosum. As compared to control, number of basal and suprabasal cells per 7.5 mm of interfollicular epidermal (IFE) length was significantly higher in the skin of animals treated with TPA + MCA. The hyperplastic response was accompanied by a significant increase in epidermal mitotic activity, number of cells in DNA-synthetic phase in epidermis, dermis and subcutis and subepidermal mast cell population. Histological observations of induced tumors revealed a significant increase in the incidence of carcinomas and mixed neoplasms of epithelial and mesenchymal histogenesis. The findings suggest that stimulated cellular proliferation in different layers of mouse skin by TPA treatment prior to MCA injection may play a major role in enhanced expression of histogenetically distinct tumors.

Animals↗
PubMed1997

Cystlike white matter lesions in tuberous sclerosis.

PURPOSE: To investigate the presence of small cystlike structures in the cerebral hemispheric white matter on MR images of patients with tuberous sclerosis. METHODS: The MR images of 18 consecutive patients with tuberous sclerosis were reviewed retrospectively. RESULTS: Eight of the 18 patients were found to have cystlike structures in the cerebral white matter. The signal intensity of these lesions was isointense with cerebrospinal fluid on T1-, proton density-, and T2-weighted images. Four patients were imaged with a fluid-attenuated inversion recovery sequence, which in each case also showed fluid-type signal in these areas. Three of the patients had CT for correlation, and these scans supported the diagnosis of cystic lesions. Cysts ranged in number from one to 12 per patient and were usually smaller than 1 cm. The most common location was adjacent to the occipital horn or trigone of the lateral ventricle (six of eight patients). Less frequent sites were near the frontal horns, in the corpus callosum, and in the deep white matter near the body of the lateral ventricle. Cysts in five patients were either immediately adjacent to a cortical tuber or in the center of a white matter dysplastic lesion. A cyst in one patient had septa, and none of the cysts enhanced. CONCLUSIONS: Cystlike structures in the cerebral hemispheric white matter were seen on the MR images of 44% of 18 patients with tuberous sclerosis. Whether these findings represent cystic degeneration of dysplastic tissue or are unrelated to the disease process of tuberous sclerosis is unknown. More than one pathogenesis may exist.

Adult↗
PubMed1998

MR of cerebral malaria.

In three cases of cerebral malaria, MR imaging disclosed either cortical infarcts (one case) or hyperintense areas of white matter (two cases) on T2-weighted and fluid-attenuated inversion-recovery sequences. These white matter abnormalities were, in one case, sharply limited, symmetrical, hyperintense, and unenhanced; in the other case, they were diffuse, hyperintense, and had a more limited focus. The diffuse hyperintensity was probably due to edema, whereas focal lesions were probably associated with gliosis.

Adolescent↗
PubMed1998

The effect of section thickness on MR lesion detection and quantification in multiple sclerosis.

BACKGROUND AND PURPOSE: The purpose of our study was to investigate the effect of section thickness on MR detection of brain lesion volume and measurement precision in patients with multiple sclerosis (MS). METHODS: Eight subjects with known MS were studied on a 1.5-T MR system. We used a 3D fast fluid-attenuated inversion-recovery sequence to obtain contiguous axial brain images at section thicknesses of 5 mm, 3 mm, and 1 mm. Two sets of images were acquired at each section thickness during two sessions, between which the patient was removed from the scanner. Lesion volumes were measured at each section thickness using a semiautomated local thresholding technique. RESULTS: We found that progressive reduction in section thickness led to detection of smaller lesions, resulting in a significant (8%) increase in lesion volume on MR images as section thickness was reduced from 5 mm to 3 mm. However, despite a further increase in lesion detection at a section thickness of 1 mm, this did not result in an increase in total lesion volume. This finding indicates that the relationship between section thickness and lesion volume on MR images is not linear. Scan-rescan reproducibility was improved by reducing section thickness, at the cost of increased analysis time. CONCLUSION: This study shows that acquisition of very thin sections increases the sensitivity and precision of MS lesion measurement. Serial studies assessing lesion changes over time are needed to define the impact of this increase on sample size requirements for MS treatment trials.

Adult↗
PubMed1989

White matter lesions: role of spin density in MR imaging.

To study the effect of hydrogen spin density (N[H]) on magnetic resonance (MR) image contrast in white matter disease of the brain, T1, T2, and N[H] values were determined for normal white matter and idiopathic white matter lesions (IWMLs) in 21 patients by using multiple spin-echo (SE) sequences. T1 values of IWMLs were significantly greater than those of normal white matter in all patients studied, and T2 values of IWMLs were significantly greater in 20 of 21 patients. N[H] values of IWMLs were greater in 20 of 21 patients, with statistically significant differences from those of normal white matter in 17 of those 20 patients. Averaged over all 21 patients studied, N[H] values of IWMLs were 20% higher than N[H] values of normal white matter. The effect of unequal N[H] values on contrast between IWMLs and normal tissues is to reduce contrast on short SE sequences with a short repetition time (TR) and a short echo time (TE), while enhancing contrast between IWMLs and normal tissues on long TR/TE SE sequences. Elevated N[H] values in IWMLs have a minimal effect on contrast in conventional inversion-recovery (IR) sequences but substantially enhance contrast between IWMLs and normal brain tissues in short inversion time IR sequences.

Brain↗
PubMed1989

Short TI inversion-recovery imaging of the liver: pulse-sequence optimization and comparison with spin-echo imaging.

Magnitude-reconstructed short inversion-time (TI) inversion-recovery (IR) sequences have the advantage of reducing the signal of fat while providing additive T1 and T2 contrast. A double-echo short TI IR sequence was implemented to offer different degrees of T1- and T2-dependent image contrast. In 50 consecutive patients with proved liver tumors (30 metastases, 13 hemangiomas, seven other primary liver tumors), images obtained with a double-echo IR sequence at a repetition time (TR) of 1,500 msec, echo time (TE) of 30 and 60 msec, and TI of 80 msec (TR/TE/TI = 1,500/30, 60/80) were compared with those obtained with spin-echo (SE) sequences at a TR of 275 msec and a TE of 14 msec (TR/TE = 275/14) and 2,350/60, 120, 180. Metastases-liver contrast-to-noise ratios were highest at SE 275/14, followed by IR 1,500/30/80 and SE 2,350/180. IR 1,500/30/80 and SE 275/14 sequences consistently showed higher sensitivity for the detection of metastases than T2-weighted SE sequences. Differential diagnosis of benign and malignant lesions was more reliable with T2-weighted SE sequences than T2-weighted short TI IR sequences.

Adult↗
PubMed1990

The basis of high resolution separation of small DNAs by asymmetric-voltage field inversion electrophoresis and its application to DNA sequencing gels.

We have previously shown that asymmetric-voltage field inversion electrophoresis produces more uniform separation for fragments between 1 and 50 kilobases (kb) than other modes of pulsed field gel electrophoresis. We now report on the basis of this phenomenon. As in conventional electrophoresis, the pulsed field mobility of DNAs between 1 and 50 kb varies with voltage in a size dependent manner. The complex migration pattern obtained with asymmetric-voltage field inversion electrophoresis reflects the difference between the mobilities of each sized fragment under the conditions used for the forward and reverse fields. We have applied this technique to DNA sequencing gels and find improvement in resolution for single-stranded fragments in polyacrylamide gels.

Base Sequence↗
PubMed1994

MR assessment of brain maturation: comparison of sequences.

PURPOSE: To evaluate the role of short-inversion-time inversion-recovery (STIR) sequences in assessment of brain maturation. METHODS: Twenty-seven infants and young children with normal neurologic development were examined by 1.5-T MR using a circularly polarized head coil. Axial T1-weighted and T2-weighted and spin-echo and STIR images were obtained. Signal intensity of different anatomic structures at individual sequences was classified relatively to reference sites and temporal sequence of signal intensity was observed. RESULTS: Signal intensity changes on T1-weighted and T2-weighted spin-echo sequences occurred at ages described in various previous publications. On STIR images intensity changes became apparent at a time between T1-weighted and T2-weighted images. The advantages of the STIR sequence were improved assessment of myelination of subcortical cerebral white matter from 6 to 14 months and good contrast between white matter lesions and cerebrospinal fluid. CONCLUSION: Our results suggest that from 0 to 6 months myelination can be assessed best using a combination of T1-weighted and T2-weighted images; from 6 to 14 months a combination of T2-weighted and STIR images seems to be advantageous; after 14 months the use of only T2-weighted sequences is sufficient. After 14 months STIR images may be useful in detecting small periventricular white matter lesions or in cases with retarded myelination and isointensity between gray matter and white matter.

Brain↗
PubMed1982

Genetic analysis of the mechanism of the Salmonella phase variation site specific recombination system.

Phase variation, the alternation of expression of flagellar antigens H1 and H2, in Salmonella typhimurium is mediated by site specific inversion of a 995 bp DNA segment of the chromosome. Hin, a protein encoded within the 995 bp segment, is thought to catalyze the recombination reaction between 14 bp inverted repeats flanking the 995 bp segment. By comparison of the relative rates of inversion of two different plasmids containing the H2 inversion segment flanked by different sequences, we conclude that the sequences adjacent to the inversion segment affect the rate of inversion. Homologous pairing of the repeats is important in H2 inversion since the orientation of the repeats on the host molecule(s) determines the result of the recombination reaction. The presence of the hin gene mediates the fusion of two plasmids when each contains one of the 14 bp repeat sequences. When the 14 bp sequences are direct repeats on a single molecule the sequence between them is deleted. These results support the hypothesis that the H2 inversion system functions by homologous, conservative, site specific recombination which is similar to the systems found associated with TnA transposons and temperate bacteriophage.

Bacterial Proteins↗
PubMed2005

Noise reduction in multi-slice arterial spin tagging imaging.

Attenuating the static signal in arterial spin tagging (ASSIST) was initially developed for 3D imaging of cerebral blood flow. To enable the simultaneous collection of cerebral blood flow and BOLD data, a multi-slice version of ASSIST is proposed. As with the 3D version, this sequence uses multiple inversion pulses during the tagging period to suppress the static signal. To maintain background suppression in all slices, the multi-slice sequence applies additional inversion pulses between slice acquisitions. The utility of the sequence was demonstrated by simultaneously acquiring ASSIST and BOLD data during a functional task and by collecting resting-state ASSIST data over a large number of slices. In addition, the temporal stability of the perfusion signal was found to be 60% greater at 3 T compared to 1.5 T, which was attributed to the insensitivity of ASSIST to physiologic noise.

Adult↗
PubMed1997

MR cholangiopancreatography at 0.5 T with a 3D inversion recovery turbo-spin-echo sequence.

The objective of this study was to assess the diagnostic value of magnetic resonance cholangiopancreatography (MRCP) at 0.5 T. The MRCP technique was performed in 28 patients with symptomatology referrable to the biliary system. A three-dimensional (3D) inversion recovery turbo-spin-echo (TSE) sequence was used to create 3D reconstructions of the bile ducts. Dilation of the biliary tree or pancreatic duct in 23 patients due to tumor, calculi, or strictures was depicted with excellent contrast resolution. The approximate level of obstruction and all calculi were accurately predicted by MRCP. In another 3 patients no cause was found for the biliary dilatation. In the last 2 cases no abnormalities were found by either MRCP or endoscopic retrograde cholangiopancreatography (ERCP). The MRCP technique at 0.5 T is an accurate method for the assessment of pathology of the biliary tree.

Biliary Tract Diseases↗