title: Ultrasound versus Cone-beam CT image-guided radiotherapy for prostate and post-prostatectomy pretreatment localization.
abstract: OBJECTIVE
  To evaluate the accuracy of an intra-modality trans-abdominal ultrasound (TA-US) device against soft-tissue based Cone-Beam Computed tomography (CBCT) registration for prostate and post-prostatectomy pre-treatment positioning.
  
  
  METHODS
  The differences between CBCT and US shifts were calculated on 25 prostate cancer patients (cohort A) and 11 post-prostatectomy patients (cohort B), resulting in 284 and 106 paired shifts for cohorts A and B, respectively. As a second step, a corrective method was applied to the US registration results to decrease the systematic shifts observed between TA-US and CBCT results. This method consisted of subtracting the mean difference obtained between US and CBCT registration results during the first 3 sessions from the US registration results of the subsequent sessions. Inter-operator registration variability (IOV) was also investigated for both modalities.
  
  
  RESULTS
  After initial review, about 20% of the US images were excluded because of insufficient quality. The average differences between US and CBCT were: 2.8 ± 4.1 mm, -0.9 ± 4.2 mm, 0.4 ± 3.4 mm for cohort A and 1.3 ± 5.0 mm, -2.3 ± 4.6 mm, 0.5 ± 2.9 mm for cohort B, in the anterior-posterior (AP), superior-inferior (SI) and lateral (LR) directions, respectively. After applying the corrective method, only the differences in the AP direction remained significant (p < 0.05). The IOV values were between 0.6-2.0 mm and 2.1-3.5 mm for the CBCT and TA-US modalities, respectively.
  
  
  CONCLUSIONS
  Based on the obtained results and on the image quality, the TA-US imaging modality is not safely interchangeable with CBCT for pre-treatment repositioning. Treatment margins adaptation based on the correction of the systematic shifts should be considered.
authors.affiliation: CREATIS, Université de Lyon, Lyon, France; CNRS UMR5220, Lyon, France; Inserm U1044, Lyon, France; INSA-Lyon, Lyon, France; Université Lyon 1, Lyon, France; Centre Léon Bérard, Lyon, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Fargier-Voiron
authors.affiliation: CREATIS, Université de Lyon, Lyon, France; CNRS UMR5220, Lyon, France; Inserm U1044, Lyon, France; INSA-Lyon, Lyon, France; Université Lyon 1, Lyon, France; Centre Léon Bérard, Lyon, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Presles
authors.affiliation: Léon Bérard Cancer Center, University of Lyon, F-69373 Lyon, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Pommier
authors.affiliation: Léon Bérard Cancer Center, University of Lyon, F-69373 Lyon, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Munoz
authors.affiliation: CREATIS, Université de Lyon, Lyon, France; CNRS UMR5220, Lyon, France; Inserm U1044, Lyon, France; INSA-Lyon, Lyon, France; Université Lyon 1, Lyon, France; Centre Léon Bérard, Lyon, France.
authors.forename: Simon
authors.initials: S
authors.lastname: Rit
authors.affiliation: CREATIS, Université de Lyon, Lyon, France; CNRS UMR5220, Lyon, France; Inserm U1044, Lyon, France; INSA-Lyon, Lyon, France; Université Lyon 1, Lyon, France; Centre Léon Bérard, Lyon, France.
authors.forename: David
authors.initials: D
authors.lastname: Sarrut
authors.affiliation: CREATIS, Université de Lyon, Lyon, France; CNRS UMR5220, Lyon, France; Inserm U1044, Lyon, France; INSA-Lyon, Lyon, France; Université Lyon 1, Lyon, France; Centre Léon Bérard, Lyon, France. Electronic address: marie-claude.biston@lyon.unicancer.fr.
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Biston
mesh_terms: D054893:Cone-Beam Computed Tomography; D006801:Humans; D008297:Male; D015588:Observer Variation; D011446:Prospective Studies; D011467:Prostate / Q000000981:diagnostic imaging* / Q000601:surgery; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000601:surgery; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D014463:Ultrasonography
keywords: IGRT; Post-prostatectomy; Prostate; Ultrasound