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PubMed1986

Iridotomy with red krypton laser.

Iridotomy with red krypton laser instead of blue-green argon laser was performed on 68 eyes with various types of angle-closure glaucoma. Patent iridotomy was obtained in all the eyes, mostly in one working session. In eight eyes secondary closure by pigment needed reopening with a few applications at the iridotomy site. There were no immediate or late complications of importance, the main advantage of the technique being the avoidance of the corneal epithelial and endothelial burns which commonly occur during argon laser iridotomy, particularly when the anterior chamber is shallow.

Glaucoma↗
PubMed1982

Effects of acute and long-term bronchodilator treatment on regional lung function in asthma assessed with krypton-81m and technetium-99m-labelled macroaggregates.

We have investigated the effect of acute and long-term bronchodilator treatment on the distribution of ventilation and perfusion in 15 asthmatics using a gamma camera, krypton-81m (for ventilation) and technetium-99m macroaggregate (for perfusion). Individual peak expiratory flow (PEF) values before bronchodilation were slightly or moderately below the predicted values. The simultaneous ventilation images (analysed visually) showed areas of delayed ventilation in all patients (mean distribution score on 3-point scale 2.1). After isoprenaline inhalation (240 micrograms) the mean PEF increased by 24%, but the distribution of ventilation remained virtually unchanged in all patients (mean score 2.0). Simultaneously defects in perfusion could be seen in all patients (mean score 1.5). After intensive treatment, when the mean PEF increased by a further 29%, the distribution scores of ventilation and perfusion fell to 0.8 and 0.9, respectively. The results indicate that, without intensive and long-term treatment, appreciable inequality of ventilation and perfusion are usual consequences of asthma; and suggest that although larger airways are dilated by isoprenaline inhalations residual bronchial obstruction may still remain in some smaller airways, maintaining uneven distribution. Perfusion disturbances seem to be secondary to changes in regional ventilation.

Adult↗
PubMed1986

Tomography of regional ventilation and perfusion using krypton 81m in normal subjects and asthmatic patients.

Single photon emission computed tomography, a rotating gamma camera, and continuous inhalation or infusion of krypton 81m (half life 13 seconds) were used to measure regional ventilation (V), perfusion (Q), and ventilation-perfusion (V/Q) ratios in five normal subjects in supine, prone, and lateral decubitus postures and in three asthmatic patients (supine posture only) before and after inhalation of 2.5 mg nebulised salbutamol. Vertical and horizontal gradients of V, Q, and V/Q were examined at three levels in each lung in regions of 1.9 cm3 size. In normal subjects V and Q increased along the axis of gravity in all postures and at all levels in the lung except for V in the prone position. Smaller horizontal gradients were found with an increase in V and Q from caudal to cranial--again except in the prone posture, where the gradient was slightly reversed. Constraint to outward motion of the ventral chest and abdominal wall is the most likely explanation for the different behaviour in the prone posture. In chronic asthma the vertical gradients of V and V/Q were the reverse of normal, but the Q gradient was normal. Bronchodilator treatment did not affect the vertical or horizontal gradients significantly, but analysis of individual regions showed that, relatively, V/Q worsened in 42% of them; this was associated in two thirds with an increase in fractional Q. After inhalation of beta agonist local vasodilatation may influence V/Q ratios in some units more than bronchodilatation.

Adult↗
PubMed1979

Krypton-81m: a better radiopharmaceutical for assessment of regional lung function in children.

Krypton-81m, an inert, radioactive gas with a physical half-life of 13 seconds was used to evaluate regional lung ventilation in 25 pediatric patients. The results suggest that Kr-81m has several advantages over previous methods employing xenon-133. These include: more favorable physical characteristics for imaging with present scintillation cameras; ease of performance of the examinations; improved resolution and multiple views with better detection and localization of abnormalities; and a much lower dose to the patient.

Adolescent↗
PubMed1988

Interpretation of the krypton-81m dynamic series: the distribution of a tidal breath.

Lung scans during cyclic breathing of krypton-81m, an isotope with a 13-s half-life, were acquired in "list mode," where both temporal and spatial information are preserved. Subjects in the left lateral decubitus position breathed with two tidal volumes at each of two frequencies. Profiles of total activity over the acquisition period were examined. They showed little effect of frequency or tidal volume on the distribution of air between dependent and non-dependent regions. Dynamic series for ensemble-averaged breaths were constructed. The regional flow per unit volume was shown to correspond to the time derivative of the regional activity of the dynamic series divided by the corresponding activity. Both the relative timing of the gas flow to different lung regions and the flow per unit volume as a function of time were obtained from the dynamic series. The dependent lung was seen to be better ventilated throughout the respiratory cycle except for brief periods at the start of inspiration and the end of expiration. Most of the dead-space gas can be construed to enter and leave the dependent lung.

Female↗
PubMed2006

Effect of low-xenon and krypton supplementation on signal/noise of regional CT-based ventilation measurements.

Xenon computed tomography (Xe-CT) is used to estimate regional ventilation by measuring regional attenuation changes over multiple breaths while rebreathing a constant Xe concentration ([Xe]). Xe-CT has potential human applications, although anesthetic properties limit [Xe] to <or=35%. We investigate effects of lower [Xe], including a low [Xe]-krypton (Kr) combination, on time constant (TC) determination. Six anesthetized sheep were scanned prone and supine using multidetector row CT. Lungs were imaged by respiratory gating during washin of a 30%, 40%, 55% Xe, and a 30% Xe/30% Kr mixture. Using Kr avoids unwanted effects of Xe. Mean TCs, coefficients of variation (CV), and half confidence intervals (CI)/mean served as indexes of sensitivity to noise. Mean supine and prone TCs of three [Xe] values were not significantly different. Average CVs of TCs increased from 57% (55% Xe), 58% (40% Xe), and 73% (30% Xe) (P < 0.05: paired t-tests; 30% Xe vs. higher [Xe]). Monte Carlo simulation indicated a CV based on inherent image noise was 8% for 55% Xe and 17% for 30% Xe (P < 0.05). Adding 30% Kr to 30% Xe gave a washin signal equivalent to 40% Xe. Half CI/mean using the 30% Xe/30% Kr mixture was not significantly different from 55 and 40% Xe. Although average TCs were not affected by changes in [Xe], the higher CV and half CI/mean suggested reduced signal-to-noise ratio at the 30% [Xe]. The 30% Xe/30% Kr mixture was comparable to that of 40% Xe, providing an important agent for CT-based assessment of regional ventilation in humans.

Administration, Inhalation↗
PubMed1996

Simplified model of krypton laser-induced thrombotic distal middle cerebral artery occlusion in spontaneously hypertensive rats.

BACKGROUND AND PURPOSE: The effects of thrombotic occlusion of the middle cerebral artery on compromised ischemic tissue may be different from and more severe than those of cerebral ischemia induced by mechanical occlusion of the artery. Photothrombosis, which is based on photochemical damage to the endothelium and subsequent platelet aggregation, is an efficient method to induce thrombosis in vivo. This study aimed to improve and simplify this unique method for an ischemia model of middle cerebral artery occlusion in rats. METHODS: Male spontaneously hypertensive rats (5 to 6 months old, 300 to 450 g) were anesthetized with halothane, endotracheally intubated, and mechanically ventilated. A krypton laser operating at 568 nm was used to irradiate the exposed distal middle cerebral artery with an intact dura above the rhinal fissure. The photosensitizing dye rose bengal (20 mg/kg body wt) was administered intravenously over 90 seconds starting simultaneously with 4 minutes of laser irradiation at a power of 20 mW to cause thrombotic occlusion of this artery. RESULTS: The irradiated middle cerebral artery was completely occluded by intraluminal thrombi within 3 minutes after simultaneous laser irradiation and rose bengal infusion. Thrombosed materials were not stained by phosphotungstic acid-hematoxylin stain (ie, aggregated platelets lacked apparent fibrin). The mean volume of 3-day-old infarction, indicated by the lack of staining with 2,3,5-triphenyltetrazolium chloride, was 84.8 +/- 17.4 mm3 (mean +/- SD, n = 6). CONCLUSIONS: We demonstrated a reproducible and minimally traumatic model of brain infarction induced by the thrombotic distal middle cerebral artery occlusion in rats.

Animals↗
PubMed1980

Quantitative approach to the study of regional lung function in children using krypton 81m.

Krypton 81m has many advantages for paediatric lung imaging, although the proper interpretation of ventilation and perfusion lung scans requires the quantitative analysis of the steady state images and clearance curves. Both the theory and practice are described and illustrated by means of 11 paediatric cases aged from 18 days to 14 years. It was possible to calculate the regional distributions of ventilation and perfusion and the normalized ventilation-perfusion (V/Q) ratios. Of greater functional significance was the detection of differences between the clearance rates of inhaled and infused 81Krm within single regions, since such differences reflected the dispersion of V/Q ratios amongst lung units within individual regions.

Adolescent↗
PubMed1988

Regional blood flow in human tumours measured with argon, krypton and xenon.

Blood perfusion in 19 superficial tumour metastases was measured by injecting three tracers, 41Ar, 85Krm and 135Xe or 133Xe, simultaneously into the tissue. The blood flow rate was calculated from the constants of the biexponential functions fitted to the measured counts. The mean blood flow in the 19 tumours studied was 18 ml/(100 g min) (SD +/- 10). Alternatively, the relative partition coefficients of argon, krypton and xenon were calculated from the equations obtained using compartmental analysis. The mean values for the ratios of the partition coefficients of these nuclides were found to be between 0.82 and 1.07.

Argon↗
PubMed1992

99Tcm-Technegas and krypton-81m ventilation scintigraphy: a comparison in known respiratory disease.

Krypton-81m gas, by virtue of its imaging characteristics, is often considered the "gold standard" for ventilation scintigraphy but its use is restricted by its high cost and limited availability. The new radiopharmaceutical 99Tcm-Technegas, a suspension of ultrafine technetium-99m labelled carbon particles, produces high-quality images of ventilation and has the advantage of continuous availability. As part of our evaluation of Technegas the two were compared in 40 patients with a variety of established respiratory diseases. Disparities were seen in five patients in five diagnostic groups and may be a consequence of the differing physical properties of the two agents and the different inhalation techniques used. In addition two interesting features were noted on the Technegas images. (1) Hot spots were seen in 50% of patients, particularly in those with a degree of airways obstruction; (2) preferential basal deposition of activity was seen in 30%, particularly in patients with idiopathic pulmonary fibrosis. Both features were significantly associated with parameters of pulmonary function indicating obstructive lung disease in the former case and restrictive lung disease in the latter.

Adult↗
PubMed1979

Exchange of krypton-85 between the blood vessels of the human uterine adnexa.

A miniature Geiger-Müller probe was inserted into one ovary of 8 women undergoing hysterectomy. A control probe was inserted into the other ovary of 2 of the women. Krypton-85 in 0.15 M-NaCl was infused into the adjacent utero-ovarian vein and the radioactivity was registered for 5--14 min after the infusion. An increase of radioactivity was recorded in the ovary in 5 cases. In one of the women with 2 probes, no increase in radioactivity was observed in the control ovary. The results show a local transfer of gas from the ovarian branch of the uterine vein into the adjacent ovary, which may be due to a countercurrent exchange mechanism between the vessels of the human uterine adnexa.

Adult↗
PubMed1981

Krypton-81m ventilation scanning: acute respiratory disease.

From experience with 700 patients undergoing ventilation and perfusion lung scanning with krypton-81m/technetium-99m technique, 34 patients suffering from nonembolic acute respiratory disease were selected for review. In 16 patients with pneumonia, all had defects of ventilation corresponding to, or larger than, the radiologic consolidation. In 13 patients there were some preservation of perfusion in the consolidated region. In two of the three patients with matched defects, the pneumonia was of long standing. In seven patients with collapse or atelectasis and in 11 patients with acute reversible bronchial obstruction and normal volume lungs, a similar pattern of ventilation and perfusion was observed.

Adult↗
PubMed2001

Comparison of deposition images obtained by use of an ultrafine 99m-technetium-labeled carbon dry aerosol with ventilation images obtained by use of 81m-krypton gas for evaluation of pulmonary dysfunction in calves.

OBJECTIVE: To characterize the accuracy of an ultrafine 99m-technetium-labeled carbon dry aerosol for use in assessment of regional ventilation in calves with pulmonary dysfunction. ANIMALS: 7 Belgian White and Blue calves. PROCEDURE: The ultrafine aerosol was assessed by comparing deposition (D) images with ventilation (V) images obtained by use of 81 m-krypton (81mKr) gas via D-to-V ratio (D:V) image analysis in calves during spontaneous breathing (SB) and during experimentally induced pulmonary dysfunction (ePD). RESULTS: Mismatching index (LrTot) calculated on the D:V images revealed a good match (LrTot, 0.96 +/- 0.01) between D and V distribution patterns in calves during SB. Calculation of the ultrafine aerosol penetration index relative to 81mKr (PIRel) revealed preferential distribution of the ultrafine aerosol in lung parenchyma (PIRel, 1.13 +/- 0.11). In ePD, heterogeneity in the D:V distribution was observed (LrTot, 0.78 +/- 0.10) as a result of ultrafine aerosol particles impaction in airways as indicated by PIRel (0.66 +/- 0.16) and a proportion of pixels more radioactive in D images, compared with V images, that was located in the central part of the lung (475 +/- 77% in ePD vs 32.8 +/- 5.7% in SB). However, this central deposition did not prevent visual examination of the entire ventilated lung. CONCLUSIONS AND CLINICAL RELEVANCE: The ultrafine aerosol appears suitable for use in examination of ventilated parts of lungs of cattle, even those with impaired pulmonary function. However, airway impaction of ultrafine aerosol particles impedes the quantification of regional ventilation in cattle with abnormal lung function.

Aerosols↗
PubMed1992

Airway responses to repeated exercises detected by krypton-81m in asthmatic children.

A repeated exercise program was used to test 7 asthmatic children for changes in ventilation. These changes were examined by continuously inhaled Krypton-81m and compared in subjects with positive and negative refractoriness, as defined by forced expiratory volume in 1 second (FEV1). Three of the seven patients showed significant refractoriness (% reduction in FEV1 > 50%). After the first exercise, they showed one or two ventilation defects which improved after the second exercise. The patient with incomplete refractoriness showed similar results. On the contrary, subjects without refractoriness showed several ventilation defects which fluctuated after the second or third exercise program. One defected area improved after the second exercise session, but deteriorated after the third; and another area deteriorated after the second exercise and improved after the third. It was concluded that approximately half of the patients were refractory in view of FEV1, but that they were all refractory in view of regional ventilation 81mKr images.

Acetylcholine↗
PubMed2000

Krypton-81m ventilation and technetium-99m macroaggregated albumin perfusion scintigraphy for detection of pulmonary embolism: the first experience in Taiwan.

BACKGROUND: This study was designed to assess whether the self-made (Institute of Nuclear Energy Research, Taiwan) krypton (Kr)-81m could be used as a ventilation agent to detect patients with suspected pulmonary embolism (PE). In addition, xenon (Xe)-133 ventilation scintigraphy was also performed for comparison. METHODS: Forty patients with suspected PE were studied. Each patient received Kr-81m ventilation, Xe-133 ventilation and technetium (Tc)-99m macroaggregated albumin (MAA) perfusion studies on the same day. Images were judged using the criteria of the modified Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). For those with a high or intermediate probability of PE on lung scans and normal pulmonary function tests, anticoagulants were given and patients were monitored with Tc-99m MAA perfusion studies after treatment. The final diagnosis was based on chest radiography, pulmonary function tests and lung scans. RESULTS: All 40 patients successfully underwent lung scans. Of these, 11 had PE. Ten of the 11 cases were detected using Kr-81m ventilation and Tc-99m MAA perfusion studies, resulting in a sensitivity of 91%. Seven of 11 cases were detected using Xe-133 ventilation and Tc-99m MAA perfusion studies, resulting in a sensitivity of 64%. Of the 11 patients with PE, four had PE alone; Kr-81m and Xe-133 results agreed in three patients, but Kr-81m detected PE in the remaining patient. Of the remaining seven patients who suffered from PE with obstructive airway disease, Kr-81m and Xe-133 agreed in four, but Kr-81m detected PE in another two patients and one case was missed by both studies. CONCLUSIONS: Self-made Kr-81m was safe and effective for ventilation scintigraphy in humans. When Kr-81m was used for the detection of PE, it was particularly advantageous when PE occurred in small areas of the lungs or when the patient with PE had concurrent obstructive airway disease.

Adolescent↗
PubMed1990

The treatment of foveal central serous choroidopathy by krypton red laser.

We present 24 patients with recent foveal central serous choroidopathy. Only those in whom the leakage site was located within a radius of 250 microns from the foveal center were included in this study. All patients were treated with the krypton red laser (647 nm) within a week of the clinical diagnosis. At the end of the follow-up, 70.8% of the patients had a visual acuity of 6/8.5 or better, and an overall visual improvement was found in 83.3%. In 90% of the patients whose vision improved, significant absorption of subretinal fluid was seen within three weeks and in 10% within four weeks. No evidence of any macular pathology complicating the laser treatment was found at the end of the follow-up period of at least 36 months.

Adult↗
PubMed1985

Vision parameters in krypton and laser photocoagulation of subfoveal neovascular membranes.

A prospective study of 78 patients, treated with krypton red laser (KRL) photocoagulation, who had senile macular degeneration (SMD) and subretinal neovascular membranes (SRNVM) located within 200u of the center of the foveal avascular zone (FAZ), was undertaken to determine if complete eradication of the SRNVM would minimize the resultant foveal scar size and retain the maximal useful functional vision as compared to untreated fellow eyes with a disciform scar. The typical patient profile with SMD and subfoveal SRNVM included: average age, 73.6 years; caucasian, 99%; females, 62%; lightly pigmented iris, 70%; hyperopic refractive error, 93%; and evidence of bilateral involvement with either predisciform or disciform lesions, 73%. In comparing eyes treated with KRL having 100% FAZ involvement with fellow untreated eyes having disciform scars, the latter had poorer average visual acuity (44% vs 100% less than or equal to 20/200), scars which were an average of five times larger (8.4 vs 38.6 sq mm) and scotomas which were an average of six times larger (15.7 vs 90 sq cm) as determined by new microcomputer technology. In all bilaterally affected cases, eyes with smaller scars and scotomas required less magnification from a low vision aid to read continuous standardized 1M print. Sixteen of 17 patients (94%) preferred the low vision aid for their treated eye. These preliminary results suggest that treatment of SRNVM within the FAZ using KRL may be successful in arresting the progressive macular hemorrhagic-exudative damage typical of untreated cases which culminate in loss of central visual function. Successful treatment, by preserving areas of paracentral fixation, can enhance the chances of visual rehabilitation using conventional low vision aids.

Aged↗
PubMed1985

Argon vs krypton laser lesions: is the wavelength more important than the power.

Conventionally, unnecessarily intense laser power is advocated for the treatment of subretinal neovascular membranes. Among the four variables determining the adequacy of the laser lesion, namely spot size, duration of exposure, wavelength, and power, the latter is seldom if ever directly considered. Patients with subretinal neovascular membranes may be satisfactorily treated using the unfiltered argon blue-green laser wavelengths and reduced power as an additional option to the filtered argon green and wavelength or krypton yellow or red wavelengths.

Adult↗