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Biomedical subjects

F Demsar

Publications and source records attributed to F Demsar.

At least 37 records · Page 2Linked to original sources

Prognostic value of contrast enhanced Gd-DTPA MRI for development of bone erosive changes in rheumatoid arthritis.

Conventional radiograms have been used to quantitate the progression of rheumatoid arthritis, mainly through the assessment of bone erosions, but this approach has many limitations. It has been suggested that an advantage of contrast-enhanced Gd-DTPA MRI over radiography may be its prognostic value due to its ability to show the natural history of active destructive to inactive fibrous pannus. The aim of this study was to evaluate the possible prognostic value of MRI for future development of bone erosive changes in small hand joints in patients with RA. The results of the study confirm that in joints in which inflammatory active pannus is shown by contrast-enhanced MRI, progression of bone-destructive changes can be expected.

Arthritis, Rheumatoid↗

Mammary carcinoma model: correlation of macromolecular contrast-enhanced MR imaging characterizations of tumor microvasculature and histologic capillary density.

PURPOSE: To determine the relationship between capillary density, a recognized surrogate of tumor angiogenesis, and magnetic resonance (MR) imaging-derived estimates of plasma volume (PV) and microvascular permeability in two mammary carcinoma models. MATERIALS AND METHODS: Dynamic spin-echo imaging was performed by using albumin-(gadolinium-diethylenetriaminepentaacetic acid)34, a prototype blood-pool contrast medium, in 14 rats with a subcutaneously implanted slow- or fast-growing subtype of R3230 mammary carcinoma. Data were fitted to an established two-compartment kinetic model to estimate PV and permeability. RESULTS: MR imaging-derived tumor PVs and permeabilities increased exponentially with increasing capillary density. MR imaging-derived microvascular characteristics correlated strongly with histologic capillary density, with an r2 of .85. CONCLUSION: Contrast medium-enhanced MR imaging may prove useful in estimating angiogenic activity in carcinomas. MR imaging may be superior to histologic assay because it is noninvasive, can be used to "sample" the entire tumor, and reflects both anatomic and physiologic characteristics.

Albumins↗

Contrast-enhanced MR imaging assessment of tumor capillary permeability: effect of irradiation on delivery of chemotherapy.

PURPOSE: To assess the effect of x rays on tumor capillary permeability with macromolecular contrast medium (MMCM)-enhanced magnetic resonance (MR) imaging. MATERIALS AND METHODS: One of paired R3230 mammary adenocarcinomas implanted in the flanks of 48 Fischer rats was treated with a single 5- or 15-Gy dose of x rays. After 1 or 3 days, MR imaging in 30 rats was performed unenhanced and enhanced with albumin-(gadolinium diethylenetriaminepentaacetic acid)30 (0.02 mmol gadolinium per kilogram body weight). Signal intensity enhancement was analyzed to estimate fractional blood volume and permeability-surface area product (PS). In 18 irradiated rats, 2.5 mg/kg cisplatin was injected intravenously, and fractional tumor platinum concentrations were measured spectrometrically. RESULTS: MR imaging showed highest capillary permeability 1 day after 15 Gy (PS 110% above control [P<.001]); PS was elevated 57% 1 day after 5 Gy and 63% 3 days after 15 Gy (P<.05). The largest mean tumor platinum fraction occurred 1 day after 15 Gy: 48% versus 20% (control)(P<.05). CONCLUSION: Transient irradiation-induced increase in tumor capillary permeability to cisplatin can be quantified with MMCM-enhanced MR imaging.

Albumins↗

Distinctive radiological features of small hand joints in rheumatoid arthritis and seronegative spondyloarthritis demonstrated by contrast-enhanced (Gd-DTPA) magnetic resonance imaging.

A series of patients with clinically early inflammatory joint disease due to rheumatoid arthritis, psoriatic arthritis and Reiter's syndrome were examined by plain film radiography and magnetic resonance imaging (MRI). The spin echo T1-weighted precontrast, T2-weighted, and, especially, T1-weighted postcontrast images demonstrated distinct differences in the distribution of inflammatory changes, both within and adjacent to involved small hand joints. Two major subtypes of inflammatory arthritis were shown, thus providing a specific differential diagnosis between rheumatoid arthritis and some patients with seronegative spondyloarthritis. In particular, all the patients with Reiter's syndrome who were studied, and half of those with psoriatic arthritis, had a distinctive pattern of extra-articular disease involvement. The need for a new classification of clinical subsets in psoriatic arthritis has been recently suggested. The present findings suggest that magnetic resonance imaging could be useful in such a reclassification of seronegative spondyloarthritis, as well as offering considerable potential for a reappraisal of pathogenesis and therapy. In this series, it was also noted that juxta-articular osteoporosis on plain film did not correlate with bone marrow oedema on MRI. Hence the aetiology of this common radiographic finding also merits further consideration.

Adult↗

Angiographic properties of Gd-DTPA-24-cascade-polymer--a new macromolecular MR contrast agent.

PURPOSE: A new macromolecular MR contrast agent, Gd-DTPA-24-cascade-polymer, was assessed for MR angiography of peritumoral vessels in rats. MATERIAL AND METHODS: High resolution 3D-SPGR (TR/TE 100/5ms, alpha = 90 degrees) angiograms were acquired in 10 Fischer rats bearing subcutaneous R3230 mammary adenocarcinomas. MRI was performed before, immediately and 40 min after administration of Gd-DTPA (0.1 mmol Gd/kg), and after either Gd-DTPA-cascade-polymer or albumin-(Gd-DTPA)30 (each 0.05 mmol Gd/kg). A semi-quantitative analysis of small peritumoral vessels and tumor rim enhancement was performed on maximum intensity projection (MIP) angiograms using a 4-point scoring system. A quantitative analysis compared vascular signal-to-background-(S/B), signal-to-noise-, and contrast-to-noise-ratio. RESULTS: Gd-DTPA produced a transient and low-scoring vessel definition (0.2 +/- 0.1), but strong rim enhancement (score 1.7 +/- 0.1). The cascade polymer resulted in better but submaximal vessel delineation (score 1.6 +/- 0.3, S/B 5.0 +/- 0.2) and strong rim enhancement (score 1.8 +/- 0.1). Albumin-(Gd-DTPA)30 produced the best and most time-persistent angiograms (score 2.6 +/- 0.2, S/B 7.4 +/- 0.2), but minimal rim enhancement (score 0.3 +/- 0.2). CONCLUSIONS: The Gd-DTPA-24-cascade-polymer demonstrated the useful combination of strong tumor rim enhancement and detailed angiographic definition of peritumoral vessels. These are advantages associated with extracellular and blood pool contrast media, respectively.

Adenocarcinoma↗

Tumor angiography using high-resolution, three-dimensional magnetic resonance imaging: comparison of gadopentetate dimeglumine and a macromolecular blood-pool contrast agent.

RATIONALE AND OBJECTIVES: We compared the peritumoral vascular definition in rats using either a paramagnetic extracellular or a macromolecular contrast medium in combination with high-resolution magnetic resonance (MR) imaging. METHODS: High-resolution, three-dimensional spoiled gradient-refocused acquisition in a steady state (SPGR) images were acquired from tumor-bearing Fischer-344 rats before, immediately after, and again 40 min after administration of gadopentetate dimeglumine (0.1 mmol Gd/kg; n = 10) and albumin-(Gd-DTPA)30 (0.05 mmol Gd/kg; n = 5). Small peritumoral vessels were analyzed semiquantitatively on maximum intensity projection angiograms using a 4-point scoring system; quantitative analyses included signal-to-background ratios (SBRs) and signal-to-noise ratios. RESULTS: Gadopentetate dimeglumine caused a transient and low-scoring (0.2 +/- 0.1, SBR = 1.9 +/- 0.2) vessel definition but strong rim enhancement (score = 1.4 +/- 0.2). Albumin-(Gd-DTPA)30 produced persistent, high-quality angiograms (score = 2.6 +/- 0.2, SBR = 7.4 +/- 0.2) but minimal rim enhancement (score = 0.3 +/- 0.2). CONCLUSION: Albumin-(Gd-DTPA)30 combined with high-resolution MR imaging produces time-persistent, detailed angiographic definition of peritumoral vessels. Vascular maps obtained with gadopentetate dimeglumine enhancement are not time persistent or of equal quality.

Adenocarcinoma↗

Cross-section areas of calf muscles in athletes of different sports.

Differences in cross-section areas of calf structures were studied in different sportsmen groups and controls: sprinters, long-distance runners, free-climbers, and sport non active persons. The cross-section areas of calf tissues were established by magnetic resonance imaging. There were no statistically significant differences between the groups in single muscle areas. The only statistically significant difference was found in subcutaneous fat between sportsmen and non active persons. Results show a general adaptive tendency of the muscle to greater activity, without exhibiting sport-group specificity differences.

Adaptation, Physiological↗

Precontrast and postcontrast (Gd-DTPA) magnetic resonance imaging of hand joints in patients with rheumatoid arthritis.

In an attempt to demonstrate whether clinically selected joints of the hand in active rheumatoid disease had consistent MRI findings, 45 patients were examined, in whom one joint in each was selected by both the referring clinician and patient as being active and symptomatic. Such joints, in order to be included in the study, were required to conform to ARA criteria of activity and usually mild to moderate X-ray changes. The joints were imaged using spin-echo sequences with T1W and T2W precontrast images, followed by T1W images after intravenous administration of Gd-DTPA. Different patterns of joint abnormalities were found. In 27 joints MRI findings suggested highly active synovitis and/or destructive pannus. In four, crescentic enhancement was thought to be compatible with simple synovitis, but in 23 rounded masses of synovial proliferation were characterized by marked, diffuse contrast enhancement on T1W postcontrast images, which corresponded well with high signal intensity on T2W images. Synovial proliferation in a further 12 joints was shown by only moderate stippled contrast enhancement and nonhomogeneous intermediate to high signal intensity on T2W images. These findings were thought to represent less active synovitis and pannus. MRI did not demonstrate inflammatory activity in six joints. In two of these pannus was of low signal intensity on T2W images, without contrast enhancement after Gd-DTPA infection presumed fibrotic and inert, and four were normal on all pulse sequences. These results suggest that clinical features of synovitis, even in carefully selected joints clinically, do not produce a homogeneous group when examined by MRI imaging. Indeed, a spectrum exists from presumed marked, active synovitis to total normality. If MRI is to be used as a clinical and research tool in the assessment of rheumatoid disease, and its therapeutic manipulation, these results are of some importance, since the variable findings indicate an appreciable heterogeneity of appearances in joints thought clinically to be of relatively uniform severity.

Adult↗

Discrimination between neuropathy and myopathy by use of magnetic resonance imaging.

Since discrimination between myopathy and neuropathy may be difficult it seemed reasonable to investigate the possibility of assessment of these disorders by means of magnetic resonance imaging. Children with Duchenne muscular dystrophy and children with the juvenile type of spinal muscular atrophy were selected for the study and compared to healthy volunteers. Measurements were performed on a small Bruker imaging system operating at 2.35 T, and T1 weighed images on the lower extremities were recorded. Images obtained on the diseased extremities could be clearly distinguished from the images from healthy children. Furthermore, preferential involvement of fast muscles in patients with muscular dystrophy, and differences in distribution of fatty degeneration of muscles enable reliable discrimination between muscular dystrophy and spinal muscular atrophy.

Adolescent↗

Lysing patterns of retracted blood clots with diffusion or bulk flow transport of plasma with urokinase into clots--a magnetic resonance imaging study in vitro.

Fresh retracted clots are known to be poorly lysable by fibrinolytic agents. We have studied whether lysis of retracted clots could be enhanced by bulk transport in comparison to pure diffusion of plasma containing urokinase (400 IU/ml) into the clots. Cylindrical retracted blood clots were occlusively glued by a polyester into plastic tubes and put in contact with plasma through the clot bases. One group of clots (perfused clots, n = 10) was placed under a pressure difference of 6 kPa (60 cm H2O) which resulted in an average plasma flow of 0.97 +/- 0.34 microliters/min through the clot during the first hour. Another group of clots (non-perfused clots, n = 10) was incubated in the lytic plasma without a pressure difference. Clot sizes were measured during lysis by magnetic resonance imaging (MRI). Channels representing lysed areas penetrated into perfused clots with a velocity of 5.4 +/- 1.6 mm/h (n = 10), whereas the boundaries of non-perfused clots subsided with a velocity of less than 0.1 mm/h. Eight of the 10 perfused clots were recanalized after 8 h and the sizes of the perfused group were reduced to 64.0 +/- 10.7% of the initial values. The relative sizes of non-perfused clots after 8 h remained significantly higher: 95.0 +/- 1.3%, p < 0.005. In a separate experiment good agreement was obtained between the measured clot sizes by MRI and the residual radioactivity of 125I-fibrin in the clot.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport↗

Magnetic resonance imaging of retracted and nonretracted blood clots during fibrinolysis in vitro.

Magnetic resonance imaging (MRI) of retracted blood clots embedded in nonretracted clots was used to follow their lysis with urokinase in a plasma milieu in vitro. The two types of clots that were imaged in the same plane differed in signal intensity on T2-weighted spin echo MR images throughout the 20-hour observation period. It was thus possible to delineate the contours of both clot types and measure their relative sizes by digital image processing. Lysis of retracted clots proceeded significantly slower than lysis of nonretracted clots. Our in vitro results suggest that MRI might prove useful in detecting thrombus retraction in vivo and in predicting the outcome of thrombolytic therapy.

Carboxyhemoglobin↗

Force, fatigue, and the cross-sectional area of wrist extensor muscles after radial nerve grafting.

The force and fatigue of the wrist extensor muscles during maximal voluntary and tetanic contractions were measured and compared in the injured and noninjured extremities of 11 patients with radial nerve gap injury and in 9 normal volunteers. The cross-sectional area (CSA) of the wrist extensor muscles was determined by magnetic resonance imaging and was correlated with force. In the patient group, an average of three (range, 2-4) sural nerve cable grafts, measuring 11.5 +/- 5 cm (range, 5-20 cm) in length, were sutured to the nerve stumps at least 9 years before this study. Differences in the CSA values of the injured and noninjured arms were compared, and a ratio was established (CSAR). The mean CSAR was 82.9% +/- 14.3. These differences were not statistically significant (P > 0.10, paired t-test). Despite very well-recovered muscular mass, the maximal voluntary contraction force was found to be incompletely recovered by up to 62.7% +/- 23, when compared with the noninjured side (P < 0.05, paired t-test). The fraction maximal voluntary contraction force/CSA had decreased by up to 76.4% +/- 25.5 (P < 0.05, paired t-test). An increased fatigability of the affected muscles persisted in all patients. The patients' noninjured extremity behaved in the same way as that of the dominant extremity of normal volunteers with regard to force, lever, and CSA values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

Dependence of blood clot lysis on the mode of transport of urokinase into the clot--a magnetic resonance imaging study in vitro.

Magnetic resonance imaging was employed to study the dependence of clot lysing patterns on two different modes of transport of urokinase into whole blood clots. In one group of clots (nonperfused clots, n1 = 10), access of urokinase to the fibrin network was possible by diffusion only, whereas in the other group (perfused clots, n2 = 10) bulk flow of plasma containing urokinase was instituted through occlusive clots by a pressure difference of 3.7 kPa (37 cm H2O) across 3 cm long clots with a diameter of 4 mm. It was determined separately that this pressure difference resulted in a volume flow rate of 5.05 +/- 2.4 x 10(-2) ml/min through occlusive clots. Perfused clots diminished in size significantly in comparison to nonperfused ones already after 20 min (p less than 0.005). Linear regression analysis of two-dimensional clot sizes measured by MRI showed that the rate of lysis was more than 50-times faster in the perfused group in comparison to the nonperfused group. It was concluded that penetration of the thrombolytic agent into clots by perfusion is much more effective than by diffusion. Our results might have some implications for understanding the differences in lysis of arterial and venous thrombi.

Biological Transport↗

Electron spin resonance imaging of tissues with lipid-rich areas.

Electron spin resonance imaging and spectroscopy of lipid-rich samples were studied at 9 Ghz. Using both lipid- and aqueous-soluble nitroxides good delineation of fat- and muscle-rich regions of tissue was obtained. Several different principles can be used to differentiate between these types of tissues and potentially between different types of lipids. These principles include lipophilicity of nitroxides, viscosity (which is higher in lipids), oxygen solubility (oxygen is four times more soluble in lipids), and the distribution of paramagnetic metal ions. These techniques have potential applicability for directly studying metabolism and oxygen concentration in tissues by ESR techniques and for investigating potential contrast agents for in vivo NMR techniques.

Adipose Tissue↗

Contrast enhancement in experimental radiation-induced liver injury: comparison of hepatocellular and reticuloendothelial particulate contrast agents.

We compared the liver enhancement of two superparamagnetic agents, polycrystalline iron oxide nanoparticles (PION) and PION coated with asialofetuin (ASF), in an experimental model of focal radiation-induced hepatitis. PION, a reticuloendothelial system-directed agent, and PION-ASF, a hepatocellular-directed agent, were compared for time-dependent liver enhancement in an experimental model of radiation-induced liver injury. Using the reticuloendothelial system (RES)-directed PION, the normal, nonirradiated portion of the liver decreased in signal intensity (SI) with a mean negative enhancement of -66% +/- 4, whereas the irradiated portion (60 Gy, 3 days before imaging) of the liver decreased in SI by -24% +/- 2, significantly less (P <.05). SI changes in irradiated liver tissue using PION were dose-dependent, being more pronounced with lower radiation exposure. The difference in SI changes induced by PION-ASF between irradiated and nonirradiated liver was not statistically different, but SI decreased with a mean negative enhancement of -80% +/- 2. The RES-directed PION is more sensitive for the detection of radiation-induced hepatitis than is the hepatocyte-directed PION-ASF. The insensitivity of PION-ASF enhancement for diffuse liver injury may be clinically advantageous for detecting focal lesions in the presence of diffuse hepatic injury.

Animals↗

Comparison of albumin-(Gd-DTPA)30 and Gd-DTPA-24-cascade-polymer for measurements of normal and abnormal microvascular permeability.

The purpose of this study was to compare a new MR macromolecular contrast medium (MMCM), gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)-24-cascade-polymer, to a well-studied prototype MMCM, for the potential of distinguishing tissues of varying endothelial permeability. Three tissue models of varying capillary permeability were studied in a total of 46 rats: normal myocardium (normal capillaries), subcutaneously implanted adenocarcinoma (mild capillary leak), and reperfused infarcted myocardium (high capillary leak). TI-weighted MRI was performed before and dynamically after injection of either albumin-(Gd-DTPA)30 or the cascade polymer (each .02 mmol gadolinium [Gd] per kg). Data analysis based on a two-compartment kinetic model yielded estimates of fractional blood volume (BV) (percentage) and fractional leak rate (FLR) (1 per hour). Permeability to the cascade polymer as reflected in FLR was considerable in normal myocardium (8.24 per hour), of similar value in tumors (8.55 per hour), but significantly greater in infarcted myocardium (39.17 per hour, P < .01) versus normal myocardium. The larger albumin-(Gd-DTPA)30 demonstrated minimal extravasation in normal myocardium (FLR .33 per hour); FLR in tumors was 100% higher (.66 per hour, P < .002) and FLR in reperfused capillaries was significantly greater (7.94 per hour, P < .001). Based on capillary permeability measurements, the cascade polymer may have limited utility for detection of mildly increased microvascular permeabilities. For severe tissue injury, the cascade polymer can resolve abnormal microvascular integrity.

Analysis of Variance↗