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Biomedical subjects

M V Knopp

Publications and source records attributed to M V Knopp.

At least 145 records · Page 8Linked to original sources
PubMed1994

[A pharmacokinetic analysis of Gd-DTPA enhancement in MRT in breast carcinoma].

Dynamic Gd-DTPA enhanced MR of the breast was performed in one single slice in 27 patients with suspicious nodular lesions. The results could be histologically verified in all cases. A rapid spin-echo sequence with a time resolution of 8.75 s was used for the dynamic examination. The signal changes were analysed using a pharmacokinetic model which allowed parametrization of the contrast enhancement and transformation of the data into colour coded parameter images. The parameters allowed reliable distinction of 9 benign from 18 malignant lesions (p < 0.05 for "amplitude", p < 0.001 for "k21"). One fibroadenoma could not be distinguished from the carcinomas. Lymph node metastases and the pharmacokinetic parameter amplitude correlated significantly (p < 0.05).

Adult↗
PubMed1994

Breast tumors: computer-assisted quantitative assessment with color Doppler US.

PURPOSE: To compare quantified measurements with color Doppler ultrasonography (US) with those obtained with conventional duplex US in the differential diagnosis of suspect lesions in the breast. MATERIALS AND METHODS: A computer-assisted protocol was used to calculate the color pixel density (CPD) and the mean color value (MCV) in US images of breast lesions. These results were compared with conventional results in the examination of 25 patients (aged 29-78 years) with carcinomas and 32 patients (aged 23-73 years) with benign lesions of the breast. RESULTS: The sensitivity of maximum flow velocity in helping identify carcinomas was 60% and the specificity was 70%. In color Doppler US, the sensitivity for MCV in helping identify carcinomas was 92% and the specificity was 78%; for CPD the sensitivity was 64% and the specificity was 91%. Combining MCV and CPD did not improve differentiation. CONCLUSION: Computer-assisted image analysis may be superior to conventional duplex US in helping differentiate between carcinomas and benign lesions.

Adult↗
PubMed1994

MR mammography with pharmacokinetic mapping for monitoring of breast cancer treatment during neoadjuvant therapy.

The increased clinical understanding of neovascularization and its changes during therapy are the basis for therapy-response monitoring with MR mammography of breast cancer treatment. With dynamic MR imaging, objective quantification of neovascularization can be achieved using pharmacokinetic analysis of contrast media enhancement. This technique likely will be of major clinical importance for the noninvasive evaluation of neoadjuvant therapy with a favorable cost-benefit ratio.

Adult↗
PubMed1994

[CD-ROM for radiologic literature research].

A CD-ROM containing the indexed radiological literature, including abstracts based on the MEDLINE from the last 10 years, is available with the Knowledge Finder RAD-LINE. The software can be used under DOS, Windows and Apple Macintosh. It is very user-friendly and enables efficient searches to be carried out in the literature based on free text and additional criteria such as key words, author names, time periods, journals and language. For the first time the CD permits quick, direct access to the relevant radiological literature for a greater period of time and is a very helpful tool for scientific work as well as a comfortable means of staying abreast on current topics.

CD-ROM↗
PubMed1994

[MR tomography of lung metastases with rapid gradient echo sequences. Initial results in diagnostic applications].

Rapid gradient echo sequences enable MR imaging (MRI) of pulmonary metastases with acquisition times of less than 1 s per slice. By optimization of this technique, density, T1- and T2-weighted images can be obtained (FLASH: TR 6.5 ms, TE2 = 3 ms, alpha = 10 degrees; T1w-Turbo-FLASH: TI 200 ms, TR 6.5 ms, TE2 = 3 ms, alpha = 10 degrees; T2w-Turbo-FLASH: TE1 = 50 ms, TR = 6.5 ms, TE2 = 3.5 ms; alpha = 10 degrees). In a prospective study 25 patients in whom pulmonary metastases were suspected were examined with three techniques in all three anatomical planes prior to surgery. All lung metastases revealed a high signal intensity on the FLASH as well as the T2w-Turbo-FLASH images, whereas vascular structures revealed a low signal intensity on the T2-weighted Turbo-FLASH images. Analysis regarding detection and correct number of lung metastases per patient with MRI compared with the histology revealed (n = 25): sensitivity of 82%, specificity 67%, positive predictive value of 95% and negative predictive value of 33%. While MRI does not currently have any diagnostic advantages over CT, the excellent differentiation of parenchymal lesions and vascular structures without the use of contrast medium and the variability of imaging planes are significant methodological advantages.

Adolescent↗
PubMed1994

[Evaluation of pulmonary lesions with positron emission tomography].

Positron emission tomography (PET) with fluor-18-labeled deoxyglucose (FDG) enables metabolically oriented imaging of intrapulmonary lesions. PET is currently not used for the detection of lung metastases, but for further diagnostic differentiation of nodules that have already been detected. The diagnostic accuracy of FDG-PET is currently dependent on the size of the metastatic lesions and the uptake intensity. Significantly increased FDG uptake is strongly suggestive of malignant disease whatever the size of lesion concerned. Differentiation of a solitary metastasis from a primary lung tumor is not possible. Slightly elevated FDG uptake can also be found in tuberculosis, sarcoidosis and other granulomatous or inflammatory processes. Exclusion of metastatic disease with PET is currently only reliably possible for lesions larger than 2.0 cm in diameter, owing to respiratory motion and effects of partial volume.

Blood Glucose↗
PubMed1994

[Comparison of computerized tomography and B-image ultrasound in imaging diagnosis of the mediastinum].

40 patients with suspected mediastinal tumors were independently examined with computed tomography (CT) and sonography. The findings were confirmed by bronchoscopy, mediastinoscopy or surgery. In the assessment of the upper and middle mediastinum, sonography reaches a high sensitivity. On the contrary, in the evaluation of the anterior and posterior mediastinum, sonography is clearly inferior to CT. 90% of the tumors demonstrated by CT could be assessed with sonography. The most frequent tumors can be diagnosed with ultrasound. The evaluation of tumors in the paravertebral and retrosternal space is limited. Sonography of the mediastinum is a noninvasive, well-reproducible and cost-effective imaging modality that provides important information in cases of unclear X-ray and CT findings. The preliminary results encourage to a more frequent use of mediastinal sonography.

Adult↗
PubMed1994

[TOF-MR angiography in radiotherapy treated cerebral arteriovenous malformations].

Intracerebral arteriovenous malformations represent congenital anomalies with an arteriovenous shunt (nidus). The therapeutic goal is to eliminate the risk of bleeding and to improve the clinical symptoms. The exact localization of the nidus and the identification of the feeding arteries are critical for therapy planning. Up to now conventional brain angiograms have been used for treatment planning and for the assessment of therapy response. We studied whether 3D time-of-flight (TOF) MR angiography can be used for therapy planning and monitoring. MRI and TOF-MRA studies of 28 patients undergoing radiotherapy were evaluated. They were compared to conventional angiography to assess the MRA study. A Correct identification of the arterial feeder and the nidus was possible in about 75% of the patients. In combination with the MRI study, an important 3D dataset for treatment planning could be obtained that includes therapeutically relevant information on the localization and spatial structure of the AVM as well as the adjacent brain tissue. As a noninvasive technique, close-meshed follow-up studies could be performed with MRA.

Adolescent↗
PubMed1993

Preliminary evaluation: magnetic resonance of urography using a saturation inversion projection spin-echo sequence.

A saturation inversion projection (SIP) spin-echo technique is reported which allows a reliable direct visualization of the urogenital system as well as its functional performance in magnetic resonance imaging. We used an imaging sequence with a 90 degree saturation pulse and two 180 degree inversion pulses followed by a short spin-echo (SE) pulse sequence. The three time intervals in the 90 degree-180 degree-180 degree-SE pulse train were adjusted to suppress the signals of soft tissues and fat. After intravenous injection of the contrast agent Gd-DTPA, a shortening of the kidney T1 and the T1 of the urogenital system is obtained below the T1 values of fat and soft tissues, and these remaining ultra-short T1 tissues were imaged with the SIP sequence. Using a sequential measuring technique a quantitative evaluation of the glomerular filtration rate seems to be possible with a time resolution of 18 sec per image. In addition, magnetic resonance urography using the SIP sequence provided a good visualization of the urogenital system and may show several clinical utilities in further clinical studies.

Contrast Media↗
PubMed1993

Bone marrow after autologous blood stem cell transplantation and total body irradiation: magnetic resonance and chemical shift imaging.

Magnetic resonance studies of the lumbar, pelvic, and femoral bone marrow were performed in 10 patients after autologous blood stem cell transplantation, including total body irradiation and myeloablative chemotherapy. The posttreatment interval varied between 2 and 6 yr. The appearance on T1-weighted images and the quantitative data obtained from chemical shift imaging (relative fat signal) were compared to 10 age-matched healthy volunteers. The classification of the T1-weighted images yielded no significant differences between the two groups. Chemical shift imaging by determination of the relative fat signal was able to detect a significant fatty replacement of the patients' lumbar (p < .002) and pelvic marrow (p < .01), showing the clinically inapparent decreased cellularity of the bone marrow. This difference did not change within the interval of 2-6 yr after transplantation.

Acute Disease↗
PubMed1993

Motor cortex stimulation measured by magnetic resonance imaging on a standard 1.5 T clinical scanner.

The authors report the effects of motor cortex stimulation of normal volunteers using conventional MR imaging techniques on a standard 1.5 T clinical scanner. A circular polarized head coil has been used normally for the stimulation measurements, although improvement in signal-to-noise ratio has been achieved by using a commercially available eye/ear surface coil with a loop of 8.5 cm in diameter. Magnet shimming with all first order coils was performed to the volunteer's head resulting in a magnetic field homogeneity of about 0.2 ppm. The imaging technique used was a conventional two-dimensional, first order flow rephased, gradient echo FLASH sequence with TR = 73 msec, TE = 60 msec, flip angle = 40 degrees. The stimulation experiments measured with the head coil were performed with a 64 x 128 matrix size, at a FOV = 230 mm, with NEX = 2 and 10 mm slice thickness. In case of stimulation measurements using the surface coil a 128 x 128 matrix size, a FOV = 200 mm, with NEX = 1 and a 5 mm slice thickness have been used. Total single scan time for one slice was 12 sec in both cases. The motor cortex stimulation was achieved by touching each finger to thumb in a sequential, self-paced, and repetitive manner. An increase in signal of order 4% in the motor cortex for the head coil measurements was observed, whereas of order 10% signal increase was detected for the surface coil measurements with smaller voxel size. The reported data demonstrate the technical feasibility of functional MR imaging using conventional sequences and equipment.

Feasibility Studies↗
PubMed1993

[Pulmonary sequestration: use of MR-angiography].

The confirmation of the diagnosis of intralobar pulmonary sequestration usually requires angiographic demonstration of the systemic arterial supply, and venous drainage. Magnetic resonance angiography (MR angiography) is a new, non-invasive imaging modality for examinations of the vasculature. In this report we describe its successful application in intralobar pulmonary sequestration demonstrating the feeding systemic artery, including its intrapulmonary branching, and the type of the venous return.

Adult↗
PubMed1993

[Magnetic resonance spectroscopy of breast cancer].

Conservative therapeutic concepts with initial chemotherapy for patients with breast cancer represent a challenge to non-invasive techniques for monitoring response to therapy. Experimental magnetic resonance spectroscopy studies have been able to show exemplary applications for therapy monitoring of breast cancer patients. The characteristic phosphomonoester resonances and their changes during therapy are possible clinical parameters. The additional information which can be obtained from proton and carbon spectroscopy increases the amount of detectable metabolites. On-going studies are investigating clinical applications of multinuclear spectroscopic studies in patients with breast cancer.

Breast Neoplasms↗
PubMed1992

[Recurrence paralysis: computed tomographic analysis of intrathoracic findings].

The long and singular course of the inferior (recurrent) laryngeal nerve makes it very vulnerable to infiltration by tumors of various locations. In particular, mediastinal and pulmonary lesions must be considered in the case of left vocal chord palsy. Recurrent nerve paralysis caused by a tumor indicates advanced disease. We retrospectively reviewed the computed tomography (CT) findings in 29 patients with bronchogenic carcinoma or mediastinal tumors and recurrent nerve paralysis with respect to the site, size and extent of the tumor and the lymph node status. The review revealed a marked predominance of left upper lobe tumors with extensive lymph node metastases to the anterior mediastinum and the aortopulmonary window. The extent of mediastinal involvement exceeded the average involvement in a control group of 30 randomly selected patients with bronchogenic carcinoma at the time of presentation. In all patients CT demonstrated tumor tissue which could have caused the paralysis at one or more sites along the anatomical course of the recurrent nerve. In most cases the tumor was located at the aortic arch. The left paratracheal region, right paratracheal region and right pulmonary apex were affected in one case each. We conclude that in patients with cancer, CT is a suitable method for localizing a recurrent nerve lesion.

Carcinoma, Bronchogenic↗
PubMed1992

[Measurement of the blood flow velocity in the pulmonary arteries using the magnetic resonance technique].

MR blood velocity measurements were performed by the RACE technique in a plane perpendicular to the flow of the pulmonary arteries. MR findings were correlated with those of perfusion scintigraphy, Doppler US and right heart catheter (thermodilution). The ratio of MR blood flow measurements of right and left pulmonary arteries correlated well with the results of perfusion scintigraphy (RPA to LPA) and Doppler. Poor correlation was found when comparing MR blood flow measurements with right heart catheter since absolute flow measurements can be superimposed by neighboring blood vessels in complex anatomic situations.

Adolescent↗