Effects of energy-matched pulsed and continuous ultrasound on tumor growth in mice.
OBJECTIVE
A diagnosis of cancer is a contraindication for the use of therapeutic ultrasound (US). Continuous US applied to murine tumors has resulted in larger and heavier tumors compared with controls. We compared tumor growth using low-power continuous US and energy-matched pulsed US.


METHODS
Female C57BL/6 mice (N = 174) were used.


METHODS
Animals received subcutaneous injections of methylcholanthrene tumor cells. The mice were randomly divided into three groups: 60 mice that received low-power continuous US for 5 minutes at 0.75 W/cm2 (LC US group), 63 mice that received pulsed US for 12.5 minutes at 1.5 W/cm2 (pulsed US group), and 51 mice that served as a control group. The LC and pulsed US groups received equal US energy. Both experimental groups received 10 treatments of 3-MHz US, which was applied directly over the tumor. The control group received identical handling but no US. After treatment, the tumors were excised, weighed, and measured. 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 mm3 for the LC US group, 0.560 g and 525 mm3 for the pulsed US group, and 0.516 g and 406 mm3 for the control group.


CONCLUSIONS
Reducing total US energy will result in less growth of murine tumors. When infusing equal energy, continuous and pulsed US will produce similar effects on tumor growth.
Sicard-Rosenbaum
L
L
Physical Therapy Section, Rehabilitation Medicine Department, National Institutes of Health, Bethesda, Md., USA.
Danoff
J V
JV
Guthrie
J A
JA
Eckhaus
M A
MA
D000704:Analysis of Variance; D000818:Animals; D005069:Evaluation Studies as Topic; D005260:Female; D008748:Methylcholanthrene; D051379:Mice; D008810:Mice, Inbred C57BL; D010865:Pilot Projects; D011897:Random Allocation; D012208:Rhabdomyosarcoma / Q000473:pathology* / Q000628:therapy*; D013010:Sonication; D014464:Ultrasonic Therapy / Q000009:adverse effects / Q000379:methods*
D008748:Methylcholanthrene