Head cheese sign (lungs)
Citation, DOI & article data
The head cheese sign or three-density pattern refers to a juxtaposition of regions with three (or sometimes more) different densities/regions of different attenuation within the lungs:
- ground-glass opacities (high attenuation)
- mosaic attenuation pattern (low attenuation)
- normal lung tissue (normal attenuation)
A mixed infiltrative (ground-glass opacity) and obstructive (mosaic attenuation) disease process can give rise to the head cheese sign. Less frequently, the superposition of a separate infiltrative and obstructive process causes this pattern. As the mosaic attenuation pattern is caused by airway narrowing/air trapping, these low attenuation areas may only be apparent on expiratory scans.
The head cheese sign is considered to be highly specific for hypersensitivity pneumonitis, although it can also be seen in other mixed infiltrative and obstructive processes (e.g. sarcoidosis and atypical infections associated with bronchiolitis (e.g. mycoplasma pneumonia) 3.
History and etymology
Head cheese, believe it or not, is not cheese and is often not made of the head. It is, in fact, a type of terrine, with bits of meat scavenged from various parts of various animals (including the head) usually from a calf or pig. The appearance of the cut surface of this dubious delicacy has been likened to the previously described pattern.
The three-density pattern has been proposed as an alternative name for this sign as familiarity with head cheese is regionally limited 5.
- 1. High-resolution CT of the lung. W. Richard Webb, Nestor L. Muller, David P. Naidich. Philadelphia : Lippincott Williams & Wilkins, c2001. ISBN:0781722780 (find it at amazon.com)
- 2. Webb WR. Thin-section CT of the secondary pulmonary lobule: anatomy and the image-the 2004 Fleischner lecture. Radiology. 2006;239 (2): 322-38. doi:10.1148/radiol.2392041968 - Pubmed citation
- 3. Chong BJ, Kanne JP, Chung JH. Headcheese sign. (2014) Journal of thoracic imaging. 29 (1): W13. doi:10.1097/RTI.0000000000000067 - Pubmed
- 4. Parker MS, Chasen MH, Paul N. Radiologic signs in thoracic imaging: case-based review and self-assessment module. (2009) AJR. American journal of roentgenology. 192 (3 Suppl): S34-48. doi:10.2214/AJR.07.7081 - Pubmed
- 5. Ganesh Raghu, Martine Remy-Jardin, Christopher J. Ryerson, Jeffrey L. Myers, Michael Kreuter, Martina Vasakova, Elena Bargagli, Jonathan H. Chung, Bridget F. Collins, Elisabeth Bendstrup, Hassan A. Chami, Abigail T. Chua, Tamera J. Corte, Jean-Charles Dalphin, Sonye K. Danoff, Javier Diaz-Mendoza, Abhijit Duggal, Ryoko Egashira, Thomas Ewing, Mridu Gulati, Yoshikazu Inoue, Alex R. Jenkins, Kerri A. Johannson, Takeshi Johkoh, Maximiliano Tamae-Kakazu, Masanori Kitaichi, Shandra L. Knight, Dirk Koschel, David J. Lederer, Yolanda Mageto, Lisa A. Maier, Carlos Matiz, Ferran Morell, Andrew G. Nicholson, Setu Patolia, Carlos A. Pereira, Elisabetta A. Renzoni, Margaret L. Salisbury, Moises Selman, Simon L. F. Walsh, Wim A. Wuyts, Kevin C. Wilson. Diagnosis of Hypersensitivity Pneumonitis in Adults. An Official ATS/JRS/ALAT Clinical Practice Guideline. (2020) American Journal of Respiratory and Critical Care Medicine. doi:10.1164/rccm.202005-2032ST