Tuesday, March 6, 2012

Pencil on CT

The CT appearance of the typical pencil containing graphite and wood is shown above in cross section in a patient with a penetrating injury. The attenuation of wood is negative (~-400 HU in this case), seen best on the lung windows. The graphite has much higher attenuation (~500 in this case), but lower than that of cortical bone.

The paint seems to have higher attenuation than the wood. Two old papers from 1971 raise concerns about the lead content of paints used on pencils, but I can't find any recent data on the contents of the paint.


  • Pichirallo J. Lead poisoning: risks for pencil chewers? Science. 1971 Aug 6;173(3996):509-10.
  • Tenenholz T, Baxter AB, McKhann GM. Orbital assault with a pencil: evaluating vascular injury. AJR Am J Roentgenol. 1999 Jul;173(1):144.
  • Schaplowsky AF. Lead in paint on pencils. HSMHA Health Rep. 1971 Nov;86(11):961-2.

1 comment:

  1. Hello! Please look at the information of the Australian Customs Service about restrictions on importing pencils with several heavy metals in the paint/lacquer (http://www.customs.gov.au/webdata/resources/files/FS_PencilPaintbrushes.pdf)! So there seems to be some factories in the world producing pencils with toxic ingredients!


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