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K Lehner

Publications and source records attributed to K Lehner.

At least 19 recordsLinked to original sources
PubMed1996

[Spiral CT angiography: computed improvement of the slice thickness profile].

It is possible to improve on the low skirt selectivity of the slice sensitivity profile (SSP) in spiral CT by interpolation of the raw data or suitable image after-processing. We determined the SSP function of spiral CT by means of a plexiglas phantom which we subsequently modified empirically-mathematically by a correction function until we obtained maximum possible skirt selectivity and smallest possible FWHM (= full width at half maximum) of the corrected image data set. The corrected image data set was obtained by bilateral convolution of a real image data set with a correction function. This resulted in most cases in a more realistic imaging of the angiographic morphology when applied to SSD and MIP (3D) reconstructions of a. mesenterica sup. and tr. coeliacus from spiral CT data sets, compared with the original data sets.

Celiac Artery↗
PubMed1995

[MRI of the knee joint: first results of a comparison of 0,2-T specialized system and 1,5-T high field strength magnet].

PURPOSE: Diagnostic accuracy and image quality of a specialised system for MR examinations of peripheral joints were evaluated. MATERIALS AND METHODS: 20 patients with acute or chronic injuries of the knee were examined using a low-field MR system (0.2 T). For comparison, all patients were also studied with a 1.5 T high field strength magnet and all diagnoses were correlated with arthroscopic findings. RESULTS: We found compatible diagnostic accuracies (cruciate ligaments 90%, menisci 75-90%) and good image quality ratings for the low field system ("good" and "excellent" image quality in 83% of cases). CONCLUSION: The low-field MR-system offers low-cost MR examinations of peripheral joints with good image quality and reliable diagnostic information.

Adult↗
PubMed1993

[The MRT criteria for the differentiation of "pseudotumorous" lesions from bone sarcomas of the extremities].

The MRT scans of 57 patients with Ewing or osteosarcomas and 34 patients with haematogenous osteomyelitis or periostitis/stress fractures were examined in order to determine whether a distinction between benign or malignant lesions is possible. Four criteria were evaluated: the margin of the bone marrow component; intensity and homogeneity of the T1 weighted signal in the bone marrow; presence of an extraosseous structured soft tissue mass and/or soft tissue edema. It was found that central osteosarcomas and Ewing's sarcomas reduced signal intensity of the marrow to become muscle-isointense with a well-defined margin. In acute haematogenous osteomyelitis and periostitis/stress fracture the marrow lesion was not sharply demarcated. In contrast to patients with bone sarcomas, only one case of osteomyelitis showed an extraosseous structured soft tissue mass. On the basis of these findings we believe that acute haematogenous osteomyelitis can be distinguished with high degree of accuracy from Ewing's sarcoma and central osteosarcomas.

Adolescent↗
PubMed1993

[A comparison of plain film, axial CT, 2D and 3D reconstructions in unstable spinal injuries following surgery].

During a period of 18 months about 70 patients suffering from an unstable spinal injury were operated in the surgical department of our clinic. In 50 of these patients it was possible to correlate the results of preoperative radiography and CT with the operative findings. Several cases of distraction instability in the dorsal column had not been recognised in the preoperative radiologic evaluation. Therefore the rationale of this study was the question as to whether modern CT technology can help to avoid such wrong diagnoses. For that purpose radiographs, axial CT-scans of 2 mm thickness or less, sagittal and coronal 2D and (in 35 cases) 3D reconstructions were re-evaluated step by step by a specifically trained radiologist without knowing the operative findings. 15 additional lesions out of 28 were demonstrated and specifically classified as distraction instabilities of the dorsal column using the improved CT technology.

Adult↗
PubMed1993

Intravascular ultrasound in tumor staging.

Our preliminary results show that intravascular ultrasound scanning yielded the correct diagnosis in each patient who underwent surgery. We therefore conclude that this method is a potent adjunct to diagnostic procedures in pretherapeutic tumor staging when applied directly to the questionable region of the vessels. In contrast, evaluation of suspected tumor infiltration of the portal vein by positioning the catheter in the inferior vena cava or aorta was generally impossible due to technical problems. We hope that these problems will be solved as technology progresses.

Adult↗
PubMed1993

[Importance of ultrasound in postoperative follow-up after reconstruction of the anterior cruciate ligament].

Eighty-eight male patients following reconstruction of the anterior cruciate ligament (ACL; mean 24 months since operation) had a thorough clinical examination including instrumented measurement of laxity using the KT 1000. These results were correlated with an ultrasound (US) grading that evaluates the reconstruction itself as well as its functional behaviour during the anterior drawer test. Thirty-four magnetic resonance (MR) studies of 33 patients were available. Undoubtedly postoperative visualization of the reconstructed ACL is superior to that of both normal control ACL and acute trauma cases. Especially operative procedures which use the patellar or semitendinosus tendon lend themselves to accurate evaluation of the intraarticular reconstruction. The sensitivity, specificity, positive and negative predictive values and overall accuracy of US/MR versus the clinical laxity measurement are calculated to be 66.7%/96.0%, 71.2%%/23.8%, 59.5%/60.0%, 77.1%/83.3% and 69.4%/63.0% respectively. US has a satisfactory diagnostic value and performs similarly well on all these parameters. MR, on the other hand, correctly diagnoses nearly all unstable knees but is associated with a high number of false positives. There is no statistically significant, linear correlation between MR and US; r = -0.0769, P = 0.6706. Only three times did the reconstructed ACL appear normal on MR, whereas 48.5% of the reconstructions were graded type I (normal) on US. Clinical Consequences: Ultrasound and MRT should not be considered rival but rather complementary methods: ultrasound is a good method for documenting changes within the knee joint on an outpatient basis, while the indications for MR in the postoperative course are any occurrences of pain, instability or reinjury.

Adult↗
PubMed1992

[Intravascular ultrasound (IVUS): the assessment of tumor infiltration into the vascular wall].

The demonstration or exclusion of tumour infiltration into a vessel wall is made possible by IVUS. This was performed 25 times in 23 patients using a 20 MHz probe where there was suspicion of tumour infiltration on the basis of CT, MRI or angiography. IVUS proved very suitable for clarifying the situation, making direct intravascular evaluation of the affected vessel possible. In 10 cases where surgery was performed, the demonstration or exclusion of tumour infiltration into a vein was confirmed operatively in every case. Further experience is necessary before the value of the method for diagnosing early arterial infiltration can be judged.

Adult↗
PubMed1992

[Computed tomographic assessment of breathing-induced "pseudo" pneumoperitoneum].

The differentiation between a "pseudo" pneumoperitoneum and a pneumoperitoneum due to a perforation may be difficult in unconscious or ventilated patients. The use of CT for differentiating between extraperitoneal and intraperitoneal air is demonstrated by three examples in whom air below the diaphragm was shown by conventional radiographs. CT can prove the extraperitoneal position of an air crescent below the diaphragm in cases of "pseudo" pneumoperitoneum. CT will also show that extraperitoneal air does not rise in the way that true peritoneal air will do when the patient is supine. In this position the viscera therefore do not fall backwards in the presence of a "pseudo" pneumoperitoneum.

Adult↗
PubMed1991

[The diagnostic accuracy of MRT in cruciate ligament injuries].

Lesions of the anterior cruciate ligaments may be demonstrated by MRI with an accuracy of 99%. Standardised technique with sagittal and coronal projections produces excellent results. Localisation of the site of rupture can be achieved in 95% of cases. MRI provides a valuable method for diagnosing lesions of the cruciate ligaments.

Adolescent↗
PubMed1991

[Magnetic resonance tomography in the assessment of anterior cruciate ligament reconstruction by tendon grafts].

150 patients were examined via magnetic resonance (MR) after anterior cruciate (ACL) ligament reconstruction (76 patellar tendon grafts, 53 semitendinous tendon grafts and 21 sutures). The results of MR were compared with clinical tests (Lachman, pivot-shift and anterior drawer test), in 2 cases with the operative findings, and in one case with arthroscopy findings. In 91% of patients with a clinically stable knee we found a continuous low-intensity ligamental structure. 10 patients were examined twice or more between 8 days and 6 months after surgery. Ligamental structures of low signal intensity did not significantly change their MR characteristics. MR is a valuable noninvasive method for evaluating ligament reconstructions.

Adult↗