Case Author(s): Thomas H. Vreeland, MD / J. Wallis, MD , 7/5/94 . Rating: #D1, #Q4

Diagnosis: Pulmonary Embolism

Brief history:

Progressively SOB, rule out PE


Tc-99m DTPA ventilation images (top) and Tc-99m MAA perfusion images (below).

View main image(vq) in a separate image viewer

The chest radiograph (not shown) was normal.

Full history/Diagnosis is available below

Diagnosis: Pulmonary Embolism

Full history:

This patient is a 63 year-old man with a history of diabetes mellitus, who presents with gradual shortness of breath during the 72 hours prior to admission. The patient had a widened A-a gradient on two liters of oxygen and, was subsequently anticoagulated. Ventilation-perfusion scintigraphy was performed to evaluate for pulmonary embolism.


CXR: No evidence of acute disease. No pleural effusions or infiltrate identified.

Ventilation Images: Mild heterogenity of ventilation, with a moderate defect in the region of the right major fissure.

Perfusion Images: (7/2/94) Multiple, large, segmental, wedge-shaped, perfusion defects in both lung fields, with greater involvement of the right lung than the left lung.


The large perfusion defects noted in both lung fields without corresponding radiographic or ventilatory abnormalities present a characteristic scintigraphic appearance for pulmonary embolism. The results are best described as yielding a high likelihood ratio for pulmonary embolism; the test results can then be combined with the pretest probabilty for pulmonary embolism to yield the post-test probability. The following table illustrates the combination of test results with the pre-test assessment.

----------------------Posterior probability of PE






The patient is being treated for pulmonary embolism with anticoagulation with coumadin.

View followup image(vq). Although no followup image is availble, this link shows another example of a high likelihood study for comparison.

Major teaching point(s):

(1) The bilateral lung involvement with large, segmental, unmatched perfusion defects is classic for pulmonary embolism, and typically negates the need for futher evaluation, i.e. pulmonary angiography.

(2) It is useful for followup ventilation / perfusion scintigraphy to be performed 2 to 4 weeks after the initial study to establish a new baseline, since a significant number of perfusion defects will persist for years.

Differential Diagnosis List

(1) Pulmonary Embolism

Other causes of unmatched defects (listed below) would be unlikely in this case.

(2) Centally obstructing mass

(3) Sarcoidosis

(4) Fibrosing Mediastinitis

(5) Radiation Changes

ACR Codes and Keywords:

References and General Discussion of Ventilation Perfusion Scintigraphy (Anatomic field:Lung, Mediastinum, and Pleura, Category:Organ specific)

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Case number: vq001

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