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M V Knopp

Publications and source records attributed to M V Knopp.

158 records · Page 9Linked to original sources
PubMed1992

[Positron emission tomography of the thorax. The current clinical status].

The non-invasive diagnostic assessment of thoracic lesions has been greatly enhanced by the use of positron emission tomography with metabolic active radio-compounds such as fluor-18 labeled deoxyglucose. Four clinical fields of use were established: differential diagnostic evaluation of lesions (T-staging); classification of adenopathy (N-staging); therapy response monitoring; diagnostic evaluation of recurrence. The upcoming challenges for clinical use are limited availability and necessary technical and qualitative standardizations.

Carcinoma, Bronchogenic↗
PubMed1991

[Computed tomography of the upper mediastinum. Optimized contrast media application by the use of an infusion pump].

The aim of this study is to show the advantages of a power injector for contrast media application in comparison to manual bolus injection. The evaluation of 144 studies showed significant improvements for the examinations using the power injector based on densitometry in selected vessels (average enhancement 348 vs 280%) as well as subjective evaluation of contrast quality (3.4 pts vs 2.3 pts on a subjective scale) and contrast-induced artifacts (1.8 vs 2.3 on a subjective intensity scale). All parameters show that an increased, more reliable, and homogeneous enhancement can be obtained by application of the power injector compared to manual bolus injection technique using the same amount of contrast media (100 cc). Due to the possible standardisation of this technique, the results are reproducible. Increased reliability in expected diagnostic gain can be obtained using our technique for intravenous contrast application. This introduced technique requires no additional monetary or time expense and is therefore applicable for clinical routine work.

Contrast Media↗
PubMedDate not supplied

Fatty replacement of bone marrow after radiation therapy for Hodgkin disease: quantification with chemical shift imaging.

The authors studied the long-term fatty replacement of bone marrow in 23 patients who had received radiation therapy for Hodgkin disease, with T1-weighted magnetic resonance imaging and quantitative chemical shift imaging. T1-weighted images revealed a mostly homogeneous high-signal-intensity pattern, in contrast to the hypointense pattern of nonirradiated marrow. The degree of fatty replacement was objectively assessed with chemical shift imaging, comparing patients to age-matched healthy volunteers. The authors found an increase in relative fat signal of 37% in the thoracic spine and 34% in the lumbar spine. The relative fat signal of nonirradiated pelvic and femoral marrow was decreased by 8%, indicating marrow reconversion. No radiation dose dependence was found in the range from 25 to 50 Gy. No signs of marrow regeneration were observed 15-126 months after radiation therapy. With chemical shift imaging, the degree of long-term radiogenic fatty replacement of the bone marrow can be quantified, confirming the lack of regeneration after radiation therapy for Hodgkin disease.

Adult↗
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

An optimized examination protocol for contrast-enhanced cervical and mediastinal CT.

We compared an optimized contrast-enhanced CT technique for the neck and upper mediastinum with a conventional technique and with nonenhanced images, using densitometric measurements. The optimized protocol included slice thickness, infusion rate, postural maneuvers, and manipulation of the gantry tilt. Densitometric evaluation showed significantly higher enhancement values in vessels and metastases with the optimized protocol than with conventional technique, without significant enhancement in muscle. Semiquantitative assessment demonstrated significantly better image quality with the optimized protocol. The optimized technique has been implemented into routine use.

Absorptiometry, Photon↗
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↗