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Borsavage JM, Cherpak AJ, Robar JL. Improving image quality and reducing dose with 2.5 MV diamond target volume-of-interest cone beam CT imaging. Med Phys 2022; 49:7661-7671. [PMID: 36106659 DOI: 10.1002/mp.15974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 08/08/2022] [Accepted: 08/19/2022] [Indexed: 12/27/2022] Open
Abstract
PURPOSE Over the past decades, continuous efforts have been made to improve megavoltage (MV) image quality versus dose characteristics, including the implementation of low atomic number (Z) targets in MV beamlines and the development of more efficient detectors. Recently, a diamond target beam within a commercial radiotherapy treatment platform demonstrated improved planar contrast-to-noise-ratio (CNR) per unit dose using a novel 2.5 MV sintered diamond target beam, which enabled image acquisition on the order of mGy. The present work assesses cone beam CT (CBCT) image quality characteristics for the novel 2.5 MV diamond target beam and the effects of volume-of-interest (VOI) collimation on the image quality and imaging dose distribution. METHODS A sintered diamond target was incorporated into the target arm of the linear accelerator, replacing the 2.5 MV commercial copper imaging target. CBCT image quality was evaluated against the commercial imaging beam with regard to spatial resolution and CNR versus dose. In addition to full-field acquisitions, we investigated VOI techniques that collimate the imaging beam to preselected anatomy, to determine potential image quality improvements and dose sparing capacity. Using an anthropomorphic phantom, VOI regions were defined to encompass the maxillary and ethmoid sinuses and ranged in dimension from 3 cm to 4.85 cm equivalent radius. The MLC was fit to each VOI structure throughout a full CBCT arc and the corresponding MLC sequences were produced as XML scripts for acquisition. Calibrated radiochromic film was used in phantom to measure cumulative axial dose distributions during each CBCT acquisition. RESULTS In full-field CBCT, the 2.5 MV diamond target beam demonstrated improved CNR versus dose compared to the commercial imaging beam, by factors of up to 1.7. The calculated modulation transfer function (MTF) displayed an increase of nearly 30% in f50 for the 2.5 MV diamond target beam compared to the commercial beam. Using VOI techniques, CNR increased monotonically as a function of equivalent radius at the bone-tissue interface. At the bone-sinus interface, the CNR for the full-field case was slightly decreased compared to the largest VOI case. Imaging dose in the anteroposterior direction increased with increasing VOI equivalent radius. CONCLUSION The novel 2.5 MV sintered diamond target beam presents a simple modification to the commercial imaging beam which provides improved image quality in full-field CBCT and the potential for simultaneous dose sparing and CNR improvement at high-contrast interfaces using VOI acquisition techniques.
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Affiliation(s)
- Jennifer M Borsavage
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Amanda J Cherpak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Medical Physics, Nova Scotia Health Authority, Halifax, Nova Scotia, Canada
| | - James L Robar
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Medical Physics, Nova Scotia Health Authority, Halifax, Nova Scotia, Canada
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Borsavage JM, Cherpak A, Robar JL. Investigation of planar image quality for a novel 2.5 MV diamond target beam from a radiotherapy linear accelerator. PHYSICS & IMAGING IN RADIATION ONCOLOGY 2021; 16:103-108. [PMID: 33458352 PMCID: PMC7807593 DOI: 10.1016/j.phro.2020.10.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 10/09/2020] [Accepted: 10/14/2020] [Indexed: 12/05/2022]
Abstract
Background and purpose A commercial 2.5 MV beam has been clinically available for beam’s-eye-view imaging in radiotherapy, offering improved contrast-to-noise ratio (CNR) compared to therapeutic beams, due to the softer spectrum. Previous research suggested that imaging performance could be improved using a low-Z diamond target to reduce the self-absorption of diagnostic energy photons. The aim of this study was to 1) investigate the feasibility of two 2.5 MV diamond target beamline configurations and 2) characterize the dosimetry and planar image quality of these novel low-Z beams. Materials and methods The commercial 2.5 MV beam was modified by replacing the copper target with sintered diamond. Two beamlines were investigated: a carousel-mounted diamond target beamline and a ‘conventional’ beamline, with the diamond target in the target arm. Planar image quality was assessed in terms of spatial resolution and CNR. Results Due to image artifacts, image quality could not be assessed for the carousel-mounted low-Z target beam. The ‘conventional’ 2.5 MV low-Z beam quality was softer by 2.7% compared to the commercial imaging beam, resulting in improved CNR by factors of up to 1.3 and 1.7 in thin and thick phantoms, respectively. In regard to spatial resolution, the ‘conventional’ 2.5 MV low-Z beam slightly outperformed the commercial imaging beam. Conclusion With a simple modification to the 2.5 MV commercial beamline, we produced an improved energy spectrum for imaging. This 2.5 MV diamond target beam proved to be an advantageous alternative to the commercial target configuration, offering both superior resolution and CNR.
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Affiliation(s)
- Jennifer M Borsavage
- Dalhousie University, Department of Physics and Atmospheric Science, 5820 University Ave., Halifax, Nova Scotia B3H 1V7, Canada
| | - Amanda Cherpak
- Dalhousie University, Department of Physics and Atmospheric Science, 5820 University Ave., Halifax, Nova Scotia B3H 1V7, Canada.,Dalhousie University, Department of Radiation Oncology, 5820 University Ave., Halifax, Nova Scotia B3H 1V7, Canada.,Nova Scotia Health Authority, Department of Medical Physics, Halifax, Canada
| | - James L Robar
- Dalhousie University, Department of Physics and Atmospheric Science, 5820 University Ave., Halifax, Nova Scotia B3H 1V7, Canada.,Dalhousie University, Department of Radiation Oncology, 5820 University Ave., Halifax, Nova Scotia B3H 1V7, Canada.,Nova Scotia Health Authority, Department of Medical Physics, Halifax, Canada
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Reshef A, Riddell C, Trousset Y, Ladjal S, Bloch I. Dual-rotation C-arm cone-beam computed tomography to increase low-contrast detection. Med Phys 2017; 44:e164-e173. [PMID: 28901617 DOI: 10.1002/mp.12247] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 02/17/2017] [Accepted: 03/23/2017] [Indexed: 11/09/2022] Open
Abstract
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® 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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Affiliation(s)
- Aymeric Reshef
- LTCI, Télécom ParisTech, Université Paris-Saclay, 75013, Paris, France.,GE Healthcare, Buc, France
| | | | | | - Saïd Ladjal
- LTCI, Télécom ParisTech, Université Paris-Saclay, 75013, Paris, France
| | - Isabelle Bloch
- LTCI, Télécom ParisTech, Université Paris-Saclay, 75013, Paris, France
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Berbeco RI, Detappe A, Tsiamas P, Parsons D, Yewondwossen M, Robar J. Low Z target switching to increase tumor endothelial cell dose enhancement during gold nanoparticle-aided radiation therapy. Med Phys 2016; 43:436. [PMID: 26745936 DOI: 10.1118/1.4938410] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
PURPOSE Previous studies have introduced gold nanoparticles as vascular-disrupting agents during radiation therapy. Crucial to this concept is the low energy photon content of the therapy radiation beam. The authors introduce a new mode of delivery including a linear accelerator target that can toggle between low Z and high Z targets during beam delivery. In this study, the authors examine the potential increase in tumor blood vessel endothelial cell radiation dose enhancement with the low Z target. METHODS The authors use Monte Carlo methods to simulate delivery of three different clinical photon beams: (1) a 6 MV standard (Cu/W) beam, (2) a 6 MV flattening filter free (Cu/W), and (3) a 6 MV (carbon) beam. The photon energy spectra for each scenario are generated for depths in tissue-equivalent material: 2, 10, and 20 cm. The endothelial dose enhancement for each target and depth is calculated using a previously published analytic method. RESULTS It is found that the carbon target increases the proportion of low energy (<150 keV) photons at 10 cm depth to 28% from 8% for the 6 MV standard (Cu/W) beam. This nearly quadrupling of the low energy photon content incident on a gold nanoparticle results in 7.7 times the endothelial dose enhancement as a 6 MV standard (Cu/W) beam at this depth. Increased surface dose from the low Z target can be mitigated by well-spaced beam arrangements. CONCLUSIONS By using the fast-switching target, one can modulate the photon beam during delivery, producing a customized photon energy spectrum for each specific situation.
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Affiliation(s)
- Ross I Berbeco
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115
| | - Alexandre Detappe
- Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115
| | - Panogiotis Tsiamas
- Department of Radiation Oncology, St. Jude Children's Hospital, Memphis, Tennessee 38105
| | - David Parsons
- Department of Radiation Oncology and Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 1V7, Canada
| | - Mammo Yewondwossen
- Department of Radiation Oncology and Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 1V7, Canada
| | - James Robar
- Department of Radiation Oncology and Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 1V7, Canada
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Parsons D, Robar JL. Volume of interest CBCT and tube current modulation for image guidance using dynamic kV collimation. Med Phys 2016; 43:1808. [DOI: 10.1118/1.4943799] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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Parsons D, Robar JL. An investigation of kV CBCT image quality and dose reduction for volume-of-interest imaging using dynamic collimation. Med Phys 2015; 42:5258-69. [DOI: 10.1118/1.4928474] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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Wikner J, Hanken H, Eulenburg C, Heiland M, Gröbe A, Assaf AT, Riecke B, Friedrich RE. Linear accuracy and reliability of volume data sets acquired by two CBCT-devices and an MSCT using virtual models: a comparative in-vitro study. Acta Odontol Scand 2015; 74:51-9. [PMID: 25936361 DOI: 10.3109/00016357.2015.1040064] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
OBJECTIVE To discriminate clinically relevant aberrance, the accuracy of linear measurements in three-dimensional (3D) reconstructed datasets was investigated. MATERIALS AND METHODS Three partly edentulous human skulls were examined. Landmarks were defined prior to acquisition. Two CBCT-scanners and a Quad-slice CT-scanner were used. Actual distances were physically measured with calipers and defined as a reference. Subsequently, from digital DICOM datasets, 3D virtual models were generated using maximum intensity projections (MIPs). Linear measurements were performed by semi-automated image analysis. Virtual and analogue linear measurements were compared using repeated measurements in a mixed model (p ≤ 0.05). RESULTS No significant difference was found among all of the digital measurements when compared to one another, whereas a significant difference was found in matched-pairs analysis between CBCT and calipers (p = 0.032). All digitally acquired data resulted in lower mean values compared to the measurements via calipers. A high level of inter-observer reliability was obtained in the digital measurements (inter-rater correlation = 0.988-0.993). CONCLUSIONS The reconstructed datasets led to highly consistent values among linear measurements. Yielding sub-millimeter precision, these modalities are assumed to reflect reality in a clinically irrelevant altered manner. During data acquisition and evaluation, a maximum of precision must be achieved.
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Affiliation(s)
- Johannes Wikner
- a 1 Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg Eppendorf , Hamburg, Germany
| | - Henning Hanken
- a 1 Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg Eppendorf , Hamburg, Germany
| | - Christine Eulenburg
- b 2 Medical Biometry and Epidemiology, University Medical Center Hamburg Eppendorf , Hamburg, Germany
| | - Max Heiland
- a 1 Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg Eppendorf , Hamburg, Germany
| | - Alexander Gröbe
- a 1 Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg Eppendorf , Hamburg, Germany
| | - Alexandre Thomas Assaf
- a 1 Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg Eppendorf , Hamburg, Germany
| | - Björn Riecke
- a 1 Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg Eppendorf , Hamburg, Germany
| | - Reinhard E Friedrich
- a 1 Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg Eppendorf , Hamburg, Germany
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