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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

In 133Xe ventilation studies the 81-keV gamma photon emitted is a major disadvantage for imaging. Using a lung model with the same attenuation coefficient as inflated lung, we compared 133Xe with 127Xe to determine the smallest "lesion" that could be imaged at different places within the lung. With the "lung lesion" directly against the collimator, the lesion had to be 10 ml in volume in order to be seen with 127Xe, but with 133Xe "lesion" had to be 30 ml. Xenon-127 gave better resolution, no matter where the lesion was placed within the lung. Xenon-127 was not better than 133Xe in resolving a lead bar phantom. When 133Xe was used with 99mTc in a model of pulmonary embolism, a "ventilation defect" was apparent even though the distribution of xenon was even throughout the model. This artifact was not seen when the 127Xe model was imaged.
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PMID:Xenon-127, a comparison with xenon-133 for ventilation studies. 2418 55

Xenon-133 and xenon-127 were compared by performing ventilation studies with both radionuclides in 19 patients with a variety of lung diseases. Assessment of the counting rate over the chest, relative to the radioactivity in the lungs, permitted the evaluation of each isotope in terms of usable photons detected by a scintillation camera with a large field of view and appropriate collimation. A greater photon yield was obtained with Xe-127. Markedly improved resolution was shown by measurement of a line phantom, but was not apparent on subjective appraisal of scintiphotos except in the washout phase. Xenon-127 appears to be preferable to Xe-133 because of the higher counting rates, lower patient radiation dose, and longer shelf life. In addition, a prior perfusion study using a Tc-99m radiopharmaceutical does not affect the quality of a Xe-127 ventilation study. The use of Xe-127 therefore permits the selection for ventilation studies of only those patients with suspected pulmonary embolism, and eliminates unnecessary radiation exposure. A further improvement in image quality obtained with Xe-127 should be possible with certain modifications of the scintillation camera that would permit use of the 375-keV photopeak along with the 172- and 203-keV gamma energies. Charcoal traps designed for Xe-133 will require additional shielding and longer storage time when used for Xe-127. Xenon-127, however, might be used again after appropriate processing.
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PMID:A clinical comparison of Xe-127 and Xe-133 for ventilation studies. 87 43

Sixty-three patients undergoing isotope ventilation/perfusion scintigraphy for suspected pulmonary embolism were monitored using pulse oximetry. Xenon inhalation had no adverse effect on arterial oxygen saturation. Fifty-seven per cent of patients demonstrated a drop in oxygen saturation of 2-10% within 5 min of injection of macroaggregates. Small changes in arterial oxygen saturation reflect larger changes in the arteriole partial pressure of oxygen. In 10 patients, oxygen saturation dropped to 91% and below, corresponding to an arterial pO2 of less than 60 mm Hg. The effect lasted up to 30 min and is thought unlikely to be simply due to arteriolar blockade. Falls in arterial oxygen saturation cannot be correlated with any specific pulmonary pathology and appear unlikely to be of any clinical significance in most patients.
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PMID:Changes in arterial oxygen saturation during isotope perfusion scans using human macroaggregates of albumin. 175 56

Xenon-133 washout phase imaging is often used to help determine whether the etiology of a perfusion defect is embolic or due to pulmonary parenchymal pathology, such as chronic obstructive pulmonary disease. This study was designed to evaluate the pulmonary blood flow patterns associated with isolated defects on xenon washout images. Scintigraphic lung studies were reviewed until 100 cases with abnormal ventilation results were obtained. Ventilation abnormalities were compared with the corresponding perfusion scan results at the same anatomic site. Of the 208 individual lung regions with xenon abnormalities, 111 showed isolated washout defects (that is, with normal washin). Ninety-four of these 111 sites showed either normal perfusion or a small, nonsegmental corresponding perfusion defect. Three segmental perfusion defects were noted in association with isolated xenon retention. In each of these cases, however, the patient was felt actually to have pulmonary embolism. Thus, it is recommended that, for interpretation of scintigraphic images in the assessment of pulmonary embolism, lung pathology associated with isolated xenon retention not be considered a potential cause for large or segmental perfusion defects.
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PMID:Evaluation of pulmonary perfusion in lung regions showing isolated xenon-133 ventilation washout defects. 239 Aug 21

To evaluate the clinical utility of improved methods for radioaerosol inhalation imaging, we obtained preperfusion radioaerosol images in 107 patients (mean age = 62 years), who were referred for evaluation of suspected pulmonary embolism (PE). For each patient, we compared six-view aerosol images with accompanying perfusion scans and chest radiographs and with Xenon-133 (Xe-133) or Krypton-81m (Kr-81m) studies. Four observers at four different institutions independently evaluated aerosol-perfusion and gas-perfusion pairs, classifying the probability of PE as low, high, or indeterminate. The radioaerosol images were good to excellent in quality; excessive central deposition of activity was infrequent and did not interfere with image interpretation. The aerosol-perfusion studies showed 86% agreement with Xe-133 perfusion interpretations (n = 299) and 80% agreement with Kr-81m perfusion interpretations (n = 99). These rates of agreement were comparable with those of intraobserver agreement for gas-to-gas and aerosol-to-aerosol comparisons, and higher than interobserver agreement rates. In a limited number (n = 9) of angiographically documented cases, aerosol-perfusion and gas-perfusion studies provided accurate and equivalent diagnoses. The results suggest that radioaerosol inhalation studies, performed with improved nebulizers, are diagnostically equivalent to ventilation imaging as an adjunct to perfusion scintigraphy in evaluating patients with suspected PE.
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PMID:Tc-99m-DTPA aerosol and radioactive gases compared as adjuncts to perfusion scintigraphy in patients with suspected pulmonary embolism. 638 13

The major clinical use of ventilation-perfusion (V/Q) scintigraphy is for the diagnosis of pulmonary embolism (PE). Accurate diagnosis of PE is essential since effective treatment is available but involves some risk to the patient. The scintigraphic characteristics of PE are segmental perfusion defects in lung that is normally ventilated and normal on the radiograph. The inherent shortcoming of perfusion scintigraphy is its lack of specificity. Combining a ventilation study with perfusion imaging improves the diagnostic specificity of lung scintigraphy. Xenon-133 is currently the most commonly used radionuclide for routine ventilation studies; a long washout technique is more sensitive than single-breath imaging when this radionuclide is used. We obtain preperfusion xenon-133 ventilation studies with a 4-min rebreathing equilibrium phase and a long 5-min washout phase to obtain maximum information. It is imperative that V/Q studies be interpreted with a current high quality chest radiograph. Interpretation of V/Q studies for PE is perhaps best done by assigning a probability diagnosis, since rarely is absolute specificity possible. This article details the criteria we use for these probability determinations.
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PMID:Current status of ventilation-perfusion imaging. 699 97

In a prospective study 169 patients with clinically suspected leg/pelvic-vein thrombosis were tested by 131 I fibrinogen uptake-test and radionuclide venography for confirmation of this diagnosis and also by a nuclearmedical lung investigation. In all cases of an abnormal perfusion scan a supplementary ventilation scan was performed. The perfusion scan has a sensitivity for pulmonary embolism of near 1.0 but its specificity is only 0.57. An additional ventilation study (133 Xenon, 81m Krypton) improves the specificity to 0.95. A mismatch of regional ventilation and perfusion is the nuclearmedical substrate of pulmonary embolism. The diagnosis of thrombosis was confirmed in 105 of 169 cases (62%). Thrombosis was located in the lower legs in 56%, in the thigh veins in 23% and in the external iliac veins in 21%. From 105 patients with leg/pelvic-vein thrombosis 60 (57.1%) had pulmonary emboli, from 64 patients with negative tests concerning thrombosis only 3 (4.7%) (p < 0.001). Pulmonary emboli were present in 46% when thrombosis was located in the lower legs, in 67% when thigh veins and in 77% when pelvic veins were involved. The average frequency of 57% emboli found in patients with leg and pelvic vein thrombosis agrees with data from pathologic-anatomical studies. An analysis of these patients with embolism showed that 70% of them were over 70 years old, that 52% of the emboli originated from thigh and pelvis and 43% from the lower leg and that 59% had no clinical signs of embolism. 80.4% of the patients had multiple perfusion defects (up to 9) which correlated in size with the severity of the clinical symptoms and which were about equally distributed in both lungs. Larger perfusion defects occure more frequently with thromboses of the thigh and pelvis than in thromboses of the lower leg. According to the chest x-ray pulmonary emboli were suspected to only 6 of 26 patients with clinical evidence of embolism (23%).
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PMID:[Pulmonary embolism in leg and pelvic vein thrombosis. Results of a prospective study - diagnosis, frequency, nuclearmedical and clinical appearance (author's transl)]. 742 23

A 67-yr-old male status post right pneumonectomy for non-small cell lung cancer who later developed an open right bronchial stump underwent a ventilation-perfusion lung scan because of episodes of recurrent dyspnea suspected to be due to pulmonary embolism. Xenon-133 ventilation images showed both rapid entry into and later washout of activity from the air-filled portion of the right thoracic cavity. A wide-open bronchial stump, documented both at bronchoscopy and later autopsy, allowed the xenon gas to freely wash out from the thoracic cavity, resulting in a different imaging pattern than for a typical bronchopleural fistula, which is usually characterized by prolonged trapping of radioactive gas within the pleural space.
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PMID:Open bronchial stump post-pneumonectomy: findings on xenon-133 ventilation imaging. 844 Oct 40

Magnetic resonance imaging using the MR signal from hyperpolarized noble gases 129Xe and 3He may become an important new diagnostic technique. Alex Pines (adapting the hyperpolarization technique pioneered by William Happer) presented MR spectroscopy studies using hyperpolarized 129Xe. The current authors recognized that the enormous enhancement in the delectability of 129Xe, promised by hyperpolarization, would solve the daunting SNR problems impeding their attempts to use 129Xe as an in vivo MR probe, especially in order to study the action of general anesthetics. It was hoped that hyperpolarized 129Xe MRI would yield resolutions equivalent to that achievable with conventional 1H2O MRI, and that xenon's solubility in lipids would facilitate investigations of lipid-rich tissues that had as yet been hard to image. The publication of hyperpolarized 129Xe images of excised mouse lungs heralded the emergence of hyperpolarized noble-gas MRI. Using hyperpolarized 3He, researchers have obtained images of the lung gas space of guinea pigs and of humans. Lung gas images from patients with pulmonary disease have recently been reported. 3He is easier to hyperpolarize than 129Xe, and it yields a stronger MR signal, but its extremely low solubility in blood precludes its use for the imaging of tissue. Xenon, however, readily dissolves in blood, and the T1, of dissolved 129Xe is long enough for sufficient polarization to be carried by the circulation to distal tissues. Hyperpolarized 129Xe dissolved-phase tissue spectra from the thorax and head of rodents and humans have been obtained, as have chemical shift 129 Xe images from the head of rats. Lung gas 129Xe images of rodents, and more recently of humans, have been reported. Hyperpolarized 129Xe MRI (HypX-MRI) may elucidate the link between the structure of the lung and its function. The technique may also be useful in identifying ventilation-perfusion mismatch in patients with pulmonary embolism, in staging and tracking the success of therapeutic approaches in patients with chronic obstructive airway diseases, and in identifying candidates for lung transplantation or reduction surgery. The high lipophilicity of xenon may allow MR investigations of the integrity and function of excitable lipid membranes. Eventually, HypX-MRI may permit better imaging of the lipid-rich structures of the brain. Cortical brain function is one perfusion-dependent phenomena that may be explored with hyperpolarized 129Xe MR. This leads to the exciting possibility of conducting hyperpolarized 129Xe functional MRI (HypX-fMRI) studies.
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PMID:Development of hyperpolarized noble gas MRI. 1154 65


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