Major progress achieved in diagnostic and therapeutic strategies has substantially improved the short-term prognosis of patients with pulmonary embolism (PE). These improvements have led to a shift from an acute to a chronic condition of venous thromboembolism, justifying the recent development of Chronic Thrombo-embolic Disease (CTED). In most of the situations, it is due to a residual pulmonary vascular obstruction (RPVO) which can be assessed by pulmonary scintigraphy.

Planar ventilation/perfusion (V/Q) scintigraphy is the gold standard, but for several months, V/Q single photon emission computed tomography (SPECT) is recommended in the guidelines.

The aim of this study is to evaluate the performances of various SPECT protocols to quantified RPVO and compared to planar scintigraphy to evaluate the RPVO.

Inclusion Criteria:

• Patient addressed to nuclear medicine department of Saint-Etienne public hospital for V/Q pulmonary SPECT-CT assess to rule out perfusion obstruction, admitted for a suspicion of pulmonary hypertension (PH), or a persistent dyspnea after PE
• Patient affiliated ou beneficiary of social security.

Exclusion Criteria:

• Pregnant patient.
• Patient addressed to nuclear medicine department for acute pulmonary embolism.
• Impossibility of the entire protocol acquisitions realization.

Patients with V/Q pulmonary SPECT-CT assess to rule out perfusion obstruction, patients admitted for a suspicion of PH, or a persistent dyspnea after PE