The use of the contrast agent, Ablavar, will help with the diagnosis of pulmonary embolism in magnetic resonance imaging (MRI).

Specific Aim 1: To assess first-pass SNR and CNR of pulmonary MR angiography performed with 0.03 mmol/Kg of intravenous gadofosveset trisodium.

Hypothesis: Use of 0.03 mmol/Kg of gadofosveset trisodium in gradient recalled echo pulmonary MR angiography will provide a pulmonary artery SNR and CNR equal to or better than the SNR and CNR obtained using the same MR technique with 0.2 mmol/Kg of a conventional contrast agent (gadopentetate dimeglumine) and equal to or better than 0.1 mmol/Kg of intravenous gadobenate dimeglumine. Data will be compared to SNR and CNR of pulmonary MR angiogram images obtained at Washington University as part of the PIOPED III study.

Specific Aim 2: To assess SNR and CNR of breath-hold pulmonary MR imaging obtained immediately after the original first-pass breath-hold pulmonary MR angiography.

Hypothesis: SNR and CNR of pulmonary MR angiography performed immediately after first-pass breath-hold pulmonary MR angiography will be at least equal to the SNR and CNR obtained using the same MR technique with 0.2 mmol/Kg of a conventional contrast agent (gadopentetate dimeglumine) and at least equal to 0.1 mmol/Kg of intravenous gadobenate dimeglumine.

Specific Aim 3: To assess SNR and CNR of lower extremity MR venogram (MRV) performed immediately after the two pulmonary MR angiograms, described above.

Hypothesis: SNR and CNR of passive lower extremity MRV performed after pulmonary MR angiography will be equal to or better than the SNR and CNR obtained using the same passive MRV technique with 0.2 mmol/Kg of a conventional contrast agent or 0.1 mmol/Kg of gadobenate dimeglumine. Again, data will be compared to SNR and CNR of lower extremity

Inclusion Criteria:

1. Patient that have pulmonary embolism.
2. 18 yrs of age and older

Exclusion Criteria:

1. allergy to gadolinium based contrast.
2. allergy to iodated based contrast.
3. renal insufficiency (GFR < 60 mL/min?1.73m2)
4. pregnant or nursing
5. contraindication to MRI

Patients 18 years or older with pulmonary embolism