Search PubMed⌕ Search

Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 163 records · Page 9Linked to original sources
PubMed2000

[The correlation between the CD4 count in HIV-positive patients and the radiological findings in diseases of the paranasal sinuses].

BACKGROUND AND OBJECTIVE: Sinusitis is a frequent and typical disease in HIV-positive patients. It was the aim of this study to examine retrospectively computed tomograms (CT) and magnetic resonance images (MRI) of such patients for sinusitis. PATIENTS AND METHODS: CT and MRI of the nasal sinuses were retrospectively analysed in 71 HIV-positive patients. RESULTS: Sinusitis was diagnosed in 49 of the 71 patients by conventional radiology (38), CT (13) and/or MRI. In patients with sinusitis, contrary to those without it, there was a significant correlation between progression of the HIV infection, as measured by reduction in CD4 count, and an increased number of symptoms (r = -0.297; p < 0.05). The latter also correlated significantly with the frequency of concomitant sinusitis (r = 0.336, p < 0.05). The radiological findings correlated more closely with the CD4 count when tomography was used. The correlation coefficient for the number of patients with concomitant sinus disease rose from r = -0.305 to r = -0.459 and for the degree of severity from r = -0.324 to r = -0.484 (p < 0.05). Severity of sinus disease was clearly more marked among HIV-positive than HIV-negative patients. CONCLUSION: The severity of sinusitis in HIV-positive patients correlated directly with the level of the CD4 count. In these patients tomographic methods are preferable to conventional radiology.

AIDS-Related Opportunistic Infections↗
PubMed2000

Is absolute noninvasive temperature measurement by the Pr[MOE-DO3A] complex feasible.

Recently, the feasibility of the praseodymium complex of 10-(2-methoxyethyl)-1,4,7,10-tetraaza-cyclododecane-1,4,7-tr iacetate (Pr[MOE-DO3A]) for non-invasive temperature measurement via 1H spectroscopy has been demonstrated. Particularly the suitability of the complex for non-invasive temperature measurements including in vivo spectroscopy without spatial resolution as well as first spectroscopic imaging measurements at low temporal resolution (> or = 4 min) and high temporal resolution (breath hold, approximately 20 s) has been shown. As of today, calibration curves according to the particular experimental conditions are necessary. This work aims to clarify whether the Pr[MOE-DO3A] probe in conjunction with 1H-NMR spectroscopy allows non-invasive absolute temperature measurements with high accuracy. The measurement results from two different representative media, distilled water and human plasma, show a slight but significant dependence of the calibration curves on the surrounding medium. Calibration curves in water and plasma were derived for the temperature dependence of the chemical shift difference (F) between Pr[MOE-DO3A]'s OCH3 and water with F = -(27.53 +/- 0.04) + (0.125 +/- 0.001) x T and F = -(27.61 +/- 0.02) + (0.129 +/- 0.001) x T, respectively, with F in ppm and T in degrees C. However, the differences are minuscule even for the highest spectral resolution of 0.001 ppm/pt, so that they are indistinguishable under practical conditions. The estimated temperature errors are +/- 0.18 degrees C for water and +/- 0.14 degrees C for plasma and with that only slightly worse than the measurement accuracy of the fiber-optical temperature probe (+/- 0.1 degrees C). It can be concluded that the results obtained indicate the feasibility of the 1H spectroscopy method in conjunction with the Pr[MOE-DO3A] probe for absolute temperature measurements, with a maximum accuracy of +/- 0.2 degrees C.

Agar↗
PubMed2000

MRI and 18F-fluorodeoxyglucose positron emission tomography in hemimegalencephaly.

We report hemimegalencephaly in a 44-year-old woman with mental retardation, epilepsy and a mild hemiparesis. In addition to typical findings on MRI, 2-deoxy-2[18F]fluorodeoxyglucose positron-emission tomography (PET) demonstrated glucose hypometabolism of the affected hemisphere. The results of PET have been coregistered with morphological information from the MRI studies by image fusion.

Adult↗
PubMed2000

MRI in decompression illness.

We report a case of decompression illness in which the patient developed paraparesis during scuba diving after rapid ascent. MRI of the spine revealed a focal intramedullary lesion consistent with the symptoms. The pathophysiological and radiological aspects of spinal decompression illness are discussed.

Adult↗
PubMed2000

Prospective comparison of endorectal ultrasound, three-dimensional endorectal ultrasound, and endorectal MRI in the preoperative evaluation of rectal tumors. Preliminary results.

BACKGROUND: The aim of this study was to compare the value of endorectal ultrasound (EUS), three-dimensional (3D) EUS, and endorectal MRI in the preoperative staging of rectal neoplasms. METHODS: Thirty consecutive patients with rectal tumors were assessed by EUS and endorectal MRI. Additionally, three-dimensional ultrasound was performed in a subgroup of 25 patients. EUS data were obtained with a bifocal multiplane transducer (10 MHz) and processed on a 3D ultrasound workstation. MR imaging was carried out with a 1. 5 T superconducting unit using an endorectal surface coil. RESULTS: EUS was carried out successfully in all 30 patients, whereas endorectal MRI was not feasible in two patients. Compared with the histopathological classification, EUS and endorectal MRI correctly determined the tumor infiltration depth in 25 of 30 and 28 patients, respectively. The comparative accuracy of EUS, 3D EUS, and endorectal MRI in predicting tumor invasion was 84%, 88%, and 91%, respectively. EUS, three-dimensional EUS, and endorectal MRI enabled us to assess the lymph node status correctly in 25, 25, and 24 patients, respectively. Both three-dimensional EUS and endorectal MRI combined high-resolution imaging and multiplanar display options. Assessment of additional scan planes facilitated the interpretation of the findings and improved the understanding of the three-dimensional anatomy. CONCLUSION: The accuracy of three-dimensional EUS and endorectal MRI in the assessment of the infiltration depth of rectal cancer is comparable to conventional EUS. One advantage of both methods is the ability to obtain multiplanar images, which may be helpful for the planning of surgery in the future.

Adult↗
PubMed2000

[The T2-weighted half-Fourier acquired single-shot turbo-spin-echo technic compared to the conventional T2-weighted turbo-spin-echo technic for cerebral magnetic resonance tomography. A sequence comparison].

PURPOSE: To compare a T2-weighted half-fourier acquired single-shot turbo spin-echo (HF-TSE) sequence (HA-STE-sequence) for cerebral MRI with a standard T2-weighted fast spin-echo (TSE) sequence. MATERIALS AND METHODS: Signal-to-noise (SNR) and contrast-to-noise ratios (CNR) for different cerebral structures, and intracerebral lesions as well as the detectability of intracerebral lesions depending on size and relaxation properties were evaluated on cranial MR examinations of 46 patients with both a TSE and a HF-TSE sequence. RESULTS: SNR and CNR were found to be significantly higher with the TSE sequence for all normal structures and lesions except CSF, and lesions with short relaxation time T2 (p < 0.001). The number of detected lesions larger than 10 mm was similar with both sequences. Thirty-six (TSE) and 34 (HF-TSE) hyperintense, and 7 (TSE) and 2 (HF-TSE) hypointense lesions of at least 5 mm but less than 10 mm in size were detected. Thirty-three (TSE) and 10 (HF-TSE) hyperintense, and 2 (TSE) and no (HF-TSE) hypointense lesions smaller than 5 mm were detected. CONCLUSION: Due to its short acquisition time, the HF-TSE sequence is an alternative for MR examinations of non-compliant or claustrophobic patients. The low SNR and CNR relative to the TSE-technique are limiting factors as to the detectability of small lesions or lesions with low contrast to surrounding structures, with the risk of an increasing number of false negative results in lesions with short T2 relaxation time smaller than 10 mm.

Artifacts↗
PubMed2000

[Ultrasonographically guided puncture technique for central venous vessels as a one-person technique].

AIM: The traditional anatomic landmark technique usually allows a rapid and easy central venous access but this technique is not always successful and can be associated with severe complications. We developed an ultrasonically guided one-operator-catheterization technique whereas a second operator to place and hold the ultrasound transducer is not necessary. METHOD: The catheterisation technique consists of 3 functional components: the swivel arm, the ultrasound unit and the conventional Seldinger central venous catheterization technique. As swivel arm we used a device with a 300 mm column with a 700 mm span attached to ultrasound unit. There were 234 catheterizations of the internal jugular vein performed in the period of January 1999 to July 1999. The indication and complication rate for the catheterization procedure was documented. RESULTS: There were 2 plexus irritations and 1 hematoma observed in all performed catheterization procedures which remained without therapeutic consequences. CONCLUSION: Once the decision for central venous access has been made the safest technique should be applied. The ultrasonically guided catheterization technique allows a fast, safe and convenient central venous access for our patients.

Catheterization, Central Venous↗
PubMed2000

[Fusion of CT and PET data: methods and clinical relevance for planning laser-induced thermotherapy of liver metastases].

AIM: Catheter-placement in liver metastases is difficult when the lesions are not visible on plain images. We evaluated the use of image fusion using CT and PET data, providing information on anatomy and liver lesions, respectively. METHODS: Plain CT of the liver and whole body FDG-PET were performed in 28 patients with colorectal carcinoma in preparation for laser-induced thermotherapy. Fusions of image data and 2D-visualisation were performed and evaluated with regard to quality of the registration, number of detected lesions and influence of the procedure on laser-induced thermotherapy. Image fusion was performed using an algorithm which was developed by our group. RESULTS: 84 focal liver lesions were visible on CT, 107 on PET images. This means that CT guided catheter placement would have to be performed "blindly" in 23 lesions. In 6 patients previously unknown extra-hepatic tumor deposits were seen on PET images (local recurrence, 2 extrahepatic metastases, 2 second primaries). CONCLUSION: Hot spots from metastases, which are difficult to locate on PET images alone, may be identified on images generated by fusion of CT and PET data. These images facilitate an interventional approach to liver lesions which are not visible on plain CT. As PET allows for whole body screening, it helps identifying patients who would not profit from laser-induced thermotherapy.

Algorithms↗
PubMed2000

[Pre- and postoperative evaluation of ventricular function, muscle mass and valve morphology by magnetic resonance tomography in Ebstein's anomaly].

PURPOSE: To evaluate the value of MRT with spin echo (SE) and CINE gradient echo (GE) sequences for the pre- and postoperative assessment of patients with Ebstein's anomaly. METHODS: Twelve patients within the ages of four to 49 years (mean 22 +/- 12 years) were examined pre- (n = 5) or postoperatively (n = 7) after tricuspid valve reconstruction with a 1.5 T scanner. For the anatomical assessment, an ECG-gated transverse SE-sequence, for the assessment of valve morphology and function as well as for volumetry a CINE GE-sequence with retrospective gating was used. With the use of the multislice-multiphase technique, after summing up the manually outlined epi- and endocardial areas, endsystolic (ESV) and enddiastolic volumes (EDV), ejection fraction (EF), stroke volume (SV), and muscle mass (MM) were calculated for both ventricles. RESULTS: The differentiation of the displaced parts of the tricuspid valve (TV) was insufficient with static SE, but was possible in all patients with CINE-MRT. Like in Doppler echocardiography, a qualitative assessment of tricuspid insufficiency was possible in CINE-MRT, the mean incompetence grade preoperative was 1.8 (+/- 0.8), postoperative 0.7 (+/- 0.5). The mean RV-EF in the preoperative group was 41.8% (+/- 6.4), in the postoperative group 47.9% (+/- 10.6), the mean LV-EF preoperative 47.4% (+/- 8.5%), postoperative 63.0% (+/- 9.4). CONCLUSION: CINE-MRT should rather be used than SE for the assessment of valve morphology. EF, muscle mass and tricuspid incompetence can also be calculated pre- and postoperative with CINE-MRT.

Adolescent↗
PubMed2000

[Imaging of intra-arterial hepatic port catheter systems by power-doppler sonography using contrast media--preliminary results].

AIM: This study was designed to determine whether intra-arterial hepatic port catheter systems can be adequately detected by contrast-enhanced power-Doppler sonography. METHOD: 15 patients with a liver port system were investigated before chemotherapy. Examinations were performed with short bolus injections of the contrast medium Levovist in addition to angiographic imaging. RESULTS: Liver port systems were easily detected by the contrast-enhanced power-Doppler method. In 11 out of 15 patients a correct flow of the contrast medium via the port system was seen with both examination methods. One partially occluded hepatic artery was not identified by power-Doppler despite correct flow of the contrast fluid. In one of three patients showing an incorrect flow of the contrast medium the blood circulated primarily through the splenic artery due to a dislocation of the catheter tip. Circulation through both the hepatic and the splenic arteries was shown in a second patient and an occluded right hepatic artery was demonstrated in a third. All these findings were observed with both examination techniques. CONCLUSION: Power-Doppler sonography provides a reliable image of the port catheter system. This method can be used as a follow-up procedure to determine the state of arterial hepatic circulation during chemotherapy.

Aged↗
PubMed2000

Pulmonary disease in liver transplant recipients. Spectrum of CT features.

PURPOSE: To determine the features of pulmonary disease in liver transplant recipients by CT. MATERIAL AND METHODS: Of 792 patients, 102 were referred to thoracic CT 3-2093 days after the transplantation procedure (median 107 days). All CT studies were retrospectively analyzed and correlated with clinical, microbiological, serological and histopathological findings. RESULTS: Eighty-eight of 102 patients (86%) had an abnormal CT. In 25 patients (25%), an elevated right hemidiaphragm, basal atelectasis and small effusions were the only abnormalities. Fourty-one patients (40%) displayed an infiltrate and 13 (13%) a mass lesion. Evidence of cytomegalovirus (CMV) infection was found in 20 patients. CMV pneumonia was suggested by an interstitial pattern of pneumonia on CT (n=13). Pneumocystis carinii pneumonia was highlighted by peribronchovascular infiltrates (n=5/8), bacterial pneumonia (n=24) including legionellosis (n= 13) by bilateral effusions (n=14) and lobar consolidation (n= 13). In 7/41 patients (17%) with both clinically apparent pulmonary disease and CT signs of pneumonia, no pathogen could be detected. Neoplastic disease was mostly due to tumor recurrence (n=6). CONCLUSION: Thoracic CT of liver transplant recipients aids in detecting and classifying both infectious and neoplastic complications.

Adolescent↗
PubMed2000

Transjugular intrahepatic portosystemic shunt. Experiences at a liver transplantation center.

OBJECTIVE: Transjugular intrahepatic portosystemic shunt (TIPS) placement is an established therapy for portal hypertension that leads to variceal bleeding or refractory ascites. We present experiences of the role of TIPS at a liver transplantation center. MATERIAL AND METHODS: One hundred and ten patients were referred to the Radiological Department for TIPS placement. One of the 110 patients had recurrent cirrhosis after liver transplantation with refractory ascites. Function of the TIPS was controlled with Doppler US at 1 day, 1 week, 4 weeks and 4 months after TIPS placement and subsequently every 3 months. Shunt insufficiency was supposed when the blood flow velocity within the stent tract was under 50 cm/s and was an indication for TIPS revision. RESULTS: TIPS was placed in 101 patients. After TIPS placement, 10 patients underwent liver transplantation. While waiting for the new liver, none of them developed variceal rebleeding, ascites or other complications of portal hypertension. Two of the 101 patients had episodes of rebleeding. The frequency of patients undergoing TIPS revision within the first year after TIPS placement was 67.5%, within the second year 38.0% and within the third year 24.4%. The revisions led to sufficient reduction of the portosystemic pressure gradient. CONCLUSION: In some liver transplant candidates, TIPS can be useful in minimizing the risk of complications of portal hypertension during the waiting time for a liver transplantation. TIPS can be monitored by Doppler US and revised if occlusion occurs.

Adult↗
PubMed2000

Laser angioplasty of peripheral arteries after unsuccessful recanalization of the superficial femoral artery.

AIM: To demonstrate the range of applying laser angioplasty after unsuccessful recanalization of the superficial femoral artery (SFA) with conventional interventional techniques. MATERIALS AND METHODS: In a prospective trial in 94 cases with occlusion of the SFA and formerly unsuccessful conventional percutaneous transluminal angioplasty, laser angioplasty for recanalization was applied. The average occlusion length of the SFA was 17.5 cm (range 4-36 cm). The recanalization attempt was made using the crossover technique in 78 patients, in eight patients with the antegrade technique and in another eight patients using the transpopliteal technique. The primary recanalization attempt was performed with Terumo wires (curved and straight) as well as different catheters (Multipurpose/Vertebralis/Cobra). After the unsuccessful recanalization attempt the laser catheter was applied. RESULTS: The application of laser angioplasty demonstrated a successful recanalization of the SFA in 76/94 patients (80.9%). In 18 patients (19.1%) the recanalization was not possible even with percutaneous transluminal laser angioplasty (PTLA). The reason for the unsuccessful PTLA was in 10 cases due to obstructing calcified material, which was resistant to PTLA application. In four cases obstructing calcifications caused the laser catheter to be positioned in subintimal tissue, resulting in perforation of the SFA. In another four patients there was an aberrant anatomy of the SFA which resulted in a direct vessel injury after advancing the laser catheter. After a follow-up period of 12 months primary, primary-assisted and secondary patency rates were 50.0%, 65.8% and 73.7%, respectively. DISCUSSION: In primarily unsuccessful recanalization of the SFA, PTLA allows in 80% of cases a successful recanalization of the SFA. The technical success rate and the patency rate support the application of PTLA.

Journal Article↗
PubMed2000

Treatment of postinterventional pseudoaneurysms by ultrasound-guided compression.

RATIONALE AND OBJECTIVES: This 3-year study was performed to evaluate the effectiveness and safety of ultrasound-guided compression (UGC) in the treatment of postinterventional pseudoaneurysms (PAs). METHODS: One hundred ten PAs were sonographically diagnosed after peripheral or cardiac interventions. In 98 patients (65 men and 33 women; age range, 44-79 years), UGC was performed. The PAs were related to the common femoral artery (n = 78), the superficial femoral artery (n = 26), the profound femoral artery (n = 2), and the distal external iliac artery (n = 4). The PAs showed diameters ranging from 0.8 to 9.86 cm (mean, 4.8 cm) and volumes between 0.6 and 109 mL (mean, 15.6 mL). Follow-up examinations including color Doppler-coded ultrasound and peripheral Doppler were performed after 18 hours +/-6 and 28 days +/-4. RESULTS: Complete closure of the PA and its neck was achieved by UGC in 96 of 98 cases (98%). In 86 of 98 cases (87.8%), UGC was successful during the first session; a second treatment was needed in 10 cases. The compression time varied from 12 to 85 minutes (mean, 35.6 minutes). Except for medically controllable vagal reactions in 4 of 98 cases (4.1%) and 1 easily controlled PA rupture, no treatment-related complications were observed. CONCLUSIONS: According to the effectiveness and safety results, we conclude that UCG is the method of choice in the treatment of postinterventional PAs. Diagnosis and UGC treatment should be performed as early as possible to minimize symptoms and hospitalization time.

Adult↗
PubMed2000

Assessment of the vascularization of neuroendocrine tumors by stimulated acoustic emission of SH U 508A ultrasound contrast agent and color or power Doppler sonography.

RATIONALE AND OBJECTIVES: To assess the vascularization of neuroendocrine tumors by stimulated acoustic emission (SAE) of SH U 508A during the blood pool phase in comparison with contrast-enhanced Doppler sonography. METHODS: Thirty-six patients with neuroendocrine tumors received contrast-enhanced Doppler sonography and 21, an additional SAE. To classify tumor perfusion on Doppler sonography, a 4-step rating score was introduced: (1) no vessels (hypoperfusion); (2) one feeding or central vessel (hypoperfusion); (3) some vessels (hyperperfusion); and (4) disseminated vessels (hyperperfusion). In 36 patients, 1 pancreatic primary tumor, 33 liver metastases, 1 splenic metastasis, and 1 lymph node metastasis were examined. Results were correlated with biphasic spiral CT (n = 35) and angiography (n = 2). RESULTS: Arterial-phase CT and digital subtraction angiography revealed 18 hyper- and 18 hypoperfused lesions. Contrast-enhanced Doppler correctly classified 15 of 18 patients (83%) with hyperperfused lesions as well as 16 of 18 (89%) hypoperfused tumors by applying the rating score. SAE correctly identified 4 of 9 hyperperfused lesions (44%), 2 were isoperfused compared with normal liver tissue (22%), and 3 were hypoperfused (33%). Of 12 hypoperfused lesions, 11 were classified correctly (92%), and 1 showed isoperfusion. Hence, the positive and negative predictive values for SAE were 80% and 69%, respectively. For contrast-enhanced Doppler sonography, positive and negative predictive values were 88% and 84%, respectively. CONCLUSIONS: Blood pool SAE failed to determine subtle tumor perfusion correctly. The rating score for contrast-enhanced Doppler sonography characterized tumor perfusion with high accuracy. The use of a contrast agent significantly improved perfusion characterization.

Angiography, Digital Subtraction↗
PubMed2000

Preoperative contrast-enhanced MRI of the parathyroid glands in hyperparathyroidism.

RATIONALE AND OBJECTIVES: To evaluate the sensitivity of contrast-enhanced MRI in the preoperative detection of abnormal parathyroid glands in patients with clinical evidence of hyperparathyroidism. METHODS: Twenty-eight patients with biochemical evidence of hyperparathyroidism underwent contrast-enhanced preoperative MRI of the parathyroid glands. Two blinded readers assessed the MR images by consensus, and MR results were subsequently correlated with those from surgery (location, diameter, weight) and histopathology. RESULTS: MRI depicted 32 of 39 surgically proved abnormal parathyroid glands (sensitivity 82%; 95% confidence interval, 66%-92%), and 1 of 114 (0.9%) was incorrectly considered abnormal. All ectopic glands were correctly identified (2 mediastinal, 1 submandibular). Sensitivity was superior for adenomas but less for hyperplasia (adenomas 87%; 95% confidence interval, 67%-97%; hyperplasia 75%; 95% confidence interval, 47%-92%). Among all lesions, atypical signal characteristics on MRI were observed in 34% of lesions (9% hyperintense signals on T2- and T1-weighted images; 25% isointense signals on T2- and T1-weighted images), with improved lesion detection after contrast administration in 17% of lesions. CONCLUSIONS: MRI of the parathyroid glands presented a sensitive imaging modality, thus demonstrating its high potential to preoperatively detect abnormal glands. Moreover, in a minor proportion of patients with atypical parathyroid lesion characteristics, contrast administration may increase lesion detectability.

Adenoma↗