Synergism between ultrasound and X rays in tumour therapy

Although direct use of ultrasound in tumour therapy, as advocated by Hovarth (1944; 1946) is now considered to be of very limited value (Lehmann and Krusen, 1955; Herrick, 1953), it has been reported by Woeber (1959; 1965) that the use of ultrasound in conjunction with X-ray therapy can increase the effectiveness of the latter. In his study, Woeber reported complete regression of Walker carcinomas in rats following 350 rads of X rays accompanied by ultrasonic irradiation at 1 W cm−2. Equivalent results were reported following 600 rads of X rays alone, implying that the ultrasonic irradiation increased the X-ray effectiveness by a factor of 600/350, or about 1·7. Despite the obvious interest of this much-quoted result, both in practical terms and in its bearing on the theoretical understanding of the mechanisms of biological action of both ionising and ultrasonic radiation, little attempt appears to have been made to follow it up. Woeber's results suggested that synergism between X irradiation and ultrasou...