A comparative evaluation of 3 different free-form deformable image registration and contour propagation methods for head and neck MRI : the case of parotid changes radiotherapy

Purpose: To validate and compare the deformable image registration and parotid contour propagation process for head and neck magnetic resonance imaging in patients treated with radiotherapy using 3 different approachesthe commercial MIM, the open-source Elastix software, and an optimized version of it. Materials and Methods: Twelve patients with head and neck cancer previously treated with radiotherapy were considered. Deformable image registration and parotid contour propagation were evaluated by considering the magnetic resonance images acquired before and after the end of the treatment. Deformable image registration, based on free-form deformation method, and contour propagation available on MIM were compared to Elastix. Two different contour propagation approaches were implemented for Elastix software, a conventional one (DIR_Trx) and an optimized homemade version, based on mesh deformation (DIR_Mesh). The accuracy of these 3 approaches was estimated by comparing propagated to manual contours in terms of average symmetric distance, maximum symmetric distance, Dice similarity coefficient, sensitivity, and inclusiveness. Results: A good agreement was generally found between the manual contours and the propagated ones, without differences among the 3 methods; in few critical cases with complex deformations, DIR_Mesh proved to be more accurate, having the lowest values of average symmetric distance and maximum symmetric distance and the highest value of Dice similarity coefficient, although nonsignificant. The average propagation errors with respect to the reference contours are lower than the voxel diagonal (2 mm), and Dice similarity coefficient is around 0.8 for all 3 methods. Conclusion: The 3 free-form deformation approaches were not significantly different in terms of deformable image registration accuracy and can be safely adopted for the registration and parotid contour propagation during radiotherapy on magnetic resonance imaging. More optimized approaches (as DIR_Mesh) could be preferable for critical deformations

Delayed Gadolinium-Enhanced Cardiac Magnetic Resonance in Patients With Chronic Myocarditis Presenting With Heart Failure or Recurrent Arrhythmias

ObjectivesWe evaluated the effectiveness of contrast-enhanced cardiac magnetic resonance (CE-CMR) in detecting chronic myocarditis (CM).BackgroundChronic myocarditis represents a common evolution of acute myocarditis. Although CE-CMR has been revealed to be effective in identifying areas of myocardial damage in acute myocarditis, its role in the diagnosis of chronic myocardial inflammation has not yet been investigated.MethodsTwenty-three patients with CM underwent CE-CMR and endomyocardial biopsy (EMB). Chronic myocarditis was defined by the presence of: 1) chronic (>6 months) heart failure symptoms and/or repetitive ventricular arrhythmias; 2) no history of recent flu-like symptoms or infections; and 3) histologic evidence of active myocarditis (AM) or borderline myocarditis (BM) according to Dallas criteria. Contrast-enhanced cardiac magnetic resonance included black-blood T2-weighted (BBT2w) images without and with fat saturation and delayed three-dimensional T1 turbo field-echo inversion-recovery sequences obtained 15 min after gadolinium injection.ResultsHistology showed AM in 14 patients and BM in 9 patients. FatSat BBT2w revealed the presence of edema in five (36%) patients with AM but not in BM patients. Areas of late enhancement (LE) were observed in 12 (84%) subjects with AM and in 4 (44%) cases with BM. A mid-wall LE pattern was the most frequent finding in both groups while a subepicardial distribution of LE was observed only in patients with AM.ConclusionsContrast-enhanced cardiac magnetic resonance identified areas of myocardial inflammation in up to 70% of patients with biopsy-proven CM. We suggest that CE-CMR may be a useful non-invasive diagnostic tool in patients with CM, and it may indicate and even guide the execution of left ventricular EMB with relevant prognostic and therapeutic implications