title: Helical tomotherapy for SIB and hypo-fractionated treatments in lung carcinomas: a 4D Monte Carlo treatment planning study.
abstract: OBJECTIVE
  To evaluate the impact of intra-fraction motion induced by regular breathing on treatment quality for helical tomotherapy treatments.
  
  
  METHODS
  Four patients treated by simultaneous-integrated boost (SIB) and three by hypo-fractionated stereotactic treatments (hypo-fractionated, 18 Gy/fraction) were included. All patients were coached to ensure regular breathing. For the SIB group, the tumor volume was delineated using CT information only (CTV(CT)) and the boost region was based on PET information (GTV(PET), no CTV extension). In the hypo-fractionated group, a GTV based on CT information was contoured. In both groups, ITVs were defined according to 4D data. The PTV included the ITV plus a setup error margin. The treatment was planned using the tomotherapy TPS on 3D CT images. In order to verify the impact of intra-fraction motion and interplay effects, dose calculations were performed using a previously validated Monte Carlo model of tomotherapy (TomoPen): first on the planning 3D CT ("planned dose") and second, on the 10 phases of the 4D scan. For the latter, two dose distributions, termed "interplay simulated" or "no interplay" were computed with and without beamlet-phase correlation over the 10 phases and combined using deformable dose registration.
  
  
  RESULTS
  In all cases, DVHs of "interplay simulated" dose distributions complied within 1% of the original clinical objectives used for planning, defined according to ICRU (report 83) and RTOG (trials 0236 and 0618) recommendations, for SIB and hypo-fractionated groups, respectively. For one patient in the hypo-fractionated group, D(mean) to the CTV(CT) was 2.6% and 2.5% higher than "planned" for "interplay simulated" and "no interplay", respectively.
  
  
  CONCLUSIONS
  For the patients included in this study, assuming regular breathing, the results showed that interplay of breathing and tomotherapy delivery motions did not affect significantly plan delivery accuracy. Hence, accounting for intra-fraction motion through the definition of an ITV volume was sufficient to ensure tumor coverage.
authors: Université Catholique de Louvain, Brussels, Belgium. esterpin@yahoo.fr
authors: Edmond
authors: E
authors: Sterpin
authors: Guillaume
authors: G
authors: Janssens
authors: Jonathan
authors: J
authors: Orban de Xivry
authors: Samuel
authors: S
authors: Goossens
authors: Marie
authors: M
authors: Wanet
authors: John A
authors: JA
authors: Lee
authors: Antoine
authors: A
authors: Delor
authors: Vanesa
authors: V
authors: Bol
authors: Stefaan
authors: S
authors: Vynckier
authors: Vincent
authors: V
authors: Gregoire
authors: Xavier
authors: X
authors: Geets
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D000077192:Adenocarcinoma of Lung; D000368:Aged; D016477:Artifacts; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D009367:Neoplasm Staging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D055425:Respiratory-Gated Imaging Techniques; D018570:Risk Assessment; D012494:Sampling Studies; D036542:Tomography, Spiral Computed