title: Quantitative assessment of the superior sagittal sinus on unenhanced computed tomography.
abstract: OBJECTIVE
  To determine the relationship between hemoglobin levels and attenuation measurements of the superior sagittal sinus (SSS) on unenhanced computed tomography (UECT). Secondly, to determine if SSS attenuation values are normally distributed such that measurements below and above certain thresholds are suggestive of pathology, such as anemia or acute venous thrombosis respectively.
  
  
  METHODS
  Institutional review board approval was obtained for retrospective review of adult patients having both an UECT head examination and a complete blood count within 24 h of the scan. A cohort of 151 consecutive patients formed the study sample (76 males and 75 females, 17-91 years of age with a mean of 61). The dorsal aspect of the SSS was divided into upper, middle and lower segments. Using freehand and circle region of interest (ROI) techniques, a total of six attenuation measurements were obtained from each patient. Next, statistical analyses were preformed to assess the correlation between Hgb levels and attenuation values, and distribution curves were plotted to assess the normal range of SSS attenuation measurements.
  
  
  RESULTS
  There is a moderate, yet statistically significant (p<0.001), correlation between Hgb levels and attenuation values in upper, middle and lower segments of the SSS (r=0.487, 0.497 and 0.533 respectively). Based on the calculated mean, median and mode, the attenuation values are normally distributed. When using the freehand ROI technique, the mean value is 50 Hounsfield Units (HU) with a standard deviation (SD) of 7.5. Attenuation values less than 2 SDs (35 HU) are highly suggestive of anemia (specificity and PPV=100%).
  
  
  CONCLUSIONS
  There is a moderate, yet statistically significant, correlation between Hgb levels and attenuation of the SSS on UECT. Furthermore, attenuation measurements of the SSS are normally distributed with a mean of 50 HU and a SD of 7.5. Therefore, quantitative assessment of the SSS may prove useful in the clinical practice of a radiologist; namely, in the diagnosis of anemia and acute venous thrombosis.
authors.affiliation: University of Toronto, Department of Medical Imaging, Ontario Canada M5S3E2. randy.fanous@gmail.com
authors.forename: Randy
authors.initials: R
authors.lastname: Fanous
authors.forename: Andrew
authors.initials: A
authors.lastname: Leung
authors.forename: Stephen
authors.initials: S
authors.lastname: Karlik
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002533:Cerebral Angiography / Q000379:methods*; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010690:Phlebography / Q000379:methods*; D011856:Radiographic Image Enhancement; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D054063:Superior Sagittal Sinus / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D056824:Upper Extremity Deep Vein Thrombosis / Q000000981:diagnostic imaging*; D055815:Young Adult
chemical_list: D003287:Contrast Media