A clustering approach to 4D MRI retrospective sorting for the investigation of different surrogates. (February 2019)

• Record Type: Journal Article
• Authors: Meschini, Giorgia; Paganelli, Chiara; Gianoli, Chiara; Summers, Paul; Bellomi, Massimo; Baroni, Guido; Riboldi, Marco
• Is Part Of: Physica medica. Volume 58(2019)
• Page Start: 107
• Page End: 113
• Publication Date: 2019-02
• Subjects: 4D MRI -- Retrospective sorting -- Liver; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2019.02.003
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: We propose a novel method for retrospective 4D MRI sorting, based on clustering. Single/multiple internal and external surrogates were tested vs. a reference method. The use of the external surrogate caused severe sorting artifacts. Multiple internal surrogates led to image quality similar to the reference method. With internal surrogates, our method improved the description of range of motion. Abstract: Purpose: In retrospective 4-Dimensional Magnetic Resonance Imaging (4D MRI) sorting, respiratory surrogate selection affects the image quality of reconstructed volumes. We propose a method for retrospective 4D MRI sorting based on clustering, which allowed us to compare the performance of single or multiple internal surrogates vs. a conventional external signal. Methods: A k-medoids clustering algorithm was exploited for sorting 2D MRI into 4D MRI, relying on (A) multiple or (B) single automatically tracked internal landmarks or (C) respiratory belt signal. 4D MRI reconstructions for seven liver cancer patients were compared to those of the state-of-the-art mutual information (MI) approach. Sorting artifacts were measured by the root mean square error (RMSE) between the diaphragm profile and a fitted second order curve. Diaphragm and tumor motions were evaluated. Results: The median RMSEs ranged 0.97–1.66 mm, 1.24–1.89 mm, 1.43–2.27 mm, 1.74–3.72 mm for the MI, (A), (B) and (C) methods, respectively. Significant differences (Friedman, α = 5%) were found between (C) and all other methods, and between (B) and MI approaches. The discrepancies between (A) and MI approaches ranged 1.1–6.2 mm and 0.7–5.3 mm respectively in diaphragm and tumor motions. Methods (A) and (B) showed similar ranges of motion. Conclusion: With multiple internal points, our method yielded the description of a higher range of motion and similar image quality with respect to the MI approach. The single point method led to more artifacts, suggesting the superior suitability of multiple internal surrogates for retrospective 4D MRI sorting. Considering internal rather than external information favored superior performance.