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R Felix

Publications and source records attributed to R Felix.

At least 271 records · Page 15Linked to original sources
PubMed1998

[Doppler sonographic monitoring control of perfusion of hepatocellular carcinoma after arterial chemoembolization].

INTRODUCTION: 22 patients with hepato-cellular carcinomas were examined sonographically before and after intra-arterial chemo-embolisation. The aim was to evaluate different techniques for judging tumour morphology and for assessing changes in perfusion. MATERIAL AND METHODS: The morphological appearances and perfusion changes were analysed by means of colour coded duplex sonography and power Doppler sonography before and after intravenous contrast medium. Pulsatility (Pl) and resistance index (RI) were used as quantitative parameters for judging changes in perfusion. RESULTS: In 13 patients intra-tumoral arteries were identified by duplex sonography and in four patients only by the power Doppler procedure. In three patients arterial vessels could only be identified after intravenous contrast. In 9 patients it was possible to document a reduction in arterial perfusion following embolisation. The indices calculated from these findings gave no prognostic indication. DISCUSSION: The methods described give information concerning changes in perfusion of a tumour following chemo-embolisation and, in conjunction with CT and clinical findings, provide indications for further tumour embolisation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1998

[Signal-enhanced color-coded duplex sonography of reactively and metastatically enlarged lymph nodes].

PURPOSE: Prospective comparison of B-mode-, plain and signal-enhanced colour Doppler ultrasound to evaluate new criteria for assessment of the tumour status of enlarged cervical lymph nodes. METHODS: Colour Doppler sonography was performed before and after application of d-galactose in 35 patients with suspected lymph node metastases of the neck. Sonomorphology was analysed qualitatively, maximal flow rate, pulsatility index and resistance index were determined quantitatively. RESULTS: Signal enhanced Doppler revealed a typical vessel morphology of the lymph nodes facilitating differential diagnosis. In 23%, vascularisation of the lymph nodes was only visible after application of the signal-enhancing agent (benign: 44%, malignant: 5%). The measurement of flow velocity and the calculation of RI and PI did not lead to a reliable differentiation between malignant and benign lymph nodes whereas B-mode sonography yielded highly valid results. CONCLUSION: The application of d-galactose facilitates differentiation between malignant and benign lymph nodes.

Aged↗
PubMed1998

[Appearance of choroidal melanoma on high resolution MRI using 1.5T with a dedicated surface coil in 200 consecutive patients].

PURPOSE: Choroidal melanomas usually present a characteristic appearance in MRI. Differing characteristics can cause problems in differential diagnosis between melanomas and other masses in the globe. The purpose of this study was to evaluate the appearance of choroidal melanomas with MRI in a large consecutive patient group. METHODS: In a prospective study, 200 patients with choroidal melanomas were investigated with MRI using a 1.5 T scanner and a 5 cm surface coil. Both quantitative and qualitative evaluation of the resulting images was performed. RESULTS: 78.5% of the melanomas presented with homogeneous signal intensities within the tumor due to a homogeneous pigmentation whereas 21.5% of the melanomas demonstrated a mixed pigmentation. Signal intensities of the homogeneous melanomas in the plain T1-WI were moderately or markedly hyperintense compared to the vitreous in 29.3% and moderately or markedly hypointense in the T2-WI in 37.1%. An accompanying retinal detachment was found in 65.5% and an extraocular growth in 7.0%. CONCLUSIONS: In 10% to 37% we observed the typical well known MR appearance, including homogeneous high signal in the T1-WI and low signals in the T2-WI. For further differentiation, morphological criteria (e.g. shape, size, and position) were used, which are also discussed.

Choroid Neoplasms↗
PubMed1998

[Color doppler ultrasonography in peripheral artery occlusive disease: continuous application of a signal enhancer].

PURPOSE: The effect of continuous infusion of a signal enhancer on the diagnostic efficacy of Doppler ultrasound in peripheral artery disease was evaluated. METHODS: 35 patients with peripheral artery disease were investigated by Doppler ultrasound before and during infusion of a signal enhancer (Levovist). Femoral and popliteal arteries were examined. Angiographic diagnoses included occlusions (24) and stenoses (22). They were compared to plain and enhanced Doppler findings. Artefacts and effects on signal intensity were evaluated. RESULTS: An increased Doppler signal was observed starting 1 min 35 s (mean) after begin of the infusion. It persisted for 11 min 46 s (mean). Signal enhanced studies provided less over- (0/1) and underestimation (3/5) of the findings and evaluation in the adductor channel was less compromised. Signal enhanced studies highlighted collaterals. CONCLUSION: Doppler ultrasound in patients with peripheral arterial disease is improved by continuous application of a signal enhancer.

Adult↗
PubMed1998

[Use of high resolution color Doppler sonography in diagnosis of temporal arteritis].

PURPOSE: To define sonographic signs of arteritis temporalis using color coded duplex sonography. METHODS: 20 patients with clinically suspected temporal arteritis were examined with color coded Doppler ultrasound prior to temporalis biopsy. The investigation included the temporal artery on both sides and documentation was performed with color prints of the longitudinal orientation of both temporal arteries. All patients had an unilateral biopsy of the temporal artery. RESULTS: 6/20 patients had histologically confirmed temporal arteritis. All patients showed a paravasal zone of lower echogenicity (halo-sign) along the temporal artery. 12/14 patients without temporal arteritis showed no halo-sign. However, a halo-sign was found in 2/14 patients without temporal arteritis which could not be distinguished from the halo-sign observed in patients with temporal arteritis. CONCLUSIONS: A halo-sign could be detected in the majority of patients with arteritis temporalis in concordance with the recent published findings of Schmidt et al. However, a definite specificity of this halo-sign must be rejected.

Aged↗
PubMed1998

An experimental high-resolution MR coil for the imaging of pathological findings in the post mortem brain stem.

PURPOSE: The purpose of this study was to evaluate the potential of an experimental coil using a whole-body MR unit to delineate pathological changes within formalin-fixed human brain stems. MATERIAL, METHODS, AND RESULTS: The MR images of 9 brain stems were compared with gross anatomy and corresponding histological sections. The resolution of the images was high enough to depict areas of clinically relevant pathological alterations.

Brain Diseases↗
PubMed1998

Evaluation of segmentation algorithms for generation of patient models in radiofrequency hyperthermia.

Time-efficient and easy-to-use segmentation algorithms (contour generation) are a precondition for various applications in radiation oncology, especially for planning purposes in hyperthermia. We have developed the three following algorithms for contour generation and implemented them in an editor of the HyperPlan hyperthermia planning system. Firstly, a manual contour input with numerous correction and editing options. Secondly, a volume growing algorithm with adjustable threshold range and minimal region size. Thirdly, a watershed transformation in two and three dimensions. In addition, the region input function of the Helax commercial radiation therapy planning system was available for comparison. All four approaches were applied under routine conditions to two-dimensional computed tomographic slices of the superior thoracic aperture, mid-chest, upper abdomen, mid-abdomen, pelvis and thigh; they were also applied to a 3D CT sequence of 72 slices using the three-dimensional extension of the algorithms. Time to generate the contours and their quality with respect to a reference model were determined. Manual input for a complete patient model required approximately 5 to 6 h for 72 CT slices (4.5 min/slice). If slight irregularities at object boundaries are accepted, this time can be reduced to 3.5 min/slice using the volume growing algorithm. However, generating a tetrahedron mesh from such a contour sequence for hyperthermia planning (the basis for finite-element algorithms) requires a significant amount of postediting. With the watershed algorithm extended to three dimensions, processing time can be further reduced to 3 min/slice while achieving satisfactory contour quality. Therefore, this method is currently regarded as offering some potential for efficient automated model generation in hyperthermia. In summary, the 3D volume growing algorithm and watershed transformation are both suitable for segmentation of even low-contrast objects. However, they are not always superior to user-friendly manual programs for contour generation. When the volume growing algorithm is used, the contours have to be postprocessed with suitable filters. The watershed transformation has a large potential if appropriately developed to 3D sequences and 3D interaction features. After all, the practicality and feasibility of every segmentation method critically depend on various details of the user software as pointed out in this article.

Algorithms↗
PubMed1998

Preoperative hyperthermia combined with radiochemotherapy in locally advanced rectal cancer: a phase II clinical trial.

OBJECTIVE: A prospective phase II study was performed to determine the feasibility and efficacy in terms of response rate, resectability, and morbidity in patients with locally advanced rectal cancer who received preoperative regional hyperthermia combined with radiochemotherapy (HRCT). SUMMARY BACKGROUND DATA: Recent studies suggest that preoperative radiochemotherapy in locally advanced rectal cancer can induce downstaging, but after resection the incidence of local recurrences remains high. Hyperthermia (HT) may add tumoricidal effects and improve the efficacy of radiochemotherapy in a trimodal approach. PATIENTS AND METHODS: Thirty-seven patients with histologically proven rectal cancer and T3 or T4 lesions, as determined by endorectal ultrasound and computed tomography, entered the trial. 5-Fluorouracil (300-350 mg/m2) and leucovorin (50 mg) were administered on days 1 to 5 and 22 to 26. Regional HT using the SIGMA 60 applicator (BSD-2000) was given once a week before radiotherapy (45 Gy with 1.8-Gy fractions for 5 weeks). Surgery followed 4 to 6 weeks after completion of HRCT. RESULTS: Preoperative treatment was generally well tolerated, with 16% of patients developing grade III toxicity. No grade IV complications were observed. The overall resectability rate was 32 of 36 patients (89%), and 31 resection specimens had negative margins (R0). One patient refused surgery. In 5 patients (14%), the histopathologic report confirmed no evidence of residual tumor (pCR). A partial remission (PR) was observed in 17 patients (46%). The survival rate after 38 months was 86%. In none of the patients was local recurrence detected after R0(L), but five patients developed distant metastases. CONCLUSION: Preoperative HRCT is feasible and effective and may contribute to locoregional tumor control of advanced rectal cancer, which is to be proven in an ongoing phase III trial.

Adenocarcinoma↗
PubMed1998

Biphasic spiral computed tomography versus digital subtraction angiography for evaluation of arterial thrombosis after orthotopic liver transplantation.

RATIONALE AND OBJECTIVES: The authors characterize the spiral computed tomographic (CT) findings in patients with hepatic arterial thrombosis after orthotopic liver transplantation (OLT). METHODS: In nine with and 15 patients without hepatic artery thrombosis (HAT) after OLT, unenhanced and contrast-enhanced biphasic spiral CT was performed during arterial and venous phases, and evaluated by consensus of two blinded readers. Evaluation included signs of parenchymal and vascular changes in the liver. Findings subsequently were correlated with those of digital subtraction angiography (DSA). RESULTS: Among all patients, eight had complete occlusion of the proximal hepatic artery and one patient had partial thrombosis, as revealed by conventional DSA. Characteristic CT findings of HAT included irregularly shaped confluent hypoattenuating liver areas (n = 8), seen both before and after administration of contrast material. Necrotic lesions and changes consistent with ischemic type of biliary lesion were documented in six patients. Biphasic CT allowed detection of HAT in eight patients. Because of inadequate contrast enhancement during the arterial phase, thrombosed intrahepatic arteries were not adequately diagnosed in one patient. Overall CT sensitivity to detect HAT was 89%, specificity was 100%. CONCLUSIONS: Characteristic biphasic spiral CT findings in hepatic artery thrombosis contribute to early detection of arterial thrombosis after OLT and are helpful for planning more invasive diagnostic approaches.

Adolescent↗
PubMed1998

Assessment of vascularity in reactive lymph nodes by means of D-galactose contrast-enhanced Doppler sonography.

RATIONALE AND OBJECTIVES: A prospective study in signal-enhanced Doppler sonography of lymph nodes that were assumed pretherapeutically to be benign was performed to investigate characteristic sonomorphologic features and vascularity of reactively enlarged lymph nodes. METHODS: Thirty-four patients with enlarged superficial lymph nodes of the neck were examined first by B-scan sonography then by Doppler sonography before and after administration of an ultrasound signal-enhancing agent. In B-scan sonography, lymph nodes were classified into three groups according to their sonomorphologic features: (1) homogeneous parenchyma, (2) a centrally located echogenoic line, and (3) a echogenoic "hilus reflex." In conventional and contrast-enhanced Doppler sonography, peak flow rate, pulsatility index, and resistive index were assessed. Sonomorphologic criteria were compared with histologic findings. RESULTS: Reactively enlarged lymph nodes showed characteristic sonomorphologic patterns correlating to their histologic features. Echogenicity of the hilus corresponded to fibrosis (centrally located echogenoic line in 13 nodes; 38.2%) or fatty involution of the hili (echogenoic hilus reflex in 15 nodes; 44.1%). Administration of the galactose-based ultrasound contrast enhancer facilitated the assessment of hilar vessels, which projected to the echogenoic hili, respectively, actually additionally visualized a hilar vascularity in 10 of the 34 lymph nodes compared with conventional Doppler. Measured Doppler indices gave not a significant clue for identifying reactive lymph nodes or for differential diagnosis. CONCLUSIONS: Qualitative sonomorphologic assessment of characteristic sonomorphologic features of reactive lymph nodes may serve as a valuable tool for examining reactively enlarged lymph nodes. Administration of an ultrasound echo enhancer allows the assessment of a characteristic nodal vascularity in reactive lymph nodes and were superior to conventional B-mode and conventional Doppler sonography.

Adult↗
PubMed1998

Biphasic spiral computed tomography for detection of hepatocellular carcinoma before resection or orthotopic liver transplantation.

RATIONALE AND OBJECTIVES: The authors correlate computed tomography (CT) findings in biphasic spiral technique with histopathology in patients with hepatocellular carcinoma (HCC) who had undergone liver resection (LR) or orthotopic liver transplantation (OLT). METHODS: Preoperative biphasic spiral CT findings in 33 consecutive patients (23 men, 10 women, aged 43-74 years; LR group: n = 17; OLT group; n = 16) with liver cirrhosis and HCC were reviewed retrospectively by consensus of two radiologists and correlated with pathology from liver specimens. RESULTS: Of the 16 patients in the OLT group with 1 to 5 confirmed HCC lesions (total lesions: 29; mean lesion diameter: 2 cm; range: 0.6-5.0 cm), CT before OLT depicted 22 lesions in 15 patients (sensitivity for lesions with a diameter of 0.5-1.0 cm, 20%; for lesions 1.1-2.0 cm, 82%; and for lesions 2.1-3.0 cm and > 3.0 cm, 86% and 100%, respectively). Among the 17 patients in the LR group (total lesions: 21; mean lesion diameter: 5.4 cm; range: 1.0-11.0 cm), CT detected 18 lesions. Lesion-by-lesion sensitivity, as correlated with pathology, was calculated at 76% and 86% in the OLT and LR groups, respectively (overall sensitivity, 80%). The diameter of CT detected lesions, compared with liver specimens, corresponded in 90% of lesions (maximum deviation, 15%). Characteristic CT findings of HCC included unenhanced hypoattenuating focal liver lesions (32 lesions), with hyperattenuation (38 lesions) in the arterial phase of contrast material administration. CONCLUSIONS: Biphasic spiral CT for preoperative HCC detection correlated with pathology in 80%, thus proving this technique to represent a sensitive imaging modality for pretherapeutic evaluation of HCC.

Adult↗
PubMed1998

Differences in predominant enhancement mechanisms of superparamagnetic iron oxide and ultrasmall superparamagnetic iron oxide for contrast-enhanced portal magnetic resonance angiography. Preliminary results of an animal study original investigation.

RATIONALE AND OBJECTIVES: To determine the effect of particle size of superparamagnetic iron oxide (SPIO) contrast agents on magnetic resonance angiography of the portal venous system. METHODS: We studied eight beagle dogs by a T1-weighted 3D turbo-gradient echo magnetic resonance (MR) angiography sequence (TE 4 milliseconds, TR 11 milliseconds, flip angle 25 degrees, coronal imaging plane) before and after administration of either Resovist (SHU555A), a superparamagnetic iron oxide contrast agent with a mean particle size of 60 nm and a relaxivity ratio R2/R1 of approximately 7, or a new ultrasmall superparamagnetic iron oxide (USPIO) contrast agent with a mean particle size of approximately 20 nm and a R2/R1 ratio of approximately 2. Images were acquired on a 1.5-T MR body scanner. Both agents were injected as a peripheral bolus of 40 mumol Fe/kg body weight. Repeated scans were acquired before, immediately after, and 10, 20, 30, and 40 minutes after administration of the agent. RESULTS: After administration of Resovist, portal venous signal increased to 237% of control immediately after injection, while hepatic parenchymal signal intensity decreased to 86% of control. The maximal CNR increase to 177% was achieved immediately after injection of the agent. After USPIO, portal venous signal increased to 401% of the precontrast value immediately after injection, while hepatic parenchymal signal intensity also increased to 131% of control at this time. Hepatic signal then decreased progressively to 49% of control after 40 minutes. The maximal CNR increase to 326% was achieved 10 minutes after injection of the agent. CONCLUSIONS: It is concluded that superparamagnetic iron oxide particles of different sizes have different R2/R1 ratios and, consequently, different mechanisms of contrast improvement in T1-weighted portal MR angiograms.

Animals↗
PubMed1998

Initially unresectable hilar cholangiocarcinoma: hepatic regeneration after transarterial embolization.

PURPOSE: To assess with volumetric computed tomography (CT) the pattern and extent of hepatic regeneration induced with transarterial embolization of initially unresectable hilar cholangiocarcinoma (Klatskin tumor). MATERIALS AND METHODS: In this prospective study, 13 patients (four men, nine women) with hilar cholangiocarcinoma, aged 43-74 years (mean +/- 1 standard deviation, 59.9 years +/- 9.6), underwent preoperative embolization of the right hepatic lobe. Embolization was performed transarterially by using four to 15 embolization coils. Volumetric measurements of the entire liver, left hepatic lobe, and spleen were performed with contrast material-enhanced and unenhanced helical CT before and after embolization in all patients. RESULTS: After right lobe embolization, volumetric helical CT measurements revealed a 2%-33% decrease (mean, 10%) in the volume of the affected right hepatic lobe, an 11%-68% increase (mean, 37%) in the volume of left hepatic lobe parenchyma, and variations in splenic volume of -5% to +28% (mean, +11%). Nine patients underwent extended hepatectomy 27-75 days (mean, 44 days) after embolization. No patient had severe complications due to embolization. CONCLUSION: In patients with an initially unresectable bilateral Klatskin tumor, right lobar arterial coil embolization results in enlargement of the left hepatic lobe (as verified with volumetric helical CT), thus allowing right hemihepatectomy.

Adult↗
PubMed1998

Internally cooled power laser for MR-guided interstitial laser-induced thermotherapy of liver lesions: initial clinical results.

PURPOSE: To evaluate experimentally and clinically an internally cooled power laser system for percutaneous treatment of liver metastases, with magnetic resonance (MR) imaging guidance, to increase the volume of coagulative necrosis with single laser beam applications. MATERIALS AND METHODS: The power laser system consisted of standard cannulation paraphernalia and a specially designed 7-F protective catheter for cooling the laser tip during treatment to avoid carbonization. A microdome laser beam applicator with a laser tip diameter of 0.95 mm kept the entire device as small as possible. After the unit was tested in 40 porcine livers, 532 laser beam applications (mean power, 27.5 W [range, 22.1-30.0 W]; mean application time, 19.8 minutes [range, 14-30 minutes]) were performed with MR guidance in 127 patients with 318 liver metastases. The safety of the procedure and the volume of induced necrosis were evaluated. RESULTS: In vitro, cuboid areas of coagulative necrosis with a mean greatest diameter of 4.3 cm +/- 0.5 (SD) were demonstrated after single applications. In vivo, MR thermometry allowed accurate demarcation of changes induced by heat, with a mean diameter of necrosis of 3.3 cm +/- 1.4. No carbonization or vaporization of tissue or damage of equipment occurred during treatment. CONCLUSION: This power laser system can increase the volume of laser-induced necrosis in liver metastases with a single application, thereby simplifying and accelerating the treatment of larger lesions.

Animals↗
PubMed1998

Magnetic resonance (MR) imaging of the chest: state-of-the-art.

To date, magnetic resonance (MR) is established as an imaging modality in the diagnosis of chest diseases. Because of its excellent distinction of vessels and soft tissue, MR can be performed as the primary imaging procedure before computed tomography in patients with suspected vascular lesions, mediastinal masses, hilar lesions, and pathological changes of the pleura and the chest wall. In these cases, MR is able to provide all the necessary diagnostic information. In other patients, a limited number of MR images may be helpful in cases of equivocal or confusing CT or clinical findings. More detailed information can be obtained, using surface coils or special imaging sequences, i.e. high resolution MR images of the pleura or angiographic images of mediastinal and pulmonary vasculature. From a clinical viewpoint, the most important task for thoracic magnetic resonance nowadays is the pretherapeutic evaluation of intrathoracic masses, the differential diagnosis of benign versus malignant lesions, and the accurate documentation of tumour extent in malignancies including three-dimensional-display to improve surgical or radiation planning. Future directions in thoracic magnetic resonance will be predominantly influenced by postprocessing approaches, specialized imaging techniques, and magnetic resonance-guided interventional applications.

Heart Diseases↗
PubMed1998

Differential diagnosis of lymph node lesions: a semiquantitative approach with colour Doppler ultrasound.

The aim of this study was to evaluate reactively enlarged cervical lymph nodes and nodal metastases in patients with squamous cell carcinoma, as well as nodes involved by malignant lymphoma, by means of colour Doppler ultrasound (CDUS) and to describe perfusion sites for each nodal group in order to determine if typical flow patterns exist for nodes with different pathology. In a prospective study, 63 untreated patients with palpable cervical lymph node enlargement (n = 208) underwent examination with CDUS. The sites of perfusion were subdivided into three groups: central, peripheral and hilar perfusion. The intensity of perfusion was subjectively quantified in a semiquantitative scale from 0 (no perfusion) to III (high perfusion). Finally, the overall perfused area of the lymph nodes was measured and the percentage of perfused nodal area was calculated. CDUS showed perfusion in 178 of 208 lymph nodes. Histological examination showed 49 reactively enlarged lymph nodes, 82 containing metastases and 47 with lymphoma. Reactively enlarged lymph nodes showed characteristically intense hilar perfusion (91.8%), whereas nodal metastases had mainly peripherally located flow (84.1%) of intensity grades I-III. Lymph nodes invaded by malignant lymphoma were highly perfused, showing colour signals in the centre as well as in the nodal periphery (78.7%). In conclusion, perfusional patterns may provide useful additional information in the differential diagnosis of cervical lymphadenopathy.

Adolescent↗
PubMed1998

Colony-stimulating factor-1 stimulates the fusion process in osteoclasts.

Colony-stimulating factor-1 (CSF-1), also called macrophage colony-stimulating factor, is required for growth, differentiation, activation, and survival of cells of the mononuclear phagocytic system. This cytokine has been shown to be essential for osteoclast development as well as for inducing both proliferation and differentiation of osteoclast progenitors. It also sustains survival of mature osteoclasts and stimulates spreading and migration of these cells. In the present in vitro study, the formation of large tartrate-resistant acid phosphatase (TRAP)-positive cells with a high number of nuclei was observed when osteoclasts isolated from rat long bones were incubated with CSF-1. These large cells, cultured on plastic, bind calcitonin and form F-actin along the edges of the cells. Fusion to such large TRAP-positive multinucleated cells in the presence of CSF-1 and the formation of pits were also observed on dentine slices. Quantitative data obtained from cultures on plastic demonstrated that the number of osteoclasts slightly increased in the course of 72 h in the presence of 250 pM CSF-1, whereas it decreased rapidly after 24 h in the absence of CSF-1, which confirms that this cytokine is required for the survival of osteoclasts. The number of nuclei per osteoclast was maximal after 16 h of incubation with CSF-1, namely twice the value found in the absence of CSF-1. The maximal effect of the cytokine on the fusion process was observed at a concentration of 250 pM. A calculation of the medians of the average frequency of nuclei distribution per osteoclast resulted in four nuclei per osteoclast in the absence and six in the presence of CSF-1. Genistein and herbimycin A, inhibitors of tyrosine kinases, inhibited the fusion induced by CSF-1. The data suggest that CSF-1 induces osteoclast fusion and that tyrosine kinase(s) are involved in this process. The fusion process may continue throughout the entire life of an osteoclast.

Animals↗