title: Sliding thin slab, minimum intensity projection of the lung in asymptomatic subjects: lower limits of lung attenuation, without airways.
abstract: OBJECTIVE
  A sliding thin slab, minimum intensity projection (STS-MinIP) is considered to be useful for detecting diseases that decrease lung attenuation. For evaluating these diseases, it would be useful to ascertain the lower limits of normal lung attenuation, allowing a division between normal and subnormal attenuation. However, normal lung attenuation may vary depending on respiratory status, anatomical position, and patient background factors. Our aim was to determine whether the lower limits of lung attenuation, without airways, in asymptomatic subjects using STS-MinIP varies under different conditions.
  
  
  METHODS
  The study subjects were 43 volunteers without pulmonary symptoms. STS-MinIP was performed at full inspiration and full expiration at three levels of the lung. The lower limits of lung attenuation were compared among the three lung levels and between full inspiration and full expiration, the sexes, age groups, smokers and nonsmokers, and the right and left lungs.
  
  
  RESULTS
  The lower limits of lung attenuation had significantly different Hounsfield unit values among lung levels, between the sexes at full inspiration, and between age groups at full expiration.
  
  
  CONCLUSIONS
  This study shows that the lower limits of lung attenuation are influenced by lung fields, sex, and, on expiration, age.
authors.affiliation: Department of Radiology, Ohme Municipal General Hospital, 4-16-5 Higashi-ohme, Ohme, Tokyo 98-0042, Japan.
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Ishihara
authors.forename: Shiro
authors.initials: S
authors.lastname: Satoh
authors.forename: Shinichi
authors.initials: S
authors.lastname: Ohdama
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Shibuya
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012143:Respiratory Physiological Phenomena; D012737:Sex Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*