title: Four-dimensional planning for motion synchronized dose delivery in lung stereotactic body radiation therapy.
abstract: To investigate a weighted four-dimensional (W-4D) treatment planning strategy based on the greater clinical advantage of the conformal over the intensity-modulated technique in lung stereotactic body radiotherapy (SBRT).
  
  
  
  Two planning strategies (individual-phase 4D [IP-4D] and W-4D) were evaluated in eighteen lung SBRT patients. The IP-4D plan can deliver a constant fluence during whole respiratory phases. The W-4D plan's key concept was to escalate (or reduce) fluence using a 4D optimization algorithm when the tumour target was out-of-line (or in-line) with an organ-at-risk. The fluence was converted to a dynamic multi-leaf collimator leaf sequence for deliverable 4D irradiation.
  
  
  
  In all patients, the W-4D plan enabled planning tumour volume conformity comparable to the IP-4D plan. The W-4D plan yielded a significantly lower maximum dose than the IP-4D plan for the spinal cord (-11%; p<0.01), oesophagus (-14%; p<0.01), heart (-22%; p=0.01) and stomach (-23%; p=0.07), and a lower mean dose to liver (-19%; p=0.18) while maintaining the mean dose to lung (-1%; p=0.23).
  
  
  
  W-4D is a robust, practical planning approach that achieves significant dose sparing relative to non-time-resolved tracking; it may be of greater clinical benefit in radiotherapy than the spatially intensity-modulated 4D approach.
authors.affiliation: University of Texas Southwestern Medical Center, Dallas, USA.
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Tachibana
authors.affiliation: University of Texas Southwestern Medical Center, Dallas, USA. Electronic address: amit.sawant@utsouthwestern.edu.
authors.forename: Amit
authors.initials: A
authors.lastname: Sawant
mesh_terms: D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D009038:Motion; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D047368:Tumor Burden
keywords: Lung; Motion management; Robust 4D treatment; SBRT