Biomedical subjects
Publications and source records attributed to W Kenn.
We report the case of a 41-year-old man who underwent heart transplantation after suffering from aortic dissection during the implantation of a biventricular assist device for heart failure after coronary artery bypass grafting. The biventricular assist device had to be operated by hand for 10 hours because of a technical defect. In the end perseverance won out and the patient is now doing well at 2.5 years of follow-up.
AIM: Comparison of colour coded duplex sonography (CCDS) to angiography in visualizing arteries and haemodialysis fistulas of the upper extremity. METHOD: 1145 arterial and vein segments were visualised using CCDS and angiography in 219 patients by different examiners with different degrees of experience. Sensitivity, specificity and accuracy were calculated. RESULTS: For the arterial segments--subclavian artery up to the distal lower arm arteries--the sensitivity was 90% and the specificity 99%. The sensitivity for the detection of vascular alterations in haemodialysis fistulas was 89% and the specificity 95%. CONCLUSION: CCDS may be able to replace diagnostic angiography of the arm except when evaluating the hand arteries and the central veins.
PURPOSE: To compare softcopy and hardcopy reading of chest radiographs a software tool was designed for creating lesions with clearly defined size, location and contrast. METHOD: An ROC study was performed using a set of chest radiographs with 300 simulated small nodules and linear details displayed on film and on a 1 K monitor. Six observers participated in the study. ROC curves were generated on the basis of 7200 decisions. RESULTS: There was no significant difference in observer performance overall (AUC = Area under curve). Monitor: 0.84 +/- 0.08 vs. AUC, Film: 0.84 +/- 0.08). Slight, but not statistical significant differences were found in the detection of low-contrast lung nodules and of linear lung details. CONCLUSION: Soft-copy reading using a high quality 1 K CRT display provides the same accuracy for the detection of subtle computer-simulated lesions as hardcopy reading. A software tool could be used for assigning optimal characteristics of CRT- and hardcopy displays using clearly defined lesions as a gold standard.
Congenital coronary artery anomalies are found in 0.3 to 1.3% of patients and can cause ischemic heart disease or sudden cardiac death, especially if the anomalous coronary artery courses between the aortic root and the pulmonary artery. Identification of the anatomic course of the anomalous vessel is not always feasible by conventional radiographic coronary angiography. With MR coronary angiography not only flowing blood but also the vessel anatomy can be imaged. In previous studies, a two-dimensional gradient-echo sequence during breathhold was used demanding both cooperation of the patient and operator skill. The navigator technique reduces respiratory artifacts by retrospective respiratory gating on the diaphragm's position, obviating the need for breathhold studies. Furthermore, the three-dimensional MR coronary angiography enables post-processing using the Volume Rendering Technique for evaluation of three-dimensional view. We report on the use of this technique for the identification of the course of anomalous coronary arteries in two patient cases.
The case of a 66-year-old woman with a primary cardiac osteosarcoma is described. These distinctly rare malignant tumors arise preferentially in the left atrium. Clinically, they often present symptoms of both, intramural and intracavitary neoplasm in addition to general weakness, recurrent breast pain, and dyspnea. As shown in the present case, with growing intracavitary tumor masses the risk for peripheral arterial including cerebral embolism increases. Consequently, in most patients with symptoms of systemic arterial embolism of unknown origin performance of transesophageal echocardiography seems advisible, which is presently the most convenient noninvasive imaging method to exclude or to identify intracardiac sources of emboli, irrespective of their type.
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In order to select those patients with colorectal liver metastases who may have benefit from an operation, preoperative detection and localization of tumors in the liver is necessary. In this study, the specificity and sensitivity of a CT arterial portography and magnetic resonance imaging with contrast media was compared with the results of operative findings and intraoperative ultrasonography. The combination of both preoperative methods led to an accuracy rate of more than 90%, and all patients who underwent laparotomy were resected or treated with an arterial infusion port system. Negative laparotomies were excluded completely.
PURPOSE: Aim of the study was to evaluate the technical aspects of colour coded duplex sonography guided interventions of peripheral vessels. METHODS: During 15 months 39 stenoses of shunt veins in 24 patients were dilated guided by colour coded duplex sonography. RESULTS: 38 stenoses were dilated without complications. The blood flow volume was increased from 361.9 +/- 83.5 to 718.9 +/- 189.2 ml/min. In one case it was not possible to dilate the stenosis because of a vasospasm. CONCLUSION: PTA guided by colour coded duplex sonography is an alternative to DSA guided interventions of superficial vessels without x-ray exposure or contrast agent application.
Fifty children between 3 months postnatal and 16 years of age were examined by means of a 1.5 T superconductive magnet, run at 0.35 and 1.0 T. The myelination was studied qualitatively and quantitatively (relaxation times, proton densities, image contrast). With increasing age, a decrease of T1 and proton density of white matter was found, which was complete at one year of age. In regions with a slow progression of myelination, gray/white matter contrast showed an increase up to the end of the first decade. Pathological white matter maturation was diagnosed either as an abnormal transformation of myelin (characterized by abnormal relaxation values), or as a deficient or delayed myelin formation (in comparison with age-matched controls).
Angiomyoma is a benign tumor that arises from soft muscular tissue within the blood vessel wall. This lesion has been found in different organs. The preferential location of these tumors is the lower extremity. We describe the rare case of a hepatic angiomyoma and present the radiologic findings of computed tomography and magnetic resonance imaging.
Glomus organs are small arteriovenous anastomoses that are chiefly responsible for thermoregulation of the distal portion of the extremities. Glomangiomas are benign tumors of these bodies. Glomangiomas occur preferentially in the fingers and toes, but some case reports have described primary glomangiomas in the respiratory or gastrointestinal tract and the genitals. To date, no glomangiomas of the liver have been observed. We report on a 61-year-old patient in whom routine ultrasound disclosed a subcapsular well-defined mass in the liver. On imaging studies, no correspondence to the usual liver tumors was found. Magnetic resonance-guided biopsy showed a primary glomangioma of the liver. Clinically, the patient had no appetite and lost weight over several months. Due to the patient's weight loss and potential malignant transformation, the tumor was excised. Histologic work-up confirmed the diagnosis of a glomangioma with no signs of malignancy.
PURPOSE: Vena cava filter (VCF) application is the method of choice to prevent recurrent pulmonary embolism in patients with deep venous thrombosis. Because of the reported complications after VCF placement we summarize our long-term follow-up results with the LGM and Titanium Greenfield (TG) devices. METHODS: Eighty-seven LGM VCF and 17 TG VCF were placed in 104 patients (average age 64 years). The follow-up examinations were performed by color-coded duplex sonography, plain radiographs, cavography, and computed tomography (CT). The maximum observation time was 81 months. RESULTS: Filter migration occurred in 11% (8/76) of the LGM VCF and 15% (2/13) of the TG VCF. Vena cava thrombosis was seen in 17% (13/76) of the patients with an LGM VCF and in 31% (4/13) of those with a TG VCF. The patency rate was 95% (72/76) for the LGM VCF and 92% (12/13) for the TG VCF. Pulmonary embolism was noted in 3 patients after LGM VCF insertion and in no patient after TG VCF insertion. CONCLUSION: A VCF should only be inserted in a patient after pulmonary embolism and when there is strict proof of the indication.
The goal of this work was to verify in a phantom study the necessity of a calibration method for comparison in dynamic contrast-enhanced magnetic resonance imaging (MRI) examinations. A perspex phantom with a dilution series of Gd-DTPA was used to measure the dynamic signal enhancement of a sequence. With nine MRI scanners from Bruker (0.23, 0.5, and 2 Tesla), Philips [0.5 and 1.5 Tesla (ACS-NT and S15)], and Siemens (0.2, 1.0, and 1.5 Tesla) one 2D FLASH and two 3D FLASH experiments were performed under identical measurement conditions. Under different measurement conditions (2D and 3D FLASH, TR, TE, FA) different characteristics in signal enhancement exist on a scanner. The same measurement conditions at different scanners (same magnetic field strength) also result in different signal enhancement. Dynamic contrast enhanced MRI examinations from different measurement conditions or scanners cannot be compared. To solve this problem a calibration is needed.
AIM: Our study was designed to evaluate the use of magnetic resonance imaging (MRI) in the follow-up of surgically treated osteochondrosis dissecans (OCD) of the talus. METHOD: We investigated 16 patients (18 joints) with OCD of the talus, surgically treated in our department between 1990 and 1997. All of them had preoperative MRI scans of the affected ankle. The mean follow-up was 40 months (8-82). All patients were evaluated by clinical examination, plain radiography and MRI using a standard protocol. RESULTS: The clinical Bray score improved significantly from 58 preoperative to 82 postoperative. Using a visual analogue scale we saw a significant reduction of the patients pain level post-op. In 72% of the patients the preoperative MRI was able to predict the accurate stage of the cartilage. Postoperative MRI showed no more lesion in 3, intact articular cartilage in 11, and disrupted cartilage in 4 joints. There was no correlation between clinical, plain radiographical, and MRI findings postoperative. CONCLUSION: Arthroscopy remains the golden standard in evaluating articular cartilage. Using our data, MRI is not the method of choice in the follow-up of surgically treated OCD lesions of the talus. Postoperative use of intravenous contrast media gave no additional information. Postoperative MRI should be reserved only for symptomatic patients to gather additional information about the actual state of the OCD. Afterwards a prompt arthroscopy of the symptomatic ankle should be performed.
AIM: This study aims to establish the indication for a pre- and postoperative MRI examination with an intravenous contrast agent in patients with an osteochondral lesion of the talus. METHODS: 20 patients with an osteochondral lesion of the talus in the different stages according to DiPaola were prospectively examined preoperatively and 6 months postoperatively by an MRI investigation with an i. v. contrast agent. The Weber ankle score was determined pre- and postoperatively. A correlation was calculated between MRI and arthroscopic findings of an osteochondral lesion (Spearman-rho). RESULTS: There was a significant correlation among the radiological, the MRI and the arthroscopically determined locations. With regard to staging only 12 out of 20 lesions were staged correctly by MRI using arthroscopy as a gold standard. Due to metal artifacts and morphological changes the postoperative MRI could not be used for staging. CONCLUSION: A preoperative MRI investigation is indicated in patients with ankle pain of unknown origin, a normal radiograph and a suspected osteochondral lesion of the talus. MRI is not indicated to determine the localization and the stage of an osteochondral lesion. A postoperative MRI is only necessary for the exclusion of a secondary pathology.