MRI-based inter- and intrafraction motion analysis of the pancreatic tail and spleen as preparation for adaptive MRI-guided radiotherapy in neuroblastoma

• Published in: Radiation oncology (London, England) England), 2023-10, Vol.18 (1), p.1-160, Article 160
• Main Authors: Van Ommen, Fasco, le Quellenec, Gaelle A.T, Willemsen-Bosman, Mirjam E, van Noesel, Max M, van den Heuvel-Eibrink, Marry M, Seravalli, Enrica, Kroon, Petra S, Janssens, Geert O
• Format: Article
• Language: English
• Subjects: Abdomen; Analysis; Antibiotics; Care and treatment; Center of gravity; Demographic aspects; Diabetes; Diagnosis; Dosimetry; Gadolinium; Infections; Interfraction motion; Intrafraction motion; Magnetic resonance imaging; Mortality; MRI-guided radiotherapy; Neuroblastoma; Pancreas; Patient outcomes; Patients; Pediatric radiotherapy; Pediatrics; Radiation; Radiation therapy; Radiotherapy; Registration; Spleen; Tails; Toxicity; Tumors; Vertebrae
• ISSN: 1748-717X; 1748-717X
• DOI: 10.1186/s13014-023-02347-9

Background In pediatric radiotherapy treatment planning of abdominal tumors, dose constraints to the pancreatic tail/spleen are applied to reduce late toxicity. In this study, an analysis of inter- and intrafraction motion of the pancreatic tail/spleen is performed to estimate the potential benefits of online MRI-guided radiotherapy (MRgRT). Materials and methods Ten randomly selected neuroblastoma patients (median age: 3.4 years), irradiated with intensity-modulated arc therapy at our department (prescription dose: 21.6/1.8 Gy), were retrospectively evaluated for inter- and intrafraction motion of the pancreatic tail/spleen. Three follow-up MRIs (T2- and T1-weighted [+ or -] gadolinium) were rigidly registered to a planning CT (pCT), on the vertebrae around the target volume. The pancreatic tail/spleen were delineated on all MRIs and pCT. Interfraction motion was defined as a center of gravity change between pCT and T2-weighted images in left-right (LR), anterior-posterior (AP) and cranial-caudal (CC) direction. For intrafraction motion analysis, organ position on T1-weighted [+ or -] gadolinium was compared to T2-weighted. The clinical radiation plan was used to estimate the dose received by the pancreatic tail/spleen for each position. Results The median (IQR) interfraction motion was minimal in LR/AP, and largest in CC direction; pancreatic tail 2.5 mm (8.9), and spleen 0.9 mm (3.9). Intrafraction motion was smaller, but showed a similar motion pattern (pancreatic tail, CC: 0.4 mm (1.6); spleen, CC: 0.9 mm (2.8)). The differences of Dmean associated with inter- and intrafraction motions ranged from - 3.5 to 5.8 Gy for the pancreatic tail and - 1.2 to 3.0 Gy for the spleen. In 6 out of 10 patients, movements of the pancreatic tail and spleen were highlighted as potentially clinically significant because of [greater than or equal to] 1 Gy dose constraint violation. Conclusion Inter- and intrafraction organ motion results into unexpected constrain violations in 60% of a randomly selected neuroblastoma cohort, supporting further prospective exploration of MRgRT. Keywords: Neuroblastoma, Pediatric radiotherapy, Interfraction motion, Intrafraction motion, MRI-guided radiotherapy