Physical phantom studies of helical cone-beam CT with exact reconstruction

Jun Tan, H. Harold Li, Eric Klein, Hua Li, Parag Parikh, Deshan Yang

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Purpose: Onboard cone-beam computed tomography (CBCT) connected to radiotherapy linear accelerators suffers CT number consistency and uniformity problems in addition to limited longitudinal coverage. Such problems have prevented CBCT from being fully utilized in many quantitative applications including tumor response evaluation and daily radiation dose computation. This paper presents a feasibility study on the helical CBCT scan with exact reconstruction that could be a potential solution. Methods: A Varian TrueBeam treatment machine was programmed in the research mode to accomplish helical scans that required synchronized gantry circular rotation and couch table linear motion. Two physical phantoms were scanned in both 360° and 720° helical trajectories. A Katsevich exact reconstruction algorithm was implemented and tested with digital phantom simulations. It was further optimized to account for mechanical instabilities of both gantry rotation and couch table motion from the physical phantom measurements. Preprocessing was employed to correct photon scattering, beam hardening, and bowtie filtration. The reconstructed images were compared to those reconstructed from the FDK approximate reconstruction algorithm using the same phantom projections. Comparisons have also been made with the clinical circular CBCT images and the diagnostic helical CT images of the same physical phantoms. Results: Satisfactory reconstruction results were obtained for the Katsevich algorithm in digital phantom study. Physical phantom results demonstrated that a 360° helical scan could provide up to 19 cm longitudinal coverage, which could be increased to 54 cm with a 720° helical scan. Image spatial resolution and soft tissue contrast were sufficient. The Q-value, which combined the spatial frequency response (modulation transfer function) and the image noise, was calculated, and suggested that the Katsevich algorithm was superior to the FDK algorithm. Conclusions: A helical CBCT scan is useful to extend the longitudinal coverage. The Katsevich exact reconstruction algorithm could provide additional advantages in image qualities over the traditional FDK approximate algorithm. The combination of helical CBCT scan with exact reconstruction was proved feasible and would render CBCT more useful in image-guided radiation therapy.

Original languageEnglish (US)
Pages (from-to)4695-4704
Number of pages10
JournalMedical Physics
Volume39
Issue number8
DOIs
StatePublished - Jan 1 2012

Fingerprint

Spiral Cone-Beam Computed Tomography
Cone-Beam Computed Tomography
Image-Guided Radiotherapy
Particle Accelerators
Spiral Computed Tomography
Feasibility Studies
Photons
Radiotherapy
Radiation

Keywords

  • CBCT
  • cone-beam computed tomography
  • CT reconstruction
  • IGRT

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

Cite this

Tan, J., Li, H. H., Klein, E., Li, H., Parikh, P., & Yang, D. (2012). Physical phantom studies of helical cone-beam CT with exact reconstruction. Medical Physics, 39(8), 4695-4704. https://doi.org/10.1118/1.4736535

Physical phantom studies of helical cone-beam CT with exact reconstruction. / Tan, Jun; Li, H. Harold; Klein, Eric; Li, Hua; Parikh, Parag; Yang, Deshan.

In: Medical Physics, Vol. 39, No. 8, 01.01.2012, p. 4695-4704.

Research output: Contribution to journalArticle

Tan, J, Li, HH, Klein, E, Li, H, Parikh, P & Yang, D 2012, 'Physical phantom studies of helical cone-beam CT with exact reconstruction', Medical Physics, vol. 39, no. 8, pp. 4695-4704. https://doi.org/10.1118/1.4736535
Tan, Jun ; Li, H. Harold ; Klein, Eric ; Li, Hua ; Parikh, Parag ; Yang, Deshan. / Physical phantom studies of helical cone-beam CT with exact reconstruction. In: Medical Physics. 2012 ; Vol. 39, No. 8. pp. 4695-4704.
@article{11b8948d2631431fbaa6508cf562da5f,
title = "Physical phantom studies of helical cone-beam CT with exact reconstruction",
abstract = "Purpose: Onboard cone-beam computed tomography (CBCT) connected to radiotherapy linear accelerators suffers CT number consistency and uniformity problems in addition to limited longitudinal coverage. Such problems have prevented CBCT from being fully utilized in many quantitative applications including tumor response evaluation and daily radiation dose computation. This paper presents a feasibility study on the helical CBCT scan with exact reconstruction that could be a potential solution. Methods: A Varian TrueBeam treatment machine was programmed in the research mode to accomplish helical scans that required synchronized gantry circular rotation and couch table linear motion. Two physical phantoms were scanned in both 360° and 720° helical trajectories. A Katsevich exact reconstruction algorithm was implemented and tested with digital phantom simulations. It was further optimized to account for mechanical instabilities of both gantry rotation and couch table motion from the physical phantom measurements. Preprocessing was employed to correct photon scattering, beam hardening, and bowtie filtration. The reconstructed images were compared to those reconstructed from the FDK approximate reconstruction algorithm using the same phantom projections. Comparisons have also been made with the clinical circular CBCT images and the diagnostic helical CT images of the same physical phantoms. Results: Satisfactory reconstruction results were obtained for the Katsevich algorithm in digital phantom study. Physical phantom results demonstrated that a 360° helical scan could provide up to 19 cm longitudinal coverage, which could be increased to 54 cm with a 720° helical scan. Image spatial resolution and soft tissue contrast were sufficient. The Q-value, which combined the spatial frequency response (modulation transfer function) and the image noise, was calculated, and suggested that the Katsevich algorithm was superior to the FDK algorithm. Conclusions: A helical CBCT scan is useful to extend the longitudinal coverage. The Katsevich exact reconstruction algorithm could provide additional advantages in image qualities over the traditional FDK approximate algorithm. The combination of helical CBCT scan with exact reconstruction was proved feasible and would render CBCT more useful in image-guided radiation therapy.",
keywords = "CBCT, cone-beam computed tomography, CT reconstruction, IGRT",
author = "Jun Tan and Li, {H. Harold} and Eric Klein and Hua Li and Parag Parikh and Deshan Yang",
year = "2012",
month = "1",
day = "1",
doi = "10.1118/1.4736535",
language = "English (US)",
volume = "39",
pages = "4695--4704",
journal = "Medical Physics",
issn = "0094-2405",
publisher = "AAPM - American Association of Physicists in Medicine",
number = "8",

}

TY - JOUR

T1 - Physical phantom studies of helical cone-beam CT with exact reconstruction

AU - Tan, Jun

AU - Li, H. Harold

AU - Klein, Eric

AU - Li, Hua

AU - Parikh, Parag

AU - Yang, Deshan

PY - 2012/1/1

Y1 - 2012/1/1

N2 - Purpose: Onboard cone-beam computed tomography (CBCT) connected to radiotherapy linear accelerators suffers CT number consistency and uniformity problems in addition to limited longitudinal coverage. Such problems have prevented CBCT from being fully utilized in many quantitative applications including tumor response evaluation and daily radiation dose computation. This paper presents a feasibility study on the helical CBCT scan with exact reconstruction that could be a potential solution. Methods: A Varian TrueBeam treatment machine was programmed in the research mode to accomplish helical scans that required synchronized gantry circular rotation and couch table linear motion. Two physical phantoms were scanned in both 360° and 720° helical trajectories. A Katsevich exact reconstruction algorithm was implemented and tested with digital phantom simulations. It was further optimized to account for mechanical instabilities of both gantry rotation and couch table motion from the physical phantom measurements. Preprocessing was employed to correct photon scattering, beam hardening, and bowtie filtration. The reconstructed images were compared to those reconstructed from the FDK approximate reconstruction algorithm using the same phantom projections. Comparisons have also been made with the clinical circular CBCT images and the diagnostic helical CT images of the same physical phantoms. Results: Satisfactory reconstruction results were obtained for the Katsevich algorithm in digital phantom study. Physical phantom results demonstrated that a 360° helical scan could provide up to 19 cm longitudinal coverage, which could be increased to 54 cm with a 720° helical scan. Image spatial resolution and soft tissue contrast were sufficient. The Q-value, which combined the spatial frequency response (modulation transfer function) and the image noise, was calculated, and suggested that the Katsevich algorithm was superior to the FDK algorithm. Conclusions: A helical CBCT scan is useful to extend the longitudinal coverage. The Katsevich exact reconstruction algorithm could provide additional advantages in image qualities over the traditional FDK approximate algorithm. The combination of helical CBCT scan with exact reconstruction was proved feasible and would render CBCT more useful in image-guided radiation therapy.

AB - Purpose: Onboard cone-beam computed tomography (CBCT) connected to radiotherapy linear accelerators suffers CT number consistency and uniformity problems in addition to limited longitudinal coverage. Such problems have prevented CBCT from being fully utilized in many quantitative applications including tumor response evaluation and daily radiation dose computation. This paper presents a feasibility study on the helical CBCT scan with exact reconstruction that could be a potential solution. Methods: A Varian TrueBeam treatment machine was programmed in the research mode to accomplish helical scans that required synchronized gantry circular rotation and couch table linear motion. Two physical phantoms were scanned in both 360° and 720° helical trajectories. A Katsevich exact reconstruction algorithm was implemented and tested with digital phantom simulations. It was further optimized to account for mechanical instabilities of both gantry rotation and couch table motion from the physical phantom measurements. Preprocessing was employed to correct photon scattering, beam hardening, and bowtie filtration. The reconstructed images were compared to those reconstructed from the FDK approximate reconstruction algorithm using the same phantom projections. Comparisons have also been made with the clinical circular CBCT images and the diagnostic helical CT images of the same physical phantoms. Results: Satisfactory reconstruction results were obtained for the Katsevich algorithm in digital phantom study. Physical phantom results demonstrated that a 360° helical scan could provide up to 19 cm longitudinal coverage, which could be increased to 54 cm with a 720° helical scan. Image spatial resolution and soft tissue contrast were sufficient. The Q-value, which combined the spatial frequency response (modulation transfer function) and the image noise, was calculated, and suggested that the Katsevich algorithm was superior to the FDK algorithm. Conclusions: A helical CBCT scan is useful to extend the longitudinal coverage. The Katsevich exact reconstruction algorithm could provide additional advantages in image qualities over the traditional FDK approximate algorithm. The combination of helical CBCT scan with exact reconstruction was proved feasible and would render CBCT more useful in image-guided radiation therapy.

KW - CBCT

KW - cone-beam computed tomography

KW - CT reconstruction

KW - IGRT

UR - http://www.scopus.com/inward/record.url?scp=84864645857&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84864645857&partnerID=8YFLogxK

U2 - 10.1118/1.4736535

DO - 10.1118/1.4736535

M3 - Article

C2 - 22894394

AN - SCOPUS:84864645857

VL - 39

SP - 4695

EP - 4704

JO - Medical Physics

JF - Medical Physics

SN - 0094-2405

IS - 8

ER -