Detection of neovascular signals in a 3 day walker 256 rat carcinoma by CW doppler ultrasound

An animal model was used to study tumor blood flow by the Doppler CW technique. The objective was to determine when neovascularity could be detected as a function of tumor size and time since transplantation. A Walker 256 carcinosarcoma tumor was innoculated into the flank of 17 Sprague-Dawley rats. Doppler examinations, using a 9 MHz CW probe, were performed daily from day 0 to day 7. The contralateral flank was used as a control. No signals were detected from the control side nor from the innoculated side until day 3. By day 3, Doppler signals could be easily detected in all tumor implants with a minimum weight of only 50 mg. These signals showed a mean systolic frequency shift of 3.3 ± 0.47 kHz at 3 days and 3.46 ± 0.58 kHz at 7 days. The diastolic Doppler shifted frequency was 1.78 ± 0.31 kHz at 3 days and 1.88 ± 0.23 kHz at 7 days giving a Pourcelot index of 0.47 ± 0.1 at 3 days and 0.46 ± 0.09 at day 7. These figures indicate the presence of low impedance vessels with high velocity flow such as has been reported in many human tumors. The vascular morphology was further evaluated by digital angiography which demonstrated coincidence between the site of the high velocity Doppler signals and the presence of arteriovenous anastomoses manifested by simultaneous arterial and venous filling. Further infusion techniques using India ink or Microfil® showed the chaotic arrangement of tumor vessels located around the growing edge of the tumor implant. The development of such vascularity is a well-recognized prerequisite for tumor growth and invasion. The ability to detect such development in tumors as small as 50 mg encourages further evaluation of Doppler techniques for the diagnosis and treatment of tumors in both animal models and humans.