title: Target localization for post-prostatectomy patients using CT and ultrasound image guidance.
abstract: We conducted a study comparing B-mode acquisition and targeting (BAT) ultrasound alignments based on CT data in the postoperative setting. CT scans were obtained with a Primatom CT-on-rails on nine patients. Two CT scans were obtained each week, while setup error was minimized by BAT ultrasounds. For the first three patients, a direct comparison was performed. For the next six patients, a template based on the shifts from the week 1 CT during treatment was used for subsequent setup. Comparison of isocenter shifts between the BAT ultrasound and CT was made by the difference, absolute difference, and improvement (using CT alignments as the reference technique). A total of 90 image comparisons were made. The average interfraction motion was 3.2 mm in the lateral, 3.0 mm in the longitudinal, and 5.1 mm in the AP direction. The results suggest that the CTbased ultrasound templates can improve the localization of the prostate bed when the initial displacements are greater than 4 mm. For initial displacements smaller than 4 mm, the technique neither improved nor worsened target localization. However, ultrasound alignments performed without the use of a template deteriorated patient positioning for two out of three patients, demonstrating that the use of a CT template was beneficial even at small initial displacements.
authors.affiliation: Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA. K_Paskalev@fccc.edu
authors.forename: Kamen
authors.initials: K
authors.lastname: Paskalev
authors.forename: Steven
authors.initials: S
authors.lastname: Feigenberg
authors.forename: Rojymon
authors.initials: R
authors.lastname: Jacob
authors.forename: Shawn
authors.initials: S
authors.lastname: McNeeley
authors.forename: Eric
authors.initials: E
authors.lastname: Horwitz
authors.forename: Robert
authors.initials: R
authors.lastname: Price
authors.forename: Charlie
authors.initials: C
authors.lastname: Ma
authors.forename: Alan
authors.initials: A
authors.lastname: Pollack
mesh_terms: D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis* / Q000532:radiotherapy*; D011182:Postoperative Care / Q000379:methods; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy* / Q000601:surgery; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D025321:Surgery, Computer-Assisted / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014463:Ultrasonography / Q000379:methods*