Ventilation-Perfusion Lung Scanning for Pulmonary Emboli

Abstract

SummaryThe conventional method of lung scanning detects defects of pulmonary artery perfusion. False positive results occur because regions of hypoventilation, such as are present in obstructive airways disease, also cause defects of perfusion. The converse is not true, however, as defects of perfusion continue to be ventilated. Thus in pulmonary embolism ventilation-perfusion discrepancy (normal ventilation and impaired perfusion) occursWe have assessed the clinical value of this discrepancy. Out of 18 patients with ventilation-perfusion discrepancy 14 had a final diagnosis of pulmonary emboli, whereas in none of the 34 patients without the discrepancy was this final diagnosis made. We conclude that combined ventilationperfusion lung scanning distinguishes pulmonary emboli from other lung conditions such as asthma and bronchitis which cause impaired pulmonary perfusion. The false positive rate was only 4% overall and 7-7% in patients with perfusion defects. IntroductionLung perfusion scanning is of value in the diagnosis of pulmonary embolism and is a simple and safe screening proced-

The value of lung scintigraphy in the diagnosis of pulmonary embolism

“…Totally absent perfusion of a complete lung is a rare finding, and one should be especially aware of congenital vascular abnormalities Pulmonary veno-occlusive disease [39] Fibrotic sarcoid [42] Perfusion defect with normal ventilation Acute pulmonary embolism [6-8, 19, 33] Old pulmonary thromboembolism [44,45] Atelectasis [48] Metastatic lung disease [49] (Microscopic) tumour embolism [51,52] Post radiotherapy [54] Haemangioendotheliomatosis [56] Traumatic pulmonary artery pseudoaneurysm [58] Air embolism [61] Idiopathic pulmonary fibrosis [63,64] Oesophageal hiatus hernia [65] Positive end expiratory pressure ventilation [67] Diaphragm paralysis [69] Mitral valve disease [71] Dogworm infestation [33] Congenital vascular abnormalities [36][37][38] Tumours in the hilar region [40,41] Histoplasmosis [43] Emphysema [46,47] Pneumonia [33,42] Sarcoidosis [49] Lymphangitis carcinomatosis [50] Intravenous drug abuse [53] Pulmonary artery sarcoma [49,55] Systemic arterial supply [57] Pulmonary contusion [59,60] Takayasu's arterities [49,62] Histoplasmosis [43] Intrathoracic stomach …”

“…Pulmonary veno-occlusive disease may also mimic pulmonary thromboembolism, but the ante-mortem diagnosis is difficult [39]. Other rare causes of unilateral perfusion-ventilation mismatch are fibrotic sarcoid and histoplasmosis [42,43].…”

Comparison of Ventilation/Perfusion Lung-Imaging and Dead-Space Measurements in Airway Disease

“…During the test, ventilation images were obtained while the patient inhaled 81mKr in air through a face mask. Radio-krypton was obtained from the MRC Cyclotron at the Hammersmith Hospital, the parent nuclide being 81Rb from which the radio-krypton emerged continuously as its radioactive breakdown product (Williams, Lyall, Vernon & Croft, 1974;Fazio & Jones, 1975;Goris, Daspit, Walter, McRae & Lamb, 1977). Ventilation and perfusion pictures were taken sequentially, the use of different energy windows on the gamma-camera allowing the technetium to be excluded when images were being made from the inhaled radio-krypton.…”

Accumulation of ^99mTc-Tetracycline in Lung Infarction Area

“…It may even be helpful in di agnosing pulmonary embolism combined with pulmonary hemorrhage without infarc tion, which may occur in some cases [2]. It is of special interest to differentiate pulmon ary embolism and/or pulmonary hemor rhage from pleuropneumonia, because it is often difficult to establish exactly the right diagnosis by clinical means [10]. In another preliminary study, we saw that accumula tion of labeled tetracycline cannot be detect ed either in pneumonic infiltration or in lung neoplasms in man.…”