Differentiation of periapical granulomas and cysts by using dental MRI: a pilot study

Abstract

The purpose of this pilot study was to evaluate whether periapical granulomas can be differentiated from periapical cysts in vivo by using dental magnetic resonance imaging (MRI). Prior to apicoectomy, 11 patients with radiographically confirmed periapical lesions underwent dental MRI, including fat-saturated T2-weighted (T2wFS) images, non-contrast-enhanced T1-weighted images with and without fat saturation (T1w/T1wFS), and contrast-enhanced fat-saturated T1-weighted (T1wFS+C) images. Two independent observers performed structured image analysis of MRI datasets twice. A total of 15 diagnostic MRI criteria were evaluated, and histopathological results (6 granulomas and 5 cysts) were compared with MRI characteristics. Statistical analysis was performed using intraclass correlation coefficient (ICC), Cohen’s kappa (κ), Mann–Whitney U-test and Fisher’s exact test. Lesion identification and consecutive structured image analysis was possible on T2wFS and T1wFS+C MRI images. A high reproducibility was shown for MRI measurements of the maximum lesion diameter (intraobserver ICC = 0.996/0.998; interobserver ICC = 0.997), for the “peripheral rim” thickness (intraobserver ICC = 0.988/0.984; interobserver ICC = 0.970), and for all non-quantitative MRI criteria (intraobserver-κ = 0.990/0.995; interobserver-κ = 0.988). In accordance with histopathological results, six MRI criteria allowed for a clear differentiation between cysts and granulomas: (1) outer margin of lesion, (2) texture of “peripheral rim” in T1wFS+C, (3) texture of “lesion center” in T2wFS, (4) surrounding tissue involvement in T2wFS, (5) surrounding tissue involvement in T1wFS+C and (6) maximum “peripheral rim” thickness (all: P < 0.05). In conclusion, this pilot study indicates that radiation-free dental MRI enables a reliable differentiation between periapical cysts and granulomas in vivo. Thus, MRI may substantially improve treatment strategies and help to avoid unnecessary surgery in apical periodontitis.

Dental imaging: Diagnosing tooth root lesions using magnetic resonance imaging

Magnetic resonance imaging (MRI) can differentiate between periapical (apex of a tooth root) cysts and granulomas (inflammations usually caused by infections). MRI is a radiation-free, non-invasive imaging technique, and a team headed by Tim Hilgenfeld at Heidelberg University Hospital in Germany conducted a pilot study to determine whether dental MRI could be used to distinguish periapical cysts from granulomas in 11 patients with confirmed periapical lesions. The authors found that dental MRI allowed for the identification of six characteristics, each of which had the capacity to clearly differentiate between periapical cysts and granulomas. The team’s findings need to be confirmed in future studies with larger numbers of patients. But the results could have a substantial clinical impact in improving diagnoses and avoiding unnecessary surgery in patients with periapical lesions.