REVIEW ARTICLE
Oncological Applications of Dual-Energy Computed Tomography Imaging Jijo Paul, PhD, Thomas J. Vogl, MD, and Emmanuel C. Mbalisike, MD Abstract: Dual-energy computed tomography (DECT) imaging is a promising method used in oncology for accurate detection/diagnosis of malignant and benign lesions. Use of dual-energy spectral, weighted average, color-coded map, and virtual unenhanced images provides increased visual detection and easy lesion delineation. Lesion detectability, sensitivity, and conspicuity are significantly improved using DECT. Material characterization and decomposition are promising using DECT. Both anatomical and functional information related to oncology can be provided by DECT using single contrast-enhanced CT. Key Words: lesion delineation, DECT applications, spectral image, weighted average data, cancer imaging (J Comput Assist Tomogr 2014;38: 834–842)
T
he diagnosis and staging of cancer are particularly important in oncological imaging. Dual-energy computed tomography (DECT) imaging is one of the new and promising methods used in oncology for accurate detection of discrete or diffused primary as well as metastatic tumors.
(suppose the imaged spectral data are 80 and 140 kV) are linearly weighted and fused based on a preselected ratio according to the provided formula to generate WA data.13,14 [W P80] + [(1 W) P140], where W is the required WA value; the value could be selected as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9 based on requirement. Noncontrast unenhanced virtual images (VUIs) can be generated using contrast-enhanced DECT spectral data sets without additional imaging. The major advantage of 80-kV over 140-kV image data is increased Hounsfield unit (HU) values especially with contrast material (CM).14 However, the contrast-to-noise ratio (CNR) and signal-to-noise ratio are higher in WA data sets especially with the image data close to 120-kV spectrum.14–16 Furthermore, 60% of information from 80 kV and 40% from 140 kVof mixed data (0.6 of WA) provide improved CNR as well as overall subjective image quality including lesion delineation.14,15 Analysis based on subjective and objective image qualities showed a higher and similar result for single-source CT and DECT 0.6-WA data.17
Image Postprocessing TECHNICAL DETAILS The concept of dual-energy imaging emerged in 1976; however, this concept was not widely used for clinical applications because it was quite complex and difficult, because it required multiple examinations and delivered double radiation dose to patients.1–4 Recent DECT system is equipped with 2 x-ray tubes and 2 corresponding detector systems that rotate around the patient simultaneously to acquire image data using the principle of multidetector CT.5–8 Corresponding detectors and its 2 separate image data acquisition systems are mounted onto the rotating gantry with a specific angular offset.7 Generally, both detector arrays (corresponding to x-ray tubes A and B) cover the entire field of view during imaging of the patients depending on the generation of the imager. Explanation of the complete details regarding DECT is not within the scope of this study. However, DECT basic principles, physics, image formation, and hardware approaches as well as discrete differences between single and DECT imaging approaches have been previously published.7,9–12
DECT Image Fusion and Virtual Image Data In addition to the spectral image data sets (generally from 80 and 140 kV), the system has the ability to generate many additional fused images called weighted average (WA) data sets. This additional information obtained from WA images can be effectively used for clinical diagnosis. The pixels of the image data sets
From the Department of Diagnostic and Interventional Radiology, Frankfurt University Hospital, Frankfurt, Germany. Received for publication March 28, 2014; accepted June 9, 2014. Reprints: Jijo Paul, PhD, Department of Diagnostic and Interventional Radiology, Frankfurt University Hospital, Theodor-Stern-Kai-7, Frankfurt/Main 60590, Germany (e‐mail: [email protected]). The authors declare no conflict of interest. Copyright © 2014 by Lippincott Williams & Wilkins
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Image postprocessing can be performed using different software tools to achieve accurate image diagnosis for various diseases. Dual-energy postprocessing allows removing iodine from the contrast-enhanced image data, and a VUI can be generated using postprocessing algorithm.13,18,19 Software tools used to modify the acquired patient image data are 2-dimensional reconstruction tool, maximum and minimum intensity projections, 3-dimensional reconstructions (shaded surface display, volume rendering, computed aided detection, qualitative lung parenchymal assessment, density marks, CT attenuation histogram analysis, complex textural analysis), VUI and contrast-enhanced imaging, color-coded image data (shows iodine distribution) ventilation imaging, and different disease postprocessing clinical application tools.11,20
ONCOLOGICAL APPLICATIONS Applications of the Head and Neck Region The detection of tumors on CT images is important during cancer imaging as well as cancer staging.21 The iodine distribution in the body on image is subtracted from all regions using DECT software producing VUI data, which helps to separate enhancing lesions from other high-attenuation lesions/calcifications without further imaging.22 For head and neck cancer detection, the color-coded map (generated using iodine distribution data) superimposed with VUI provides increased visual detection of lesions due to excellent anatomical details leading to easy delineation of lesions.22 Figure 1 shows DECT of neck axial images with right oropharyngeal carcinoma. During CT imaging of the acute intracerebral hemorrhage, there are possibilities to hide the presence of an underlying tumor due to the enhancement of CM. Kim et al23 performed a study using DECT to differentiate tumor bleeding from pure hemorrhage. They used single-energy true unenhanced image (TUI) and postcontrast
J Comput Assist Tomogr • Volume 38, Number 6, November/December 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
J Comput Assist Tomogr • Volume 38, Number 6, November/December 2014
Dual-Energy CT-Oncological Applications
FIGURE 1. Generated dual-energy cross-sectional CT image data of the neck with oropharyngeal carcinoma. A, Cross-sectional image obtained using 140-kV tube potential. B, Image generated using 0.6 WA (this image is close to 120-kV acquisition). C, Image acquired using 80-kV tube potential. D, Color-coded image using 0.6 WA data (showing iodine distribution in the tumor and higher anatomical details). E, True unenhanced axial image with color map. F, TUI generated using 120-kV tube potential. G, Virtual unenhanced axial image with color map. Figure 1 can be viewed online in color at www.jcat.org.
DECT on 56 patients with unknown-origin spontaneous intracerebral hemorrhage. The authors found that the diagnostic performance of DECT WA data was significantly superior to the conventional postcontrast CT (P = 0.006). Furthermore, the comparison between DECT and standard contrast-enhanced CT showed a higher sensitivity (94.4% vs 61.1%) and specificity (97.4% vs 92.3%) favoring DECT. This DECT approach is effective during imaging when the presence of high-attenuation hematoma or the enhancing portion of the lesion is small. Furthermore, the replacement of TUI with VUI data provides a reduced patient dose due to the elimination of second patient examination. A combined analysis using WA and contrast-enhanced spectral data sets produces excellent diagnostic performance during the imaging of laryngeal cartilage invasion by squamous cell carcinoma.6 Thyroid nodules are common, and differentiation of nodules, that is, benign from malignant, has potential diagnostic and clinical impact. Li et al24 published an article using 97 specimens (pathologically confirmed 169 nodules) consisting of 108 nodular goiters, 47 follicular adenomas, and 14 papillary carcinomas. They obtained statistically significant difference between benign and malignant nodules for iodine concentration (P < 0.001), HU curve slops (P < 0.001), and effective atomic number (P < 0.001) using DECT imaging. In addition, they concluded that VUI and material decomposition using DECT provides promising potential for diagnostic differentiation of benign and malignant nodules; DECT © 2014 Lippincott Williams & Wilkins
could provide specific characterization of thyroid nodules in the absence of fine-needle aspiration biopsy.
Applications of the Thoracic Region Usually, 2 different CT acquisitions are required for solitary pulmonary nodule assessment, unenhanced imaging (detecting the presence of calcification), and an enhanced imaging (detection of the degree and pattern of enhancement) using CM. This is important to differentiate benign from malignant lesions. The DECT is capable of producing contrast-enhanced data and VUI data simultaneously; hence, single imaging simply derives calcification and enhancement details25 (Table 1). This omitting of unenhanced imaging provides a reduction of dose and measurement error (arising during the subtraction of unenhanced from an enhanced image due to different regions of interest). The generated iodine maps using DECT have the potential to assess pulmonary nodules relative to its vascularity.26 The accurate assessment of tissue enhancement provides the possibility of replacing dynamic CT perfusion data acquisition; however, this feasibility further reduces patient dose. The DECT is a valuable functional imaging tool for the assessment of nonsmall cell lung carcinoma (NSCLC). Contrast-enhanced DECT was correlated with maximum standardized uptake value (SUVmax) of 18-fluorine-deoxyglucose positron emission www.jcat.org
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
835
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72 60 17 49
Patient Number
100 100 — 100
CM, mL
Knöss et al26 (2011) Phantom — 37 105 Schmid-Bindert et al27 (2012) 15 1.5 mL/kg Chandarana et al30 (2011) Graser et al33 (2009) 110 1.35 mL/kg Phantom — Brown et al34 (2009) 60 120 Song et al35 (2011) 40 1.5 mL/kg Altenbernd et al37 (2011) 42 1.5 mL/kg Park et al38 (2011) Marin et al39 (2009) 48 150 24 80 Klauß et al46 (2013) 15 1.5 mL/kg Macari et al47 (2010) Ho et al51 (2012) 19 150 96 1.5 mL/kg Pan et al54 (2013) 21 120 Boellaard et al56 (2013) 44 100–120 Qian et al57 (2012) Kaza et al63 (2013) 39 100
Kuno et al6 (2012) Tawfik et al15 (2012) Gupta et al18 (2010) Chae et al25 (2010)
Publication 200/200 151/302 385/675 210/50
Current, mAs
140/80 50/200 140/80 50/235 120, Sn140/80 240, 125/687 120, 140/80 240, 96/404 140/100 133/565 120, Sn140/80 180, 162/299 120, 140/80 240, 96/404 140/80 96/404 140, 80 308, 540 Sn140/80 50/270 120, 140/80 56–80/370–480 120, 140/80 250, 126/499 140/80 600 Sn140/100 178/230 140/80 600 120, 140/80 100–400, auto
Sn140/100 Sn140/80 140/80 140/80
Energy, kV
1 2 1.5 5 3 — 3,3 — 5, 5 5 1.2 5 2.5 3 5 2.5, 2.5
1 2 2.5 2
Section thickness, mm
D40f and B50f D30f D30f — D30f — B30f, D30f — B31f B31f — — — — — —
D30f/B30f D30f — D30f
Recon. Kernel
0.7 1.2 0.5–0.7 1.2, 0.55 0.55 1.2, 0.55 1.2/0.55 0.85 — — 0.5–0.7 1, 0.55 — 0.7 1.3 1.375:1
0.6 0.9 — 0.7
Pitch
Energy Weighting
0.5, virtual 0.3, 0.6, 0.8 — Nonenhanced WA, enhanced WA, virtual, enhanced 64 0.6 — 14 1.2 0.3, virtual 64 0.6,14 1.2 0.3, virtual 64 0.6, 14 1.2 0.3, virtual 64 0.6 0.3, virtual 128 0.6, 32 0.6 0.5, virtual 64 0.6/14 1.2 2 0.3, virtual 24 1.2 0.3 64 0.625 — 14 1.2 0.3 64 0.6, 14 1.2 0.3, virtual 64 0.6, 14 1.2 — – Mono and poly 32 0.6 0.5, virtual – — – —
32 0.6 128 0.6 64 0.625 14 1.2
Detector Collimation, mm
TABLE 1. Technical Parameters Used for Oncological Imaging of Different Body Regions Using DECT in Different Publications From 2009 to 2013
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes — Yes
Yes Yes Yes Yes
Tube Current Modulation
Paul et al J Comput Assist Tomogr • Volume 38, Number 6, November/December 2014
© 2014 Lippincott Williams & Wilkins
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Result
Conclusion
© 2014 Lippincott Williams & Wilkins
www.jcat.org
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Continued next page
Specificity of DECT WA and contrast CT was Using both WA and contrast images of DECT improved the significantly higher than WA images alone (96% vs 70%). diagnostic performance during the evaluation of carcinoma. CNR significantly increased from 140 kV to 0.6-WA data. Dual-energy 0.6 WA shows improved tumor CNR and lesion Tawfik et al15 (2012) Mean tumor enhancement showed a stepwise increase with a delineation. 0.6-WA data were superior to 0.3 WA. decrease from 140 to 80 kV. Fused 0.6 WA produced best image quality score. Metastatic lesions showed an increase in HU at 80-kV data; furthermore, decreased A change in HU between 140- and 80-kV data was shown to be Gupta et al18 (2010) HU with 80 kV is an indicator of intracellular lipid within an adenoma. a specific sign of adrenal adenoma. Metastatic lesions from lipid-poor adrenal adenomas can be differentiated. Calcifications in the solitary pulmonary nodule (85%) and Detection of calcifications and degree of contrast enhancement are Chae et al25 (2010) lymph nodes (97.8%) were detected using VUI. possible without additional imaging. Calcium can be differentiated from CM using ≥16-mm-diameter artificial Iodine and calcium can be easily differentiated in lesions, Knöss et al26 (2011) nodules in vitro, but clearer differentiation is difficult for lesions < 16 mm. but smaller lesion's differentiation is difficult. Schmid-Bindert et al27 (2012) Moderate correlation was found between HU of DECT and SUVmax in all tumors. DECT could be used as a valuable functional imaging test for A strong correlation among contrast DECT and SUVmax was found in patients patients with NSCLC as the contrast DECT correlates with SUVmax. with NSCLC. Thoracic lymph node showed moderate correlation between SUVmax and DECT. Lesion contrast concentration and lesion-to-aorta ratio in enhancing masses DECT can be used to estimate the presence and concentration of iodine Chandarana et al30 (2011) were significantly higher (P < 0.0001) than in hyperdense and simple renal cysts. in lesions. Characterization of renal masses could be possible without unenhanced images. Obtained renal parenchymal attenuation were 30.8 and 31.6 (7.1) HU (P = 0.29) Graser et al33 (2009) VUI data are a reasonable approximation of TUI data during with VUI and TUI; liver, 55.8 and 57.8 HU (P = 0.11). Image qualities were renal mass evaluation. DECT reduces patient exposure by 35% because 1.70 HU for VUI and 1.15 HU for TUI (P = 0.0001). of the elimination of additional imaging. Enhancing masses and cysts were identified with 97% of sensitivity and 83% of Enhancing renal masses can be detected using DECT and CM Brown et al34 (2009) specificity. 10-HU lesions (92%) and lesions with 20 or 40 HU were detected with high sensitivity. correctly. Contrast-enhanced DECT showed 21 renal cell carcinomas of >20HU, 36 simple Contrast-enhanced DECT with VUI could be useful for characterizing Song et al35 (2011) cysts, and 10 hemorrhagic cysts of
Oncological Applications of Dual-Energy Computed Tomography Imaging Jijo Paul, PhD, Thomas J. Vogl, MD, and Emmanuel C. Mbalisike, MD Abstract: Dual-energy computed tomography (DECT) imaging is a promising method used in oncology for accurate detection/diagnosis of malignant and benign lesions. Use of dual-energy spectral, weighted average, color-coded map, and virtual unenhanced images provides increased visual detection and easy lesion delineation. Lesion detectability, sensitivity, and conspicuity are significantly improved using DECT. Material characterization and decomposition are promising using DECT. Both anatomical and functional information related to oncology can be provided by DECT using single contrast-enhanced CT. Key Words: lesion delineation, DECT applications, spectral image, weighted average data, cancer imaging (J Comput Assist Tomogr 2014;38: 834–842)
T
he diagnosis and staging of cancer are particularly important in oncological imaging. Dual-energy computed tomography (DECT) imaging is one of the new and promising methods used in oncology for accurate detection of discrete or diffused primary as well as metastatic tumors.
(suppose the imaged spectral data are 80 and 140 kV) are linearly weighted and fused based on a preselected ratio according to the provided formula to generate WA data.13,14 [W P80] + [(1 W) P140], where W is the required WA value; the value could be selected as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9 based on requirement. Noncontrast unenhanced virtual images (VUIs) can be generated using contrast-enhanced DECT spectral data sets without additional imaging. The major advantage of 80-kV over 140-kV image data is increased Hounsfield unit (HU) values especially with contrast material (CM).14 However, the contrast-to-noise ratio (CNR) and signal-to-noise ratio are higher in WA data sets especially with the image data close to 120-kV spectrum.14–16 Furthermore, 60% of information from 80 kV and 40% from 140 kVof mixed data (0.6 of WA) provide improved CNR as well as overall subjective image quality including lesion delineation.14,15 Analysis based on subjective and objective image qualities showed a higher and similar result for single-source CT and DECT 0.6-WA data.17
Image Postprocessing TECHNICAL DETAILS The concept of dual-energy imaging emerged in 1976; however, this concept was not widely used for clinical applications because it was quite complex and difficult, because it required multiple examinations and delivered double radiation dose to patients.1–4 Recent DECT system is equipped with 2 x-ray tubes and 2 corresponding detector systems that rotate around the patient simultaneously to acquire image data using the principle of multidetector CT.5–8 Corresponding detectors and its 2 separate image data acquisition systems are mounted onto the rotating gantry with a specific angular offset.7 Generally, both detector arrays (corresponding to x-ray tubes A and B) cover the entire field of view during imaging of the patients depending on the generation of the imager. Explanation of the complete details regarding DECT is not within the scope of this study. However, DECT basic principles, physics, image formation, and hardware approaches as well as discrete differences between single and DECT imaging approaches have been previously published.7,9–12
DECT Image Fusion and Virtual Image Data In addition to the spectral image data sets (generally from 80 and 140 kV), the system has the ability to generate many additional fused images called weighted average (WA) data sets. This additional information obtained from WA images can be effectively used for clinical diagnosis. The pixels of the image data sets
From the Department of Diagnostic and Interventional Radiology, Frankfurt University Hospital, Frankfurt, Germany. Received for publication March 28, 2014; accepted June 9, 2014. Reprints: Jijo Paul, PhD, Department of Diagnostic and Interventional Radiology, Frankfurt University Hospital, Theodor-Stern-Kai-7, Frankfurt/Main 60590, Germany (e‐mail: [email protected]). The authors declare no conflict of interest. Copyright © 2014 by Lippincott Williams & Wilkins
834
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Image postprocessing can be performed using different software tools to achieve accurate image diagnosis for various diseases. Dual-energy postprocessing allows removing iodine from the contrast-enhanced image data, and a VUI can be generated using postprocessing algorithm.13,18,19 Software tools used to modify the acquired patient image data are 2-dimensional reconstruction tool, maximum and minimum intensity projections, 3-dimensional reconstructions (shaded surface display, volume rendering, computed aided detection, qualitative lung parenchymal assessment, density marks, CT attenuation histogram analysis, complex textural analysis), VUI and contrast-enhanced imaging, color-coded image data (shows iodine distribution) ventilation imaging, and different disease postprocessing clinical application tools.11,20
ONCOLOGICAL APPLICATIONS Applications of the Head and Neck Region The detection of tumors on CT images is important during cancer imaging as well as cancer staging.21 The iodine distribution in the body on image is subtracted from all regions using DECT software producing VUI data, which helps to separate enhancing lesions from other high-attenuation lesions/calcifications without further imaging.22 For head and neck cancer detection, the color-coded map (generated using iodine distribution data) superimposed with VUI provides increased visual detection of lesions due to excellent anatomical details leading to easy delineation of lesions.22 Figure 1 shows DECT of neck axial images with right oropharyngeal carcinoma. During CT imaging of the acute intracerebral hemorrhage, there are possibilities to hide the presence of an underlying tumor due to the enhancement of CM. Kim et al23 performed a study using DECT to differentiate tumor bleeding from pure hemorrhage. They used single-energy true unenhanced image (TUI) and postcontrast
J Comput Assist Tomogr • Volume 38, Number 6, November/December 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
J Comput Assist Tomogr • Volume 38, Number 6, November/December 2014
Dual-Energy CT-Oncological Applications
FIGURE 1. Generated dual-energy cross-sectional CT image data of the neck with oropharyngeal carcinoma. A, Cross-sectional image obtained using 140-kV tube potential. B, Image generated using 0.6 WA (this image is close to 120-kV acquisition). C, Image acquired using 80-kV tube potential. D, Color-coded image using 0.6 WA data (showing iodine distribution in the tumor and higher anatomical details). E, True unenhanced axial image with color map. F, TUI generated using 120-kV tube potential. G, Virtual unenhanced axial image with color map. Figure 1 can be viewed online in color at www.jcat.org.
DECT on 56 patients with unknown-origin spontaneous intracerebral hemorrhage. The authors found that the diagnostic performance of DECT WA data was significantly superior to the conventional postcontrast CT (P = 0.006). Furthermore, the comparison between DECT and standard contrast-enhanced CT showed a higher sensitivity (94.4% vs 61.1%) and specificity (97.4% vs 92.3%) favoring DECT. This DECT approach is effective during imaging when the presence of high-attenuation hematoma or the enhancing portion of the lesion is small. Furthermore, the replacement of TUI with VUI data provides a reduced patient dose due to the elimination of second patient examination. A combined analysis using WA and contrast-enhanced spectral data sets produces excellent diagnostic performance during the imaging of laryngeal cartilage invasion by squamous cell carcinoma.6 Thyroid nodules are common, and differentiation of nodules, that is, benign from malignant, has potential diagnostic and clinical impact. Li et al24 published an article using 97 specimens (pathologically confirmed 169 nodules) consisting of 108 nodular goiters, 47 follicular adenomas, and 14 papillary carcinomas. They obtained statistically significant difference between benign and malignant nodules for iodine concentration (P < 0.001), HU curve slops (P < 0.001), and effective atomic number (P < 0.001) using DECT imaging. In addition, they concluded that VUI and material decomposition using DECT provides promising potential for diagnostic differentiation of benign and malignant nodules; DECT © 2014 Lippincott Williams & Wilkins
could provide specific characterization of thyroid nodules in the absence of fine-needle aspiration biopsy.
Applications of the Thoracic Region Usually, 2 different CT acquisitions are required for solitary pulmonary nodule assessment, unenhanced imaging (detecting the presence of calcification), and an enhanced imaging (detection of the degree and pattern of enhancement) using CM. This is important to differentiate benign from malignant lesions. The DECT is capable of producing contrast-enhanced data and VUI data simultaneously; hence, single imaging simply derives calcification and enhancement details25 (Table 1). This omitting of unenhanced imaging provides a reduction of dose and measurement error (arising during the subtraction of unenhanced from an enhanced image due to different regions of interest). The generated iodine maps using DECT have the potential to assess pulmonary nodules relative to its vascularity.26 The accurate assessment of tissue enhancement provides the possibility of replacing dynamic CT perfusion data acquisition; however, this feasibility further reduces patient dose. The DECT is a valuable functional imaging tool for the assessment of nonsmall cell lung carcinoma (NSCLC). Contrast-enhanced DECT was correlated with maximum standardized uptake value (SUVmax) of 18-fluorine-deoxyglucose positron emission www.jcat.org
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
835
836
www.jcat.org
72 60 17 49
Patient Number
100 100 — 100
CM, mL
Knöss et al26 (2011) Phantom — 37 105 Schmid-Bindert et al27 (2012) 15 1.5 mL/kg Chandarana et al30 (2011) Graser et al33 (2009) 110 1.35 mL/kg Phantom — Brown et al34 (2009) 60 120 Song et al35 (2011) 40 1.5 mL/kg Altenbernd et al37 (2011) 42 1.5 mL/kg Park et al38 (2011) Marin et al39 (2009) 48 150 24 80 Klauß et al46 (2013) 15 1.5 mL/kg Macari et al47 (2010) Ho et al51 (2012) 19 150 96 1.5 mL/kg Pan et al54 (2013) 21 120 Boellaard et al56 (2013) 44 100–120 Qian et al57 (2012) Kaza et al63 (2013) 39 100
Kuno et al6 (2012) Tawfik et al15 (2012) Gupta et al18 (2010) Chae et al25 (2010)
Publication 200/200 151/302 385/675 210/50
Current, mAs
140/80 50/200 140/80 50/235 120, Sn140/80 240, 125/687 120, 140/80 240, 96/404 140/100 133/565 120, Sn140/80 180, 162/299 120, 140/80 240, 96/404 140/80 96/404 140, 80 308, 540 Sn140/80 50/270 120, 140/80 56–80/370–480 120, 140/80 250, 126/499 140/80 600 Sn140/100 178/230 140/80 600 120, 140/80 100–400, auto
Sn140/100 Sn140/80 140/80 140/80
Energy, kV
1 2 1.5 5 3 — 3,3 — 5, 5 5 1.2 5 2.5 3 5 2.5, 2.5
1 2 2.5 2
Section thickness, mm
D40f and B50f D30f D30f — D30f — B30f, D30f — B31f B31f — — — — — —
D30f/B30f D30f — D30f
Recon. Kernel
0.7 1.2 0.5–0.7 1.2, 0.55 0.55 1.2, 0.55 1.2/0.55 0.85 — — 0.5–0.7 1, 0.55 — 0.7 1.3 1.375:1
0.6 0.9 — 0.7
Pitch
Energy Weighting
0.5, virtual 0.3, 0.6, 0.8 — Nonenhanced WA, enhanced WA, virtual, enhanced 64 0.6 — 14 1.2 0.3, virtual 64 0.6,14 1.2 0.3, virtual 64 0.6, 14 1.2 0.3, virtual 64 0.6 0.3, virtual 128 0.6, 32 0.6 0.5, virtual 64 0.6/14 1.2 2 0.3, virtual 24 1.2 0.3 64 0.625 — 14 1.2 0.3 64 0.6, 14 1.2 0.3, virtual 64 0.6, 14 1.2 — – Mono and poly 32 0.6 0.5, virtual – — – —
32 0.6 128 0.6 64 0.625 14 1.2
Detector Collimation, mm
TABLE 1. Technical Parameters Used for Oncological Imaging of Different Body Regions Using DECT in Different Publications From 2009 to 2013
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes — Yes
Yes Yes Yes Yes
Tube Current Modulation
Paul et al J Comput Assist Tomogr • Volume 38, Number 6, November/December 2014
© 2014 Lippincott Williams & Wilkins
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Result
Conclusion
© 2014 Lippincott Williams & Wilkins
www.jcat.org
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Continued next page
Specificity of DECT WA and contrast CT was Using both WA and contrast images of DECT improved the significantly higher than WA images alone (96% vs 70%). diagnostic performance during the evaluation of carcinoma. CNR significantly increased from 140 kV to 0.6-WA data. Dual-energy 0.6 WA shows improved tumor CNR and lesion Tawfik et al15 (2012) Mean tumor enhancement showed a stepwise increase with a delineation. 0.6-WA data were superior to 0.3 WA. decrease from 140 to 80 kV. Fused 0.6 WA produced best image quality score. Metastatic lesions showed an increase in HU at 80-kV data; furthermore, decreased A change in HU between 140- and 80-kV data was shown to be Gupta et al18 (2010) HU with 80 kV is an indicator of intracellular lipid within an adenoma. a specific sign of adrenal adenoma. Metastatic lesions from lipid-poor adrenal adenomas can be differentiated. Calcifications in the solitary pulmonary nodule (85%) and Detection of calcifications and degree of contrast enhancement are Chae et al25 (2010) lymph nodes (97.8%) were detected using VUI. possible without additional imaging. Calcium can be differentiated from CM using ≥16-mm-diameter artificial Iodine and calcium can be easily differentiated in lesions, Knöss et al26 (2011) nodules in vitro, but clearer differentiation is difficult for lesions < 16 mm. but smaller lesion's differentiation is difficult. Schmid-Bindert et al27 (2012) Moderate correlation was found between HU of DECT and SUVmax in all tumors. DECT could be used as a valuable functional imaging test for A strong correlation among contrast DECT and SUVmax was found in patients patients with NSCLC as the contrast DECT correlates with SUVmax. with NSCLC. Thoracic lymph node showed moderate correlation between SUVmax and DECT. Lesion contrast concentration and lesion-to-aorta ratio in enhancing masses DECT can be used to estimate the presence and concentration of iodine Chandarana et al30 (2011) were significantly higher (P < 0.0001) than in hyperdense and simple renal cysts. in lesions. Characterization of renal masses could be possible without unenhanced images. Obtained renal parenchymal attenuation were 30.8 and 31.6 (7.1) HU (P = 0.29) Graser et al33 (2009) VUI data are a reasonable approximation of TUI data during with VUI and TUI; liver, 55.8 and 57.8 HU (P = 0.11). Image qualities were renal mass evaluation. DECT reduces patient exposure by 35% because 1.70 HU for VUI and 1.15 HU for TUI (P = 0.0001). of the elimination of additional imaging. Enhancing masses and cysts were identified with 97% of sensitivity and 83% of Enhancing renal masses can be detected using DECT and CM Brown et al34 (2009) specificity. 10-HU lesions (92%) and lesions with 20 or 40 HU were detected with high sensitivity. correctly. Contrast-enhanced DECT showed 21 renal cell carcinomas of >20HU, 36 simple Contrast-enhanced DECT with VUI could be useful for characterizing Song et al35 (2011) cysts, and 10 hemorrhagic cysts of
