Estimation of sacroiliac joint index in normal subjects of various age groups: comparative evaluation of four different methods of quantification in skeletal scintigraphy

BACKGROUND: To estimate and compare the sacroiliac joint(SIJ) index in skeletal scintigraphy by four different methodsof quantification employed in normal subjects of different agegroups.MATERIAL AND METHODS: The whole-body skeletal survey of100 subjects, who underwent skeletal scintigraphy three hoursafter injection of 99mTc-Methylene Diphosphonate (MDP), wereselected for this analysis. The patients having previous historyof low back pain, joint pain or any benign bone joint disorders(e.g. ankylosing spondylitis, metabolic bone disease, andosteoarthritis), documented bone lesions or tumors within thepelvis region were excluded from the study. All subjects hadnormal posterior pelvis view on visual assessment in the respectivestudy. 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) methodand applied to calculate SIJ index. SIJ indices for left and rightsacroiliac joints were calculated by dividing the count for eachjoint by the count for the sacrum. Results obtained by the fourmethods were compared statistically.RESULTS: The overall SIJ index was found to range from 1.06to 1.36 in the study population of 100 subjects encompassing allage groups. There was no significant difference in the estimatedSIJ index within each age group obtained by the four differentmethods employed in this study. The values of SIJ index wereas follows: in patients aged 2–20 years — they ranged from 1.22to 1.36; in patients aged 21–40 years — from 1.07 to 1.19; forpatients aged 41–60 years — from 1.08 to 1.19 and in patientsaged 61 years and older, SIJ values were slightly lower than inother groups and ranged from 1.06 to 1.13.CONCLUSION: Methods of selecting a region of interest haveno significant effect on the calculation of SIJ index and in healthysubjects its values range between 1.06 and 1.36, depending onthe age of the subject. The maximum value was observed inpatients aged 2–20 years and minimum values were noted inpatients aged 61 and older