title: MRI sequences for the detection of individual lymph nodes in regional breast radiotherapy planning.
abstract: OBJECTIVE
  In regional radiotherapy (RT) for patients with breast cancer, lymph node (LN) targets are delineated on CT, defined by anatomical boundaries. By identifying individual LNs, MRI-based delineations may reduce target volumes and thereby toxicity. We optimized MRI sequences for this purpose. Our aim was to evaluate the techniques for LN delineation in RT planning.
  
  
  METHODS
  Supine MRI was explored at 1.5 T in RT position (arms in abduction). 5 MRI techniques were optimized in 10 and evaluated in 12 healthy female volunteers. The scans included one T1 weighted (T1w), three T2 weighted (T2w) and a diffusion-weighted imaging (DWI) technique. Quantitative evaluation was performed by scoring LN numbers per volunteer and per scan. Qualitatively, scans were assessed on seven aspects, including LN contrast, anatomical information and insensitivity to motion during acquisition.
  
  
  RESULTS
  Two T2w fast spin-echo (FSE) methods showed the highest LN numbers (median 24 axillary), high contrast, excellent fat suppression and relative insensitivity to motion during acquisition. A third T2w sequence and DWI showed significantly fewer LNs (14 and 10) and proved unsuitable due to motion sensitivity and geometrical uncertainties. T1w MRI showed an intermediate number of LNs (17), provided valuable anatomical information, but lacked LN contrast.
  
  
  CONCLUSIONS
  Explicit LN imaging was achieved, in supine RT position, using MRI. Two T2w FSE techniques had the highest detection rates and were motion insensitive. T1w MRI showed anatomical information. MRI enables direct delineation of individual LNs.
  
  
  CONCLUSIONS
  Our optimized MRI scans enable accurate target definition in MRI-guided regional breast RT and development of personalized treatments.
authors.affiliation: 1 Department of Radiotherapy, University Medical Centre Utrecht, Utrecht, Netherlands.
authors.forename: Tristan C F
authors.identifier: http://orcid.org/0000-0001-8493-8247
authors.initials: TC
authors.lastname: van Heijst
authors.affiliation: 1 Department of Radiotherapy, University Medical Centre Utrecht, Utrecht, Netherlands.
authors.forename: Bram
authors.initials: B
authors.lastname: van Asselen
authors.affiliation: 2 Department of Radiology, University Medical Centre Utrecht, Utrecht, Netherlands.
authors.forename: Ruud M
authors.initials: RM
authors.lastname: Pijnappel
authors.affiliation: 1 Department of Radiotherapy, University Medical Centre Utrecht, Utrecht, Netherlands.
authors.forename: Marissa
authors.initials: M
authors.lastname: Cloos-van Balen
authors.affiliation: 1 Department of Radiotherapy, University Medical Centre Utrecht, Utrecht, Netherlands.
authors.forename: Jan J W
authors.initials: JJ
authors.lastname: Lagendijk
authors.affiliation: 1 Department of Radiotherapy, University Medical Centre Utrecht, Utrecht, Netherlands.
authors.forename: Desirée
authors.initials: D
authors.lastname: van den Bongard
authors.affiliation: 1 Department of Radiotherapy, University Medical Centre Utrecht, Utrecht, Netherlands.
authors.forename: Mariëlle E P
authors.initials: ME
authors.lastname: Philippens
mesh_terms: D000328:Adult; D001940:Breast / Q000000981:diagnostic imaging / Q000473:pathology; D001943:Breast Neoplasms / Q000532:radiotherapy*; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000000981:diagnostic imaging* / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D055815:Young Adult