L. Sicardrosenbaum et al., EFFECTS OF ENERGY-MATCHED PULSED AND CONTINUOUS ULTRASOUND ON TUMOR-GROWTH IN MICE, Physical therapy, 78(3), 1998, pp. 271-277
Background and Purpose. A diagnosis of cancer is a contraindication fo
r the use of therapeutic ultrasound (US). Continuous US applied to mur
ine tumors has resulted in larger and heavier tumors compared with con
trols. We compared tumor growth using low-power continuous US and ener
gy-matched pulsed US. Subjects. Female C57BL/6 mice (N=174) were used.
Methods. Animals received subcutaneous injections of methylcholanthre
ne tumor cells. The mice were randomly divided into three groups: 60 m
ice that received low-power continuous US for 5 minutes at 0.75 W/cm(2
) (LC US group), 63 mice that received pulsed US for 12.5 minutes at 1
.5 W/cm(2) (pulsed US group), and 51 mice that served as a control gro
up. The LC and pulsed US groups received equal US energy. Both experim
ental groups received 10 treatments of 3-MHz US, which was applied dir
ectly over the tumor. The control group received identical handling bu
t no US. After treatment, the tumors were excised, weighed, and measur
ed. A one-way analysis of variance, followed by Newman-Keuls Post hoc
testing, was used to analyze the data. Results. Mean tumor weights (in
grams) and volumes (in cubic millimeters) were 0.563 g and 564 mm(3)
for the LC US group, 0.560 g and 525 mm(3) for the pulsed US group, an
d 0.516 g and 406 mm(3) for the control group. Conclusion and Discussi
on. Reducing total US energy will result in less growth of murine tumo
rs. When infusing equal energy, continuous and pulsed US will produce
similar effects on tumor growth.