Correct!
3. V/Q scanning shows multiple small, non-segmental perfusion defects
The V/Q scan shows normal findings on the ventilation portion of the study- no delayed tracer washout is noted to suggest obstructive pulmonary disease. The kidneys are not visible, as is normally the case; visualization of the kidneys on a V/Q scan is abnormal and indicates systemic tracer embolization, suggesting a right-to-left shunt. The perfusion portion of the study is abnormal, showing numerous small, non-segmental perfusion defects, manifesting as inhomogeneous pulmonary parenchymal perfusion, but no segmental or larger perfusion defects strongly suggesting venous thromboembolism are present. Overall the pattern is consistent with an intermediate probability for thromboembolic disease.
The patient’s room air oxygen saturation was 93%, but she desaturated with ambulation to 83%. Blood gas analysis showed a PaO2 of 63 mmHg. Further evaluation with CT pulmonary angiography (Figure 4) was performed.
Figure 4. Panels A-F: Axial enhanced thoracic CT displayed in a relatively wide lung window. Lower panel: movie of axial thoracic CT scan in lung windows.
Which of the following regarding this pulmonary CTA examination is correct? (Click on the correct answer to proceed to the fourth of six panels)