title: Computed tomography of the human pineal gland for study of the sleep-wake rhythm: reproducibility of a semi-quantitative approach.
abstract: OBJECTIVE
  To propose a semi-quantitative computed tomography (CT) protocol for determining uncalcified pineal tissue (UCPT), and to evaluate its reproducibility in modification of studies showing that the degree of calcification is a potential marker of deficient melatonin production and may prove an instability marker of circadian rhythm.
  
  
  METHODS
  Twenty-two pineal gland autopsy specimens were scanned in a skull phantom with different slice thickness twice and the uncalcified tissue visually assessed using a four-point scale. The maximum gland density was measured and its inverse graded on a non-linear four-point scale. The sum of both scores was multiplied by the gland volume to yield the UCPT. The within-subject variance of UCPT was determined and compared between scans of different slice thickness.
  
  
  RESULTS
  The UCPT of the first measurement, in arbitrary units, was 39+/-52.5 for 1 mm slice thickness, 44+/-51.1 for 2 mm, 45+/-34.8 for 4 mm, and 84+/-58.0 for 8 mm. Significant differences of within-subject variance of UCPT were found between 1 and 4 mm, 1 and 8 mm, and 2 and 8 mm slice thicknesses (P<0.05).
  
  
  CONCLUSIONS
  A superior reproducibility of the semi-quantitative CT determination of UCPT was found using 1 and 2 mm slice thicknesses. These data support the use of thin slices of 1 and 2 mm. The benefit in reproducibility from thin slices has to be carefully weighted against their considerably higher radiation exposure.
authors.affiliation: Department of Radiology and Nuclear Medicine, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: S A
authors.initials: SA
authors.lastname: Schmitz
authors.forename: I
authors.initials: I
authors.lastname: Platzek
authors.forename: D
authors.initials: D
authors.lastname: Kunz
authors.forename: R
authors.initials: R
authors.lastname: Mahlberg
authors.forename: K-J
authors.initials: KJ
authors.lastname: Wolf
authors.forename: J O
authors.initials: JO
authors.lastname: Heidenreich
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D002114:Calcinosis / Q000000981:diagnostic imaging; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000096:biosynthesis; D008875:Middle Aged; D010870:Pineal Gland / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D008550:Melatonin