T₂ relaxation mapping MRI of healthy and inflamed gingival tissue

To investigate the use and reproducibility of MRI transverse relaxation time (T₂) mapping in healthy and inflamed gingivae.

21 subjects were recruited into 2 groups: those without evidence of gingivitis ("healthy"; n = 11, age 24.0 ± 3.66 years) by visual assessment and those with moderate to severe gingivitis ("gingivitis"; n = 10, age 28.9 ± 6.03 years) exhibited across the second mandibular premolar and first mandibular molar buccal gingivae. Subjects were imaged by MRI twice in a single day. Three T₂ weighted turbo spin-echo volumes with 0.25 × 0.25 × 0.8-mm³ resolution were acquired at echo times of 16, 32 and 48 ms for T₂ decay fitting. Image analysis was fully blinded; the two imaging sessions were not identifiable as coming from the same subject. Each imaging session had independent regions of interest drawn on the first echo image and applied to the calculated T₂ decay maps.

The coefficient of variation was low and similar in healthy and gingivitis populations: 6.10 and 5.25% populations, respectively, with 5.65% populations across both groups. Bland-Altman analysis revealed no bias (mean -2.93%; 95% confidence intervals -22.20 to 16.34%) between sessions. The intersession agreement was good (r = 0.744, ρ = 0.568, intraclass correlation coefficient = 0.68). T₂ mapping did not differentiate healthy from gingivitis groups. The mean T₂ value in the healthy group (63.7 ms) was similar to that of the gingivitis group (65.23 ms) (p = 0.30).

Mapping of the T₂ decay in the gingivae was a repeatable process; however, T₂ value alone did not differentiate those with clinical examination-determined gingivitis from those without signs of gingivitis.