PURPOSE: The aim of this study was to quantify interfractional pancreatic position variation using fiducial markers visible on daily cone beam computed tomography (CBCT) scans. In addition, we analyzed possible migration of the markers to investigate their suitability for tumor localization. METHODS AND MATERIALS: For 13 pancreatic cancer patients with implanted Visicoil markers, CBCT scans were obtained before 17 to 25 fractions (300 CBCTs in total). Image registration with the reference CT was used to determine the displacement of the 2 to 3 markers relative to bony anatomy and to each other. We analyzed the distance between marker pairs as a function of time to identify marker registration error (SD of linear fit residuals) and possible marker migration. For each patient, we determined the mean displacement of markers relative to the reference CT (systematic position error) and the spread in displacements (random position error). From this, we calculated the group systematic error, Σ, and group random error, σ. RESULTS: Marker pair distances showed slight trends with time (range, -0.14 to 0.14 mm/day), possibly due to tissue deformation, but no shifts that would indicate marker migration. The mean SD of the fit residuals was 0.8 mm. We found large interfractional position variations, with for 116 of 300 (39%) fractions a 3-dimensional vector displacement of >10 mm. The spread in displacement varied significantly (P<.01) between patients, from a vector range of 9.1 mm to one of 24.6 mm. For the patient group, Σ was 3.8, 6.6, and 3.5 mm; and σ was 3.6, 4.7 and 2.5 mm, in left-right, superior-inferior, and anterior-posterior directions, respectively. CONCLUSIONS: We found large systematic displacements of the fiducial markers relative to bony anatomy, in addition to wide distributions of displacement. These results for interfractional position variation confirm the potential benefit of using fiducial markers rather than bony anatomy for daily online position verification for pancreatic cancer patients.
PURPOSE: The aim of this study was to quantify interfractional pancreatic position variation using fiducial markers visible on daily cone beam computed tomography (CBCT) scans. In addition, we analyzed possible migration of the markers to investigate their suitability for tumor localization. METHODS AND MATERIALS: For 13 pancreatic cancerpatients with implanted Visicoil markers, CBCT scans were obtained before 17 to 25 fractions (300 CBCTs in total). Image registration with the reference CT was used to determine the displacement of the 2 to 3 markers relative to bony anatomy and to each other. We analyzed the distance between marker pairs as a function of time to identify marker registration error (SD of linear fit residuals) and possible marker migration. For each patient, we determined the mean displacement of markers relative to the reference CT (systematic position error) and the spread in displacements (random position error). From this, we calculated the group systematic error, Σ, and group random error, σ. RESULTS: Marker pair distances showed slight trends with time (range, -0.14 to 0.14 mm/day), possibly due to tissue deformation, but no shifts that would indicate marker migration. The mean SD of the fit residuals was 0.8 mm. We found large interfractional position variations, with for 116 of 300 (39%) fractions a 3-dimensional vector displacement of >10 mm. The spread in displacement varied significantly (P<.01) between patients, from a vector range of 9.1 mm to one of 24.6 mm. For the patient group, Σ was 3.8, 6.6, and 3.5 mm; and σ was 3.6, 4.7 and 2.5 mm, in left-right, superior-inferior, and anterior-posterior directions, respectively. CONCLUSIONS: We found large systematic displacements of the fiducial markers relative to bony anatomy, in addition to wide distributions of displacement. These results for interfractional position variation confirm the potential benefit of using fiducial markers rather than bony anatomy for daily online position verification for pancreatic cancerpatients.
Authors: Wei Zhao; Liyue Shen; Bin Han; Yong Yang; Kai Cheng; Diego A S Toesca; Albert C Koong; Daniel T Chang; Lei Xing Journal: Int J Radiat Oncol Biol Phys Date: 2019-06-13 Impact factor: 7.038
Authors: Susana Marques; Miguel Bispo; Sílvia Leite; Teresa Moreira; Ana Caldeira; Pedro Moutinho-Ribeiro; Nuno Nunes Journal: GE Port J Gastroenterol Date: 2020-07-28
Authors: Oliver J Gurney-Champion; Dualta McQuaid; Alex Dunlop; Kee H Wong; Liam C Welsh; Angela M Riddell; Dow-Mu Koh; Uwe Oelfke; Martin O Leach; Christopher M Nutting; Shreerang A Bhide; Kevin J Harrington; Rafal Panek; Kate L Newbold Journal: Int J Radiat Oncol Biol Phys Date: 2017-10-16 Impact factor: 7.038
Authors: Eva Versteijne; Eelco Lens; Astrid van der Horst; Arjan Bel; Jorrit Visser; Cornelis J A Punt; Mustafa Suker; Casper H J van Eijck; Geertjan van Tienhoven Journal: Strahlenther Onkol Date: 2017-06-12 Impact factor: 3.621