Image-guided radiotherapy using a mobile kilovoltage x-ray device

Stephen P. Sorensen, Phillip E. Chow, Sergey Kriminski, Paul M. Medin, Timothy D. Solberg

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

A mobile isocentric C-arm kilovoltage imager has been evaluated as a potential tool for image-guided radiotherapy. The C-arm is equipped with an amorphous silicon flat panel for high-quality image acquisition. Additionally, the device is capable of cone beam computed tomography (CT) and volumetric reconstruction. This is achieved through the application of a modified Feldkamp algorithm with acquisition over a 180° scan arc. The number of projections can be varied from 100 to 1000, resulting in a reconstructed volume 20 cm in diameter by 15-cm long. While acquisition time depends upon number of projections, acceptable quality images can be obtained in less than 60 seconds. Image resolution and contrast of cone-beam phantom images have been compared with images from a conventional CT scanner. The system has a spatial resolution of < 10 lp/cm and resolution is approximately equal in all 3 dimensions. Conversely, subject contrast is poorer than conventional CT, compromised by the increased scatter and underlying noise inherent in cone beam reconstruction, as well as the absence of filtering prior to reconstruction. The mobility of the C-arm makes it necessary to determine the C-arm position relative to the linear accelerator isocenter. Two solutions have been investigated: (1) the use of fiducial markers, embedded in the linac couch, that can subsequently be registered in the image sets; and (2), a navigation approach for infrared tracking of the C-arm relative to the linac isocenter. Observed accuracy in phantom positioning ranged from 1.0 to 1.5 mm using the navigation approach and 1.5 to 2.5 mm using the fiducial-based approach. As part of this work, the impact of respiratory motion on cone-beam image quality was evaluated, and a scheme for retrospective gating was devised. Results demonstrated that kilovoltage cone beam CT provides spatial integrity and resolution comparable to conventional CT. Cone-beam CT studies of patients undergoing radiotherapy have demonstrated acceptable soft tissue contrast, allowing assessment of daily changes in target anatomy. Of the 2 approaches developed to register images to the linac isocenter, the navigation method demonstrated superior accuracy for daily patient positioning relative to the fiducial-based method. Finally, significant image degradation due to respiratory motion was observed. It was demonstrated that this could be improved by correlating the acquisition of individual 2D projections with respiration for retrospective reconstruction of phase-based volumetric datasets.

Original languageEnglish (US)
Pages (from-to)40-50
Number of pages11
JournalMedical Dosimetry
Volume31
Issue number1
DOIs
StatePublished - Mar 2006

Fingerprint

Image-Guided Radiotherapy
Cone-Beam Computed Tomography
radiation therapy
X-Rays
Equipment and Supplies
cones
tomography
Tomography
Fiducial Markers
X-Ray Computed Tomography Scanners
Patient Positioning
Particle Accelerators
x rays
acquisition
Silicon
navigation
Noise
Anatomy
Respiration
Radiotherapy

Keywords

  • C-Arm
  • Cone beam CT
  • Flat panel
  • Image-guided radiation therapy

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Health Professions(all)
  • Radiation

Cite this

Image-guided radiotherapy using a mobile kilovoltage x-ray device. / Sorensen, Stephen P.; Chow, Phillip E.; Kriminski, Sergey; Medin, Paul M.; Solberg, Timothy D.

In: Medical Dosimetry, Vol. 31, No. 1, 03.2006, p. 40-50.

Research output: Contribution to journalArticle

Sorensen, Stephen P. ; Chow, Phillip E. ; Kriminski, Sergey ; Medin, Paul M. ; Solberg, Timothy D. / Image-guided radiotherapy using a mobile kilovoltage x-ray device. In: Medical Dosimetry. 2006 ; Vol. 31, No. 1. pp. 40-50.
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