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Title: SU-G-TeP2-11: Initial Evaluation of a Novel Split-Filter Dual-Energy CT for Use in Radiation Oncology

Abstract

Purpose: To perform an initial evaluation of a novel split-filter dual-energy CT (DECT) system with the goal of understanding the clinical utility and limitations of the system for radiation therapy. Methods: Several phantoms were imaged using the split-filter DECT technique on the Siemens Edge CT scanner using a range of clinically-relevant doses. The optimum-contrast reconstruction, the mixed reconstruction, and the monoenergetic reconstructions (ranging from 40 keV to 190 keV) were evaluated. Each image was analyzed for CT number accuracy, uniformity, noise, low-contrast visibility (LCV), spatial resolution and geometric distortion. For comparison purposes, all parameters were evaluated on 120 kVp single-energy CT (SECT) scans used for treatment planning, as well as, a sequential-scan DECT technique for corresponding doses. Results: For all DECT reconstructions no observable geometric distortion was found. Both the optimal-contrast and mixed images demonstrated slight improvements in LCV and noise when compared to the SECT, and slight reductions in CT number accuracy and spatial resolution. The CT numbers trended as expected for the monoenergetic reconstructions, with CT number accuracy within 50 HU for materials of density <2 g/cm3. Spatial resolution increased with energy, and for monoenergetic reconstructions >70 keV the spatial resolution exceeded that of the SECT. The noisemore » in the monoenergetic reconstructions increased with decreasing energy. Thus, the image uniformity, signal-to-noise ratio and LCV were diminished at lower energies (70 keV). Applying iterative reconstruction techniques to the low-energy images reduced noise and improved LCV. The signal-to-noise ratio was stable for energies >100 keV. Conclusion: The initial commissioning of the novel split-filter DECT technology demonstrated favorable results for clinical implementation. The mixed reconstruction showed potential as a replacement for the treatment planning SECT. The image parameters for the monoenergetic reconstructions varied appropriately with energy. This work provides an initial understanding of the limitations and potential applications for monoenergetic imaging.« less

Authors:
; ; ;  [1]
  1. University of Wisconsin, Madison, WI (United States)
Publication Date:
OSTI Identifier:
22649391
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; ACCURACY; BIOMEDICAL RADIOGRAPHY; COMPUTERIZED TOMOGRAPHY; IMAGES; ITERATIVE METHODS; NOISE; SIGNAL-TO-NOISE RATIO; SPATIAL RESOLUTION

Citation Formats

Miller, J, Huang, J, Szczykutowicz, T, and Bayouth, J. SU-G-TeP2-11: Initial Evaluation of a Novel Split-Filter Dual-Energy CT for Use in Radiation Oncology. United States: N. p., 2016. Web. doi:10.1118/1.4957046.
Miller, J, Huang, J, Szczykutowicz, T, & Bayouth, J. SU-G-TeP2-11: Initial Evaluation of a Novel Split-Filter Dual-Energy CT for Use in Radiation Oncology. United States. doi:10.1118/1.4957046.
Miller, J, Huang, J, Szczykutowicz, T, and Bayouth, J. 2016. "SU-G-TeP2-11: Initial Evaluation of a Novel Split-Filter Dual-Energy CT for Use in Radiation Oncology". United States. doi:10.1118/1.4957046.
@article{osti_22649391,
title = {SU-G-TeP2-11: Initial Evaluation of a Novel Split-Filter Dual-Energy CT for Use in Radiation Oncology},
author = {Miller, J and Huang, J and Szczykutowicz, T and Bayouth, J},
abstractNote = {Purpose: To perform an initial evaluation of a novel split-filter dual-energy CT (DECT) system with the goal of understanding the clinical utility and limitations of the system for radiation therapy. Methods: Several phantoms were imaged using the split-filter DECT technique on the Siemens Edge CT scanner using a range of clinically-relevant doses. The optimum-contrast reconstruction, the mixed reconstruction, and the monoenergetic reconstructions (ranging from 40 keV to 190 keV) were evaluated. Each image was analyzed for CT number accuracy, uniformity, noise, low-contrast visibility (LCV), spatial resolution and geometric distortion. For comparison purposes, all parameters were evaluated on 120 kVp single-energy CT (SECT) scans used for treatment planning, as well as, a sequential-scan DECT technique for corresponding doses. Results: For all DECT reconstructions no observable geometric distortion was found. Both the optimal-contrast and mixed images demonstrated slight improvements in LCV and noise when compared to the SECT, and slight reductions in CT number accuracy and spatial resolution. The CT numbers trended as expected for the monoenergetic reconstructions, with CT number accuracy within 50 HU for materials of density <2 g/cm3. Spatial resolution increased with energy, and for monoenergetic reconstructions >70 keV the spatial resolution exceeded that of the SECT. The noise in the monoenergetic reconstructions increased with decreasing energy. Thus, the image uniformity, signal-to-noise ratio and LCV were diminished at lower energies (70 keV). Applying iterative reconstruction techniques to the low-energy images reduced noise and improved LCV. The signal-to-noise ratio was stable for energies >100 keV. Conclusion: The initial commissioning of the novel split-filter DECT technology demonstrated favorable results for clinical implementation. The mixed reconstruction showed potential as a replacement for the treatment planning SECT. The image parameters for the monoenergetic reconstructions varied appropriately with energy. This work provides an initial understanding of the limitations and potential applications for monoenergetic imaging.},
doi = {10.1118/1.4957046},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • A simple technique for obtaining dual energy information from a single computed tomography (CT) scan is described. The method involves filtering the two halves of the x-ray fan beam differently. It is shown that during a 360 degree scan, this split-filtration geometry results in dual energy noise analysis, valid for polychromatic x-ray beams, is presented and used to determine the optimal parameters for the split-filter scans. Using the theoretically optimal split-filter design installed on a commercial CT scanner, photoelectric and Compton images of a head phantom were obtained. Recombination of the photoelectric and Compton components of attenuation at arbitrary energiesmore » demonstrates the ability to remove spectral artifacts from conventional CT images.« less
  • Purpose: A prospective feasibility study was conducted to investigate the utility of dual-energy (DE) imaging compared to conventional x-ray imaging for patients undergoing kV-based image guided radiation therapy (IGRT) for lung cancer. Methods and Materials: An institutional review board-approved feasibility study enrolled patients with lung cancer undergoing IGRT and was initiated in September 2011. During daily setup, 2 sequential respiration-gated x-ray images were obtained using an on-board imager. Imaging was composed of 1 standard x-ray image at 120 kVp (1 mAs) and a second image obtained at 60 kVp (4 mAs). Weighted logarithmic subtraction of the 2 images was performed offline tomore » create a soft tissue-selective DE image. Conventional and DE images were evaluated by measuring relative contrast and contrast-to-noise ratios (CNR) and also by comparing spatial localization, using both approaches. Imaging dose was assessed using a calibrated ion chamber. Results: To date, 10 patients with stage IA to IIIA lung cancer were enrolled and 57 DE images were analyzed. DE subtraction resulted in complete suppression of overlying bone in all 57 DE images, with an average improvement in relative contrast of 4.7 ± 3.3 over that of 120 kVp x-ray images (P<.0002). The improvement in relative contrast with DE imaging was seen for both smaller (gross tumor volume [GTV] ≤5 cc) and larger tumors (GTV >5 cc), with average relative contrast improvement ratios of 3.4 ± 4.1 and 5.4 ± 3.6, respectively. Moreover, the GTV was reliably localized in 95% of the DE images versus 74% of the single energy (SE images, (P=.004). Mean skin dose per DE image set was 0.44 ± 0.03 mGy versus 0.43 ± 0.03 mGy, using conventional kV imaging parameters. Conclusions: Initial results of this feasibility study suggest that DE thoracic imaging may enhance tumor localization in lung cancer patients receiving kV-based IGRT without increasing imaging dose.« less
  • The initial results of a prospective randomized collaborative therapeutic trial of split-course radiotherapy in carcinoma of the nasopharynx are reported. The split-course therapy consisted of two irradiation courses, each delivering 3000 rad in 2 weeks, in 10 fractions of 300 rad. The courses were separated by a rest period of 3 weeks. Continuous radiation therapy consisted of 30 fractions of 220 rad each, for a total dose of 6600 rad. One hundred and nine patients were eligible for analysis with a minimal follow-up period of 1 year. No statistically significant differences were observed in the two therapeutic groups with regardmore » to acute toxicity (normal tissue reactions, completion of therapy, and need of hospitalization during radiotherapy), late toxicity, incidence of distant metastases, patients who became free of clinically detectable tumor in the primary and neck sites at last follow-up or at death, and survival after therapy.« less
  • One hundred forty-one patients with carcinoma of the base of tongue were randomized to receive either continuous course radiotherapy (6600 rad in 30/33 fractions over 7-8 weeks) or split course therapy (3000 rad in 10 fractions over 2 weeks, a three-week rest, 3000 rad in 10 fractions over 2 weeks). Both treatment groups tolerated the treatment well, but the continuous couse goup required more treatment modifications. The results of therapy, as judged by control of primary tumor, ocntrol of metastatic lymph nodes, time to failure and overall survival were comparable in the two treatment groups.
  • One hundred forty-one patients with carcinoma of the base of tongue were randomized to receive either continuous course radiotherapy (6600 rad in 30/33 fractions over 7-8 weeks) or split course therapy (3000 rad in 10 fractions over 2 weeks, a three-week rest, 3000 rad in 10 fractions over 2 weeks). Both treatment groups tolerated the treatment well, but the continuous course group required more treatment modifications. The results of therapy, as judged by control of primary tumor, control of metastatic lymph nodes, time to failure and overall survival were comparable in the two treatment groups.