<qa>  What is the purpose of the Shockwave Coronary Rx Lithoplasty System?Prospective, multi-center, single arm study designed to evaluate the safety and performance of the Shockwave Coronary Rx Lithoplasty System to treat calcified lesions in the coronary arteries for the purpose of enhancing the placement of stents and reducing the ultimate residual stenosis. Patients will be followed through discharge and at 30 and 180 days. 