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Biomedical subjects

B Hamm

Publications and source records attributed to B Hamm.

At least 217 records · Page 12Linked to original sources
PubMed1991

Contrast material for computed tomography and magnetic resonance imaging of the gastrointestinal tract.

Various contrast agents are applied in both CT and MR imaging to improve the detection as well as the differentiation of focal liver lesions. In detecting hepatocellular carcinoma, the accuracy of Lipiodol-enhanced CT is comparable to that of CT during arterial portography. Tissue-specific contrast agents for the liver are superparamagnetic iron oxide particles, which are characterized by uptake in the reticuloendothelial system, and the paramagnetic hepatobiliary contrast agent manganese (II)-N,N'-dipyridoxylethylenediamine-N,N'-diacetate-5,5'-bis(phosphate). Both substances have the potential for markedly improving the detection of malignant liver tumors. The already good differentiation of focal hepatic lesions on plain MR images can be further improved by dynamic gadolinium diethylenetriamine penta-acetic acid-enhanced MR imaging. In the diagnosis of bile duct disorders, contrast-enhanced CT continues to be the method of choice. Water applied as a gastrointestinal contrast agent improves the staging of rectal carcinoma by CT. The development of suitable orally applied gastrointestinal contrast agents has now also improved the differentiation of the intestine from other abdominal structures on MR images, and this will lead to a general improvement of abdominal MR imaging.

Contrast Media↗
PubMed1990

Intracranial meningiomas. Comparison of plain and contrast-enhanced examinations in CT and MRI.

Fifty patients with intracranial meningiomas underwent plain and contrast-enhanced examinations with CT and MRI. Each of the MR studies consisted of three plain (T1, proton density and T2-weighted) and a post-contrast series (0.1 mmol Gd-DTPA/kg body weight). All techniques (plain CT, plain MRI, contrast-enhanced CT, contrast-enhanced MRI) proved to be highly efficient as regards tumour detection: depending on the technique, an intracranial lesion was demonstrated in 47-50 cases. The image contrast was assessed as good or excellent in 21 cases having plain CT and in 33 cases having plain MRI, but in 46 and 50 of the contrast-enhanced CT and MRI studies respectively. Adequate tumour delineation was achieved in 18 cases with plain CT, in 35 cases with plain MRI and in 46 and 50 cases of the contrast-enhanced CT and MRI examinations. The contrast-enhanced studies proved to be superior to the plain CT and MRI studies as regards image contrast and tumor delineation. Because of the methodological advantages of the MRI technique, contrast-enhanced MRI was judged to be slightly superior to contrast-enhanced CT.

Adult↗
PubMed1990

Differentiation of Trypanosoma brucei bloodstream trypomastigotes from long slender to short stumpy-like forms in axenic culture.

An axenic cultivation system was used to study the differentiation of Trypanosoma brucei bloodstream forms from long slender to short stumpy-like forms. Trypanosomes in the logarithmic phase are similar to long slender bloodstream forms freshly isolated from infected mice, differing only in the rate of oxygen uptake. In contrast, trypanosomes in the stationary phase show a decreased level of glucose oxidation, express pyrroline-5-carboxylate reductase (proline oxidase), are inhibited in oxygen uptake to about 44% by KCN, undergo considerable morphological changes on the cellular and subcellular level, and have a significantly smaller cell volume. These results are comparable to those observed during the differentiation of long slender to short stumpy forms in infected animals, suggesting that the differentiation process towards insect procyclic forms can be initiated in culture at 37 degrees C. As judged from immunofluorescence and electron microscopy analysis, the surface coat remains intact.

Animals↗
PubMed1990

[A semiquantitative assessment of aortic valve insufficiency by cine-MR compared to Doppler color echocardiography and cardioangiography].

A simple, reliable semiquantitative method for evaluating aortic valve insufficiency by means of cine MR is described. Ten normal persons and 36 patients with aortic valve abnormalities were examined in a 1.5 Tesla apparatus using ECG-triggered gradient echo sequences. The heart was imaged along its short axis. Semiquantitative evaluation of aortic valve insufficiency was calculated from an MRI index, which depends on the diameter of the aortic regurgitant jet and on its length; the results were compared with colour Doppler echocardiography and cardioangiography. The MRI index showed better correlation with cardioangiography (r = 0.92) than the correlation between the colour Doppler echocardiography and cardioangiography (r = 0.78). Over and under estimates are less common with MRI than with colour Doppler echocardiography. MRI showed very little interobserver variability (r = 0.96, p less than 0.001). Cine MR is a reliable method for demonstrating aortic valve insufficiency. Using the short axis of the heart, rapid semiquantitative evaluation of the aortic regurgitant jet is regularly possible.

Adult↗
PubMed1990

Contrast-enhanced magnetic resonance imaging of the abdomen and pelvis.

Contrast media in magnetic resonance imaging (MRI) of the abdomen and pelvis are applied for various purposes; different substances and forms of application must be distinguished. Oral contrast agents are primarily used to enhance the discrimination of the intestine from the other organs and from pathological lesions. Clinical studies of i.v. contrast agents focus on two substances: gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) and superparamagnetic iron oxide. Whereas dynamic Gd-DTPA-enhanced MRI improves the differential diagnosis of focal hepatic lesions, iron oxide is a promising agent for increasing the sensitivity of MRI in the detection of hepatic and splenic tumors. Dynamic Gd-DTPA-enhanced MRI of the kidney allows functional assessment of this organ; good demarcation of kidney tumors is only achieved during the early phase of a dynamic examination. In the assessment of adrenal lesions, dynamic Gd-DTPA-enhanced MRI permits better differentiation of adenoma from malignancy. Intravenous Gd-DTPA also appears to be useful in the staging of urinary bladder tumors to distinguish between superficial and infiltrating tumors. Although offering no major diagnostic advantage in the staging of cervical carcinomas, Gd-DTPA-enhanced MRI improves the discrimination of necrotic tumor portions of endometrial carcinoma and allows good differentiation of this lesion from fluid retained in the uterine cavity. Studies of new contrast agents for MRI of the abdomen, which have so far only been investigated in animal experiments, focus on liver imaging. These substance include hepatobiliary agents, Gd-DTPA-containing liposomes, and paramagnetic macromolecules.

Abdomen↗
PubMed1989

[Magnetic resonance tomography in the differential diagnosis of ovarian tumor and mucocele of the appendix].

Ultrasonography in a 73-year-old woman revealed two cystic structures in the region of the right adnexa. Magnetic resonance imaging suggested two morphologically distinct, space-occupying lesions, findings confirmed at operation and histological examination of the surgical specimen, which demonstrated a serous cystadenoma of the right ovary and a mucocele of the appendix.

Adnexa Uteri↗
PubMed1989

[Improvement of MR tomography of the liver using a multislice gradient echo sequence].

A prospective study of 52 patients with various focal liver lesions was carried out using a multislice-gradient echo sequence and this was compared with spin-echo sequences. The multislice-gradient echo sequence provides the possibility of obtaining heavily T1-weighted images of the entire liver during one examination, thereby reducing the time of the examination. Contrast is significantly better than that of a T1-weighted spin-echo sequence (p greater than 0.05). The multislice-gradient echo sequence examination, taking 5.4 minutes, provides good and diagnostically useful image quality.

Adult↗
PubMed1989

[Dynamic MR tomography of intrahepatic tumors].

By combining rapid imaging and bolus injections of the paramagnetic contrast medium gadolinium-DTPA, it is possible to perform dynamic MR imaging. The diagnostic value of dynamic MR imaging was investigated in 28 patients with focal liver lesions. Malignant tumours appear hypo-intense during the early phase of the dynamic study and are better distinguished from normal liver tissue. Haemangiomas produce a typical 'fill-in phenomenon' after contrast application and achieve very high signal intensity. Focal nodular hyperplasia is characterised by very rapid signal enhancement within the first minute after contrast injection. Dynamic MR imaging represents further improvement in the MR differentiation of liver tumours.

Adult↗
PubMed1989

[Improvement in the diagnosis of scrotal diseases using color-coded duplex sonography].

Two hundred and twenty-two patients with abnormalities of their scrotal contents were examined with colour-coded duplex sonography. The aim of this prospective study was to evaluate this new procedure for the investigation of the scrotal organs. Differentiation between testicular torsion and inflammation by colour-coded duplex sonography achieved 95% accuracy. The diagnosis of varicoceles was simplified and expedited (accuracy = 99%). In other abnormalities of the scrotum, particularly testicular tumours, a knowledge of the blood flow did not provide any important additional diagnostic information compared with conventional sonography.

Acute Disease↗
PubMed1989

[MR diagnosis of the liver].

By recent technical development magnetic resonance tomography has brought about essential improvements also for the diagnostics of the liver. For detecting focal lesions the diagnostic value of MRT is equal or superior to CT. For tumour screening at medium magnetic field strengths T1-weighted sequences with short repetition and echo times and multiple averaging of images are indicated. After detection of a pathologic tumourous condition a T2-weighted sequence allows the further differentiation of tissues. Hemangioma, the most frequent hepatic tumour, can be differentiated with high accuracy and non-invasively by MRT. Sonography will keep its place in screening, because of the high numbers of available devices and its low costs. Cystic lesions are better detected and the biliary ducts and be evaluated rapidly and at lower costs than with MR and CT. Gadolinium-DTPA as paramagnetic contrast medium is advised for demonstrating perfusion of hepatic tumours. Ferrites, small ferromagnetic iron particles, may open a new age of tumour screening.

Humans↗
PubMed1988

[Reactive benign thymus hyperplasia following cytostatic chemotherapy].

A space-occupying mediastinal mass was discovered in a 16-year-old boy with metastasizing non-seminomatous testicular tumour six months after successful conclusion of cytostatic chemotherapy. Metastases at other sites were excluded. An enlarged thymus was the only finding at operation. Histological and histochemical examination demonstrated diffuse hyperplasia. The findings demonstrate that reactive benign thymic hyperplasia after cytostatic chemotherapy has to be considered in the differential diagnosis of space-occupying mediastinal lesions. They can also occur in adults. They are benign, explainable as immunological rebound phenomena, and do not require operative intervention. In case of doubt, short-term corticoid administration will diminish the size of the mass and thus confirms the diagnosis.

Adolescent↗
PubMed1988

[Oral contrast media for magnetic resonance tomography of the abdomen. III. Initial patient research with gadolinium-DTPA].

32 patients with abdominal tumours or inflammatory abdominal diseases were examined by MRI (0.5 T) prior to and after oral administration of gadolinium-DTPA (Gd-DTPA). T1- and T2-weighted sequences were employed. 10 ml/kg body weight of a Gd-DTPA formulation were administered (1.0 mmol/l, 15 g mannitol/l). Gd-DTPA provided markedly hyperintensive opacification of the gastrointestinal tract. In 19 of 32 studies Gd-DTPA-enhanced scans showed improved delineation of abdominal pathologies. In most cases Gd-DTPA-enhanced T1-weighted multislice gradient echo images provided the most useful diagnostic result. Meteorism and diarrhea were recorded in 13 patients.

Abdomen↗
PubMed1988

[Magnetic resonance tomography of paranasal sinus tumors using gadolinium-DTPA and multi-echo sequences].

We report on the use of magnetic resonance tomography for tumours of the paranasal sinuses. The value of gadolinium-DTPA was investigated in a prospective study. For tissue characterisation and determination of the extent of the disease, combined use of T2-weighted multi-echo sequences and plain and contrast examinations with T1-weighted spin-echo sequences are superior to CT. CT must be used, however, to demonstrate bone changes. Endocranial tumour extension can be demonstrated more precisely with magnetic resonance than with CT.

Adult↗
PubMed1988

Testicular cysts: differentiation with US and clinical findings.

In 34 of 847 patients (4%), testicular cysts were discovered with high-resolution ultrasound (US). Sixteen had a cystic testicular tumor, and US images showed multiple cysts and solid tumor portions in 12 of these 16 (75%). Eighteen patients had nonneoplastic cysts: Five had cysts of the tunica albuginea, and 13 had intratesticular cysts. All tunica albuginea cysts were palpable as small masses, and only US images showed that the masses were cystic. None of the 13 intratesticular cysts was palpable; all were accidentally discovered with US, which showed that 12 were single cysts with a marginal location (92%). On histologic studies, the nonneoplastic cysts were related to the spermatic ducts (rete testis, efferent ductules) and frequently appeared as postinflammatory alterations. Only five patients with intratesticular cysts were followed up with US, and no changes occurred. The combination of clinical and US findings facilitated the differentiation between nonneoplastic and neoplastic testicular cysts.

Adolescent↗