How small of a tumor can ultrasound find? i know the technology is getting better all the time, but what's the smallest size tumor modern ultrasound equipment can detect?

The : The smallest size tumor that can be detected depends on what organ is being imaged. Lesions that measure approximately 5 mm and less can be detected in the thyroid, gallbladder, testicles, ovaries, and uterus. Tumors in the kidneys, liver, and spleen are often more difficult to identify and are sometimes overlooked even when larger than 1-2 inches in diameter; for this reason ct is usually the preferred method to evaluate these organs. Ultrasound can also be used to evaluate tumors in the breast, but a prior mammogram is almost always used for comparison and to assist in locating the lesion. Depending on the size of the breast, tumors 5 to 10 mm can be detected (small lesions are usually more difficult to detect in larger breasts).

Depends on organ: Ultrasound of the thyroid can find 3 mm nodules; but, this level of sensitivity is not quite a good in the liver or breast. It depends on the organ being evaluated. Ovary, liver, pancreas, prostate, thyroid, lung and even esophagus can all be test by ultrasound.