What is the most accurate way to check for pulmonary emobolism, fluid build up around heart & other chest conditions.mri, regular xray, ultrasound, etc?

Usually...: Ct chest with pulmonary embolism protocol. Us in the form of echocardiogram can also be used to detect some of those findings.

Various: For pulmonaru embolism , its a ct angiogram of the chest. For pericardial effusion its a 2d echocardiogram, usually a ct scan of the ches with IV contrast picks up most lung lesions, but not its function.