Subjects eligible for trial enrollment will be identified by the Thomas Jefferson University Urology group from their patient population of subjects under active surveillance for recurrence of a previously cryoablated RCC. A research coordinator will explain the study to the patient. The patient will be given time to consider the risks and benefits of the study and ask questions about participation. The coordinator will review the consent form with the patient and then the patient will be given the form to review. The patient, coordinator, and a study investigator will all sign the consent form. The patient will be given a copy of the signed consent form for their records.

Screening assessments will be performed prior to CEUS imaging. Trial participants will have the presence of inclusion criteria and absence of exclusion criteria verified by providing a medical history. A full demographic profile, known drug allergies or intolerances, and a review of the subject's medical/surgical history will be recorded. If the subject is a woman of childbearing age, she will have a urine pregnancy test (the results of which will be made available to the subject prior to study initiation).

All contrast injections will be supervised by a board certified physician. Resuscitation equipment and trained personnel will be in immediate proximity to the patient during each CEUS exam. The ultrasound examinations will be performed by a qualified sonographer. Ultrasound exams will take place the morning prior to the patient's 8, 12, 18, 24, or 36 month CT/MRI follow up (scheduled as part of their clinical care) or during their consultation in Jefferson's Urology clinic (for patients who have imaging performed outside Jefferson). Procedures and equipment for this trial will be used in accordance with typical clinical procedures. All trial procedures will be conducted in accordance with Good Clinical Practice. For the ultrasound examination, the patient will be asked to lie in the supine position and a catheter will be placed in a superficial vein (preferably an antecubital vein). Acoustic coupling gel will be applied to the area of interest. A state of the art ultrasound scanner with 2D and 3D curvilinear probes will be used.

A baseline ultrasound grayscale scan will be used to identify the tumor and to evaluate the following criteria: size, shape, and orientation of the lesion; echogenicity compared to surrounding tissue. Standard power Doppler of the lesion will also be performed. When possible, previous MR/CT data will be uploaded onto the scanner in order to perform image fusion for ultrasound guidance during imaging. The distribution of color signals and the overall color content of the tumor will be evaluated by comparing the pattern and amount of color to the normal surrounding tissue. Following baseline scanning, patients will receive a 1 ml intravenous injection of Optison (GE Healthcare, Princeton, NJ) in a peripheral vein followed by renal mass imaging in 2D CHI (a nonlinear contrast imaging package). Ten minutes after the 2D CEUS exam, patients will receive a second bolus injection of Optison followed by 3D CHI (using a curvilinear 3D array). All contrast injections will be supervised by a board certified physician. Resuscitation equipment and trained personnel will be immediate proximity to the patient during each contrast-enhanced ultrasound exam. Digital clips of the exams will be recorded through the contrast agent wash-in and wash-out phases for at least two minutes and stored for later use. The subject will then be monitored for adverse reactions for 30 minutes. If the patient wishes to continue participating in the study, they will be eligible for CEUS exams during their future clinically scheduled follow up exams as long as these take place within the study timeframe.

Patients will be monitored for AEs during and 30 minutes after contrast administration. All other procedures will be performed according to standard of care. No further patient monitoring is required as side effects of Optison are acute in nature and no renal toxicity has been reported.