St. Jude Children's Research Hospital is studying ways to make ultrasound images clearer - to be able to see blood vessels, body structures, and tumors better. Ultrasound uses sound waves to create pictures, allowing doctors and other medical professionals to "see" inside the body.

Researchers are studying a contrast agent (like a dye) called Optison™. St. Jude Children's Research Hospital researchers want to learn the best and safest dose of this ultrasound "dye."

Inclusion Criteria:

• Age: 2-20 years old
• Subject has a known or suspected solid soft tissue tumor in the abdomen or pelvis.
• Subject is scheduled for other imaging or is already scheduled for an ultrasound or has already had adequate imaging performed at an outside institution.
• Subject is able to lie still for the exam without sedation.

Exclusion Criteria:

• Known or suspected hypersensitivity to albumin, blood or blood products.
• History of open heart surgery, cyanotic congenital heart disease or an axygen saturation of less than 96% as determined by pulse oximetry.