No abstract

In a prospective, randomized study we examined the influence of prophylactic short-term thyrostatic therapy on thyroid iodine metabolism in patients with euthyroid autonomy undergoing elective coronary angiography. From a total of 1177 patients, 51 fulfilled the criteria of euthyroid autonomy before coronary angiography (negative thyrotropin-releasing hormone test, 10-min uptake of at least 1.2%, 99mTc and no elevation of free thyroxine and free triiodothyronine indices) and were randomized into three groups: group 1 (N = 17) received 20mg/day of thiamazole and group 2 (N = 17) received 900 mg/day of sodium perchlorate; thyrostatic therapy was begun on the day before angiography and continued for 14 days; group 3 (N = 17) served as controls without treatment. Parameters of thyroid function-free thyroxine (FT4) index and free triiodothyronine (FT3) index, thyrotropin (TSH) and delta-TSH urine iodine excretion and 99mTc uptake were determined before and 30 days after coronary angiography. At the end of the study the mean FT4 index and FT3 index were elevated significantly in the control group compared with baseline values, but were still within the normal range. In contrast, the mean FT4 index and FT3 index remained unchanged in the treated groups. Four mild cases of hyperthyroidism were observed at the end of the study: two cases in the control group and one case in each of the treated groups. Thyrotropin suppression, urine iodine excretion and 99mTc uptake differed significantly between the treated groups and the control group. In the treated groups TSH suppression, urine iodine excretion and 99mTC uptake remained unchanged 30 days after coronary angiography compared with baseline values. In the control group the degree of TSH suppression and the level of urine iodine excretion increased (about twofold) significantly after coronary angiography, whereas 99mTc uptake decreased significantly (ca. 50%). In conclusion, short-term prophylactic thyrostatic therapy seems to have a protective effect against iodine excess in patients with euthyroid autonomy. However, mild hyperthyroidism could not be prevented in some cases. Probably a combination therapy of thiamazole and perchlorate would be more effective.

We present THz ultrashort pulse detection by a photoconductive antenna array consisting of 16 photoconductive antennas. The efficient excitation of the photoconductive antennas has been realized by a microlens array which generates 16 single spots from the exciting fs-laser beam. This combination of optoelectronics and microoptics improves the detection efficiency by an order of magnitude in comparison to an excitation by a line focus.

Several novel types of detectors for the measurement of electromagnetic radiation in the THz spectral range are described. Firstly, detectors based on pyroelectric foil coated with different absorbers have been developed focusing on the following features: high accuracy due to well-characterized absorption, high sensitivity, large area absorbers and frequency and polarization independence. A three-dimensional design with five absorptions gave an overall absorption of more than 98 %. Secondly, detectors based on pyroelectric foils with thin metal layers were realized. An absorption of 50 % can be obtained if the thickness of the layers is carefully adjusted. According to electromagnetic theory this degree of absorption is independent of the polarization and frequency of the radiation in a wide range from at least 20 GHz to 5 THz. The third type of detector is based on a new type of volume absorber with a polished front surface and a gold-coated back side. It is the absorber of choice of the standard power detector for disseminating the spectral power responsivity scale. This standard detector allows the application of a physical model to calculate its spectral responsivity in the range from 1 THz to 5 THz if the detector has been calibrated at one single frequency. Finally, a THz detector calibration facility was set up and is now in operation at PTB to calibrate detectors from customers with an uncertainty as low as 1.7 %.

We report on, to the best of our knowledge, the first absolute terahertz (THz) power measurement of a photoconductive emitter developed for time-domain spectroscopy (TDS). The broadband THz radiation emitted by a photoconductor optimized for the excitation with 1550-nm femtosecond pulses was measured by an ultrathin pyroelectric thin-film (UPTF) detector. We show that this detector has a spectrally flat transmission between 100 GHz and 5 THz due to special conductive electrodes on both sides of the UPTF. Its flat responsivity allows the calibration with a standard detector that is traceable to the International System of Units (SI) at the THz detector calibration facility of PTB. Absolute THz power in the range from below 1 μW to above 0.1 mW was measured.

The Metrology Light Source (MLS)—the dedicated electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB), designed for metrology and technological applications in the spectral range from the far IR to the VUV—started user operation in April 2008. The MLS is used as a primary source standard from the NIR to the VUV spectral region and is therefore equipped with all the instrumentation necessary to measure with low uncertainty the storage ring parameters and the geometrical parameters needed for the calculation of the spectral photon flux according to the Schwinger theory. It can be operated at any electron beam energy between 105 MeV and 630 MeV and at electron beam currents varying from 1 pA (one stored electron) up to 200 mA, which allows conditions to be tailor-made for special applications.

The metrology institute in Germany, the Physikalisch-Technische Bundesanstalt (PTB), calibrates the spectral responsivity of THz detectors at 2.52 THz traceable to International System of Units. The Terahertz detector calibration facility is equipped with a standard detector calibrated against a cryogenic radiometer at this frequency. In order to extend this service to a broader spectral range in the THz region a new standard detector was developed. This detector is based on a commercial thermopile detector. Its absorber was modified and characterized by spectroscopic methods with respect to its absorptance and reflectance from 1 THz to 5 THz and at the wavelength of a helium-neon laser in the visible spectral range. This offers the possibility of tracing back the THz power responsivity scale to the more accurate responsivity scale in the visible spectral range and thereby to reduce the uncertainty of detector calibrations in the THz range significantly.

The national metrology institute of Germany, the Physikalisch-Technische Bundesanstalt (PTB), together with the company Sensor and Lasertechnik (SLT), develops pyroelectric detectors for radiation in the terahertz (THz) spectral range. The intention of this development is to deliver a highly sensitive, accurately calibrated detector for power measurement in the power range of time-domain spectroscopy (TDS) systems. This work reports about a large-area thin-film pyroelectric (TFP) detector applicable within a wide spectral range from 300 GHz to 30 THz and its radiometric characterization by PTB's THz radiation sources. Applying coherent synchrotron radiation from the Metrology Light Source (MLS), laser radiation from a molecular gas laser and blackbody radiation from a water-heated blackbody to this detector reveal its potential to be capable of spanning an even wider THz frequency range than covered by TDS systems. To demonstrate this, its spectral responsivity was measured at different frequencies between 300 GHz and 30 THz by means of those three THz radiation sources.