The pituitary gland is roughly an ellipsoid.
volume in mL based on direct measurements =
= (4 / 3) * PI() * ((width in cm) / 2) * ((length in cm) / 2) * ((height in cm) / 2) *
When estimating the pituitary size from the size of the sella turcica seen on plain X-rays Di Chiro used a correction factor of 0.5112 that takes into account:
(1) X-ray magnification effect
(2) difference between roentgenographic and actual volume
(3) correction for 4 * PI() / 3 * ((0.5)^3) = 0.524
volume in mL based on size of the sella turcica =
= 0.5112 * (length in mm) * (width in mm) * (height in mm) / 1000
where:
• 1000 is for conversion from cubic mm to cubic cc (mL).
• Note that the actual dimensions are used rather than the radii, which represents factor of 8.
• If you take the previous equation, 4 * PI() / 3 / 8 = 0.5236. 0.5112 is 97.6% of this value.
• If the density of the pituitary gland is known then the weight can be estimated.
The different parts of the pituitary gland normally represent the following percentages of pituitary weight:
|
Pituitary Region
|
Percent of Total Weight
|
|
anterior lobe
|
70%
|
|
pars intermedia
|
2%
|
|
posterior lobe
|
18%
|
|
pituitary stalk
|
5%
|
|
pituitary capsule
|
5%
|
from Figure 17, page 36
