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Biomedical subjects

Roland Felix

Publications and source records attributed to Roland Felix.

89 records · Page 5Linked to original sources
PubMed2002

The cellular and molecular basis of hyperthermia.

In oncology, the term 'hyperthermia' refers to the treatment of malignant diseases by administering heat in various ways. Hyperthermia is usually applied as an adjunct to an already established treatment modality (especially radiotherapy and chemotherapy), where tumor temperatures in the range of 40-43 degrees C are aspired. In several clinical phase-III trials, an improvement of both local control and survival rates have been demonstrated by adding local/regional hyperthermia to radiotherapy in patients with locally advanced or recurrent superficial and pelvic tumors. In addition, interstitial hyperthermia, hyperthermic chemoperfusion, and whole-body hyperthermia (WBH) are under clinical investigation, and some positive comparative trials have already been completed. In parallel to clinical research, several aspects of heat action have been examined in numerous pre-clinical studies since the 1970s. However, an unequivocal identification of the mechanisms leading to favorable clinical results of hyperthermia have not yet been identified for various reasons. This manuscript deals with discussions concerning the direct cytotoxic effect of heat, heat-induced alterations of the tumor microenvironment, synergism of heat in conjunction with radiation and drugs, as well as, the presumed cellular effects of hyperthermia including the expression of heat-shock proteins (HSP), induction and regulation of apoptosis, signal transduction, and modulation of drug resistance by hyperthermia.

Cell Death↗
PubMed2002

Flat panel digital radiography compared with storage phosphor computed radiography: assessment of dose versus image quality in phantom studies.

RATIONALE AND OBJECTIVE: To assess and quantify the dose reduction by use of a CsI-flat panel digital radiography (DR)-system compared with digital computed radiography (CR). MATERIALS AND METHODS: A TCDD-test using the CDRAD-phantom was performed at mAs-values of 5, 4, 2.5, 2, 1, and 0.5 mAs for both digital systems. Entrance surface doses were recorded for all images. Images were presented to four independent observers. For quantitative comparison the image quality figure (IQF) was calculated. Statistical analysis was performed using the Pearson correlation and the Wilcoxon test. A ROC analysis was performed using the TRG-phantom. Settings of 4, 2.5, 2 mAs for both systems were used. In addition, 1 and 0.5 mAs were used for the DR system only. Statistical significance was evaluated using Student test. RESULTS: The DR system provided equivalent results compared with CR with respect to high frequency information and superior results with respect to low contrast details. Compared with computed radiography, the flat panel detector demonstrated significantly lower IQFs, ensuring a better image quality with respect to contrast and detail detectability. IQFs for DR and CR were equal at a surface dose reduction of 87% for DR. ROC analysis revealed significantly higher values under the curve for DR up to a surface dose reduction of 70%. CONCLUSIONS: Image quality of DR proved to be far superior to CR in particular for low contrast details. The image quality of CR is similar to that of DR only at high dose levels.

Phantoms, Imaging↗
PubMed2002

Prospective evaluation of pancreatic tumors: accuracy of MR imaging with MR cholangiopancreatography and MR angiography.

PURPOSE: To prospectively assess accuracy of magnetic resonance (MR) imaging, MR cholangiopancreatography (MRCP), and MR angiography in patients suspected of having pancreatic tumors. MATERIALS AND METHODS: Sixty-six patients suspected of having pancreatic tumors underwent MR imaging (unenhanced and contrast material-enhanced MR, MRCP, and contrast-enhanced MR angiography). Two blinded readers prospectively analyzed the images by consensus, and results were correlated with surgery, biopsy, or follow-up findings. Results were tabulated in two-by-two tables. RESULTS: MR assessment of pancreatic lesion status (differentiation of benign vs malignant) resulted in 60 correct diagnoses (accuracy, 91%), and six (10%) false diagnoses. Among histologically proved malignant tumors, MR imaging yielded correct diagnoses in 42 of 44 patients (sensitivity, 95%; 95% CI: 85%, 99%), whereas 18 of 22 patients with benign findings were classified correctly. At MR imaging, findings in four patients with chronic pancreatitis were wrongly categorized as malignant tumors (specificity, 82%; 95% CI: 60%, 95%), and in one patient, a distal common bile duct carcinoma was not detected. In no patient with pancreatic adenocarcinoma was this tumor misdiagnosed as benign. In patients with malignant tumors who underwent resection, local-regional tumor growth and vascular infiltration were accurately classified in 89% and 94%, respectively. MR imaging depicted histologically proved synchronous hepatic metastases in 82%. The positive and negative predictive values for cancer nonresectability were 90% and 83%, respectively, and the accuracy, sensitivity, and specificity were 85%, 69%, and 95%, respectively. CONCLUSION: Unenhanced and contrast-enhanced MR imaging with MRCP and MR angiography offers potential as a noninvasive tool for assessment of patients suspected of having pancreatic tumors.

Adult↗
PubMed2002

Bronchiolitis obliterans syndrome in lung transplant recipients: use of spirometrically gated CT.

PURPOSE: To assess the potential use of spirometrically gated lung computed tomographic (CT) findings in the diagnosis of bronchiolitis obliterans syndrome after lung transplantation. MATERIALS AND METHODS: Forty-nine lung transplant recipients were examined at least 8 months after surgery with spirometrically gated thin-section CT of the lung. In addition to visual signs of small-airway disease at CT, mean lung attenuation and the SD were numerically determined and compared with the results of lung function testing at the time of the CT examination and 1 year later by using factorial analysis of variance. RESULTS: Mean lung attenuation was significantly lower in patients who developed bronchiolitis obliterans syndrome within 1 year after the CT study (-837 HU +/- 3) than in patients with persistent normal lung function (-812 HU +/- 3, P <.001). With an optimal threshold, sensitivity was 69%, specificity was 71%, and accuracy was 84%. Visual analysis did not significantly contribute to the prognostic power of CT. CONCLUSION: Spirometrically gated CT measurements of lung attenuation can be used to predict the onset of bronchiolitis obliterans syndrome after lung transplantation.

Adult↗
PubMed2002

Percutaneous transluminal laser angioplasty versus balloon dilation for treatment of popliteal artery occlusions.

PURPOSE: To compare the immediate results, complication rates, and long-term outcomes of percutaneous transluminal laser angioplasty (PTLA) versus balloon dilation alone in the treatment of popliteal artery occlusions. METHODS: In a prospective nonrandomized study conducted between December 1994 and June 2000, 215 symptomatic patients with unilateral popliteal occlusions were treated with either dilation alone (88 patients: 52 men; mean age 62 years, range 48-83) or PTLA (127 patients: 70 men; mean age 64 years, range 49-86) using a 308-nm excimer laser followed by dilation. The average occlusion length was 10.4 cm (range 3-14). RESULTS: PTLA was successful in recanalizing 105 (82.7%) arteries, while the recanalization rate for dilation alone was only 70.4% (62/88; p=0.045). After a mean follow-up of 36 months (range 6-52), the primary and secondary patency rates were 21.7% and 50.8%, respectively, in patients with PTLA and 16.3% and 35.2% in the angioplasty group (p=0.762). The complication rates associated with both techniques were similar. CONCLUSIONS: Although initial recanalization may be better with PTLA, it does not appear to add any long-term benefit over balloon dilation alone.

Aged↗
PubMed2002

[Quantitative determination of coronary vascular calcinosis (coronary calcium score) with double-helical CT].

Coronary heart disease is a common disease, with the typical characteristic of coronary sclerosis, an abnormal calcification of the heart's blood vessels. The amount of coronary calcification is in direct correlation to the extent of coronary heart disease. With the double-detector-helical-CT it is possible to detect and quantify these calcifications. The correlation of the "Calcium-Scoring" with the results of coronary-angiography, myocardial scintigraphy and clinical findings shows the value of this method of coronary heart diagnostic. False negative results, based on low calcified fatty stenotic plaques and false positive results, based on high calcificated plaques without significant stenosis should be taken into account.

Adult↗
PubMed2002

[BALTOMA--long-term follow-up].

PURPOSE: The purpose of this work was to describe the findings and the long term follow up of pathologically confirmed bronchus-associated lymphoid tissue lymphoma (BALTOMA) in 6 patients. METHODS: CT examinations and conventional radiological examinations were reviewed and compared to describe typical radiological findings and patterns of pulmonary manifestations. It were described the number of lesions and characteristics like presence of airspace consolidation, ground-glass attenuation, bubble-like radiolucencies, air bronchogram, bronchial dilatation, Infiltration and the long term behaviour of the manifestations. RESULTS: Lesions with a positive air bronchogram, no infiltration of extrapulmonary tissue or extrapulmonary manifestations were revealed as typical findings. Only a slow or no progression of disease was shown in most patients over a term of up to twelve years. CONCLUSIONS: The lymphoma of the bronchus-associated lymphoid tissue of the lung is a rare tumor. A positive air bronchogram, a multiplicity of disease, bilateral lesions, a fibrotic transformation of the lung tissue and no growth or only a slow groth over al long term of observation are typical radiological findings.

Adult↗
PubMed2002

[Diagnosis of tumors of the small intestine with the aid of CT contrast enema. Sellink CT technique evaluated in 63 patients].

PURPOSE: Aim of the study was to compare the visualisation of small bowel tumours particularly lymphoma of the small bowel by enteroclysma, computed tomography (CT) and computed tomography following enteroclysma. METHODS: We examined 97 examinations in 63 patients. Non Hodgkin's Lymphoma was the primary malignancy in 44 patients, metastasis of different malignancies in 8 patients, primary malignancies of the small intestine in 5 patients, mesenteric tumours in 4 patients and postoperative stricture in another 2 patients. CT following enteroclysma (CT Sellink) was performed as helical CT in 55 patients and as incremental CT in 42 patients. Examinations were evaluated by two radiologists. Evaluation criteria were small bowel distension, perceptibility of details and topographic correlation. RESULTS: Manifestations of lymphoma were found in 32 patients, infiltration of bowel wall in 12 patients. In three patients metastases of melanoma were found. In three patients the suspicion for small bowel tumours was not verified in CT Sellink. The perceptibility of details was evaluated as ameliorated in 45.5% of examinations over all. CONCLUSIONS: CT Sellink offers remarkable advantages in the diagnosis of small bowel tumours compared with enteroclysma and "conventional" computed tomography under intra-venous and oral contrast media. CT Sellink was feasible over a time of 7 years now in clinical praxis. This examination represents an optimized standard in small intestine examination.

Adult↗
PubMedDate not supplied

Osteoid osteoma: experience with laser- and radiofrequency-induced ablation.

The purpose of this study was to analyze the clinical outcome of osteoid osteoma treated by thermal ablation after drill opening. A total of 17 patients and 20 procedures were included. All patients had typical clinical features (age, pain) and a typical radiograph showing a nidus. In 5 cases, additional histological specimens were acquired. After drill opening of the osteoid osteoma nidus, 12 thermal ablations were induced by laser interstitial thermal therapy (LITT) (9F Power-Laser-Set; Somatex, Germany) and 8 ablations by radiofrequency ablation (RFA) (RITA; StarBurst, USA). Initial clinical success with pain relief has been achieved in all patients after the first ablation. Three patients had an osteoid osteoma recurrence after 3, 9, and 10 months and were successfully re-treated by thermal ablation. No major complication and one minor complication (sensible defect) were recorded. Thermal ablation is a safe and minimally invasive therapy option for osteoid osteoma. Although the groups are too small for a comparative analysis, we determined no difference between laser- and radiofrequency-induced ablation in clinical outcome after ablation.

Adolescent↗
PubMedDate not supplied

Radiation exposure to patient and staff in hepatic chemoembolization: risk estimation of cancer and deterministic effects.

The purpose of the study was to determine the risks of radiation-induced cancer and deterministic effects for the patient and staff in transarterial chemoembolization (TACE) of hepatocellular carcinoma (HCC). Sixty-five patients with HCC underwent the first cycle of TACE. Thermoluminescence dosemeters and conversion factors were used to measure surface doses and to calculate organ doses and effective dose. For the patient, the risk of fatal cancer and severe genetic defect was in the magnitude of 10(-4) and 10(-5), respectively. Five patients showed surface doses over the first lumbar vertebra exceeding 2000 mSv and 45 patients showed doses over the spine or the liver region above 500 mSv. The risk of fatal cancer and severe genetic defect for the radiologist and assistant was in the magnitude of 10(-7) to 10(-8). They could exceed the threshold for lens opacity in the case of more than 490 and 1613 TACE yearly for a period of many years, respectively. Radiation dose could lead to local transient erythema and/or local depression of hematopoiesis in many patients after TACE. For the radiologist and assistant, risk of fatal cancer and genetic defect and lens opacity might arise when they perform interventions such as TACE intensively.

Adult↗
PubMedDate not supplied

Radiological interventions for correction of central venous port catheter migrations.

The purpose of the study is to evaluate radiological-interventional central venous port catheter corrections in migrated/malpositioned catheter tips. Thirty patients with migrated/malpositioned port catheter tips were included in this retrospective analysis. To visualize the catheter patency, a contrast-enhanced port catheter series was performed, followed by transfemoral port catheter correction with various 5F angiographic catheters (pigtail, Sos Omni), goose-neck snare, or combinations thereof. One patient showed spontaneous reposition of the catheter tip. In 27 of 29 patients (93%), radiological-interventional port catheter correction was successful. In two patients, port catheter malposition correction was not possible because of the inability to catch either the catheter tip or the catheter in its course, possibly due to fibrin sheath formation with attachment of the catheter to the vessel wall. No disconnection or port catheter dysfunction was observed after correction. In migrated catheter tips, radiological-interventional port catheter correction is a minimally invasive alternative to port extraction and reimplantation. In patients with a fibrin sheath and/or thrombosis, port catheter correction is often more challenging.

Adult↗
PubMedDate not supplied

Bowel wall enhancement in magnetic resonance colonography for assessing activity in Crohn's disease.

BACKGROUND: This study focuses on the correlation of the signal intensity (SI) of the bowel wall in magnetic resonance (MR) colonography with the inflammation activity in Crohn's disease. MATERIAL AND METHODS: We performed MR colonography in 42 patients and compared the change of the SI of the bowel wall (T1-weighted/paramagnetic contrast medium) with colonoscopic findings. RESULTS: Change of the SI and colonoscopically assessed inflammatory activity are significantly correlated (r=.676, P<or=.01). CONCLUSION: The degree of the contrast enhancement of the bowel wall may be a criterion for the degree of inflammation in Crohn's disease.

Adult↗
PubMedDate not supplied

MR colonoscopy at 3.0 T: comparison with 1.5 T in vivo and a colon model.

PURPOSE: Retrospectively, magnetic resonance (MR) colonography images obtained from a colon model and in routine examinations of patients screened for polyps were compared in terms of whether, and to what degree, image quality improved at a higher field strength of 3.0 T compared to 1.5 T. MATERIALS AND METHODS: One hundred twenty-eight MR colonography images from 40 patients, of whom 20 had each been scanned at 1.5 and 3.0 T, respectively, using a four-element phased-array torso coil, were compared. At both field strengths, imaging included T1-weighted fat-suppressed spoiled gradient-echo (T1-fs-GE), T2/T1-weighted fast imaging employing steady-state acquisition (FIESTA), and T2-weighted single-shot fast spin-echo (T2-SSFSE), with breath-hold technique. Using receiver operating characteristic analysis performed by seven readers, the three types of images from the colon model and from 20 patients each at 1.5 and 3.0 T were compared. While a time window of 20 s was allowed for picture assessment in a chance-generated succession of images on a monitor, image quality was rated with a score of 1-5 (1=very good; 5=very bad). Statistical significance was calculated with Mann-Whitney U test. RESULTS: At both field strengths, T2-SSFSE images received the best ratings, followed by FIESTA images (P=.001). Although, overall, the 3.0-T images obtained scores worse than those of the 1.5-T images, a better detection of phantom polyps was noted in the colon model (P=.001). CONCLUSION: Although MR colonography with the breath-hold technique using the same four-element phased-array coil at 3.0 and 1.5 T does not perform better at a higher field strength in general, an improved detection of small polyps may be obtained.

Colon↗
PubMedDate not supplied

Mitral annulus after mitral repair: geometry and dynamics.

The study of systolic changes in both the inflow and outflow of the left ventricle after mitral repair elucidates the geometric characteristics after surgery. The study included eight normal subjects and six patients after mitral repair without a prosthesis. The left ventricular (LV) base, consisting of both mitral valve annulus (MVA) and left ventricular outflow tract (LVOT) orifice, was reconstructed from magnetic resonance images. The angle between the planes of the MVA and LV base (MB angle), and the proportionate share of the LVOT at the LV base were calculated. After mitral repair, both the MVA and LV base became almost normal in size, showing flexible change (i.e., contraction and dorsiflexion) in the MVA and contraction of the LV base in systole. Compared with the normal heart at 100 ms delay from the electrocardiogram R wave, the hearts of the patients at the same phase had a mean 1.05 cm2 larger LVOT orifice, resulting in a mean 8.0 degree larger MB angle. Furthermore, the LVOT orifice occupied a mean of 49.5% of the LV base (41.9% in normal subjects). We hypothesize that the higher MB angle at early systole may weaken the tension of the chordae of the anterior mitral leaflet.

Adult↗
PubMedDate not supplied

Efficacy of contrast medium use for neuroimaging at 3.0 T: utility of IR-FSE compared to other T1-weighted pulse sequences.

As inversion-recovery (IR) technique improves T1 contrast at high field strength, signal enhancement by T1-shortening contrast media may be affected. To clarify the different enhancement properties at 3.0 T, the authors compared T1-weighted sequences. Twelve contrast-enhancing lesions were investigated by spin-echo (SE), inversion recovery fast spin-echo (IR-FSE), two-dimensional gradient-echo (2D GE), and magnetization-prepared three-dimensional gradient-echo (3D GE) sequences and evaluated by comparing signal-intensity enhancements within the lesions. In addition, signal-to-noise-ratios (SNR) and contrast-to-noise-ratios (CNR) were measured. On average, signal enhancement of the lesions amounted to 60% for SE, 57% for IR-FSE, 32% for 2D GE, and 35% for 3D GE images. CNR of gray matter versus white matter was significantly higher for IR SE and GE imaging than for genuine SE and 2D GE acquisitions (Wilcoxon test), while 2D GE imaging alone had an excellent SNR. As IR-FSE images provide an excellent CNR for gray and white matter in the brain and contrast enhancement performs almost similarly well compared with SE imaging, this technique appears to be well suited for T1-weighted neuroimaging without and with contrast enhancement at 3.0 T. However, the inherent blurring of the IR-FSE can lead to poor performance for very small lesions.

Adult↗