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B Hamm

Publications and source records attributed to B Hamm.

At least 109 records · Page 6Linked to original sources
PubMed2000

[Molecular MR imaging. State of the research with examples describing individual results] .

Basic medicobiological research in recent years has made rapid advances in the functional understanding of normal and pathological processes down to the molecular level. At the same time, various imaging modalities have developed from the depiction of organs to approaching the depiction of the cellular level and are about to make the visualization of molecular processes an established procedure. Besides other modalities like PET and near-infrared fluorescence, MR imaging offers some promising options for molecular imaging as well as some applications that have already been tested such as the visualization of enzyme activity, the depiction of the expression of certain genes, the visualization of surface receptors, or the specific demonstration of cells involved in the body's immune response. A major advantage of molecular magnetic resonance imaging (mMRI) over other more sensitive modalities is its high spatial resolution. However, the establishment of mMRI crucially relies on further improvements in resolution and the development of molecular markers for improving its sensitivity and specificity. The state of the art of mMRI is presented by giving a survey of the literature on experimental studies and reporting the results our study group obtained during investigation on gliomas.

Enzymes↗
PubMed2000

[Intraoperative digital radiography for diagnosis of nonpalpable breast lesions].

PURPOSE: A procedure for performing intraoperative digital radiography of diagnostic breast specimens directly in the operating suite with teleradiologic assessment by a radiologist is presented. The efficiency of this procedure is compared with that of conventional magnification mammography performed in the radiology department. MATERIAL AND METHODS: Thirty-six specimen radiographs obtained by conventional magnification mammography were compared with 38 intraoperative digital magnification radiographs (DIMA Soft P42 prototype, Feinfocus Inc., Garbsen). The radiographs were assessed for lesion conspicuity and time savings for the surgeon, anesthesiologist, and radiologist. RESULTS: The new procedure identified all 38 labeled pathological lesions, and the conventional technique likewise had a detection rate of 100% (36/36). The new technique resulted in considerable time savings for the surgeon and the radiologist. The duration of surgery was shorter and the time interval from removal of the specimen to reporting of the results was reduced from about 23 min to about 13 min. A single radiograph was sufficient for complete visualization of the specimen in all cases. CONCLUSION: Digital intraoperative specimen radiography considerably reduces the time of surgery depending on the local conditions and is highly accurate in locating a suspicious area within the tissue.

Breast Neoplasms↗
PubMed2000

Quantitative analyses of sacroiliac biopsies in spondyloarthropathies: T cells and macrophages predominate in early and active sacroiliitis- cellularity correlates with the degree of enhancement detected by magnetic resonance imaging.

OBJECTIVE: Sacroiliitis is a hallmark of the spondyloarthropathies (SpA). The degree of inflammation can be quantified by magnetic resonance imaging (MRI). The aim of this study was to further elucidate the pathogenesis of SpA by quantitative cellular analysis of immunostained sacroiliac biopsy specimens and to compare these findings with the degree of enhancement in the sacroiliac joints (SJ) as detected by dynamic MRI. METHODS: The degree of acute sacroiliitis detected by MRI after intravenous administration of gadolinium-DTPA was quantitatively assessed by calculating the enhancement observed in the SJ and chronic changes were graded as described in 32 patients with ankylosing spondylitis (n=18), undifferentiated SpA (n=12) and psoriatic arthritis (n=2). Back pain was graded on a visual analogue scale (VAS, 0-10) and disease duration (DD) was assessed. Shortly after MRI, SJ of patients with VAS > 5 were biopsied guided by computed tomography. Immunohistological examination was performed using the APAAP technique; only whole sections > 3 mm were counted. RESULTS: By MRI, chronic changes </= grade II were detected in nine patients (group I, DD 2.5 (SD 2.9) years) and > II in 13 patients (group II, DD 7.3 (SD 4.8) years), while enhancement < 70% was found in eight (group A, DD 5.6 (SD 3.3) years) and > 70% in 12 patients (group B, DD 4.7 (SD 5.8) years). The relative percentage of cartilage (78-93%), bone (7-18%) and proliferating connective tissue (1-4%) was comparable between the groups (range). There were more inflammatory cells in group I compared with group II (mean (SD) 26.7(20.1) versus 5.3 (5. 2), p=0.04) and group A compared with B (21.8 (17.3) versus 6.0 (5. 6), p=0.05) cells/10 mm(2)), T cells (10.9 (8.5)) being slightly more frequent than macrophages (9.6 (16.8/10 mm(2))). Clusters of proliferating fibroblasts were seen in three and new vessel formation in seven cases. CONCLUSION: This study shows that T cells and macrophages are the most frequent cells in early and active sacroiliitis in SpA. The correlation of cellularity and MRI enhancement provides further evidence for the role of dynamic MRI to detect early sacroiliitis.

Acute Disease↗
PubMed2000

Focal liver lesions: evaluation of the efficacy of gadobenate dimeglumine in MR imaging--a multicenter phase III clinical study.

PURPOSE: To evaluate gadobenate dimeglumine (Gd-BOPTA) for dynamic and delayed magnetic resonance (MR) imaging of focal liver lesions. MATERIALS AND METHODS: In 126 of 214 patients, MR imaging was performed before Gd-BOPTA administration, immediately after bolus administration of a 0.05- mmol/kg dose of Gd-BOPTA, and 60-120 minutes after an additional intravenously infused 0.05-mmol/kg dose. In 88 patients, imaging was performed before and 60-120 minutes after a single, intravenously infused 0.1-mmol/kg dose. T1- and T2-weighted spin-echo and T1-weighted gradient-echo images were acquired. On-site and blinded off-site reviewers prospectively evaluated all images. Intraoperative ultrasonography, computed tomography (CT) during arterial portography, and/or CT with iodized oil served as the reference methods in 110 patients. RESULTS: Significantly more lesions were detected on combined pre- and postcontrast images compared with on precontrast images alone (P <. 01). All reviewers reported a decreased mean size of the smallest detected lesion and improved lesion conspicuity on postcontrast images. All on-site reviewers and two off-site reviewers reported increased overall diagnostic confidence (P <.01). Additional lesion characterization information was provided on up to 109 (59%) of 184 delayed images and for up to 50 (42%) of 118 patients in whom dynamic images were assessed. Gd-BOPTA would have helped change the diagnosis in 99 (47%) of 209 cases and affected patient treatment in 408 (23%) of 209 cases. CONCLUSION: Gd-BOPTA increases liver lesion conspicuity and detectability and aids in the characterization of lesions.

Adult↗
PubMed2000

Coronary artery bypass grafts: improved electron-beam tomography by prolonging breath holds with preoxygenation.

In 45 patients with coronary bypass grafts, the breath-hold interval with and that without preoxygenation was measured. Its effect on depiction of the distal graft anastomosis at electron-beam tomography was evaluated. Preoxygenation prolonged the breath-hold interval in most patients, thereby allowing greater anatomic coverage including more distal anastomoses. Preoxygenation may improve scanning of coronary bypass grafts and increase detectability of graft stenoses.

Adult↗
PubMed2000

Evaluation of the accuracy of gadobenate dimeglumine-enhanced MR imaging in the detection and characterization of focal liver lesions.

OBJECTIVE: We evaluated the extent to which hepatic lesion characterization and detection is improved by using gadobenate dimeglumine for enhancement of MR images. MATERIALS AND METHODS: Eighty-six patients were imaged before gadobenate dimeglumine administration, immediately after the 2 mL/sec bolus administration of a 0.05 mmol/kg dose (dynamic imaging), and at 60-120 min after the IV infusion at 10 mL/min of a further 0.05 nmol/kg dose (delayed imaging). The accuracy for lesion characterization was assessed for a total of 107 lesions. Sensitivity for lesion detection was assessed for a total of 149 lesions detected on either intra-operative sonography, iodized oil CT, CT during arterial portography, or follow-up contrast-enhanced CT as the gold standard. RESULTS: The accuracy in differentiating benign from malignant liver lesions increased from 75% and 82% (the findings of two observers) on unenhanced images alone, to 89% and 80% on dynamic images alone (p<0.001, p = 0.8), and to 90.7% when combining the unenhanced and dynamic image sets (p<0.001, p = 0.023). Delayed images did not further improve accuracy (90% and 91%; p = 0.002, p< 0.05). A similar trend was apparent in terms of accuracy for specific diagnosis: values ranged from 49% and 62% on unenhanced images alone, to 76% and 70% on combined unenhanced and dynamic images (p<0.001, p = 0.06), and to 75% and 70% on inclusion of delayed images (p<0.001, p = 0.12). The sensitivity for lesion detection increased from 77% and 81% on unenhanced images alone, to 87% and 85% on combined unenhanced and dynamic images (p = 0.001, p = 0.267), and to 92% and 89% when all images were considered (p<0.001, p = 0.01). CONCLUSION: Contrast-enhanced dynamic MR imaging with gadobenate dimeglumine significantly increases sensitivity and accuracy over unenhanced imaging for the characterization of focal hepatic lesions, and delayed MR imaging contributes to the improved detection of lesions.

Adult↗
PubMed1999

Arthritis of the finger joints: a comprehensive approach comparing conventional radiography, scintigraphy, ultrasound, and contrast-enhanced magnetic resonance imaging.

OBJECTIVE: A prospective study was performed comparing conventional radiography, 3-phase bone scintigraphy, ultrasound, and magnetic resonance imaging (MRI) with precontrast and dynamic postcontrast examinations in 60 patients with various forms of arthritis including rheumatoid arthritis (RA), spondyl-arthropathy, and arthritis associated with connective tissue disease. METHODS: A total of 840 finger joints were examined clinically and by all 4 imaging methods. Experienced investigators blinded to the clinical findings and diagnoses analyzed all methods independently of each other. The patients were divided into 2 groups. Group 1 included 32 patients (448 finger joints) without radiologic signs of destructive arthritis (Larsen grades 0-1) of the evaluated hand and wrist and group 2 included 28 patients (392 finger joints) with radiographs revealing erosions (Larsen grade 2) of the evaluated hand and/or wrist. RESULTS: Clinical evaluation, scintigraphy, MRI, and ultrasound were each more sensitive than conventional radiography in detecting inflammatory soft tissue lesions as well as destructive joint processes in arthritis patients in group 1. All differences were statistically significant. We found ultrasound to be even more sensitive than MRI in the detection of synovitis. MRI detected erosions in 92 finger joints (20%; 26 patients) in group 1 that had not been detected by conventional radiography. CONCLUSION: Our data indicate that MRI and ultrasound are valuable diagnostic methods in patients with arthritis who have normal findings on radiologic evaluation.

Adult↗
PubMed1999

[Three-dimensional breast biopsy and surgery].

For the histological verification of suspicious non-palpable small breast tumors, the three-dimensional breast biopsy applied as cylindrical extirpation using the ABBI system is the optimal solution at present. Because of the possibility of performing mammography during the operation, errors of localization can be corrected and incorrect incisions avoided. Taking the three radiomorphologically leading symptoms into consideration--suspicious microcalcification, focal shadow and structural irregularity--it can be stated that the digital mammography of the ABBI system is more sensitive than the conventional one for detecting microcalcification, but focal shadow and structural irregularity are detected less well by digital technique. These structures should be preoperatively marked by using sonography. After the complete removal of suspicious microcalcification checked by digital mammography during the operation, residual tumor might be found in a second excision when histologically invasive or intraductal tumor terminations reach the excision margin (R1 resection). Thirteen invasive and 8 intraductal carcinomas were found in 80 cases of cylindrical extirpation using the ABBI system. In 7 procedures carried out to exclude an in-breast recurrence, 3 intraductal carcinomas and 1 invasive carcinoma were observed. In 8 of 12 invasive carcinomas and in 1 of 5 intraductal carcinomas, breast-conserving therapy was indicated. Two cases of invasive carcinoma fulfilled the criteria applied (minimal tumor-free margin > 2 mm, no extensive intraductal component) to use the ABBI cylinder as lumpectomy without a second excision to follow.

Adult↗
PubMed1999

Low-dose spiral CT: applicability to paediatric chest imaging.

BACKGROUND: Spiral CT of the chest is an imaging technique with unequivocal indications and proven higher sensitivity and specificity than conventional chest X-rays. However, particularly in children, attempts should be made to reduce radiation exposure to a minimum. OBJECTIVE. To evaluate whether a low-dose technique in spiral CT scanning results in adequate diagnostic information. MATERIALS AND METHODS: In a prospective study, 27 children (range 3 weeks to 14 years, mean 7 years) underwent a low-dose CT examination of the chest for various indications. The tube energy was 12.5 mAs (n = 5), 25 mAs (n = 17), 50 mAs (n = 3), or 75 mAs (n = 2) per slice. Two radiologists evaluated, in consensus, the CT scans with respect to their diagnostic value and comparison was made with 20 standard-dose chest CT examinations of adults (175 mAs per slice, mean age 56 years) with respect to technical image quality (noise and artefacts). In a second part of the study, dose measurements were carried out by means of exposing thermoluminescent dosimeters attached to a water/air phantom simulating a child's chest. RESULTS: All low-dose CT scans were of diagnostic image quality and no additional studies were necessary. The average image noise was significantly higher than in standard-dose CT examinations (SD 39.5 compared with 12.5 for unenhanced soft tissue, P < 0.01), but did not hinder accurate diagnosis. Artefacts were exclusively due to patient motion. Radiation exposure per slice was approx. 4 mGy at 25 mAs and 34 mGy at 250 mAs, regardless of slice thickness. CONCLUSIONS: For all indications in paediatric CT scanning of the chest, low-dose technique provides adequate image quality without loss of diagnostic information. The radiation exposure is approximately 5-20 % of a standard-dose CT.

Adolescent↗
PubMed1999

MR imaging and CT of the female pelvis: radiologic-pathologic correlation.

For imaging of the female pelvis, transvaginal ultrasound is the method of choice. Magnetic resonance imaging and CT provide important additional information in various disorders. Magnetic resonance imaging is superior to CT in diagnosing benign and malignant disorders of the uterus. The same holds for the characterization of adnexal masses, where MR imaging reliably differentiates dermoids, ovarian fibromas, and most endometriomas. Differentiation of other benign and malignant ovarian tumors by CT and MR imaging is based on identical morphological criteria; no superiority of MR imaging over CT has been established. Computed tomography is still the preferred imaging modality for staging ovarian cancer. A thorough knowledge of the pathomorphological changes associated with the different disorders of the female pelvis not only helps to choose the proper imaging modality and examination protocol, but also improves image interpretation.

Female↗
PubMed1999

CT and MRI of the male genital tract: radiologic-pathologic correlation.

Technical advances in magnetic resonance imaging (MRI), notably in high-resolution MRI, have opened up new diagnostic applications in male pelvic pathology. A major indication is the preoperative staging of prostate cancer, where MRI is more reliable than other imaging modalities in differentiating between localized and advanced disease. In monitoring local recurrence after radical prostatectomy MRI is also valuable in differentiating scar tissue from new growth. In benign prostate disease, MRI effectively displays the congenital cysts that may be associated with infertility. Other disease, however - notably benign prostatic hyperplasia - is generally an incidental finding. Ultrasound remains the imaging modality of choice for evaluation of pathologies of the penis, testis and scrotum, e. g. in differentiating malignant from benign scrotal masses or in diagnosing acute scrotum due to testicular torsion or rupture. In isolated cases, MRI is also a valuable diagnostic aid in conditions of these organs, e. g. in the preoperative localization of ectopic testes in cryptorchidism or if US findings are equivocal.

Genital Diseases, Male↗
PubMed1999

Tumor diagnosis in the adult liver transplant candidate.

Hepatic transplantation has emerged as a potentially curative treatment of certain malignant hepatic neoplasms such as hepatocellular carcinoma, bile duct carcinoma, fibrolamellar hepatocellular carcinoma, metastases from neuroendocrine tumors, and epithelioid hemangioendothelioma. In the early years of hepatic transplantation, there was great enthusiasm to cure patients with unresectable hepatobiliary malignancy. This early enthusiasm was tempered by the unfavorable outcome of transplantation in advanced cases of malignancy and the organ-donor shortage. Presently, patients have to be selected with predictable likelihood for long-term survival. Pre-transplantation imaging is indispensable for detection, characterization, staging, and surgical road-mapping before the procedure. The present article focuses on the role of imaging modalities in these different aspects of preoperative assessment.

Adult↗
PubMed1999

[The use of automated speech recognition in diagnostic radiology].

PURPOSE: Applicability and benefits of digital speech recognition in diagnostic radiology were tested using the speech recognition system SP 6000. METHODS: The speech recognition system SP 6000 was integrated into the network of the institute and connected to the existing Radiological Information System (RIS). Three subjects used this system for writing 2305 findings from dictation. After the recognition process the date, length of dictation, time required for checking/correction, kind of examination and error rate were recorded for every dictation. With the same subjects, a correlation was performed with 625 conventionally written finding. RESULTS: After an 1-hour initial training the average error rates were 8.4 to 13.3%. The first adaptation of the speech recognition system (after nine days) decreased the average error rates to 2.4 to 10.7% due to the ability of the program to learn. The 2nd and 3rd adaptations resulted only in small changes of the error rate. An individual comparison of the error rate developments in the same kind of investigation showed the relative independence of the error rate on the individual user. CONCLUSION: The results show that the speech recognition system SP 6000 can be evaluated as an advantageous alternative for quickly recording radiological findings. A comparison between manually writing and dictating the findings verifies the individual differences of the writing speeds and shows the advantage of the application of voice recognition when faced with normal keyboard performance.

Germany↗
PubMed1999

[Diagnostic assessment after myocardial infarction: What is the role of magnetic resonance imaging?].

There have been considerable advances in the diagnostic assessment of the heart by magnetic resonance imaging (MRI) in recent years. Thus MRI as a one-stop shop modality for the comprehensive noninvasive evaluation of coronary heart disease and myocardial infarction may soon become a reality. This article presents an overview of the present possibilities and future potential of evaluating myocardial anatomy, function, perfusion, and coronary anatomy after myocardial infarction. Cine MRI provides a reliable analysis of regional and global disturbances of cardiac wall motion with a high temporal and spatial resolution. Tagging techniques permit the noninvasive labelling of parts of the myocardium and the identification of three-dimensional patterns of contraction. Myocardial perfusion and disturbed wall motion under pharmacologic stress can be reliably assessed by MRI as well. What is unique is the visualization of myocardial edema, which is made possible by the high soft-tissue contrast resolution. The as yet limited potential to assess coronary arteries and coronary bypasses is likewise discussed.

Diagnosis, Differential↗
PubMed1999

[The value of MRT in the diagnosis of benign and malignant tumors of the uterus].

Magnetic resonance (MR) imaging gains a more and more important role in the diagnostic assessment of the female pelvis. The free selection of the imaging plane is of particular importance for the visualization of the uterus, and the high soft-tissue contrast presently offers the best possibilities for assessment of the zonal anatomy of the uterus. Advances in coil technology and the use of time-saving pulse sequences that, in addition, yield high-resolution images (e.g., fast spin-echo sequences) have made MR imaging a reliable diagnostic modality with a high image quality. There is no doubt that ultrasound continues to be the most widely used imaging modality besides the clinical examination. However, ultrasound is not only limited by high interexaminer variation but also by an insufficient tissue characterization and, above all, the lacking possibility of staging malignancies. Computed tomography has turned out to be inefficient in determining the local tumor stage due to its poor soft-tissue contrast and should thus only be used in advanced tumor stages. MR imaging, on the other hand, excellently depicts the morphologic details of the female pelvis and helps in the assessment of both benign and malignant masses of the uterus and has the highest diagnostic value in staging malignancies. Furthermore, recent studies have shown that MR imaging is also cost-effective as a pretherapeutic modality in cervical cancer.

Adult↗
PubMed1999

Evaluation of liposomal contrast agents for liver CT in healthy rabbits.

RATIONALE AND OBJECTIVES: To evaluate the efficiency of two new liposomal contrast agents aimed at the reticuloendothelial system for liver CT in comparison to an extracellular contrast agent. METHODS: Two liposomal contrast agents (BR2 and BR21, respectively), containing free as well as encapsulated iomeprol at different concentrations, and commercially available free extracellular iomeprol were studied. In 60 experiments, the three contrast agents were tested at five different doses in rabbits. Intravenous injection was followed by dynamic CT studies over a period of 0 to 120 minutes (0 to 6 hours in 3 animals). A quantitative analysis of the enhancement in aorta and liver was performed. RESULTS: In healthy rabbits, the two liposomal contrast agents induced a significantly higher and more persistent increase in liver density at doses of > or = 1.5 mL/kg compared with the extracellular agent. The density enhancement induced by the two liposomal agents was dose-dependent and reached a maximum of +102 Hounsfield units (HU), compared with +87 HU for the extracellular contrast agent, at 2.0 mL/kg, without any appreciable increases at higher dosages. An adequate liver enhancement of at least +40 HU persisted for up to 90 minutes after injection of the liposomal contrast agents, compared with < 5 minutes after the extracellular agent. BR2 tended to provide a higher and more persistent enhancement than BR21. CONCLUSIONS: Liposomal contrast agents induce a more pronounced and much more persistent increase in liver density than conventional extracellular agents. Liposomes thus have the potential for optimizing CT examinations of the liver by providing a larger imaging window.

Animals↗
PubMed1999

Experimental study of X-ray mammography in a fluid bath: reduced radiation dose and improved detail resolution.

OBJECTIVE: To determine the effects on x-ray mammography of embedding the breast in a fluid bath. METHODS: A plexiglass phantom in the shape of a compressed breast was x-rayed in air and water with a mammography unit, and the radiation dose was measured by 20 thermoluminescence dosimeters placed in 20 representative positions on the surface of the phantom. Udders from slaughtered sheep as an animal model and phantoms were examined by mammography in identical positions surrounded by air and different fluids. The images were evaluated for detail resolution subjectively (animal model) and objectively (phantom containing quantifiable structures) by 6 and 15 blinded readers, respectively. The readers' results were analyzed and compared for visualization of the objects in air versus fluid. RESULTS: Mammographic examination in the fluid bath reduced the radiation dose and improved detail resolution in the rounded margin of the breast. Also, viewing conditions in the central region were improved as a result of the uniform optical density across the entire film area. CONCLUSIONS: Performing x-ray mammography in a fluid bath has advantages that make the technical realization of this method desirable.

Air↗