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Biomedical subjects

M Essig

Publications and source records attributed to M Essig.

At least 127 records · Page 7Linked to original sources
PubMed1996

Vascular MR contrast enhancement in cerebrovascular disease.

PURPOSE: To determine the significance of vascular enhancement in stroke patients with and without permanent neurologic deficit. METHODS: We prospectively studied two groups of patients with spin-echo MR imaging before and after injection of gadopentetate dimeglumine. In the patients in group 1 (12 women, 22 men; age range, 32 to 76 years), who had permanent neurologic deficit caused by recent ischemic brain infarction, we obtained 3 to 13 serial MR images during follow-up examination. Group 2 consisted of 26 patients (14 women, 12 men; age range, 54 to 81 years) with transient neurologic deficit caused by angiographically proved high-grade stenosis or occlusion of the internal carotid artery. RESULTS: Vascular enhancement was present in 59% of patients in group 1 and in 65% of patients of group 2. In group 1, the frequency of vascular enhancement declined steadily over several weeks, but it was still present in single cases even after 3 months. Vascular enhancement correlated positively with the extent of brain infarction in group 1 and with the degree of carotid stenosis in group 2. CONCLUSION: Vascular enhancement as shown by MR imaging may herald ischemic brain infarction and could persist over several weeks in areas that show collateral flow after infarction has occurred.

Adult↗
PubMed1996

[Blood volume changes after the radiotherapy of the central nervous system].

BACKGROUND: The pathogenesis of late delayed radiation damage in normal brain tissue is most likely due to damage to the vascular endothelium. The mitotic activity of gliomas was shown to correlate with the tumor induced angiogenesis. Dynamic susceptibility contrast MR imaging (DSC MRI) allows the measurement of the cerebral hemodynamics based on the indicator dilution theory. We describe theory and technique of the method and present our experience with blood volume measurements after irradiation of the CNS. METHODS: We established a double slice technique on a standard 1.5 T MR system without hardware modifications, which allows an absolute quantification of the blood volume in regions of interest (ROI) within the brain. Fifty-five T2* weighted double slice images were acquired before, during and after bolus injection of Gd-DTPA (0.1 mmol/kg in 5 sec.) using a SD FLASH sequence (simultaneous dual fast low angle shot, TR/TE1/TE2 31/16/25, flip angle 10 degrees). Concentration-time curves were calculated from the measured signal-time curves. Blood volume values in tissue were normalised and calculated in absolute values (ml/100 g) based on the knowledge of the arterial input function (AIF), which was measured in the brain supplying arteries. The whole procedure requires only 2 to 3 minutes, the time for post processing is about 15 to 20 minutes. RESULTS: Blood volume parameter images of representative cases demonstrate the blood volume changes after radiotherapy. A reduction in blood volume could be observed in normal brain tissue and low-grade gliomas, while recurrent tumors were accompanied by a local increase in blood volume. CONCLUSIONS: Radiation induced blood volume changes in the CNS can be measured using dynamic susceptibility contrast MR imaging. The measurements in normal brain tissue allow a functional in-vivo analysis of late delayed radiation reactions of the CNS. The definite value of intratumoral blood volume measurements for determination of the therapeutic success and for differentiation of recurrences versus radionecroses remains to be clarified in further studies.

Adult↗
PubMed1995

Renal mass and serum calcitriol in male idiopathic calcium renal stone formers: role of protein intake.

To determine whether chronic overconsumption of protein might increase renal mass and cause up-regulation of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D] production, 57 male recurrent idiopathic calcium stone formers (RCSF), 29 with hypercalciuria (HCSF; urinary calcium x V, > 7.50 mmol/day) and 28 with normocalciuria (NCSF), were compared with 15 healthy male controls (C) while consuming a free choice diet. Renal mass in RCSF was measured by the sum of the surface areas of right and left kidneys (square centimeters) on plain films of the abdomen by a computer-assisted sonic stylus; in C, renal mass was assessed sonographically. Serum intact PTH and 1,25-(OH)2D were measured radioimmunometrically. In HCSF, urinary phosphate x V (35.9 +/- 1.2 mmol/day) was higher than that in NCSF (29.3 +/- 1.3 mmol/day; P = 0.0009) or C (28.7 +/- 1.8 mmol/day; P = 0.005); urinary creatinine x V (16.5 +/- 0.5 mmol/day) was also higher in HCSF than in NCSF (15.0 +/- 0.5 mmol/day; P = 0.024) or C (13.8 +/- 0.6 mmol/day; P = 0.002). For identical blood levels of ionized calcium and phosphate, the 1,25-(OH)2D/PTH concentration ratio (an index of regulation of 1,25-(OH)2D production) was higher in HCSF (6.5 +/- 1.0) than in NCSF (4.0 +/- 0.3; P = 0.005). In addition, the sum of the surface areas of right and left kidneys was increased in HCSF (163.4 +/- 2.9 cm2) compared with that in NCSF (140.5 +/- 3.1 cm2; P = 0.0001), and it positively correlated with urinary phosphate x V (r = 0.429; P = 0.001) as well as with urinary creatinine x V (r = 0.294; P = 0.026); no such correlation was noted in C. Calcitriol levels were positively related to renal mass in RCSF (r = 0.316; P = 0.018), but not in C. Finally, urinary calcium x V positively correlated with the serum calcitriol/PTH concentration ratio only in RCSF (r = 0.388; P = 0.003). These findings suggest that protein overconsumption may cause an increase in renal mass and up-regulate calcitriol production in some male RCSF, an effect that would subsequently cause "idiopathic" hypercalciuria.

Adult↗
PubMed1995

[Diagnosis of recurrence of cervix carcinoma using dynamic MRI: correlation of pharmacokinetic analysis and histopathology].

PURPOSE: The aim of the study was to evaluate the value of dynamic magnetic resonance imaging (MRI) to classify suspect lesions into benign and malignant in patients previously treated for cancer of the cervix. MATERIALS AND METHODS: Eleven patients with 14 suspect lesions after treatment of cervical carcinoma were examined by dynamic contrast-enhanced MRI. The imaging findings were compared to the giant cross-section specimen as the reference standard. Computed tissue-specific enhancement parameters were obtained (pharmacokinetic mapping) and displayed as color-coded images. The regions of interest were retrospectively defined according to the pharmacokinetic images over the most suspect areas. Therein, the threshold values were determined that achieved the greatest overall accuracy and a low rate of false-positive results. RESULTS: Analysis of the lesions on T2-weighted images revealed sensitivity of 88%, specificity of 40%, and accuracy of 71%. Analysis of the dynamic MR data showed significantly shorter (p < 0.01) and stronger (p < 0.001) contrast media enhancement of malignant (n = 9) than benign lesions (n = 5). CONCLUSION: Pharmacokinetic mapping appears to yield important information for dividing suspect lesions into malignant and benign following treatment of cervical cancer.

Adult↗
PubMed1983

The effect of relaxin and progesterone on rat uterine contractions.

The effect of porcine relaxin on electrically stimulated in vitro contractions of isolated uterine horn segments from estrogen-pretreated immature rats was studied. Relaxin decreased the amplitude of contractions. A mean of 8.3 ng/ml of relaxin produced a 90% decrease in contraction amplitude. There was a minimal effect of 1.0 microgram/ml of progesterone on contraction amplitude. In vitro pretreatment of the isolated uterine segment with this dose of progesterone for 15 minutes did not significantly affect the dose of relaxin needed to decrease the amplitude of contractions. In contrast, pretreatment with progesterone for 45 minutes significantly decreased the concentration of relaxin needed to decrease contraction amplitude. Only 4.7 ng/ml of relaxin was needed to produce a 90% decrease in amplitude after progesterone pretreatment for 45 minutes (p less than 0.005). Relaxin and progesterone synergize in decreasing the amplitude of uterine contractions in vitro. A similar effect may occur in vivo.

Animals↗
PubMed1982

Stimulation of human sperm motility by relaxin.

Relaxin has recently been identified in human seminal plasma (SP). This investigation was undertaken to determine the effect of relaxin on sperm motility. Washed ejaculated human sperm were incubated with or without porcine relaxin. In a series of 37 normal specimens (motility greater than or equal to 60%) relaxin attenuated the decline in grade of forward progression and percentage of motile sperm. Relaxin had a similar effect on a series of 47 subfertile specimens (motility 30% to 40%). Endogenous relaxin may play a role in delaying declines of motility and grade of forward progress in ejaculated sperm.

Animals↗
PubMed1981

Hormone secretion by monolayer cultures of human luteal cells.

To be able to study the control mechanisms for human luteal function, a system was designed to maintain human luteal cells in culture. Collagenase dispersed cells of human corpora lutea of the menstrual cycle and pregnancy were maintained as monolayer cultures for 26 days. Progesterone (P) and relaxin (R) in culture media were measured by radioimmunoassay. Both menstrual cycle and pregnancy luteal cells secreted P for 26 days. hCG increased P secretion by menstrual cycle luteal cells, but not by pregnancy luteal cells. R was not detected in media of menstrual cycle luteal cell controls, nor in media of cells incubated with hCG. R was detected in media of pregnancy luteal cells for 6 days. Addition of hCG caused a significant increase in media R levels only on day 2 of culture. These studies show that human luteal cells can be maintained as viable monolayer cultures for at least 26 days and these cultures can be used to study control of human luteal function.

Cells, Cultured↗
PubMedDate not supplied

Assessment of tumor microcirculation: a new role of dynamic contrast MR imaging.

With the advances in MR techniques, information related to tumor microcirculation now can be obtained in the clinical setting. This information can be valuable in the assessment of tumor blood supply/oxygenation status and tumor response to therapy. In this article, we review the tracer-kinetic modeling for tumor microcirculatory parameters derived from dynamic contrast MR imaging and report several preliminary results from both an animal model and early experience with human tumors. Despite the application of different MR protocols and tracer-kinetic models, the initial results of these pioneer studies consistently support the role of MR-derived microcirculatory tumor parameters, in providing prognostic information to assess and predict the response of cancers to cytotoxic therapy.

Animals↗
PubMedDate not supplied

Pharmacokinetic MRI for assessment of malignant glioma response to stereotactic radiotherapy: initial results.

The purpose of this study was to assess the value of dynamic, contrast-enhanced MRI in patients with malignant glioma (a) to predict before stereotactic radiotherapy local tumor control, (b) to investigate temporal changes in tumor microcirculation after stereotactic radiotherapy, and (c) to analyze whether malignant glioma response may be predicted earlier by alterations in the tissue pharmacokinetics rather than in terms of tumor volume. Ninety MRI studies were performed of 18 patients with malignant glioma before and 6, 18, 26, 52, and 72 weeks after the end of stereotactic radiotherapy. The signal time courses of the contrast-enhanced tumors were analyzed using a pharmacokinetic two-compartment model that calculates for the parameter A, reflecting the degree of MRI signal enhancement [no units] and the exchange rate constant k21 [min(-1)]. Before radiotherapy, the amplitude A was significantly (P < .05) lower in patients with subsequent local tumor control (n = 8; mean A = .34 +/- .15) compared to patients without subsequent local tumor control (n = 10; mean A = .94 +/- .71). In the local tumor control group, early after stereotactic radiotherapy (at 6-18 weeks), there was a significant (P < .05) time-dependent decrease in the parameter k21, whereas there was still no alteration in the tumor volume. A low amplitude A before radiotherapy, combined with an early drop of k21 after stereotactic radiotherapy, reliably characterized the group of patients with subsequent tumor volume decrease. Our preliminary results suggest that two contrast-enhanced dynamic MR studies, one before and one early after stereotactic radiotherapy, offer important information on local tumor control within the first 6 to 18 weeks after stereotactic radiotherapy. Moreover, this response may be evidenced before tumor volume changes and provides a therapeutic window to broaden treatment options and to improve treatment outcome.

Brain↗
PubMedDate not supplied

Fast fluid-attenuated inversion-recovery (FLAIR) MRI in the assessment of intraaxial brain tumors.

This study demonstrates the value of a fast fluid-attenuated inversion-recovery (FLAIR) technique in the assessment of primary intraaxial brain tumors. Twenty-one patients with primary intraaxial brain tumors were examined by T2-weighted, proton-density-weighted fast spin echo, fast FLAIR, and contrast-enhanced T1-weighted spin echo using identical slice parameters. The images were evaluated using quantitative and qualitative criteria. Quantitative criteria were tumor-to-background and tumor-to-cerebrospinal fluid (CSF) contrast and contrast-to-noise ratio (CNR). The qualitative evaluation was performed as a multireader analysis concerning lesion detection, lesion delineation, and image artifacts. In the qualitative evaluation, all readers found the fast FLAIR to be superior to fast spin echo in the exact delineation of intraaxial brain tumors (P < .001) and the delineation of enhancing and nonenhancing tumor parts. Fast FLAIR was superior in the delineation of cortically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided a significantly better tumor-to-CSF contrast and tumor-to-CSF CNR (P < .001). The tumor-to-background contrast and tumor-to-background CNR of the fast FLAIR images were lower than those of T2-weighted spin-echo images but higher than those of proton-density-weighted spin-echo images. FLAIR images had more image artifacts influencing the image interpretation in only two patients. Signal hyperintensities at the ventricular border were present in 92% of the patients. They are common findings in fast FLAIR and should be included into the image interpretation.

Adult↗
PubMedDate not supplied

Interleaved gradient echo planar (IGEPI) and phase contrast CINE-PC flow measurements in the renal artery.

ECG-gated phase contrast (CINE-PC) flow measurements in the renal artery help to differentiate between low- and high-grade stenoses. Because conventional CINE-PC acquisitions with high temporal resolution require acquisition times of several minutes, respiratory motion results in a systematic overestimation of renal artery flow. With the use of an interleaved gradient echo-planar technique (IGEPI), total measurement times can be shortened to about 30 seconds, while a high spatial and temporal resolution is maintained. In this study, an IGEPI CINE-PC flow measurement pulse sequence with 16 gradient echoes was compared with a non-breathheld conventional CINE-PC technique. Flow-time curves were measured in volunteers and in patients with suspected renal artery stenosis. With IGEPI CINE-PC, mean flow velocity, vessel cross-sectional area, and mean blood flow were substantially lower by 90% to 25%. Contrast-enhanced 3D MR angiography was used to compare stenosis grading based on flow-time curve patterns with morphologic grading. With IGEPI CINE-PC, all high-grade stenoses (n = 5) were detected, whereas only 66% (n = 3) were found with conventional CINE-PC.

Adult↗
PubMedDate not supplied

Cerebral changes and cerebrospinal fluid beta-amyloid in Alzheimer's disease: a study with quantitative magnetic resonance imaging.

Pathological and biochemical studies indicate that beta-amyloid (betaA4) deposition is a hallmark in the pathogenesis of Alzheimer's disease (AD). Neuroimaging studies demonstrate that the respective cerebral changes primarily strike the temporal lobe and the amygdala-hippocampus complex and may be reliably assessed using quantitative magnetic resonance imaging (MRI). Therefore one may expect that reduced betaA4-levels are significantly correlated with measures of the temporal lobe rather than global cerebral atrophy in AD patients. To test this hypothesis in a clinical study, cerebrospinal fluid concentrations of total betaA4 and its major C-terminal variations betaA4 1-40 and betaA4 1-42 were compared with cerebral changes as assessed by quantitative magnetic resonance imaging (MRI). Significantly (P< 0.05) reduced betaA4 1-40 and betaA4 1-42 levels were found in the AD patients (17 female; six male; AD/NINCDS-ADRDA-criteria) in comparison to the patients with major depression (seven female; two male; DSM-III-R). Within the AD group, betaA4 and betaA4 1-42 levels were significantly correlated with the volume of the temporal lobes (r= 0.46 and r= 0.48, respectively) but none of the other volumetric measures. These findings indicate that changes in cerebral betaA4 levels contribute to temporal lobe atrophy in AD and support the possibility that betaA4 is central to the etiology of AD.

Aged↗
PubMedDate not supplied

Staging of invasive cervical carcinoma and of pelvic lymph nodes by high resolution MRI with a phased-array coil in comparison with pathological findings.

PURPOSE: Our goal was to stage invasive cervical carcinoma (pT1b-pT4a) and pelvic lymph nodes by high resolution MRI with a circularly polarized (cp) phased-array coil in correlation with the whole-mount specimen and the histopathological findings. METHOD: Thirty-three patients (20-68 years old; mean age 55 years) with biopsy-proven primary cancer of the cervix were prospectively examined on a 1.5 T scanner by using a cp body phased-array coil. The MR protocol consisted of high resolution T2-weighted turbo-SE (TSE) and pre- and postcontrast T1-weighted SE (SE) sequences. Slice thickness was 5-7 mm with a pixel size of 0.3-0.4 mm2. All MRI findings were matched to the whole-mount specimens and the histopathological findings. RESULTS: Pathological stages evaluated were pT1b (n = 5), pT2b (n = 16), and pT4a (n = 12). The overall accuracy rates for tumor staging were 79% for high resolution T2-weighted TSE and 76% for postcontrast T1-weighted SE images. The accuracy for high resolution T2-weighted TSE images in determining parametrial infiltration, pelvic side wall, and bladder and rectal wall infiltration was 84, 87, and 87%, respectively. In prospective analysis of the 1.0 cm criterion for diagnosis of a positive pelvic lymph node, MRI had a 72% accuracy, a 68% sensitivity, and a 78% specificity. CONCLUSION: High resolution MRI with a cp body phased-array coil provides excellent and robust high resolution images in patients with invasive cervical carcinoma. However, accuracy, specificity, and sensitivity for staging invasive cervical carcinoma and pelvic lymph nodes with correlation to whole-mount specimens and histopathological findings did not improve compared with the results in the literature using a body coil with thicker slices and a lower spatial resolution.

Adult↗
PubMedDate not supplied

In vivo quantification of brain volumes in subcortical vascular dementia and Alzheimer's disease. An MRI-based study.

Quantitative magnetic resonance imaging (MRI) was used to assess global and regional cerebral volumes in patients with a clinical diagnosis of subcortical vascular dementia (VD) and Alzheimer's disease (AD). Whole brain volume, cerebrospinal fluid volume, volumes of the temporal, frontal and parietal lobes, the cerebellum and the amygdala-hippocampus complex were determined using a personal computer-based software. Seventeen patients with VD, 22 patients with AD and 13 healthy controls were included. Analysis of covariance using age as covariate demonstrated significant mean differences between controls and dementia groups with respect to all morphological parameters. However, apart from the volume of the cerebellum no significant volumetric differences were found between VD and AD. These results indicate that MRI-based volumetry allows differentiation between AD or VD from normal controls and that measurement of cerebellar volume may be of use to separate vascular and degenerative dementia. However, since the distribution of cerebral atrophy in both dementia groups is very similar, it is suggested that the atrophic changes are not specific to the underlying cause but rather reflect the selective vulnerability of neuronal structures.

Aged↗