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Biomedical subjects

M Thelen

Publications and source records attributed to M Thelen.

At least 19 recordsLinked to original sources
PubMed2005

[Classification and treatment of endoleaks after endovascular treatment of abdominal aortic aneurysms].

This article describes the classification of endoleaks after endovascular treatment of abdominal aortic aneurysms, thereby summarizing the most important problems of this endovascular technique. The correct classification of endoleaks is a prerequisite for interdisciplinary discussion. It is indispensable for professional reporting of the pathological findings and for the decision making as to the adequate treatment of endoleaks. Irrespective of the types of stent graft and property of the material, five endoleak types are defined in the literature: leakage at the anchor sites (type I); leakage due to collateral arteries (type II); defective stent grafts (type III); leakage due to porosity of the graft material (type IV); and endotension (type V). The causes of endoleaks are discussed and treatment options are reviewed for the diverse pathologic findings.

Alloys↗
PubMed2005

[Visual assessment of functional lungs parenchyma on HRCT and (3)He-MRI in patients after single lung transplantation: comparison with quantitative volumetric results].

PURPOSE: Visual assessment of the ventilation using HRCT and (3)He-MRI in patients after single lung transplantation (SLTX). Analysis of specific ventilation defects found with (3)He-MRI and morphological changes found with HRCT. MATERIALS AND METHODS: We evaluated 8male patients (54 +/- 6 years) suffering from emphysema and six patients (3males and 3 females, 58 +/- 9.5 years) suffering from idiopathic pulmonary fibrosis (IPF) after SLTX. The morphological changes at HRCT were classified and localized. In (3)He-MRI (2D FLASH), 10 to 14 slices (slice thickness 10 mm, gap 5 mm) were acquired in coronal orientation to cover the whole lung. Ventilation defects were localized and characterized. The visually estimated ventilation was recorded on a 5-point scoring system. A double threshold technique was applied to volumetric quantification in (3)He-MRI to serve as internal reference. RESULTS: We found no correlation between morphological changes in HRCT and ventilation defects in (3)He-MRI. The visual assessment of ventilation in (3)He-MRI was sufficient in patients with emphysema, but this was not confirmed in patients with IPF. The visual assessment in HRCT did not correlate with the volumetric evaluation in both conditions. CONCLUSION: The various ventilation defects were not linked to specific morphological changes. For the visually assessed ventilation in patients with emphysema, (3)He-MRI is superior to HRCT.

Emphysema↗
PubMed2005

[Self-organizing neural networks for automatic detection and classification of contrast (media) enhancement of lesions in dynamic MR-mammography].

PURPOSE: Investigation and statistical evaluation of "Self-Organizing Maps," a special type of neural networks in the field of artificial intelligence, classifying contrast enhancing lesions in dynamic MR-mammography. MATERIAL AND METHODS: 176 investigations with proven histology after core biopsy or operation were randomly divided into two groups. Several Self-Organizing Maps were trained by investigations of the first group to detect and classify contrast enhancing lesions in dynamic MR-mammography. Each single pixel's signal/time curve of all patients within the second group was analyzed by the Self-Organizing Maps. The likelihood of malignancy was visualized by color overlays on the MR-images. At last assessment of contrast-enhancing lesions by each different network was rated visually and evaluated statistically. RESULTS: A well balanced neural network achieved a sensitivity of 90.5 % and a specificity of 72.2 % in predicting malignancy of 88 enhancing lesions. Detailed analysis of false-positive results revealed that every second fibroadenoma showed a "typical malignant" signal/time curve without any chance to differentiate between fibroadenomas and malignant tissue regarding contrast enhancement alone; but this special group of lesions was represented by a well-defined area of the Self-Organizing Map. DISCUSSION: Self-Organizing Maps are capable of classifying a dynamic signal/time curve as "typical benign" or "typical malignant." Therefore, they can be used as second opinion. In view of the now known localization of fibroadenomas enhancing like malignant tumors at the Self-Organizing Map, these lesions could be passed to further analysis by additional post-processing elements (e.g., based on T2-weighted series or morphology analysis) in the future.

Algorithms↗
PubMed2005

[Systematic analysis of the geometry of a defined contrast medium bolus--implications for contrast enhanced 3D MR-angiography of thoracic vessels].

PURPOSE: Little is known about the dispersion of a defined contrast bolus during its passage through the heart and pulmonary vasculature. The purpose of this study was to analyze factors influencing a defined contrast bolus for ce-MRA of thoracic vessels. MATERIALS AND METHODS: For analysis of bolus geometry, an ECG-gated saturation-recovery Turbo-Flash sequence with a TI of 20 msec was used. It was acquired axially at the level of the pulmonary trunc, so that with one data acquisition a curve analysis was possible in the ascending and descending aorta, and in the pulmonary trunc. Twenty-nine patients received 3 ml of Gd-DTPA diluted with saline to a total of 20 ml. Contrast injection was done using a MR compatible power injector with injection rates varying between 1, 2 and 4 ml/sec. Each injection was followed by a saline flush of 20 ml with the same injection rate and mode. Cardiac function was assessed by cine imaging, and phase contrast measurements. After normalization to baseline signal intensity (SI), bolus curves were fitted using a gamma-variate fit and peak signal intensity (peak SI), time-to-peak (TP), upslope, mean transit time (MTT) and dispersion of the contrast bolus were calculated. Furthermore, T (1) and [Gd] in the experimental setting were calculated as follows: T (1) = T (1 o)/ ln [SI/SI (0)], and [Gd] (exp) = [1/T (1) - 1/T (1 o)]/ R (1.) They were then extrapolated [Gd] to clinical conditions by [Gd] (clin) = [Gd] (exp) . 10/1.5, and minimal blood T (1) by T (1)(clin) = 1 / [1/T (1 o) + R (1) [Gd] (clin)]. RESULTS: With increasing injection rate, there was a significant decrease (p < 0.001) of MTT in all target vessels. However, this decrease was not linear: a 4-fold increase in injection rate lead to a 2-fold decrease in MTT e. g. in the ascending aorta. MTT was significantly shorter in the pulmonary trunc compared with that in the ascending and descending aorta (p < 0.001), regardless of injection rate (p < 0.001). Vice versa, dispersion of the contrast bolus was significantly lower in the pulmonary trunc, and increased with higher injection rates. There was no clinically relevant difference in minimal blood T (1) between the different target vessels, for clinical conditions extrapolated values ranged between 20 und 79 msec. Heart function parameters only had a minor influence of bolus curve parameters. CONCLUSION: Analysis of bolus geometry enables determination of transit times of a defined contrast bolus through a defined target vessel in the thoracic cavity. Bolus geometry is mainly determined by injection parameters, cardiac function is of minor importance. Dispersion of contrast bolus and MTT increase from the pulmonary trunc to the ascending aorta. The knowledge of these facts may help optimizing of injection parameters and the total amount of contrast agent for contrast-enhanced MRA of thoracic vessels.

Adult↗
PubMed2005

[TACE: therapy of the HCC before liver transplantation--experiences].

PURPOSE: Analysis of the course of disease in patients with histologically proven HCC before and after orthotopic liver transplantation (LTx) who received transarterial chemoembolization (TACE). MATERIAL AND METHODS: Thirty-five of a total collective of 363 patients with histologically proven HCC underwent LTx. Before LTx, all patients were treated with sequential TACE. According to treatment pattern, TACE should be performed every 6 weeks, using a suspension consisting of max. 10 mg Mitomycin C as well as 10 - 30 ml iodized oil (Lipiodol). Patients were classified according to the Milano criteria. Criteria were called exceeded if the tumor size was > 5 cm and/or > 3 tumors larger than 3 cm were found. Therapy success and liver function were examined by means of spiral CT and laboratory controls. Investigation parameters included the number of tumor knots as well as the maximum tumor size. Additionally, the Lipiodol accumulation, the patency of the portal vein and the occurrence of complications were checked. RESULTS: Altogether, 184 TACE procedures were accomplished (5.3 +/- 3.3, range 1 - 14). The waiting period up to the transplantation amounted to 366 +/- 255 days (range 44 - 1137). The average number of tumor knots for each patient was 3.1 +/- 2.2 before and 2.9 +/- 2.2 after TACE (p = 0.887). The average tumor size was 4.2 +/- 2.5 before and 2.8 +/- 1.4 after TACE. The Milano criteria to LTx crossed 17/35 patients. Patients with exceeded Milan criteria showed a highly significant size reduction of the tumor after TACE (p = 0.001); in 9/17 cases the transplantation criteria were secondarily fulfilled through downstaging. A successful LTx was accomplished in 35/35 cases. Follow up after LTx was 769 +/- 509 days. The tumor recurrence in patients with exceeded vs. fulfilled transplantation criteria was 11.1 % vs. 11.8 % (p = 0.99). The recurrence free survival was 93.3 %, 82.5 % and 82.5 % at 1, 3 and 5 years, respectively. There were no relevant differences between patients with exceeded vs. fulfilled transplantation criteria (p = 0.99). CONCLUSION: The sequential TACE is an effective method for the therapy of the HCC before LTx in selected patients. A relevant downsizing could be achieved by TACE in patients with advanced HCC. Patients with larger tumors showed a significantly stronger size reduction after TACE. The recurrence rate and the survival rate for patients with advanced or small tumors do not differ.

Adult↗
PubMed2005

[Does HRCT-emphysema index represent the entire lung?].

PURPOSE: : Comparison of emphysema index derived of thin section MD-CT of the entire lung volume and HRCT, simulated by calculation of every twentieth image of the whole data-set. MATERIALS AND METHODS: Pulmonary emphysema was quantified by semiautomatic, segmentation of lung borders and assessment of lung volume and emphysema volume within these borders. The emphysema index (pixel index) was calculated. Statistical analysis was done by the sign-test and Bland-Altman-analysis. RESULTS: Median lung volume, emphysema volume and emphysema index are significantly higher in simulated HRCT. Median lung volume (emphysema volume) calculated by HRCT is 5118 ml (407 ml) and 5040 ml (367 ml) calculated by the entire MD-CT data-set, representing differences of 1 and 8 % related to the median lung and emphysema volumes. Emphysema index is 0.09 (HRCT) and 0.08 (MD-CT). CONCLUSION: HRCT overrates emphysema index compared to thin section MD-CT of the entire lung volume.

Adolescent↗
PubMed2005

[Prospective benefit and effect of lipiodol marking in hepatocellular carcinoma].

PURPOSE: To assess the benefit and the effect of intraarterial lipiodol application on histological analysis of patients suspected of having HCC. To determine whether lipiodol marking leads to a better biopsy result and how lipiodol or a transarterial chemoembolization influences the histological diagnosis. MATERIALS AND METHODS: Two groups of patients were examined. Group A included 14 patients highly suspected of having an HCC which had previously been unsuccessfully biopsied. A transarterial embolization with lipiodol was performed in these patients to mark intrahepatic tumors which could not otherwise be defined in unenhanced CT. A biopsy was then repeated. Group B included 22 patients undergoing therapy using transarterial chemoembolization (TACE). A biopsy was performed to support the diagnosis of a multifocal HCC before changing the therapy. RESULTS: The transversal diameters of the biopsied tumors were similar in both groups (A: 22 mm; B: 21 mm). The length of percutaneous access was 71 mm in Group A and 88 mm in Group B. In eleven of 14 patients of Group A we confirmed the diagnosis of an HCC. Thirty-six procedures were necessary for this confirmation. In Group B we confirmed the diagnosis in 17 of 22 patients. In addition, we found typical histological modification due to hepatic cirrhosis and virus hepatitis. Lipiodol had no negative influence on the histological diagnosis. CONCLUSION: Applying lipiodol for marking and delineating HCC-suspicious liver tumors in cases of formerly negative histology seems to enhance the success of biopsy, confirming the diagnosis of an HCC.

Aged↗
PubMed2004

Assessment of right ventricular function by 16-detector-row CT: comparison with magnetic resonance imaging.

The purpose of this study was to determine right ventricular (RV) function from 16-detector-row CT by using two different software tools in comparison with MRI. Nineteen patients underwent cardiac CT. (1) With semiautomated contour detection software end-diastolic and end-systolic RV volumes were determined from short-axis CT reformations (MPR) created at every 10% of the RR-interval. (2) End-systolic and end-diastolic axial images were transformed to 3D to determine the volumes by using a threshold-supported reconstruction algorithm. Steady-state free-precession cine-MRI of the heart was done in short-axis orientation. RV function could not be analyzed in one patient because of sternal wire artifacts in MRI. Mean end-diastolic (155.4+/-54.6 ml) and end-systolic (79.1+/-37.0 ml) RV volumes determined with MPR correlated well with MRI [151.9+/-53.7 ml (r=0.98) and 75.0+/-36.0 ml (r=0.96), respectively (P<0.001)]. RV stroke volume (76.2+/-20.2 ml for MPR-CT, 76.9+/-20.7 ml for MRI, r=0.93) showed a good correlation and RV ejection fraction (50.8+/-8.4% for MPR-CT, 51.9+/-7.4% for MRI, r=0.74) only a moderate one. Threshold supported 3D reconstructions revealed insufficient correlations with MRI (r=0.31-0.59). MPR-based semiautomated analysis of cardiac 16 detector-row CT allows for RV functional analysis. The results correlate well with MRI findings. Threshold value-supported 3D reconstructions did not show satisfying results because of inhomogeneities of RV contrast enhancement.

Aged↗
PubMed2004

Minilaparoscopy in the diagnosis of peritoneal tumor spread: prospective controlled comparison with computed tomography.

BACKGROUND: Early diagnosis of peritoneal spread in malignant disease prevents unnecessary laparotomies. Minimally invasive laparoscopy with the patient under conscious sedation is a new, easily feasible diagnostic technique. This study compares prospective and controlled diagnostic minilaparoscopy with computed tomography (CT) scan for the diagnosis of peritoneal metastases. METHODS: In this study, 56 patients with malignant disease were prospectively investigated with diagnostic minilaparoscopy and CT scan. RESULTS: The study criteria were fulfilled by 54 patients. Minilaparoscopy detected peritoneal carcinosis in 28 of 54 cases, whereas CT detected the disease in 14 of 54 cases. For 36 patients, the diagnosis could be verified by histologic examination of peritoneal biopsies or laparotomy. In this group, minilaparoscopy detected peritoneal carcinosis in 25 of 36 cases, whereas CT detected the disease in 12 of 36 cases. CONCLUSIONS: Minilaparoscopy was more sensitive than CT in detecting peritoneal carcinosis (100% vs 47.8%; p < 0.01). Considering its low grade of invasiveness and superior sensitivity, minilaparoscopy should be regarded as the procedure of choice for the early detection of peritoneal carcinosis.

Adult↗
PubMed2004

Preoperative imaging of hilar cholangiocarcinoma: surgical evaluation of standard practises.

UNLABELLED: It was the goal of this study to compare the results of the preoperative diagnostic workup (ERC, MRC, and PTC) with the tumor extent of the surgical specimen in patients with hilar cholangiocarcinoma (hilCC). PATIENTS AND METHODS: Between 9/97 and 12/2002 82 patients with hilCC were treated at our institution. In 59 patients tumor resection was feasible. Preoperative ERC, MRC and PTC - blinded for the idendity of the patients - were analysed retrospectively and compared with the surgical specimen. RESULTS: PTC resulted in significantly superior visualization of the bile ducts including the hilar lesion compared to ERC and MRC (p < 0.01). ERC, MRC and PTC were correct in predicting tumor extent in 29, 36 and 53 % of cases, respectively. The extent of the tumor was overestimated in 42 % (ERC), 41 % (MRC) and 31 % (PTC). Underestimation or wrong assessment or no decision at all occurred in 31, 23 and 16 %, respectively. In 20 patients results of all three diagnostic methods were available allowing a statistical comparison regarding the resection to be performed: PTC was superior to ERC (McNemar test:p < 0.01), but not to MRC. In the patients with overestimated tumor extent both the rate of curative resections and survival were similar to the other resected patients. DISCUSSION: In contrast to most reports in the literature, ERC and MRC were found to be of limited reliability regarding the assessment of tumor extent. PTC proved to be the most reliable approach. Overestimation of the tumor extent, which may lead to exclude the patient from potentially curative surgery, was the most common mistake in each diagnostic modality.

Bile Duct Neoplasms↗
PubMed2004

[Quantification of atelectases in artificial respiration: spiral-CT versus dynamic single-slice CT].

PURPOSE: Dynamic CT (dCT) allows visualization and quantification of ventilated lung and atelectases with high temporal resolution during continuous ventilation. This study compares a quantitative image analysis in a subcarinal single slice dCT series versus a whole lung spiral-CT, in order to analyze, whether the distribution of atelectasis of a single dCT series is representative for the whole lung. MATERIALS AND METHODS: dCT in sliding windows technique (slice thickness 1 mm, temporal increment 100 ms) was performed in 8 healthy pigs 3 cm caudal to the carina during continuous mechanical ventilation. Subsequently, a spiral-CT of the whole lung (slice thickness 2 mm; pitch 1.5; increment 2 mm) was acquired during inspiratory breath hold (airway pressure 20 mbar). Lung segmentation and planimetry of predefined density ranges were achieved using a dedicated software tool in both data-sets. Thus, the fractions of the following functional lung compartments were averaged over time: hyperinflated lung (- 1024 to - 910 HE), normal ventilated lung -900 to -300 HE) and atelectasis (-300 to +200 HE). RESULTS: Quantitative analysis of dCT-series during continuous respiration correlated with the density analysis in spiral-CT as follows: hyperinflated lung r = 0.56; normal ventilated lung r = 0.83 and atelectases r = 0.84. Analysis of spiral-CT showed the following distribution of functional lung compartments: hyperinflated lung 3.1% normal ventilated lung 77.9% and atelectasis 19.0%. In dCT, hyperinflated lung represented 6.4%, normal ventilated lung 65.2% and atelectasis 28.4% of total the lung area. CONCLUSION: The results of our study demonstrate that dCT allows monitoring of atelectasis formation in response to different ventilatory strategies. However, a deviation between dCT and spiral-CT has to be taken into account. In subcarinal dCT series, hyperinflated lung areas and atelectases were overestimated due to a craniocaudal gradient of atelectases, whereas normal ventilated lung was underestimated.

Animals↗
PubMed2004

[Contrast-enhanced 3D MR angiography of the pulmonary arteries with integrated parallel acquisition technique (iPAT) in patients with chronic-thromboembolic pulmonary hypertension CTEPH - sagittal or coronal acquisition?].

PURPOSE: Comparison of two different types of contrast-enhanced 3D-MR angiography (CE-MRA) with integrated parallel acquisition technique (iPAT) in patients with chronic-thromboembolic pulmonary hypertension (CTEPH) and evaluation whether sagittal acquisition with higher resolution and minimized acquisition time is superior to common coronal orientation. MATERIALS AND METHODS: CE-MRA was performed on 15 patients with CTEPH preoperatively and on 10 patients also postoperatively, while 5 other patients received only a postoperative MRA. All 30 MR studies with one coronal and two sagittal acquisitions were blindly evaluated and compared. The resolution of coronal and sagittal MRA was 1.3 x 0.6 x 1.4 mm (3) and 1.2 x 1.2 x 1.2 mm (3), and acquisition time 20 and 17 sec (iPAT factor 2, GRAPPA), respectively. Image quality, coverage of the pulmonary arteries, delineation of patent segmental and sub-segmental vessels and pathological findings were assessed. A total of 1980 vessels were evaluated. RESULTS: Sagittal 3D-MRA was superior in overall image quality and complete coverage of the vessels compared to coronal MRA, 18 % of subsegmental and 4.3 % of segmental arteries as well as 1.1 % of the lobar vessels were not covered by coronal acquisition. Only 0.5 % of sagittal subsegments were missed. The number of depicted patent segmental and subsegmental arteries was higher in sagittal MRA (460 vs 489 and 573 vs 649, respectively), the total difference of patent vessels was 105. Sagittal MRA revealed more pathological findings in segmental arteries (especially thrombotic material and stenoses). CONCLUSION: Sagittal CE-MRA of the pulmonary arteries with higher resolution and short acquisition time proved to be superior in all assessed criterias like image quality, vessel coverage, depiction of patent peripheral arteries and pathological findings compared to coronal MRA. The applied sagittal MRA is recommended for the routine practise in diagnostic evaluation of patients with CTEPH.

Chronic Disease↗
PubMed2004

[Experimental in vitro study to evaluate a flat-panel detector system].

PURPOSE: To evaluate the contrast-detail performance of a flat-panel detector system, we performed a comparative study of this flat-panel system versus storage phosphor and conventional screen-film systems. MATERIALS AND METHODS: Bone models made of human humeri were prepared with foreign bodies, fracture lines and drilled holes to create artificial fractures, osteolyses or metastases. Immersed in a water bath, hard copy images of these models were acquired with the same exposure dose (55 kV; 3.2 mAs) on the flat-panel detector, two state-of-the-art storage phosphor systems (PCR, ADC) and two conventional screen-film systems (Insight, T-Mat). Using a standardized protocol with a 4-point scale for a lesion, 220 different images were analyzed as to their appearance by 5 independent radiologists. The statistical significance of the differences between the used modalities and the observers was determined with a sign test. RESULTS: Especially the drilled holes showed differences between the modalities. The flat-panel detector showed significantly slightly better results locally than the two storage phosphor systems. The same applied to the Insight screen-film systems, but the intraindividual differences between the modalities were not clinically relevant. CONCLUSION: Under the conditions of the chosen experimental design, the flat-panel detector showed results comparable to the conventional screen-film and the state of the art storage phosphor radiographs. The use in skeletal radiography is possible.

Bezoars↗
PubMed2004

[Evaluation of percutaneous vertebroplasty in osteoporotic vertebral fractures using a combination of CT fluoroscopy and conventional lateral fluoroscopy].

PURPOSE: Evaluation of vertebroplasty using a combination of CT-fluoroscopy and conventional lateral fluoroscopy in patients with osteoporotic vertebral fractures. MATERIALS AND METHODS: Fifty-eight patients (23male, 35 women, age 69.7 +/- 10.2 years) with painful osteoporotic vertebral fractures were treated with vertebroplasty in conscious sedation and local anesthesia. Spiral-CT with sagittal reconstructions of the respective vertebral bodies was used for classification of the fracture. The cannula was placed under CT-guidance in the ventral third of the respective vertebral bodies and cement instilled under CT fluoroscopy and lateral fluoroscopy. When cement migrated towards the vertebral canal, the injection was immediately stopped for 30 - 60 seconds. After polymerization in this location, the injection was continued until sufficient filling of the vertebra. Results were documented by spiral CT with sagittal reconstructions. RESULTS: A total of 123 vertebral bodies were treated, comprising 39 thoracic and 84 lumbar vertebral bodies, with a mean of 2.1 +/- 1.3 (range 1 to 6) vertebral bodies in each patient and a maximum of 3 vertebral bodies per session. All interventions were successfully completed in conscious sedation and local anesthesia. A mean volume of 5.9 +/- 0.6 ml (range 2 to 14 ml) cement was applied for each vertebra, with 79.7 % of procedures performed using a unilateral access. To achieve a sufficient cement deposit, a bilateral access was used in 20.3 %. The dorsal wall of the vertebra was included in 23.6 % of the fractures. In one case, cement migration into the spinal canal was detected, reducing the diameter of the canal by 30 %. In two other cases, cement leakage was seen at the puncture site of the vertebra (one intercostotransversally in the 10 (th) thoracic vertebra and one dorsolaterally in the 1 (st) lumbar vertebra) with retrograde cement migration through the neuroforamen into the epidural space. In one of these cases, the cannulation of the vertebra had been changed before cement application resulting in a hole in the dorsolateral vertebral wall. However, all patients were discharged without evidence of neurologic complications. Multiplanar reconstructions of CT scans were used for the detection of extraosseous cement leaks: The incidence of extraosseous cement leaks was 4.1 % in epidural veins, 6.5 % in paravertebral vessels (6 veins, 2 arteries), and 17.9 and 11.4 %, respectively, for upper or lower end plates. At discharge, 25 patients (43.1 %) were free of pain and 28 (48.3 %) significantly improved with a considerable reduction of analgetic drugs. Significant complaints persisted in 5 patients (8.6 %) with concomitant degenerative disease in four and vasculitis in one case. CONCLUSION: Percutaneous vertebroplasty is effective for stabilization and pain management of osteoporotic vertebral fractures. The procedure can be safely performed in conscious sedation and local anesthesia. Compared to conventional fluoroscopy alone, CT fluoroscopy provides an excellent additional monitoring of the procedure and probably contributes to the safety of the procedure.

Adult↗
PubMed2004

[Comparison of contrast-enhanced MR angiography of the aortoiliac vessels using a 1.0 molar contrast agent at 1.0 T with intra-arterial digital subtraction angiography].

PURPOSE: To evaluate the diagnostic accuracy of contrast-enhanced MR angiography (CE-MRA) using a 1.0 molar contrast agent at 1.0 T for the diagnosis of abdominal aortic aneurysms and stenoses of renal or iliac arteries in comparison to intraarterial digital subtraction angiography (DSA). MATERIALS AND METHODS: A total of 19 patients with the suspicion of abdominal aortic aneurysm or stenosis of renal or iliac arteries were examined with CE-MRA at 1.0 T. Intra-arterial DSA served as reference in all cases. After test bolus tracking, 10 or 8 ml of the 1.0 molar contrast agent Gadobutrol corresponding to a dose of 0.1 - 0.15 mmol/kg bw were injected and imaging performed using a FLASH-3D sequence. To evaluate the interobserver-variability, the blinded images were analyzed by two radiologists. Besides the rating of overall image quality on a 4-point-scale, the images were evaluated for aneurysms and arteriosclerotic lesions with a stenosis of < 50 % or > 50 % or occlusion. RESULTS: A total of 144 segments were analyzed. The mean value of the CE-MRA image quality was 3.4 on a 4-point-scale. The sensitivity of CE-MRA in depicting relevant pathological findings was 96 % and the specificity 99 %. The positive predictive value was 96 % and the negative predictive value 99 %. Inter-observer variability was low with a kappa value of 0.82. CONCLUSION: CE-MRA using a 1.0 molar contrast agent at 1.0 T enables an excellent diagnosis or exclusion of pathologies of the aortoiliac vessels.

Adult↗
PubMed2004

[Non-invasive assessment of coronary artery bypass grafts -- an update].

The limited lifetime and the correlation between graft occlusion and recurring symptoms underline the need for repeated imaging of coronary artery bypass grafts. CT and MRI allow for non-invasive imaging of coronary bypasses with high accuracies concerning the patency of these vessels. Multidetector CT seems to be the CT technique of choice, especially after the introduction of 16 slice CT scanners for morphologic assessment of coronary artery bypass grafts. Compared with MRI, CT is a robust technique for assessment of cardiac anastomoses, native coronary arteries, and for the detection of graft stenoses. MRI, however, is able to deliver functional information about the grafts and the recipient coronary arteries by determining the coronary flow reserve. Furthermore, it can be integrated in a multiparametric MR examination protocol. The follow-up of asymptomatic patients can primarily be done by these non-invasive techniques as nearly every third patient reveals an asymptomatic bypass occlusion 5 years after operation. Furthermore, patients with atypical complaints after the operation may undergo non-invasive imaging as long as documented patency of the bypass averts coronary angiography. Patients with recurrent angina pectoris and/or myocardial ischemia discovered by other cardiologic tests have to undergo coronary angiography.

Coronary Artery Bypass↗
PubMed2004

[Anthracycline-induced cardiotoxicity: cardiac MRI after treatment for childhood cancer].

PURPOSE: Quantification of left and right ventricular function using MRI in young cancer patients treated with cardiotoxic anthracyclines. MATERIALS AND METHODS: Twenty-eight patients (mean age 16.4 years) underwent cardiac MRI at 1.5 T. The study protocol consisted of morphologic T2-weighted images with fat suppression and cine steady-state free precession sequences (SSFP) for functional analysis. Seven patients were examined at the end of chemotherapy, two of them also repeatedly during therapy, and 21 patients following an average period of three years after finishing chemotherapy (range one month--20 years) RESULTS: The end-systolic volume index increased and the ejection fraction of the left and right ventricle decreased during anthracycline therapy. Two of seven patients showed a myocardial edema at the end of the therapy. In 15 of all 28 patients, the left ventricular ejection fraction was reduced to less than 55 % (minimum 44 %). No clinical signs of cardiac insufficiency or cardiomyopathy were observed. CONCLUSION: MRI is able to detect acute as well as chronic subclinical cardiotoxic effects of anthracyclines. Impairment of the right ventricular function should be considered in the diagnosis of anthracycline-induced cardiomyopathy.

Adolescent↗