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British Journal of Radiology (2004) 77, 803
© 2004 British Institute of Radiology
doi: 10.1259/bjr/44426072
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Correspondence

Baked beans on CT

The Editor—Sir,

I noted with interest the Case of the Month in February [1], demonstrating multiple high density filling defects in the stomach, which it transpired were baked beans. I was surprised that they could find no reference to this in the literature (though when I looked I was equally unsuccessful). This appearance was brought to my attention by senior colleagues when I was a research fellow in CT some years ago. The explanation, I suspect, is largely not the presence of high atomic number materials (the authors mention iodine, iron sulphate, other trace elements such as magnesium, manganese and molybdenum amongst others). Unless high atomic number elements are present in high concentrations, it is the electron density of a material that most markedly affects its CT number, this is closely related to the physical density of the material. Baked beans are dense! They sink in the tomato sauce. It is for the same reason that a fresh blood clot is of high CT number – not the iron content but the physical density of (haemoglobin) blood cells compacted together with serum excluded.

Experiments to further investigate this could include measurement of the physical density of baked beans and dual energy quantitative computed tomography of baked beans (this can separate high and low atomic number effects from electron density effects). Ash weight measurements of (ex-) baked beans are feasible but mass spectroscopy might be taking this a bit far.

Changes in physical density of materials are reflected in changes of CT number, with ice, for example, having a CT number of around –80, whilst lard (and body fat) becomes denser as its temperature falls – beware CT number in frozen specimens [2].

Yours etc.,

R Whitehouse

Manchester Royal Infirmary, Oxford Road, Manchester, M13 9WL

Received for publication March 24, 2004. Accepted for publication June 10, 2004.

References

  1. Offiah C, Kumar EN. An unusual cause of intraluminal gastric radio-opacities. Br J Radiol 2004;77:171–2.[Free Full Text]
  2. Whitehouse RW, Economou G, Adams JE. Influence of temperature on QCT: implications for mineral densitometry. J Comput Assist Tomogr 1993;17:945–51.[Medline]

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Author's reply
C Offiah
BJR 2004 77: 803. [Full Text]  




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