title: Conventional 3D staging PET/CT in CT simulation for lung cancer: impact of rigid and deformable target volume alignments for radiotherapy treatment planning.
abstract: OBJECTIVE
  Positron emission tomography (PET)/CT scans can improve target definition in radiotherapy for non-small cell lung cancer (NSCLC). As staging PET/CT scans are increasingly available, we evaluated different methods for co-registration of staging PET/CT data to radiotherapy simulation (RTP) scans.
  
  
  METHODS
  10 patients underwent staging PET/CT followed by RTP PET/CT. On both scans, gross tumour volumes (GTVs) were delineated using CT (GTV(CT)) and PET display settings. Four PET-based contours (manual delineation, two threshold methods and a source-to-background ratio method) were delineated. The CT component of the staging scan was co-registered using both rigid and deformable techniques to the CT component of RTP PET/CT. Subsequently rigid registration and deformation warps were used to transfer PET and CT contours from the staging scan to the RTP scan. Dice's similarity coefficient (DSC) was used to assess the registration accuracy of staging-based GTVs following both registration methods with the GTVs delineated on the RTP PET/CT scan.
  
  
  RESULTS
  When the GTV(CT) delineated on the staging scan after both rigid registration and deformation was compared with the GTV(CT)on the RTP scan, a significant improvement in overlap (registration) using deformation was observed (mean DSC 0.66 for rigid registration and 0.82 for deformable registration, p = 0.008). A similar comparison for PET contours revealed no significant improvement in overlap with the use of deformable registration.
  
  
  CONCLUSIONS
  No consistent improvements in similarity measures were observed when deformable registration was used for transferring PET-based contours from a staging PET/CT. This suggests that currently the use of rigid registration remains the most appropriate method for RTP in NSCLC.
authors.affiliation: Department of Radiotherapy, VU University Medical Center, Amsterdam, The Netherlands. Gerry.Hanna@gmail.com
authors.forename: G G
authors.initials: GG
authors.lastname: Hanna
authors.forename: J R
authors.initials: JR
authors.lastname: Van Sörnsen De Koste
authors.forename: K J
authors.initials: KJ
authors.lastname: Carson
authors.forename: J M
authors.initials: JM
authors.lastname: O'Sullivan
authors.forename: A R
authors.initials: AR
authors.lastname: Hounsell
authors.forename: S
authors.initials: S
authors.lastname: Senan
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D003198:Computer Simulation; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D008297:Male; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18