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Biomedical subjects

D Szolar

Publications and source records attributed to D Szolar.

30 records · Page 2Linked to original sources
PubMed1996

Differentiation of delayed kidney graft function with gadolinium-DTPA-enhanced magnetic resonance imaging and Doppler ultrasound.

RATIONALE AND OBJECTIVES: The authors differentiate acute tubular necrosis from transplant rejection in patients with delayed kidney graft function using gadolinium (Gd)-DTPA enhanced magnetic resonance (MR) imaging. METHODS: Twenty-four patients after renal transplantation (10 with normal graft function, 14 with delayed graft function) underwent conventional and Doppler sonography and MR imaging examination after bolus application of Gd-DTPA. Within a time period of 512 seconds, 39 single-slice MR images were obtained. Measurements of signal intensity in three regions of interests (cortex, medulla, renal pelvis) resulted in a graphic description of the dynamics of the contrast enhancement. The time between the start of the scan and the peaks of the curves was measured. RESULTS: In patients with normal graft function the curves reached the peaks between 39 and 55 seconds (cortex), 44 and 61 seconds (medulla), and between 161 and 318 seconds (renal pelvis). Six patients with acute tubular necrosis showed normal values for the curves 1 and 2 but markedly prolonged time for curve 3 (between 420 and 512 seconds). In all patients with histologically proven transplant rejection, the peaks of all curves were not reached before the ends of the scans. CONCLUSION: The authors' preliminary results suggest that MR imaging seems to be a sensitive, noninvasive diagnostic tool to differentiate acute tubular necrosis from transplant rejection in the critical early postoperative period.

Adult↗
PubMed1996

Cerebral schistosomiasis: MR and CT appearance.

After returning from Africa, a 54-year-old man began to have episodes of headache and nausea, then a cerebral convulsion. Clinical and laboratory findings and response to chemotherapy indicated the diagnosis of cerebral schistosomiasis. Three lesions were seen on CT and MR studies: two appeared to be subacute intracerebral hematomas, one in the right parietal lobe and one in the frontal lobe; the third lesion, in the cortex of the left occipital lobe, appeared to be a cyst. These lesions could represent small granulomatous tissue reactions with secondary hemorrhages.

Brain Diseases↗
PubMed1994

The sphenoid sinus during childhood: establishment of normal developmental standards by MRI.

To obtain baseline standards of normal age-related development of the sphenoid sinus during childhood magnetic resonance images of the sphenoid sinus in 401 patients less than 15 years old were reviewed. T1-weighted sagittal and T2-weighted axial scans were evaluated for bone marrow conversion, development of pneumatization, spatial enlargement and septation of the sphenoid sinus. The sphenoid sinus had a uniformly low signal intensity (red bone marrow) on T1-weighted images in all children less than 4 months old. Signal intensity changes from hypo- to hyperintense (bone marrow conversion) started at age of 4 months. Onset of pneumatization was observed in 12% of the patients at age 13-15 months. By age 43-48 months, 85% of the patients showed pneumatization of the anterior part of the sphenoid bone. Pneumatization was complete in all patients older than 10 years. Enlargement of the sinus showed a characteristic profile in each dimension. Median septation was observed irregularly with age, with a maximum of 77%. Septum variants were noticed between 4.5% and 20%. The recognition of this phenomenon may serve as a reference for evaluating normal and abnormal development of the sphenoid sinus and may be of great value for diagnostic and therapeutic management of pathologic conditions of the child's sphenoid sinus and its surrounds.

Adolescent↗
PubMed1994

Relationship between heart rate threshold, lactate turn point and myocardial function.

We examined the relationship between heart rate threshold (HRT), lactate turn point (LTP) and myocardial function expressed as left ventricular ejection fraction (LVEF) determined by radionuclide ventriculography. Two groups of subjects (G I: N = 8; G II: N = 7) with and without a deflection of heart rate performance curve (HRPC) underwent sitting cycle ergometry. HRT (G I), aerobic threshold (AeT; G I, G II), and LTP (G I, G II) were determined by means of linear regression break point analysis. Also, a break point in LVEF performance curve (LVEFBP) was obtained. Power output at HRT and at LTP was not significantly different between G I and G II (272.5 +/- 38.7 W; 294.3 +/- 20.6 W). Power output at LVEFBP (G I: 182.6 +/- 31.7 W; G II: 211.8 +/- 21.5 W) was not significantly different to power output at LTP (G I: 194.2 +/- 32.7 W; G II: 215.2 +/- 24.4 W) and HRT (G I: 193.0 +/- 38.2 W). Significant differences (p < 0.05) could only be found between G I and G II for heart rate (HR) at LTP (G I: 163.5 +/- 5.8 b.min-1; G II: 154.4 +/- 6.7 b.min-1) and LVEF at the end of the load (LVEFend) (G I: 77.9 +/- 2.9%; G II: 71.3 +/- 7.0%). The drop of LVEF at LVEFBP was significantly related to LTP in all cases. The present data suggest that the noninvasive determination of anaerobic threshold by means of heart rate curve analysis is not always possible due to different response of myocardial function and heart rate to graded cycle ergometer exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Magnetic resonance assessment of age-related development of the sphenoid sinus.

Magnetic resonance images of the sphenoid sinus in 401 patients under 15 years old were reviewed to establish normal age-related standards. T1-weighted sagittal and T2-weighted axial scans were evaluated for bone marrow conversion, development of pneumatization, spatial enlargement and septation of the sphenoid sinus. The sphenoid sinus had a uniformly low signal intensity (red bone marrow) on T1-weighted images in all children less than 4 months old. Signal intensity changes from hypointense to hyperintense (bone marrow conversion) started at the age of 4 months. Onset of pneumatization was observed in 12% of the patients at age 13-15 months. By age 43-48 months, 85% of the patients showed pneumatization of the anterior part of the sphenoid bone. Pneumatization was complete in all patients older than 10 years. Enlargement of the sinus showed a characteristic profile in each dimension. Median septation was observed irregularly with age, with a maximum of 77%. Septum variants were noticed between 4.5% and 20%. Because paediatric sinus disease is a challenging problem in children, these results may be useful as baseline standards of normal age-related development of the sphenoid sinus during childhood.

Adolescent↗
PubMed1993

Malignant ureteral obstruction: preliminary results of treatment with metallic self-expandable stents.

Self-expandable metal stents 7 mm in diameter were percutaneously implanted into 13 ureters in 10 patients with malignant ureteral obstruction not amenable to double-J stent placement. In nine ureters, one stent was placed, and in four ureters, two overlapping stents were placed. Primary reconstitution of ureteral patency was achieved in all ureters. After 1-2 weeks, four ureters showed a urothelial reaction encroaching on the lumen of the ureter, and a double-J stent was placed coaxially. One ureter was occluded by urothelial hyperplasia 4 weeks after stent placement, and a double-J stent was therefore placed. One ureter was occluded 8 months after stent placement by distal tumor overgrowth. The other ureters showed no signs of obstruction during a follow-up of 3-14 (average, 5.8) months. Peristalsis was preserved at both ends of the stent in all ureters. The use of this stent alone or in combination with a double-J stent alleviated upper urinary tract obstruction and avoided external drainage in all patients.

Adult↗
PubMedDate not supplied

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↗
PubMedDate not supplied

Percutaneous cholangioscopy in obstructed biliary metal stents.

PURPOSE: To reevaluate the reasons for the occlusion of self-expanding biliary metal stents, on the basis of cholangioscopic findings. METHODS: Percutaneous transhepatic cholangioscopy (PTCS) was performed in 15 patients with obstructed biliary Wallstents. The reason for stent insertion was a malignant obstruction in 14 patients; 1 had a benign biliary stricture. Conventional noncovered stents had been inserted in 12 patients; in 3 cases a polyurethanecovered prototype Wallstent had been used. Stent occlusions occurred after 1-55 months. PTCS was performed with a 2.3-mm endoscope through an 11 Fr sheath. Biopsies were taken via the working channel of the endoscope. RESULTS: In all patients with noncovered stents the inner surface of the stent was highly irregular with seaweed-like protrusions (biopsy-proven granulation tissue). Stent incorporation varied from absent (n = 1) to subtotal (n = 8), but was always incomplete, no matter how long the stent had been in place. Tumor ingrowth was histologically proven in 2 patients. One patient had a large occluding concrement at the proximal end of the stent. In patients with covered stents, the inner surface appeared more regular; however, viable granulation tissue was found inside two stents and tumor ingrowth in one of them. CONCLUSION: PTCS showed that incorporation of the stent is virtually always incomplete. The factors contributing most to stent occlusion are the buildup of granulation tissue, bile sludge, and tumor overgrowth. Stone formation and tumor ingrowth can also be important, although less common causes of occlusion. A polyurethane stent covering could not prevent tumor ingrowth in one patient and the buildup of viable granulation tissue inside the stent in two further patients; mean stent patency in the three patients with such a stent was 3 months.

Aged↗
PubMedDate not supplied

Strength, elasticity, and plasticity of expandable metal stents: in vitro studies with three types of stress.

PURPOSE: Five types of expandable metal stents (Palmaz, Strecker, Gianturco, Cragg, and Wallstent) were subjected to standardized tests to obtain objective, comparable data of their mechanical characteristics. MATERIALS AND METHODS: The stents were subjected to area loads, point loads, and circular loads; the resistance of the stents to a continually increasing deformation was measured. Elasticity and deformation characteristics of the stents were also noted. Another experiment simulated the situation of the stent in an implanted state. The stents were covered with a thin self-adhesive foil to simulate optimal wall contact by limiting the mobility of the mesh struts. RESULTS: For all types of stress, the Palmaz stent showed the highest resistance but was completely inelastic. The Strecker stent and the Wallstent showed higher resistance when coated in foil (simulating good wall contact). The Gianturco stent showed the lowest resistances but was completely elastic. A point load on a Wallstent caused concentric constriction over a longer distance. CONCLUSIONS: Palmaz stents are appropriate for insertion into highly resistant obstructions. Strecker stents and Wallstents require good wall contact to achieve adequate strength. Because of their unique deformation characteristics, Wallstents may not function well if implanted into eccentric stenoses of tough consistency. The Gianturco stent showed the lowest resistances.

Alloys↗