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At least 199 records · Page 11Linked to original sources
PubMed1988

Juxtapapillary exophytic retinal capillary hemangioma treated by yellow krypton (568 nm) laser photocoagulation.

A 30-year-old man was found to have juxtapapillary exophytic capillary hemangioma complicated by circinate maculopathy and peripapillary exudative retinal detachment. The diagnosis was made from the appearance of the tumor and confirmed by fluorescein angiography. The presence of intermittent hematuria associated with a cystic kidney supported the diagnosis of von- Hippel-Lindau disease. subsequently, and attempt to treat the vascular lesion by yellow krypton (586 nm) laser photocoagulation failed to arrest the progression of the exudative retinal detachment, which finally became total.

Adult↗
PubMed1986

[Right ventricular function assessed by scintigraphy using continuous infusion of krypton-81 m].

Scintigraphy using continuous infusion of krypton-81m, (81mKr) is a reproducible, noninvasive method for determining right ventricular ejection fraction (RVEF). Radionuclide determinations of RVEF by 81mKr scintigraphy were compared with those by the technetium-99m (99mTc) first-pass technique in 25 patients; the results obtained by both methods correlated well (r = 0.86, p less than 0.005). In 20 additional patients, the RVEF determined by 81mKr was compared with the RVEF as measured by multislice ECG-gated cardiac X-ray computed tomography, and there was good correlation between RVEFs obtained by the two methods (r = 0.76, p less than 0.005). Furthermore, the RVEF by the 81mKr technique and the LVEF by the 99mTc gated blood pool technique were compared with hemodynamic measurements. There was a significant inverse correlation between RVEF and pulmonary artery pressure or total pulmonary resistance. Other determinants of right ventricular systolic function were the presence of proximal right coronary artery disease, reduced left ventricular function and associated tricuspid regurgitation.

Heart↗
PubMed1986

Krypton-79m: a new radionuclide for applications in nuclear medicine.

Krypton-79m emits 130-keV gamma rays in 27 +/- 1% of its disintegrations and decays with a half-life of 50 +/- 3 sec. It is generated readily by bombarding nearly saturated aqueous solutions of bromide salts, or bromoform, with 14-MeV protons. The 79mKr is swept out continuously as it is produced by bubbling helium upward through the liquids. Up to 200 mCi per I are obtained of the resulting mixture of gases. The 79mKr + helium is mixed with about five volumes of air and then driven continuously through a small-bore tube to an Anger scintillation camera located approximately 200 yards away. The rate of flow is adjusted so that the amounts of 13-sec 81mKr and of 35-hr 79Kr are inconsequential at the time and point of use. When the gases are inhaled, good images of the lungs are obtained with an Anger scintillation camera. The trachea and bronchi commonly are revealed also.

Humans↗
PubMedDate not supplied

Measurement of right ventricular ejection fraction with krypton-81m in chronic obstructive pulmonary disease.

Thirty patients with chronic obstructive pulmonary disease (COPD) and 15 healthy volunteers have been studied to assess the value of measuring right ventricular ejection fraction (RVEF) at rest with a perfusion of krypton-81m (81mKr). With this perfusion, equilibrium RVEF can be measured in a 30 degrees right anterior oblique projection, avoiding a superimposition of cardiac cavities. The average RVEF of the patients with COPD was significantly lower than that of the normal patients (36.3 +/- 9.3% vs 52.6 +/- 3.9%; p less than 0.001). An inverse linear relation was found between mean pulmonary artery pressure (Ppa) and RVEF (r = -0.543; p less than 0.01). The RVEF in a group of 15 patients with COPD and pulmonary hypertension (Ppa greater than 20 mmHg), averaged 30.4 +/- 7.26%, which was significantly lower than that of the other 15 COPD patients with normal Ppa, whose RVEF averaged 42.3 +/- 7.1% (p less than 0.01). Taking a RVEF value less than or equal to 35% as an indicator of pulmonary hypertension, the sensitivity was 80% and specificity was 75%, the predictive value for a positive test was 75%, and for a negative test was 80%. A positive but weak correlation was found between RVEF and PaO2 (r = 0.52; p less than 0.01), SaO2 (r = 0.41; p less than 0.05) and the forced expiratory volume in one second (FEV1) (r = 0.40; p less than 0.05). No correlation was found between RVEF and prior history of right cardiac insufficiency, PaCO2, pH, the ratio FEV1/vital capacity, ECG signs of cor pulmonale and left ventricular ejection fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Krypton-81m imaging of the right ventricle.

We report the development of a method for obtaining right-ventricular radionuclide angiograms using continuous peripheral intravenous infusion of the ultra-short-lived nuclide krypton-81m. This tracer has a half-life of 13 sec, emits a single 190-keV photon, and is extremely insoluble. During infusion into a peripheral vein, Kr-81m achieves stable count rates over the right heart, and it is essentially completely cleared by the lungs during its initial pulmonary transit. Thus no interfering activity is present in the systemic circulation. Initial studies provide excellent data on right-heart anatomy and function.

Heart↗
PubMed1979

An experimental model for angina pectoris using krypton-81m. The dynamic balance between myocardial perfusion and metabolism.

16 anesthetized and open chest dogs were studied. Regional myocardial perfusion was assessed using a constant infusion of krypton-81m (half-life 13 sec) into the aortic sinuses and a gamma camera linked to a digital computer. The epicardial electrocardiogram was recorded and the plasma activity of creatine kinase was measured in serial blood samples from the aorta and a local coronary vein draining the area of myocardium supplied by the left anterior descending coronary artery (LAD). These parameters were observed throughout the whole period of a 5-h experiment. Two reversible snares were positioned on the middle portion of this artery. A critical narrowing of this vessel was produced and a peripheral venous infusion of isoproterenol (causing a 5--10% increase in heart rate and a 10--15% fall in blood pressure) was used to increase myocardial oxygen demand. During infusion there was both a relative and absolute fall in regional myocardial perfusion together with evidence of myocardial ischemia in the epicardial electrocardiogram. Provided the infusion was discontinued within 30 min (8 dogs) myocardial perfusion and the epicardial electrocardiogram returned to normal during a 5-h recovery period. In addition there was no efflux of creatine kinase activity from the ischemic area. When infusion was continued for 1 h (4 dogs) permanent alterations in myocardial perfusion and the epicardial electrocardiogram occurred and there was increased creatine kinase activity released from the area of myocardium by the narrowed vessel. Infusion for 40 min in 4 dogs produced permanent alterations in the parameters measured in 2 and complete recovery in the remaining 2. A further 4 dogs were studied in the same way but without a snare on the coronary artery. Isoproterenol given for 1 h produced no effects on any of the parameters either during or after infusion.

Angina Pectoris↗
PubMed1983

[Measurement of the right ventricular ejection fraction during the acute phase of myocardial infarction using 81m krypton infusion. Comparison with the left ejection fraction].

The right ventricular ejection fraction is rarely measured, as conventional diagnostic methods (radiology, echocardiography) are confronted with the problem of representing the right ventricle as a simple tridimensional geometrical model. This is not necessary with the radio-isotopic techniques. However, all those used for the measurement of right ventricular ejection fraction lead to important methodological problems. We have therefore developed a technique of measuring this parameter with an infusion of 81 m Kr. This radioactive gas is pure gamma-ray emitter with a 13 second period. Dissolved and infused intravenously, it is eliminated during the first passage through the lung. The continuous separation of the generator of 81 m Kr is performed with isotonic dextrose solution which is then infused for a period of 7 minutes. During this time, the activity detected by the scintillation camera inclined in the 30 degrees RAO projection is stored, together with the electrocardiogram in a computer. The precordial radioactivity of the retrocardiac lung tissue is subtracted after injection of 74 MBq of 99 mTc microspheres. A graph of right ventricular activity can then be reconstructed and the right ventricular ejection fraction calculated. The left ventricular ejection fraction is then measured with 99 mTc--labelled RBCs. This method allows the right ventricular ejection fraction to be measured in the RAO projection, the best incidence for the separation of the right atrial from the right ventricular activity without interference from left ventricular activity because of the pulmonary elimination of the Krypton radioactivity. The measurement performed on a large number of cardiac cycles allows a continuous study of the right ventricular ejection fraction. At the end of the infusion there is no circulating radioactivity so that the measurement can be repeated. This technique was used in 17 patients with acute myocardial infarction. In the 7 patients with anterior infarcts reduction of the left ventricular ejection fraction was the predominant finding (21,6 +/- 6,8%). The right ventricular ejection fraction was 34,2 +/- 6,4%. On the other hand, patients with a postero-inferior infarction had little change in left ventricular ejection fraction (59,2 +/- 12%) but those with right ventricular extension of their infarcts had very reduced right ventricular ejection fractions (less than 23%). The measurement of right ventricular ejection fraction with 81 m Kr is a reliable atraumatic method for diagnosing right ventricular infarction by the quantification of its functional impairment.

Adult↗
PubMed1984

Histopathologic studies on transscleral argon-krypton photocoagulation with an exolaser probe.

We performed argon and krypton laser photocoagulation of the retina and ciliary body on rabbit and monkey eyes using an exolaser probe. Clinically, transscleral retinal lesions produced a white circumscribed reaction. Histologically, we observed necrosis of the retina and choroid. Chronic lesions showed disorganization of the retina and formation of chorioretinal scars. Transciliary body laser coagulation damaged the ciliary body and its processes. The intraocular pressure was reduced in rabbits for one week and in monkeys for two weeks after 360 degrees transciliary laser coagulation. Scleral involvement was a common finding in transscleral laser coagulation.

Animals↗
PubMed1996

Argon green vs. krypton red laser photocoagulation for extrafoveal choroidal neovascularization secondary to age-related macular degeneration: 3-year results of a multicentre randomized trial. Canadian Ophthalmology Study Group.

OBJECTIVE: To determine whether argon green laser (AGL) or krypton red laser (KRL) is superior for the treatment of well-defined extrafoveal choroidal neovascularization (CNV) in patients with age-related macular degeneration (AMD) after 3 years of follow-up. DESIGN: Multicentre randomized clinical trial. SETTING: University-based referral practices in Canada. PARTICIPANTS: Among 210 patients selected by ophthalmologists at 13 participating centres there were 191 eligible patients aged 50 years or more with angiographically proven CNV whose posterior edge was 200 to 2500 microns from the foveal avascular zone. Other inclusion criteria included the presence of drusen in either eye, a best corrected visual acuity in the study eye of at least 35 letters on the Early Treatment Diabetic Retinopathy Study chart (equivalent of 20/200 or better on the Snellen chart) and no prior photocoagulation in the study eye. The patients were randomly assigned to receive either AGL (96 patients) or KRL (95 patients) treatment. INTERVENTIONS: Treatment with 200-microns spots of 0.2 to 0.5 seconds' exposure to produce a homogeneous grey white lesion that completely covered the CNV. OUTCOME MEASURES: Change from baseline in visual acuity at 1, 2 and 3 years (primary measure), development of persistent or recurrent CNV (secondary measure). RESULTS: There were no significant differences between the treatment groups in drop-out rates. No significant differences were found between the two groups in loss of visual acuity or angiographic evidence of persistent or recurrent CNV. CONCLUSION: KRL is no better than AGL in preserving vision and preventing loss of visual acuity in patients with AMD with well-defined extrafoveal CNV followed for 3 years.

Aged↗
PubMed1997

Flow cytometric analysis and confocal imaging of anticancer alkylaminoanthraquinones and their N-oxides in intact human cells using 647-nm krypton laser excitation.

Flow cytometry and laser-scanning confocal fluorescence microscopy have been used in the study of the pharmacodynamics, in single intact cells, of two novel alkylaminoanthraquinones (AQ4 and AQ6), structurally based upon the mid-red excitable but very weakly fluorescent anticancer agent mitoxantrone, together with their respective N-oxide derivatives (AQ4NO and AQ6NO). The drug design rationale was that N-oxide modifications generates prodrug forms suitable for selective bioreductive-activation in hypoxic tumor cells. DNA-binding ranked in the order of mitoxantrone > AQ6 > AQ4 > AQ6NO >> AQ4NO. Using both cytometric methods a similar ranking was found for whole cell and nuclear location in human transformed fibroblasts. However, AQ6 showed enhanced nuclear uptake compared with mitoxantrone, in keeping with its greater capacity to inhibit DNA synthesis. Partial charge neutralisation by N-oxide derivatization resulted in loss of DNA synthesis inhibition but retention of the ability to accumulate in the cytosol, an important property for prodrug development. We conclude that both flow cytometry and confocal imaging revealed biologically significant differences between analogues for subcellular distribution and retention properties. The study demonstrates the potential for these complementary 647-nm krypton laser line-based fluorometric methods to provide relevant structure-activity information in anthraquinone drug-design programmes.

Anthraquinones↗
PubMed1998

Exploring hydrophobic sites in proteins with xenon or krypton.

X-ray diffraction is used to study the binding of xenon and krypton to a variety of crystallised proteins: porcine pancreatic elastase; subtilisin Carlsberg from Bacillus licheniformis; cutinase from Fusarium solani; collagenase from Hypoderma lineatum; hen egg lysozyme, the lipoamide dehydrogenase domain from the outer membrane protein P64k from Neisseria meningitidis; urate-oxidase from Aspergillus flavus, mosquitocidal delta-endotoxin CytB from Bacillus thuringiensis and the ligand-binding domain of the human nuclear retinoid-X receptor RXR-alpha. Under gas pressures ranging from 8 to 20 bar, xenon is able to bind to discrete sites in hydrophobic cavities, ligand and substrate binding pockets, and into the pore of channel-like structures. These xenon complexes can be used to map hydrophobic sites in proteins, or as heavy-atom derivatives in the isomorphous replacement method of structure determination.

Animals↗
PubMed1986

Ultrastructure of Bruch's membrane after krypton laser photocoagulation. II. Repair of Bruch's membrane and the role of macrophages.

The accompanying ultrastructural study showed that ophthalmoscopically white krypton laser photocoagulation in rats is followed by cellular invasion causing breakdown of Bruch's membrane (BM). We have expanded these observations, using scanning electron microscopy, transmission electron microscopy, and high-voltage transmission electron microscopy to describe the healing process. The repair of BM involves regenerating retinal pigment epithelial cells and choriocapillaris (CC) that form new basement membranes and fibroblasts that secrete collagen and elastin. The reformation of the CC is also associated with subretinal neovascularization. The involvement of macrophages was evident throughout the process of BM repair and formation of new vessels. We propose that the macrophages act as a common factor linking the diverse diseases associated with choroidal subretinal neovascularization, deduced from our evaluation of the healing process and the reformation of choriocapillaris.

Animals↗
PubMed1983

Argon and krypton laser photocoagulation of senile exudative macular degeneration.

Senile exudative macular degeneration can be divided into two stages: the pre-exudative stage of drusen and pigment-epithelial degeneration and the exudative stage of pigment-epithelial detachment (PED) and the disciform lesion. Patients with PED may retain useful vision for many years but finally subretinal neovascularisation develops resulting in a disciform scar with loss of central vision. Photocoagulation has no favourable therapeutic effect. The disciform lesion has a poor visual outcome. In part of the patients the subretinal neovascularisation can successfully be treated by laser coagulation. The prognosis depends on duration of symptoms, visual acuity and the distance between neovascularisation and the foveal area. As the newly formed vessels will grow rapidly towards the posterior pole, patients with a senile disciform lesion must be considered as emergency cases. The krypton laser has advantages over the argon laser but to what degree is still to be assessed.

Fluorescein Angiography↗
PubMed1991

[The morphological results of the use of a pulsed krypton fluoride excimer laser for enamel conditioning].

Although there have been many advances in the field of acid etching, major problems still present. For the most part, these are the unpredictability of the effects of etching, the lack of control of the depth of etching over the long term, and the development of enamel fractures occurring on debonding. The aim of this study was to investigate the morphological effects of enamel conditioning using a pulsed krypton fluoride excimer laser (wavelength 248 nm). Scanning electron microscopic examination revealed a surface similar to that produced by peripheral etching; no signs of thermal damage were to be seen. The requirements that have to be met by a modern laser considered as a possible alternative to conventional acid etching, are discussed.

Acid Etching, Dental↗
PubMed1985

Krypton red laser photocoagulation for subretinal neovascularization.

One hundred fifty-seven patients with subretinal neovascularization (SRN) were treated in a prospective, nonrandomized, consecutive study with the krypton red laser (KRL). The patients were analyzed with respect to age, etiology of the SRN, location of the SRN, and pre- and post-treatment visual acuity in patients with at least three months follow-up. Previous studies have not investigated KRL photocoagulation within the foveal avascular zone (FAZ). The results of this study compare favorably with other large series in which patients with SRN located outside the FAZ were treated with the argon blue-green laser (ABGL).

Adult↗
PubMed2006

Electron impact fragmentation of size-selected krypton clusters.

Clusters of krypton are generated in a supersonic expansion and size selected by deflection from a helium target beam. By measuring angular distributions for different fragment masses and time-of-flight distributions for fixed deflection angles and fragment masses, the complete fragmentation patterns for electron impact ionization at 70 eV are obtained from the dimer to the heptamer. For each of the neutral Kr(n) clusters studied, the main fragment is the monomer Kr(+) ion with a probability f(n)(1) > 90%. The probability of observing dimer Kr(2)(+) ions is much smaller than expected for each initial cluster size. The trimer ion Kr(3)(+) appears first from the neutral Kr(5), and its fraction increases with increasing neutral cluster size n, but is always much smaller than that of the monomer or dimer. For neutral Kr(7), all possible ion fragments are observed, but the monomer still represents 90% of the overall probability and fragments with n > 3 contribute less than 1% of the total. Aspects of the Kr(n) cluster ionization process and the experimental measurements are discussed to provide possible reasons for the surprisingly high probability of observing fragmentation to the Kr(+) monomer ion.

Journal Article↗
PubMed2004

The dynamic desorption of krypton from the zeolite chabazite.

Single crystal diffraction studies of the zeolite chabazite show that at high loading krypton atoms are forced to occupy sites with unfavourable interatomic Kr-Kr separations but upon desorption of Kr the remaining Kr atoms can now occupy sites with no such unfavourable separations.

Journal Article↗
PubMed1990

[Krypton laser coagulation in idiopathic macular holes].

Twenty-six eyes with acute idiopathic senile macular holes and visual acuity of between 0.02 and 0.5 were treated by laser coagulation with krypton red. The laser burns were placed in a ring around the hole, at the border of the retinal detachment. A few weeks after treatment marked regression of the detachment was seen. During the follow-up period (3-18 months) visual acuity improved in 18 eyes, deteriorated in 1 and was unchanged in 7.

Aged↗