Detection of Esophageal Fiducial Marker Displacement During Radiation Therapy With a 2-dimensional On-board Imager: Analysis of Internal Margin for Esophageal Cancer

• Published in: International journal of radiation oncology, biology, physics Vol. 85; no. 4; pp. 991 - 998
• Main Authors: Fukada, Junichi, MD, Hanada, Takashi, PhD, Kawaguchi, Osamu, MD, PhD, Ohashi, Toshio, MD, PhD, Takeuchi, Hiroya, MD, PhD, Kitagawa, Yuko, MD, PhD, Seki, Satoshi, MD, PhD, Shiraishi, Yutaka, MD, Ogata, Haruhiko, MD, PhD, Shigematsu, Naoyuki, MD, PhD
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.03.2013
• Subjects: Aged; Aged, 80 and over; Anatomic Landmarks - diagnostic imaging; Dose Fractionation; Esophageal Neoplasms - diagnostic imaging; Esophageal Neoplasms - pathology; Esophageal Neoplasms - radiotherapy; ESOPHAGUS; Esophagus - diagnostic imaging; Female; FIDUCIAL MARKERS; Fiducial Markers - statistics & numerical data; Hematology, Oncology and Palliative Medicine; Humans; IMAGE PROCESSING; Image Processing, Computer-Assisted - methods; Male; METALS; Middle Aged; Motion; NEOPLASMS; PATIENTS; Radiography; Radiology; RADIOLOGY AND NUCLEAR MEDICINE; RADIOTHERAPY; Radiotherapy Planning, Computer-Assisted - methods; Retrospective Studies; TWO-DIMENSIONAL CALCULATIONS; VERTEBRAE
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2012.07.2358

Purpose To quantify the interfraction displacement of esophageal fiducial markers for primary esophageal cancer radiation therapy. Methods and Materials Orthogonal 2-dimensional (2D) matching records fused to vertebrae were analyzed in clinically staged T1/2N0 esophageal cancer patients undergoing endoscopic clipping as fiducial metal markers. Displacement of the markers between the digitally reconstructed radiographs and on-board kilovoltage images during radiation therapy was analyzed according to direction and esophageal site. Results Forty-four patients, with 81 markers (10 proximal, 42 middle, and 29 distal), underwent 367 2D matching sessions during radiation therapy. The mean (SD) absolute marker displacement was 0.26 (0.30) cm in the right–left (RL), 0.50 (0.39) cm in the superior–inferior (SI), and 0.24 (0.21) cm in the anterior–posterior (AP) direction. Displacement was significantly larger in the SI than in the RL and AP directions ( P <.0001). In the SI direction, mean absolute displacements of the distal, middle, and proximal esophagus were 0.67 (0.45) cm, 0.42 (0.32) cm, and 0.36 (0.30) cm, respectively. Distal esophagus displacement was significantly larger than those of the middle and proximal esophagus ( P <.0001). The estimated internal margin to cover 95% of the cases was 0.75 cm in the RL and AP directions. In the SI direction, the margin was 1.25 cm for the proximal and middle esophagus and 1.75 cm for the distal esophagus. Conclusions The magnitude of interfraction displacement of esophageal clips was larger in the SI direction, particularly in the distal esophagus, but substantial displacement was observed in other directions and at other esophageal sites. It is practical to take estimated movements into account with internal margins, even if vertebrae-based 2D matching is performed.