MR T1 and T2 relaxations in cysts and abscesses measured by 1.5 T MRI

Objectives: The main objective of this study was to make a comparison between the relaxation rates in jaw cysts and abscesses. Such a comparison should provide quantitative information for MR image analysis. Methods: A phantom containing 20 odontogenic jaw cysts and 11 jaw abscesses was imaged with 1.5 T MR. T-1 measurements were performed by using a mixed sequence of inversion recovery and spin echo, while T-2 measurements were carried out by the Carr-Purcell Meiboom-Gill (CPMG) sequence. Cystic fluids and abscesses were compared statistically. Results: In cysts and abscesses, respectively, the mean 1/T-1 was 0.9355 s(-1) and 0.8245 s(-1) and the mean 1/T-2 was 2.4575 s(-1) and 4.7073 s(-1). The 1/T-2 in cysts was very highly significantly different from that in abscesses (p = 0.0001). Both T-1 and T-2 were linearly proportional to material contents. T-2 relaxivities [26.458 ml(g s)(-1) for abscesses and 21.455 ml (g s)(-1) for cysts] were higher than T-1 relaxivities [5.4766 ml (g s)(-1) for abscesses and 10.075 ml (g s)(-1) for cysts]. Discussion: Present T-2 measurements differentiate cysts from abscesses with a confidence interval of 95%. Because in vivo and in vitro image contrasts are changed by the same parameters, the T-2 findings should present valuable information for in vivo MRI. Hence the significant difference and the relaxivities may provide quantitative information for clinicians and researchers making image analyses. Conclusion: T-2 may differentiate cysts from abscesses. The difference in T-2 is related to the material content of samples. Dentomaxillofacial Radiology (2012) 41, 385-391. doi: 10.1259/dmfr/96188015