Biomedical subjects

K C Seelos

Publications and source records attributed to K C Seelos.

35 records · Page 2Linked to original sources

PubMed1995

High-resolution activation mapping of basal ganglia with functional magnetic resonance imaging.

We investigated the activation of the putamen and the external and internal division of the globus pallidus in 12 normal volunteers during rapid supination and pronation of their right or left hand, using functional MRI (fMRI). We observed an increase in signal intensity varying from 3.1 +/- 1.2% to 23.4 +/- 2.3% during activation. Activated areas were predominantly contralateral to the moving hand and smaller than 5 mm2. These findings indicate that fMRI allows study of the normal function of basal ganglia and may be of value in the investigation of basal ganglia disorders.

Adult↗

PubMed1995

[Possibilities of technical and methodological optimization of functional magnetic resonance tomography].

The techniques of in vivo functional magnetic resonance imaging (fMRI) have been established over the past few years. Signal changes resulting from small differences in the magnetic resonance signal caused by variations in the oxygenation state of the venous vasculature are used to map neuronal activity of the brain. While many of the advantages for using MRI for functional neuroimaging are quite obvious (high spatial and temporal resolution, direct anatomic correlation, noninvasiveness), the underlying mechanisms and problems are not fully known. This article focuses on selected topics of fMRI techniques and their problems, such as field strength B0, different types of sequences and their parameters, 2D and 3D data acquisition, different statistical methods and motion artifacts. The authors favor the use of a 1.5 T clinical scanner with EPI capabilities, 2D FLASH sequences with a TR < 60 ms, TE = 30-40 ms, alpha < 20 degrees for high resolution and sensitivity, fMRI and multislice EPI for high temporal and overview and fMRI as well as cross-correlation for post-processing.

Arousal↗

PubMed1995

[Functional magnetic resonance tomography of the basal ganglia. Use of FLASH sequences for mapping activity with BOLD contrast ane high resolution].

The activation pattern of putamen, internal and external division of globus pallidus was investigated during rapid pronation and supination of the right and left hand in 12 normal volunteers using a FLASH sequence with high resolution for functional magnetic resonance imaging (fMRI) at 1.5 T. The chosen paradigm for motor function led to a signal increase within the basal ganglia between 3 and 23%, depending on the structure and individual subject. In all cases significant activation could be found contralateral to the moving hand. In six cases activation was also found on the ipsilateral side. The activated areas within putamen, internal and external division of globus pallidus were less than 5 mm2. These first results indicate that fMRI studies of basal ganglia are feasible and might be suitable for analyzing basal ganglia disorders.

Adult↗

PubMed1995

[Use of ultra-fast computerized tomography in diagnosis of coronary heart disease].

Ultrafast or electron beam tomography (EBT) permits acquisition of images in 50-100 ms. An artifact-reduced display of heart and vessel structures as well as calcifications can be achieved. Therefore, EBT can be used for the detection and quantification of coronary artery calcification. Thirty-two patients with known coronary artery disease (CAD) were studied by EBT with and without i.v. contrast enhancement and with conventional coronary angiography. Different scoring systems were applied in order to define the basis to compare the data. The results showed a high EBT sensitivity for detection of coronary artery stenosis of up to 94% but low specificity with a maximum of 75%, depending on the scoring system applied. With EBT, differentiation between significant CAD (> 75%) and low-grade CAD (0-75%) showed significant results. The scoring system is not yet completely satisfactory, and with the integration of other screening tests and continuous development of scoring systems, the significance and reliability of this method in evaluation of CAD are expected to increase.

Aged↗

PubMed1994

[Tuberculous meningoencephalitis in post-embryo transfer status].

A 30-year old pregnant woman, who received an embryo transfer, suffered since the 12th week of pregnancy from therapy-resistant attacks of fever for several weeks. With progressive deterioration, the increasingly somnolent patient showed by now clear signs of meningism and acid-fast bacilli were found in the cerebrospinal fluid. NMR showed a finding consistent with bacterial meningoencephalitis. During therapy with INH, Rifa and EMB, the clinical course and the CSF findings showed rapid improvement. Nevertheless, spontaneous abortion occurred in the 23rd week of pregnancy. Previous history revealed, that granulomatous salpingitis had been diagnosed several years earlier as the reason for infertility.

Adult↗

PubMed1994

[MR angiography of the heart and thoracic blood vessels. Use of rapid ECG-triggered techniques with multiplanar reconstruction capability].

Segmented 2D times-of-flight (TOF) magnetic resonance angiography (MRA) with ECG gating is a suitable adjunct to conventional magnetic resonance tomography. Based on our experience with 106 patients, cardiovascular MRA primarily aids in the diagnosis of congenital heart disease, but is of minor importance for the evaluation of acquired cardiovascular disease, such as aortic aneurysms. Changes in flow dynamics as a result of spin dephasing may render partial signal loss. Due to flow turbulence and resulting signal loss distal to stenoses, difficulties may arise in correctly determining the degree of stenosis and differentiating between partial thrombosis and slowly flowing blood. The most promising approach for optimizing 2D TOF MRA is enhancement of the intravascular signal and suppression of background signal. For the equipment we use with a 0.5 Tesla scanner, the most powerful combination to enhance intravascular signal and suppress back-ground noise was applying a flip angle of 65 degrees and a short inversion prepulse. The influence of the flip angle and prepulse on the intravascular signal varies, dependent on the flow velocities and heart rates. Secondary reconstructions, such as the MIP technique, contribute to better spatial orientation by using rotating projection views. To avoid overprojection artifacts and loss of diagnostic information, 2D single slices should be the primary source of image analysis.

Aortic Diseases↗

PubMed1994

[Patient monitoring and safety aspects in magnetic resonance imaging examinations].

With the continuously growing number of MRI examinations and the enormously rapid application of new technical developments, patient monitoring and safety aspects become an increasingly important issue. The vendors of MRI systems and the legislation tend to underestimate and ignore these problems. Therefore the institutions which operate MRI units have to find solutions by their own initiative. Not only due to forensic reasons a monitoring concept should be developed with suitable equipment and careful documentation in any institution operating an MRI unit. This article discusses the planning, implementation and conduct of adequate patient monitoring during MRI examinations.

Adult↗

PubMed1993

Cardiac abnormalities: assessment with T2-weighted turbo spin-echo MR imaging with electrocardiogram gating at 0.5 T.

PURPOSE: To evaluate the cardiovascular system with magnetic resonance (MR) imaging performed with the turbo spin-echo (TSE) method and electrocardiogram (ECG) gating. MATERIALS AND METHODS: ECG-gated T2-weighted TSE images were obtained in 52 patients with 68 pathologic conditions (intracardiac [n = 18], myocardial [n = 23], pericardial [n = 6], paracardial [n = 10], or aortic [n = 11] disease) and 10 healthy subjects. In healthy subjects, TSE parameters were tested and optimized, and signal-to-noise ratios (S/Ns) and contrast-to-noise ratios (C/Ns) were determined. Delineation of the endo-, epi-, and pericardial borders and signal intensity characteristics of myocardium, fat, pericardium, blood flow, tumors, and clots were assessed. RESULTS: The TSE method provided good-quality T2-weighted images with sharp edge definition in a short imaging time. Increasing the turbo factor reduced motion artifacts and preserved the S/N and C/N. TSE images also helped in diagnosis of tumors, pleural effusions, inflammatory changes, and intravascular clots. CONCLUSION: TSE MR imaging is a feasible alternative to time-consuming conventional SE MR imaging, reduces motion artifact, and may help in evaluation of the cardiovascular system.

Adipose Tissue↗

PubMed1992

Magnetic resonance imaging in acute and subacute mediastinal bleeding.

The appearance of intracranial hematoma on magnetic resonance (MR) images has been described. However, the appearance of hematoma on ECG-gated spin-echo images, which are used for cardiac imaging, has not been described previously. Accordingly a retrospective analysis of nine consecutive patients with acute and subacute mediastinal bleeding imaged with ECG-gated spin-echo MR images was done. The time interval between the incipient event and the date of the MR study was determined, and the signal appearance of the hemorrhage was evaluated relative to striated muscle and fat. MR findings were corroborated by other imaging modalities and surgical findings. Acute hematomas showed medium to high signal intensity, whereas subacute hematomas had areas of high signal intensity on images acquired with ECG gating to every heart beat (repetition time = R-R interval) and a short echo time (30 msec). The characteristic signal intensities of blood on ECG-gated MR images are usually distinct in comparison to other pericardial and mediastinal fluid collections. The ability of MR to specifically identify blood within the first few hours after hemorrhage was not tested in this study.

Acute Disease↗

PubMed1992

Application of cine nuclear magnetic resonance imaging for sequential evaluation of response to angiotensin-converting enzyme inhibitor therapy in dilated cardiomyopathy.

Cine nuclear magnetic resonance (NMR) imaging was used to serially measure cardiovascular function in 17 patients with New York Heart Association class II or III heart failure and left ventricular ejection fraction less than or equal to 45% who were treated for 3 months with benazepril hydrochloride, a new angiotensin-converting enzyme inhibitor, while continuing treatment with diuretic agents and digoxin. Interobserver reproducibilities for ejection fraction (r = 0.94, SEE 3.3%), end-systolic volume (r = 0.98, SEE 10.6 ml), end-diastolic volume (r = 0.99, SEE 8.29 ml), end-systolic mass (r = 0.96, SEE 15.4 g), end-systolic wall stress (r = 0.91, SEE 10 dynes.s.cm-5) and end-systolic stress/volume ratio (r = 0.85, SEE 0.13) demonstrated applicability of cine NMR imaging for the serial assessment of cardiovascular function in response to pharmacologic interventions in patients with heart failure. During 12 weeks of treatment with benazepril, ejection fraction increased progressively from 29.7 +/- 2.2% (mean +/- SEM) to 36 +/- 2.2% (p less than 0.05), end-diastolic volume decreased from 166 +/- 14 to 158 +/- 12 ml (p = NS), end-systolic volume decreased from 118 +/- 12 to 106 +/- 11 ml (p less than 0.05), left ventricular mass decreased from 235 +/- 13 to 220 +/- 12 g (p less than 0.05), end-systolic wall stress decreased 29% from 90 +/- 5 to 64 +/- 5 dynes.s.cm-5 (p less than 0.05), end-systolic pressure decreased from 92.6 +/- 3.7 to 78.8 +/- 5.3 (p less than 0.05) and end-systolic stress/volume ratio, a load-independent index of contractility, decreased from 0.83 +/- 0.05 to 0.67 +/- 0.06 (p less than 0.05), demonstrating that improved ejection fraction is due to afterload reduction.

Analysis of Variance↗

PubMed1991

Abnormalities of the pulmonary veins: evaluation with MR imaging and comparison with cardiac angiography and echocardiography.

Seventy-seven patients underwent T1-weighted spin-echo magnetic resonance (MR) imaging. Group 1 (n = 56) consisted of patients with various types of congenital heart disease but normal pulmonary veins. Group 2 (n = 22) consisted of patients with the following conditions: partial anomalous pulmonary venous connection (n = 11), total anomalous pulmonary venous connection (n = 5), cor triatriatum (n = 4), or pulmonary vein stenosis (n = 2). In group 1, the sites of connections of all four pulmonary veins were identified with MR imaging in 88% of cases; the connections of at least three pulmonary veins were seen in all patients. In group 2, the prospective detection rate of pulmonary venous abnormalities with MR imaging was 95%. The prospective detection rates of pulmonary venous abnormalities with cardiac angiography (n = 13) and echo-cardiography (n = 13) were 69% and 38%, respectively. This study indicates that MR imaging can accurately demonstrate the normal pulmonary veins and abnormalities of the pulmonary veins.

Adolescent↗

PubMed1990

Persistent and recurrent hyperparathyroidism: assessment with gadopentetate dimeglumine-enhanced MR imaging.

The effect of gadopentetate dimeglumine on signal intensity of abnormal parathyroid glands was assessed in 14 patients with persistent and recurrent hyperparathyroidism. Non-contrast material-enhanced T1- and T2-weighted spin-echo images were compared with T1-weighted images obtained 1 minute and 10 minutes after administration of gadopentetate dimeglumine. Percentage of contrast between the abnormal gland and surrounding tissue was determined with the use of skeletal muscle, subcutaneous fat, and thyroid gland as reference tissues. All 11 abnormal parathyroid glands showed low to intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Gadopentetate dimeglumine significantly increased the signal intensity enhancement ratio of all abnormal parathyroid glands, causing increased percentage of contrast relative to the thyroid gland and skeletal muscle on T1-weighted images. However, the percentage of contrast relative to these tissues was even greater on nonenhanced T2-weighted images. Thus, gadopentetate dimeglumine can substantially enhance the signal intensity of abnormal parathyroid glands and improve differential contrast with some neighboring tissues on T1-weighted images, but it does not improve contrast with surrounding tissue beyond that achieved on T2-weighted images.

Adipose Tissue↗

PubMed1990

Evaluation of surgical procedures for cyanotic congenital heart disease by using MR imaging.

ECG-gated MR imaging has been shown to be effective for the diagnosis of congenital heart disease. In this study, we assessed its role in the postoperative evaluation of surgical procedures in patients with complex congenital heart disease. MR images of 26 patients with Rastelli (five), Fontan (three), Senning (three), Damus (one), Jatene (eight), Waterston (four), and Potts (two) procedures were evaluated retrospectively. The accuracy of MR imaging was compared with that of angiography in 20 patients. The surgical anastomoses were identified in all patients. Patency, atresia, or hypoplasia of central pulmonary arteries and postoperative complications (focal stenoses of pulmonary arteries, thrombosed conduit, peri-conduit abscess) were shown. Narrowing of the right ventricular outflow tract and focal compression of the proximal pulmonary arteries were recognized as specific complications of the Jatene procedure. MR imaging appears to be effective in the postoperative evaluation of surgical procedures used for congenital heart disease. It should be considered as an alternative to repeated catheterization and angiography for the postoperative examination of children with complex congenital heart disease.

Adolescent↗

PubMedDate not supplied

MR angiography of congenital heart disease: value of segmented two-dimensional inflow technique and maximum-intensity-projection display.

Magnetic resonance (MR) angiography of the cardiovascular system was evaluated in 41 patients with congenital heart disease by using a two-dimensional (2D) inflow technique based on a magnetization-prepared gradient-echo pulse sequence with segmented k-space data acquisition and electrocardiographic gating at 0.5 T. Inversion and saturation prepulses were used to suppress stationary tissue and enhance intravascular signal. Presaturation slabs were applied where certain vascular structures had to be suppressed. Sequence parameters were optimized by evaluating signal intensity and contrast characteristics for various flip angles and inversion and saturation delay times. The heart and intrathoracic vasculature were encompassed with 40-50 overlapping sections. Both 2D angiograms and maximum-intensity-projection images were evaluated. Combining data sets acquired in the sagittal and transverse orientations provided the most satisfactory information about the pulmonary arteries. The highest signal-to-noise ratios were obtained with a flip angle of 65 degrees and short prepulse delay times. Two-dimensional MR angiography can provide useful diagnostic information but requires a thorough understanding of in-plane and hemodynamically induced signal intensity changes.

Aorta↗

PubMedDate not supplied

Detection of aortic arch thrombus using MR imaging.

Three patients with peripheral embolization and negative echocardiographic examinations were studied with MR imaging. Magnetic resonance imaging detected aortic arch thrombi in the absence of aortic aneurysm, dissection, or ulcerated plaques. By combining spin echo and cine MR sequences, MR enabled us to characterize and contrast intravascular mural thrombi reliably without application of contrast media. Thus we are assisted in the identification of patients at risk for embolization from an often overlooked source: the thoracic aorta.

Aged↗

PubMedDate not supplied

Cine gradient refocused echo (GRE) imaging of intravascular masses: differentiation between tumor and nontumor thrombus.

Spin echo MR imaging has not permitted reliable differentiation between intraluminal blood clot and tumor thrombus. This study assessed the role of ECG referenced repetitive gradient refocused echo (cine GRE) imaging for the differentiation of intravascular tumor from blood clot. Cine GRE images were reviewed in 23 patients, 11 of whom had intravascular tumor and 12 of whom had intravascular blood clots. Percentage contrast between the lesion and skeletal muscle as the reference tissue was determined from a subjective review of the images and objective signal intensity measurements. Intravascular clots were found to be lower in signal intensity than muscle (mean -55 +/- 29%). Intravascular tumors showed higher signal intensity relative to muscle (mean +17 +/- 9%) with the exception of myxomas (n = 2), which had signal intensity values relative to muscle as low as clots (mean -41 +/- 17%). Three masses in the inferior vena cava were composed of central tumor and peripheral clot; the two components could be differentiated with cine GRE imaging. Cine GRE imaging provides adequate signal intensity differences to visualize intravascular masses and helps to differentiate intravascular clot from tumor thrombus. However, if the tumor contains substantial amounts of iron, then the signal is also low and consequently clot and thrombus may not be distinguishable. This can occur in some atrial myxomas.

Diagnosis, Differential↗

PubMedDate not supplied

Intraprocedural thrombus formation during coil placement in ruptured intracranial aneurysms: treatment with systemic application of the glycoprotein IIb/IIIa antagonist tirofiban.

BACKGROUND AND PURPOSE: When using detachable coils to treat intracranial aneurysms, thromboembolism is the most feared and frequently reported complication during or after endovascular therapy. The purpose of this study was to document the therapeutic effect of tirofiban on patency of the parent vessel, rate of rebleedings, and outcome of the patients in the setting of acute subarachnoidal hemorrhage. METHODS: A patient data base was retrospectively reviewed to identify patients in whom thrombus occurred during endovascular treatment of ruptured cerebral aneurysms within a 34-month period and who were treated with tirofiban. All patients underwent anticoagulation with heparin during endovascular treatment procedures. Sixteen patients (age range, 52.9 +/- 10.7 years; 10 women, 6 men) were identified with intraprocedural thrombus formation. The patency of the parent vessel was assessed in a retrospective analysis blinded to outcome. Eight patients received ventriculostomy and had a follow-up CT. RESULTS: Local nonocclusive thrombus at the coil surface was detected in 5 patients, in all of whom the thrombus was dissolved. In 10 patients, partial or total occlusion of the parent vessel occurred during the intervention; in 8 of these, the vessel was recanalized completely and in 2 drug administration was assisted by mechanical means. In 1 patient, however, the occlusion persisted. No periprocedural rebleedings of the ruptured aneurysm occurred; 3 of 8 ventriculostomies had clinically silent small local bleedings. CONCLUSION: The use of tirofiban in the setting of endovascular treatment of ruptured intracranial aneurysms to dissolve platelet aggregation seems relatively safe and effective.

Adult↗