On the incorporation of iron into hexagonal barium titanate: II. Magnetic moment, electron paramagnetic resonance (EPR) and optical transmission.

Systematic measurements of the magnetic moment in dependence on temperature and magnetic field of hexagonal 6H-BaTiO3 + 0.04 BaO + x/2 Fe2O3 (0.005 ⩽ x ⩽ 0.05) ceramics were performed to study the influence of Fe ions on the magnetic properties. While the samples show Curie-Weiss paramagnetism for Fe concentrations ⩽1.0 mol%, antiferromagnetic interactions become manifest for 2.0 and 5.0 mol% iron. With increasing Fe content the antiferromagnetic interaction, which is assumed to be caused by a superexchange mechanism [Formula: see text], becomes stronger. At external magnetic fields smaller than 1 T a further, ferromagnetic interaction between Fe3+ ions is detected below 200 K. The interactions between Fe3+ ions in the samples with 2.0 and 5.0 mol% iron are also manifest in the EPR spectra by numerous lines with low intensity. Q-band EPR investigations of 5.0 mol% Fe doped single crystals confirm the existence of only one type of Fe3+-VO associates in the samples.

On the incorporation of iron into hexagonal barium titanate: I. electron paramagnetic resonance (EPR) study.

Electron paramagnetic resonance (EPR) investigations of BaTiO3 + 0.04 BaO + x/2 Fe2O3 (0.007 ⩽ x ⩽ 0.05) ceramics and BaTi0.98Fe0.02O3 single crystals were performed to study the incorporation of Fe ions in the hexagonal 6H-BaTiO3 lattice and their defect properties. The samples were characterized by x-ray diffraction and wavelength-dispersive x-ray electron probe microanalysis. EPR spectra were recorded both in X- and Q-bands at room temperature. Angle-dependent single crystal EPR investigations and simulations of the ceramic powder EPR spectra revealed three different centers, which can be attributed to Fe3+ ions incorporated on crystallographically different Ti sites. Only one of them was already known before. Two spectra with axial symmetry belong to isolated Fe3+ ions incorporated at Ti(1) sites (exclusively corner-sharing oxygen octahedra) and Ti(2) sites (face-sharing octahedra). The difference of their spectral parameters arises from the different trigonal distortions of the two types of octahedra. The third spectrum has orthorhombic symmetry and is caused by Fe3+ centers associated with a nearest-neighbor charge-compensating oxygen vacancy. A model for the location of this associate is proposed.

Defect properties of cobalt-doped hexagonal barium titanate ceramics.

X-ray diffraction (XRD) patterns, electron paramagnetic resonance (EPR) powder spectra (9 and 34 GHz) and the magnetic susceptibility of BaTiO3 + 0.04 BaO + x/2 Co2O3 (0.001 â©½ x â©½ 0.02) ceramics were studied to investigate the incorporation of Co ions in the BaTiO3 lattice and their valence states as well as the development of the hexagonal phase (6H modification) in dependence on doping level x and sintering temperature Ts. At Ts = 1400 °C the 6H modification begins to occur at a nominal Co concentration x of about 0.001 and for x > 0.005 the samples are completely hexagonal at room temperature. Two different EPR spectra were observed in the 6H modification of BaTiO3, which were both assigned to paramagnetic Co(2+) ions located at the two crystallographically non-equivalent Ti sites in 6H-BaTiO3. The EPR g tensor values as well as the molar paramagnetic susceptibility, measured in the temperature range 5 K-300 K at a magnetic field of 9 T, were analyzed in the framework of the ligand field theory using the program CONCORD. The combination of EPR and magnetic measurements reveals that in air-sintered 6H BaTiO3, the incorporated Co occurs as a mixture of paramagnetic Co(2+) and diamagnetic Co(3+) ions, whereas in samples annealed in reducing atmosphere the majority of Co is in the divalent state. The occurrence of Co(4+) can be excluded for all investigated samples. The sample color caused by Co(2+) and Co(3+) ions is beige/light yellow and dark grey/black, respectively. The majority of the Co(2+) ions substitutes Ti in the exclusively corner-sharing oxygen octahedra possessing nearly cubic symmetry. The corresponding ligand field parameter [Formula: see text] amounts to about -28 000 cm(-1) (Wybourne notation, 10Dq ≈ 20 000 cm(-1)). In the reduced samples nearly 5% of the detected Co(2+) ions occupy the Ti site in the face-sharing oxygen octahedra, which are significantly trigonally distorted. The negative sign of the obtained ligand field parameter [Formula: see text] ≈ -7300 cm(-1) reflects a compression of this octahedron in direction of the hexagonal c-axis.

Paramagnetic resonance study of nickel ions in hexagonal barium titanate.

X-ray diffraction patterns and electron paramagnetic resonance (EPR) powder spectra (9 and 34 GHz) of BaTiO(3) + 0.04 BaO + xNiO (0.001 ≤ x ≤ 0.02) ceramics were studied to investigate the incorporation of Ni ions and their valence states as well as the development of the hexagonal phase (6H modification) of Ni-doped material with respect to doping level x and sintering temperature T(s). The 6H modification begins to occur at a nominal Ni concentration of between x = 0.005 and 0.01 and its percentage increases with increasing sintering temperature. Ni-doped BaTiO(3) with x = 0.02 sintered at T(s) = 1400 °C is completely hexagonal. In the 3C modification, present in as-sintered ceramics with low nominal Ni concentrations, only one type of Ni EPR spectrum was observed. By comparing its principal values of the g tensor with data of single-crystal measurements the clear assignment of this spectrum to Ni(+) ions is possible. Two different EPR spectra with orthorhombic g tensors are observed in the as-sintered samples with hexagonal crystal structure. These spectra were assigned to Ni(3+) ions with the electron spin S = 1/2 (electron configuration 3d(7), strong crystal field) substituted at Ti lattice sites corresponding to the different distorted octahedra of the hexagonal modification. Measurements of the concentration reveal that only 5% of the doping material is in the state Ni(3+). No EPR spectra of Ni(2+) ions have been detected in either 3C or 6H modification in as-sintered ceramics. Therefore, we suppose that the main part of nickel is substituted as Ni(4+) ions on Ti(4+) lattice sites. After heat treatment of the samples in H(2)/Ar atmosphere a single-line spectrum with g = 2.21 ± 0.01 at room temperature has been observed which is assigned to metallic Ni or antiferromagnetically coupled Ni(2+) ions in secondary phases segregated at grain boundaries or triple points.

Jahn-Teller effect in BaTiO(3):Cr(5+): an electron paramagnetic resonance study.

Electron paramagnetic resonance (EPR) spectra of Cr(I)(5+) defects incorporated on Ti(4+) sites in single-crystal and powdered ceramics of BaTiO(3) were investigated in the temperature range 50-220 K at 34 GHz (Q band). Single-crystal and powder measurements allow the unambiguous determination of the full g tensor in the ferroelectric rhombohedral phase whereas in the orthorhombic phase only the determination of the principal values of the Cr(I)(5+) g tensor was successful. The [Formula: see text] Jahn-Teller effect stabilizes the vibronic ground state of the 3d(1) electron of the Cr(I)(5+) ion and leads to a tetragonally compressed defect-O(6) octahedron with the point symmetry D(4h). The spontaneous electrical polarization present in the ferroelectric phases of BaTiO(3) appears as a further perturbation. The quadratic field effect reduces the D(4h) symmetry of the Cr(I)(5+) defect centre and produces an additional g tensor breaking the tetragonal symmetry of the Zeeman term. For symmetry reasons one of the principal axes of the rhombic g tensor must be directed along one [Formula: see text] direction. The angles of the other two principal axes with respect to the [Formula: see text] axes are dependent on the absolute value of the spontaneous polarization. The difference in the temperature behaviour of the single-crystal and powder spectra can be explained by the presence of internal stress in the grains of the ceramic samples which increases the JT energy of the 3d(1) electron.

The influence of domains on tetrahedrally coordinated Cr(5+) in ferroelectric BaTiO(3): an electron paramagnetic resonance study.

Electron paramagnetic resonance (EPR) spectra of quasi-tetrahedrally coordinated Cr(5+) ions (named Cr(II)(5+) in contrast to the octahedrally coordinated Cr(I)(5+)) in powdered ceramic samples of BaTiO(3) were investigated in the temperature range 50-220 K at 9.4 and 34.0 GHz (X and Q band). At 50 K, in the ferroelectric low-temperature phase with rhombohedral symmetry, two peaks in the powder spectrum of the 1/2-spin Cr(II)(5+) centre show a frequency-dependent doublet splitting which is explained assuming the existence of two Cr(II)(5+) centres with slightly different g tensors. The spontaneous polarization in the ferroelectric domains induces changes in the peak positions in the spectra and generates alignment effects of the off-centred Cr(5+) ions. These effects are caused by the linear coupling of the electric dipole moment, associated with the off-centred Cr(5+) ion within the octahedron of surrounding O(2-) ions, and the polarization field. At 75 K a dynamic reorientation of the defect ions among the possible positions in the unit cell broadens the powder peaks. Above 150 K only an isotropic single-line spectrum is observed, the line width of which increases with rising temperature.

[Radioiodine therapy of functional autonomy of the thyroid gland. Treatment results in view of pretreatment scintigraphic diagnosis and early response of triiodothyronine levels to treatment]. / Die Radiojodtherapie der funktionellen Schilddrüsenautonomie. Behandlungsergebnisse unter Berücksichtigung der Autonomieform und des frühen posttherapeutischen Trijodthyroninspiegels.

AIM: The goal of this retrospective study was to evaluate the results of radioiodine therapy of thyroid autonomy with respect to the underlying scintigraphic pattern, administered I-131 doses and pretherapeutic Tc-99m and I-131 uptake. Furthermore, early post-therapeutic free triiodothyronine (FT3) levels were measured during the first 6 weeks after radioiodine therapy with respect to a FT3-increase. PATIENTS AND METHODS: Thyroid autonomy in 632 patients was followed for at least 3 months (mean 10.9 months). The patients were divided into several groups based on scintigraphic pattern of unifocal (UA), a multifocal (MFA), a focal/disseminated (FDA) and a disseminated (DA) autonomy. The early effects of therapy on thyroid function were assessed by evaluation of FT3 values of 786 patients during the 1st, 2nd, 3rd, 4th and 6th week after therapy. RESULTS: Successful elimination of thyroid autonomy as defined by normalization of FT3 and TSH levels was observed in 92.1% (582/632) of the patients. In 2.2% (14/632) of the patients, immunogenic hyperthyroidism following I-131 therapy was observed. There was no significant difference in the success rates in patients with UA and MFA of 94.9% and 96.1%, respectively, using similar target doses based on the amount of autonomous tissue. The success rate in MFA (96.6%) was similar if target dose was calculated based on the volume of the whole thyroid gland. Compared to MFA (96.6%), however, FDA and DA were associated with significantly lower success rate with 82.7% and 75.5%, respectively, although the target doses were not significantly different. Considering the quantitative Tc-99m uptake prior to therapy, there was no significant difference in the success rate for Tc-99m uptake < or = 3% and > 3%, while the success rate in patients with I-131 uptake of < or = 50% was significantly higher (p = 0.032) than in those with an uptake of > 50%. The determination of FT3 levels during the first 6 weeks after radioiodine therapy revealed a dependence of the FT3 decrease and FT3 increase on the scintigraphic pattern and thyroid function. Patients with FDA and DA with hyperthyroidism showed an increase of FT3 (> 2 to 14.7 pmol/l) in 11 to 18% of the cases, during the first 2 weeks after therapy which occurred significantly more frequently in patients with FDA and DA than in UA and MFA. A similar increase in FT3 level in patients with FDA and DA compared to patients with UA and MFA was observed in 317 patients with euthyroid pretherapeutic hormone levels. A decrease in FT3 level following radioiodine therapy was observed significantly more often and earlier in patients with UA and MFA with hyperthyroid values than in patients with FDA and DA during the first 6 posttherapeutic weeks. Concerning patients with euthyroid FT3 levels, the decrease in FT3 level was observed significantly more frequently in patients with UA and MFA only after 6 weeks following radioiodine therapy. CONCLUSION: In contrast to the multifocal autonomy (MFA), the target dose of 150 to 200 Gy based on total thyroid volume did not result in a comparably high success rate of approximately 95% in disseminated and focal/disseminated types of thyroid autonomy. Therefore, an increase of target dose of 200 to 300 Gy is recommended. The transient FT3 increase particularly observed in FDA and DA in the first weeks following radioiodine therapy makes short-term controls of thyroid function necessary, especially in patients with cardiac risk, in order to initiate necessary therapy.

[Clinical relevance of I-123/I-131-MIBG scintigraphy in intestinal carcinoid tumors]. / Klinische Relevanz der I-123/I-131-MIBG-Szintigraphie bei intestinalen Karzinoiden.

AIM: Of this retrospective study was to determine the value of MIBG-scintigraphy in patients with intestinal carcinoids dependent on histological, clinical, and biochemical parameters. METHODS: In 15 patients uptake in carcinoid tumors and metastasis was correlated with location of the primary tumor, intra- and extrahepatic tumor masses, histology, immunhistochemistry, neuroendocrinological markers, and clinical symptoms. RESULTS: High uptake was to be seen almost only in tumor masses of primary tumors located in the terminal ileum. There also was a positive correlation with clinical symptoms for carcinoids and urinary 5-HIAA level. No correlation between MIBG uptake and tumor masses, histology, and most of the immunhistochemical and neuroendocrinological markers could be found. CONCLUSION: There is a limited indication for MIBG-scintigraphy in follow up of intestinal carcinoids. In patient with proven uptake MIBG scintigraphy is suitable for long-term follow up and therapy monitoring.

[Occurrence of immune hyperthyroidism after radioiodine therapy of autonomous goiter]. / Zum Auftreten einer Immunhyperthyreose nach Radiojodtherapie von Schilddrüsenautonomien.

AIM: The goal of the study was to examine the prevalence of Graves' disease following I-131 treatment of autonomous goiter with special regard to pretreatment scintigraphic patterns. PATIENTS AND METHOD: Pre- and posttreatment in-vitro and in-vivo parameters were studied in 375 consecutive patients treated with I-131 therapy for nodular or diffuse autonomous goiter. All patients included were within ambulant control for at least 2.5 months following treatment. According to the pretreatment Tc-99m pertechnetate scan 59% (220/375) had multifocal (MF), 23% (86/375) unifocal (UF), 10% (38/375) mixed focal-disseminated (FD) and 8% (31/375) disseminated (D) scintigraphic patterns. RESULTS: In 93.9% (352/375), the autonomous tissue was totally, in 2.1% (8/375) partially and in 1.6% (6/375) insufficiently eliminated. In 2.4% (9/375) a relapse of hyperthyroidism was observed 2 to 10 months following I-131 therapy. In 8 patients a relapse of hyperthyroidism was accompanied or followed by an elevation of the previously non-elevated TSH-receptor antibody (TRAb) level and in 1 patient by an TRAb increase to the upper borderline range implicating Graves' disease. With the prevalence of Graves' disease following I-131 therapy a statistically significant difference in pretreatment Tc-99m pertechnetate scintigraphic patterns was found: 0% of unifocal (0/86) or multifocal (0/220), however 18% (7/38) of focal-disseminated and 7% (2/31) of disseminated scintigraphic patterns. From the 366 patients without relapse of hyperthyroidism 2 (MF) had elevated pre- and posttreatment TRAb levels and 3 (D) had elevated TRAb levels for the first time after I-131 therapy. CONCLUSION: There is a low overall prevalence (2.4%) of Graves' disease following I-131 therapy for nodular or diffuse autonomous goiter. However, the prevalence of posttreatment Graves' disease is highly dependent upon pretreatment scintigraphic patterns exhibiting focal-disseminated or disseminated patterns.

[Early detection of morphologic-functional changes in the airways using a simple method of inhalation scintigraphy]. / Früherkennung von morphologisch-funktionellen Veränderungen der Atemwege durch eine einfache Methode der Inhalationsszintigraphie.

In order to validate a method of inhalation scintigraphy with 99mTc-labeled human serum albumin in the early diagnosis of morphologic-functional changes of the airways 35 volunteers and patients (12 healthy non-smokers and smokers each, 11 patients with bronchitis) were studied. Deposition of the aerosol immediately after inhalation was calculated quantitatively by a ROI technique and qualitatively (scoring of central deposition, homogeneity, and recognizability of lung outline). Additionally, the regional clearance of the inhaled aerosol was determined by continuous lung imaging up to 60 min (mainly regional mucociliary removal rates). Discrimination between healthy volunteers and patients with bronchitis was possible by means of deposition patterns immediately after inhalation. On the other hand, no differences could be recognized in this way between healthy non-smokers and smokers. Regional mucociliary removal was higher in non-smokers than in smokers, but there was no difference between smokers and patients with bronchitis.

The efficacy of nifedipine and acebutolol in coronary artery disease assessed by radionuclide ventriculography.

The efficacy of a fixed combination of 10 mg nifedipine and 100 mg acebutolol was tested in 21 patients with angiographically proven coronary artery disease (CAD). Ejection fraction (EF), emptying and filling rate (VS and VD), and end-systolic volume (ESV) were assessed by means of radionuclide ventriculography at rest and during exercise prior to as well as 1 hour and 5 hours following oral drug application. Whereas exercise-induced worsening of cardiac function had been documented in all the patients prior to medication, EF and ESV improved significantly after drug administration.

[Age-related heart function in patients with healthy hearts]. / Altersabhängigkeit der Herzfunktion bei Herzgesunden.

Left ventricular function was investigated at rest and during submaximal exercise in 191 healthy subjects, including 46 women, by means of radionuclide ventriculography (RNV). As global parameters of heart function, ejection fraction (EF) and maximal rates of volume change during systole (VS) and diastole (VD) as well as endsystolic volume (ESV) were determined. These parameters were calculated for four age groups with mean ages of 32, 45, 55, and 64 years, respectively. At rest, heart rate (HR), EF, VS, and ESV were not significantly different in all age groups, whereas VD decreased with increasing age from 3.3 +/- 0.6 s-1 to 2.6 +/- 0.6 s-1. During exercise, HR, EF, VS, and VD increased in all groups, but less in the elderly. The smaller increase of EF and VD could be accounted for by HR alone. VS was both HR- and age-dependent. The age dependence of VD (at rest) and VS (under exercise) may reflect a reduction of myocardial compliance with increasing age. Differences of EF and VS with respect to sex were not observed, whereas VD was slightly lower in males.

[Experimental studies and clinical aspects of cold-preserved allogenic spongiosa]. / Experimentelle Untersuchungen und klinische Aspekte zur Kältekonservierung allogener Spongiosa.

Different temperatures, freeze techniques, and durations of storage for cryopreservation of allogeneic spongious bone were studied in an experimental model. Low temperatures (-70 degrees C to 196 degrees C) without cryoprotectants proved to be favorable in micromorphological as well as scintigraphic analyses. These transplants seem to be equivalent to fresh autologous transplants - at least in animal experiments. Medium-term durations of storage (3 mo) at low temperatures yield the best osteoinductive capacity. Long term storage (12 months) and radiosterilization reduce the quality of the allogeneic bone. The clinical results in 495 transplantations of cryopreserved allogeneic spongious bone confirm the experimental findings.

[Age and sex dependence of tubular kidney clearance in childhood]. / Alters- und Geschlechtsabhängigkeit der tubulären Nierenclearance im Kindesalter.

Nuclear medicine methods have gained wide-spread use for quantitative determination of renal function, but normal values related to age and sex are often not available, especially in children. Since pediatric clearance studies in our clinic are carried out routinely by means of I-123-OIH (ortho-iodo-hippurate), OIH-clearance determinations were performed in 33 children considered to have normal renal function. Within the investigated age of 3,5-15 years no significant correlation of tubular renal clearance with age and no difference between both sexes was found, the mean value +/- SD being 577 +/- 88 ml/min/1,73 m2 surface area. Comparing all age related values known from literature, our values from children and adults fit in quite well.

[Radionuclide ventriculography in coronary heart disease]. / Radionuklid-Ventrikulographie bei koronarer Herzkrankheit.

Heart function can be investigated non-invasively and without risk for the patient by means of radionuclide ventriculography. Coronary artery disease can be diagnosed with high sensitivity and distinguished from other diseases of the heart with high specificity by typical alterations of heart function as seen in rest and/or exercise scans. The hemodynamic significance of invasively proven stenoses of coronary arteries can de demonstrated and the function and functional capacity of surviving vital myocardium after myocardial infarction can be quantified scintigraphically. The efficacy of medical and surgical therapy can be documented and the course of disease can be followed up.

[Value of skeletal scintigraphy in the follow-up of breast cancer]. / Die Bedeutung der Skelettszintigraphie in der Nachsorge des Mammakarzinoms.

In a retrospective study of 728 patients with breast cancer up to 3 years after primary treatment skeletal scintigraphy yielded 15.8% (n = 115) bone metastases. By scintigraphic differentiation between a typical and an untypical pattern of bone metastasis a diagnostic accuracy of 99% was found. Depending on the local stage of tumor the rate of osseous metastases rises with increasing tumor size and with the extent of metastatic involvement of the lymph nodes. The frequency of bone metastasis proved to be also dependent on the histological type of tumor; it was highest in scirrhous carcinomas. By evaluating the scintigraphic behaviour of skeletal metastases under treatment in 122 patients we revealed an obvious decrease of metastatic deposits or complete normalization in 11.5% (n = 14), an unchanged finding in 32% (n = 39) and a progression of metastasis in 56.5% (n = 69). Therefore scintigraphic bone imaging in follow-up of breast cancer can be recommended for early detection of osseous metastases and for assessing the response of skeletal metastases to treatment.

In vivo/in vitro labeling of red blood cells with 99mTc.

Red blood cells (RBC) were labeled with 99mTc in vitro after in vivo pretreatment with a stannous solution. The whole in vivo/in vitro procedure took 30-40 min. Pretinning was carried out by injection of either 6 mg DTPA and 0.6 mg Sn++ (Sn-DTPA) or 5 mg pyrophosphate and 0.7 mg Sn++ (Sn-PYP). The results of 1,356 patients were evaluated. The labeling yield was 89.7% (mean) after pretinning with Sn-DTPA and 88.2% following Sn-PYP pretreatment, the median values being 94% and 92%, respectively. The new method was successfully used in over 2,000 patients who had a radionuclide-ventriculography and in 38 patients studied for localization of occult gastrointestinal bleeding. Adverse side effects have never been observed.