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Title: SU-F-J-212: Enabling Conventional Cone Beam CT with the Capability of Dual Energy Imaging Using a Simple Add-On Beam Modifier

Abstract

Purpose: In searching for a robust, efficient and cost-effective dual energy cone beam CT (DECBCT) solution for various radiation oncology applications, in particularly for improved proton dose planning/replanning accuracy and DE-CBCT guided radiation therapy, we investigate a novel energy modulation scheme using a beam modifier placed between the source and patient and optimize its geometric configuration for routine clinical use. Methods: The study was performed using a Hitachi CBCT scanner and the tube voltage was set at 125 kVp. The higher energy beam was obtained by filtering the incident utilizing a beam modulation layer (material: copper, thickness: 1.8 mm). To avoid the need for double scans (one with and one without the energy modulator), the modulation layer was configured to cover only the half of the X-ray beam so that two sets of sinograms corresponding low and high energies were collected after a single gantry rotation of 360 deg. The average high energy and low energy HU numbers (HUhigh and HUlow) were derived for pixels in a defined region-of-interest, respectively. Results: The beam modifier increased the threshold of the energy spectrum from ∼20 keV up to ∼50 keV. Two complete sets of images were obtained with good alignment between themore » high energy and low-energy cases without any artifact observed (Fig. 2). The HUlow/HUhigh is ∼0/0 (water), ∼394/238 (brain), ∼1283/1085 (cortical bone) and ∼3000/1800 (titanium). Conclusion: The feasibility of the proposed DECT implementation using a beam modifier has been demonstrated. Compared to the existing DECT solutions, the proposed scheme is much more cost-effective and requires minimum hardware modification. The work lays foundation for us to study the quantification of HU values to derive material density images and atomic number (and electron density) of substances.« less

Authors:
; ;  [1]; ;  [2];  [3]
  1. Stanford University, Palo Alto, CA (United States)
  2. Department of Radiation Oncology, Graduate School of Medicine, Sapporo, Hokkaido (Japan)
  3. Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido (Japan)
Publication Date:
OSTI Identifier:
22642240
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; BEAMS; BIOMEDICAL RADIOGRAPHY; BRAIN; COMPUTERIZED TOMOGRAPHY; IMAGES; MODULATION; PATIENTS; PLANNING; RADIATION DOSES; RADIOTHERAPY; SKELETON; TITANIUM

Citation Formats

Vinke, R, Peng, H, Xing, L, Takao, S, Shirato, H, and Umegaki, K. SU-F-J-212: Enabling Conventional Cone Beam CT with the Capability of Dual Energy Imaging Using a Simple Add-On Beam Modifier. United States: N. p., 2016. Web. doi:10.1118/1.4956120.
Vinke, R, Peng, H, Xing, L, Takao, S, Shirato, H, & Umegaki, K. SU-F-J-212: Enabling Conventional Cone Beam CT with the Capability of Dual Energy Imaging Using a Simple Add-On Beam Modifier. United States. doi:10.1118/1.4956120.
Vinke, R, Peng, H, Xing, L, Takao, S, Shirato, H, and Umegaki, K. 2016. "SU-F-J-212: Enabling Conventional Cone Beam CT with the Capability of Dual Energy Imaging Using a Simple Add-On Beam Modifier". United States. doi:10.1118/1.4956120.
@article{osti_22642240,
title = {SU-F-J-212: Enabling Conventional Cone Beam CT with the Capability of Dual Energy Imaging Using a Simple Add-On Beam Modifier},
author = {Vinke, R and Peng, H and Xing, L and Takao, S and Shirato, H and Umegaki, K},
abstractNote = {Purpose: In searching for a robust, efficient and cost-effective dual energy cone beam CT (DECBCT) solution for various radiation oncology applications, in particularly for improved proton dose planning/replanning accuracy and DE-CBCT guided radiation therapy, we investigate a novel energy modulation scheme using a beam modifier placed between the source and patient and optimize its geometric configuration for routine clinical use. Methods: The study was performed using a Hitachi CBCT scanner and the tube voltage was set at 125 kVp. The higher energy beam was obtained by filtering the incident utilizing a beam modulation layer (material: copper, thickness: 1.8 mm). To avoid the need for double scans (one with and one without the energy modulator), the modulation layer was configured to cover only the half of the X-ray beam so that two sets of sinograms corresponding low and high energies were collected after a single gantry rotation of 360 deg. The average high energy and low energy HU numbers (HUhigh and HUlow) were derived for pixels in a defined region-of-interest, respectively. Results: The beam modifier increased the threshold of the energy spectrum from ∼20 keV up to ∼50 keV. Two complete sets of images were obtained with good alignment between the high energy and low-energy cases without any artifact observed (Fig. 2). The HUlow/HUhigh is ∼0/0 (water), ∼394/238 (brain), ∼1283/1085 (cortical bone) and ∼3000/1800 (titanium). Conclusion: The feasibility of the proposed DECT implementation using a beam modifier has been demonstrated. Compared to the existing DECT solutions, the proposed scheme is much more cost-effective and requires minimum hardware modification. The work lays foundation for us to study the quantification of HU values to derive material density images and atomic number (and electron density) of substances.},
doi = {10.1118/1.4956120},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • Purpose: To evaluate the sensitivity of dual-phase cone-beam computed tomography during hepatic arteriography (CBCTHA) for the detection of hepatocellular carcinoma (HCC) by comparing it with the diagnostic imaging 'gold standard': contrast-enhanced magnetic resonance imaging (CE-MRI) of the liver. Materials and Methods: Eighty-eight HCC lesions (mean diameter 3.9 {+-} 3.3 cm) in 20 patients (13 men, mean age 61.4 years [range 50 to 80]), who sequentially underwent baseline diagnostic liver CE-MRI and then underwent early arterial- and delayed portal venous-phase CBCTHA during drug eluting-bead transarterial chemoembolization, were evaluated. Dual-phase CBCTHA findings of each tumor in terms of conspicuity were compared withmore » standard CE-MR images and classified into three grades: optimal, suboptimal, and nondiagnostic. Results: Seventy-seven (mean diameter 4.2 {+-} 3.4 cm [range 0.9 to 15.9]) (93.9%) of 82 tumors were detected. Sensitivity of arterial-phase (71.9%) was lower than that of venous-phase CBCTHA (86.6%) for the detection of HCC lesions. Of the 82 tumors, 33 (40.2%) and 52 (63.4%), 26 (31.7%) and 19 (23.2%), and 23 (28%) and 11 (13.4%) nodules were classed as optimal, suboptimal, and nondiagnostic on arterial- and venous-phase CBCTHA images, respectively. Seventeen (73.9%) of the 23 tumors that were not visible on arterial phase were detected on venous phase. Six (54.5%) of the 11 tumors that were not visible on venous phase were detected on arterial phase. Conclusions: Dual-phase CBCTHA has sufficient image quality to detect the majority of HCC lesions compared with the imaging 'gold standard': CE-MRI of the liver. Moreover, dual-phase CBCTHA is more useful and reliable than single-phasic imaging to depict HCC nodules.« less
  • Purpose: Dual energy cone beam CT system is finding a variety of promising applications in diagnostic CT, both in imaging of endogenous materials and exogenous materials across a range of body sites. Dual energy cone beam CT system to suggest in this study acquire image by rotating 360 degree with half of the X-ray window covered using copper modulation layer. In the region that covered by modulation layer absorb the low energy X-ray by modulation layer. Relative high energy X-ray passes through the layer and contributes to image reconstruction. Dose evaluation should be carried out in order to utilize suchmore » an imaging acquirement technology for clinical use. Methods: For evaluating imaging dose of modulation layer based dual energy cone beam CT system, Prototype cone beam CT that configured X-ray tube (D054SB, Toshiba, Japan) and detector (PaxScan 2520V, Varian Medical Systems, Palo Alto, CA) is used. A range of 0.5–2.0 mm thickness of modulation layer is implemented in Monte Carlo simulation (MCNPX, ver. 2.6.0, Los Alamos National Laboratory, USA) with half of X-ray window covered. In-house phantom using in this study that has 3 cylindrical phantoms configured water, Teflon air with PMMA covered for verifying the comparability the various material in human body and is implemented in Monte Carlo simulation. The actual dose with 2.0 mm copper covered half of X-ray window is measured using Gafchromic EBT3 film with 5.0 mm bolus for compared with simulative dose. Results: Dose in phantom reduced 33% by copper modulation layer of 2.0 mm. Scattering dose occurred in modulation layer by Compton scattering effect is 0.04% of overall dose. Conclusion: Modulation layer of that based dual energy cone beam CT has not influence on unnecessary scatter dose. This study was supported by the Radiation Safety Research Programs (1305033) through the Nuclear Safety and Security Commission.« less
  • Purpose: To compare markerless template-based tracking of lung tumors using dual energy (DE) cone-beam computed tomography (CBCT) projections versus single energy (SE) CBCT projections. Methods: A RANDO chest phantom with a simulated tumor in the upper right lung was used to investigate the effectiveness of tumor tracking using DE and SE CBCT projections. Planar kV projections from CBCT acquisitions were captured at 60 kVp (4 mAs) and 120 kVp (1 mAs) using the Varian TrueBeam and non-commercial iTools Capture software. Projections were taken at approximately every 0.53° while the gantry rotated. Due to limitations of the phantom, angles for whichmore » the shoulders blocked the tumor were excluded from tracking analysis. DE images were constructed using a weighted logarithmic subtraction that removed bony anatomy while preserving soft tissue structures. The tumors were tracked separately on DE and SE (120 kVp) images using a template-based tracking algorithm. The tracking results were compared to ground truth coordinates designated by a physician. Matches with a distance of greater than 3 mm from ground truth were designated as failing to track. Results: 363 frames were analyzed. The algorithm successfully tracked the tumor on 89.8% (326/363) of DE frames compared to 54.3% (197/363) of SE frames (p<0.0001). Average distance between tracking and ground truth coordinates was 1.27 +/− 0.67 mm for DE versus 1.83+/−0.74 mm for SE (p<0.0001). Conclusion: This study demonstrates the effectiveness of markerless template-based tracking using DE CBCT. DE imaging resulted in better detectability with more accurate localization on average versus SE. Supported by a grant from Varian Medical Systems.« less
  • Purpose: The aim of this study is to evaluate the feasibility of using a dual-energy CBCT (DECBCT) in proton therapy treatment planning to allow for accurate electron density estimation. Methods: For direct comparison, two scenarios were selected: a dual-energy fan-beam CT (high: 140 kVp, low: 80 kVp) and a DECBCT (high: 125 kVp, low: 80 kVp). A Gammex 467 tissue characterization phantom was used, including the rods of air, water, bone (B2–30% mineral), cortical bone (SB3), lung (LN-300), brain, liver and adipose. For the CBCT, Hounsfield Unit (HU) numbers were first obtained from the reconstructed images after a calibration wasmore » made based on water (=0) and air materials (=−1000). For each tissue surrogate, region-of-interest (ROI) analyses were made to derive high-energy and low-energy HU values (HUhigh and HUlow), which were subsequently used to estimate electron density based on the algorithm as previously described by Hunemohr N., et al. Parameters k1 and k2 are energy dependent and can be derived from calibration materials. Results: While for the dual-energy FBCT, the electron density is found be within +/−3% error relative to the values provided by the phantom vendor: −1.8% (water), 0.03% (lung), 1.1% (brain), −2.82% (adipose), −0.49% (liver) and −1.89% (cortical bones). While for the DECBCT, the estimation of electron density exhibits a relatively larger variation: −1.76% (water), −36.7% (lung), −1.92% (brain), −3.43% (adipose), 8.1% (liver) and 9.5% (cortical bones). Conclusion: For DECBCT, the accuracy of electron density estimation is inferior to that of a FBCT, especially for materials of either low-density (lung) or high density (cortical bone) compared to water. Such limitation arises from inaccurate HU number derivation in a CBCT. Advanced scatter-correction and HU calibration routines, as well as the deployment of photon counting CT detectors need be investigated to minimize the difference between FBCT and CBCT.« less