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G Kölbel

Publications and source records attributed to G Kölbel.

15 recordsLinked to original sources
PubMed1989

[T2*-weighted MR images of gynecologic tumors with the FLASH sequence: the initial experiences at 1.5 T].

To speed up the time taken for MR examinations, 20 patients with malignant gynaecological lesions (carcinoma of the cervix, uterus or ovary) and two operative specimen (carcinoma of the cervix) were examined by T2*-weighted flash sequences; the results were compared with T2-weighted spin echo sequences. In ten out of 20 in vivo examinations, the flash method produced a similar contrast range between tumour and normal tissues, cystic lesions being particularly well seen in gradient echo sequences. In the remaining patients, and in the surgical specimen, demarcation of the tumour was significantly poorer on the flash sequences. There was also loss of anatomic detail and an increased susceptibility to artifacts. The flash sequence as used here can therefore not be regarded as of the same diagnostic value as T2-weighted spin echo sequences in the diagnosis of gynaecological malignancies.

Carcinoma↗
PubMed1988

[Parameter-weighted MR images and their optimization: theory and example of images for the flash sequence compared to the spin-echo sequence].

In this paper the signal intensity and parameter-weighting zones of spin echo and gradient echo sequences (FLASH) have been analysed. Using information available in the literature, with additional analytical and numerical techniques, it is possible to determine parameters which maximise tissue contrast for T1, T2 and proton-weighted images. The technique is equally applicable to spin echo and FLASH sequences. The advantages of optimised gradient echo sequences compared with spin echo sequences with respect to its signal to noise ratio for short repetition times are analysed quantitatively. T2-weighted images can be generated as rapid as T1-weighted images, using the FLASH sequences when using a small angle of spin and relatively long echo. Illustrations are shown to demonstrate the numerical results (field strength 1.5 tesla). This is followed by a discussion of possible opposing effects.

Humans↗
PubMed1988

[Reproducibility of the sonographic determination of the size of intra-abdominal space-occupying lesions].

The reproducibility of sonographic measurements was checked using 255 measurements on 57 intra-abdominal masses. It was shown that differences of measurements carried out independently by two observers increased in a linear manner with tumour diameter. Relative differences in measurement averaged 10%, but in 5% of cases they reached 30%. Somewhat better results were obtained with small tumours and for measurements lying strictly in the axis of the body. The significance of these findings in clinical practice, particularly for tumour follow-up, is discussed.

Abdominal Neoplasms↗
PubMed1988

Small arteries in peripheral lymph nodes: a specific US sign of lymphomatous involvement.

Fifty-seven patients with palpably enlarged peripheral lymph nodes underwent detailed ultrasonographic (US) examination with a 5.0-MHz and a 7.5-MHz probe. In 32 of 36 patients with malignant lymphoma (12 with Hodgkin disease, 24 with non-Hodgkin lymphoma) US showed a hypoechoic mass with a centrally located tubular structure. Pathologic examination showed that this structure correlated with small intact arterial vessels encased by confluent lymphomatous masses. This sonographic finding was not seen in patients with carcinomatous metastatic lesions to the lymph nodes (nine patients) or benign lymphadenitis (12 patients). The detection with US of small arteries within enlarged lymph nodes may indicate nodal infiltration by malignant lymphoma.

Arteries↗
PubMed1987

[Definitions of pulse sequences and parameter weightings in the NMR tomogram].

Due to the different possibilities of image creation in MR tomography there is no clear terminology of pulse sequences and MR images. This paper tries to define the designation of pulse sequence parameters in a practical way and to specify the term "parameter weighting of MR images". Starting with general definitions, special definitions for CNS and liver are elaborated.

Central Nervous System↗
PubMed1987

[The internal echo pattern of the normal pancreas. An assessment of the aging process and body weight dependence by sonographic gray-scale analysis].

Sonography of the pancreas was evaluated quantitatively in 94 normal subjects. The grey-scale values in the head and body of the pancreas were measured and compared with those of retroperitoneal fat. The echogenicity of the pancreas and the contrast between pancreas and fat were correlated with the age and weight of the subjects. Semi-quantitative studies revealed a positive correlation between echogenicity and age (r = 0.505); this can be confirmed to a high degree of statistical significance by quantitative analysis of pancreatic grey-scale values (r = 0.55 for the head and 0.71 for the body). Further improved correlation with age is obtained by computing the sonographic contrast between the pancreas and the retroperitoneal fat (r = 0.66 for the head and 0.77 for the body of the pancreas). It is concluded that determination of the grey-scale value can provide additional information particularly if one uses retroperitoneal fat as a reference tissue.

Adipose Tissue↗
PubMed1987

[Results of curative high-voltage irradiation of prostatic cancer].

The results of percutaneous irradiation of 111 patients with prostatic carcinomas during the years from 1974 through 1984 are retrospectively analyzed. A 8 MV X-radiation was applied in form of a moving field therapy charging the prostatic bed with a dose of 67.5 Gy in the 90% isodose enclosing the tumor; the regional lymph nodes were exposed to a total dose of 40 to 50 Gy. CT irradiation planning was used since 1976. All patients showing metastases received endocrine treatment or a cytostatic therapy. The corrected probability of a 10 year survival is 88% for a collective of carcinomas mainly limited to the capsula. Local recurrences were found in 2.7% and local recurrences accompanied by formation of metastases in 5.4% of cases. 12% of the patients showed chronic radiogenic side effects. The influence exerted on the survival curves by tumor stage, histological grade as well as other prognostic factors is discussed.

Aged↗
PubMed1986

[1.5 Tesla nuclear magnetic resonance tomographic studies of bladder cancer].

MR tomography was performed in 15 patients with urologically prediagnosed carcinoma of the urinary bladder. A field strength of 1.5 Tesla yields excellent morphological resolution of site and contrast. The results are compared with CT and--wherever available--with the pathological anatomic preparations. MR is often superior to x-ray computed tomography in demonstrating polypous carcinomas of the bladder and those producing thickening of the wall, since MR offers the possibility of performing coronary and sagittal cuts. In individual cases, MR can supply definite information on the depth of infiltration into the bladder wall and into perivesical structures; such findings agree with those obtained with cystectomy preparations. The contrast behaviour of the tumours and adjacent structures depends strongly on the measurement parameters employed with the high-strength field technique of 1.5 Tesla used in this study. MR echo sequences using different measurement parameters are useful in delineating the tumour contours against adjacent structures such as prostate, seminal vesicles, perivesical fat, urine and to differentiate the tumour from the healthy bladder wall.

Humans↗
PubMed1986

[Subjective evaluation and quantitative gray-scale analysis in the sonographic diagnosis of diffuse changes in the liver parenchyma].

Two investigators were asked to evaluate independently the echogenicity, coarsening and inhomogeneity of the hepatic echo pattern in a semi-quantitative manner; they had no knowledge of the diagnosis and used the same apparatus. The three subjective criteria were largely independent from the observer. Approximately three-quarters of all patients with slightly increased echogenicity showed a subjective appearance of coarsening; the impression of inhomogeneity increased significantly with increasing echogenicity. This is of importance in the sonographic evaluation of cirrhosis of the liver and in the diagnosis of diffuse liver metastases in a fatty liver. Grey scale analysis within a region of interest showed satisfactory correlation between the measured mean grey scale and echogenicity. Standard deviation within the grey scale was redundant, and there was no correlation between the other subjective characteristics and quantitatively measurable values.

Fatty Liver↗
PubMed1986

[Computed tomographic localization of the uterus for optimization of primary combined radiotherapy of inoperable cervix cancer].

The authors present the technique of CT reconstruction of the shape of the uterus in topograms of the pelvic region. The treatment scheme of combined endocavitary and percutaneous radiotherapy of uterine cervix carcinomas can be improved by means of the described method. The reliability of this method is compared to that of radiotherapy planning based on measuring radiography. Modifications of the position of the uterus obtained by endocavitary inserts proved to be relevant if the endocavitary regions exposed to high doses are left out from percutaneous therapy.

Brachytherapy↗
PubMedDate not supplied

Selective chemical imaging with a three-dimensional gradient echo sequence.

A combination of frequency selective excitation and saturation is used to separated water and fat components in magnetic resonance imaging. In conjunction with a gradient echo sequence (fast low angle) shot and a three-dimensional data acquisition, a large volume of the body can be covered. A set of 32 water or fat images can be obtained within 3.5 min using a repetition time of 50 ms and a 256 x 256 half Fourier space matrix. As no correction data or additional image calculations are necessary, the method can easily be applied to routine examinations.

Humans↗
PubMedDate not supplied

Dynamic sequential MR imaging of focal liver lesions: initial experience in 22 patients at 1.5 T.

The feasibility of dynamic sequential magnetic resonance (MR) imaging of focal hepatic lesions using Gd-diethylenetriamine pentaacetic acid (DTPA) was evaluated in this study. Three patients with hepatocellular carcinoma, 12 patients with metastases, and 7 patients with hemangiomas were studied with pre- and postcontrast multislice spin echo (SE) images using a repetition time of 500 ms and an echo time of 15 ms. The dynamic distribution phase of Gd-DTPA (0.1 mmol/kg) was investigated by using a sequential, transverse partial flip imaging sequence [fast low angle shot (FLASH)] before and after intravenous administration of Gd-DTPA. The lesion-liver contrast-to-noise ratio showed a great variability in patients with metastases and was significantly improved following administration of Gd-DTPA in patients with hemangiomas, two patients with hepatocellular carcinoma, and eight patients with metastases both on FLASH and SE images. Hemangiomas appeared darker than liver parenchyma on precontrast SE and FLASH images, increasingly enhanced over 5 min postinjection (pi) on FLASH images, and were still greatly enhanced at 10 min pi on SE images. During the dynamic sequential image acquisition the contrast enhancement of hemangiomas was significantly different from the enhancement observed in malignant lesions. The results of this study indicate the clinical potential of dynamic sequential imaging for the MR assessment of focal hepatic lesions.

Carcinoma, Hepatocellular↗