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F D Knollmann

Publications and source records attributed to F D Knollmann.

At least 37 records · Page 2Linked to original sources
PubMed1997

Abdominal CT features and survival in acquired immunodeficiency.

PURPOSE: HIV-infected patients show a high incidence of abdominal disease. This investigation was made to determine whether abdominal CT provided prognostically relevant information in these patients. MATERIAL AND METHODS: Images from 533 abdominal CT examinations in 339 HIV-infected patients were retrospectively reviewed for signs of abdominal disease, and correlated with clinical data and survival rates. The Kaplan-Meier analysis and rank testing of survival, and proportional hazards regression were used to define prognostic clinical and imaging findings. RESULTS: Of the 339 patients, 278 (82%) showed abnormal abdominal findings on CT. Median survival was 29 months. Of the imaging findings, hepatic masses (n = 11), pathologically enlarged lymph nodes (n = 48), and ascites (n = 7) were associated with poor survival, giving a median survival of respectively 13 months, 15 months, and less than 1 month. These three features showed no association with CD4(+)-T-lymphocyte count or CDC category. Main determinants of survival were a low CD4(+)-T-lymphocyte count, and certain abnormal CT findings. Splenomegaly (n = 147), hepatomegaly (n = 144), and lymphadenopathy (n = 111) were the most common abdominal findings on CT but lacked prognostic relevance. CONCLUSION: Abdominal CT offered prognostic implications in HIV-infected patients and might serve in risk stratification in selected patients. CT features such as hepatic masses, grossly enlarged lymph nodes, or ascites indicate advanced immunosuppression.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Hemodynamic tolerance of intravascular contrast agents for magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Intravascular contrast agents for magnetic resonance imaging (MRI) facilitate the quantification of tissue perfusion. The authors determined the hemodynamic tolerance of these agents. METHODS: Doses of 0.05, 0.15, and 0.45 mmol/kg of the polymeric intravascular contrast agent gadolinium-DTPA-polylysine, and di-nitrobenzyl-gadolinium-DTPA, a non-polymeric intravascular contrast agent with high protein binding, and gadolinium-DTPA dimeglumine, a paramagnetic contrast agent with extracellular distribution, were injected into 18 normal male rats as a peripheral intravenous bolus. Systolic, diastolic, and mean blood pressure, left ventricular end-diastolic and developed pressure, positive rate of pressure change (+dP/dt), dP/dt, the rate-pressure product, and heart rate were recorded during a period of 20 minutes. Hemodynamic effects were established by analysis of variance for repeated measurements. RESULTS: There was a transient increase of all blood pressure parameters and contractility for Gd-DTPA-polylysine at the dose of 0.45 mmol/kg only. Di-nitrobenzyl-Gd-DTPA increased blood pressure parameters at 0.45 mmol/kg only. At doses of 0.05 and 0.15 mmol/kg, no significant hemodynamic effects were observed. CONCLUSIONS: The authors conclude that Gd-DTPA-polylysine is hemodynamically safe at doses to 0.15 mmol/kg and acts like a plasma expander at higher doses after peripheral bolus injection in normal rats. Additional investigations are indicated to elucidate the mechanism of a nonsignificant and satiable transient hemodynamic depression after injection of 0.05 mmol/kg DNB-Gd-DTPA.

Animals↗
PubMed1996

In vitro delineation of human brain-stem anatomy using a small resonator: correlation with macroscopic and histological findings.

Our purpose was to investigate the potential of an experimental animal coil using a commercial MRI unit to delineate the anatomical structure of the human brain stem. Three formaldehyde-fixed brain-stem specimens were examined by MRI and sectioned perpendicular to their longitudinal axis. The images were compared with gross anatomy and myelin-stained histological sections. Fibre tracts and nuclei which were not evident on examination of the unstained specimen were readily identified by MRI. Due to its inherent grey/white matter contrast, MRI with a high-resolution coil delineates anatomical structures in a way comparable to the myelin-stained histological sections. However, pigmented structures, readily visible on examination of the unstained specimen were discernible on neither MRI nor on myelin-stained sections. The excellent anatomical detail and grey/white matter contrast provided by these images could make MRI a useful adjunct to the pathologist investigating brain disease.

Brain Stem↗
PubMed1996

Cardiac activation mapping by MRI.

To establish cardiac MRI as a tool for noninvasive evaluation of activation patterns, 10 healthy volunteers were examined by cine segmented turboFLASH imaging sequences. Sequence modifications for low signal blood-pool appearance were applied, i.e., bilateral spatial saturation for segmented turboFLASH imaging. Pixelwise calculation of first-harmonic Fourier phase values (displayed as color-encoded maps) reveal either anterior septal or left ventricular free-wall sites as areas of earliest phase spreading towards posterior paraseptal sites in segmented turboFLASH scans. Phase scatter is lower in unsaturated than spatially presaturated segmented turboFLASH studies. Phase standard deviation in areas of endocardial displacement is higher in basal than apical slice positions in these scans. Early results indicate that first-harmonic Fourier phase analysis of cardiac-segmented turboFLASH MRI cine studies may provide a tool for noninvasive studies of cardiac activation sequence.

Adult↗
PubMed1996

Applications of specialized coils for high-resolution MRI on a whole-body scanner.

To investigate the application of a mini-coil surface system for high-resolution MRI, 60 volunteers were examined in a 1.5-T whole-body scanner. Two replaceable probe heads were available: a circular 2.5-cm coil and a quadratic 5-cm coil, both of which were placed directly on the skin. The skin layers, Achilles tendon and finger joints were examined with the 2.5-cm coil and a FOV of 25 X 25 mm2. A matrix of 256 pixels resulted in a pixel size of 0.098 X 0.098 mm2. For imaging of the carpal tunnel, the 5-cm coil was used in transverse orientation. The FOV was 50 X 50 mm2 so that a matrix of 256 X 256 pixels led to a pixel size of 0.195 X 0.195 mm2. The resulting spatial resolution permitted visualization of the epidermis, dermis and subcutis, resulting in clear definition of anatomical detail of the musculoskeletal system. MRI measurement of skin-layer thickness did not correlate with histometric data (p < 0.05). This discrepancy was due in part to shrinkage of the tumor specimen on histologic preparation. Other causes include the motion artifacts and the limited accuracy of determining thickness on the MRI display unit.

Achilles Tendon↗
PubMed1996

Failure of gadopentetate dimeglumine-enhanced, high-resolution magnetic resonance imaging to differentiate among melanin-containing skin tumors.

RATIONALE AND OBJECTIVES: We evaluated the diagnostic potential of gadopentetate dimeglumine-enhanced, high-resolution magnetic resonance (MR) imaging to differentiate benign from malignant melanin-containing skin tumors. METHODS: Forty-five patients were prospectively examined using high-resolution MR imaging at 1.5 T using a 2.5-cm surface coil. For tumor assessment, T1-weighted and T2-weighted transverse spin-echo sequences were acquired. After intravenous administration of gadopentetate dimeglumine (0.1 mmol/kg), the T1-weighted transverse sequence was repeated. Contrast enhancement was quantitatively determined as the percentage increase of signal intensity. Histologic findings were correlated using the Wilcoxon signed-ranks test. The quality of contrast enhancement was assessed by three independent investigators who were unaware of the patients' history and histologic data. The signal-to-noise ratio (SNR) was calculated in the T2-weighted sequence. Significance was tested using the Wilcoxon signed-ranks test. RESULTS: In all tumors, contrast enhancement was visually discernible. Half of the cases were enhanced inhomogeneously. The percentage of contrast enhancement did not correlate with histologic findings. Malignant melanomas could not be differentiated from benign melanocytic nevi with the use of gadopentetate dimeglumine. Determination of the SNR in T2-weighted sequences revealed no significant difference for histologic subgroups or tumor type. CONCLUSION: Gadopentetate dimeglumine-enhanced MR imaging does not differentiate malignant melanomas from benign melanocytic nevi. Determination of the SNR in the T2-weighted sequences revealed no significant difference for histologic subgroups.

Adolescent↗
PubMed1996

Keratinization and necrosis. Morphologic aspects of lymphatic metastases in ultrasound.

RATIONALE AND OBJECTIVE: The authors performed a retrospective study in ultrasound to investigate new aspects in the sonomorphology of lymph node metastases of the neck. In this study, it could be demonstrated the first time that the histologic characteristics of the metastases determine the sonographic appearance. In addition to criteria such as the longitudinal/ transversal quotient, sonomorphology could support a more precise differential diagnosis of neck lymph nodes. METHODS: In 105 of 145 patients with histologically proved head and neck carcinomas, 187 lymph node metastases were detected by ultrasound. Sonomorphology was compared with the corresponding histology. RESULTS: Five sonomorphologic groups could be differentiated. (1) Thirty-one percent of the metastases were homogenous. (2) Concerning the more complex morphology of lymph node metastases in ultrasound, echolucent forms could be differentiated from echogenic textures: low- or nondifferentiated and nonkeratinizing metastases appeared echolucent and cyst-like, with dorsal signal amplification. (3) Nonkeratinizing lymphomas with necrosis showed single or multiple echolucent intranodal lesions. (4) In correlation with an increasing keratinization, the echogenecity of the lymph nodes increased and intranodal echogenic inclusions appeared. (5) An extended keratinization correlated with a central echogenecity. CONCLUSIONS: The morphologic assessment of lymph nodes in ultrasound allows for primary histologic and prognostic evaluation of lymph node metastases.

Aged↗
PubMed1996

Fourier phase mapping of the human heart. The use of spatial modulation of magnetization cine magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Fourier phase mapping of cine cardiac magnetic resonance (MR) imaging offers noninvasive analysis of temporal cardiac activation patterns. The aim of our investigation was to extend this analysis to intramyocardial dynamics. METHODS: A fast-imaging with steady-state precision (FISP) two-dimensional gradient echo spatial modulation of magnetization (SPAMM) sequence and a segmented two-dimensional FISP-SPAMM sequence were applied to acquire cine MR images of the complete cardiac cycle on a 1.5-tesla imager. Signal intensity data were submitted to pixel-wise Fourier phase analysis. Color-encoded amplitude and phase maps were displayed for visual analysis. RESULTS: Using the unsegmented SPAMM two-dimensional FISP sequence, a more consistent tag-to-myocardium contrast and a higher number of cardiac phases was achieved than by using the segmented version of this sequence. The typical tag displacement reflected complex intramyocardial dynamics, including rotation. Phase mapping displayed a pattern of contraction consistent with electrophysiologic concepts of cardiac activation. In contrast, the segmented sequence did not reflect any differences in the onset of cardiac contraction, although tag displacement was apparent with this sequence as well. CONCLUSIONS. Fourier phase mapping of cardiac MR imaging tagging studies allows for noninvasive analysis of intramyocardial activation patterns. A temporal resolution of 50 mseconds per image at a heart rate of 75 beats per minute allows for an assessment of spatial differences in the onset of myocardial activation.

Adult↗
PubMed1996

[Theoretical principles and technical realization of high resolution nuclear magnetic resonance tomography with the example of a dedicated coil system].

The theory of high-resolution magnetic resonance imaging (MRI) and the physical properties of a dedicated coil system with its clinical application are reviewed. To evaluate the spatial resolution of the system, a phantom sample was depicted by a transverse T1-weighted sequence (time of repetition 500 ms, time of echo 25 ms, 256 x 256 matrix, 3 acquisitions, field of view 25 mm2). Relative signal intensity decrease was less using the 5-cm coil, as signal intensity field distribution depends on coil diameter. The phantom appeared as an attainable resolution of 100-microns pixel width using the 2.5-cm coil. For the 5-cm coil the pixel width was 200 microns, not accomplishing clear resolution of the phantom. Coil head choice depends on the anatomic depth of the target organ. Work-up of the skin and musculoskeletal lesions is the main indication for high-resolution MRI using surface coils.

Achilles Tendon↗
PubMed1996

[Contrast medium behavior of epithelial skin tumors and tumor-like changes in high resolution magnetic resonance tomography].

To evaluate the use of Gd-DTPA in imaging epithelial skin tumors and tumor-like lesions, 29 benign, 8 malignant and 4 semimalignant skin tumors were prospectively examined by high-resolution MRI at 1.5 Tesla using a 2.5-cm surface coil. For tumor assessment, transverse plain and contrast-enhanced scans (0.1 mmol Gd-DTPA/kg body mass) were performed (TR 500 ms, TE 25 ms, 3 acquisitions, 256 x 256 matrix, FOV 2.5 cm). Contrast enhancement was quantitively determined as the percent enhancement of signal intensity. Histologic findings were correlated using the Mann-Whitney-test (p < 0.05). Quality of contrast enhancement was independently assessed by three investigators, who mostly described inhomogeneous enhancement, regardless of histologic findings. Malignant tumors could not be differentiated from benign lesions by contrast enhancement. MRI using Gd-DTPA does not provide differentiation of skin tumor types.

Adolescent↗
PubMed1995

Role of high-resolution magnetic resonance imaging for differentiating melanin-containing skin tumors.

RATIONALE AND OBJECTIVES: The aim of the study was to evaluate the use of high resolution magnetic resonance imaging (MRI) for differentiation of melanin-containing skin tumors. METHODS: Twenty-seven melanocytic nevi and 18 malignant melanomas were examined by high resolution MRI. Signal intensities and signal-to-noise (SNR) and contrast-to-noise ratios (CNR) of the tumors were determined in enhanced (T1, T2, water-suppression, and fat-suppression sequences) and contrast-enhanced images (T1 and fat-suppression sequences). The differences were tested for significance by a Wilcoxon test. RESULTS: Malignant melanomas differed from melanocytic nevi in that they displayed a higher SNR in T2-weight and unenhanced and contrast-enhanced fat-suppression scan. Malignant melanomas exhibited a higher CNR than did benign lesions in unenhanced and contrast-enhanced fat-suppression sequences with dermis as reference tissue (P < 0.05) and in enhanced fat-suppression sequences with subcutis as reference tissue (P < 0.05). CONCLUSIONS: The usefulness of SNR and CNR analysis on MRI for the differentiation of malignant skin tumors from benign skin tumors of the melanin-containing system is limited. Clinical and histologic examinations are, further, the important step in evaluation of melanin-containing skin tumors.

Adipose Tissue↗
PubMed1995

[Comparative imaging of HIV associated diseases of the hepatobiliary system in computerized tomography and cholangiography].

With the incidence of AIDS being on the rise, diagnostic work-up of hepatobiliary disease in these patients is of increasing interest. 57 x-ray cholangiograms and computed tomographic studies of 13 AIDS-patients with clinical signs of cholangitis were reviewed. Nine patients had abnormal cholangiographic findings. Computed tomography of 8 patients revealed hepatobiliary disease in six cases. Of three patients with cholangiograms reflecting bile duct dilatation of neoplastic aetiology, CT was required in two for definite diagnosis. Cholangiography is the method of choice for diagnosing AIDS-associated cholangitis, whereas computed tomography compares favourably in depicting neoplastic disease of the hepatobiliary system. Follow-up of AIDS-associated cholangitis usually delineates unchanged radiologic findings.

AIDS-Related Opportunistic Infections↗
PubMed1995

[Radioisomorphisms of sclerosing cholangitis].

For differentiation of Primary Sclerosing Cholangitis (PSC) from AIDS-associated cholangitis (AAC), 95 CT or Cholangiography studies of 37 patients were reviewed and signs of biliary disease analysed. Only two each of PSC and AIDS-subjects were free from biliary lesions compatible with some kind of sclerosing cholangitis. Subgroup analysis revealed wide overlapping of morphological findings in PSC and AAC. We conclude that radioisomorphism of etiologically different forms of sclerosing cholangitis may indicate pathophysiologically similar courses.

AIDS-Related Opportunistic Infections↗
PubMed1995

[Diagnostic results of abdominal computerized tomography in HIV-infected patients].

The exact frequency of pathologic findings in abdominal computed tomograms of HIV-infected patients is not yet known. To analyse such findings, CT scans of 339 HIV-infected patients were reviewed. While over four fifths of patients displayed abnormal findings; hepatosplenomegaly, lymphadenopathy, pathologically enlarged lymph nodes, and bowel wall thickening were the most common signs of disease. Only for enlarged lymph nodes could a dependency on clinical stage of the infection be demonstrated. As a conclusion, abdominal computed tomography reveals pathologic findings in the vast majority of HIV-infected patients, almost independent of clinical stage. Specifically, CT provides well documented lymph node staging. There are practically no age-or sex-dependent disease patterns in abdominal CT scans.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Evaluation of portal MR angiography using superparamagnetic iron oxide.

The purpose of our research was to determine the effects of superparamagnetic iron oxide on MR imaging of the portal venous system. Eight piglets were examined in deep anaesthesia and respiratory arrest using a time-of-flight magnetic resonance fast low angle shot, two-dimensional angiography sequence at 1.5T, MR angiograms were acquired precontrast and after intravenous administration of a cumulative dose of 10, 20 and 40 mumol/kg SHU 555A, a superparamagnetic iron oxide contrast agent for MR imaging with a particle size of 60 nm. For each dose, two subsequent sets of scans were obtained and reconstructed by a maximum-intensity-projection algorithm. Hepatic parenchymal and portal venous signal intensities were measured, and portal vein contrast calculated for each set of scans. All examinations were visually rated as to portal vein contrast and homogeneity by two blinded observers. Receiver operating characteristics of both observers were analyzed. The contrast agent reduced hepatic parenchymal signal in a dose-dependent way. After a cumulative dose of 10 mumol iron oxide, hepatic parenchymal signal intensity decreased to 63 +/- 6% (average of measurements at 4 and 14 minutes, mean +/- standard error of the mean), after 20 mumol to 24 +/- 3%, and after 40 mumol to 12 +/- 1% of control. Intravascular signal in the left main portal vein branch increased to 117 +/- 6%, 127 +/- 10%, and 133 +/- 9% of control, respectively. The contrast-to-noise ratio of the portal vein improved (521 +/- 90%, 891 +/- 178%, and 995 +/- 201% of control in the left portal vein main branch). Intravascular signal intensities increased slightly. The combined effect improved contrast of the portal vein stem and its branches. Receiver operating characteristics analysis documented dose-dependency of contrast medium effects on portal venous contrast and intravascular homogeneity. Visual rating also indicated a positive effect on portal venous contrast. The superparamagnetic iron oxide agent improved portal venous contrast with surrounding hepatic parenchyma in this normal animal model, and could potentially result in more accurate diagnosis of portal venous pathology.

Animals↗
PubMedDate not supplied

Use of semiflexible applicators for radiofrequency ablation of liver tumors.

PURPOSE: To evaluate the feasibility and potential advantages of the radiofrequency ablation of liver tumors using new MRI-compatible semiflexible applicators in a closed-bore high-field MRI scanner. METHODS: We treated 8 patients with 12 malignant liver tumors of different origin (5 colorectal carcinoma, 2 cholangiocellular carcinoma, 1 breast cancer) under MRI guidance. Radiofrequency ablation (RFA) was performed using 5 cm Rita Starburst Semi-Flex applicators (Rita Medical Systems, Milwaukee, WI, USA) which are suitable for MR- and CT-guided interventions and a 150 W RF generator. All interventions were performed in a closed-bore 1.5 T high-field MRI scanner for MRI-guided RFA using fast T1-weighted gradient echo sequences and T2-weighted ultra-turbo spin echo sequences. Control and follow-up MRI examinations were performed on the next day, at 6 weeks, and every 3 months after RFA. Control MRI were performed as double-contrast MRI examinations (enhancement with iron oxide and gadopentetate dimeglumine). All interventions were performed with the patient under local anesthesia and analgo-sedation. RESULTS: The mean diameter of the treated hepatic tumors was 2.4 cm (+/-0.6 cm, range 1.0-3.2 cm). The mean diameter of induced necrosis was 3.1 cm (+/-0.4 cm). We achieved complete ablation in all patients. Follow-up examinations over a duration of 7 months (+/-1.3 months, range 4-9 month) showed a local control rate of 100% in this group of patients. All interventions were performed without major complications; only 2 subcapsular hematomas were documented. CONCLUSION: RFA of liver tumors using semiflexible applicators in closed-bore 1.5 T scanner systems is feasible. These applicators might simplify the RFA of liver tumors under MRI control. The stiff distal part of the applicator facilitates its repositioning.

Aged↗