610 Strahlenther Onkol 2007 · No. 11 © Urban & Vogel Strahlentherapie und Onkologie Original Article Transabdominal Ultrasonography, Computed Tomo- graphy and Electronic Portal Imaging for 3-Dimensional Conformal Radiotherapy for Prostate Cancer Barbara Alicja Jereczek-Fossa 1, 5 , Federica Cattani 2 , Cristina Garibaldi 2 , Dario Zerini 1 , Raffaella Cambria 2 , Genoveva Ionela Boboc 1 , Marco Valenti 2 , Anna Kowalczyk 4 , Andrea Vavassori 1 , Giovanni Battista Ivaldi 1 , Mario Ciocca 2 , Deliu Victor Matei 3 , Ottavio De Cobelli 3, 5 , Roberto Orecchia 1, 5 Purpose: To evaluate the feasibility and accuracy of daily B-mode acquisition and targeting ultrasound-based prostate localiza- tion (BAT TM ) and to compare it with computed tomography (CT) and electronic portal imaging (EPI) in 3-dimensional conformal radiotherapy (3-D CRT) for prostate cancer. Patients and Methods: Ten patients were treated with 3-D CRT (72 Gy/30 fractions, 2.4 Gy/fraction, equivalent to 80 Gy/40 frac- tions, for α/β ratio of 1.5 Gy) and daily BAT-based prostate localization. For the first 5 fractions, CT and EPI were also performed in order to compare organ-motion and set-up error, respectively. Results: 287 BAT-, 50 CT- and 46 EPI-alignments were performed. The average BAT-determined misalignments in latero-lateral, antero-posterior and cranio-caudal directions were –0.9 mm ± 3.3 mm, 1.0 mm ± 4.0 mm and –0.9 mm ± 3.8 mm, respectively. The differences between BAT- and CT-determined organ-motion in latero-lateral, antero-posterior and cranio-caudal directions were 2.7 mm ± 1.9 mm, 3.9 ± 2.8 mm and 3.4 ± 3.0 mm, respectively. Weak correlation was found between BAT- and CT-determined misalignments in antero-posterior direction, while no correlation was observed in latero-lateral and cranio-caudal directions. The correlation was more significant when only data of good image-quality patients were analyzed (8 patients). Conclusion: BAT ensures the relative positions of target are the same during treatment and in treatment plan, however, the reli- ability of alignment is patient-dependent. The average BAT-determined misalignments were small, confirming the prevalence of random errors in 3-D CRT. Further study is warranted in order to establish the clinical value of BAT. Key Words: Prostate cancer · 3-D conformal radiotherapy · Ultrasonography · Electronic portal imaging · Computed tomography Strahlenther Onkol 2007;183:610–6 DOI 10.1007/s00066-007-1702-5 Transabdominaler Ultraschall, Computertomographie und elektronisches Portal-Imaging für 3D-konformale Strahlen- therapie des Prostatakrebses Ziel: Ziel dieser Studie ist es, die Möglichkeit und Genauigkeit der täglichen B-mode-Akquisition und zielgerichteten ultraschall- basierten Prostatapositionierung (BAT TM ) einzuschätzen und sie mit der Computertomographie (CT) und dem elektronischen Portal-Imaging (EPI) bei der 3D-konformalen Strahlentherapie (3D-CRT) des Prostatakrebses zu vergleichen. Patienten und Methodik: 10 Patienten wurden mit 3D-CRT (72 Gy/30 Fraktionen, 2,4 Gy/Fraktion, äquivalent zu 80 Gy/40 Fraktionen, α/β-Verhältnis von 1,5 Gy ) und täglicher BAT behandelt. Für die ersten 5 Fraktionen wurden auch CT und EPI durch- geführt, um jeweils die Bewegung der Organe und die Set-up-Fehler zu vergleichen. Ergebnisse: 287 BAT-, 50 CT- und 46 EPI-Positionierungen wurden durchgeführt. Der durchschnittliche BAT-Positionierungs- fehler war jeweils –0,9 mm ± 3,3 mm, 1,0 mm ± 4,0 mm und –0,9 mm ± 3,8 mm in den latero-lateralen, anterior-posterioren und kraniokaudalen Richtungen. Die Unterschiede zwischen der BAT- und CT-Technik bei der Bestimmung der Organbewegung in den latero-lateralen, anterior-posterioren und kraniokaudalen Richtungen waren jeweils 2,7 mm ± 1,9 mm, 3,9 ± 2,8 mm und Received: November 23, 2006, accepted: July 24, 2007 1 Department of Radiation Oncology of the European Institute of Oncology, Milan, Italy, 2 Department of Medical Physics of the European Institute of Oncology, Milan, Italy, 3 Department of Urology of the European Institute of Oncology, Milan, Italy, 4 Department of Oncology and Radiotherapy, Medical University, Gdansk, Poland, 5 University of Milan, Milan, Italy.