Split-filter dual energy computed tomography radiotherapy: From calibration to image guidance

Edmund, Jens; Feen Rønjom, Marianne; van Overeem Felter, Mette; Maare, Christian; Margrete Juul Dam, Annica; Tsaggari, Eirini; Wohlfahrt, Patrick

doi:10.1016/j.phro.2023.100495

Cited by 5 publications

(2 citation statements)

References 36 publications

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“…Hence, an efficient handling of multiple datasets needs to be established for DECT workflows to optimally benefit from its variety and to ensure the correct use of images for each task at hand. This can be verified in an end-to-end test during commissioning [35] . Due to the many new possibilities offered by DECT, its clinical introduction will greatly benefit from knowledge-sharing, standardisation and guidance documents to ensure safe, smooth and efficient clinical procedures.…”

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confidence: 65%

From computed tomography innovation to routine clinical application in radiation oncology – A joint initiative of close collaboration

Taasti,

Wohlfahrt

2024

Physics and Imaging in Radiation Oncology

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mentioning

confidence: 65%

From computed tomography innovation to routine clinical application in radiation oncology – A joint initiative of close collaboration

Taasti,

Wohlfahrt

2024

Physics and Imaging in Radiation Oncology

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“…An equivalent low number using DECT with photon dose calculations has been reported. However, a workflow for the use of split filter DECT-based photon RT has been recently evaluated to be a feasible alternative to SECT-based photon RT, with possibilities for improved delineation accuracy [21] .…”

Section: Discussionmentioning

confidence: 99%

Survey on fan-beam computed tomography for radiotherapy: Imaging for dose calculation and delineation

Decabooter,

Hilgers,

De Rouck

et al. 2024

Physics and Imaging in Radiation Oncology

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First linac‐mounted photon counting detector for image guided radiotherapy: Planar image quality characterization

Hood,

Newall,

Butler

et al. 2024

Medical Physics

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BackgroundImage guided radiotherapy (IGRT) with cone‐beam computed tomography (CBCT) is limited by the sub‐optimal soft‐tissue contrast and spatial resolution of energy‐integrating flat panel detectors (FPDs) which produce quasi‐quantitative CT numbers. Spectral CT with high resolution photon‐counting detectors (PCDs) could improve tumor delineation by enhancing the soft‐tissue contrast, spatial resolution, dose‐efficiency, and CT number accuracy.PurposeThis study presents the first linac‐mounted PCD. On the journey to developing spectral cone‐beam CT for IGRT, the planar image quality of a linac‐mounted PCD is first fundamentally characterized and compared to an FPD in terms of the 2D spatial resolution, noise, and contrast.MethodsA Medipix3RX‐based PCD was mounted to the kV FPD of an x‐ray volume imaging (XVI) system on an Elekta linac and the PCD acquisition was synchronized with the pulsed kV source. The energy calibration of the Medipix3RX was determined with various radioisotope gamma emissions up to 60 keV. To compare the 2D spatial resolution and noise between the PCD and FPD, the pre‐sampling modulation transfer function (MTF) and normalized noise power spectrum (NPS) were measured using an RQA5 spectrum and a fluoroscopy phantom was imaged to determine the limiting resolution of line pairs. Spectral planar images of phantom inserts containing two different concentrations of calcium (60 and 240 mg/cc) and iodine (5 and 15 mg/cc) were optimally energy weighted to maximize the contrast using tube voltages of 60, 80, 100, and 120 kV. To account for drifts in the sensor temperature, the PCD was dynamically translated in and out of the insert shadow during acquisitions to obtain flat field corrections per frame. The raw contrast of the resultant planar images was compared to the energy‐integrating FPD.ResultsThe energy calibration of the Medipix3RX was observed to be linear up to 60 keV. The limiting resolution observed on the fluoroscopy phantom was 2 lp/mm for the FPD and 5 lp/mm for the PCD. The pre‐sampling MTF was higher across all frequencies comparing the PCD to the FPD. The normalized NPS of the PCD did not vary with frequency, whereas the spectrum for the FPD decreased monotonically and was lower than the PCD noise power across most of the spatial frequency range studied due to optical light spreading. Optimal energy weights were applied to the dynamically acquired PCD images and the raw contrast of the 60 mg/cc calcium insert increased by factors of and at 60 and 120 kV respectively compared to the FPD.ConclusionsA Medipix3RX‐based PCD was successfully integrated with the kilovoltage imaging system on an Elekta linac. The initial planar image quality characterization indicated improvements in the MTF and energy‐weighted contrast compared to the FPD. Future work will focus on obtaining linac‐mounted spectral CBCT images with a translate‐rotate geometry, however this initial study indicates that variations in the PCD sensor response during acquisitions must be addressed to realise the full potential of linac‐mounted spectral CBCT.

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Split-filter dual energy computed tomography radiotherapy: From calibration to image guidance

Cited by 5 publications

References 36 publications

From computed tomography innovation to routine clinical application in radiation oncology – A joint initiative of close collaboration

From computed tomography innovation to routine clinical application in radiation oncology – A joint initiative of close collaboration

Survey on fan-beam computed tomography for radiotherapy: Imaging for dose calculation and delineation

First linac‐mounted photon counting detector for image guided radiotherapy: Planar image quality characterization

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