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Biomedical subjects

B Hamm

Publications and source records attributed to B Hamm.

At least 145 records · Page 8Linked to original sources
PubMed1997

Gadolinium-ethoxybenzyl-DTPA as a hepatobiliary contrast agent for use in MR cholangiography: results of an in vivo phase-I clinical evaluation.

The purpose of this study was to investigate the time course of contrast enhancement in bile ducts and the gallbladder (GB) after injection of gadolinium-ethoxybenzyl-DTPA (Gd-EOB-DTPA). In a clinical phase-I study, MR imaging at 1.5T was performed in 16 healthy volunteers with four different doses of Gd-EOB-DTPA (10, 25, 50, and 100 micro;mol/kg b. w., four volunteers per dosage). The study protocol comprised a heavily T1-weighted fast multiplanar gradient-echo (GE) sequence before and at increasing intervals for up to 360 min after injection of Gd-EOB-DTPA. The signal enhancement was evaluated in extra- and intrahepatic bile ducts as well as in the GB. In all 16 volunteers the common bile duct showed intense signal enhancement beginning 5-16 min after injection (mean 10 min) and persisting for at least 120 min in 4 subjects and for 360 min in 12 subjects. The duration of signal enhancement was significantly (p < 0.05) longer for higher doses (50, 100 micro;mol/kg) than for lower doses (10, 25 micro;mol/kg). Intrahepatic bile ducts were hyperintense as compared with liver parenchyma in all subjects receiving 10 micro;mol/kg from approximately 50-120 min after contrast agent application. Intrahepatic bile ducts were not displayed using the higher doses, probably because of the strong enhancement of the liver parenchyma. Gallbladder contrasting was achieved in all cases beginning 7-33 min after injection (mean 19 min) and remained visible for up to 360 min in 94 %. Hyperintense visualization of normal extrahepatic bile ducts as well as the GB is regularly achieved with the hepatobiliary contrast agent Gd-EOB-DTPA. The dosage for hyperintense visualization of intrahepatic bile ducts is 10 micromol/kg.

Adult↗
PubMed1997

Contrast agents for MR imaging of the liver: a clinical overview.

Different contrast agents have been clinically used in MR imaging of the liver including extracellular gadolinium chelates, contrast agents targeted to the macrophage-monocytic phagocytic system (MMPS), hepatobiliary contrast agents, and blood-pool contrast agents. Extracellular gadolinium chelates are optimally used for characterization of focal hepatic lesions, whereas hepatobiliary and MMPS-targeted contrast agents are optimally used for detection and preoperative evaluation. The present review portrays these contrast agents and discusses their advantages and shortcomings.

Contrast Media↗
PubMed1997

Hepatic magnetic resonance imaging: new techniques and contrast agents.

Magnetic resonance (MR) imaging is a relatively new method of examining the liver. Attempts have been made to optimize the method by developing new imaging techniques and introducing new contrast agents. The new imaging techniques have improved the image quality by shortening the examination time, reducing motion artifacts, and improving contrast-to-noise ratio. Contrast agents have improved the diagnosis of focal hepatic lesions in MR imaging in several ways. Extracellular gadolinium chelates have significantly improved the characterization of lesions, and can be optimally used as a problem-solving method for differentiating focal lesions of an unknown nature that have already been detected by other imaging modalities or by unenhanced MR imaging. Hepatobiliary and macrophage monocytic phagocytic system (MMPS)-targeted contrast agents have improved the detection of hepatic lesions. These agents are best used for preoperative evaluation of the exact number of lesions in patients with primary or secondary hepatic neoplasms.

Animals↗
PubMed1997

[Electron-beam tomographic imaging of the coronary arteries: an experimental comparison between monomeric and dimeric x-ray contrast media].

PURPOSE: Comparison of a monomeric and a dimeric radiographic contrast medium in the visualisation of the coronary arteries via electron beam tomography (EBT). MATERIAL AND METHODS: In a total of 6 Göttingen minipigs the heart was examined by EBT (40 sections, ECG-triggering, 1.5 mm section thickness, 100 ms acquisition time) after injection of both iopamidol (monomer, 370 mg l/ml) and iotrolan (dimer, 320 mg l/ml) at a dose of 740 mg l/kg. Injection rate and scan delay were adjusted to heart rate and circulation time. RESULTS: The intravascular increase in density after intravenous injection of iotrolan was significantly higher and longer than after injection of iopamidol (> 300 HE: 28 +/- 4 versus 17 +/- 5 cardiac cycles; p < 0.05). Iotrolan attained a higher score in the visualisation of the coronary arteries in three-dimensional surface reconstructions (p < 0.05). CONCLUSION: The dimeric contrast medium iotrolan proved superior to the monomeric agent iopamidol for visualisation of the coronary arteries via EBT.

Animals↗
PubMed1997

[Sacroiliitis: the key symptom of spondylathropathies. 1. The clinical aspects].

Seronegative and HLA B27-associated spondyloarthropathy (SpA) is a heterogeneous disease, so far without a clear origin. The term comprises five clinically defined subcategories: ankylosing spondylitis (AS), psoriatic arthritis (PsA), reactive arthritis (ReA), inflammatory bowel disease-associated arthritis and undifferentiated spondyloarthropathy (uSpA). Sacroiliitis, an inflammatory involvement of one or both sacroiliac joints, is the key symptom of all spondyloarthropathies. Sacroiliitis is often associated with inflammatory back pain, manifest as deep nocturnal back pain that is improved by exercise. The pathogenesis of SpA and the reason for the tropism for the sacroiliac joints is still obscure. A genetic background of an initially bacterial triggered infection seems to be most likely.

Diagnosis, Differential↗
PubMed1997

[Sacroiliitis:the key symptom of spondylarthropathies. 2: morphological aspects].

Because of their curved course and segmental convolution of articular surfaces, the anatomy of the sacroiliac joints is complex. An important part of the diagnosis of sacroiliitis of spondyloarthropathy patients relies on radiographic imaging techniques: x-ray, conventional tomography, computed tomography (CT) and scintigraphy. Diagnosis can be difficult in early and acute stages of sacroiliitis because radiographic findings may be normal, although dynamic magnetic resonance imaging (MRI) of the sacroiliac joints certainly enables to detect chronic as well as acute inflammatory changes. In spondyloarthropathy patients with acute sacroiliitis or acute exacerbation of chronic sacroiliitis who do not respond to or do not tolerate non-steroidal antiinflammatory drugs, CT-guided corticosteroid injection into the sacroiliac joints has proved to be an effective therapy.

Acute Disease↗
PubMed1997

[The revised WHO classification of brain tumors. Radiological aspects of 4 new tumor entities].

PURPOSE: Characterisation of the classification of brain tumours authorized by the WHO. METHOD OF APPRAISAL: This classification was revised and published in its second version. In the revision, some tumours were regrouped histogenetically and some tumour variants were added. Radiologically relevant changes of the classification include the differentiation of four new tumour entities that are easily distinguished by MR imaging. These four tumours belong to the group of childhood tumours or tumours occurring in early adulthood and are characterized by a good prognosis after extirpation. RESULTS OF APPRAISAL: Central neurocytomas are small-cyst ventricular tumours associated with the foramen of Monroi and show moderate contrast enhancement. Infantile desmoplastic gangliogliomas/astrocytomas commonly consist of a solid tumour portion related to the leptomeninges with pronounced contrast enhancement and a typically very large cyst. Pleomorphic xanthoastrocytomas are circumscribed cortical tumours and usually show very moderate gyriform enhancement with only slight signs of a mass effect. Dysembryoblastic neuroepithelial tumours, which originate in the cortical/ subcortical region, likewise show no mass effect; they are characterised by thickening of the cortex from surrounding dysplastic tissue and erosion of the calotte.

Adult↗
PubMed1997

Description and first clinical use of a new system for combined mammography and automated clinical amplitude/velocity reconstructive imaging breast sonography.

RATIONALE AND OBJECTIVES: The authors tested a new automated system for clinical amplitude/velocity reconstructive imaging (CARI) breast sonography and compared the results with those of a manual laboratory model of this imaging modality, conventional sonography, and mammography. METHODS: Fifty-one patients with breast lesions were examined by mammography, conventional breast sonography, a laboratory version of a mammography-like breast compression device for breast sonography, and an automated system that allows sonography while in compression and reconstructs an image of the whole breast. The automated device allows reconstruction of one image per breast from an automatically acquired sonographic data set and simultaneous performance of mammography. The results of mammography and all modes of sonography were compared with histopathology in 36 surgically treated lesions of which 20 were benign and 16 malignant. In addition, 17 lesions confirmed to be benign by different imaging modalities were examined with the three different sonographic devices. RESULTS: All 16 histopathologically proven malignant lesions were identified correctly by compression sonography (laboratory and automated device) compared with 14 by conventional sonography. Of the 20 benign lesions, 16 were interpreted correctly by conventional sonography, 19 with the laboratory version, and 18 with the automated device, whereas mammography identified 12 benign lesions correctly and missed 1 malignant lesion. Only 16 of 17 lesions diagnosed to be benign by outpatient imaging could be examined with all three modes of study sonography and were found to be benign with all three modes in all cases. CONCLUSIONS: Compared with the laboratory version, the automated device facilitates acquisition and evaluation of compression breast sonography and is similar in lesion detection and differentiation. It should be tested in a larger number of patients.

Adult↗
PubMed1997

Comparison of angiography, CT arteriography and MR imaging in assessment of liver metastases treated by percutaneous transcatheter intraarterial chemotherapy.

The purpose of this study was to compare results of digital subtraction angiography (DSA), computed tomographic arteriography (CTA), and magnetic resonance imaging (MRI) in the assessment of patients with liver metastases subjected to percutaneous transcatheter intraarterial chemotherapy. Forty-four patients with liver metastases treated by cyclic percutaneous transcatheter intra-arterial chemotherapy were examined before each cycle by an imaging protocol consisting of DSA and CTA. MRI was added to this protocol in 18 patients. DSA and CTA equally detected thrombosis of the catheter or arteries distal to the catheter tip in 16 examinations. DSA detected arterial reflux in 15 examinations, while CTA detected only one case of reflux. CTA was superior to DSA in demonstrating perfusion abnormalities and superior to MRI in detecting metastases. CT was the only method that demonstrated intratumoral calcification. In conclusion, in patients with liver metastases subjected to percutaneous transcatheter intra-arterial chemotherapy, DSA is the best method for detection of arterial reflux, whereas CTA is the best method for detection of metastases and demonstration of perfusion abnormalities.

Adult↗
PubMed1997

Liver metastases: improved detection with dynamic gadolinium-enhanced MR imaging?

PURPOSE: To compare dynamic gadolinium-enhanced with unenhanced magnetic resonance (MR) imaging in detection of liver metastases. MATERIALS AND METHODS: Two groups of patients were prospectively examined with unenhanced and dynamic gadolinium-enhanced MR imaging. The first group (n = 48) had proved liver metastases; the second group (n = 49) did not. One set of unenhanced and one set of gadolinium-enhanced MR images were selected per patient. Three independent, blinded readers assessed the images for presence, number, location, and conspicuity of lesions. Data were analyzed with receiver operating characteristic curves, and contrast-to-noise ratios were calculated for the images. RESULTS: There was no statistically significant difference between the use of unenhanced and gadolinium-enhanced MR images in the differentiation of patients with from patients without metastases. The numbers of false-positive and false-negative diagnoses of individual lesions were higher (not statistically significant) with dynamic MR images than with unenhanced MR images. At dynamic MR imaging, contrast-to-noise ratio was highest in the early phase (30 seconds after injection of the contrast agent) but was not significantly different from the contrast-to noise ratio of the T2-weighted images. CONCLUSION: Dynamic gadolinium-enhanced MR imaging showed no improvement over unenhanced MR imaging in detectability of liver metastases.

Adult↗
PubMed1997

Peripheral washout sign on contrast-enhanced MR images of the breast.

PURPOSE: To assess the value of the peripheral washout sign on delayed contrast material-enhanced magnetic resonance (MR) images in differentiation of benign from malignant breast masses. MATERIALS AND METHODS: In 49 women with 79 breast lesions (55 malignant and 24 benign), dynamic contrast-enhanced MR imaging was performed every 90 seconds during the first 7 minutes and repeated at 10, 20, 30, 40, 50, and 60 minutes after injection of contrast material. Qualitative analysis of the images was performed to evaluate the presence of the peripheral washout sign (a hypointense zone in the periphery of the lesion relative to the center). Quantitative analysis of the images was performed by measuring the signal intensity of the periphery and center of the lesions. RESULTS: The peripheral washout sign was seen in 28 (51%) of the 55 carcinomas on delayed contrast-enhanced MR images (> 10 minutes). Quantitative analysis demonstrated different enhancement profiles of the periphery and center of these lesions. The periphery showed early increase and decrease of enhancement, while the center showed gradual increase and persistent enhancement. The peripheral washout sign was not seen in any of the benign lesions. Specificity was 100% and sensitivity was 51% for diagnosis of breast carcinoma. CONCLUSION: Peripheral washout may be a reliable sign of malignancy on delayed contrast-enhanced MR images of the breast.

Adult↗
PubMed1997

Detection of malignant and benign breast lesions with an automated US system: results in 120 cases.

PURPOSE: To evaluate clinically an automated ultrasound (US) system for detecting benign and malignant breast lesions. MATERIALS AND METHODS: A prototype automated US system was used to examine 119 patients: 38 patients with 39 proved malignant breast lesions (7-50 mm), 41 patients with 41 proved benign breast lesions (8-40 mm), and 40 patients without breast lesions. The device yields a three-dimensional set of B-mode scans and reconstructed US images comparable to mammograms. All patients had undergone mammography. Four radiologists who had not performed the examinations independently assessed the mammograms and US images to detect benign and malignant breast lesions. RESULTS: Each of the four readers did not recognize one to three detectable malignant lesions on mammograms, one to two detectable malignant lesions on US images, two to four detectable benign lesions on mammograms, and five to seven detectable benign lesions on US images. All readers identified the 39 cancers with at least one of the modalities. The 40 cases without lesions were diagnosed correctly more frequently on the US images by three readers and on the mammograms by one reader. CONCLUSION: Depiction of breast lesions at automated US is reproducible. Automated US is complementary to mammography.

Breast Diseases↗
PubMed1997

MR imaging of the liver. Contrast agents.

Contrast agents are needed for improvement of lesion detection and lesion characterization on hepatic MR imaging. According to their biodistribution, contrast agents are classified into extracellular, hepatocyte-targeted, macrophage-monocytic phagocytic system(MPPS)-targeted, and blood-pool contrast agents. Dynamic MR imaging of the liver enhanced with extracellular gadolinium chelates improves lesion characterization. Hepatocyte-targeted and MPPS-targeted contrast agents improve lesion detection. Hepatocyte-targeted contrast agents that have an initial extracellular distribution phase and blood-pool contrast agents offer a potential for improvement of both detection and characterization of focal hepatic lesions.

Contrast Media↗
PubMed1997

[Minimal invasive surgery in clinically occult breast carcinoma].

The ABBI (Advanced Breast Biopsy Instrumentation) system is a new method of breast surgery of nonpalpable tumors which permits intraoperative mammography. In a pilot study it was shown that a small carcinoma can be removed by a mammographically and stereotactically controlled biopsy (20 mm maximum diameter). An indicated breast-conserving therapy can be carried out when using this method.

Biopsy↗
PubMed1996

Imaging of metastases to the liver.

Metastatic disease to the liver is an important disease from the diagnostic, prognostic and therapeutic points of view. Different imaging modalities, such as US, CT, scintigraphy, and MRI, have been used for detection, characterization, therapy planning, and follow-up of this disease with variable degrees of success and failure. This review handles the problems which face the different imaging modalities in diagnosis of liver metastases in view of the pathological background of the disease. It also discusses the indications, strong points, and shortcomings of each of the imaging modalities in diagnosis of metastases, and surveys the recent efforts done to improve their performance through the optimization of quality control and in the innovations in the field of contrast agents. Finally, a protocol is suggested for the clinical management of patients with liver metastases to optimize cost-effectiveness of the imaging modalities in this era of multimodality approach in diagnostic imaging.

Cost-Benefit Analysis↗
PubMed1996

Diagnosis and staging of carpal tunnel syndrome: comparison of magnetic resonance imaging and intra-operative findings.

PURPOSE: In order to determine the reliability of magnetic resonance imaging (MRI) in the diagnosis and staging of carpal tunnel syndrome (CTS), the most common entrapment neuropathy, the following prospective study has been performed. METHODS: We compared clinical and electrophysiological studies in 58 cases of CTS with MRI investigations and confirmed the reliability by exact correspondence with intra-operative findings. RESULTS: Typical MRI characteristics of the median nerve in CTS have been established. There is a significant difference in flattening (p < 0.05), swelling (p < 0.01) and signal intensity (p < 0.05) of the median nerve between early and advanced CTS. Comparison of MRI and intra-operative findings revealed that median nerve compression was diagnosed correctly in 91% of cases. Additional lesions in the carpal tunnel, which are a primary cause of nerve compression, were established by MRI in 25 cases and confirmed by surgery. CONCLUSION: MRI is a reliable diagnostic tool for assessing as well as staging of CTS. Morphological changes following chronic nerve compression can be visualized. It is particularly useful in cases of suspected lesions within the carpal tunnel as a cause of CTS. The information provided may support the choice of adequate treatment modality.

Adult↗