and determined that ultrasound could be used to scan biological material. He stated:All I wanted to know, quite simply, was whether these various masses differed in their ultrasonic echo characteristics. The results were beyond my wildest dreams and even with the primitive apparatus of those days clearly showed that a cyst produced echoes only at depth from the near and far walls, whereas a solid tumour progressively attenuated echoes at increasing depths of penetration.When he returned to the hospital, Donald's goal was to find an ultrasound machine that he could continue to experiment with. He obtained a Kelvin Hughes Mark lIb supersonic flaw detector from William Valentine Mayneord at the Royal Cancer Hospital. While Mayneord had been experimenting with the machine in an attempt to image the brain, he had been unsuccessful in his efforts; Donald hoped he could replicate and improve upon his previous success. However, he found that when using the machine it could not produce echoes from less than 8 cm from the face of the transducer, making it almost useless for obstetric diagnostics. Donald experimented with balloons and condoms filled with water to widen the gap with little success. He was assisted by John Lenihan, a professor of clinical physics, who helped him form images, but the Mark IIb was insufficient for the task and the images produced were of very poor quality. Experiments with A-mode scanner In late 1956, Tom Brown, a research engineer with Kelvin & Hughes who had previously worked on an automatic flaw detector to test industrial products, became involved. Brown has learned from a colleague who had installed a specialist bulb in a Western Infirmary theatre, that Donald was using the flaw detector. Brown immediately looked up Donald and arranged a meeting. When they met, Brown noticed that the Mark lIb was not manufactured by Kelvin & Hughes, but instead had been manufactured under contract. He also noticed that the machine had been converted from using a double probe, one to produce pulses and one to receive the pulses, to a single probe. Not wanting to insult Donald by explaining why the machine was not working correctly, Brown offered to try and source another machine from somewhere. Brown phoned Alex Rankin, the man who collaborated with Brown on the automatic flaw detector for help and who later became director of the department of Medical Ultrasonics at the company. Rankin offered to