How fast is optically induced electron transfer in organic mixed valence systems?

The rate of thermally induced electron transfer in organic mixed valence compounds has thoroughly been investigated by e.g. temperature dependent ESR spectroscopy. However, almost nothing is known about the dynamics of optically induced electron transfer processes in such systems. Therefore, we investigated these processes in mixed valence compounds based on triphenylamine redox centres bridged by conjugated spacers by NIR transient absorption spectroscopy with fs-time resolution. These experiments revealed an internal conversion (IC) process to be on the order of 50-200 fs which is equivalent to the back electron transfer after optical excitation into the intervalence charge transfer band. This IC is followed by ultrafast cooling to the ground state within 1 ps. Thus, in the systems investigated optically induced electron transfer is about 3-4 orders of magnitude faster than thermally induced ET.

Energy redistribution dynamics in triarylamine-triarylborane containing hexaarylbenzenes.

Two hexaarylbenzenes (HAB) 1 and 2 each decorated by three triarylamines (TAA) as electron donors and three triarylboranes (TAB) as electron acceptors in a symmetric (1) and asymmetric (2) fashion as well as one model compound (3) with only one donor-acceptor pair were investigated by ultrafast transient absorption and fluorescence upconversion spectroscopy. Fluorescence anisotropy measurements revealed energy redistribution between localised, partly relaxed CT-states of the HABs 1 and 2 induced by dipole-dipole interaction with energy transfer time constants of ca. 3 ps. These results manifest symmetry breaking in the formally symmetric HAB 1 upon photoexcitation.

A photoinduced mixed-valence state in an organic bis-triarylamine mixed-valence compound with an iridium-metal-bridge.

Upon irradiation a mixed-valence (MV) state is formed in a donor-iridium(III)-acceptor triad by a photoinduced electron transfer process. The resulting radical and intervalence charge transfer (IV-CT) absorptions cover a wide spectral range (3200-400 nm). These results were supported by spectroelectrochemistry, fs-time resolved pump-probe spectroscopy and assisted by TD-DFT calculations.

Diffusion-weighted magnetic resonance imaging of breast lesions: the influence of different fat-suppression techniques on quantitative measurements and their reproducibility.

OBJECTIVE: The aim of this study was to evaluate the influence of different fat-suppression techniques on quantitative measurements and their reproducibility when applied to diffusion-weighted imaging (DWI) of breast lesions. METHODS: Twenty-five patients with different types of breast lesions were examined on a clinical 1.5-T magnetic resonance imaging (MRI) system. Two diffusion-weighted sequences with different fat-suppression methods were applied: one with spectral presaturation by inversion recovery (SPIR), and one with short-TI inversion recovery (STIR). The acquisition of both sequence variants was repeated with modified shim volume. Lesion-to-background contrast (LBC), apparent diffusion coefficients (ADC) ADC(0,1000) and ADC(50,1000), and their coefficients of variation (CV) were determined. RESULTS: In four patients, the image quality of DWI with SPIR was insufficient. In the other 21 patients, 46 regions of interest (ROI), including 11 malignant and 35 benign lesions, were analysed. The LBC, ADC(0,1000) and ADC(50,1000) values, which did not differ between initial and repeated measurements, were significantly higher for STIR than for SPIR. The mean CV improved from 10.8 % to 4.0 % (P = 0.0047) for LBC, from 6.3 % to 2.9 % (P = 0.0041) for ADC(0,1000), and from 6.3 % to 2.6 % (P = 0.0049) for ADC(50,1000). CONCLUSION: For STIR compared to SPIR fat suppression, improved lesion conspicuity, higher ADC values, and better measurement reproducibility were found in breast DWI. KEY POINTS: • Quality of fat suppression influences quantitative DWI breast lesion measurements. • In breast DWI, STIR fat suppression worked more reliably than SPIR. • Lesion-to-background contrast and its reproducibility were significantly higher with STIR fat suppression. • Lesional ADCs and their reproducibility were significantly higher with STIR fat suppression.

A patient with portal hypertension and blindness after transjugular intrahepatic portosystemic shunt.

We report on a case of recurrent variceal bleeding from gastric varices, which was treated with transjugular intrahepatic portosystemic shunt (TIPS) and Histoacryl injection into the gastric varices. Furthermore, the patient had a small patent foramen ovale without a right-to-left shunt. After the intervention, the patient developed acute neurological disorders as a result of a cerebral paradoxical embolism. In the following, we describe the potential risk of histoacryl in paradoxical embolization when used for the injection of variceal collaterals during TIPS placement in patients with portal hypertension. The present case report shows a very rare but important complication after TIPS implantation. To avoid this complication it is recommended to perform echocardiography before all TIPS placements.

[Magnetic resonance imaging of the brain in patients with cardiac pacemakers. Experimental and clinical investigations at 1.5 Tesla]. / MRT-Untersuchungen des Hirns bei Patienten mit implantierten Herzschrittmachern. Experimentelle und klinische Untersuchungen an einem 1.5 Tesla-System.

PURPOSE: In-vitro and In-vivo evaluation of feasibility and safety of MRI of the brain at 1.5 T in patients with implanted pacemakers (PM). MATERIALS AND METHODS: 24 PM models and 45 PM electrodes were tested In-vitro with respect to translational forces, heating of PM leads, behaviour of reed switch (activated vs. deactivated) and function at a 1.5 T MRI-system (actively shielded, maximum field gradient: 30 mT/m; rise time: 150 T/m/s). Based on these results, 63 MRI examinations in 45 patients with implanted PM were performed. Prior to MRI the PM were re-programmed in an asynchronous mode. The maximum SAR of MRI-sequences was limited to 1.2 W/kg. Continuous monitoring of ECG and pulse oximetry was performed during MRI. PM inquiry was performed prior to MRI, immediately after MRI and -- to assess long-term damages -- three months after the MRI exams, including determination of stimulation thresholds to assess potential thermal myocardial injuries at the lead tips. RESULTS: Translational forces (F (max) < or = 560 mN) and temperature increase (DeltaT (max) < or = 2.98 degrees C) were in a range which does not represent a safety concern from a biophysical point of view. No changes to the programmed parameters of the PM or damage of PM components were observed neither In-vitro (n = 0/24) nor In-vivo (n = 0/63). Despite the strong magnetic field, the reed switch remained deactivated in 54 % (13/24) of the cases during In-vitro simulated MRI exams of the brain. All patient studies (n = 63/63) could be completed without any complications. Atrial and ventricular stimulation thresholds (expressed as pulse duration at 2-fold rheobase) did not change significantly immediately post-MRI nor in the 3 months follow-up (pre-MRI: 0.17 ms +/- 0.13 ms, post-MRI: 0.18 ms +/- 0.14 ms, 3 months follow-up: 0.17 ms +/- 0.12 ms). CONCLUSION: MRI of the brain at 1.5 Tesla can be safely performed in carefully selected clinical circumstances when appropriate strategies are used (re-programming the PM to an asynchronous mode, continuous monitoring of ECG and pulse oximetry, limiting the SAR value of the MRI sequences, cardiological stand-by). Based on these studies, implanted PM should not longer be regarded as an absolute contraindication for MRI at 1.5 T.

[The value of applying nitroglycerin in 3D coronary MR angiographie with real-time navigation technique]. / Wert der Applikation von Nitroglycerin bei der 3D-MR-Koronarangiographie mit Echtzeit-Navigatortechnik.

PURPOSE: Nitroglycerin administration results in dilation of epicardial coronary vessels and in an increase in coronary blood flow, and has been suggested to improve MR coronary angiography. This study evaluates systematically whether administration of nitroglycerin improves the visualization of coronary arteries and, as a result, the detection of coronary artery stenosis during free breathing 3D coronary MR angiography. MATERIALS AND METHODS: Coronary MR angiography was performed in 44 patients with suspected coronary artery disease at a 1.5 Tesla System (Intera, Philips Medical Systems) (a) with and (b) without continuous administration of intravenous nitroglycerin at a dose rate of 2.5 mg/h, using an ECG gated gradient echo sequence with real-time navigator correction (turbo field echo, in-plane resolution 0.70 x 0.79 mm(2), acquisition window 80 ms). Equivalent segments of the coronary arteries in the sequences with and without nitroglycerin were evaluated for visualized vessel length and diameter, qualitative assessment of visualization using a four point grading scale and detection of stenoses > 50 %. Catheter coronary angiography was used as a gold-standard. RESULTS: No significant differences were found between scans with and without nitroglycerin as to average length of the contiguously visualized vessel length (p > 0.05) and diameter (p > 0.05). There was also no significant difference in the coronary MR angiography with and without nitroglycerin in the average qualitative assessment score of the visualization of LM, proximal LAD, proximal CX, and proximal and distal RCA (2.1 +/- 0.8 and 2.2 +/- 0.7; p > 0.05). Sensitivity (77 % [17/22] vs. 82 % [18/22] p > 0.05) and specificity (72 % [13/18] vs. 72 % [13/18] p > 0.05) for the detection of coronary artery stenosis also did not differ significantly between scans with and without intravenous administration of nitroglycerin. CONCLUSION: Administration of nitroglycerin does not improve visualization of the coronary arteries and detection of coronary artery stenosis in free breathing 3D coronary MR angiography.

[High field MR imaging: magnetic field interactions of aneurysm clips, coronary artery stents and iliac artery stents with a 3.0 Tesla MR system]. / Hochfeld-Magnetresonanztomographie: Magnetische Anziehungs- und Rotationskräfte auf metallische Implantate bei 3.0 T.

PURPOSE: To evaluate magnetic field interactions of commonly used biomedical implants at 3.0 Tesla. MATERIALS AND METHODS: Fourteen aneurysm clips designed for permanent placement in intracranial aneurysms, 19 coronary artery stents and 20 iliac artery stents were evaluated in an actively shielded compact 3.0 T MR system (Intera, Philips Medical Systems, Best, The Netherlands, length of magnet 1.57 m). The magnetic deflection forces (translational movement) were evaluated as follows: The implants were suspended by a fine string and placed in the magnet bore at the location of the maximum magnetic field gradient. The translational forces F (z) were calculated from the measured angle of deflection from the vertical axis. The magnetic field-induced torque (rotational forces) was evaluated as follows: Each implant was placed in the center of the magnetic bore parallel to the static magnetic field B0 (position 0 degrees ). Any possible displacement of the implant was noted on a millimeter scale and any torque qualitatively evaluated using a 5 point grading scale (0: no torque; + 4: very strong torque). The implant was turned in steps of 45 degrees, and the procedure was repeated to encompass a full 360 degrees rotation. RESULTS: In 52 of the 53 devices tested, the deflection force (deflection angle: range 0-21 degrees, translational force: range 0-3.8 mN) was less than the gravitational force (i.e., the implant's weight). These devices (n = 52/53) did not show any alignment to or rotation in the magnetic field at any of the various 45 degrees -increment positions corresponding to a qualitative torque evaluation of grade 0/4. One device (n = 1/53), an iliac artery stent made of stainless steel (Zenith, Cook, Mönchengladbach, BRD), was found to have deflection forces (deflection angle 88 degrees translational force 299 mN) greatly exceeding the gravitational force as well as a pronounced torque (grade 4/4). CONCLUSION: Out of 53 biomedical implants evaluated for magnetic field interactions at 3.0 T, one iliac artery stent made of stainless steel was found to be potentially unsafe based on ASTM criteria. MR imaging at 3.0 Tesla may be performed safely in patients with any of the other 52 different implants evaluated in this study with respect to magnetic field translational attraction and torque.

[Prevalence and type of incidental extramammary findings in MRI of the breast]. / Häufigkeit und Spektrum von Zusatzbefunden ausserhalb des Brustdrüsenparenchyms bei MR-mammographischen Untersuchungen.

PURPOSE: To analyze prevalence and type of relevant incidental findings in patients undergoing breast MRI. MATERIALS AND METHODS: This prospective investigation consists of 1013 patients who underwent breast MRI as follow-up after breast cancer therapy, for pre-operative staging, and for screening of high-risk patients as well as for clarification of unclear clinical examinations and inconclusive conventional mammography. Prevalence and type of relevant incidental extramammary findings were recorded together with the indication of the examination. RESULTS: Incidental extramammary findings were encountered in 92 (9%) of the 1013 patients. MRI had markedly more incidental extramammary findings with the staging examinations (39.5%) and follow-up examinations (11.6%). The prevalence of incidental malignant findings was 81% in patients examined for pre-operative staging. Incidental benign and malignant findings were equally frequent in patients followed after breast cancer therapy. The incidental findings were exclusively benign in patients without a history of breast cancer. CONCLUSION: The interpretation of breast MRI should incorporate a careful analysis of the adjacent extramammary structures. Especially patients followed after breast cancer therapy can be expected to have incidental malignant findings outside the breast.

[Submillimeter 3D coronary MR angiography with real-time navigator correction in 107 patients with suspected coronary artery disease]. / Hochauflösende 3D-MR-Koronarangiographie inEcht-Zeit-Navigatortechnik: Ergebnisse aus107 Patientenuntersuchungen.

PURPOSE: To evaluate the clinical value of high-resolution coronary MR angiography (coronary MRA) in a large group of patients with suspected coronary artery disease. METHODS AND MATERIAL: 107 patients with suspected coronary artery disease underwent free-breathing coronary MRA (Intera, 1.5 T, Philips Medical Systems). To compensate for artefacts due to respiratory motion, a right hemidiaphragmatic navigator with real time-time slice correction was used. An ECG-gated, fat-suppressed, 3D segmented-k-space gradient echo sequence (in plane resolution 0.70 x 0.79 mm(2)) was used. Cardiac catheterization with selective coronary angiography was performed in all patients. Visualization of the coronary arteries (CA) was qualitatively assessed using a four-point grading scale. RESULTS: Image quality of grade 1 was achieved in 24 %, grade 2 in 48 %, grade 3 in 24 % and grade in in 4 % of patients. Based on an evaluation of the coronary MRAs of all patients (n = 107) sensitivity and specificity for the detection of stenoses > 60 % in the proximal and middle main coronary arteries were 74 % and 63 %, respectively. In coronary MRAs with good quality [grade 1 and 2, n = 77/107 (72 %)] sensitivity and specificity for the detection of coronary stenoses were 88 % and 91 %, respectively. CONCLUSION: Submillimeter 3D coronary MRA with real-time navigator correction allows high quality imaging of the proximal and middle main coronary arteries with good sensitivity and specificity for detection of stenoses > 50 % in selected patients. However, in about 28 % of patients image quality is severely impaired.

MR imaging--guided large-core (14-gauge) needle biopsy of small lesions visible at breast MR imaging alone.

PURPOSE: To report our experience with magnetic resonance (MR) imaging-guided large-core breast biopsy of lesions visible at breast MR imaging only. MATERIALS AND METHODS: Stereotactic large-core (14-gauge) needle biopsy of 78 lesions visible at MR imaging only was performed with MR imaging guidance in 59 patients. Results were validated with excisional biopsy or mastectomy in 42 lesions and with radiologic-pathologic correlation and/or follow-up MR imaging for at least 2 years in another 17 lesions. The accuracy of MR imaging--guided core biopsy was determined for those 59 lesions with established validation. The effect on patient treatment was evaluated by comparing the prebiopsy treatment plan with the ultimate treatment. RESULTS: Histologic diagnosis from core biopsy was possible in 77 (99%) of 78 lesions. In the 59 lesions with established validation, the diagnostic accuracy of MR imaging--guided core biopsy was 98% (58 of 59). Successful MR imaging--guided core biopsy findings changed treatment in 70% (54 of 77) of lesions. Difficulties were due to the unsatisfactory performance of earlier types of MR imaging--compatible biopsy guns and decreasing target visibility during intervention. CONCLUSION: MR imaging--guided large-core stereotactic breast biopsy is sufficiently accurate for obtaining histologic proof of lesions visible only at MR imaging. It can change patient treatment by reducing unnecessary surgical biopsy and can enable one-step surgery for breast cancers.

Antibodies against proteins of streptococcal hyaluronate synthase bind to human fibroblasts and are present in patients with rheumatic fever.

Antibodies directed against the streptococcal 42 kDa hyaluronate synthase and a 56 kDa auxiliary protein bound to the surface of intact human fibroblasts in vitro. Staining was most prominent during the detachment phase of mitosis. In eukaryotic plasma membranes a 52 kDa protein was recognized by the antiserum against the 56 kDa streptococcal protein. Since the cross-reacting proteins could be involved in immunological mimicry between streptococcal and human antigens leading to heart cell necrosis, the reactivity of sera from patients with rheumatic fever was compared with that of sera from healthy or streptococcal infected persons. The sera from patients with rheumatic fever showed a higher reactivity against the 56 kDa protein than those from healthy persons or from patients with an antibiotic treated streptococcal infection. This difference was not observed for the 42 kDa protein. These sera were able to lead to cell lysis in the presence of complement.

Bioptic microbiology in the differential diagnosis of enterocolitis.

Parameters in the differential diagnosis of enterocolitis have been poorly evident for many years. Development and profitable employment of endoscopic instruments were the first step towards advancing the diagnostic facilities in inflammatory bowel disease. The microbiologic examination of mucosal biopsies creates a new diagnostic dimension, and it distinctly seems to increase the diagnostic sensitivity for pathogens. Within fifteen months 152 patients admitted to the gastroenterologic unit with acute, or symptoms of exacerbated, bowel disease were examined for the aetiologic agents. Compared with former reports, idiopathic inflammatory bowel disease (IIBD) such as Crohn's disease (32.2%) and ulcerative colitis (18.4%) were decreased. Infectious colitis (22.3%), mostly Campylobacter or Yersinia infections, was, sometimes exclusively, diagnosed by bioptic microbiology, non-classifiable forms of colitis (21.7%), and rare forms (5.4%) were diagnosed more often. It proved to be important that IIBD was frequently superinfected by Campylobacter, Yersinia and Chlamydia, and the differential diagnosis was complicated, since these microorganisms can mimic IIBD. The results suggest that coloileoscopy combined with bioptic microbiologic investigation additional to faecal samples should include a search for Campylobacter and Yersinia. It appears indispensable that the final diagnosis "Crohn's disease" or "ulcerative colitis" should be confirmed by sequential coloileoscopy and microbiologic examination.

[Blood serum levels in mother and child after oral administration of doxycycline ante partum (author's transl)]. / Blutserumspiegel bei Mutter und Kind nach oraler Verabreichung von Doxycyclin ante partum

After the administration of a single dose of doxycycline to 14 pregnant women shortly before delivery, different concentrations of doxycycline were measured in blood from the umbilical cord after parturition, up to a maximum 54% of the maternal serum concentration. 9 hours after the application of 200 mg doxycycline, a serum level could no longer be detected in the blood from the cord of the fetuses. Serum levels were still demonstrable in the maternal blood 24 hours after the administration. The level of the concentration of doxycycline in the fetal blood was dependent on the level of the concentration of doxycycline in the maternal blood.