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Multifocal hepatocellular carcinoma in a 54-year-old man with cirrhosis. Contrast-enhanced CT images obtained in the arterial phase (top row) show several (at least six) faintly enhancing liver nodules (arrows). Corresponding iodine images (with a color overlay; bottom row) show higher lesion-to-parenchyma contrast with improved lesion conspicuity, providing better depiction of nodules with varying enhancement patterns in a cirrhotic liver. In this case, follow-up MR imaging showed multiple arterial enhancing liver nodules with washout in the portal venous phase, a finding consistent with hepatocellular carcinoma.
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Dual-energy computed tomographic (DECT) technology offers enhanced capabilities that may benefit oncologic imaging in the abdomen. By using two different energies, dual-energy CT allows material decomposition on the basis of energy-dependent attenuation profiles of specific materials. Although image acquisition with dual-energy CT is similar to tha...
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Context 1
... specific maps depict and quantify iodine in each voxel; thus, a small amount of enhancement in a lesion may be detected. Another potential applica- tion of iodine-specific maps is improved depiction of nodules with varying enhancement patterns in patients with a cirrhotic liver (Fig 6). ...
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Citations
... Dual-energy CT (DECT) allows generation of materialspecific images based on the principle that materials with different tissue compositions attenuate x-rays differently and have material-specific behavior at varying x-ray energy levels [12]. Several studies have demonstrated the utility of low keV monoenergetic images and material-specific images, particularly iodine images, in various cancers, enabling superior lesion detection/characterization, treatment planning, and disease monitoring [13][14][15][16][17]. However, few studies have explored the benefits of DECT in PC [18,19]. ...
To assess the value of material density (MD) images generated from a rapid kilovoltage-switching dual-energy CT (rsDECT) in early detection of peritoneal carcinomatosis (PC).
Thirty patients (60 ± 13 years; 24 women) with PC detected on multiple abdominal DECT scans were included. Four separate DECTs with varying findings of PC from each patient were used for qualitative/quantitative analysis, resulting in a total of 120 DECT scans (n = 30 × 4). Three radiologists independently reviewed DECT images (65 keV alone and 65 keV + MD) for diagnosis of PC (diagnostic confidence, lesion conspicuity, sharpness/delineation and image quality) using a 5-point Likert scale. Quantitative estimation of contrast-to-noise ratio (CNR) was done. Wilcoxon signed-rank test and Odds ratio calculation were used to compare between the two protocols. Inter-observer agreement was evaluated using Kappa coefficient analysis. P values < 0.05 were considered statistically significant.
65 keV + MD images showed a slightly higher sensitivity (89%[95%CI:84,92]) for PC detection compared with 65 keV images alone without statistical significance (84%[95%CI:78,88], p = 0.11) with the experienced reader showing significant improvement (98%[95%CI:93,100] vs. 90%[95%CI:83,94], p = 0.02). On a per-patient basis, use of MD images allowed earlier diagnosis for PC in an additional 13–23% of patients. On sub-group analysis, earlier diagnosis of PC was particularly beneficial in patients with BMI ≤ 29.9 kg/m2. 65 keV + MD images showed higher diagnostic confidence, lesion conspicuity, and lesion sharpness for the experienced reader (p < 0.001). CNR was higher in MD images (1.7 ± 0.5) than 65 keV images (0.1 ± 0.02, p < 0.001). All readers showed moderate interobserver agreement for determining PC by both protocols (κ = 0.58 and κ = 0.47).
MD images allow earlier and improved detection of PC with the degree of benefit varying based on reader experience and patient body habitus.
... In abdominal imaging, CT has played a very important role in various diseases and conditions. In the field of oncology, CT has been used for detection, staging and preoperative planning of various tumors [1,2]. In chronic diseases, CT has also been used to evaluate substances present in the organs, such as fatty deposition in the liver in metabolic dysfunction-associated steatohepatitis or hepatic iron deposition in iron overload condition [3]. ...
Photon-counting CT has a completely different detector mechanism than conventional energy-integrating CT. In the photon-counting detector, X-rays are directly converted into electrons and received as electrical signals. Photon-counting CT provides virtual monochromatic images with a high contrast-to-noise ratio for abdominal CT imaging and may improve the ability to visualize small or low-contrast lesions. In addition, photon-counting CT may offer the possibility of reducing radiation dose. This review provides an overview of the actual clinical operation of photon-counting CT and its diagnostic utility in abdominal imaging. We also describe the clinical implications of photon-counting CT including imaging of hepatocellular carcinoma, liver metastases, hepatic steatosis, pancreatic cancer, intraductal mucinous neoplasm of the pancreas, and thrombus.
Graphical Abstract
... In this context, DECT postprocessing provides a variety of additional quantitative parameters of tumor characteristics, including atomic number maps (Rho/Z) showing the Rho and Z of lesions [16,17]. Numerous studies have assessed DECT advantages, especially in oncology [14,[18][19][20][21][22]. However, this technique has not been evaluated to differentiate liver metastases and benign lesions in patients with malignant melanoma. ...
... Various postprocessing techniques provide additional information to distinguish lesions by analyzing these parameters. Former studies have demonstrated DECT's advantage in distinguishing benign lesions from malignant ones compared to conventional single-energy CT [14,18,[29][30][31]. However, there are insufficient studies that performed multiparametric analysis based on the Z and Rho of each tissue type using the application class of special postprocessing software (Rho/Z maps), especially in patients with malignant melanoma. ...
Objectives: The aim of this study is to evaluate the diagnostic accuracy of dual-energy computed tomography (DECT)-based Rho/Z maps in differentiating between metastases and benign liver lesions in patients diagnosed with malignant melanoma compared to conventional CT value measurements. Methods: This retrospective study included 73 patients (mean age, 70 ± 13 years; 43 m/30 w) suffering from malignant melanoma who had undergone third-generation DECT as part of tumor staging between December 2017 and December 2021. For this study, we measured Rho (electron density) and Z (effective atomic number) values as well as Hounsfield units (HUs) in hypodense liver lesions. Values were compared, and diagnostic accuracy for differentiation was computed using receiver operating characteristic (ROC) curve analyses. Additional performed MRI or biopsies served as a standard of reference. Results: A total of 136 lesions (51 metastases, 71 cysts, and 14 hemangiomas) in contrast-enhanced DECT images were evaluated. The most notable discrepancy (p < 0.001) between measured values and the highest diagnostic accuracy for distinguishing melanoma metastases from benign cysts was observed for the Z (0.992; 95% CI, 0.956–1) parameters, followed by Rho (0.908; 95% CI, 0.842–0.953) and finally HU120kV (0.829; 95% CI, 0.751–0.891). Conversely, when discriminating between liver metastases and hemangiomas, the HU120kV parameters showed the most significant difference (p < 0.001) and yielded the highest values for diagnostic accuracy (0.859; 95% CI, 0.740–0.937), followed by the Z parameters (0.790; 95% CI, 0.681–0.876) and finally the Rho values (0.621; 95% CI, 0.501–0.730). Conclusions: Rho and Z measurements derived from DECT allow for improved differentiation of liver metastases and benign liver cysts in patients with malignant melanoma compared to conventional CT value measurements. In contrast, in differentiation between liver hemangiomas and metastases, Rho/Z maps show inferior diagnostic accuracy. Therefore, differentiation between these two lesions remains a challenge for CT imaging.
... Dual-energy CT (DECT) has become an integral component of clinical practice, offering a wide array of applications across various medical domains, including musculoskeletal, vascular, cardiac, gastrointestinal, genitourinary, and neurological fields [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Notably, recent advancements have highlighted its significant advantages in the evaluation of oncology patients [20][21][22]. ...
... The low monoenergetic images also provide the highest contrast-to-noise ratio and signal-to-noise ratio for the detection of pancreatic ductal adenocarcinoma (PDAC). In fact, many studies have demonstrated that lesion conspicuity was significantly higher in monoenergetic images at 55 keV, with overall increased reader confidence at 70 keV [11,22,92,93]. Gupta et al. have found that the use of VMI with 50 keV and 70 keV images plays a very important role since it could be a problem-solver in cases of pancreatic adenocarcinoma [78]. ...
Dual-energy CT (DECT) is an innovative technology that is increasingly widespread in clinical practice. DECT allows for tissue characterization beyond that of conventional CT as imaging is performed using different energy spectra that can help differentiate tissues based on their specific attenuation properties at different X-ray energies. The most employed post-processing applications of DECT include virtual monoenergetic images (VMIs), iodine density maps, virtual non-contrast images (VNC), and virtual non-calcium (VNCa) for bone marrow edema (BME) detection. The diverse array of images obtained through DECT acquisitions offers numerous benefits, including enhanced lesion detection and characterization, precise determination of material composition, decreased iodine dose, and reduced artifacts. These versatile applications play an increasingly significant role in tumor assessment and oncologic imaging, encompassing the diagnosis of primary tumors, local and metastatic staging, post-therapy evaluation, and complication management. This article provides a comprehensive review of the principal applications and post-processing techniques of DECT, with a specific focus on its utility in managing oncologic patients.
... The enhanced capabilities of dual-energy computed tomography (DECT) in detecting and characterizing tumors have been widely acknowledged in the genitourinary, gastroenterology, and pulmonary fields [59][60][61][62]. ...
Purpose of Review
This review aims to consolidate knowledge and recent research findings related to the potential clinical applications of dual-energy computed tomography (DECT) for the identification and characterization of bone lesions. The purpose is to explore the advantages of DECT over traditional imaging techniques in musculoskeletal radiology, particularly in the context of oncologic care for cancer patients.
Recent Findings
DECT has emerged as a state-of-the-art imaging technique that offers significant benefits in the detection and assessment of skeletal lesions. It provides improved sensitivity in identifying hidden lesions, including metastatic ones that are often concealed within the marrow space. DECT's advanced technology enables material decomposition and color-coded overlays, allowing for the differentiation of various types of soft tissue mineralization and the evaluation of bone marrow edema and infiltrative skeletal neoplasms. Furthermore, DECT can aid in distinguishing between malignant and benign skeletal lesions, providing valuable diagnostic information for treatment planning and patient care.
Summary
Dual-energy computed tomography (DECT) is a promising tool in musculoskeletal radiology, particularly for oncologic care and disease staging in cancer patients. DECT's ability to differentiate, enhance, or suppress various types of tissues through material decomposition and spectral data analysis makes it a valuable imaging technique for identifying and characterizing bone lesions. With its advanced technology, DECT offers improved sensitivity in detecting hidden lesions and provides valuable diagnostic information without increasing radiation exposure. By addressing the limitations of other imaging modalities, DECT has the potential to enhance patient care and improve outcomes in the field of musculoskeletal radiology.
... Polychromatic effects such as photon starvation from dense materials or metals [3] and beam hardening can even complicate the retrieval of a material's average LAC [4]. Some substances like tumor and fibrous tissues, soft tissues [5][6][7][8] and liquid and homemade explosives [9] can possess overlapping averaged LACs, giving low contrast information between different materials. This limits the efficiency of single energy CT for material identification based on the contrast between the averaged LACs of materials. ...
We propose a method for estimation of material's electron density parameter (e) using multi-energy x-ray Computed Tomography (CT). Multi-energy CT uses a photon counting detector (PCD) to measure a material's linear attenuation coefficient (LAC) at multiple energies with the simultaneous data acquisition. The physical effects in the PCD such as charge sharing and photon pileup result in spectral distortions of the energy spectrum. Corrects for such distortions are performed with a correction algorithm. A custom laboratory instrument for multi-energy CT is used to experimentally validate the method. The identification efficiency is evaluated for different numbers of energy channels. When using 15 energy channels without inter-gaps the method gives a relative deviation of 1.8% for estimation of e , for materials in the range of 0.43 ≤ e ≤ 1.06 e − mol∕cm 3 .
... In recent years, numerous technological developments and innovations have emerged in CT imaging, leading to the better radiological management of patients [1][2][3][4][5][6][7][8][9][10][11]. Among them, dual-energy spectral imaging has emerged to improve the detection and characterization of lesions, particularly abdominal lesions [12][13][14][15]. Its basic principle is to acquire or detect two photon spectra at low-and high-energy levels to help identify the tissue attenuation coefficients. ...
The purpose of this study was to compare the quality of low-energy virtual monoenergetic images (VMIs) obtained with three Dual-Energy CT (DECT) platforms according to the phantom diameter. Three sections of the Mercury Phantom 4.0 were scanned on two generations of split-filter CTs (SFCT-1st and SFCT-2nd) and on one Dual-source CT (DSCT). The noise power spectrum (NPS), task-based transfer function (TTF), and detectability index (d’) were assessed on VMIs from 40 to 70 keV. The highest noise magnitude values were found with SFCT-1st and noise magnitude was higher with DSCT than with SFCT-2nd for 26 cm (10.2% ± 1.3%) and 31 cm (7.0% ± 2.5%), and the opposite for 36 cm (−4.2% ± 2.5%). The highest average NPS spatial frequencies and TTF values at 50% (f50) values were found with DSCT. For all energy levels, the f50 values were higher with SFCT-2nd than SFCT-1st for 26 cm (3.2% ± 0.4%) and the opposite for 31 cm (−6.9% ± 0.5%) and 36 cm (−5.6% ± 0.7%). The lowest d’ values were found with SFCT-1st. For all energy levels, the d’ values were lower with DSCT than with SFCT-2nd for 26 cm (−6.2% ± 0.7%), similar for 31 cm (−0.3% ± 1.9%) and higher for 36 cm (5.4% ± 2.7%). In conclusion, compared to SFCT-1st, SFCT-2nd exhibited a lower noise magnitude and higher detectability values. Compared with DSCT, SFCT-2nd had a lower noise magnitude and higher detectability for the 26 cm, but the opposite was true for the 36 cm.
... [5][6][7][8][9][10] Both types of images improve the detection and characterization of lesions, particularly in the liver, kidney, and adrenals. 5,7,11,12 Many dual-energy CT (DECT) platforms have been developed to obtain both the low-and high-energy photon spectra required to create spectral images. 2,[13][14][15][16][17][18] Among these DECT platforms, the split filter CT (SFCT) platform has been developed. ...
Background
Recently, a second generation of split filter dual‐energy CT (SFCT) platform has been developed. The thicknesses of the gold and tin filters used to obtain both low‐ and high‐energy spectra have been changed. These differences in filter thickness may affect the spectral separation between the two spectra and thus the quality of spectral images.
Purpose
To compare the spectral performance of two Split‐Filter Dual‐Energy CT systems (SFCT‐1st and SFCT‐2nd) on virtual monoenergetic images (VMIs) and iodine map.
Methods
A Multi‐Energy CT phantom was scanned on two SFCT with a tube voltage of 120 kVp for both systems (SFCT‐1st‐120 and SFCT‐2nd‐120) and 140 kVp only for the second generation (SFCT‐2nd‐140). Acquisitions were performed on the phantom with a CTDIvol close to 11 mGy. Noise power spectrum (NPS) and task‐based transfer function (TTF) were evaluated on VMIs from 40 to 70 keV. A detectability index (d’) was computed to assess the detection of two contrast‐enhanced lesions on VMIs. Hounsfield Unit (HU) accuracy was assessed on VMIs and the accuracy of iodine concentration was assessed on iodine maps.
Results
For all keV, noise magnitude values were lower with the SFCT‐2nd‐120 than with the SFCT‐1st‐120 (on average: ‐22.5 ± 2.9%) and higher with the SFCT‐2nd‐140 than with the SFCT‐2nd‐120 (on average: 25.0 ± 6.2%). Average NPS spatial frequencies (fav) were lower with the SFCT‐1st‐120 than with the SFCT‐2nd‐120 (‐6.0 ± 0.5%) and the SFCT‐2nd‐140 (‐3.6 ± 1.6%). Similar TTF50% values were found for both systems and both kVp for blood and iodine inserts at 2 mg/mL (0.29 ± 0.01 mm⁻¹) and at 4 mg/mL (0.31 ± 0.01 mm⁻¹). d’ values peaked at 40 keV for the SFCT‐2nd and at 70 keV for the SFCT‐1st. Highest d’ values were found for the SFCT‐2nd‐120 for both simulated lesions. Accuracy of HU values and iodine concentration was higher with the SFCT‐2nd than with the SFCT 1st.
Conclusion
Compared to the SFCT‐1st, with similar spatial resolution and noise texture values, the SFCT‐2nd‐120 exhibited the lowest values for noise magnitude, the highest detectability index values, and more accurate HU values and iodine concentrations.
... These include improved bleeding conspicuity [3][4][5] using iodine material density and low monoenergetic images, lesion characterization [6][7][8], and image quality [9][10][11]. Clinical applications of DECT in oncology [12], vascular imaging [13], and routine imaging for improved characterization of incidental findings [14,15] have been well reported. As an example, low monoenergetic CT images, such as 50-keV, can increase liver bleeding conspicuity acquired in the portal venous phase. ...
Purpose
To develop and assess the utility of synthetic dual-energy CT (sDECT) images generated from single-energy CT (SECT) using two state-of-the-art generative adversarial network (GAN) architectures for artificial intelligence-based image translation.
Methods
In this retrospective study, 734 patients (389F; 62.8 years ± 14.9) who underwent enhanced DECT of the chest, abdomen, and pelvis between January 2018 and June 2019 were included. Using 70-keV as the input images (n = 141,009) and 50-keV, iodine, and virtual unenhanced (VUE) images as outputs, separate models were trained using Pix2PixHD and CycleGAN. Model performance on the test set (n = 17,839) was evaluated using mean squared error, structural similarity index, and peak signal-to-noise ratio. To objectively test the utility of these models, synthetic iodine material density and 50-keV images were generated from SECT images of 16 patients with gastrointestinal bleeding performed at another institution. The conspicuity of gastrointestinal bleeding using sDECT was compared to portal venous phase SECT. Synthetic VUE images were generated from 37 patients who underwent a CT urogram at another institution and model performance was compared to true unenhanced images.
Results
sDECT from both Pix2PixHD and CycleGAN were qualitatively indistinguishable from true DECT by a board-certified radiologist (avg accuracy 64.5%). Pix2PixHD had better quantitative performance compared to CycleGAN (e.g., structural similarity index for iodine: 87% vs. 46%, p-value < 0.001). sDECT using Pix2PixHD showed increased bleeding conspicuity for gastrointestinal bleeding and better removal of iodine on synthetic VUE compared to CycleGAN.
Conclusions
sDECT from SECT using Pix2PixHD may afford some of the advantages of DECT.
... In recent years, numerous technological developments and innovations have emerged in CT imaging, leading to better radiological management of patients [1][2][3][4][5][6][7][8][9][10][11]. Among them, dual-energy spectral imaging has emerged to improve the detection and characterization of lesions, particularly abdominal lesions [12][13][14][15]. Its basic principle is to acquire or detect two photon spectra at low-and high-energy levels to help identify tissue attenuation coefficients. ...
To compare the quality of low-energy VMIs obtained with three DECT platforms according to phantom diameter. Three sections of the Mercury Phantom 4.0 were scanned on two generations of split-filter CTs (SFCT-1st and SFCT-2nd) and on one Dual-source CT (DSCT). Noise power spectrum (NPS), task-based transfer function (TTF) and detectability index (d’) were assessed on VMIs from 40 to 70keV. Highest noise magnitude values were found with SFCT-1st and noise magnitude was higher with DSCT than with SFCT-2nd for 26-cm (10.2±1.3%) and 31-cm (7.0±2.5%), and the opposite for 36-cm (-4.2±2.5%). The highest average NPS spatial frequencies and TTF values at 50% (f50) values were found with DSCT. For all energy levels, f50 values were higher with SFCT-2nd than SFCT-1st for 26-cm (3.2±0.4%) and the opposite for 31-cm (-6.9±0.5%) and 36-cm (-5.6±0.7%). The lowest d’ values were found with SFCT-1st. For all energy levels, d’ values were lower with SFCT-2nd than with DSCT for 26-cm (-6.2±0.7%), similar for 31-cm (-0.3±1.9%) and higher for 36-cm (5.4±2.7%). In conclusion, compared to SFCT-1st, SFCT-2nd exhibited lower noise magnitude and higher detectability values. Compared with DSCT, SFCT-2nd had lower noise magnitude and higher detectability for the 26-cm but the opposite was true for the 36-cm.
