Noninvasive imaging of pulmonary hypertension

Pulmonary hypertension is defined as a resting mean pulmonary arterial pressure of 25 mm Hg or more determined at right heart catheterization. The challenges for imaging in patients with suspected PH are fivefold: the imaging modality should have a high diagnostic accuracy with regard to the presence of PH; it should be able to characterize the underlying disease, and allow for quantification of its extent by measuring pulmonary hemodynamics. Finally, it should provide prognostic information, and can be used for monitoring of therapy. There have been tremendous improvements in assessment of PH by computed tomography (CT) and magnetic resonance (MR) technology in recent years. This overview tries to elucidate the potential role of each imaging modality and summarizes the most important results that have been achieved so far. In general, after implementation of multidetector technology, CT is superior to MR in assessment of parenchymal and vascular pathologies of the lung, and with electrocardiogram-triggered data acquisition allows for assessment of cardiac structures. The implementation of iodine maps as surrogate for lung perfusion will enable functional assessment of lung perfusion by CT. MR imaging is the reference standard for assessment of cardiac structure and function and allows for physiologic assessment of the pulmonary vasculature. New developments show that with MR techniques, an estimation of hemodynamic parameters such as mean pulmonary arterial pressure and pulmonary vascular resistance will be possible. Actually, CT and MR imaging should be considered as complementary investigations providing comprehensive information in patients with pulmonary hypertension.