Which of the following is NOT a basic diagnostic test for a Pulmonary Embolism?

A pulmonary embolism (PE) is a blockage in one of the pulmonary arteries in the lungs, usually caused by blood clots that travel to the lungs from the legs or other parts of the body (deep vein thrombosis). The basic diagnostic tests typically used for PE are designed to assess the likelihood of an embolism and to visualize the blockage.

A chest X-ray is a basic diagnostic imaging test; however, it may show normal results in many patients with PE. It is mainly used to rule out other causes of symptoms like chest pain or breathing difficulty.

Arterial blood gas analysis provides information about the patient's oxygenation, carbon dioxide levels, and blood pH, which can indicate compromise in gas exchange due to a potential pulmonary embolism.

The Vd/Vt ratio, or the dead space to tidal volume ratio, is a clinical measurement used to assess ventilation effectiveness in relation to perfusion. An increased Vd/Vt ratio can suggest a problem such as PE, as it indicates that a portion of the lung is ventilated but not perfused.

A pulmonary angiogram, while a definitive test for diagnosing PE, is more specialized and invasive compared to the other diagnostic tests mentioned. It involves the injection of contrast material into the pulmonary arteries