title: Fast imaging employing steady-state acquisition (FIESTA) MRI to investigate cerebrospinal fluid (CSF) within dural reflections of posterior fossa cranial nerves.
abstract: OBJECTIVE
  There is no consensus approach to covering skull base meningeal reflections-and cerebrospinal fluid (CSF) therein-of the posterior fossa cranial nerves (CNs VII-XII) when planning radiotherapy (RT) for medulloblastoma and ependymoma. We sought to determine whether MRI and specifically fast imaging employing steady-state acquisition (FIESTA) sequences can answer this anatomical question and guide RT planning.
  
  
  METHODS
  96 posterior fossa FIESTA sequences were reviewed. Following exclusions, measurements were made on the following scans for each foramen respectively (left, right); internal acoustic meatus (IAM) (86, 84), jugular foramen (JF) (83, 85) and hypoglossal canal (HC) (42, 45). A protocol describes measurement procedure. Two observers measured distances for five cases and agreement was assessed. One observer measured all the remaining cases.
  
  
  RESULTS
  IAM and JF measurement interobserver variability was compared. Mean measurement difference between observers was -0.275 mm (standard deviation 0.557). IAM and JF measurements were normally distributed. Mean IAM distance was 12.2 mm [95% confidence interval (CI) 8.8-15.6]; JF was 7.3 mm (95% CI 4.0-10.6). The HC was difficult to visualize on many images and data followed a bimodal distribution.
  
  
  CONCLUSIONS
  Dural reflections of posterior fossa CNs are well demonstrated by FIESTA MRI. Measuring CSF extension into these structures is feasible and robust; mean CSF extension into IAM and JF was measured. We plan further work to assess coverage of these structures with photon and proton RT plans. Advances in knowledge: We have described CSF extension beyond the internal table of the skull into the IAM, JF and HC. Oncologists planning RT for patients with medulloblastoma and ependymoma may use these data to guide contouring.
authors.affiliation: 1 Department of Oncology, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Noble
authors.affiliation: 2 Department of Radiology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Scoffings
authors.affiliation: 1 Department of Oncology, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, UK.
authors.forename: Thankamma
authors.initials: T
authors.lastname: Ajithkumar
authors.affiliation: 1 Department of Oncology, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, UK.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Williams
authors.affiliation: 1 Department of Oncology, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, UK.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Jefferies
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002528:Cerebellar Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D002555:Cerebrospinal Fluid / Q000000981:diagnostic imaging*; D002648:Child; D002675:Child, Preschool; D003391:Cranial Nerves / Q000000981:diagnostic imaging* / Q000528:radiation effects; D004806:Ependymoma / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007223:Infant; D015192:Infratentorial Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008527:Medulloblastoma / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D008875:Middle Aged; D011880:Radiotherapy Planning, Computer-Assisted; D015203:Reproducibility of Results; D012189:Retrospective Studies