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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

Unusual burns of the lower extremities caused by a closed conducting loop in a patient at MR imaging.

An extremely rare occurrence of third-degree burns was induced in the medial calves of a male patient with unusual anatomy (after resection and radiation therapy of a liposarcoma) during conventional magnetic resonance (MR) imaging on a clinical 1.5-T MR system that operated without any external conductor present and within safe limits. A closed conducting loop was inadvertently created, which caused focal increased temperature at the junction of his calves.

Adult↗
PubMed1996

Cervical carcinoma: comparison of standard and pharmacokinetic MR imaging.

PURPOSE: To stage advanced cervical carcinoma with conventional or pharmacokinetic magnetic resonance (MR) imaging by correlating imaging findings with whole-mount specimens and histopathologic findings. MATERIALS AND METHODS: Twenty-six adult patients with primary cervical cancer (stages IIB-IVA) underwent T2-weighted turbo spin-echo (SE) MR imaging; gadolinium-enhanced, T1-weighted SE MR imaging; and gadolinium-enhanced, saturation-recovery, turbo fast low-angle shot MR imaging. All imaging findings were correlated with the whole-mount specimens and histopathologic findings. Signal intensity changes versus time were analyzed by using a pharmacokinetic model and parameter values displayed as a color-coded overlay. RESULTS: Histopathologic stages were IIB (n = 9), IIIB (n = 1), and IVA (n = 16). The overall accuracy for tumor staging was 73% for T2-weighted, 81% for T1-weighted, and 92% for pharmacokinetic MR imaging. Pharmacokinetic MR imaging was accurate (90%) in the diagnosis of tumor extension into the bladder and/or rectal wall but inaccurate (69%) in that of parametrial invasion. T2-weighted images were most accurate (86%) in the assessment of parametrial tumor extension but less accurate (69%) in that of bladder or rectal invasion. CONCLUSION: T2-weighted turbo SE images are still superior to contract medium-enhanced T1-weighted SE or pharmacokinetic MR images in the diagnosis of parametrial infiltration by uterine cervical carcinoma. However, pharmacokinetic MR imaging is a promising method for demonstrating and staging IVA disease.

Adenocarcinoma↗
PubMed1996

Pelvic lesions in patients with treated cervical carcinoma: efficacy of pharmacokinetic analysis of dynamic MR images in distinguishing recurrent tumors from benign conditions.

OBJECTIVES: Dynamic MR image series were analyzed with a pharmacokinetic two-compartment model. To preserve the spatial resolution of the dynamic MR images, the pharmacokinetic parameters were computed pixel by pixel, color coded, and superimposed on conventional MR images (pharmacokinetic mapping). The efficacies of pharmacokinetic mapping and conventional MR imaging in distinguishing between recurrent tumors and benign conditions in patients who have pelvic lesions after treatment of cervical carcinoma were compared. MATERIALS AND METHODS: Twenty-one women with 24 suspected pelvic lesions and a history of treated cervical carcinoma (stages IB-IIIA) were included in this study. Patients had been treated before MR imaging with surgery or irradiation alone (eight patients) or a combination of the two (13 patients). Patients were referred because of our findings from CT examinations and/or clinical examinations. Of 24 suspected lesions, 17 were histologically verified as tumor recurrences and seven were classified as benign masses (histologically diagnosed as fibrosis and granulation tissue). T1- and T2-weighted spin-echo images were interpreted by three observers. During and after constant-rate infusion of gadopentetate dimeglumine, the kinetics of lesion response were determined with a strongly T1-weighted saturation recovery turbo-fast low-angle shot sequence. The signal-time curves for the suspected lesions were analyzed within the framework of a pharmacokinetic two-compartment model and displayed as color-coded images. The calculated pharmacokinetic parameters (amplitude [A] and tissue distribution time [t21]) were evaluated retrospectively to obtain optimal threshold values for differentiating malignant lesions from benign lesions. RESULTS: Analysis of the pharmacokinetic mapping data showed significantly shorter (p < .005) and stronger (p < .001) contrast medium enhancement of malignant lesions (t21, 24 sec; A, 1.5 arbitrary units) than of benign lesions (t21, 65 sec; A, 0.7), resulting in a sensitivity of 100%, a specificity of 88%, and an accuracy of 96%. Interpretation of the lesions on conventional T2-weighted MR images resulted in a sensitivity of 90%, a specificity of 38%, and an accuracy of 74%. CONCLUSION: Analysis of color-coded pharmacokinetic maps is more effective than conventional MR imaging in distinguishing between malignant and benign conditions in patients who have pelvic lesions after treatment of cervical carcinoma.

Carcinoma, Squamous Cell↗
PubMed1996

[Quantitative magnetic resonance tomography and the severity of deficits in dementia of the Alzheimer type].

The aim of the present study was to investigate the severity of dementia of the Alzheimer type (DAT) with respect to morphological changes revealed by quantitative magnetic resonance imaging (MRI). Seventeen patients with DAT (NINCDS-ADRDA guidelines) and 10 healthy elderly controls were included. The severity of dementia was evaluated on the Mini Mental State Examination (MMSE), the Global Deterioration Scale (GDS) and the Brief Cognitive Rating Scale (BCRS). Three-dimensional MRI sequences were acquired using a 1.5-T Siemens Magnetom. Whole-brain volume and the volume of the amygdala-hippocampus complex (AHC) were assessed using the newly developed software NMRWin. This software provides a semi-automated measure of the whole brain volume, while measurement of substructures requires manual guidance. In addition, the ventricle-brain ratio (VBR) was assessed. All morphometric parameters differed significantly between the two groups. AHC volumes discriminated best between them with only a small overlap. These findings were confirmed when only the data of the mildly demented patients were included in the analysis. The degree of AHC atrophy exceeded that of generalized cerebral atrophy. The severity of dementia as indicated by the MMSE, GDS and BCRS scores was correlated significantly with the volumes of the AHC bilaterally, but not with whole-brain volume or with VBR. These results underline the importance of the mesial temporal substructures in the etiology and progression of DAT and indicate that the volume of the AHC can be monitored by MRI and may be used to follow up the disease process.

Aged↗
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↗