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R Felix

Publications and source records attributed to R Felix.

1,036 records · Page 58Linked to original sources
PubMedDate not supplied

Time-dependent changes in image contrast in brain tumors after gadolinium-DTPA.

Time-dependent changes in the contrast enhancement of tumor tissue, tumor necrosis, perifocal edema, and normal brain tissue after IV injection of 0.1 mmol gadolinium-DTPA/kg body weight were studied with spin-echo technique (SE 800/35) in 15 patients with intracranial tumors. Using a region of interest technique, we determined the signal-intensity values of these tissues before and at fixed times up to 68.5 min after administration of the contrast agent. In tumor tissue, the 8.5 min postinjection (p.i.) scan showed a significant increase in signal intensity. The signal intensity of the tumor tissue remained significantly higher than precontrast levels throughout the entire period of observation, decreasing only slightly toward the end of the examination (48.5 and 68.5 min p.i.). Central tumor necrosis exhibited a delayed uptake of the contrast agent, with a maximum signal intensity between 48.5 and 68.5 min p.i. In perifocal edema and normal brain tissue, slight increases in signal intensity after injection of gadolinium-DTPA were measured (statistically significant in the case of edema). This effect, however, was not visually detectable. The present study shows that after one injection, scans with excellent tumor visualization can be obtained between 8.5 and 38.5 min p.i. and with diagnostically valid enhancement at least up to 68.5 min p.i.

Adult↗
PubMedDate not supplied

Gadolinium-DTPA in MR imaging of glioblastomas and intracranial metastases.

In 14 patients with the diagnosis of glioblastoma (n = 7) or intracranial metastases (n = 7), magnetic resonance (MR) imaging was performed using a variety of spin-echo (SE) pulse sequences before and after intravenous injection of 0.1 mmol gadolinium-DTPA (Gd-DTPA) per kilogram of body weight. In 10 patients, tumor tissue could not be adequately differentiated from perifocal edema on unenhanced scans with any of the applied pulse sequences. In four cases of intracranial metastases, poor differentiation between tumor and perifocal edema was possible in T2-weighted (SE 1600/70 and SE 1600/105) unenhanced scans. After administration of Gd-DTPA, tumor tissue showed marked contrast enhancement, and tumor delineation was consistently possible on SE 800/35 images. Tumor tissue could be differentiated from perifocal edema on SE 800/70 scans. Gd-DTPA is likely to increase the potential of MR imaging and refine the evaluation of glioblastomas and intracerebral metastases.

Adult↗
PubMedDate not supplied

Gadolinium-DTPA: a new contrast agent for magnetic resonance imaging.

Gd-DTPA-dimeglumine is a new contrast agent for magnetic resonance imaging. Its safety and efficacy in man were evaluated in 20 volunteers and 60 patients. For determination of tolerance of Gd-DTPA, blood and urine samples were taken and blood pressure, pulse rate, and ECG were recorded before and after injection. The results of these analyses showed no clinically relevant changes. In MR imaging of intracranial lesions Gd-DTPA serves as an indicator of function or disfunction of the blood-brain-barrier, because its pharmacokinetic behavior is very similar to that of urographic iodinated contrast media used now for X-ray CT. And so by using Gd-DTPA it is possible to differentiate between neoplastic tissue and perifocal edema, to determine the extension of tumor infiltration, and to detect tumor recurrence.

Contrast Media↗
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Liver transplantation: significance of the periportal collar on MRI.

OBJECTIVE: Liver transplantation is performed with increasing success and frequency all over the world. Experience with MRI of the liver allograft is, however, limited. This study was designed to correlate MRI to clinical-laboratory findings, CT, and biopsy and to evaluate the significance of the periportal collar on MRI. MATERIALS AND METHODS: Fourteen patients who had undergone orthotopic liver transplantation were studied by CT and MRI [T1-weighted imaging: gradient-echo, repetition time/echo time (TR/TE) 306/14 ms, theta 90 degrees; proton density and T2-weighted imaging: spin-echo, TR/TE 1,600/30-120 ms]. Three patients also had follow-up MR examinations 43 days, 89 days, and 5 months after transplantation. RESULTS: Magnetic resonance imaging demonstrated a perivascular collar around central portal venous branches in all 14 patients and around peripheral portal branches in 10 of the 14 patients on the initial MRI study. The perivascular collar showed low signal intensity on T1-weighted imaging and an increase in signal intensity on T2-weighted multiecho imaging. The distribution and prevalence of central and peripheral periportal collars were identical on MR and CT. Peripheral periportal collars were seen in 9 patients who had no clinical-laboratory signs of rejection. In 3 patients with biopsy-proved rejection, the periportal collar was less prominent on MR at the time of rejection when compared with MR performed when the patient had no signs of transplant rejection. CONCLUSION: A perivascular collar in a patient with liver transplantation is likely to be related to impaired lymph drainage after surgical interruption of the draining lymph vessels and lymphedema. In contrast to previous CT reports, however, a perivascular collar around peripheral portal branches does not appear to correlate to rejection, since it is frequently observed in the normal liver allograft.

Adult↗
PubMedDate not supplied

Endoscopic management of biliary complications after orthotopic liver transplantation.

BACKGROUND/AIMS: Biliary complications after orthotopic liver transplantation are still a severe problem and often require a second surgical operation. MATERIAL AND METHODS: In our center we studied 500 patients after liver transplantation. RESULTS: In this patient population, we found 44 patients suffering from diseases of the bile duct system after liver transplantation. Biliary complications were caused by stenoses which were localized most often in the common bile duct of the recipient (65%) but also in the common bile duct of the donor liver (26%) as well as in the anastomosis of common bile duct (9%). In all cases ERC was able to identify location, entity and dimension of the biliary complication thus leading to therapeutic strategy. 66% (27 out of 41) of the patients with biliary complication could be cured definitely by endoscopic methods alone while 29% (12 out of 41) of these patients needed surgical operation and 5% (2 out of 41) received both, endoscopic and surgical therapy. Patients suffering from multiple complications could be cured partially by endoscopic methods improving patient condition for subsequent surgery. Ischemic type biliary lesions of the extrahepatic ducts (ITBL type I) as well as of the intrahepatic ducts (ITBL type II) could be successfully treated by endoscopy. Only rare cases of multiple lesions intra- and extrahepatically due to ITBL type III gave no chance to endoscopy and demanded directly surgical operation. CONCLUSIONS: Our results show that most of the biliary complications after liver transplantation can be resolved by endoscopic treatment.

Biliary Tract Diseases↗
PubMedDate not supplied

Dynamic change in the left ventricular base with or without a rigid mitral valve prosthesis.

To evaluate the narrowing of the left ventricular outflow tract (LVOT) during systole caused by a rigid mitral prosthesis, the geometric relationship between the prosthesis (or the mitral annulus) and the left ventricular base (LVB) was studied in five patients with mechanical mitral valve prostheses and eight normal subjects. The images of the mitral valve annulus (MVA) and the LVOT orifice reconstructed in three dimensions were projected on the plane of the LV base. Calculating the areas of these projected images (i.e., those for MVA [Sm], LVOT orifice [So], the LVB [Sb; Sb = Sm + So]), the MVA-LVB ratio (Sm/Sb) was determined. In the normal subject, the MVA-LVB ratio was nearly constant during systole (59 +/- 5% at 0 msec and 62 +/- 7% at 300 msec, respectively), whereas in the patients with prostheses, the ratio increased from 61 +/- 4% (0 msec) to 69 +/- 4% (300 msec). The increase in MVA-LVB ratio reduces the proportionate share of LVOT orifice in relation to the total LVB. The ideal mitral valve prosthesis should be flexible at the annulus to attain good performance in LVB dynamics.

Adult↗