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Evaluation of a kidney lesion in dual energy CT (window width, 350 HU; window level, 40 HU) a Averaged image. Note the lesion in the left kidney with inhomogeneous density and central inclusion of fat. With reference to the virtual unenhanced image (c), the lesion does contain contrast material. Overall, an angiomyolipoma can be suspected. b Averaged image with colorcoded iodine distribution. The lesion does contain iodine. c Virtual unenhanced image. The noise and resolution are not sufficient to detect the small central inclusion of fat. d Real pre-contrast scan
Source publication
The aim of this study was to assess the feasibility of a differentiation of iodine from other materials and of different body tissues using dual energy CT. Ten patients were scanned on a SOMATOM Definition Dual Source CT (DSCT; Siemens, Forchheim, Germany) system in dual energy mode at tube voltages of 140 and 80 kVp and a ratio of 1:3 between tube...
Citations
... Two decades after the advent of spectral computed tomography (CT) modalities [1][2][3][4][5][6] and the introduction of material-selective algorithms [7][8][9][10][11][12][13][14][15], energy-discriminating photon-counting detector (PCD) CT systems have become commercially available [16,17]. Analogous to established dual-energy techniques on energy-integrating detectors, such as dual-source, kV-switching, or the use of dual-layer detectors, threshold image acquisition with PCDs allows two-material decomposition of the input images into a pair of base materials. ...
... We defined the input CNR based on the T1 image because it is created by all incident photons on the detector. Thus, the input CNR in in one ROI with average CT number quadruple = ( 1 2 3 4 ) in one image slice reads in = 1 √ in (9) where in is the image noise standard deviation in the T1 image measured in the voxels of the ROI. The output CNR out in the same ROI of the -th material map with average CE reads out = √ out (10) where out is the image noise standard deviation measured analogously to in . ...
Photon-counting CT systems generally allow for acquiring multiple spectral datasets and thus for decomposing CT images into multiple materials. We introduce a prior knowledge-free deterministic material decomposition approach for quantifying three material concentrations on a commercial photon-counting CT system based on a single CT scan. We acquired two phantom measurement series: one to calibrate and one to test the algorithm. For evaluation, we used an anthropomorphic abdominal phantom with inserts of either aqueous iodine solution, aqueous tungsten solution, or water. Material CT numbers were predicted based on a polynomial in the following parameters: Water-equivalent object diameter, object center-to-isocenter distance, voxel-to-isocenter distance, voxel-to-object center distance, and X-ray tube current. The material decomposition was performed as a generalized least-squares estimation. The algorithm provided material maps of iodine, tungsten, and water with average estimation errors of 4% in the contrast agent maps and 1% in the water map with respect to the material concentrations in the inserts. The contrast-to-noise ratio in the iodine and tungsten map was 36% and 16% compared to the noise-minimal threshold image. We were able to decompose four spectral images into iodine, tungsten, and water.
... The importance of DECT is reflected by the 2015 EULAR/ACR classification criteria for gout, were gout diagnosis is enabled without invasive joint aspiration using clinical and laboratory parameters as well as DECT beside ultrasound and x-ray [29]. As a well-established tool to detect peripheral MSU deposits, its application on the vascular system has recently been proven feasible [30][31][32][33]. ...
Purpose of Review
To highlight novel findings in the detection of monosodium urate deposits in vessels using dual energy computed tomography, and to discuss the potential clinical implications for gout and hyperuricemia patients.
Recent Findings
Gout is an independent risk factor for cardiovascular disease. However, classical risk calculators do not take into account these hazards, and parameters to identify patients at risk are lacking. Monosodium urate measured by dual energy computed tomography is a well-established technology for the detection and quantification of monosodium urate deposits in peripheral joints and tendons. Recent findings also suggest its applicability to identify vascular urate deposits.
Summary
Dual energy computed tomography is a promising tool for detection of cardiovascular monosodium urate deposits in gout patients, to better delineate individuals at increased risk for cardiovascular disease.
... DECT shows greater image enhancement at low tube voltages (15). Karino et al. (16) analyzed energy spectral images of virtual monochromatic images (VMI) with energy levels ranging from 40 to 140 KeV in increments of 1 keV gradient and found that a VMI of 63 KeV significantly improved the overall image quality and BM boundary display. ...
Brain metastases (BMs) are the most prevalent intracranial malignant tumors in adults and are the leading cause of mortality attributed to malignant brain diseases. Radiotherapy (RT) plays a critical role in the treatment of BMs, with local RT techniques such as stereotactic radiosurgery (SRS)/stereotactic body radiotherapy (SBRT) showing remarkable therapeutic effectiveness. The precise determination of gross tumor target volume (GTV) is crucial for ensuring the effectiveness of SRS/SBRT. Multimodal imaging techniques such as CT, MRI, and PET are extensively used for the diagnosis of BMs and GTV determination. With the development of functional imaging and artificial intelligence (AI) technology, there are more innovative ways to determine GTV for BMs, which significantly improve the accuracy and efficiency of the determination. This article provides an overview of the progress in GTV determination for RT in BMs.
... The increasing clinical adoption of dual-energy computed tomography technology in clinical practice has enhanced our comprehension of tissue composition. DECT leverages a material decomposition algorithm to precisely quantify iodine concentration and fat fraction by analyzing the differential absorption characteristics across two X-ray beam energies [10]. Our study underscores the pivotal role of DECT in providing deeper insight into lymph node characteristics, particularly in breast cancer patients. ...
Purpose: To evaluate the diagnostic performance of a dual-energy computed tomography (DECT)-based material decomposition algorithm for iodine quantification and fat fraction analysis to detect lymph node metastases in breast cancer patients. Materials and Methods: 30 female patients (mean age, 63.12 ± 14.2 years) diagnosed with breast cancer who underwent pre-operative chest DECT were included. To establish a reference standard, the study correlated histologic repots after lymphadenectomy or confirming metastasis in previous/follow-up examinations. Iodine concentration and fat fraction were determined through region-of-interest measurements on venous DECT iodine maps. Receiver operating characteristic curve analysis was conducted to identify the optimal threshold for differentiating between metastatic and non-metastatic lymph nodes. Results: A total of 168 lymph nodes were evaluated, divided into axillary (metastatic: 46, normal: 101) and intramammary (metastatic: 10, normal: 11). DECT-based fat fraction values exhibited significant differences between metastatic (9.56 ± 6.20%) and non-metastatic lymph nodes (41.52 ± 19.97%) (p < 0.0001). Absolute iodine concentrations showed no significant differences (2.25 ± 0.97 mg/mL vs. 2.08 ± 0.97 mg/mL) (p = 0.7999). The optimal fat fraction threshold for diagnosing metastatic lymph nodes was determined to be 17.75%, offering a sensitivity of 98% and a specificity of 94%. Conclusions: DECT fat fraction analysis emerges as a promising method for identifying metastatic lymph nodes, overcoming the morpho-volumetric limitations of conventional CT regarding lymph node assessment. This innovative approach holds potential for improving pre-operative lymph node evaluation in breast cancer patients, offering enhanced diagnostic accuracy.
... It uses two different X-ray spectra to acquire two datasets of the same anatomic region, allowing analysis of energy-dependent changes in the attenuation of different materials. This has led to a transition from CT attenuation-based imaging to material-specific or spectral imaging that provides specific information about the composition of materials [3]. ...
To quantitatively evaluate the possible advantages of quantifying and differentiating various soft tissues using virtual monochromatic images (VMI) derived from different dual-energy computed tomography (DECT) technologies. This study involved four DECT scanners with different technologies. CIRS phantom images were acquired in single-energy (SECT) and DECT modes with each scanner. The analysis focused on five equivalent soft-tissue inserts: adipose, breast, liver, muscle, and bone (200 mg). The signal-to-noise ratio (SNR) was calculated for each equivalent soft-tissue insert. Finally, the contrasts of tissue pairs between DECT and SECT images were compared using Wilcoxon signed-rank tests adjusted for multiple comparisons. Average CT numbers and noise showed a significant difference pattern between DECT with respect to SECT for each CT scanner. Generally, energy levels of 70 keV or higher led to improved SNR in VMI for most of the equivalent soft-tissue inserts. However, energy levels of 40–50 keV showed significantly higher contrasts in most of the equivalent soft-tissue insert pairs. DECT images at low energies, especially at 40–50 keV, outperform SECT images in discriminating soft tissues across all four DECT technologies. The combined use of DECT images reconstructed at different energy levels provides a more comprehensive set of information for diagnostic and/or radiotherapy evaluation compared to SECT. Some differences between scanners are evident, depending on the DECT acquisition technique and reconstruction method.
... This eliminates the need for a pre-contrast scan, thereby reducing radiation exposure [9,67]. In the context of vascular tumors, analyzing enhancement patterns on iodine map images proves invaluable for diagnosis, offering a more comprehensive view of iodine distribution compared to standard conventional CT scans [68][69][70]. Furthermore, the vascular application of DECT enhances the clarity of vascular supply delineation by eliminating osseous structures from the scanned image. ...
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.
... In particular, for a given acquisition energy, CT numbers depend on both magnitudes, Z ef and e W r , so tissue differentiation is limited by the lack of information provided by single-energy CT (SECT) acquisitions. Performing CT acquisitions at multiple energies could decouple the influence of density and chemical composition, providing additional information (Johnson et al 2007). Indeed, Hounsfield already mentioned the potential of using two images to enhance tissues that cannot be differentiated using just one image (Hounsfield 1973). ...
We introduce a new calibration method for Dual Energy CT (DECT) based on Material Decomposition (MD) maps, specifically iodine and water MD maps. The aim of this method is to provide the first DECT calibration based on MD maps. The experiments were carried out using a General Electric (GE) Revolution CT scanner with ultra-fast kV switching and used a Density Phantom by GAMMEX for calibration and evaluation.
The calibration process involves several steps. First, we tested the ability of MD values to reproduce Hounsfield Unit (HU) values of SECT acquisitions and it was found that the errors were below 1\%, validating their use for HU reproduction. Next, the different definitions of computed $Z$ values were compared and the robustness of the approach based on the materials' composition was confirmed. Finally, the calibration method was compared with a previous method by Bourque et al., providing a similar level of accuracy and superior performance in terms of precision.
Overall, this novel DECT calibration method offers improved accuracy and reliability in determining tissue-specific physical properties. The resulting maps can be valuable for proton therapy treatments, where precise dose calculations and accurate tissue differentiation are crucial for optimal treatment planning and delivery.
... 2,3 DECT exploits the differential energy-dependent attenuation profiles exhibited by different tissues acquired with two x-ray energy levels, typically at 80-90 and 140-150 keV. [2][3][4] The attenuation of X-ray photons during a CT scan comprises predominantly of photoelectric effect and Compton scatter. Compton scatter is less applicable in DECT as it is not affected by the X-ray beam energy whereas photoelectric effect plays a more important role in DECT. ...
... Each material has a specific DEI, and the differentiation is superior if the differences between the DEIs are greater. 4 Apart from the atomic number, the molecular structure of certain tissues, such as collagen and urate, can also display distinctive spectral properties with varying energy levels. 4 Post processing tools are required to generate clinically useful material specific or energy specific images from the DECT datasets. ...
... 4 Apart from the atomic number, the molecular structure of certain tissues, such as collagen and urate, can also display distinctive spectral properties with varying energy levels. 4 Post processing tools are required to generate clinically useful material specific or energy specific images from the DECT datasets. ...
Dual-energy computed tomography (DECT) is an exciting application in CT technology conferring many advantages over conventional single energy CT at no additional with comparable radiation dose to the patient. Various emerging and increasingly established clinical DECT applications in musculoskeletal (MSK) imaging such as bone marrow edema detection, metal artifact reduction, monosodium urate (MSU) analysis, as well as collagen analysis for ligamentous, meniscal and disc injuries are made possible through its advanced DECT post processing capabilities. These provide superior information on tissue composition, artifact reduction and image optimisation. Newer DECT applications to evaluate fat fraction for sarcopenia, Rho/Z application for soft tissue calcification differentiation, 3D rendering, and AI integration are being assessed for future use. In this article we will discuss the established and developing applications of DECT in the setting of MSK radiology as well as the basic principles of dual-energy CT which facilitate them.
... Efforts to reduce dose also include the use of dual-energy CT (DECT) techniques during the arterial or delayed phase. DECT allows the acquisition of two sets of images at different energy spectra in a single scan, allowing the differentiation of materials based on their attenuation coefficients at different energies [5]. By accurately mapping of specific elements, material decomposition allows additional reconstructions, such as virtual elimination of elements. ...
... One of the advantages of DECT in vascular studies is the ability to generate virtual non-contrast (VNC) reconstructions. These are derived from dual-energy data by removing the iodine signal from the original images, simulating the appearance of non-contrast images without the need for an additional scan, thus reducing radiation dose by replacing the non-contrast scan with VNC images [5,6]. ...
Purpose: To assess the diagnostic accuracy of BMI-adapted, low-radiation and low-iodine dose, dual-source aortic CT for endoleak detection in non-obese and obese patients following endovascular aortic repair. Methods: In this prospective single-center study, patients referred for follow-up CT after endovascular repair with a history of at least one standard triphasic (native, arterial and delayed phase) routine CT protocol were enrolled. Patients were divided into two groups and allocated to a BMI-adapted (group A, BMI < 30 kg/m2; group B, BMI ≥ 30 kg/m2) double low-dose CT (DLCT) protocol comprising single-energy arterial and dual-energy delayed phase series with virtual non-contrast (VNC) reconstructions. An in-patient comparison of the DLCT and routine CT protocol as reference standard was performed regarding differences in diagnostic accuracy, radiation dose, and image quality. Results: Seventy-five patients were included in the study (mean age 73 ± 8 years, 63 (84%) male). Endoleaks were diagnosed in 20 (26.7%) patients, 11 of 53 (20.8%) in group A and 9 of 22 (40.9%) in group B. Two radiologists achieved an overall diagnostic accuracy of 98.7% and 97.3% for endoleak detection, with 100% in group A and 95.5% and 90.9% in group B. All examinations were diagnostic. The DLCT protocol reduced the effective dose from 10.0 ± 3.6 mSv to 6.1 ± 1.5 mSv (p < 0.001) and the total iodine dose from 31.5 g to 14.5 g in group A and to 17.4 g in group B. Conclusion: Optimized double low-dose dual-source aortic CT with VNC, arterial and delayed phase images demonstrated high diagnostic accuracy for endoleak detection and significant radiation and iodine dose reductions in both obese and non-obese patients compared to the reference standard of triple phase, standard radiation and iodine dose aortic CT.
... The ratio of these two attenuation coefficients allows the unique differentiation of tissues with differing atomic numbers, based on the energy-and elementdependent nature of X-ray attenuation (19,21). Hence, DECT allows for the decomposition of tissues into their constituent elements, including soft tissues (22,23). Soft tissue characterization via DECT imaging is innovative since the evaluation of soft tissue usually requires an MRI. ...
... Additionally, water/fat separation can be achieved by the XBONE sequence; this is a gradient echo-type sequence that generates two sets of images, with one containing only the fat signal and the other containing only the water signal. On the contrary, DECT allows the detection of bone edema-like lesions via a three-material decomposition algorithm (22,40). This algorithm subtracts the calcium from the cancellous bone, generating virtual non-calcium (VNCa) images to evaluate the fat and water components within the bone marrow. ...
... Of all these abnormalities that are categorized under the umbrella term "bone edema-like lesion", there was only a selected range of the abnormalities detected in every case. Furthermore, for each case, a different abnormality dominated the histological sample: hemorrhage in foot IV, fibrosis, and "true" edema in foot V. Consequently, future studies should determine the influence of the lesion characterization on the accuracy of DECT VNCa imaging since this imaging technique solely evaluates the fat and water components within the bone marrow (22,40). For example, in foot IV, the presence of iron in the hemorrhage zone in the navicular bone could be a determining factor for the increased attenuation of DECT (57). ...
Introduction
In this proof-of-concept study, the post-mortem feasibility of dual-energy computed tomography (DECT) in the detection of bone edema-like lesions in the equine foot is described in agreement with the gold standard imaging technique, which is magnetic resonance imaging (MRI).
Methods
A total of five equine cadaver feet were studied, of which two were pathological and three were within normal limits and served as references. A low-field MRI of each foot was performed, followed by a DECT acquisition. Multiplanar reformations of DECT virtual non-calcium images were compared with MRI for the detection of bone edema-like lesions. A gross post-mortem was performed, and histopathologic samples were obtained of the navicular and/or distal phalanx of the two feet selected based on pathology and one reference foot.
Results
On DECT virtual non-calcium imaging, the two pathological feet showed diffuse increased attenuation corresponding with bone edema-like lesions, whereas the three reference feet were considered normal. These findings were in agreement with the findings on the MRI. Histopathology of the two pathologic feet showed abnormalities in line with bone edema-like lesions. Histopathology of the reference foot was normal.
Conclusion
DECT virtual non-calcium imaging can be a valuable diagnostic tool in the diagnosis of bone edema-like lesions in the equine foot. Further examination of DECT in equine diagnostic imaging is warranted in a larger cohort, different locations, and alive animals.
