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PubMed1982

Excitation functions for 3He-Particle induced nuclear reactions on 76Se, 77Se and natSe: possibilities of production of 77Kr.

Thin selenium films were prepared by cathodic deposition on aluminium foils. The Al-Se-Al sandwich stacks were used for measurement of the excitation functions of the 76Se(3He,2n)77Kr, 77Se(3He,3n)77Kr and natSe(3He,xn)77Kr reactions up to 3He-particle energy of 36 MeV. Excitation functions were also measured for the competing reactions 76Se(3H,3n)76Kr, 76Se(3He,pn)77Br, 76Se(3He,p2n)76Br, 76Se(3He,p3n)75Br, 76Se(3He, alpha)75Se, 77Se(3He,n)79Kr, 77Se(3He,4n)76Kr, 77Se(3He,pn)78Br, 77Se(3He,p2n)77Br, 77Se(3He,p3n)76Br, 77Se(3He, alpha n)75Se, natSe(3He,xn)79Kr and natSe(3He,xn)76Kr. Thick target yields were calculated for the formation of krypton and bromine isotopes in 3He-induced reactions on 76Se and 77Se and for krypton isotopes in reactions on natural selenium. The possibilities of production of 77Kr using 3He-particle induced reactions on 76Se, 77Se and natSe were investigated. From the viewpoint of yield and purity, for the production of 77Kr the reactions 76Se(3He,2n)77Kr and 77Se(3He,3n)77Kr were found to be very suitable, the former at low energies and the latter at relatively higher energies. In the case of 76Se(3He,2n)77Kr reaction, a target thickness corresponding to E3Hc = 25 leads to 15 MeV leads to a theoretical thick target yield of 7.5 mCi 77Kr/micro Ah; the 76Kr impurity at EOB amounts to 0.45%. In the case of 77Se(3He,3n)77Kr reaction, on the other hand, for a target thickness corresponding to E3Hc = 36 leads to 15 MeV the calculated thick target yield of 77Kr is 11.5 mCi/micro Ah and the levels of impurities 79Kr and 76Kr at EOB amount to 0.35 and 0.36% respectively.

Helium↗
PubMed1983

Production of 77Kr and 79Kr for medical applications via proton irradiation of bromine: excitation functions, yields and separation procedure.

Excitation functions were measured for the formation of both 77Kr and 79Kr by interaction of protons with bromine of natural isotopic composition. The theoretical yields are 62.8 mCi/muAh for 77Kr in the energy range from 45 to 32 MeV, with 1.5% 76Kr and 11.7% 79Kr impurities, and 14.9 mCi/muAh for 79Kr in the energy range of 45 to 0 MeV, respectively. The experimental yield after dry distillation separation of the krypton isotopes from irradiated NaBr targets, lies between 40 and 60% of the theoretical ones. Below the melting point of NaBr, krypton is released by diffusion, caused by lattice defects in the target material.

Bromine↗
PubMed2005

Is 2-cyclopropylpropene really gauche?

Infrared spectra of gaseous and solid 2-cyclopropylpropene (2-CPP, c-C3H5C (CH3)CH2) have been recorded from 3500 to 40 cm-1, and Raman spectra (3200-150 cm-1) of the liquid as well as mid-infrared spectra of 2-CPP in liquid krypton solution (from -105 to -150 degrees C) were also obtained. Ab initio calculations, with basis sets up to 6-311+G(2df, 2pd), were carried out for this molecule, using the restricted Hartree-Fock (RHF) approach, with full electron correlation by the perturbation method to second order (MP2(full)) and density functional theory (DFT) by the B3LYP method. The combination of the experimental and computational results (particularly with the higher basis sets) unequivocally identifies the more stable conformer of 2-CPP as the trans form, with the gauche rotamer higher in energy, but also stable. The cis structure of this compound is not observed experimentally, and is predicted by the computational approaches to be a transition state. By studying the temperature variation of two well-resolved sets of conformational doublets of 2-CPP dissolved in liquid krypton, an average enthalpy difference between conformers of 182+/-18 cm-1 (2.18+/-0.22 kJ mol-1) has been determined, with the trans conformation lower in energy in the fluid states, and the sole conformer present in the polycrystalline solid phase. This enthalpy difference corresponds to an ambient temperature conformational equilibrium in the fluid phases of 2-cyclopropylpropene containing approximately 55+/-2% of the more stable trans rotameric form. A complete vibrational assignment for the trans conformer of 2-CPP is given, and many of the bands of the gauche rotamer have also been assigned. Structural parameters, dipole moments, and rotational constants for this molecule have been calculated at the MP2(full)/6-311+G(d,p) level, and these results--as well as the results from the experimental studies--are compared to similar quantities in related compounds.

Alkenes↗
PubMed1980

Lung imaging with radioaerosols for the assessment of airway disease.

Aerosol inhalation lung scans offer distinct advantages in the evaluation of airways and the qualitative distribution of ventilation. The sensitivity in detecting mild obstructive disease is similar to that of xenon washout and both probably surpass standard pulmonary function tests that measure total rather than regional ventilation. Although imaging studies using krypton gas are ideal for assessment of rapidly ventilated space, krypton's short half-life precludes its usefulness for demonstrating air trapping. Neither 133Xe nor 81mKr gas demonstrates sites of airway abnormality as aerosol does. Aerosols are ideal for the general nuclear medicine practice in community hospitals because of their convenience, cost effectiveness, and information yield. Current technique using same-day multiple-view aerosol scans after a preliminary perfusion scan, makes use of the most logical diagnostic scheme in the vast majority of patients with chest complaints, since a normal perfusion scan often eliminates the need for a ventilation scan.

Adult↗
PubMed2006

Unusual photochemical C-N bond cleavage in the novel methyl 2-chloro-3-methyl-2H-azirine-2-carboxylate.

The structure, preferred conformers, vibrational spectrum, and photochemical behavior of the novel azirine, methyl 2-chloro-3-methyl-2H-azirine-2-carboxylate (MCMAC) were investigated in low-temperature matrixes and in the neat solid amorphous state by infrared spectroscopy and quantum-chemical calculations. Two conformers of the compound were observed in argon, krypton, and xenon matrixes, in agreement with the DFT(B3LYP)/6-311++G(d,p) and MP2/6-311++G(d,p) theoretical calculations. Both conformers were found to exhibit the carboxylic ester group in the cis conformation, differing in the arrangement defined by the O=C-C-Cl dihedral angle (cis and trans, for Ct and Cc forms, respectively). The Ct conformer was found to be the most stable conformer in the gaseous phase as well as in both argon and krypton matrixes, whereas the more polar Cc conformer became the most stable form in the xenon matrix and in the neat solid amorphous phase. In situ broadband UV (lambda > 235 nm) excitation of matrix-isolated MCMAC led to azirine ring C-C and C-N bond cleavages, the latter process corresponding to the most efficient reaction channel. The photochemical cleavage of the C-N bond had never been previously observed in the case of aliphatic 2H-azirines. Two electron withdrawing substituents (methoxycarbonyl group and chlorine atom) are connected to the azirine ring in the novel MCMAC azirine. The simultaneous presence of these two groups accelerates intersystem crossing toward the triplet state where cleavage of the C-N bond takes place. The primary photoproducts resulting from the C-N and C-C ring-opening reactions were also found to undergo further photochemical decarbonylation or decarboxylation reactions.

Argon↗
PubMed1983

[Computerized tomography and lung function scintigraphy in central bronchial cancer. Comparison between morphologic and functional changes].

Functional scintigraphic and computer tomographic findings in 20 patients with central bronchial carcinomas were compared in order to determine to what extent functional changes correlate with morphological appearances. Computer tomography shows alterations in the bronchial system more clearly than changes in large or small pulmonary vessels. Pre-operative and subsequent scintigraphy is essential for exact determination of regional lung function. It was shown that short-lived radio-active gases, such as krypton 81, may indicate a total lack of ventilation where there is only a severe bronchial stenosis; the use of longer half-life nucleids, such as krypton 85 or xenon 133, provides good correlation with computer tomographic findings of a bronchial stenosis.

Bronchi↗
PubMed1979

Theoretical of the measurement of choroidal blood flow using a radioactive inert gas clearance technique.

A mathematical model for the diffusion of krypton in ocular tissues and its removal by blood flow has been developed to explain the complex clearance pattern found experimentally in the rabbit--an animal which has predominantly a choroidal circulation. Comparison of theoretical and experimental results has shown that the initial slope of the clearance curve is a measure of choroidal blood flow for values of blood flow over 500 ml/100 g/min. The shape of the curve at later times has been shown to be attributable predominantly to the diffusion of krypton into other ocular tissues.

Animals↗
PubMed1984

Right ventricular performance in chronic air flow obstruction.

Right ventricular pump performances were assessed in 14 patients with chronic obstructive pulmonary disease by means of radionuclide angiocardiography using krypton-81m as a tracer. Right ventricular ejection fraction (RVEF) was significantly lower in the patients than in normal volunteers. Additionally there was a striking difference in RVEF between patients with normal pulmonary artery pressure (PAP) and those with pathologically elevated PAP. A linear negative correlation between RVEF and mean PAP could be demonstrated. From this data we suggest that radionuclide angiocardiography using krypton-81m allows non invasive assessment of right heart afterload and thus indirectly PAP.

Adult↗
PubMedDate not supplied

Distribution of the blood flow supplied by the vertebral artery in humans as assessed by emission CT.

Though unilateral blood distribution of the vertebral artery has not been studied in humans, it is significant when considering the ischemic events especially embolic occlusion in vertebrobasilar system. To clarify the blood distribution, Krypton-81m was continuously infused into the vertebral arteries of 10 patients. Radioactivity was recorded by a rotating gamma camera. The perfusion images, reconstructed by computer in the transaxial plane, were classified according to whether the distribution was equal, or predominantly unilateral. Overlapping of blood supply from each vertebral artery was studied. In addition, the perfusion from one of the vertebral arteries revealed four distribution patterns with respect to laterality. A) ipsilateral; B) contralateral; C) bilateral; D) mosaic. Images obtained following perfusion of the vertebral artery show less uniformity compared to that of the internal carotid artery, suggesting a complicated vascular supply of the vertebral basilar territory. This complex distribution can be classified by the use of continuous infusion of Krypton-81m.

Adult↗
PubMed1989

[Imaging and measurement of global and regional airflow in the lung using a radioactive gas].

In this paper it is shown how "circumscribed" movements of air within the lungs, such as those occurring during respiration, can be visualized and measured with the aid of the radio-active gas krypton 81 m. With this new examination technique, the previously employed procedures used for investigating the lungs have been expanded: In the imaging procedures sector, function patterns of regional ventilation can now be recognized, while the diagnostic evaluation of pulmonary function is complemented by the regional identification of disturbed and undisturbed ventilation. The equipment required for the examination is available in any nuclear medical department, and the methodology is relatively simple. The use of such studies is described on the basis of two clinical cases: The findings obtained with this new procedure clearly demonstrate the expansion of the diagnostic evaluation, and already point to the indications. Since 1982, we have carried out some 1,500 investigations of pulmonary ventilation. On the basis of the experience thus gained, a spectrum of indications can be established, and this is represented in the "Discussion". The inert gas, krypton, which is both odourless and chemically inert and has optimal physical properties for nuclear medical studies, has been shown by our investigations to be highly suitable for sophisticated analyses of pulmonary function, also in the severe-ill patient. Properly and rationally employed, the procedure is economical, and the radiation exposure low.

Aged↗
PubMed1985

Ultraviolet-laser ablation of skin.

We report on the use of pulsed ultraviolet-laser irradiation at 193 nm from an argon-fluoride laser and at 248 nm from a krypton-fluoride laser to ablate skin. In vitro, both wavelengths performed comparably, removing tissue precisely and cleanly, and leaving minimal thermal damage to the surrounding tissue. In vivo, the 193-nm laser radiation failed to remove tissue after bleeding began. The 248-nm radiation, however, continued to remove tissue despite bleeding and left a clean incision with only minimal thermal damage. The krypton-fluoride excimer laser beam at 248 nm, which should be deliverable through a quartz optical fiber, has great potential as a surgical instrument.

Animals↗
PubMed1984

Ultrastructural findings in the brain of fruit flies (Drosophila melanogaster) and mice exposed to high-energy particle radiation.

Effects of high energy, heavy particle (HZE) radiation were studied in the brain of the fruit fly (Drosophila melanogaster) exposed to argon (40Ar) or krypton (84Kr) ions. In the flies exposed to argon the fluence ranged from 6 X 10(4) to 8 X 10(7) particles/cm2. The insects were killed 35 days after exposure. Extensive tissue fragmentation was observed at the higher fluence employed. At fluences ranging from 5 X 10(6) (one hit/two cell bodies) to 9 X 10(4) (one hit/90 cell bodies) particles/cm2, swelling of the neuronal cytoplasm and focally fragmented membranes was observed. Marked increase of glial lamellae around nerve cell processes was seen at fluences ranging from one hit/six to one hit/135 cell bodies. In the flies irradiated with krypton, the fluences employed were 5.8 X 10(3) and 2.2 X 10(6) particles/cm2. Acute and late effects were evaluated. In the flies killed 36 hours after exposure (acute effects) to either fluence, glycogen particles were found in the neuroglial compartment. The granules were no longer present in flies killed 35 days later (late effects). As in the flies exposed to argon, neuronal swelling and membrane disruption were observed 35 days after exposure to both fluences. From these studies it appears that the Drosophila brain is a useful model to investigate radiation damage to mature neurons, neuroglia, and therefore, to the glio-neuronal metabolic unit. In a separate study, the synaptic profiles of the neuropil in layers II-III of the frontal cerebral cortex of anesthesized adult LAFl mice were quantitatively appraised after exposure to argon (40Ar) particles. The absorbed dose ranged from 0.05 to 5 gray (Gy) plateau. It was determined that the sodium pentobarbital anesthesia per se results in a significant decrease in synaptic profile length one day after anesthetization, with return to normal values after 2-28 days. Irradiation with 0.05-5 Gy argon particles significantly inhibited the synaptic shortening effect of anesthesia at one day after exposure.

Animals↗
PubMedDate not supplied

The relationship between the pulmonary distribution of inhaled fine aerosols and tests of small airway function.

Gamma-camera lung images obtained after aerosol inhalation (2.2 micron mean aerodynamic diameter) were compared with those obtained during inhalation of krypton-81m gas. The penetration of the aerosol to the periphery of the lung appeared in both smokers and nonsmokers to be similar to the penetration of krypton-81m. An index of the inhomogeneity of deposition of the aerosol (aerosol distribution index, ADI) was calculated by dividing the variance of the cell by cell radioactivity counts by the mean count. This index was expressed as the mean value for both lungs (ADIM) or the value for the lung with the higher value (ADIH). ADIM and ADIH were correlated with the FEV1 and maximum expiratory flow rates at 50% and 25% of vital capacity and on average showed higher values for smokers than non-smokers. ADIH, forced expired time and partial expiratory time from 50% to 0% of vital capacity were correlated with pack-years of smoking. It is concluded that the results of tests of small airway disease are related to inhomogeneities of airflow in the periphery of the lung and that measurements of aerosol deposition may provide a sensitive indicator of disease of small airways. The future potential of the test is discussed.

Adult↗
PubMed1994

[Regional pulmonary function test--pulmonary nuclear medicine].

Pulmonary nuclear medicine has been dominated by techniques that depict the distribution of pulmonary ventilation and perfusion. At present, there are three commercially available methods of performing a ventilation study. One of the methods utilizes xenon-gas 133Xe, one utilizes radioactive krypton gas, 81mKr, and the last is performed with a radioactive aerosol, usually the radio aerosol of 99Tc human serum albumin (HSA). Ventilation studies with 133Xe usually consist of an image taken after inhalation of a single breath, which can be followed by a serial image. After a rebreathing period of 3 to 5 minutes, the tracer (133Xe) is washed out of the lungs. The washout portion of the 133Xe study is the most reliable and sensitive to detect of the slow compartments. Krypton-81m has a very short physical half-life of 13 seconds. Thus, ventilation scans can be obtained in desired projections, and the rapid disappearance of the tracer from lungs will allow ventilation studies to be performed before and after medications and exercise. Radioaerosols also provide a means for investigating regional ventilation. Radioaerosols are small particles, rather than gases, and are deposited in the lung by impaction, sedimentation and random contact. With the recent development of new radiopharmaceuticals and refinement of current imaging techniques, especially quantitative techniques and single-photon emission computed tomography of the lung, pulmonary nuclear medicine has expanded its horizons.

Humans↗
PubMed1983

Time and location analysis of lesion formation in photocoagulation.

Fourteen eyes from seven owl monkeys were used for study of the time and location within the retinal layers of the formation of the white reactions produced by photocoagulation with green (530.9 nm), yellow (568.2 nm), or red (647.1 nm) krypton wavelengths. Locations on the retina with equivalent conditions of absorbance were chosen. The white reaction formed in the first 100 ms of application. The depth at which the most damage occurred depended on the wavelength used. The final shape of the lesion depended on the location (in depth) of the white reaction first formed and on the power of the laser beam. The cauterizing power of the krypton yellow was evident.

Animals↗
PubMed1986

Cell proliferation after laser photocoagulation in primate retina. An autoradiographic study.

Argon blue-green laser and krypton red laser (KRL) photocoagulation were applied to primate retinas at intervals ranging from two to 23 days before the animals were killed. An injection of tritiated thymidine was given intravitreally three days before death. Argon blue-green laser photocoagulation induced cell proliferation in the retina and retinal pigment epithelium seven days after treatment, with quiescence at 23 days. Krypton red laser photocoagulation induced similar cell proliferation not only in the retina and retinal pigment epithelium but also around choroidal vessels and in the stroma of the choroid. Peak thymidine uptake occurred seven days after KRL treatment. There was less uptake at two and 11 days and no uptake at 23 days. Thymidine uptake in the retina and choroid also was detected with low levels of KRL treatment. True cell hyperplasia (cell division) occurred after laser treatment; only KRL treatment induced cellular reaction in the choroid.

Animals↗
PubMed1991

Laser photocoagulation of subfoveal neovascular lesions in age-related macular degeneration. Results of a randomized clinical trial. Macular Photocoagulation Study Group.

A clinical trial has been conducted to evaluate the effect on vision of laser treatment (argon green or krypton red lasers, assigned randomly) compared with no treatment of eyes with subfoveal choroidal neovascularization associated with age-related macular degeneration. Three months after enrollment, the visual acuity of 37 (20%) of 184 laser-treated eyes had decreased 6 or more lines from the baseline level, while only 19 (11%) of 178 untreated eyes had suffered such large decreases (P = .01, chi 2 test). However, 24 months after enrollment, the visual acuity of only 23 (20%) of 114 laser-treated eyes had decreased by 6 or more lines from baseline compared with 41 (37%) of 112 untreated eyes (P less than .01, chi 2 test). On average, after 24 months, visual acuity of laser-treated eyes had decreased 3 lines from baseline, and visual acuity of untreated eyes had decreased 4 lines (P = .003, t test). Laser-treated eyes retained contrast threshold for large letters at or near baseline levels through 36 months of follow-up examinations, while the contrast threshold of untreated eyes worsened. Persistent or recurrent neovascularization was observed in 51% of the laser-treated eyes by 24 months after initial treatment but was not associated with decreased visual acuity. None of the findings suggested a reason to favor either the argon green or krypton red wavelength. Laser treatment of subfoveal neovascular lesions that meet the eligibility criteria for this study is recommended if both the patient and the ophthalmologist are prepared for a large decrease in visual acuity immediately after treatment.

Adult↗
PubMed1981

Dual laser beam focussing for flow cytometry through a single crossed cylindrical lens pair.

Two laser beans (argon 488 nm blue, and krypton UV lines) have been focussed either to the same point or to two different points in a vertical plane in a multiparameter flow cytometer. The technique exploits the focal length shortening of the longer wavelength beam that occurs with spherical and astigmatic lens aberrations. Ethidium bromide-stained DNA is excited by both the argon 488 nm and krypton UV lines and the excitation intensities of both beams were set to give the same red fluorescence pulse height from ethidium bromide-stained nuclei. DNA histograms were obtained for sequential focussing of the two beams and these were virtually identical irrespective of which beam was the first excitor and irrespective of which beam the histogram was recorded from. Coincident focussing of the two exciting beams resulted in a histogram of double the emission intensity.

Cell Nucleus↗