Pioneers; Hounsfield & Cormack

Godfrey Hounsfield (1919-2004) was a British electrical engineer who developed computed tomography (CT). 

In 1949, Hounsfield began working at EMI, Ltd where he researched guided weapon systems and radar.  At EMI, he became interested in computers and in 1958, he helped in the design of the first computer system in Great Britain. Shortly afterwork he started work on CT scanner.   

Hounsfield came up with the idea that one could determine what was inside a box by taking x-ray readings at multiple angles around an object.  He then built a computer that could take input from x-rays at various angles to create an image of the object in slices.  Applying this idea to the medical field led him to what is known today as computed tomography. The scale of units he used (HD), running from -1000 HD for air, 0 HD for water, and +1000 HD for cortical bone are the quantitive measures used in obtaining, depicting and evaluating a CT scan.

At that time, Hounsfield was not aware of the work and the two papers Allan Cormack (1924-1988) had published in 1956 on the theoretical basis of such a device when he worked at the University of Cape Town and Groote Schuur Hospital.

Hounsfield built a prototype head CT scanner and tested it first on a cadaver's brain and soon after on a cow's brain and finally on himself.  On October 1st 1971, CT scanning was introduced in medical practice with a brain scan performed on a patient and in 1975 Hounsfield built a whole body scanner. 

In 1979, Hounsfield and Cormack received the Nobel Prize in Physiology and Medicine.  Both received numerous awards in addition to the Nobel and Hounsfield was also knighted in 1981.

The above post is dedicated to Dr John Andreou and Professor A Gouliamos  prominent Greek radiologists whose expertise in computed tomography contributed in establishing it as a pre-eminent diagnostic method in Greece.  in addition to being a good colleagues I also thank them for being good friends to me for the past 50 years.

Low Radiation Dose CT Leads to Inferior Diagnoses

Jensen et al reported in Radiology that CT evaluation of colorectal liver metastases was not as accurate after reducing the radiation exposure by more than 50 percent. 

Their study included 52 patients with biopsy-proven colorectal cancer liver metastases and few benign lesions as well.  Each patient underwent two CT scans-a standard radiation dose (SD) contrast CT and a reduced radiation dose (RD) CT scan- during the same breast hold.

Reduced dose CT resulted in a mean dose reduction of 54% compared with standard dose. Of the 260 lesions, 233 were metastatic and 27 benign, 212 were detected with RD CT, whereas 252 were detected with SD CT.   Mean qualitative scores ranked SD images as higher quality versus RD series images.

The authors concluded that CT evaluation of colorectal liver metastases is compromised with reduced radiation dose, and the use of iterative reconstructions could not maintain observer performance.