Tc-HYNIC-Annexin V also fails in detecting enhanced apoptosis when vasculature has regressed. (A) Nuclear measurements using the tracer 99 mTc-HYNIC-Annexin V reveal almost equal tumor-to-muscle ratios normalized to tissue weight in control and therapy tumors (control, n = 5; therapy, n = 6), P = 0.63. (B) In contrast to nuclear measurements, quantification of the TUNEL-positive area fraction in sections of treated tumors demonstrates a highly significant increase in apoptosis in the treated tumors, **P < 0.001. (C) Contrast-enhanced ultrasound demonstrates again a significantly higher acoustic intensity per tumor area in control versus treated tumors (*P < 0.01). (D) Quantification of the mean vessel density in tumor sections demonstrates a highly significant decrease in vessel density in the therapy group, **P < 0.001.