Simultaneously acquired MR/PET images compared with sequential MR/PET and PET/CT: alignment quality
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Published on: November 15, 2024
Cornelia B Brendle1, Holger Schmidt, Sabrina Fleischer
1Department of Radiology, Division of Diagnostic and Interventional Radiology, Eberhard-Karls University Tuebingen, Hoppe-Seyler-Str 3, 72076 Tuebingen, Germany.
Purpose:
To compare anatomic alignment between morphologic and positron emission tomography (PET) images acquired in the abdomen and pelvis by using simultaneous magnetic resonance (MR)/PET, PET/computed tomography (CT), and retrospective MR/PET fusion and to compare alignment between MR and PET in simultaneous and sequential thoracic MR/PET by using different breathing, registration, and gating protocols.
Materials And Methods:
Informed consent and institutional review board approval were obtained. The misalignment in 28 abdominal patient datasets was analyzed in simultaneous MR/PET, PET/CT, and retrospective MR/PET fusion. In seven thoracic MR/PET datasets, the effect of different breathing protocols, simultaneous, sequential, and MR-gated data acquisition was evaluated, and the effect of rigid registration versus nonregistered images was evaluated. Analysis of variance and subsequent Tukey test were used for statistical analysis.
Results:
The misalignment in all abdominal organs was reduced in simultaneous MR/PET compared with retrospectively fused MR and PET images (means, 5.8 mm vs 11.9 mm; P < .001), and in the urinary bladder compared with PET/CT (means, 5.9 mm vs 11.0 mm; P < .007). Thoracic MR/PET with inspiratory breath-hold MR showed the largest misalignment (mean, 24.5 mm; P < .001). None of the other thoracic protocols that were composed of different acquisition, registration, or gating procedures differed significantly from one another.
Conclusion:
The alignment of hybrid datasets acquired in simultaneous whole-body MR/PET was more accurate than retrospective fusion in all investigated abdominal organs, and more accurate than PET/CT in the urinary bladder; the alignment of thoracic MR/PET with expiratory breath hold or free-breathing MR was more exact than with inspiratory MR. However in this preliminary work the clinical importance of these degrees of misalignment was not assessed.
