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Biomedical subjects

K Seelos

Publications and source records attributed to K Seelos.

16 recordsLinked to original sources
PubMed1999

Echo-planar magnetic resonance imaging (EPI) with high-resolution matrix in intra-axial brain tumors.

The aim of this study was to assess the potential of high-speed interleaved echo-planar imaging (EPI) to achieve diagnostic image quality comparable to T2-weighted imaging in patients with brain tumors. Seventeen patients with intra-axial, supratentorial tumors (10 untreated gliomas, 7 radiated gliomas) were investigated on a 1. 5-T scanner. The conventional scan (SE, TR/TE = 2200/80 ms, 18 slices) was acquired in 8 min, 4 s, and EPI (TR/TE = 3000/80 ms, 18 slices) was completed in 25 s. The films were compared in a blinded trail by three radiologists. On the general impression and anatomic display, both sequences were rated to be of similar quality. Artifacts were slightly more pronounced at the skull base and around surgical clips using EPI. Tumor delineation was nearly equivalent using EPI, compared with the T2-weighted sequence. Echo-planar imaging reached diagnostic quality in all patients. Interleaved high-resolution EPI yielded sufficient quality to depict intra-axial, supratentorial brain tumors. Since EPI can be obtained in a small fraction of the time needed for conventional spin echo, in addition to other indications it could be considered to study patients unable to cooperate.

Artifacts↗
PubMed1999

Characteristic MR lesion pattern and correlation of T1 and T2 lesion volume with neurologic and neuropsychological findings in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an arteriopathy related to a genetic defect of the notch 3 gene on chromosome 19. The purpose of this study was to evaluate lesion distribution and volume using MR imaging and to correlate the lesion volume with the neurologic and neuropsychological findings. METHODS: Twenty members of two families (14 with CADASIL as determined by linkage analysis, six healthy) were studied with MR imaging. Two observers evaluated the MR findings semiquantitatively and quantitatively. MR results were then correlated with neurologic and neuropsychological findings. RESULTS: A typical pattern of lesion distribution in patients with CADASIL was found: the frontal lobe was the site with the highest lesion load, followed by the temporal lobe and the insula. The total lesion volume on T1-weighted MR images correlated significantly with the degree of disability and the degree of impairment in neuropsychological functions (including attention, memory, and conceptual and visuospatial functions). CONCLUSION: In CADASIL patients, a common pattern of cerebral lesion distribution is found. The total T1 lesion volume is an important parameter to correlate with disability, as it may prove to be helpful in predicting the natural history of the disease.

Adult↗
PubMed1997

[Bleeding atheroma. A nuclear magnetic resonance tomography differential diagnosis of dissection of the carotid artery].

Improved methods of imaging the cerebral vascular system have increased the detection of traumatic or spontaneous dissection of the vertebral and carotid arteries. Especially MRI allows direct demonstration of intramural hematomas that are a sign of dissection of the vessel wall. We report on a patient who had an acute onset of dysarthria and monocular blurred vision, which recurred several times. Doppler ultrasound showed stenosis in both internal carotid arteries with reduced velocity of the flow; angiography confirmed the stenosis, showing a long stretch of stenosis (70%) of the right and a short stretch of stenosis (60%) of the left internal carotid arteries. MRI demonstrated a narrowing of the lumen by an intramural mass, whose signal characteristics were typical for blood. The MRI findings were thus consistent with the diagnosis of a spontaneous dissection of the carotid arteries. Since the Doppler ultrasound follow-up showed no change during the following 3 days, we interpreted the MRI findings as an indication of bleeding in an atheroma. The carotid disobliteration, performed first on the left side and later on the right side, confirmed this interpretation. Since stenosis due to a fissuring atheroma or bleeding in an atheroma requires different therapy than a dissection, it is thus important to consider the possible differential diagnosis in interpreting the MRI.

Arteriosclerosis↗
PubMed1996

BK virus encephalitis in an immunocompetent patient.

OBJECTIVES: To describe a previously healthy patient now suffering from monophasic encephalitis caused by a primary infection with BK virus and to discuss possible risk factors for developing BK virus encephalitis. DESIGN: Case report. SETTING: Referral hospital. PATIENT: The patient was examined on referral. MAIN OUTCOME MEASURES: The main diagnostic tests performed were serology, polymerase chain reaction on cerebrospinal fluid samples, and cranial magnetic resonance imaging. RESULTS: During the course of the patient's encephalitis, an IgM titer developed against polyomavirus, followed by anti-polyomavirus IgG. Wild-type BK virus was demonstrated in cerebrospinal fluid samples. Cranial magnetic resonance imaging showed diffuse reversible white matter changes most prominent on T2-weighted images. CONCLUSION: We conclude that diagnostic tests for BK, a human polyomavirus, should be included in the screening program for encephalitogenic pathogens.

Adult↗
PubMed1994

Musculoskeletal MR imaging: turbo (fast) spin-echo versus conventional spin-echo and gradient-echo imaging at 0.5 tesla.

The value of T2-weighted fast spin-echo imaging of the musculoskeletal system was assessed in 22 patients with various neoplastic, inflammatory, and traumatic disorders. Images were acquired with high echo number (i.e., echo train length) fast spin-echo (FSE; TR 2000 ms, effective TE 100 ms, echo number 13, linear k-space ordering), conventional spin-echo (SE; TR 2000 ms, TE 100 ms) and gradient-echo (GRE) sequences (TR 600 ms, TE 34 ms, flip angle 25 degrees). Signal intensities, signal-to-noise ratios, contrast, contrast-to-noise ratios, lesion conspicuousness, detail perceptibility, and sensitivity towards image artifacts were compared. The high signal intensity of fat on FSE images resulted in a slightly inferior lesion-to-fat contrast on FSE images. However, on the basis of lesion conspicuity, FSE is able to replace time-consuming conventional T2-weighted SE imaging in musculoskeletal MRI. In contrast, GRE images frequently showed superior lesion conspicuity. One minor disadvantage of FSE in our study was the frequent deterioration of image quality by blurring, black band, and rippling artifacts. Some of these artifacts, however, can be prevented using short echo trains and/or short echo spacings.

Adolescent↗
PubMed1994

[Fat-suppressing STIR sequences with and without contrast media in the MRT of ENT tumors].

Fat-suppressed STIR (short TI inversion recovery) sequences were compared to plain and contrast-enhanced T1-weighted SE sequences of head and neck tumors. 19 patients underwent MR imaging on a 0.5 Telsa system (T5-II, Philips). STIR imaging parameters: TR/TE = 1000/20 ms, inversion pulse 100 ms. All films were read by four radiologists. The image quality was graded: score from 0 to 5, by means that grade 5 = optimal quality. Sensitivity was 89% in STIR, 96% in SE sequences. Tumor delineation was graded good in the enhanced T1-weighted and enhanced fat suppression images. The unenhanced imaging was superior in STIR (STIR/T1 = 2.8/2.43). The tumor contrast was best in contrast enhanced and plain STIR sequences (STIR contrast = 3.41), and in the contrast enhanced T1-weighted SE (3.33). STIR almost equaled T1 post-contrast in respect of tumour conspicuity, but the sensitivity was lower. STIR can be a supplement to SE, but cannot substitute T1 postcontrast. The combined use is expected to have the highest assessment value.

Adipose Tissue↗
PubMed1994

[MRT of the female pelvis: turbo-spin-echo (TSE) sequences compared to conventional spin-echo sequences at 0.5 tesla].

Markedly T2-weighted MR images of the pelvis can be obtained with TSE sequences using short acquisition times. In order to determine whether TSE sequences at 0.5 Tesla produce diagnostically valuable images, 9 normals and 53 patients with suspected gynaecological tumours were examined with TSE and SE sequences. Visual comparison showed a considerable superiority of the TSE sequences in most respects. The quality of the TSE images was regarded as very good in 82% and good in 18% (SE sequences: 27% very good, 55% good, 18% moderate), delineation of anatomical structures 81% very good and 19% good (SE sequence: 31% very good, 53% good, 16% moderate). TSE sequences were also superior in the detection of pathological changes (87% very good, 13% good) compared with SE sequences (56% very good, 37% good, 7% moderate). Venous plexuses in the parametrium were better demonstrated by SE sequences. There were significantly higher signal to noise ratios (SNR) with TSE sequences for fat, bone marrow (each p < 0.001), and urine (p < 0.05). Using muscle as reference tissue, there were significantly higher signal-difference to noise ratios (SDR) for fat (p < 0.001), and bone marrow (p < 0.0001), the other pelvic organs and tumours showed no significant differences between the SNR and SDR. TSE sequences are well suited to replace SE sequences in the MR diagnosis of gynaecological tumours.

Adolescent↗
PubMed1993

[Rheumatoid arthritis of the wrist. Dynamic Gd-DTPA enhanced MRT].

21 patients with rheumatoid arthritis of the wrist diagnosed according to the criteria of the American Rheumatism Association were examined by dynamic MRT before and after the i.v. injection of Gd-DTPA (0.1 mmol/kg). The results were correlated with the clinical and radiological findings. The increased signal intensity of the pannus was 1.17 +/- 0.45%/sec and this differed significantly (p < 0.001) from bone marrow (0.16 +/- 0.11%/sec) and from muscle (0.25 +/- 0.16%/sec). Blood sedimentation rate correlated with the gradient of synovial proliferation (p < 0.05). There were no further statistically significant correlations between the clinical, radiological and MRT findings and the change in signal intensity from synovial proliferation as shown by dynamic MRT.

Adult↗
PubMed1993

[Turbo(fast) spin echo at 0.5 T: effect of echo distance and echo number on image contrast].

Signal intensities, signal-to-noise ratios (S/N), and contrast-to-noise ratios (C/N) in dependence on the echo distance and echo number of the new turbo (fast) spin-echo technique are analysed by phantom, volunteer and patient measurements. With increasing echo number (3 to 15 echoes), signal intensities increase (25 to 50%), S/N varies between different tissues, and C/N of fat to water decreases (70%). A high echo number, although it shortens the imaging time, is thus not always the best choice since the fat/water contrast is lost. However, a high fat/water contrast is advantageous for several MR applications.

Arthritis, Rheumatoid↗
PubMed1993

[Magnetic resonance tomography with fast spin-echo sequences--the results in the ENT area].

UNLABELLED: The use of T2-weighted spin-echo sequences is mandatory for identifying tumours in the ENT region and for differential diagnosis of pathological findings. A highly promising alternative to time-consuming conventional SE sequences is now available in the fast-spin-echo sequences (FSE). FSE was compared with the conventional SE (CSE) basing on 100 assessments of examinations of 20 patients. RESULTS: Conventional SE = TR/TE = 1800/90 ms with one average (NEX), FSE = TR/TE = 3200/120 ms with 4 averages (NEX). Measurement time CSE 6:59 min, FSE 3:12 min. Analysis was performed in analogy to on ROC analysis by 5 radiologists as a blind study. The anatomic differentiation and contrast performance were compared as well as the differentiation and definition of lesion and lymphatic node and a subjective overall assessment. Differentiation of pathological findings was the same with both sequences. FSE was superior to CSE in the visualisation of normal tissue, lymph nodes and also in the subjective overall assessment. The following criteria were employed in the subjective overall valuation: sum total of impressions gathered from contrast behaviour or performance, susceptibility to artifacts, and signal-to-noise ratio. Due to the definitely improved parameters of image quality and the markedly reduced scanning time--which is reduced to 50%--FSE will replace the conventional spin-echo sequence in routine diagnostics.

Artifacts↗
PubMed1993

[Magnetic resonance tomography using the fast STIR technique: optimization and a comparison with other sequences in a 0.5-Tesla system].

One disadvantage of the STIR sequence in MRI is its long acquisition time. A TR shortening for acceleration requires shortening of the inversion time depending upon the field strength. We optimized this "fast-STIR" technique at 0.5 T using calculations, phantom, volunteer, and patient measurements. This optimization procedure is transferable to other field strengths. The resulting sequence takes 4.5 minutes, fat is visualised signal-free. In the second part of our study we compared quantitatively and qualitatively the signal intensities, contrast, and sensitivity towards artifacts of this sequence with that of conventional SE and GRE sequences in 21 patients with neoplastic, inflammatory and traumatic disorders of the musculoskeletal system. The fast-STIR sequence showed similar or better lesion contrast as SE in 100% and as GRE in 88%. Decreased spatial resolution and higher sensitivity towards pulsatile artifacts of the fast-STIR sequence were only minor drawbacks.

Achilles Tendon↗
PubMed1992

Effect of cilazapril on regional left ventricular wall thickness and chamber dimension following acute myocardial infarction: in vivo assessment using MRI.

The primary goal of the current study was to assess in situ, using magnetic resonance imaging, the effect of a new angiotensin-converting enzyme inhibitor, cilazapril, in reducing left ventricular remodeling after acute myocardial infarction. Three groups of animals were investigated: (1) sham-operated rats (n = 19); (2) infarcted rats receiving no treatment (n = 23); and (3) infarcted rats receiving cilazapril (100 mg/L drinking water, n = 20). Treatment with cilazapril began on the third day postocclusion and continued for 3 to 4 months. Myocardial infarction was produced by ligation of the left coronary artery, and electrocardiographic (ECG)-gated short-axis images were acquired 3 to 4 months later. Sham-operated animals were subjected to the same procedure but the left coronary artery was not ligated. From the image acquired in the middle of the left ventricle (equatorial slice), left ventricular wall thicknesses, chamber diameters, and surface area measurements of the cavities were determined. At autopsy examination, infarct size and tissue water content were determined. The results demonstrate that magnetic resonance imaging has the potential to assess in situ the alterations of left ventricular dimensions and mass after acute myocardial infarction and can be used to document the influence of therapeutic interventions. Cilazapril provided protection against the deleterious remodeling changes such as ventricular dilation and wall thinning consequent to acute myocardial infarction.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1988

[Value of magnetic resonance tomography in the diagnosis of diseases of the thoracic aorta].

MRI with imaging in the frontal and axial planes can replace, in most cases, CT as well as angiography. By limiting oneself to these planes, the examination can be carried out on patients with acute symptoms. If the findings on MRI are indefinite due to movement or flow artifacts, angiography can be carried out immediately. This may not be possible after CT, due to limitation of contrast volumes. With the exception of patients being ventilated after multiple trauma, MRI should nowadays be the primary form of examination, particularly in high risk patients.

Aortic Dissection↗
PubMed1988

[Gd-DTPA contrast enhancement in the nuclear magnetic resonance tomographic diagnosis of thoracic space-occupying lesions].

The optimal technique for examining mediastinal masses is the use of T1 weighted spin-echo sequences (TR 500 msec/TE 17 msec) in transverse and coronal slice orientation pre and post contrast application. This setup provides an excellent morphological depiction of anatomy and pathology as well as T2 comparable information about tumor structure without the disadvantage of a reduction of the signal-to-noise ratio.

Adenocarcinoma↗