MRI Deep Learning‐Based Automatic Segmentation of Interventricular Septum for Black‐Blood Myocardial T2* Measurement in Thalassemia

Abstract

BackgroundThe T2* value of interventricular septum is routinely reported for grading myocardial iron load in thalassemia major, and automatic segmentation of septum could shorten analysis time and reduce interobserver variability.PurposeTo develop a deep learning‐based method for automatic septum segmentation from black‐blood MR images for the myocardial T2* measurement of thalassemia patients.Study TypeRetrospective.Population/SubjectsOne hundred forty‐six transfusion‐dependent thalassemia patients with cardiac MR examinations from two centers. Data from Center 1 (1.5 T) were assigned to the training (100 examinations) and internal testing (20 examinations) sets; data from Center 2 were assigned to the external testing set (26 examinations; 10 at 1.5 T and 16 at 3.0 T).Field Strength/Sequence1.5 T and 3.0 T, multiecho gradient‐echo sequence.AssessmentA modified attention U‐Net for septum segmentation was constructed and trained, and its performance evaluated on unseen internal and external datasets. T2* was measured by fitting the average septum signal, separately segmented by automatic and manual methods.Statistical TestsAgreement between manual and automatic septum segmentations was assessed with the Dice coefficient, and T2* agreement was assessed using the Bland–Altman plot and the coefficient of variation (CoV).ResultsThe median Dice coefficient of deep network‐based septum segmentation was 0.90 [0.05] on the internal dataset, 0.82 [0.10] on the external 1.5 T dataset, and 0.86 [0.14] on the external 3.0 T dataset. T2* measurements using automatic segmentation corresponded with those from manual segmentation, with a mean difference of 0.02 (95% LoA: −0.74 to 0.79) msec, 0.43 (95% LoA: −2.1 to 3.0) msec, and 0.36 (95% LoA: −0.72 to 1.4) msec on the three datasets. The CoVs between the two methods were 3.1%, 7.0%, and 6.1% on the internal and two external datasets, respectively.Data ConclusionsThe proposed septum segmentation yielded myocardial T2* measurements which were highly consistent with those obtained by manual segmentation. This automatic approach may facilitate data processing and avoid operator‐dependent variability in practice.Evidence Level4Technical EfficacyStage 1