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Roland Felix

Publications and source records attributed to Roland Felix.

At least 73 records · Page 4Linked to original sources
PubMed2003

Clinical results of CsI-detector-based dual-exposure dual energy in chest radiography.

The aim of this study was to compare the sensitivity and specificity of digital chest radiography alone with digital chest radiography combined with dual-energy chest radiography in the detection of small non-calcified pulmonary nodules. Standard and dual-energy radiographs were obtained with a flat-panel digital chest system. Four radiologists reviewed digital posteroanterior chest radiographs in random order either alone or in conjunction with dual-energy soft tissue and bone images. Twenty patients with a total of 59 pulmonary nodules (median 0.5 cm, range 0.3-2.5 cm) confirmed by computed tomography (HU < or =100) were included. A level of confidence for each diagnosis was documented using a rating scale of 1-5. Brunner and Langer's test was performed for statistical analysis. Subgroup analysis was performed for nodules greater than 1 cm, 1-0.5 cm, and <0.5 cm. For posteroanterior chest radiography, sensitivity was 33%, positive predictive value 83%, specificity 81%, and negative predictive value 30%. Review in conjunction with dual-energy images resulted in a sensitivity of 42%, positive predictive value 88%, specificity 85%, and negative predictive value 34%. The increase of nodule detection overall as well as for different size categories was significant (p<0.05). The increase of the confidence level rating was also significant (p<0.001). Dual energy added to standard posteroanterior chest radiography significantly improves the sensitivity, specificity, and confidence in detection of small non-calcified pulmonary nodules.

Humans↗
PubMed2003

Detection of pulmonary nodules by multislice computed tomography: improved detection rate with reduced slice thickness.

The purpose of this study was to find out if the use of 1.25-mm collimated thin-slice technique helps to detect more small pulmonary lung nodules than the use of 5 mm. A total of 100 patient examinations that allowed a reconstruction of 1.25-mm slice thickness in addition to the standard of 5-mm slices were included in a prospective study. Acquisition technique included four rows of 1-mm slices. Two sets of contiguous images were reconstructed and compared with 1.25- and 5-mm slice thickness, respectively. Two radiologists performed a film-based analysis of the images. The size and the confidence of the seen nodules were reported. We did not perform a histological verification, according to the normal clinical procedure, although it would be optimal regarding research. Statistical analysis was performed by using longitudinal analysis described by Brunner and Langer. In addition, sensitivity, specificity, negative predictive value and positive predictive value were calculated for each reader using the 1.25-mm sections as the gold standard. As an index for concordance the kappa value was used. A value of p<0.05 was regarded as significant. In 37 patients pulmonary nodules were detected. Twenty-four patients showed more than one nodule; among these, 7 patients had disseminated disease and were excluded from the study. Pulmonary nodules larger than 10 mm in size were equally well depicted with both modalities, whereas lesions smaller than 5 mm in size were significantly better depicted with 1.25 mm (p<0.05). Using 1.25 mm as the gold standard, sensitivity for 5-mm reconstruction interval was 88 and 86% for observers A and B, respectively. No false-positive results were reported for 5-mm sections. Interobserver agreement for nodule detection determined for 1.25-mm reconstruction intervals showed a k value of 0.753, indicating a good agreement, and 0.562 for 5-mm reconstruction intervals, indicating a moderate agreement. Brunner and Langer analysis showed significant differences for slice thickness and no significant difference between the observers. Reduced slice thickness demonstrated an improvement of small nodule detection, confidence levels, and interobserver agreement. Application of thin-slice multidetector-row CT may raise the sensitivity for lung nodule detection, although the higher detection rate of smaller nodules has to be evaluated from a clinical perspective and remains problematic about how the detection of small nodules will effect patient outcome.

Adult↗
PubMed2003

Clinical use of the hyperthermia treatment planning system HyperPlan to predict effectiveness and toxicity.

PURPOSE: The main aim is to prove the clinical practicability of the hyperthermia treatment planning system HyperPlan on a beta-test level. Data and observations obtained from clinical hyperthermia are compared with the numeric methods FE (finite element) and FDTD (finite difference time domain), respectively. METHODS AND MATERIALS: The planning system HyperPlan is built on top of the modular, object-oriented platform for visualization and model generation AMIRA. This system already contains powerful algorithms for image processing, geometric modeling, and three-dimensional graphics display. A number of hyperthermia-specific modules are provided, enabling the creation of three-dimensional tetrahedral patient models suitable for treatment planning. Two numeric methods, FE and FDTD, are implemented in HyperPlan for solving Maxwell's equations. Both methods base their calculations on segmented (contour based) CT or MR image data. A tetrahedral grid is generated from the segmented tissue boundaries, consisting of approximately 80,000 tetrahedrons per patient. The FE method necessitates, primarily, this tetrahedral grid for the calculation of the E-field. The FDTD method, on the other hand, calculates the E-field on a cubical grid, but also requires a tetrahedral grid for correction at electrical interfaces. In both methods, temperature distributions are calculated on the tetrahedral grid by solving the bioheat transfer equation with the FE method. Segmentation, grid generation, E-field, and temperature calculation can be carried out in clinical practice at an acceptable time expenditure of about 1-2 days. RESULTS: All 30 patients we analyzed with cervical, rectal, and prostate carcinoma exhibit a good correlation between the model calculations and the attained clinical data regarding acute toxicity (hot spots), prediction of easy-to-heat or difficult-to-heat patients, and the dependency on various other individual parameters. We could show sufficient agreement between the calculations and measurements for power density (specific absorption rate) within the range of assessed precision. Tumor temperatures can only be estimated, because of the rather variable perfusion conditions. The results of the FE and FDTD methods are comparable, although slight differences exist resulting from the differences in the underlying models. There are also statistically provable differences among the tumor entities regarding the attained specific absorption rate, temperatures, and volume loads in normal tissue. However, gross fluctuations exist from patient to patient. CONCLUSION: The hyperthermia planning system HyperPlan could be validated for a number of the 30 patients. Further improvements in the implemented models, FE and FDTD, are required. Even at its present state of development, hyperthermia planning for regional hyperthermia delivers valuable information, not only for clinical practice, but also for further technologic improvements.

Algorithms↗
PubMed2003

Laser-induced thermotherapy (LITT) of liver metastases: MR-guided percutaneous insertion of an MRI-compatible irrigated microcatheter system using a closed high-field unit.

PURPOSE: To evaluate the efficacy and safety of a new MRI-compatible irrigated laser microcatheter system for thermal ablation of liver metastases. MATERIAL AND METHODS: The new microcatheter system consists of a titanium needle with a diameter of 1.5 mm and a surrounding Teflon catheter with an outer diameter of 1.8 mm (5.5 F). In vitro laser-induced coagulation of bovine liver tissue was performed to determine the optimal perfusion rate of cooling saline flow, maximum laser energy, and ablation time. Laser-induced thermotherapy using the new microcatheter system, an Nd:YAG laser (Dornier), and a flexible laser light guide (Somatex GmbH, Berlin, Germany) was performed in 28 patients with liver metastases. Percutaneous insertion and positioning of multiple microcatheters in the lesion and monitoring of therapy was performed with a closed high-field MRI scanner using T1-weighted gradient-echo sequences during breath-hold. RESULTS: A perfusion rate of 0.75 mL/minute, a laser energy of 15 W, and an ablation time of 20 minutes were found suitable to achieve safe and sufficient ablation of metastatic tissue. The mean volume of induced coagulation in vitro was 23.9 mL. Ablation of liver metastases in patients was technically and clinically successful. CONCLUSION: The new microcatheter system allows for both catheter placement and monitoring of therapy using a single imaging modality. This shortens the procedure and enables more precise puncture and therapy of liver metastases. Due to the miniaturized design of the catheter and the real-time monitoring, the procedure is minimally invasive and very well tolerated by patients. This new technique seems to be a safe and feasible alternative in treating liver metastases.

Aged↗
PubMed2003

Prospective comparison of transcutaneous 3-dimensional US cholangiography, magnetic resonance cholangiography, and direct cholangiography in the evaluation of malignant biliary obstruction.

BACKGROUND: The purpose of this study was to investigate the ability of transcutaneous three-dimensional US cholangiography to depict the biliary tree in malignant obstruction, compared with that of MRCP and direct cholangiography. METHODS: Three-dimensional US and MRCP and direct cholangiography were performed in 40 patients with suspected malignant biliary obstruction. Diagnostic quality of the images, presence, level, and cause of ductal obstruction were assessed in a prospective, blinded fashion. The results were correlated with consensus interpretation (3 investigators), intra-operative findings, and histopathology or clinical follow-up. RESULTS: Three-dimensional US produced cholangiographic images of diagnostic quality. The appearance of these images was similar to that of MRCP or ERCP/percutaneous transhepatic cholangiography images. All modalities were highly sensitive in the detection of biliary dilatation. The accuracy of 3-dimensional US, MRCP, and ERCP/percutaneous transhepatic cholangiography in determining the level of obstruction was, respectively, 92%, 95%, and 98%. Transcutaneous 3-dimensional US and MRCP accurately identified the cause of obstruction in, respectively, 90% and 95% of cases. Direct cholangiography revealed the correct diagnosis in 95% of the patients. CONCLUSIONS: Three-dimensional US cholangiography is a new, noninvasive method with the capability to produce diagnostic cholangiograms. Three-dimensional US cholangiography may be used increasingly as an initial test to select patients who require further diagnostic evaluation by MRCP or therapeutic ERCP.

Aged↗
PubMed2003

Whole body hyperthermia induces apoptosis in subpopulations of blood lymphocytes.

Whole Body Hyperthermia (WBH) has been shown to induce alterations of lymphocyte subpopulations in peripheral blood: T-cells decrease and NK-cells increase in number in the course of this therapy. As elevated temperature induces programmed cell death in healthy lymphocytes in vitro, we intended to determine the role of lymphocyte apoptosis in WBH by measuring the rate of apoptosis in blood lymphocytes in the course of this treatment. Blood was taken from cancer patients, treated with whole body hyperthermia and chemotherapy, before, during and the day after treatment. Apoptosis rates of the whole lymphocyte population, as well as, of B-, T-, CD4 + -T-, CD8 + -T-, and Natural-Killer (NK)-cell-subpopulations were determined by staining with AnnexinV-FITC and FACS flow analysis. A significant rise of apoptosis in the whole lymphocyte population, in CD4 + -T- and in CD8 + -T-cells occurred during treatment. In contrast, an elevated rate of apoptosis in NK-cells was observed 20 hours after termination of WBH. These differences were similar when the cells were incubated at 37 degrees C for 24 hours. Our results suggest, that apoptosis is one reason for the previously described decrease of T-cells during WBH and of NK-cells after WBH, and that the hyperthermia-related apoptosis-inducing mechanism is different in T-cells and NK-cells.

Adult↗
PubMed2003

Coronary artery calcium scoring: diagnostic accuracy of different software implementations.

PURPOSE: To compare the diagnostic power of different software implementations for the quantification of coronary artery calcium. MATERIALS AND METHODS: Electron beam computed tomography was performed in 109 heart transplant recipients at the same time as catheter coronary angiography and intracoronary ultrasound. Electron beam computed tomography images were analyzed by 3 software packages marketed for the quantification of coronary calcifications using the same software settings, and the resultant calcium scores correlated with the invasive reference methods by Bland-Altman plots and analysis of the receiver operating characteristics. RESULTS: Although all scoring systems displayed close correlations upon regression analysis (r2=0.94-0.99), their ability to detect disease as per the invasive reference method varied significantly in some instances. The area under the ROC curve varied between Az=0.78 and 0.85 for the detection of coronary artery stenosis upon coronary angiography (P=0.05-0.13), and between Az=0.75 and 0.83 for the detection of accelerated intimal proliferation (P=0.03-0.18). CONCLUSIONS: Different software implementations for the quantification of coronary artery calcium load may display diagnostically relevant differences in spite of close direct correlation.

Adolescent↗
PubMed2003

Dual-energy chest radiography with a flat-panel digital detector: revealing calcified chest abnormalities.

OBJECTIVE: The aim of this study was to assess the value of dual-energy chest radiography obtained using a cesium iodide flat-panel detector in addition to standard posteroanterior chest radiography for the detection of calcified chest abnormalities. MATERIALS AND METHODS: The study included 20 patients with a total of 37 calcified chest lesions (16 pulmonary nodules, 17 mediastinal calcifications, and four pleural calcifications) as confirmed on CT. Twenty-eight locations in the chests of the same patients who were free of lesions were used as negative controls. Four radiologists reviewed posteroanterior chest radiographs in a blinded manner alone and in conjunction with dual-energy soft-tissue and bone images. We calculated sensitivity, specificity, the negative predictive value (NPV), and the positive predictive value (PPV) for lesion prediction. The Wilcoxon's and the Brunner and Langer's tests were performed for statistical analysis. RESULTS: For posteroanterior chest radiography, sensitivity was 36%, the PPV was 64%, and the NPV was 47%. When dual-energy images were added, sensitivity increased significantly to 66% (p < 0.05), the PPV to 76%, and the NPV to 62%. The specificity remained constant at 73%. Brunner and Langer's test revealed a highly significant difference between posteroanterior chest radiography and dual-energy imaging in the detection of calcified chest abnormalities (p < 0.01). CONCLUSION: Dual-energy images added to standard posteroanterior chest radiographs significantly improve the detection of calcified chest lesions.

Aged↗
PubMed2003

[Pre- and post-interventional follow-up of stent graphs with single and multi-slice spiral computerized tomography].

PURPOSE: Could contrast enhanced computed tomography replace conventional catheter angiography in the preoperative evaluation of aortic aneurysms before stentgraft implantation? Does multi slice computed tomography have advantages comparing to single slice computed tomography? METHODS: We compared 15 single slice with 13 multi slice computed tomography studies and reconstructions according to there ability to replace conventional catheter angiography in the preoperative evaluation. In the postoperative follow-up 60 single slice computed tomography studies were compared to 60 multi slice studies. RESULTS: By using appropriate reconstructions the spiral computed tomography studies could deliver all information necessary for implantation. In our study no advantage of multi slice computed tomography could be detected. In the postoperative evaluation of stentgrafts our computed tomography scan protocol could detect all relevant complications in single and multi slice computed tomography. No significant advantage of multi slice computed tomography could be detected. CONCLUSION: Contrast enhanced computed tomography is equal to conventional catheter angiography in the pre- and postoperative evaluation of stengrafts. No significant advantage of multi slice versus single slice could be detected.

Aortic Aneurysm, Abdominal↗
PubMed2002

CSF flow imaging in the management of third ventriculostomy with a reversed fast imaging with steady-state precession sequence.

The aim of this study was evaluation of a fast and slow-flow sensitive 2D steady-state free-precession sequence for its capability to prove the patency of endoscopic third ventriculostomy (TVS) in obstructive hydrocephalus, and to exclude communicating third ventricle prior to TVS. We compared gated and ungated variants of this sequence for this purpose. Twenty-three patients with obstructive hydrocephalus underwent 36 MR examinations with a 2D reversed fast imaging with steady-state precession (PSIF) sequence in a retrospectively cardiac gated (cine) and a faster but ungated version beside T1- and T2-weighted sequences in three planes. Thirteen patients were examined both before and after TVS, 4 patients solely before, and 6 patients solely after TVS. Imaging diagnoses were compared with intraoperative findings and clinical findings after TVS. Preoperative diagnosis of non-communicating third ventricle and cisterns was intraoperatively confirmed in 16 of 17 cases. Preoperative MRI was inconclusive in 1 case. Postoperative MRI revealed sufficient TVS in 16 of 19 cases and obstructed TVS in 3 of 19 cases due to several reasons. Findings at MRI were consistent in 19 of 19 cases with the clinical course and intraoperative results. The faster but ungated PSIF sequence was found to be diagnostically equivalent to the cardiac gated cine sequence. The CSF flow imaging with a 2D reversed fast imaging with steady-state precession sequence in conjunction with conventional T1- and T2-weighted images is a fast and reliable tool for pre- and postoperative functional evaluation in third ventriculostomy.

Adult↗
PubMed2002

Prospective evaluation of contrast-enhanced MRI in the depiction of peritoneal spread in primary or recurrent ovarian cancer.

The purpose of this study was to assess the accuracy of MRI in the staging of intra-abdominal tumor seeding of ovarian carcinoma. Fifty-seven patients with suspected primary or recurrent ovarian carcinoma were included in this study. All patients received laparotomy within 8 weeks after MRI. The MRI protocol included fat-saturated T1-weighted spin-echo (SE) sequences pre- and post i.v. application of gadopentetate dimeglumine. The criteria for tumor manifestation was contrast enhancement of intra-abdominal soft tissue lesions or peritoneum. The image review was performed by a blinded radiologist, a specialist in gynecological and abdominal MR imaging. Results were compared with findings during laparotomy. Sensitivity, specificity, positive and negative predictive values, and corresponding 95% confidence intervals were calculated for single intra-abdominal locations and for groups of locations defined according to surgical strategies for intra-abdominal cytoreduction. Laparotomy and histopathology confirmed 251 abdominal tumor locations. Sensitivity was high in lower pelvis locations (73-83%) except for ureter or bladder infiltration (40%). Bowel or mesentery locations displayed sensitivity values from 73 to 77%. Sensitivity was very low for pelvic lymph nodes (28%), greater omentum (38%), and lesser sac (43%). Magnetic resonance imaging based on contrast-enhanced fat-saturated T1 SE sequences improves planning of cytoreduction preceding chemotherapy in advanced primary or relapsed ovarian carcinoma.

Abdominal Neoplasms↗
PubMed2002

Preoperative evaluation of malignant liver tumors: comparison of unenhanced and SPIO (Resovist)-enhanced MR imaging with biphasic CTAP and intraoperative US.

The purpose of this study was to evaluate the diagnostic efficacy of iron-oxide-enhanced MRI vs CT during arterial portography (CTAP) and intraoperative ultrasound (IOUS) in detection of liver neoplasms. Seventeen patients with malignant focal liver lesions (liver metastases, n=7), hepatocellular carcinomas (HCC, n=9), and cholangiocellular carcinoma (CCC, n=1) underwent presurgical Resovist-enhanced MRI and CTAP. Two independent observers (A and B) assessed the blinded images of unenhanced and iron-oxide-enhanced MRI vs CTAP for the presence, number, and location of the liver lesions. These results were compared lesion by lesion and segment by segment with the results of intraoperative ultrasound ( n=17) serving as the reference standard. Eighty lesions were detected by intraoperative ultrasound in 17 patients. In comparison with IOUS (lesion-by-lesion analysis) the sensitivity was 86.8% for CTAP, 65% for combined unenhanced MR imaging, and 86.8% for combined Resovist-enhanced MRI as well as 86.8% for the combination of unenhanced and Resovist-enhanced MRI. Compared with the sensitivity of combined unenhanced MRI the sensitivity of CTAP as well as the sensitivity of combined Resovist-enhanced MRI was significantly higher (p<0.05). False-positive results were much higher in CTAP as compared with combined unenhanced and SPIO-enhanced MRI. Using the segment-by-segment analysis the specificity of combined unenhanced MRI with 100% (96.7-100%) as well as combined Resovist-enhanced MRI with 100% (96.7-100%) was significantly higher (p<0.05) in comparison with the specificity of CTAP with 91.1% (83.2-96.1%). The accuracy of combined unenhanced MRI was 100% (93.2-100%), combined Resovist-enhanced MRI 100% (93.6-100%) and of CTAP 85.2% (72.9-93.4%). In the detection of focal liver lesions iron-oxide-enhanced MR imaging is superior to unenhanced MRI and similar to CTAP.

Adult↗
PubMed2002

Role of power Doppler techniques and ultrasound contrast enhancement in the differential diagnosis of focal breast lesions.

The purpose of this article is to demonstrate the diagnostic impact of ultrasound in differentiating focal breast lesions with special regard on power Doppler and US contrast agents. The sonographic evaluation of breast lesions has become a standard procedure during the past 15 years. Especially the improvement of B-mode resolution and the use of high-frequency probes increased the diagnostic value of US. Assuming that the neoangiogenetic vascular architecture of solid breast lesions can be depicted reliably by color Doppler, many authors tried to differentiate between benignity and malignancy using Doppler criteria such as flow and morphologic aspects. Additionally, adjuvant techniques, such as harmonic imaging and new US contrast agents, are meant to be success-promising tools. Whereas the sensitivity and specificity of color Doppler have varied in different studies, prognostic prediction and treatment monitoring seem to be the future areas of application. To evaluate sufficiently flow signals of very small vessels with low flow velocity, the use of contrast-enhancing agents may be necessary. Nevertheless, an indispensable condition for successful Doppler-based assessment of the entity of breast lesions is the standardization of techniques, evaluation, analysis and weighting of the parameters.

Blood Flow Velocity↗
PubMed2002

Giant fibroma in the left ventricle of an infant: imaging findings in magnetic resonance imaging, echocardiography and angiography.

The diagnosis of a rare case of giant intraventricular fibroma in an infant by MRI in comparison with other imaging modalities, such as echocardiography and angiography, is discussed. For preoperative planning only MRI showed the myocardial infiltration. The myocardial blood supply of the tumor could be evaluated qualitatively by contrast-enhanced MRI, but the direct visualization of the distally located branches could only be assessed by coronary angiography. Magnetic resonance coronary angiography using the navigator technique failed to depict the distal part of the coronaries. The obstruction of the left ventricle outflow tract could be assessed and quantified by all imaging modalities.

Coronary Angiography↗
PubMed2002

Magnetic resonance imaging of inflammatory bowel disease: evaluation in a rabbit model.

PURPOSE: To correlate intestinal contrast enhancement and wall thickening with the degree of inflammation in an experimental model of inflammatory bowel disease. MATERIALS AND METHODS: Inflammatory bowel disease was elicited in 39 New Zealand White rabbits by rectal instillation of 2,4,6-trinitrobenzene sulphonic acid (TNBA). Magnetic resonance imaging (MRI) was used to determine bowel wall thickness and intestinal contrast enhancement after the administration of 0.1 mmol/kg of gadodiamide intravenously. MR measurements were compared with the complete histopathologic analysis. RESULTS: MR measurements of bowel wall thickness correlated well with histopathologic measurements in vitro (r = 0.85, P < 0.0001) and with histopathologic evidence of chronic inflammatory bowel disease (P < 0.02). Chronic inflammation was characterized by increased intestinal contrast enhancement (137 +/- 25%) when compared to normal bowel (86 +/- 7%, P = 0.04). CONCLUSION: Contrast-enhanced MRI accurately reflects inflammatory bowel disease in the rabbit model.

Animals↗
PubMed2002

Restaging of locally advanced carcinoma of the rectum with MR imaging after preoperative radio-chemotherapy plus regional hyperthermia.

BACKGROUND: The restaging accuracy of MR imaging in advanced primary rectal carcinoma after preoperative radiochemotherapy and regional hyperthermia was evaluated and compared with the histopathologically verified degree of tumor remission after a course of radio-chemo-thermotherapy. PATIENTS AND METHODS: 35 patients with primary rectal carcinoma (uT3/uT4) underwent MRI using a surface coil 4-6 weeks after radiochemotherapy (n = 35), regional hyperthermia (n = 23), and before curative surgery. We defined as gold standard for the remission status the comparison of pretherapeutic endosonography with the histopathology of the resected specimen. RESULTS: T category was correctly restaged after preoperative treatment in only 19 (54%) of 35 patients. Nine of 20 responders were overstaged and seven of 15 non-responders were understaged. Concurrently, the N category was correctly restaged in 19 (54%) of 35 patients (twelve responders and seven non-responders). Overstaging occurred in four responders and two non-responders, understaging occurred in four responders and six non-responders. CONCLUSIONS: MRI proved independent of the response status as not suitable to restage locally advanced rectal carcinoma after preoperative radiochemotherapy despite optimized imaging technique and spatial resolution. Basically, imaging the morphology of a tumor cannot clearly differentiate between vital and devitalized tissue after a treatment. Functional imaging such as PET (positron emission tomography) appears more feasible for restaging after radio-chemo-thermotherapy.

Adult↗
PubMed2002

Tumour of the diaphragm mimicking liver lesion.

Tumours of the diaphragm bordering the liver may impose diagnostic difficulties. We report the case of a 46-year-old patient diagnosed with a tumour of the liver based on ultrasound and CT. MRI of the liver depicted a tumour growing from the chest wall towards the liver. Surgery revealed the rare entity of a malignant fibrous histiocytoma of the diaphragm.

Abdominal Abscess↗