The purpose of this study is to prospectively analyze the value of 3D ultrasound perfusion imaging for treatment planning, the prediction of therapy success, and to monitor the treatment response in patients with a primary or metastatic liver tumor undergoing radiation treatment.

Primary Objective:

The primary objectives of this prospective pilot study is to:

1. determine the feasibility and reproducibility of 3D contrast enhanced ultrasound imaging in liver cancer patients undergoing Stereotactic Ablative Radiotherapy and
2. evaluate whether there are treatment induced early changes in imaging metrics derived from 3D contrast enhanced ultrasound. This study will provide valuable insight as to the potential of baseline and/or early post-treatment 3D ultrasound perfusion characteristics (measurements of blood-flow) of primary and metastatic liver tumors to predict tumor response to Stereotactic Ablative Radiotherapy. The investigators' underlying goal is to assess whether early perfusion changes at 1-7 days after SABR initiation can be used as a non-invasive early biomarker for treatment response assessment.

Secondary Objectives:

Evaluate the feasibility of contrast-enhanced ultrasound-to-CT fusion by assisting three-dimensional (3D) perfusion ultrasound (US) imaging with optical and electromagnetic tracking of the ultrasound probe on patients with liver cancer that will undergo CT for treatment planning and/or response evaluation.

Inclusion Criteria:

• Ability to understand and willingness to sign the written informed consent document
• Patient with primary liver tumor or metastasis scheduled for Stereotactic Ablative Radiotherapy (SABR)
• Patient is at least 18 years of age. No gender/race-ethnic restrictions.
• Performance status (ECOG) between 0-3
• History and Physical done within 4 weeks of enrollment.

Exclusion Criteria:

• Patient has previously been enrolled in and completed this study.
• Known right to left cardiac shunt, bidirectional or transient.
• Patient has any medical condition or other circumstances which would significantly decrease the chances of obtaining reliable data, achieving study objectives, or completing the study and/or post-dose follow-up examinations.
• History of hypersensitivity to the contrast agent perflutren
• History of pulmonary hypertension
• Patients who are pregnant or are trying to become pregnant

Up to 4 months