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Query: UMLS:C0034065 (pulmonary embolism)
 14,979 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Krypton lung-imaging is considered the ventilation procedure of choice when it is available. Aerosol and krypton wash-in images both reveal regional abnormalities of ventilation, but the aerosol images also disclose evidence of major airways disease. Xenon wash-out images are probably the most sensitive indicators of regional abnormalities of ventilation and/or small airways obstruction, whereas xenon wash-in images are far less sensitive and may be frequently misinterpreted. The Tc-DTPA aerosol inhalation procedure is perferred over xenon and krypton ventilation imaging for routine use immediately after a perfusion examination in pulmonary embolism suspects. This combined method provides the referring physician with the necessary diagnostic information quickly and with around-the-clock availability. In our opinion, this new aerosol procedure deserves wider application in the diagnosis and management of pulmonary disease. Lung imaging procedures, performed after th inhalation of 99mTechnetium labeled aerosols, 133Xenon and and 81mKrypton gases, were used to visualize the sites of airway obstruction and regional abnormalities of ventilatory function in normal volunteers, patients with obstructive airway disease and pulmonary embolism suspects. This chapter presents intercomparisons of these three methods regarding their functional significance, diagnostic merits, and limitations. A new nebulizer-radioaerosol delivery system is described. Test agent kits are inexpensive and readily available for on site assembly. Currently, we consider radioaerosol imaging in multiple views as more informative and suitable for routine use than xenon methods to detect regional abnormalities of the airways and ventilatory function. The krypton procedure is preferred in pulmonary embolism suspects because it requires far less patient cooperation than the xenon and aerosol methods and the lung images disclose regional ventilatory impairment quickly and accurately. However, krypton gas is cyclotron-produced and not yet commercially available.
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PMID:Inhalation lung imaging with radioactive aerosols and gases. 74 65

The authors report their experience with the use of Tc-99m DTPA aerosol following a perfusion lung scan. The study includes 422 consecutive patients with suspected pulmonary embolism. The final diagnosis was determined by (a) clinical follow-up for 2 months or more, (b) pulmonary angiography, or (c) autopsy. There were 79 patients (19%) who had a normal or near-normal perfusion study and in whom no aerosol study was required. Interpretation groups were classified and divided as follows: Normal or low probability 281 (66.5%) High probability 75 (18.0%) Intermediate 60 (14.0%) Technically inadequate 6 (1.5%) There was autopsy or angiographic confirmation of 72 patient studies with confirmation of the scan diagnosis in 29 of 31 classified as normal or low probability and 24 of 25 classified as high probability. The background perfusion albumin activity was not computer-subtracted from the combined aerosol-perfusion image. Technical improvements included the use of eight standard views for both the perfusion and the subsequent aerosol scan, and the use of 75 mCi (2,775 MBq) of Tc-99m DTPA in the radioaerosol nebulizer. This allowed for easy accumulation of more than three times the count rate in a posterior aerosol image when compared with the previous posterior perfusion image. The authors' experience shows that the perfusion lung scan followed by this radioaerosol technique is a reliable means to evaluate suspected pulmonary embolism.
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PMID:Utility of Tc-99m DTPA aerosol inhalation scans following perfusion lung scans in the diagnosis of pulmonary embolism. 218 Jun 7

Technetium-99m diethylenetriaminepentaacetic acid ([99mTc]DTPA) radioaerosol scans performed on 21 consecutive artificially ventilated patients were compared to 50 similar scans performed on patients breathing without mechanical assistance. All patients were referred for evaluation of suspected pulmonary embolism. The comparison revealed increased extrathoracic tracheal and mediastinal tracheal deposition but less central bronchial deposition in the artificially ventilated patients. Peripheral penetration in both groups of patients was excellent. Within the artificially ventilated group, peripheral penetration of activity seemed equally good in patients receiving positive-end expiratory pressure ventilation (n = 14) and those ventilated with normal pressures (n = 7). The frequency of regions in which aerosol activity (A) was present in the same zone as a perfusion (P) defect was the same in the controls and artificially ventilated patients (12% against 14%) but the frequency of the reverse type of mismatch (i.e., P greater than A) was significantly higher in the artificially ventilated group (42% against 14%, p less than 0.001). The results suggest that [99mTc]DTPA aerosol scans in artificially ventilated patients are associated with good peripheral penetration of activity and frequently yield valuable clinical information.
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PMID:The utility of technetium-99m DTPA inhalational scans in artificially ventilated patients. 240 94

In two patients with chronic unilateral massive pulmonary embolism, we studied the pulmonary epithelial permeability by measuring the clearance of inhaled and deposited 99mTc-DTPA aerosol. The clearances from the embolized lungs with complete or almost complete occlusion of a main pulmonary artery were more rapid than the clearances from the normal lung, which had an increased blood flow. This suggests that in chronic, embolized lung (1) the bronchial flow clears the inhaled solutes, and (2) there is an increase of epithelial permeability.
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PMID:Chronic thromboembolic occlusion of main pulmonary artery does not reduce the lung clearance of 99mTc-DTPA. 265 4

The application of 99mTc-DTPA radioaerosols to a variety of clinical disorders is described. With the development of simple equipment that can deliver very small droplets, this approach has become increasingly popular for measurements of the distribution of ventilation in patients with obstructive lung disease and suspected pulmonary embolism. In addition, by determining the rate at which the radionuclide is cleared from the lung, information has been obtained concerning the permeability of the pulmonary epithelium to extracellular indicators. Accelerated clearance rates have been found in patients with a variety of chronic interstitial lung diseases indicating that epithelial permeability is increased. Accelerated clearance rates have also been found with acute inflammation of the lung such as the adult respiratory distress syndrome and pneumocystis pneumonia. Furthermore, rapidly reversible increases in 99mTc-DTPA clearance occur in smokers and may be related to the inflammatory changes that contribute to the development of emphysema.
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PMID:99mTc-DTPA aerosol deposition and clearance in COPD, interstitial disease, and smokers. 329 74

Pulmonary emboli lead to regional limitation of pulmonary artery perfusion, often without affecting distribution of ventilation. We have studied the effect of this regional reduction of pulmonary artery perfusion on the integrity of epithelium of alveoli (and possibly bronchioli). Integrity of alveolar epithelium was assessed by measuring regional rates of clearance from lung to blood of an inhaled aerosol of a small molecular weight solute, 99mTc DTPA (technetium-99m diethylene-triamine-pentaacetate). Ten patients with pulmonary emboli were studied, where the diagnosis was made from 'mismatching' seen on ventilation (V) and perfusion (Q) lung scintigraphy. Rates of clearance of DTPA in regions with normal V/Q ratios were compared with embolized regions with high V/Q ratios. Clearance rates were increased in embolized regions (V/Q ratio greater than 1): 2.59 +/- (SD) 0.89% X min-1, compared with normal regions (V/Q ratio less than 1): mean 1.39 +/- 0.60% X min-1 (p less than 0.01). In repeat studies in nine patients (one died), after intervals between 2 and 12 weeks, the V/Q ratio of previously embolized regions decreased towards unity in all nine patients, suggesting resolution. The differences in clearance rates for DTPA between normal and embolized regions decreased in association with this return towards normal of V/Q ratios. We surmise that reduction in pulmonary artery perfusion which occurs in pulmonary embolic disease alters the integrity of the alveolar (and possibly bronchiolar) epithelium. This effect is largely reversible, recovering with return of pulmonary artery perfusion.
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PMID:Clearance of inhaled 99mTc DTPA from regions of the lung recently affected by pulmonary embolus. 351 68

The regional distribution of [99mTc]DTPA aerosol was compared with that of 133Xe (n = 30) and krypton (n = 24) in a group of patients with suspected pulmonary embolism. All patients had an aerosol study using a recently available commercial generator system, a ventilation study with one of the gases, and perfusion imaging. Regional information was assessed visually on xenon, krypton, and aerosol studies independently by considering each lung as three equal-sized zones. In addition, gas ventilation findings peripheral to regions of aerosol turbulence ("hot spots") were evaluated. Only 64% of the zones were in complete agreement on xenon and aerosol. Most of the discordance between xenon and aerosol was accounted for by minor degrees of 133Xe washout retention in zones that appeared normal in the aerosol study. An agreement rate of 85% was noted between 81mKr and aerosol regionally. The regions of discordance between aerosol and gas studies, however, usually were associated with unimpressive perfusion defects that did not change the scintigraphic probability for pulmonary embolism in any patient. Regarding zones of aerosol hyperdeposition, 76% had associated washout abnormalities on xenon; however, there was no correlation between the presence of these abnormalities or perfusion abnormalities. The results confirm the high sensitivity of 133Xe washout imaging, but suggest that radioaerosol imaging will detect most parenchymal abnormalities associated with perfusion defects of significance.
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PMID:Regional comparison of technetium-99m DTPA aerosol and radioactive gas ventilation (xenon and krypton) studies in patients with suspected pulmonary embolism. 352 12

Two radiopharmaceuticals, 99mTc-DTPA (D) and 99mTc-rhenium sulfur (R), were evaluated with a nebulizer delivering submicronic particles. Seventy-seven patients were examined (42 D, 35 R). For all patients, the examination began with a ventilation study. Immediately after the last ventilation view, 99mTc MAA was injected. Aerosol performance was assessed in 37 D and 17 R. Nebulization yield was 8.98% for D and 9.31% for R. A lung clearance study was performed in 12 patients for D and in 12 different patients for R. The lung clearance was 0.22%/min for R and 2.35%/min for D. The quality of ventilation and the quantification of bronchial and gastric activity were evaluated; the difference between the two groups was not statistically significant. It may be concluded that radioaerosols allow good quality images to be obtained. The yield of the nebulizer is adequate, so that nebulization of 20 mCi delivers approximately 2 mCi of aerosol activity to the lung. When pulmonary embolism is being investigated, R, due to its slower lung clearance, would appear to be preferable to D for patients suspected of increased bronchoalveolar permeability, especially if the time between nebulization and recording is greater than 10 min.
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PMID:99mTc-DTPA and 99mTc-rhenium sulfur aerosol compared as adjuncts to perfusion scintigraphy in patients with suspected pulmonary embolism. 353 18

To evaluate the clinical value of radioaerosol imaging, 156 patients with suspected pulmonary embolism (PE) were studied. In 25 patients, a preperfusion xenon-133 (Xe-133) study was compared with a postperfusion study using Tc-99m DTPA aerosol. It was found that they were of equal value most of the time (56%), but that the aerosol study was more often helpful. Because of this, and the technical ease of using six standard views with radioaerosol, the series was completed using perfusion scintigraphy followed by radioaerosol images. In 19 patients the perfusion scintigraphy with Tc-99 macroaggregated albumin (Tc-99m MAA) was normal or nearly normal and no aerosol study was required. Tc-99m DTPA aerosol images were satisfactory when the count rate was at least twice and preferably three times that of the previous perfusion study. There were 17 studies (11%) classified as intermediate. There were 26 patients classified as high probability for PE, and angiographic or autopsy correlation was available in 14. All of the 14 proved to have PE. In the 113 patients classified as low probability, there were ten with angiographic or autopsy correlation. In the ten, there was one patient with a small pulmonary embolus found at autopsy. Clinical follow-up for over two months confirmed the absence of PE in the remainder of this group. Aerosol studies have proven technically easier to perform and a satisfactory substitute for xenon imaging in suspected PE.
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PMID:Clinical experience with technetium-99m DTPA aerosol with perfusion scintigraphy in suspected pulmonary embolism. 354 7

Fetal dose estimates from Tc-99m MAA and Tc-99m DTPA aerosol were calculated using two methods. These calculations show that the average fetal dose decreases as gestational age (or fetal size) increases. Although the resultant dose estimates exceed those previously reported by severalfold, the risk to mother and fetus from undiagnosed pulmonary embolism far outweighs the risk to the fetus from the radiation exposure.
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PMID:Fetal dosimetry from pulmonary imaging in pregnancy. Revised estimates. 376 34


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