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J Lorenzen

Publications and source records attributed to J Lorenzen.

At least 37 records · Page 2Linked to original sources
PubMed2003

[MR-imaging of the breast at 0.5 Tesla: menstrual-cycle dependency of parenchymal contrast enhancement in healthy volunteers with oral contraceptive use?].

INTRODUCTION: To evaluate changes of contrast medium enhancement of the breast parenchyma due to menstrual cycle in healthy volunteers with oral contraceptive use in MR-imaging of the breast. MATERIAL AND METHODS: 15 healthy volunteers (age: 22 - 36, mean 28,2) without breast disease were examined two times during one menstrual cycle (days 7 - 14 and days 21 - 2). Two volunteers were examined only in the second part of the cycle (days 21 - 2). All volunteers used oral contraceptives for more than 6 month continuously. Examinations were performed with a 0,5 T magnet (dynamic 3D-gradient echo protocol with subtraction postprocessing). We evaluated the number of enhancing foci and the parenchymal contrast medium enhancement during the different phases of the cycle by region of interest. RESULTS: Only a total of two enhancing foci were found in 2 of 17 volunteers. Time/signal intensity diagrams in these both cases were not suspicious (< 80 % initial signal increase after of contrast medium injection, no wash-out phenomenon) and sonography of the breast in these two cases was inconspicuous. Contrast medium enhancement of breast parenchyma in cycle days 7 - 14 (mean enhancement: 0.12 - 0.26, minutes 1 - 9 p. i.) was not significantly different (p = 0.2209; Wilcoxon signed rank test) from cycle days 21 - 2 (mean: 0.13 - 0.32). CONCLUSION: Menstrual cycle dependency of parenchymal contrast medium enhancement seems to be of minor relevance for premenopausal women with use of oral contraceptives.

Adult↗
PubMed2003

[Elastography: Quantitative imaging modality of the elastic tissue properties].

The wide range of elastic tissue properties and the difference in elasticity of tumors and the adjacent tissues have provided motivation for developing elasticity imaging techniques. These research efforts have converged with the development of a new imaging modality, the so-called elastography, with the acquired and processed images referred to as elastograms. This modality was pioneered for ultrasonic imaging, which provides the majority of experience on this topic. MR-elastography has been developed in recent years. The published clinical data range from the characterization of prostate and breast cancer in oncology and dynamic examinations of skeletal muscle to intravascular elastic differentiation of vessel plaques. Advantages of the ultrasonic elastography are ubiquitous applicability and cost-effectiveness. MR elastography offers improved reconstruction and the possibility to assess potential anisotropic properties. The different approaches of elastography, their technical and clinical application and the limitations known so far are reviewed in this paper.

Anisotropy↗
PubMed2002

MR elastography of the breast:preliminary clinical results.

PURPOSE: Imaging of breast tumors and various breast tissues using magnetic resonance (MR) elastography (MRE) to explore the potential of elasticity as a new parameter for the diagnosis of breast lesions. METHODS: Low-frequency mechanical waves are transmitted into breast tissue by means of an oscillator. The local characteristics of the mechanical wave are determined by the underlying elastic properties of the tissue. Theses waves can be displayed by means of a motion-sensitive spin-echo MR sequence within the phase of the MR image. Elasticity reconstruction is performed on the basis of 8 "snapshots" of each wave within the three spatial directions. We performed in-vivo measurements in 15 female patients with malignant tumors of the breast, 5 patients with benign breast tumors, and 15 healthy volunteers. RESULTS: Malignant invasive breast tumors documented the highest values of elasticity with a median of 15.9 kPa and a wide range of stiffnesses between 8 and 28 kPa. In contrast, benign breast lesions represented low values of elasticity, which were significantly different from malignant breast tumors (median elasticity: 7.0 kPa; p = 0.0012). This was comparable to the stiffest tissue areas in healthy volunteers (median elasticity 7.0 kPa), whereas breast parenchyma (median: 2.5 kPa) and fatty breast tissue (median: 1.7 kPa) showed the lowest values of elasticity. Two invasive ductal carcinomas had elasticity values of 8 kPa and two stiff parenchyma areas in healthy volunteers had elasticities of 13 and 15 kPa. These lesions could not be differentiated by their elasticity. CONCLUSION: We conclude that MRE is a promising new imaging modality with the capability to assess the viscoelastic properties of breast tumors and the surrounding tissues. However, from our preliminary results in a small number of patients it is obvious that there is an overlap in the elasticity ranges of soft malignant tumors and stiff benign lesions.

Adult↗
PubMed2002

[Percutaneous core-needle biopsy of palpable breast tumors. Do we need ultrasound guidance?].

INTRODUCTION: Percutaneous core-needle biopsy is widely accepted for preoperative histologic assessment of suspicious breast lesions. The purpose of this study was to asses the impact of continuous sonographic guidance on diagnostic accuracy of large core needle biopsy of palpable breast lesions. METHOD: We analysed 170 breast lesions in a retrospective study. Percutaneous breast biopsies were performed by using a biopsy gun with 14-gauge needles. Eighty-eight biopsies were performed under continuous ultrasound guidance (group II) and 82 biopsies without ultrasound documentation of the procedure (group I). Core needle diagnoses were compared with the patients final tissue diagnosis as based on surgical excisional biopsy. RESULTS: In patient group I, 17 lesions were categorized as core breast biopsy cancer misses (sensitivity 79 %). The sensitivity in this group showed an obvious dependency on tumor size. Among the 17 false negative lesions, 13 lesions were 3 cm in mean diameter or smaller. Two false negative findings occurred in group II (sensitivity 98 %), with a tumor size of 0.5 and 1.0 cm. CONCLUSION: Sonographic guidance is indispensable to ensure adequate diagnostic accuracy for core-needle biopsy of palpable breast lesions.

Adult↗
PubMed2002

[MRI-based N-staging in esophageal cancer].

PURPOSE: For planning the therapeutic strategies and estimating the prognosis in esophageal cancer, N-staging is very important. To date, MRI still is of minor importance as imaging modality of the mediastinum despite promising developments in the past, like ECG-gating or "averaging" sequences, e. g., LOTA (Long-term averaging), which facilitate mediastinal and thoracic MR-imaging. In a prospective approach, the value of MRI based N-staging was examined with respect to LOTA-sequences. MATERIAL AND METHODS: Within four weeks prior to esophagectomy, standardized MRI of the esophagus was performed in 15 patients (10 squamous-cell-carcinomas and 5 adenocarcinomas) using a 1.5 T whole body scanner. Imaging quality was classified based on depiction of aortic wall or tracheal wall layers. Criteria for malignant infiltration were a diameter of more than 15 mm or a round appearance of a lymph node together with GD-DTPA enhancement. All data were blinded and separately read by two radiologists. The data of the study were compared with those from the pathological workup of the resected specimen. RESULTS: MRI had a sensitivity of 100 % and a specificity of 78 % for lymph node metastases. Due to incomplete depiction of the celiac trunk (M1), nodal metastasis in a non-enlarged node was missed. CONCLUSION: With modern MRI, N-staging is almost as accurate as the gold standard endoscopic ultrasound and should particularly be used in patients not suited for an endoscopic ultrasound examination.

Adenocarcinoma↗
PubMed2001

Locoregional treatment of low-grade B-cell lymphoma with CD3xCD19 bispecific antibodies and CD28 costimulation. II. Assessment of cellular immune responses.

Ten patients with advanced B-cell lymphoma were treated with a single locoregional injection of CD3xCD19 bispecific and costimulating CD28 monospecific antibodies to activate tumor-infiltrating T-lymphocytes. Antibodies were administered at 4 different dose levels (30 microg, 270 microg, 810 microg, 1,600 microg of each antibody) either by intratumoral or intralymphatic injection. Most patients developed responses within different compartments of the immune systems (T cells, NK cells) subsequent to the antibody application. Comparative studies in 2 patients of which treated as well as untreated lymph nodes were available revealed the up-regulation of T-cell activation markers induced by the antibody injection. Additionally, in 1 patient the induction of apoptosis of lymphoma B cells in the antibody-treated lymph node was observed. Specificity analyses of peripheral blood T cells by means of IFN-gamma ELISpot measurement indicated the recruitment of idiotype-specific T cells, as in 1 out of 3 investigated patients an increased T-cell response toward autologous idiotype peptides could be demonstrated. We conclude that a single injection of CD3xCD19 bispecific antibodies is capable to induce an activation of autologous T lymphocytes if simultaneous costimulatory signaling by CD28 antibodies is provided. Furthermore, our data suggest that at least in some patients lymphoma-specific T cells can be recruited by this immunotherapeutic approach toward B-cell lymphoma.

Aged↗
PubMed2001

[Imaging of breast tumors using MR elastography].

PURPOSE: Imaging of breast tumors using MR-Elastography. MATERIAL AND METHOD: Low-frequency mechanical waves are transmitted into breast-tissue by means of an oscillator. The local characteristics of the mechanical wave are determined by the elastic properties of the tissue. By means of a motion-sensitive spin-echo-sequence these waves can be displayed within the phase of the MR image. Subsequently, these images can be used to reconstruct the local distribution of elasticity. In-vivo measurements were performed in 3 female patients with malignant tumors of the breast. RESULTS: All patients tolerated the measurement set-up without any untoward sensation in the contact area of skin and oszillator. The waves completely penetrated the breast, encompassing the axilla and regions close to the chest wall. All tumors were localized by MRE as structures of markedly stiffer tissue when compared to the surrounding tissue. Furthermore, in one patient, a metastasis in an axillary lymph node was detected. In all patients, local regions of increased elasticity were found in the remaining parenchyma of the breast, which, however, did not reach the high levels of elasticity found in the tumors. CONCLUSION: MRE is an imaging modality enabling adjunct tissue differentiation of mammary tumors.

Adult↗
PubMed2001

Value of FDG PET in patients with fever of unknown origin.

Fever of unknown origin (FUO) is a diagnostic challenge, because the cause of such fever may be manifold. Studies on the use of positron emission tomography (PET) using 18F-fluorodeoxyglucose (18F-FDG), for the diagnosis of inflammation in patients with osteomyelitis or HIV have been promising and suggest its use in patients with FUO. In this study, we used FDG PET in 16 patients with FUO in whom conventional diagnostics had not been conclusive. In 12 patients, (75%) non-physiological accumulations of FDG were found which led to the final diagnosis in 11 patients (69%). FDG PET was negative in four patients (25%). Two of these patients had rheumatic fever, while in the other two patients the origin of fever could not be detected within 3 months after PET by any other laboratory or imaging means. These findings point to the high sensitivity of FDG whole-body PET for the detection of morphologically assessable foci as an origin of FUO. Moreover, they suggest a high negative predictive value of FDG PET in the setting of FUO, since in no patient with a negative FDG PET could a morphological origin of the fever be determined. In conclusion, FDG whole-body PET appears to be a promising diagnostic tool in patients with FUO, in whom conventional diagnostics had been unsuccessful.

Adult↗
PubMed2001

Genetic characterization of a Sinorhizobium meliloti chromosomal region in lipopolysaccharide biosynthesis.

The genetic characterization of a 5.5-kb chromosomal region of Sinorhizobium meliloti 2011 that contains lpsB, a gene required for the normal development of symbiosis with Medicago spp., is presented. The nucleotide sequence of this DNA fragment revealed the presence of six genes: greA and lpsB, transcribed in the forward direction; and lpsE, lpsD, lpsC, and lrp, transcribed in the reverse direction. Except for lpsB, none of the lps genes were relevant for nodulation and nitrogen fixation. Analysis of the transcriptional organization of lpsB showed that greA and lpsB are part of separate transcriptional units, which is in agreement with the finding of a DNA stretch homologous to a "nonnitrogen" promoter consensus sequence between greA and lpsB. The opposite orientation of lpsB with respect to its first downstream coding sequence, lpsE, indicated that the altered LPS and the defective symbiosis of lpsB mutants are both consequences of a primary nonpolar defect in a single gene. Global sequence comparisons revealed that the greA-lpsB and lrp genes of S. meliloti have a genetic organization similar to that of their homologous loci in R. leguminosarum bv. viciae. In particular, high sequence similarity was found between the translation product of lpsB and a core-related biosynthetic mannosyltransferase of R. leguminosarum bv. viciae encoded by the lpcC gene. The functional relationship between these two genes was demonstrated in genetic complementation experiments in which the S. meliloti lpsB gene restored the wild-type LPS phenotype when introduced into lpcC mutants of R. leguminosarum. These results support the view that S. meliloti lpsB also encodes a mannosyltransferase that participates in the biosynthesis of the LPS core. Evidence is provided for the presence of other lpsB-homologous sequences in several members of the family Rhizobiaceae.

Bacterial Proteins↗
PubMed2000

Recombinant anti-CD25 immunotoxin RFT5(SCFV)-ETA' demonstrates successful elimination of disseminated human Hodgkin lymphoma in SCID mice.

Since clinical phase-I/II trials in patients with resistant Hodgkin's lymphoma treated with the chemically linked anti-CD25 ricin-A-chain immunotoxin RFT5-SMPT-dgA indicate promising results for patients with minimal residual disease, we constructed a new immunotoxin by fusing the RFT5 single-chain variable fragment to a deletion mutant of Pseudomonas exotoxin A (ETA'). The recombinant protein was directed into the periplasmic space of E. coli by means of the pET-derived expression vector pBM1.1 and our newly developed expression/purification method. Biologically active RFT5(scFv)-ETA' was isolated by freezing/thawing and purified by immobilized metal-ion affinity and molecular-size-chromatography. RFT5(scFv)-ETA' was subsequently used for the treatment of disseminated human Hodgkin's lymphoma in a SCID-mouse model. The mean survival time (MST) of L540rec-challenged SCID mice was 38.1 days. A single i.v. injection of 40 microg recombinant immunotoxin (rIT) 1 day after tumor inoculation resulted in 100% tumor-free mice, extending the MST to more than 220 days (p < 0.0001). The blood-distribution time T(1/2)alpha was 39.65 min, the serum elimination time T(1/2)alpha, 756.6 min. All animals were assessed for soluble interleukin-2 receptor alpha, which is directly correlated to tumor burden. Soluble CD25 was not detectable in mice treated with the rIT. Our findings, concerning potent anti-tumor effects of a recombinant anti-CD25 immunotoxin against disseminated Hodgkin's lymphoma in SCID mice reported here demonstrate that RFT5(scFv)-ETA' might be suitable for further evaluation against Hodgkin's lymphoma in humans.

Animals↗
PubMed2000

Psychoactive substance use diagnoses among psychiatric in-patients.

OBJECTIVE: To estimate the prevalence and possible under-diagnosing of substance use disorders and to consider factors that might influence diagnosing of substance use disorders. METHOD: Data collected from case records and PSE interviews of psychiatric in-patients from 12 psychiatric departments in Denmark admitted during October 1996 were compared with data from the Danish Psychiatric Register. RESULTS: A substantially lower prevalence of substance use diagnoses were found in the register (26.1%) than in the research data (50.0%). A high prevalence of co-occurrence between substance use disorders and mental disorders other than substance use disorders was found (37.3%). In the majority of cases knowledge of the substance use disorders was present in the case records, although they had not resulted in a diagnosis. CONCLUSION: The under-diagnosis of substance use disorders is due not only to concealed diagnostic signs and symptoms but also to an under-diagnosis by the psychiatrists, in spite of the fact that information on the substance use was accessible.

Adult↗
PubMed2000

High-resolution tensor MR elastography for breast tumour detection.

MR elastography is a novel imaging technique for the visualization of elastic properties of tissue. It is expected that this method will have diagnostic value for the clarification of suspicious breast lesions. Low-frequency mechanical waves are coupled into the tissue and visualized via an MR sequence which is phase-locked to the mechanical excitation. Commonly, elasticity is assumed to be isotropic and reconstruction is performed in only two dimensions. The technique is extended to three dimensions such that the entire symmetric elasticity tensor is assessed. This is achieved by measuring different phases of the mechanical wave during one oscillatory cycle. Thereby it is possible to provide information about the anisotropy of the elasticity tensor. Finite-element simulations as well as phantom experiments are performed to demonstrate the feasibility of the method. Initial clinical results of a breast carcinoma are presented. The analysis of the eigenvalues of the elasticity tensor support the hypothesis that breast carcinoma might exhibit an anisotropic elasticity distribution. The surrounding benign tissue appears isotropic. Thereby new and additional diagnostic information is provided which might help in distinguishing between benign and malignant breast diseases.

Algorithms↗
PubMed1999

Polycythemia vera megakaryocytes but not megakaryocytes from normal controls and patients with smokers polyglobuly spontaneously express IL-6 and IL-6R and secrete IL-6.

Polycythemia rubra vera (PV) represents a clonal hematological disorder defined by an abnormal expansion of erythroid precursors and megakaryopoiesis, in particular. Ample evidence has been provided that the IL-6/1L-6R complex may be responsible for the proliferation of normal and neoplastic megakaryocytes in vitro and this fact lead us to the hypothesis, that defects in the regulation of IL-6 synthesis take part in the pathogenesis of PV. The study was carried out to determine the IL-6 serum levels and the megakaryocytic IL-6 production in patients with PV and to compare these data with the situation in hematologically healthy donors as well as in patients suffering from spurious polycythemia--smokers polyglobuly (PG). For this purpose, IL-6 serum levels were measured by ELISA and the megakaryocytic production studied by immunohistochemistry, reverse hemolytic plaque assay (RHPA) together with reverse transcription/polymerase chain reaction (RT-PCR) in highly enriched megakaryocyte preparations. In additional experiments, the influence of IL-3 stimulation and the expression of IL-6R were tested. Serum levels of IL-6 did not differ between the three groups under study. In contrast, immunohistochemistry revealed a raised proportion of megakaryocytes expressing IL-6 in PV as compared to normal donors and patients suffering from PG. The percentage of megakaryocytes actively secreting this cytokine as detected by the RHPA was 20 times greater than in both the other groups. This phenomenon was further substantiated by the fact that IL-6 mRNA could only be shown in PV megakaryocyte preparations. The regulation of IL-6 secretion appears to be abnormal in PV. Whereas in the normal and in the PG group IL-3 stimulation exerts a marked increase in megakaryocytic IL-6 secretion, PV megakaryocytes responded with a paradoxical down-regulation of IL-6 synthesis combined with the loss of IL-6R. Our data describe for the first time an abnormally raised IL-6 production by PV megakaryocytes and point towards fundamental regulatory alterations of the IL-6 synthesis in this disease.

Bone Marrow↗
PubMed1999

[A search for the focus in patients with fever of unknown origin: is positron-emission tomography with F-18-fluorodeoxyglucose helpful?].

PURPOSE: Search for focus in patients with fever of unknown origin (FUO). MATERIAL AND METHODS: In four patients with the above mentioned problem, F-18-FDG-PET was performed, following the common imaging methods, which were without evidence for a focus. RESULTS: The origin of FUO was verified in all patients by PET: Tuberculosis, pneumocystis-carinii pneumonia, chronic inflammatory hematoma, aortitis. CONCLUSION: Successful implementation of F-18-FDG-PET as additional imaging method in patients with FUO seems reasonable. This has to be verified by further prospective studies.

Adolescent↗
PubMed1999

[Onco-PET: lesion detection by monitor versus standardized film documentation].

AIM: Lesion detection and localization of 2-[18F]fluoro-2-deoxy-D-glucose (F-18-FDG) Onco-PET-Investigations are usually performed on-line at the computer display. The aim of the present study was to evaluate the clinical efficacy of a standardized film documentation as an alternative approach. METHODS: 100 Onco-PET-investigations without attenuation correction were analyzed with regard to number and localization of lesions suspicious of malignancy. A standardized documentation on film was developed including 1. transversal slices of the brain, 2. coronal slices and maximum-intensity-projections (MIPs) of the head/neck region and 3. of the trunk and 4. MIPs of the legs. These transparencies were analyzed at the light box. An additional analysis on the computer display was performed slice by slice in coronal, transversal and sagittal directions for the whole body. RESULTS: A total of 315 lesions were detected in 100 patients. In 96/100 patients the two modalities agreed both in number and localization of tumor-suspicious lesions. 7 lesions in the legs of 3 patients didn't show when interpreting the films (MIPs only). In 2/100 patients additional analysis on the computer display caused a change in the localization of 9/315 lesions. 8 of these were located in the legs. When adding coronal slices for the documentation of the lower extremities all the lesions were shown. Moreover, all lesions were localized correctly except one clinically non-relevant change of localization out of a total of 322 lesions. CONCLUSION: The newly developed standardized documentation supports the concept of film reading and reporting of onco-PET investigations, restricting an additional on-line analysis to rare cases only. Furthermore, the intention of the "Arbeitsgemeinschaft Standardisierung" (work group standardisation) are met, i.e. to ease analysis of follow-up studies acquired at different places.

Documentation↗
PubMed1999

[Granulation tissue: pitfall in therapy control with F-18-FDG PET after chemotherapy].

False positive findings in primary tumor and metastasis diagnostics by FDG-PET due to FDG-uptake in inflammatory foci are documented in literature. The demonstrated case reveals that increased uptake of FDG in activated neutrophile granulocytes and macrophages has to be taken into consideration in therapy control under chemotherapy, too. In a 53 year old patient FDG-PET was performed after chemotherapy of an abdominal Non-Hodgkin lymphoma for evaluation of persistent tumor vitality. The margin of the persisting mass showed increased uptake of glucose. Histology documented a necrotic center surrounded by granulation tissue.

Abdominal Neoplasms↗