Effects of image lag on real-time target tracking in radiotherapy

R. Tanaka, K. Ichikawa, S. Mori, S. Dobashi, M. Kumagaya, H. Kawashima, S. Morita, S. Sanada

Research output: Chapter in Book/Report/Conference proceedingConference contribution


There is a concern that image lag may reduce accuracy of real-time target tracking in radiotherapy. This study was performed to investigate influence of image lag on the accuracy of target tracking in radiotherapy. Fluoroscopic image: were obtained using a direct type of dynamic flat-panel detector (FPD) system under conditions of target tracking during radiotherapy. The images continued to be read out after X-irradiations and cutoff, and image lag properties in the system were then determined. Subsequently, a tungsten materials plate with a precision edge was mounted on to a motor control device, which provided a constant velocity. The plate was moved into the center of the detector at movement rate of 1 and 20 mm/s, covering lung tumor movement of normal breathing, and MTF and profile curves were measured on the edges covering and uncovering the detector. A lung tumor with blurred edge due to image lag was simulated using the results and then superimposed on breathing chest radiographs of a patient. The moving target with and without image lag was traced using a template-matching technique. In the results, the target could be traced within a margin for error ii external radiotherapy. The results indicated that there was no effect of image lag on target tracking in usual breathing speed in a radiotherapy situation. Further studies are required to investigate influence by the other factors, such a: exposure dose, target size and shape, imaging rate, and thickness of a patient's body.

Original languageEnglish
Title of host publicationMedical Imaging 2010
Subtitle of host publicationPhysics of Medical Imaging
EditionPART 3
Publication statusPublished - 2010
Externally publishedYes
EventMedical Imaging 2010: Physics of Medical Imaging - San Diego, CA, United States
Duration: 2010 Feb 152010 Feb 18

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
NumberPART 3
ISSN (Print)1605-7422


OtherMedical Imaging 2010: Physics of Medical Imaging
Country/TerritoryUnited States
CitySan Diego, CA


  • Flat panel detector
  • Image lag
  • Radiotherapy
  • Target tracking

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging


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