 Doppler signals can be recorded from the lung parenchyma by means of a pulsed Doppler ultrasound system incorporating a special signal processing package- the Transthoracic Parametric Doppler TPD Echosense Ltd., Haifa, Israel. Systemic sclerosis patients often develop pulmonary vascular disease leading to pulmonary hypertension. The TPD system may provide important insight into pulmonary blood vessels characteristics by the LDS Lung Doppler Signals signals that are related to pulmonary hypertension. The TPD performance in detecting PAH in SSc patients will be assessed in the study. 