SEARCH · Search PubMed

Results for “Krypton”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45Linked to original sources

PubMed1984

Computation of ventilation-perfusion ratio with Kr-81m in pulmonary embolism.

Diagnostic difficulties occur in pulmonary embolism (PE) during visual analysis of ventilation-perfusion images in matched defects or in chronic obstructive lung disease (COPD). In 44 patients with angiographically confirmed PE and in 40 patients with COPD, the regional ventilation-perfusion ratios (V/Q) were therefore computed using krypton-81m for each perfusion defect, and were displayed in a functional image. In patients with PE and mismatched defects, a high V/Q (1.96) was observed. A V/Q greater than 1.25 was also found in nine of 11 patients having PE and indeterminate studies (studies with perfusion abnormalities matched by radiographic abnormalities). COPD was characterized by matched defects and low V/Q. The percentage of patients correctly classified as having PE or COPD increased from 56% when considering the match or mismatched character to 88% when based on a V/Q of 1.25 in the region of the perfusion defect. This quantitative analysis, therefore, seems useful in classifying patients with scintigraphic suspicion of PE.

Adult↗

PubMed1982

Gastric blood flow and distribution in anesthetized cat and man as studied by an inert gas elimination method.

Gastric blood flow and its intramural distribution were studied in anesthetized cat and man by recording the elimination of intra-arterially injected krypton-85. The elimination was monitored with two external detectors--a scintillation detector recording the disappearance of gamma-activity from the entire gastric wall and a G-M tube recording the disappearance of beta-activity from the muscle layer only. Total and muscle layer blood flow could be calculated from the washout curves, and, knowing these variables, the blood flow to the mucosa-submucosa could be indirectly calculated. Gastric blood flow in the cat and man closely resembled each other, both in magnitude and distribution. Total blood flow in man 'at rest' was 12 +/- 4 ml/min and 100 g tissue (mean +/- S.D.; no. = 20), muscle blood flow amounting to 7 +/- 3 and mucosa-submucosa flow to 16 +/- 8 ml/min and 100 g muscle and mucosa-submucosa tissue, respectively. The distribution to the muscle layer was 26 +/- 14% and to the mucosa-submucosa 74 +/- 14% of total gastric blood flow.

Anesthesia, General↗

PubMed1982

Gastric blood flow and distribution: the effect of pentagastrin in anesthetized cat and man as studied by an inert gas elimination method.

Using a krypton-85 elimination method previously described, the effect of pentagastrin on gastric blood flow has been studied in 28 anesthetized patients, 12 control patients, and 16 patients with duodenal ulcer disease. Both in control and duodenal ulcer patients a significant increase in total blood flow was found, reflecting an increase of flow in the mucosa-submucosa layer of the corpus. In normal subjects a 5-fold increase in flow was found in this tissue layer, whereas the corresponding increase in duodenal ulcer patients was 12-fold. Concomitantly, a significant decrease of flow distribution to the muscle layer was seen. In the antrum pentagastrin did not cause any significant changes in either mucosa-submucosa or muscle layer blood flow. No qualitative differences in the response to pentagastrin, with regard to the gastric blood flow, was found between normal subjects and duodenal ulcer patients.

Adult↗

PubMedDate not supplied

A study of regional cerebral blood flow and hemodynamics in cerebrovascular diseases by selective continuous infusion of Kr-81m.

A tomographic study of regional cerebral blood flow and hemodynamics was performed on 25 patients with cerebrovascular diseases by selective continuous infusion of krypton-81m (Kr-81m). Kr-81m single photon emission computed tomograms were superimposed on X-ray computed tomograms to assess topographically the perfusion of the entire brain. Study of cerebrovascular diseases using this method showed: (1) regional cerebral blood flow change; (2) perfusion distribution change; (3) the route by which blood reached the brain or the obstructed artery proximal to the circle of Willis; (4) development of a collateral system and its actual function; and (5) efficacy of surgical bypass after extracranial-intracranial anastomosis. This method is especially useful in hemodynamic assessment in patients with ischemic cerebrovascular disease.

Adult↗

PubMed1981

Sensitivity of Kr-81m and Xe-127 in evaluating nonembolic pulmonary disease.

The relative sensitivities of Kr-81m and Xe-127 in detecting lung ventilation defects was evaluated in 80 patients with nonembolic pulmonary diseases. Krypton-81m ventilation images (500,000 count) were interdigitated with Tc-99m MAA perfusion images; both were compared with Xe-127 images. The distributions of the two gases were also compared on the basis of point-by-point computer analyses. Xenon-127 was found to be more sensitive than Kr-81m in clinical evaluations of scintiphotos--although they were equivalent by computer analyses--in indicating regions of impaired ventilation in patients with obstructive airways disease.

Computers↗

PubMed1984

Topographic distribution of pulmonary ventilation and perfusion in the horse.

The regional distribution of ventilation to perfusion ratios (VA/Q) in the lungs of 8 healthy standing Thoroughbred geldings (4.4 +/- 1.5 years, 465.7 +/- 46.6 kg) was studied, using steady-state inhalation and IV infusion of the radioactive gas krypton-81m. The VA/Q was uniformly distributed within a vertical lung strip centered over the 9th rib on the right side. Ventilation per unit of alveolar volume (V/VA) assessed from the clearance of inhaled radioactive gas in 5 horses increased from 0.49 +/- 0.13 (arbitrary units) in nondependent lung zones to 1.45 +/- 0.16 in dependent lung zones. Seemingly, a vertical gradient of pulmonary ventilation exists in the horse that is matched by a similar gradient of perfusion.

Animals↗

PubMed1982

Limitations of Kr-81m for quantitation of ventilation scans.

Predictions of Kr-81m behavior in the lungs have been based on a single-compartment model of well-mixed gas. To determine the validity of this model, anesthetized, paralyzed dogs were ventilated mechanically over a wide range of ventilations with Kr-81m in the inspirate. Averaged data obtained from 1.5- to 2-min images were compared with the model's predictions. Krypton-81m concentration appeared more linearly related to ventilation than the model predicts. This suggests that the Kr-81m may not be distributed to the entire resident gas volume or that its distribution changes with lung volume. Estimation of end-expiratory volume (FRC)--based on the tidal volume and the maximum-to-minimum count ratio over the lung during gated acquisitions--underestimated the true FRC by about 40%. The magnitude of error depended upon the combination of tidal volume and frequency and the inspiratory time. Thus, Kr-81m does not mix well with resident lung gas, and the well-mixed, single-compartment model is not a good predictor of Kr-81m behavior in the lung.

Animals↗

PubMed1976

Ocular damage induced by near-ultraviolet laser radiation.

A quantitative study was conducted of ocular damage thresholds in the rhesus monkey eye from krypton, argon, and nitrogen laser radiation. Corneal and lenticular thresholds are reported for various laser beam parameters. Corneal damage was found to occur following incident energy doses of approximately 60 to 70 Joules per square centimeter (J./cm.2) for pulsewidths ranging from 250 musec to 120 sec. The results are consistent with a photochemical damage mechanism. With certain exposure parameters, cataracts were induced with lower energy doses than required to cause corneal damage. The lenticular thresholds, however, appear to be consistent with a thermal rather than a photochemical mechanism. Corneal and lenticular hazards of near-ultraviolet (near-UV) lasers are discussed in terms of existing safety standards for laser radiation.

Animals↗

PubMed1977

Quantification of flow in a dynamic phantom using Rb81-Kr81m, and a Nal detector.

Blood flow can be measured by monitoring the count rate of Krypton-81m after its parent, Rubidium-81 (a potassium analogue), has been deposited in the tissue. The steady-state Kr-81m count rate reflects both production by decay of Rb-81 and washout due to blood flow. Its use is theoretically superior to that of Xenon-133 for quantification of blood flow (cc/min per 100 gm) since: (1) multiple flow measurements can be obtained from a single arterial injection, (2) flow-dependent changes in the count rate of Kr-81m provide a steady-state measure of specific flow, and (3) errors due to uptake in fat are eliminated. The count rate of Kr-81m was measured as a function of flow in a dynamic phantom with a NaI crystal, suing both pure cyclotron-produced Rb-81 and commercially available samples with as much as 25% contamination from Rb-82m. The phantom was calibrated by measuring the flow-rate constants with Xe-133. No significant difference was found between the flow-rate constant measured with three pure samples. The ratio of the zero-flow Kr-81m count rate to the rate observed in the presence of flow showed excellent correlation with calibrated flow over a range of rate constant from 0 to 0.02 sec (-1). This study suggests that regional specific flow can be measured in vivo with currently available Nal detecting systems after the intra-arterial injection of Rb-81.

Blood Flow Velocity↗

PubMed1998

Laser-induced autofluorescence spectroscopy of dental caries.

We studied spectral autofluorescence characteristics of dental caries. A wide range of carious lesions revealed characteristic emission of endogenous fluorophores with strong fluorescence bands in the red spectral region when excited with 407 nm line radiation of a krypton ion laser. Healthy hard dental tissue exhibited no emission bands in the red. The fluorescence spectra, fluorescence excitation spectra as well as the reflectance spectra of carious lesions were found to be typical for fluorescent porphyrins, mainly protoporphyrin IX. A possible source of these porphyrins within carious tissues is bacterial biosynthesis. Non-invasive sensitive in vivo caries detection by means of appropriate excitation sources and porphyrin fluorescence detectors should be possible.

Dental Caries↗

PubMed2001

Intravitreal triamcinolone acetonide inhibits choroidal neovascularization in a laser-treated rat model.

OBJECTIVE: To determine if intravitreal triamcinolone acetonide (TAAC) inhibits experimental choroidal neovascular membranes induced by laser trauma in a rat model. METHODS: Nineteen anesthetized male Brown Norway rats received a series of 8 krypton red laser lesions per eye (647 nm, 0.05 seconds, 50 microm, and 150 mW in 17 rats, and 200 mW in 2 rats). One eye received an intravitreal injection of triamcinolone acetonide (20 microL, 0.8 mg) and the other eye received an injection of isotonic sodium chloride solution. Fundus and fluorescein angiography examinations occurred just before euthanasia and tissue processing for histopathology on day(s) 0, 1, 3, 7, 14, 21, 28, and 35. RESULTS: From the control eyes that underwent photocoagulation at 150 mW, 57 discrete lesions with definitive fibrovascular proliferations were observed at 21, 28, and 35 days, arising from a total of 72 spots placed (79% yield). From the control eyes that underwent photocoagulation at 200 mW, 11 discrete lesions with definitive fibrovascular proliferations were observed at 28 days, arising from a total of 16 spots placed (69% yield). In the TAAC-treated group, no fibrovascular proliferations were observed in the 72 lesions and in the 16 lesions created with 150 mW and 200 mW, respectively. CONCLUSION: Intravitreal TAAC is a potent inhibitor of fibrovascular proliferations in a rat model of choroidal neovascular membranes induced by laser trauma. CLINICAL RELEVANCE: This study corroborates previous investigations that propose TAAC as a potential treatment for choroidal neovascular membranes in humans.

Animals↗

PubMed2004

Predilection of the macular region to high incidence of choroidal neovascularization after intense laser photocoagulation in the monkey.

OBJECTIVE: To determine the key factors for creating a high incidence model of choroidal neovascularization (CNV) in the monkey. METHODS: Intense laser photocoagulation was performed in 8 eyes of 4 monkeys using krypton red and green-yellow and Alcon frequency-doubled diode ophthalmic lasers. Eight to 13 lesions were delivered to an area between the temporal vascular arcades in each eye. Development of CNV was monitored by fluorescein angiography at 2 and 4 weeks after laser treatment, and the results were correlated with histological analysis. RESULTS: A much higher incidence of CNV occurred in the macular region, which refers to an anatomic area equivalent to a mean +/- SD 2.5 +/- 0.4 times the horizontal diameter of the optic disc in the fundus. Regardless of the type of ophthalmic laser used, 72% of lesions developed fluorescein leakage within the macula, compared with 12% outside the macula (P<.001). By histological analysis, 89% of lesions developed microscopic CNV within the macula vs 22% outside the macula (P<.001). CONCLUSION: The macular region is predisposed to creation of laser-induced CNV in the monkey.Clinical Relevance The predilection of the macular region to a high incidence of laser-induced CNV may account for the high recurrence rate of subfoveal CNV after laser treatment in humans.

Animals↗

PubMed1986

Fluid-gas exchange and photocoagulation after vitrectomy. Indications, technique, and results.

We describe the indications, complications, and results of postvitrectomy fluid-gas exchange and laser photocoagulation for management of complicated vitreoretinal disease. Indications include proliferative vitreoretinopathy, vitreous opacities associated with proliferative diabetic retinopathy, giant retinal tear, recurrent rhegmatogenous retinal detachment, and trauma. Eyes treated with 50% sulfur hexafluoride gas rather than sterile air demonstrated a higher intraocular pressure on the first postexchange day, which was not a significant source of disease. There was no statistically significant difference in retinal reattachment between eyes treated with gas and those treated with air. Fluid-gas exchange in eyes with partial or total retinal detachment resulted in total or partial retinal reattachment, with the macula attached in 82% of cases within the first 48 hours following exchange. Final reattachment rate, with a mean follow-up of 8.9 months (range, six to 36 months), was 55%. In eyes with proliferative vitreoretinopathy, the combination of postoperative argon or krypton laser photocoagulation with fluid-gas exchange was associated with a final reattachment rate of 75%. Postoperative fluid-gas exchange and photocoagulation appear to be safe and effective advances in the treatment of complicated vitreoretinal diseases requiring vitrectomy.

Body Fluids↗

PubMed1986

Excimer laser ablation of the lens.

Ablation of the bovine crystalline lens was studied using radiation from an excimer laser at four ultraviolet wave lengths as follows: 193 nm (argon fluoride), 248 nm (krypton fluoride), 308 nm (xenon chloride), and 351 nm (xenon fluoride). The ablation process was quantitated by measuring mass ablated with an electronic balance, and characterized by examining ablation craters with scanning electron microscopy. The highest ablation rate was observed at 248 nm with lower rates at 193 and 308 nm. No ablation was observed at 351 nm. Scanning electron microscopy revealed the smoothest craters at 193 nm while at 248 nm there was vacuolization in the crater walls and greater disruption of surrounding tissue. The craters made at 308 nm did not have as smooth a contour as the 193-nm lesions. The spectral absorbance of the bovine lens was calculated at the wavelengths used for ablation and correlated with ablation rates and thresholds. High peak-power, pulsed ultraviolet laser radiation may have a role in surgical removal of the lens.

Animals↗

PubMed1987

Laser photocoagulation in the acute retinal necrosis syndrome.

Acute retinal necrosis (ARN) is a syndrome of fulminant necrotizing vaso-occlusive retinitis associated with a high incidence of retinal detachment due to retinal breaks and vitreous traction. We performed argon or krypton laser photo-coagulation to demarcate areas of active retinitis as prophylaxis against retinal detachment in five patients with ARN. Patients were concomitantly treated with antiviral agents, systemic steroids, and antiplatelet therapy. One patient required multiple additional treatments as retinal necrosis progressed. The retinas remained attached in all five patients over a mean follow-up period of 15 months. By creating a chorioretinal adhesion in areas of potential retinal break formation, laser photocoagulation may be an effective prophylaxis against retinal detachment in ARN.

Acute Disease↗

PubMed1989

A new model of experimental choroidal neovascularization in the rat.

Choroidal neovascularization in rat eyes was induced by krypton laser photocoagulation. Lesions were studied weekly by ophthalmoscopy, fundus photography, and fluorescein angiography. Morphologic correlation was provided by serial sectioning of lesions for light and transmission electron microscopy. In addition, vascular casts were prepared for scanning electron microscopy. Choroidal neovascularization occurred in 25 (60%) of 42 lesions, as evidenced by growth of capillaries through breaks in Bruch's membrane. In addition, 24 (28%) of 86 lesions studied by fluorescein angiography demonstrated leakage. This study provides the most complete angiographic, histologic, and ultrastructural documentation of experimental choroidal neovascularization in the rat. This model may be useful for in vivo studies of choroidal angiogenesis and its modulation via drug therapy.

Animals↗

PubMed1996

Clinicopathologic correlation of submacular membranectomy with retention of good vision in a patient with age-related macular degeneration.

We present the clinicopathologic features of the eye of a patient with age-related macular degeneration who underwent submacular membranectomy and had retention of good visual acuity for almost 4 years despite recurrent choroidal neovascularization treated with krypton laser photocoagulation and mild expansion of the laser lesion with time. Histopathologic study of the surgically removed membrane from the right eye disclosed a thin fibrovascular membrane lined by retinal pigment epithelium on one surface. Microscopic examination of the right eye obtained post mortem disclosed a 2.75-mm (horizontal) x 2.1-mm (vertical) retinal pigment epithelium defect with overlying photoreceptor cell atrophy centered on the temporal parafoveal area, and a 0.6 x 0.1-mm subretinal pigment epithelium fibrovascular membrane with an area of retinal pigment epithelial hyperplasia and vascularization from the retina 0.4 mm temporal to the fovea. Basal laminar deposit was present in the region of the fovea and nasal parafoveal area.

Aged↗

PubMed1997

Clinical evaluation of a method for detecting superficial surgical transitional cell carcinoma of the bladder by light-induced fluorescence of protoporphyrin IX following the topical application of 5-aminolevulinic acid: preliminary results.

BACKGROUND AND OBJECTIVE: In bladder cancer, conventional white light endoscopic examination of the bladder does not provide adequate information about the presence of "flat" urothelial lesions such as carcinoma in situ. In the present investigation, we examine a new technique for the photodetection of such lesions by the imaging of protoporphyrin IX (PpIX) fluorescence following topical application of 5-aminolevulinic acid (ALA). STUDY DESIGN/MATERIALS AND METHODS: Several hours after bladder instillation of an aqueous solution of ALA in 34 patients, a Krypton ion laser or a filtered Xenon arc-lamp was used to excite PpIX fluorescence. Tissue samples for histological analysis were taken while observing the bladder wall either by means of a video camera, or by direct endoscopic observation. RESULTS: A good correlation was found between the PpIX fluorescence and the histopathological diagnosis. On a total of 215 biopsies, 143 in fluorescent and 72 in nonfluorescent areas, all visible tumors on white light cytoscopy appeared in a bright red fluorescence with the photodetection technique. In addition, this method permitted to discover 47 unsuspected carcinomatous lesions on white light observation, among which 40% were carcinoma in situ. CONCLUSION: PpIX fluorescence induced by instillation into the bladder of 5-ALA is an efficient method of mapping the mucosa in bladder carcinoma.

Administration, Cutaneous↗