An investigation of kV CBCT image quality and dose reduction for volume‐of‐interest imaging using dynamic collimation

Parsons, David; Robar, James L.

doi:10.1118/1.4928474

Cited by 17 publications

(26 citation statements)

References 27 publications

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“…Parsons and Robar [28, 29] have developed an innovative iris-type dynamic collimator for ROI imaging in IGRT. At present they have utilized it for true conformal imaging, in which they only attempt to recover an accurate image of the specified volume-of-interest (VOI).…”

Section: Discussionmentioning

confidence: 99%

“…As such, it does not provide as much information of the surrounding anatomy as the dIWROI method presented here. The blades of the iris collimator described in [28] are copper with a thickness of 6.4 mm, twice the thickness we used; thus they will have a nonzero, though small (roughly 0.2%) transmission. In principle there is no reason the iris collimator cannot be used for IWROI imaging, although its relatively complicated blade structure would make edge matching as described above for the I 0 correction quite challenging.…”

Section: Discussionmentioning

confidence: 99%

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Dynamic intensity-weighted region of interest imaging for conebeam CT

Pearson

Pan

Pelizzari

2016

XST

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BACKGROUND Patient dose from image guidance in radiotherapy is small compared to the treatment dose. However, the imaging beam is untargeted and deposits dose equally in tumor and healthy tissues. It is desirable to minimize imaging dose while maintaining efficacy. OBJECTIVE Image guidance typically does not require full image quality throughout the patient. Dynamic filtration of the kV beam allows local control of CT image noise for high quality around the target volume and lower quality elsewhere, with substantial dose sparing and reduced scatter fluence on the detector. METHODS The dynamic Intensity-Weighted Region of Interest (dIWROI) technique spatially varies beam intensity during acquisition with copper filter collimation. Fluence is reduced by 95% under the filters with the aperture conformed dynamically to the ROI during cone-beam CT scanning. Preprocessing to account for physical effects of the collimator before reconstruction is described. RESULTS Reconstructions show image quality comparable to a standard scan in the ROI, with higher noise and streak artifacts in the outer region but still adequate quality for patient localization. Monte Carlo modeling shows dose reduction by 10–15% in the ROI due to reduced scatter, and up to 75% outside. CONCLUSIONS The presented technique offers a method to reduce imaging dose by accepting increased image noise outside the ROI, while maintaining full image quality inside the ROI.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Dynamic intensity-weighted region of interest imaging for conebeam CT

Pearson

Pan

Pelizzari

2016

XST

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“…The CBCT projections were reconstructed using the FDK algorithm 6 within iTools (Varian Medical Systems, iLab GmbH, Baden, Switzerland). The preprocessing steps were simplified from previous VOI CBCT methods 4 to account for the truncation artifacts associated when reconstructing VOI projections. Prior to reconstruction, the VOI projection is masked using the a priori blade locations, eroded, the boundary of the VOI extrapolated and normalized.…”

Section: B Volume Of Interest Cbct Imagingmentioning

confidence: 99%

“…Volume of interest (VOI) CBCT offers improved image quality and dose reduction compared to full-field CBCT through reduction of scatter generation within the patient. [1][2][3][4] Chen et al 2 and Lai et al 3 have shown using a static copper collimator, scatter reductions of a factor of 6.6, compared to fullfield CBCT, for example. This resulted in a contrast-to-noise ratio (CNR) improvement of a factor of approximately 1.45, with dose reductions by a factor of 1.2 and 2.7 inside and outside the VOI, respectively, compared to full-field CBCT.…”

Section: Introductionmentioning

confidence: 99%

Volume of interest CBCT and tube current modulation for image guidance using dynamic kV collimation

Parsons

Robar

2016

Medical Physics

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“…Interestingly, C‐arm CBCT is often used for volume‐of‐interest (VOI) imaging, with limited contrast detection due to truncation artifacts. Building upon the concept of the bow‐tie filter, several beam modulators have been proposed to concentrate the exposure over the VOI while avoiding truncation artifacts . Beam modulators for VOI imaging are again invasive and costly to integrate, lacking flexibility since they only define a fixed aperture.…”

Section: Introductionmentioning

confidence: 99%

Dual‐rotation C‐arm cone‐beam computed tomography to increase low‐contrast detection

Reshef

Riddell²,

Trousset³

et al. 2017

Medical Physics

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Purpose: This paper investigates the capabilities of a dual-rotation C-arm cone-beam computed tomography (CBCT) framework to improve non-contrast-enhanced low-contrast detection for full volume or volume-of-interest (VOI) brain imaging. Method: The idea is to associate two C-arm short-scan rotational acquisitions (spins): one over the full detector field of view (FOV) at low dose, and one collimated to deliver a higher dose to the central densest parts of the head. The angular sampling performed by each spin is allowed to vary in terms of number of views and angular positions. Collimated data is truncated and does not contain measurement of the incoming X-ray intensities in air (air calibration). When targeting full volume reconstruction, the method is intended to act as a virtual bow-tie. When targeting VOI imaging, the method is intended to provide the minimum full detector FOV data that sufficiently corrects for truncation artifacts. A single dedicated iterative algorithm is described that handles all proposed sampling configurations despite truncation and absence of air calibration. Results: Full volume reconstruction of dual-rotation simulations and phantom acquisitions are shown to have increased low-contrast detection for less dose, with respect to a single-rotation acquisition. High CNR values were obtained on 1% inserts of the Catphan r 515 module in 0.94 mm thick slices. Image quality for VOI imaging was preserved from truncation artifacts even with less than 10 non-truncated views, without using the sparsity a priori common to such context. Conclusion: A flexible dual-rotation acquisition and reconstruction framework is proposed that has the potential to improve low-contrast detection in clinical C-arm brain soft-tissue imaging.

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An investigation of kV CBCT image quality and dose reduction for volume‐of‐interest imaging using dynamic collimation

Abstract: The presented VOI technique offers improved image quality for image-guided radiotherapy while sparing the surrounding volume of unnecessary dose compared to full-field techniques.

Cited by 17 publications

References 27 publications

Dynamic intensity-weighted region of interest imaging for conebeam CT

Dynamic intensity-weighted region of interest imaging for conebeam CT

Volume of interest CBCT and tube current modulation for image guidance using dynamic kV collimation

Dual‐rotation C‐arm cone‐beam computed tomography to increase low‐contrast detection

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