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K F Kreitner

Publications and source records attributed to K F Kreitner.

At least 55 records · Page 3Linked to original sources
PubMed1999

[Intraoperative flow measurement of coronary bypass grafts using the ultrasound transit time flowmeter].

The aim of the study was to compare the mean and maximum flow and the flow pattern of coronary vein grafts (SVG) supplying target vessels of the inferior and lateral wall with internal mammary (IMA) grafts to the left anterior descending artery (LAD). In 21 patients 25 bypass grafts (13/25 SVG, 12/25 IMA) were investigated. Using the transit time ultrasound method, flow was measured every 5 ms and the flow data of 60 s were acquired. The flow pattern showed significant differences between both graft types during their cycle. IMA grafts showed only one peak occurring after 22.1+/-12.3% and the second after 63.4+/-15.5% of their cycle. The mean flow was not different in both graft types (IMA: 45.3+/-27.0 ml/min and SVG: 41.8+/-26.7 ml/min, p = n. s.) as it was the case for the maximum flow (IMS: 98. 4+/-45.2 ml/min and SVG: 75.7+/-55.4 ml/min, p = n. s.). In conclusion, there is a different flow pattern for both graft types concerning the number and the occurrence of flow-peaks in the bypass cycle. The mean and peak flow showed no significant difference.

Adult↗
PubMed1999

[MR angiography of peripheral vessels with automatic tracking table technique at 1.0 in comparison with intra-arterial digital subtraction angiography].

PURPOSE: Contrast-enhanced (CE) 3D-MR angiography of peripheral arteries was performed in 8 patients with peripheral arterial occlusive disease by applying a new tracking technique on a 1.0 T system (Magnetom Harmony, Siemens). The studies were compared with intra-arterial digital angiography as gold standard. MATERIALS AND METHODS: Imaging of the distal aorta, pelvis, upper and lower limb arteries was accomplished with a Flash-3D-sequence (TR/TE = 6.2/3.2 ms) within 26 s acquisition time of each region after a single bolus of 30 ml contrast agent. Individual circulation time was determined by a test bolus before each examination. RESULTS: 112 vessel segments were evaluated. MR angiography achieved a sensitivity of 89% and a specificity of 100% for detecting high grade stenoses and vessel occlusions. CONCLUSIONS: Tracking CE 3D-MR angiography with a 1.0 T MR imager proved to be a promising method in evaluating hemodynamically significant stenoses and occlusions of peripheral arteries. However, its definite role in the diagnostic work-up of peripheral arterial occlusive disease has to be evaluated in larger prospective studies.

Angiography, Digital Subtraction↗
PubMed1999

[Low-field MRI of the knee joint: results of a prospective, arthroscopically controlled study].

PURPOSE: To define the diagnostic accuracy of an open low-field MR unit (Magnetom Open, Siemens, Erlangen) in traumatic knee lesions. MATERIALS AND METHODS: The MRIs of 150 patients were prospectively evaluated by two independent readers with different experience levels. The study protocol included a proton-density weighted SE-sequence in the sagittal, a T2.-weighted Flash-2D-sequence in the coronal, and a 3D-acquisition (DESS) in the axial plane. 75 patients were treated either conservatively or operatively. RESULTS: Based on arthroscopy as the gold standard, the sensitivities, specificities, and diagnostic accuracies for lesions of the medial and lateral meniscus, the anterior cruciate ligament (ACL), the hyaline cartilage, and the posterior cruciate ligament (PCL) were 92%, 92% and 92%, 83%, 93% and 92%, 95%, 96% and 96%, 74%, 93% and 85%, and 100%, respectively, for reader 1. The values for reader 2 were 81%, 74% and 77% (medial meniscus), 61%, 86% and 80% (lateral meniscus), 79%, 95% and 91% (ACL), 48%, 91% and 73% (hyaline cartilage), and 100% each (PCL), respectively. There were no statistical differences between the two readers (Fisher's Exact Test, 95%-confidence interval). CONCLUSIONS: Using a time-consuming examination protocol, the diagnostic accuracies of the open low-field MR unit are well comparable to those obtained with mid- or high-field units. Although not statistically significant in this study, the experience level of the examiner seems to be of considerable clinical relevance.

Adult↗
PubMed1999

[Sarcoma of the pulmonary artery--pre- and postoperative radiologic findings in initial tumor manifestation and recurrence].

PURPOSE: Primary pulmonary artery sarcomas are very rare tumors. Their diagnosis is difficult due to their unspecific symptoms. Still, an early preoperative diagnosis is the only possibility for a potential therapy. PATIENTS AND METHODS: 4 pre- and 5 postoperative CT- and three pre- and one postoperative MRT-examination(s) have been evaluated with respect to surgical and histological findings. RESULTS: The presence of a convex intraluminal bulging mass spreading mostly from the pulmonary trunc continuously into the peripheral pulmonary artery branches the filling and dilatation of the vessels, the tumor's inhomogeneity indicating hemorrhages and necrosis and the appearance of intrapulmonary nodules are found in both CT and MRI. Recurrent pulmonary artery sarcoma features an extravascular growth and is similar to lung cancer affecting the vessels. It shows contrast enhancement both in CT and MRI while the primary tumor shows a distinct contrast enhancement only of Gadopentetate dimeglumine but none or little enhancement in CT. CONCLUSION: The criteria presented in knowledge of CT and MRI serve to increase the probability for a correct preoperative diagnosis and thus allow adequate surgical planning.

Adult↗
PubMed1999

[The assessment of the patency of coronary bypass vessels with a 2D T2-weighted turbo-spin-echo sequence (HASTE) in the breath-hold technic].

AIM: To evaluate the patency of coronary artery bypass grafts with a 2D T2-weighted breath-hold turbo-spin-echo sequence. METHODS: 38 patients with 97 grafts (19 internal mammary artery and 78 saphenous vein grafts) and a total of 120 distal anastomoses were studied at 1.5 Tesla in supine position using a phased array body coil. An ECG gated 2D T2-weighted breath-hold turbo-spin-echo sequence (HASTE) was performed. Reference method was selective coronary angiography. The image material was evaluated independently by two radiologists (observer one, a radiological fellow and the second a staff radiologist). RESULTS: Observer 1 reached a sensitivity of 96% (72/75) and a specificity of 91% (20/22), positive predictive value was 97%, negative predictive value 87%. 79 of the 97 (81%) patent distal anastomoses were correctly identified. Observer 2 achieved a sensitivity of 92% (69/75) and a specificity of 82% (18/22), positive and negative predictive values were 95% and 75% respectively. From 97 patent distal anastomoses 59 (61%) were recognized. The interobserver agreement was good (Cohen's kappa = 68%, p-value [McNemar] = 58%). CONCLUSION: Using the HASTE sequence a reliable assessment of graft patency is possible. This sequence is a helpful tool for planning flow measurements and 3D MR angiography.

Aged↗
PubMed1999

Contributions of dynamic phosphorus-31 magnetic resonance spectroscopy to the analysis of muscle fiber distribution.

RATIONALE AND OBJECTIVES: In high-performance athletes, conclusions regarding the muscle fiber distribution were to be drawn from dynamic 31phosphorus magnetic resonance spectroscopy (31P MRS). METHODS: Eleven volleyball players (V), eight bodybuilders (B), and 22 nonathletic volunteers (N) were examined by dynamic 31P MRS. During rest, exhaustive exercise, and recovery, respectively, up to 60 consecutive phosphorus spectra of the quadriceps muscle were acquired by "time series" in 36 s each. Two main spectroscopic approaches to the spectroscopic analysis of muscle fiber distribution were applied: evaluation of the ratio Pi/PCr at rest and the computer-assisted analysis of the Pi-peak at its exercise-induced line width maximum. RESULTS: At rest, the bodybuilders showed a significant lower Pi/PCr (0.07 +/- 0.03), in comparison with the volleyball players (0.11 +/- 0.03) and the nonathletic volunteers (0.11 +/- 0.02). The computer-assisted analysis of the Pi-peak at its line width maximum revealed a significantly lower pH of both of the subpeaks in the bodybuilders [6.30 versus 6.37 (V) and 6.38 (N); 6.89 versus 6.92 (V, N)], whereas the volleyball players provided the largest proportion of oxidative muscle fibers (68%), compared to bodybuilders (64%) and nonathletic volunteers (59%). A correlation between the ratio Pi/PCr and the area of the subpeak with the high pH (representing oxidative fibers) could not be demonstrated. CONCLUSIONS: Spectroscopic results during rest and exercise may be influenced by the muscle fiber distribution of the respective volunteer. The applied spectroscopic approaches to the analysis of muscle fiber composition are not compatible with each other; depending on the applied method, the classification of a muscle fiber as type I or type II fiber may change. The influence of physiologic factors like muscle fiber distribution on spectroscopic results has to be considered in the interpretation of pathological conditions.

Adult↗
PubMed1999

Assessment of coronary artery bypass grafts: value of different breath-hold MR imaging techniques.

OBJECTIVE: Our aim was to evaluate the patency of coronary artery bypass grafts and to detect graft stenosis using different breath-hold MR imaging techniques. SUBJECTS AND METHODS: Twenty-two patients with 59 grafts (14 internal mammary artery grafts and 45 saphenous vein grafts) and 76 distal anastomoses (singular and sequential grafts) were studied using a 1.5-T scanner. A two-dimensional T2-weighted breath-hold half-Fourier acquisition single-shot turbo spin echo (HASTE) sequence and a three-dimensional breath-hold contrast-enhanced MR angiography sequence (fast imaging with steady-state free precession) were performed. For MR angiography, a bolus of 20 ml of gadopentetate dimeglumine was used. Time delay for contrast injection was calculated by a test bolus. The gold standard was coronary angiography performed within 14 days of MR imaging. All images were evaluated independently by two radiologists. RESULTS: With the HASTE sequence, 95% of the patent grafts were recognized (42/44); specificity was 93% (14/15). MR angiography had both a sensitivity (41/44) and specificity (14/15) of 93%. Interobserver agreement for both sequences was good (Cohen's kappa = 87%; McNemar test, p = 56%). Forty-nine (83%) of 59 patent distal graft anastomoses were revealed with the HASTE sequence; 38 (64%) of 59 were seen on contrast-enhanced angiography. With HASTE imaging, only two of eight hemodynamically significant graft stenoses were detected. MR angiography revealed only four of eight significant graft stenoses. CONCLUSION: The HASTE sequence and three-dimensional MR angiography proved to be useful MR techniques when evaluating the patency of coronary artery bypass grafts. However, reliable detection of graft stenosis does not yet seem possible with these imaging techniques.

Aged↗
PubMed1999

[Cohen's kappa or McNemar's test? A comparison of binary repeated measurements].

This article intends to illustrate the combination of McNemar's significance test and Cohen's kappa coefficient in the comparison of repeated binary measurements. Both methods are standard statistical tools of major relevance for the evaluation and comparison of clinical imaging methods and thus have an impact on the corresponding publications. The interpretation of results obtainable with these methods will be illustrated to facilitate their use based on recent statistical software. Examples will further outline limitations and possible pitfalls in their application to clinical data.

Data Interpretation, Statistical↗
PubMed1998

[Cryotherapy of liver metastases. Initial results].

PATIENTS AND METHOD: Between 1 Jan 1996 and 1 Apr 1998 29 patients underwent cryosurgical therapy for liver metastasis at the Department of Surgery at the University of Mainz. RESULTS: No complications occurred following cryosurgery alone (n = 12). Within the group of patients with a combined procedure (n = 11) 1 patient had temporary liver failure and 1 patient died of sepsis. Following freezing of the cutting zone (n = 6) 1 patient showed a bile fistula and 1 ascites. In 15 cases of 28 dismissed patients with remaining destroyed tumor tissue the follow-up showed no tumor recurrence (median follow-up 11 months). On the other hand 9 patients had a tumor recurrence within the liver, 3 patients at extrahepatic regions and 7 patients developed a tumor recurrence within the freezing zone.

Colorectal Neoplasms↗
PubMed1998

Bone age determination based on the study of the medial extremity of the clavicle.

The development of the medial clavicular epiphysis and its fusion with the clavicular shaft have been a subject of medical research since the second decade of this century. Computed tomography provides the imaging modality of choice in analyzing the maturation process of the sternal end of the clavicle. In a retrospective study, we analyzed normal development in 380 individuals under the age of 30 years. The appearance of an epiphyseal ossification center occurred between ages 11 and 22 years. Partial union was found from age 16 until age 26 years. Complete union was first noted at age 22 years and in 100 % of the sample at age 27 years. Based on these data, age-related standardized age distributions and 95 % reference intervals were calculated. Compared to the experience recorded in the relevant literature, there are several landmarks that show no significant change between different ethnic groups and different periods of publication; these are the onset of ossification, the time span of partial union, and the appearance of complete union. Despite the relatively long time spans of the maturation stages, bone age estimation based on the study of the development of the medial clavicular epiphysis may be a useful tool in forensic age identification in living individuals, especially if the age of the subject is about the end of the second or the beginning of the third decade of life (e. g. in determining the applicability of adult or juvenile penal systems). Another possible use is in identifying human remains whose age is estimated at under 30 years.

Adolescent↗
PubMed1998

Hyperplastic callus formation in osteogenesis imperfecta: CT and MRI findings.

Hyperplastic callus formation is a noteworthy condition in patients with osteogenesis imperfecta because it often mimicks osteosarcoma on radiography. The findings of CT and MRI in hyperplastic callus formation have not been reported. In the presented case, MRI demonstrated contrast enhancement and edema of the surrounding soft tisssue, consistent with benign as well as malignant disease. Computed tomography showed a calcified rim of the lesion which may be a useful feature to rule out osteosarcoma in this condition.

Adult↗
PubMed1998

[Acute vascular perforation with shunt formation in the right ventricle after percutaneous transluminal coronary angioplasty. Magnetic resonance tomography and Doppler ultrasound detection of shunt flow].

A coronary artery perforation is a rare complication after percutaneous transluminal coronary angioplasty. The therapy will be determined by the hemodynamic failure of the left or right ventricle. A case of a coronary artery perforation with a shunt from the right coronary artery to the right ventricle after coronary angioplasty is reported. The shunt was detected by coronary angiography and confirmed by magnetic resonance imaging and doppler echocardiography.

Aged↗
PubMed1998

[MRI of knee ligaments: error analysis with reference to meniscus and anterior cruciate ligaments in an arthroscopic controlled patient cohort].

PURPOSE: To categorise discrepancies in findings of the menisci and anterior cruciate ligament (ACL) between arthroscopy and MRI. MATERIALS AND METHODS: The MRIs of 236 patients were retrospectively analysed by an experienced radiologist without knowledge of clinical and/or operative findings. Discrepancies in arthroscopic findings were reevaluated together with the arthroscopist to determine their cause of error. RESULTS: The diagnostic accuracies for injuries of the medial and lateral meniscus and the ACL were 92.4%, 92.4%, and 94.1%, respectively. For the menisci, causes for discrepancies in findings (n = 31) were: overinterpretation of central signal intensities with contact to the meniscal surface but without disturbance of the meniscal contour as a tear (n = 12), insufficient arthroscopie evaluation of the knee joint (n = 11), overlooked tears on MR imaging (n = 6), misinterpretation of normal anatomic structures (n = 1), "magic angle" phenomenon (n = 1), and missed tears at MRI (n = 1). Causes for discrepancies for the ACL (n = 18) were: nearly complete versus complete rupture either at MRI or arthroscopy and vice versa (n = 9), insufficient arthroscopic evaluation (n = 6), insufficient MRI technique (n = 2), and overlooked tear on MR imaging (n = 1). CONCLUSIONS: Discrepant findings between MRI and arthroscopy may be also due to an insufficient arthroscopic evaluation in clinical routine. The close cooperation between surgeons and radiologists improves the understanding of the methods of each other.

Adolescent↗