Participants
The pituitary glands of 100 healthy Nepalese people (49 male and 51 female, age range 7 to 86 years) were collected during the period of approximately four months from June to September 2019 at the Department of Radio-diagnosis and Medical Imaging, Universal College of Medical Sciences (UCMS), Ranigaon, Bhairahawa, Nepal. Brain MRI scans that were reported as normal findings by a radiologist were included in this study. Brain MRIs were excluded from this study if the participants were non-Nepalese citizens and were described as abnormal with (a) evidence of space-occupying lesions, e.g., brain tumour, (b) cerebral haemorrhage, (c) infarctions, (d) head injuries, (e) features of raised intracranial pressure, (f) any kind of pituitary abnormality including empty sella and (g) any previous intracranial surgeries.
MRI Scan
The image data were collected in Siemens Magnetom Essenza 1.5 Tesla clinical MRI imager (Erlangen, Germany) using a bird-cage coil following the brain scan protocol. The patient was placed in the headfirst supine position, and the laser beam localizer was centred over the glabella. The cushions were used for head immobilization. The localizer, T2 axial turbo spin-echo (TSE), T1 axial spin-echo (SE), T2 axial fluid-attenuated inversion recovery (FLAIR), T2 coronal TSE and T1 sagittal SE sequences were acquired. The image data were acquired with the following scan parameters: Time of Repetition (TR), 500 ms and Time of Echo (TE), 8.9 ms for T1-weighted sagittal scan, TR, 3800 ms and TE, 105 ms for T2-weighted coronal scan, slice thickness (ST), 5 mm, and field of view (FOV), 250-270 x 250-270 mm.
Data Analysis
Age was categorized into 7 groups, viz, below 20, 20 – 30, 30 – 40, 40 – 50, 50 – 60, 60 – 70 and 70 above years. The height, width and depth of the pituitary gland were measured, and the volume of the pituitary gland was calculated. The height and depth were measured in T1-weighted mid-sagittal images in which the cerebral aqueduct was distinct. The width was measured in T2-weighted mid-coronal images where the pituitary stalk was clearly visible as shown in Figure 1. The pituitary volume (mm3) was obtained by multiplying the height (H), depth (D), and width (W) by 0.52. The factor 0.52 was derived from the sphere volume equation coefficient and cubic volume calculation (4/3π) (r3)/ (2r) 3 = 3.1416/6 = 0.52 The term 0.52 is a constant and is a correction factor for the variation in shape that may occur in the normal pituitary gland. Measures of central tendency and statistical tests were analyzed in Statistical Package for the Social Sciences (SPSS), version 27, (IBM, Armonk, New York, United States). The data were assessed for normal distribution by using Shapiro-Wilk normality test, scatter plot and histogram plot. The width and volume data of the pituitary gland followed a normal distribution and were analyzed by independent samples T-test and one-way analysis of variance (ANOVA) test with Bonferroni’s correction applied post hoc test, whereas the height and depth data did not follow a normal distribution and were analyzed by using Mann-Whitney U-test and Kruskal-Wallis H-test with Bonferroni’s post hoc test.
Ethical approval and consent to participate
The written ethical approval was obtained from the institutional review board of Universal College of Medical Sciences, Ranigaon, Bhairahawa, Nepal. The approval number of this study is UCMS/IRC/225/19. The consent to participate was obtained from all the participants before performing an MRI scan. The written informed consent was obtained from a parent or a guardian for participants under 16 years of age.