Investigation on effect of image lag in fluoroscopic images obtained with a dynamic flat-panel detector (FPD) on accuracy of target tracking in radiotherapy

Rie Tanaka, Katsuhiro Ichikawa, Shinichiro Mori, Suguru Dobashi, Motoki Kumagai, Hiroki Kawashima, Shinichi Minohara, Sigeru Sanada

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

Real-time tumor tracking in external radiotherapy can be achieved by diagnostic (kV) X-ray imaging with a dynamic flat-panel detector (FPD). The purpose of this study was to address image lag in target tracking and its influence on the accuracy of tumor tracking. Fluoroscopic images were obtained using a direct type of dynamic FPD. Image lag properties were measured without test devices according to IEC 62220-1. Modulation transfer function (MTF) and profile curves were measured on the edges of a moving tungsten plate at movement rate of 10 and 20 mm/s, covering lung tumor movement of normal breathing. A lung tumor and metal sphere 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 image lag for the first frame after X-ray cutoff was 2.0% and decreased to less than 0.1% in the fifth frame. In the measurement of profile curves on the edges of static and moving tungsten material plates, the effect of image lag was seen as blurred edges of the plate. The blurred edges of a moving target were indicated as reduction of MTF. However, the target could be traced within an error of ± 5 mm. The results indicated that there was no effect of image lag on target tracking in usual breathing speed in a radiotherapy situation.

Original languageEnglish
Pages (from-to)723-731
Number of pages9
JournalJournal of radiation research
Volume51
Issue number6
DOIs
Publication statusPublished - 2010 Nov
Externally publishedYes

Keywords

  • Flat-panel detector (FPD)
  • Fluoroscopic image
  • Image lag
  • Radiotherapy
  • Target tracking

ASJC Scopus subject areas

  • Radiation
  • Radiology Nuclear Medicine and imaging
  • Health, Toxicology and Mutagenesis

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