BACKGRO

UND: To estimate and compare the sacroiliac joint
(SIJ) index in skeletal scintigraphy by four different methods
of quantification employed in normal subjects of different age
groups.
MATERIAL AND METHODS: The whole-body skeletal survey of
100 subjects, who underwent skeletal scintigraphy three hours
after injection of 99mTc-Methylene Diphosphonate (MDP), were
selected for this analysis. The patients having previous history
of low back pain, joint pain or any benign bone joint disorders
(e.g. ankylosing spondylitis, metabolic bone disease, and
osteoarthritis), documented bone lesions or tumors within the
pelvis region were excluded from the study. All subjects had
normal posterior pelvis view on visual assessment in the respective
study. Sacroiliac joint index was calculated by quantitative sacroiliac scintigraphy. In each subject, four different methods of quantification were carried out: 1. irregular region of interest
(ROI) method, 2. rectangular ROI method, 3. profile peak counts
(PPC) method and 4. profile integrated counts (PIC) method
and applied to calculate SIJ index. SIJ indices for left and right
sacroiliac joints were calculated by dividing the count for each
joint by the count for the sacrum. Results obtained by the four
methods were compared statistically.

RESULTS: The overall SIJ index was found to range from 1.06
to 1.36 in the study population of 100 subjects encompassing all
age groups. There was no significant difference in the estimated
SIJ index within each age group obtained by the four different
methods employed in this study. The values of SIJ index were
as follows: in patients aged 2–20 years — they ranged from 1.22
to 1.36; in patients aged 21–40 years — from 1.07 to 1.19; for
patients aged 41–60 years — from 1.08 to 1.19 and in patients
aged 61 years and older, SIJ values were slightly lower than in
other groups and ranged from 1.06 to 1.13.

CONCLUSION: Methods of selecting a region of interest have
no significant effect on the calculation of SIJ index and in healthy
subjects its values range between 1.06 and 1.36, depending on
the age of the subject. The maximum value was observed in
patients aged 2–20 years and minimum values were noted in
patients aged 61 and older.