Single-energy Images Research Articles

Markerless tumor tracking using fast-kV switching dual-energy fluoroscopy on a benchtop system.

To evaluate markerless tumor tracking (MTT) using fast-kV switching dual-energy (DE) fluoroscopy on a bench top system. Fast-kV switching DE fluoroscopy was implemented on a bench top which includes a turntable stand, flat panel detector, and x-ray tube. The customized generator firmware enables consecutive x-ray pulses that alternate between programmed high and low energies (e.g., 60 and 120kVp) with a maximum frame rate of 15Hz. In-house software was implemented to perform weighted DE subtraction of consecutive images to create an image sequence that removes bone and enhances soft tissues. The weighting factor was optimized based on gantry angle. To characterize this system, a phantom was used that simulates the chest anatomy and tumor motion in the lung. Five clinically relevant tumor sizes (5-25mm diameter) were considered. The targets were programmed to move in the inferior-superior direction of the phantom, perpendicular to the x-ray beam, using a cos4 waveform to mimic respiratory motion. Target inserts were then tracked with MTT software using a template matching method. The optimal computed tomography (CT) slice thickness for template generation was also evaluated. Tracking success rate and accuracy were calculated in regions of the phantom where the target overlapped ribs vs spine, to compare the performance of single energy (SE) and DE imaging methods. For the 5mm target, a CT slice thickness of 0.75mm resulted in the lowest tracking error. For the larger targets (≥10mm) a CT slice thickness ≤2mm resulted in comparable tracking errors for SE and DE images. Overall DE imaging improved MTT accuracy, relative to SE imaging, for all tumor targets in a rotational acquisition. Compared to SE, DE imaging increased tracking success rate of small target inserts (5 and 10mm). For fast motion tracking, success rates improved from 23% to 64% and 74% to 90% for 5 and 10mm targets inserts overlapping ribs, respectively. For slow moving targets success rates improved from 19% to 59% and 59% to 91% in 5 and 10mm targets overlapping the ribs, respectively. Similar results were observed when the targets overlapped the spine. For larger targets (≥15mm) tracking success rates were comparable using SE and DE imaging. This work presents the first results of MTT using fast-kV switching DE fluoroscopy. Using DE imaging has improved the tracking accuracy of MTT, especially for small targets. The results of this study will guide the future implementation of fast-kV switching DE imaging using the on-board imager of a linear accelerator.

Evaluation of photon-counting spectral mammography for classification of breast microcalcifications

The purpose of this study was to evaluate the feasibility of spectral mammography using a dual-energy method to non-invasively distinguish between type I (calcium oxalate) and type II (calcium hydroxyapatite) microcalcifications. These two types of microcalcifications are difficult to differentiate owing to their similar linear attenuation coefficients. To improve the detection efficiency regarding microcalcifications, a photon-counting detector with energy discrimination capability was used, and the microcalcifications were classified using the optimal dual-energy spectrum. Two energy bins were used to obtain dual-energy images. In this study, a photon-counting spectral mammography system was simulated using Geant4 Application for Tomographic Emission (GATE) simulation tools. A cadmium zinc telluride detector with a high quantum efficiency was used in this study. The effects of classification on the density and thickness of the breast phantom were investigated. Microcalcifications of various sizes, ranging from 130 to 550 μm, were embedded in the phantom. For statistical analysis, the microcalcifications were classified as calcium hydroxyapatite or calcium oxalate based on a score calculation using the dual-energy images. According to the results, the measured contrast-to-noise ratio (CNR) of the calcium hydroxyapatite was higher than that of calcium oxalate in a single-energy image. The calcium hydroxyapatite had a higher attenuation coefficient and slightly higher contrast compared with calcium oxalate. In addition, the microcalcifications were classified into the optimal energy bin in the dual-energy images. This classification showed better performance with a high energy of 50 kVp and an energy threshold of 30 keV. This study demonstrated that using the dual-energy method could improve classification performance because the microcalcifications are affected by the density and thickness of the breast phantom. These results indicate that the classification accuracy was improved when the difference between the low-energy image and high-energy image was used. The dual-energy method can reduce the frequency of the need for biopsies and discriminate between different types of microcalcifications in mammography. These results can improve the efficiency of early breast cancer diagnosis.

Application of MRI and CT Energy Spectrum Imaging in Hand and Foot Tendon Lesions.

To deeply analyze the tendon lesions of hands and feet, the application of Computed Tomography (CT) energy spectrum imaging and magnetic resonance imaging (MRI) in anatomy and lesions is mainly studied. Firstly, the related information of the subjects is introduced in turn. Secondly, Gemstone Spectral Imaging (GSI) and MRI examinations are performed respectively. Through energy spectrum analysis software, suitable single energy value (KeV) is selected, the mixed energy image is converted into the single energy image, and a variety of image recombination methods are used to observe the energy spectrum CT image and compare the results with MRI. The results of the study show that GSI could display the morphology, continuous walking and dead point of the tendon, especially the three-dimensional spatial relationship of the tendon, bone and muscle, which is superior to MRI. There is no statistically significant difference between GSI and MRI in the display of tendon rupture, thickening, deletion and compression. And GSI is not as clear as MRI in the display of tendon adhesion, degeneration and tendon sheath lesions, and the difference is statistically significant. Therefore, MRI is still the first choice in hand and foot tendon lesions, especially in the display of early pathological changes of the tendon and tendon sheath diseases, as well as the evaluation of postoperative functional rehabilitation of the tendon. And CT energy spectrum imaging, as a new imaging mode, can clearly show the anatomy of normal tendon of hand and foot and most tendon lesions, especially in the observation of tendon morphology, which has a high diagnostic value.

Imaging ionomer in fuel cell catalyst layers with synchrotron nano transmission x-ray microscopy

This work presents a novel characterization method for distinguishing ionomer phase within porous composite catalyst layer. Quantifying ionomer distribution in a catalyst layer of polymer electrolyte fuel cells (PEFCs) is critical to understanding the morphological and transport properties of this key component. Current methods to image ionomer rely on staining it with heavy ions, such as cesium, Cs, to enable detection with hard X-rays, however if the catalyst layer contains electrocatalyst, such as platinum, Pt, then the challenge is to distinguish between Cs-stained ionomer and Pt. These two materials have very similar X-ray attenuation coefficients. Using synchrotron transmission x-ray microscopy (TXM) and two energy imaging, above and below Pt electrocatalyst absorption edge, the ionomer distribution is quantified. The method is applied to a PEFC catalyst layer and compared against the method of single energy imaging, which is not able to separate the two phases.

Micro-CT myelography using contrast-enhanced digital subtraction: feasibility and initial results in healthy rats.

The spinal subarachnoid space (SSAS) is vital for neural performance. Although models of spinal diseases and trauma are used frequently, no methods exist to obtain high-resolution myelograms in rodents. Thereby, our aim was to explore the feasibility of obtaining high-resolution micro-CT myelograms of rats by contrast-enhanced dual-energy (DE) and single-energy (SE) digital subtraction. Micro-CT contrast-enhanced DE and SE imaging protocols were implemented with live adult rats (total of 18 animals). For each protocol, contrast agents based on iodine (Iomeron® 400 and Fenestra® VC) and gold nanoparticles (AuroVist™ 15nm) were tested. For DE, images at low- and high-energy settings were acquired after contrast injection; for SE, one image was acquired before and the other after contrast injection. Post-processing consisted of region of interest selection, image registration, weighted subtraction, and longitudinal alignment. High-resolution myelograms were obtained with contrast-enhanced digital subtraction protocols. After qualitative and quantitative (contrast-to-noise ratio) analyses, we found that the SE acquisition protocol with Iomeron® 400 provides the best images. 3D contour renderings allowed visualization of SSAS and identification of some anatomical structures within it. This in vivo study shows the potential of SE contrast-enhanced myelography for imaging SSAS in rat. This approach yields high-resolution 3D images without interference from adjacent anatomical structures, providing an innovative tool for further assessment of studies involving rat SSAS.

Estimation of myocardial fibrosis in humans with dual energy CT

BackgroundThe current clinical standard for in vivo imaging of myocardial fibrosis is contrast-enhanced cardiac magnetic resonance (CMR). We sought to validate a novel non-contrast dual energy computed tomography (DECT) method to estimate myocardial fibrosis in patients undergoing CMR with contrast. MethodsAll subjects underwent non-contrast, prospectively-triggered cardiac DECT on a single source scanner with interleaved acquisition between tube voltages of 80 and 140 kVp. Monochromatic images were reconstructed at 11 energies spanning 40–140 keV; a region of interest (ROI) was drawn in the mid-inferoseptal segment, recording mean attenuation value in the ROI, at each energy level. Comparison was made to data from single energy (70 keV) image data. Linear discriminant analysis (LDA) was performed to compare the predictive capability of single vs. multi-energy inferoseptal segment CT attenuation on myocardial fibrosis by both visually assessed LGE (absent/present fibrosis) and CMR T1 mapping-derived myocardial extracellular volume fraction (ECV). ResultsThe multi-energy CT/LDA approach performed better than a single energy approach to discriminate among LGE-CMR classes of present/absence myocardial fibrosis severity, demonstrating correct classification rates of 89% and 71%, respectively. The multi-energy CT/LDA approach also performed better in correctly discriminating normal from elevated ECV, doing so in 89% of patients vs. correct distinction of normal/elevated ECV in only 70% using the single energy approach. ConclusionsNon-contrast cardiac DECT with multi-energy analysis better classifies myocardial fibrosis and extracellular volume compared to what is feasible with non-contrast single energy cardiac CT. These data support further evaluation of this approach to noninvasively assess myocardial fibrosis.

Determination of Optimal Image Type and Lowest Detectable Concentration for Iodine Detection on a Photon Counting Detector-Based Multi-Energy CT System.

Photon counting detector (PCD) based multi-energy CT is able to generate different types of images such as virtual monoenergetic images (VMIs) and material specific images (e.g., iodine maps) in addition to the conventional single energy images. The purpose of this study is to determine the image type that has optimal iodine detection and to determine the lowest detectable iodine concentration using a PCD-CT system. A 35 cm body phantom with iodine inserts of 4 concentrations and 2 sizes was scanned on a research PCD-CT system. For each iodine concentration, 80 repeated scans were performed and images were reconstructed for each energy threshold. In addition, VMIs at different keVs and iodine maps were also generated. CNR was measured for each type of images. A channelized Hotelling observer was used to assess iodine detectability after being validated with human observer studies, with area under the ROC curve (AUC) as a figure of merit. The agreement between model and human observer performance indicated that model observer could serve as an effective approach to determine optimal image type for the clinical practice and to determine the lowest detectable iodine concentration. Results demonstrated that for all size and concentration combinations, VMI at 70 keV had similar performance as that of threshold low images, both of which outperformed the iodine map images. At the AUC value of 0.8, iodine concentration as low as 0.2 mgI/cc could be detected for an 8 mm object and 0.5 mgI/cc for a 4 mm object with a 5 mm slice thickness.

Impact of Photon Counting Detector Technology on kV Selection and Diagnostic Workflow in CT.

The purpose of this study is to determine the optimal iodine contrast-to-noise ratio (CNR) achievable for different patient sizes using virtual-monoenergetic-images (VMIs) and a universal acquisition protocol on photon-counting-detector CT (PCD-CT), and to compare results to those from single-energy (SE) and dual-source-dual-energy (DSDE) CT. Vials containing 3 concentrations of iodine were placed in torso-shaped water phantoms of 5 sizes and scanned on a 2nd generation DSDE scanner with both SE and DE modes. Tube current was automatically adjusted based on phantom size with CTDIvol ranging from 5.1 to 22.3 mGy. PCD-CT scans were performed at 140 kV, 25 and 75 keV thresholds, with CTDIvol matched to the SE scans. DE VMIs were created and CNR was calculated for SE images and DE VMIs. The optimal kV (SE) or keV (DE VMI) was chosen at the point of highest CNR with no noticeable artifacts. For 10 mgI/cc vials in the 35 cm phantom, the optimal CNR of VMIs on PCD (22.6@50keV) was comparable to that of the best DSDE protocol (23.9@50keV) and was higher than that of the best SE protocol (19.7@80kV). In general, the difference of optimal CNR between PCD and SE increased with phantom size, with PCD 50 keV VMIs having an equivalent CNR (0.6% difference) with that of SE at the 25 cm phantom and 57% higher CNR at the 45 cm phantom. PCD-CT demonstrated comparable iodine CNR of VMIs to that of DSDE across patient sizes. Whereas SE and DSDE CT exams require use of patient-size-specific acquisitions settings, our findings point to the ability of PCD-CT to simplify protocol selection, using a single VMI keV setting (50 keV), acquisition kV (140 kV), and energy thresholds (25 and 75 keV) for all patient sizes, while achieving optimal or near optimal iodine CNR values.

Significance of an Advanced Image-Based Virtual Monoenergetic Reconstruction of Dual Source Dual-Energy CT Data at Low keV Increases Image Quality for Portal Vein System of Pancreatic Cancer Patients

Purpose: To explore the significance of dual-source computed tomography (DECT) virtual monoenergetic reconstructions technology in improving image quality for portal vein system of pancreatic cancer patients. Materials and methods: 47 patients with clinically suspected pancreatic cancer (all confirmed by pathology) were collected. Routine plain scan was performed with Siemens Force dual-source dual-energy CT followed by 3 scans respectively carried out in arterial phase, portal phase and delayed phase. Traditional virtual monoenergetic reconstructions (Mono_E) and new generation of virtual monoenergetic reconstructions (Mono+) were respectively performed on portal vein images to obtain virtual single energy images including Mono_ E70 keV, Mono_E 55 keV and Mono+ 70 keV and Mono+ 55 keV. The signal-to-noise ratio (SNR) and noise of portal vein, normal pancreatic tissues and pancreatic lesions of 100 kV, Mono_E and Mono+ images were compared. In addition, the contrast noise ratio of portal vein and lesions as well as pancreatic tissues and lesions (CNR PV, CNRtumor) were also compared. At the same time, two imaging physicians with rich clinical experiences read the films and scored the images of each group by using the 5-point scoring method. Results: Mono+ 55 keV images including SNRpv, SNRpanc, SNRtumor, Noise, CNRpv, CNRtumor were statistically different from 100 KV images and Mono_E images (P keV image score also had the highest score, which had statistical significance (P keV images had the best quality. Conclusion: The new generation of virtual Mono+ post-treatment can reduce image noise. Low energy Mono+ images can improve the contrast between pancreatic cancer lesions and portal of pancreatic cancer patients.

Application of an Advanced Image-Based Virtual Monoenergetic Reconstruction of Dual Source Dual-Energy CT Data at Low keV Increases Image Quality for Esophageal Cancer Patients Imaging

Purpose: To explore the significance of dual-source computed tomography (DECT) virtual monoenergetic reconstructions technology in improving the imaging quality of esophageal cancer patients. Materials and methods: 68 patients with clinically suspected esophageal cancer (all confirmed by pathology) were collected. Routine plain scan was performed with SIEMENS Force dual-energy CT and then dual-phase scans were performed. The venous phase images were respectively subjected to traditional virtual monoenergetic reconstructions (Mono_E) and new generation virtual monoenergetic reconstructions (Mono+). Mono_E 55 keV and Mono+ 55 keV virtual single-energy images were obtained respectively. The signal-to-noise ratio (SNR) of normal esophageal tissue and esophageal cancer lesions, noise and contrast noise ratio (CNR tumor) of normal esophageal tissue and esophageal cancer lesions were compared among 100 kV images, Mono_E images and Mono+ images. At the same time, two imaging physicians read the films and scored the images of each group by using a 5-point scoring method. Results: Mono+ 55 keV images, SNR, SNRtumor, noise and CNRtumor were statistically different from those of 100 kV images and Mono_E images (P Mono+ 55 keV images also had the highest subjective score, with statistical significance (P 55 keV images had the best quality. Conclusion: The new generation of virtual monoenergetic reconstructions post-processing (Mono+) could reduce image noise and improve the contrast between esophageal cancer lesions and normal esophageal tissues, which was of great significance to improve the imaging quality of esophageal cancer patients and improve the early detection rate of esophageal cancer.

Application of Dual-Energy CT Non-Linear Fusion Technology in Improving CTA Image Quality of Renal Cancer

Objective: To explore the significance of dual-energy CT non-linear fusion technique in improving the quality of CTA image of renal cancer. Methods: The CTA images of 100 patients who had been confirmed by pathology as renal cancer were collected and were randomly divided into experimental group and control group with 50 cases respectively. The two groups of patients were treated with iodine concentration of 300 mg/ml and 350 mg/ml non-ionic contrast agent, with a dosage of 1.5 ml/kg and an injection rate of 4 ml/s. The contrast agent intelligently tracking method was adopted bolus. The control group used the conventional CTA scanning, with a reference tube voltage/tube current of 100 kv/ref150 mas. The experimental group adopted the double energy scanning, with ball tube A and ball tube B. The reference tube voltage/tube current was 100 kv/ref250 mas and sn150 kv/ref125 mas respectively. The images of the experimental group were non-linear fused to obtain the Mono+ 55 kev single-energy images. The CT value, SNR contrast ratio of the abdominal aorta, renal artery and tumor tissue of the experimental group images and the 100 KV images and the Mono+ 55 kev images of the control group were compared. The objective evaluation and subjective evaluation of the image quality of the three groups of images was performed. Results: The results showed that the 100 kV images of the experimental group were statistically different from those of the control group (P05) in CT value, SNR and CNR (P 0.05). The subjective evaluation of image quality showed that there was no significant difference between Mono+ 55 kev images and control group images, and the quality of Mono+ 55 kev images was higher than that of experimental group 100 kV images. Conclusion: The dual-energy CT non-linear fusion technique can improve the quality of CTA image in patients with renal cancer, and it is possible to obtain high quality CTA images with low iodine concentration contrast agent.

Non-contrast estimation of diffuse myocardial fibrosis with dual energy CT: A phantom study

BackgroundEstimation of diffuse myocardial fibrosis, substrate for adverse events such as heart failure and arrhythmias in patients with various cardiac disorders, is presently done by histopathology or cardiac magnetic resonance. We sought to develop a non-contrast method to estimate the amount of diffuse myocardial fibrosis leveraging dual energy computed tomography (DECT) in phantoms and a suitable small animal model. Methods and ResultsPhantoms consisted of homogenized bovine myocardium with varying amounts of Type 1 collagen. Fifteen mice underwent sham surgery, no procedure, or transverse aortic constriction (TAC) for 5 or 8 weeks to produce moderate or severe fibrosis, respectively. Phantoms and ex vivo mouse hearts were imaged on a single source, DECT scanner equipped with kVp switching. Monochromatic images were reconstructed at 40–140 keV. Linear discriminant analysis (LDA) was performed on mean myocardial CT numbers derived from single energy (70 keV) images as well as images reconstructed across multiple energies. Classification of myocardial fibrosis severity as low, moderate or severe was more often correct using the multi-energy CT/LDA approach vs. single energy CT/LDA in both phantoms (80.0% vs. 70.0%) and mice (93.3% vs. 33.3%). ConclusionsDECT myocardial imaging with multi-energy analysis better classifies myocardial fibrosis severity compared to a single energy-based approach. Non-contrast DECT can accurately and non-invasively estimate the extent of diffuse myocardial fibrosis in phantom and animal models. These data support further evaluation of this approach for in vivo myocardial fibrosis estimation.

Megavoltage cargo radiography with dual energy material decomposition

Megavoltage (MV) radiography has important applications in imaging large cargos for detecting illicit materials. A useful feature of MV radiography is the possibility of decomposing and quantifying materials with different atomic numbers. This can be achieved by imaging cargo at two different X-ray energies, or dual energy (DE) radiography. The performance of both single energy and DE radiography depends on beam energy, beam filtration, radiation dose, object size, and object content. The purpose of this work was to perform comprehensive qualitative and quantitative investigations of the image quality in MV radiography depending on the above parameters. A digital phantom was designed including Fe background with thicknesses of 2cm, 6cm, and 18cm, and materials samples of Polyethylene, Fe, Pb, and U. The single energy images were generated at x-ray beam energies 3.5MV, 6MV, and 9MV. The DE material decomposed images were generated using interlaced low and high energy beams 3.5/6MV and 6/9MV. The X-ray beams were filtered by low-Z (Polyethylene) and high-Z (Pb) filters with variable thicknesses. The radiation output of the accelerator was kept constant for all beam energies. The image quality metrics was signal-to-noise ratio (SNR) of the particular sample over a particular background. It was found that the SNR depends on the above parameters in a complex way, but can be optimized by selecting a particular set of parameters. For some imaging setups increased filter thicknesses, while strongly absorbing the beams, increased the SNR of material decomposed images. Beam hardening due to polyenergetic x-ray spectra resulted in material decomposition errors, but this could be addressed using region of interest decomposition. It was shown that it is not feasible to separate the materials with close atomic numbers using the DE method. Particularly, Pb and U were difficult to decompose, at least at the dose levels allowed by radiation source and safety requirements.

Dual Energy Fluoroscopy Improves the Accuracy of Template-Based Tracking in Lung Cancer Patients Receiving Stereotactic Body Radiation Therapy

Template-based matching algorithms are currently being considered for markerless motion tracking (MMT) of lung tumors using fluoroscopy. The accuracy of this match is quantified through a metric known as peak-to-side lobe ratio (PSR). A previous study has shown that template matches with PSR≥3 are significantly more accurate than those with PSR<3. The goal of this study is to evaluate the fraction of single energy (SE) fluoroscopic images, obtained in SBRT lung cancer patients, that have PSR≥3, and if the addition of dual energy (DE) subtraction fluoroscopy can increase the PSR value. Moreover, radiomic parameters from CT images are evaluated to determine if any are predictive of PSR. In this prospective study, a total of 2,448 fluoroscopy frames were acquired, at multiple imaging angles, from 8 SBRT patients with Stage IA - IIA lung cancer. Sequential 60 kVp and 120 kVp fluoroscopic sequences were acquired and aligned based on respiratory signal. DE fluoroscopic sequences were created using a frame-by-frame weighted logarithmic subtraction. Separately, a template was derived from the contoured gross tumor volume (GTV) on the CT simulation scan. A template-based matching algorithm was used to track tumor motion throughout the DE and SE (120 kVp) fluoroscopy sequences. This algorithm shifts the template across the image and calculates the normalized cross correlation (NCC) between the template and image, resulting in a match score surface. The offset at which the NCC has the maximum value (i.e., the position of the peak of the surface) represents the potential target position. The strength of this peak relative to NCC values away from the peak, called side lobe values, is quantified by the PSR. Radiomic parameters using the GTV from the planning CT scans were examined to determine correlation with the PSR values. Approximately 68% of the SE fluoroscopic images had PSR ≥3. Of the SE images with PSR <3, 79.5% were obtained at an oblique imaging angle, while the remaining were obtained at an anterior imaging angle. By adding DE fluoroscopy, over 86% of the images obtained PSR ≥3 (P < 0.001). Of the 23 unique imaging sessions, SE imaging alone allowed for tracking in over 80% of the images in 12/23 (52%) sessions vs. 18/23 (78%) when combined with DE fluoroscopy (P = 0.12). In those cases where DE imaging increased the PSR to ≥3, the change in template positioning was 1.14 +/- 0.61 mm. Of the 200 unique radiomic parameters analyzed, “energy” was predictive of PSR value, having a Pearson’s correlation coefficient = 0.846 and 0.841 for SE and DE, respectively. The PSR value provides an independent metric for assessing the accuracy of a template match when used in conjunction with MMT. The addition of DE imaging to SE fluoroscopy increases the fraction of images with PSR >3, thus improving the overall accuracy of template matching.

Quality of routine diagnostic abdominal images generated from a novel detector-based spectral CT scanner: a technical report on a phantom and clinical study.

To evaluate the image quality of routine diagnostic images generated from a novel detector-based spectral detector CT (SDCT) and compare it with CT images obtained from a conventional scanner with an energy-integrating detector (Brilliance iCT), Routine diagnostic (conventional/polyenergetic) images are non-material-specific images that resemble single-energy images obtained at the same radiation, METHODS: ACR guideline-based phantom evaluations were performed on both SDCT and iCT for CT adult body protocol. Retrospective analysis was performed on 50 abdominal CT scans from each scanner. Identical ROIs were placed at multiple locations in the abdomen and attenuation, noise, SNR, and CNR were measured. Subjective image quality analysis on a 5-point Likert scale was performed by 2 readers for enhancement, noise, and image quality. On phantom studies, SDCT images met the ACR requirements for CT number and deviation, CNR and effective radiation dose. In patients, the qualitative scores were significantly higher for the SDCT than the iCT, including enhancement (4.79±0.38 vs. 4.60±0.51, p=0.005), noise (4.63±0.42 vs. 4.29±0.50, p=0.000), and quality (4.85±0.32, vs. 4.57±0.50, p=0.000). The SNR was higher in SDCT than iCT for liver (7.4±4.2 vs. 7.2±5.3, p=0.662), spleen (8.6±4.1 vs. 7.4±3.5, p=0.152), kidney (11.1±6.3 vs. 8.7±5.0, p=0.033), pancreas (6.90±3.45 vs 6.11±2.64, p=0.303), aorta (14.2±6.2 vs. 11.0±4.9, p=0.007), but was slightly lower in lumbar-vertebra (7.7±4.2 vs. 7.8±4.5, p=0.937). The CNR of the SDCT was also higher than iCT for all abdominal organs. Image quality of routine diagnostic images from the SDCT is comparable to images of a conventional CT scanner with energy-integrating detectors, making it suitable for diagnostic purposes.

Characteristics of single- and dual-photopeak energy window acquisitions with thallium-201 IQ-SPECT/CT system.

Although dual-energy (DE) acquisition with conventional 201Tl myocardial perfusion SPECT has several advantages such as improved attenuation of the inferior wall and increased acquisition counts, the characteristics of IQ-SPECT have not been fully evaluated. We evaluate the difference of characteristics between single-energy (SE) and dual-energy (DE) imaging using 201Tl myocardial IQ-SPECT. Two myocardial phantoms were created simulating normal myocardium and infarction of the inferior wall. Energy windows were set at 70keV±10% for SE, and an additional 167keV±7.5% for DE. SPECT images were reconstructed using the ordered subset conjugates gradient minimizer (OSCGM) method. We visually and quantitatively compared short-axis images of correction for no (NC), for attenuation (AC) or for both AC and scatter (ACSC) images. The average counts of SE and DE projection data were 17.5 and 20.3 counts/pixel, respectively. The DE data increased acquisition counts by approximately 16% compared with the SE data. The average visual score of normal myocardium did not differ significantly between the SE and DE images. However, the DE image of defective myocardium showed a significantly lower score in AC than SE images. The % uptake values of DE image with both NC and AC were significantly higher than those of SE images. The DE images of the inferior defective areas (segments 4 and 10) showed approximately 5-10% higher uptake compared with the SE images. The DE image with NC improved attenuation of the inferior wall. However, DE image with AC showed low defect detectability. Thus, AC should be used with SE rather than DE. Furthermore, while the SE image with ACSC can be used to detect perfusion defects, it must be interpreted carefully including the possibility of artificial inhomogeneity even in the normal myocardium.

Correlation of dual-source computed tomography/dual-energy imaging with pathological grading of lung adenocarcinoma and its clinical value.

Objective:To explore the correlation of dual-source computed tomography (DSCT)/dual-energy imaging with pathological grading of lung adenocarcinoma.Methods:A total of 47 patients with lung adenocarcinoma were selected. Tissues were histopathologically confirmed by routine DSCT scanning and dual-energy enhanced scanning. Arterial-phase and venous-phase iodine distribution images and single-energy images at 40-190 keV were obtained. The region of interest was outlined to obtain CT values. The iodine concentrations of each tumor in two phases were recorded to calculate normalized iodine concentrations (NICs).Results:The maximum diameter and minimum diameter of tumors in low differentiation (LD) group were significantly higher than those of high differentiation (HD) group (P<0.05). In LD group, 70.8% of margins were lobulated, which significantly exceeded that of HD group (30.4%) (P<0.05). Besides, 26.1% of patients in HD group were complicated with ground-glass opacity, which was significantly higher than that of LD group (4.2%) (P<0.05). In venous phase, there were significant differences between the two groups at low energy levels (40-70 keV) (P<0.05). At high energy levels (80-190 keV), the CT values of LD group were slightly higher than those of HD group. In arterial and venous phases, NICs of HD group were lower than those of LD group (P>0.05).Conclusion:HD and LD groups could be predictably distinguished by single-energy images at low energy levels (40-70 keV) in the venous phase. Quantitative analysis of NIC in the venous phase is also valuable for predicting the pathological grade of lung adenocarcinoma.

Evaluation of a template-based algorithm for markerless lung tumour localization on single- and dual-energy kilovoltage images.

To evaluate a template-based matching algorithm on single-energy (SE) and dual-energy (DE) radiographs for markerless localization of lung tumours. A total of 74 images from 17 patients with Stages IA-IV lung cancer were considered. At the time of radiotherapy treatment, gated end-expiration SE radiographs were obtained at 60 and 120 kVp at different gantry angles (33° anterior and 41° oblique), from which soft-tissue-enhanced DE images were created. A template-based matching algorithm was used to localize individual tumours on both SE and DE radiographs. Tumour centroid co-ordinates obtained from the template-matching software on both SE and DE images were compared with co-ordinates defined by physicians. The template-based matching algorithm was able to successfully localize the gross tumor volume within 5 mm on 70% (52/74) of the SE images vs 91% (66/74) of the DE images (p < 0.01). The mean vector differences between the co-ordinates of the template matched by the algorithm and the co-ordinates of the physician-defined ground truth were 3.2 ± 2.8 mm for SE images vs 2.3 ± 1.7 mm for DE images (p = 0.03). Template-based matching on DE images was more accurate and precise than using SE images. Advances in knowledge: This represents, to the authors' knowledge, the largest study evaluating template matching on clinical SE and DE images, considering not only anterior gantry angles but also oblique angles, suggesting a novel lung tumour matching technique using DE subtraction that is reliable, accurate and precise.

Rock porosity quantification by dual-energy X-ray computed microtomography

Porous media investigation by X-ray microtomography allows obtaining valuable quantitative and qualitative information, while preserving sample integrity. Modern X-ray nanotomography or Synchrotron radiation systems may distinguish structures sized only hundreds of nanometers. However, pores sized less than a few microns (microporosity) may be undetectable due to the system’s spatial resolution and noise in microfocus sources, compromising the quality of the measurement. In this study a dual-energy methodology was developed to generate density-based images from two scans made at two different voltages (80kV and 130KV) with a microfocus bench-top microtomography system. The images obtained were quantized in 256 gray levels, where the lowest value (zero) corresponded to voids and the highest value (255) corresponded to the densest regions mapped. From density images and single energy images, porosity was evaluated and compared. Results indicate that density images present better results than single energy images when both are compared with porosity obtained by the helium injection method. In addition, images acquired in dual-energy show good agreement with the sample’s real density values.

Application of spectral computed tomography dual-substance separation technology for diagnosing left ventricular thrombus.

ObjectiveTo investigate the value of spectral computed tomography (CT) dual-substance separation technology for diagnosing left ventricular (LV) thrombus.MethodsIn this observational case–control study, spectral CT scans were conducted in patients with and without LV thrombi. Densities in the regions of the LV cavity, papillary muscles and LV thrombus were observed on 140kVp mixed-energy and 70 keV single-energy images. Iodine and blood were chosen as the base material pair, the densities were observed and the iodine and blood concentrations were quantitatively measured.ResultsA total of 24 patients were enrolled in this study. On iodine-based density images, both the LV thrombus and papillary muscles showed low-attenuation shadows. On blood-based density images, comparable high-density attenuation was found in the LV thrombus and LV cavity, while relative hypodensity was noted in the papillary muscles. Iodine and blood densities were significantly lower in papillary muscles than in the LV cavity. Iodine densities were significantly lower in the LV thrombus than the LV cavity, whereas blood densities in the two areas did not differ significantly.ConclusionsSpectral CT dual-substance separation technology and its derived images of iodine- and blood- based densities provide a new, simple, and feasible semiquantitative method to detect LV thrombus that warrants further investigation.