title: Magnetic resonance imaging of swallowing-related structures in nasopharyngeal carcinoma patients receiving IMRT: Longitudinal dose-response characterization of quantitative signal kinetics.
abstract: BACKGROUND
  We aim to characterize serial (i.e., acute and late) MRI signal intensity (SI) changes in dysphagia-associated structures as a function of radiotherapy (RT) in nasopharyngeal cancer (NPC) patients.
  
  
  METHODS
  We retrospectively extracted data on 72 patients with stage III-IV NPC treated with intensity-modulated RT (IMRT). The mean T1- and T2-weighted MRI SIs were recorded for the superior pharyngeal constrictor (SPC) and soft palate (SP) at baseline, early-after IMRT, and last follow up, with normalization to structures receiving <5 Gy.
  
  
  RESULTS
  All structures had a significant increase in T2 SIs early after treatment, irrespective of the mean dose given. At last follow-up, the increase in T2 SI subsided completely for SPC and partially for SP. The T1 SI did not change significantly in early follow-up images of both structures; on late follow-up, patients with mean doses >62.25 Gy had a significant decrease in the corresponding T1 SI for SPC (1.6 ± 0.4 vs. 1.3 ± 0.4, P=0.007) but decreased non-significantly for SP.
  
  
  CONCLUSIONS
  Serial MRI acquisitions enable the identification of both early and late radiation-induced changes in swallowing structures after definitive IMRT for NPC. Dose dependent decrease in late T1 SI is associated with higher RT doses to the superior pharyngeal constrictor muscle; while dose independent increase in SI for both structures in early post-RT T2 images is observed and subsides after therapy. Further efforts will seek to elucidate the relationship between dose-dependent muscle SI changes and functional alteration of swallowing muscles.
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA; The University of Texas Medical School at Houston, USA. Electronic address: Jay.A.Messer@uth.tmc.edu.
authors.forename: Jay A
authors.initials: JA
authors.lastname: Messer
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA; Department of Clinical Oncology and Nuclear Medicine, Faculty of Medicine, University of Alexandria, Egypt. Electronic address: asmohamed@mdanderson.org.
authors.forename: Abdallah S R
authors.initials: AS
authors.lastname: Mohamed
authors.affiliation: Department of Head and Neck Surgery, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Hutcheson
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA; Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Yao
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Department of Head and Neck Surgery, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Jan S
authors.initials: JS
authors.lastname: Lewin
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Jihong
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Head and Neck Surgery, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Stephen Y
authors.initials: SY
authors.lastname: Lai
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Frank
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Adam S
authors.initials: AS
authors.lastname: Garden
authors.affiliation: Department of Head and Neck Surgery, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Vlad
authors.initials: V
authors.lastname: Sandulache
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA; The University of Texas Medical School at Houston, USA.
authors.forename: Hillary
authors.initials: H
authors.lastname: Eichelberger
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA; The University of Texas Medical School at Houston, USA.
authors.forename: Chloe C
authors.initials: CC
authors.lastname: French
authors.affiliation: Department of Diagnostic Imaging, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Rivka R
authors.initials: RR
authors.lastname: Colen
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Jack
authors.initials: J
authors.lastname: Phan
authors.affiliation: Department of Radiology, Harvard Medical School, Boston, USA.
authors.forename: Jayashree
authors.initials: J
authors.lastname: Kalpathy-Cramer
authors.affiliation: Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Hazle
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: David I
authors.initials: DI
authors.lastname: Rosenthal
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: G Brandon
authors.initials: GB
authors.lastname: Gunn
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA. Electronic address: cdfuller@mdanderson.org.
authors.forename: Clifton D
authors.initials: CD
authors.lastname: Fuller
mesh_terms: D000328:Adult; D000368:Aged; D002277:Carcinoma; D003680:Deglutition Disorders / Q000209:etiology / Q000473:pathology*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D010160:Palate, Soft / Q000473:pathology; D010609:Pharyngeal Muscles / Q000528:radiation effects*; D011832:Radiation Injuries / Q000473:pathology*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D055815:Young Adult
keywords: Dose–response; Dysphagia; IMRT; Magnetic resonance imaging; Nasopharyngeal carcinoma; Superior pharyngeal constrictor
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