Dual-energy CT Imaging Research Articles

Low kV versus dual-energy virtual monoenergetic CT imaging for proven liver lesions: what are the advantages and trade-offs in conspicuity and image quality? A pilot study.

Single-energy low tube potential (SE-LTP) and dual-energy virtual monoenergetic (DE-VM) CT images both increase the conspicuity of hepatic lesions by increasing iodine signal. Our purpose was to compare the conspicuity of proven liver lesions, artifacts, and radiologist preferences in dose-matched SE-LTP and DE-VM images. Thirty-one patients with 72 proven liver lesions (21 benign, 51 malignant) underwent full-dose contrast-enhanced dual-energy CT (DECT). Half-dose images were obtained using single tube reconstruction of the dual-source SE-LTP projection data (80 or 100kV), and by inserting noise into dual-energy projection data, with DE-VM images reconstructed from 40 to 70keV. Three blinded gastrointestinal radiologists evaluated half-dose SE-LTP and DE-VM images, ranking and grading liver lesion conspicuity and diagnostic confidence (4-point scale) on a per-lesion basis. Image quality (noise, artifacts, sharpness) was evaluated, and overall image preference was ranked on per-patient basis. Lesion-to-liver contrast-to-noise ratio (CNR) was compared between techniques. Mean lesion size was 1.5±1.2cm. Across the readers, the mean conspicuity ratings for 40, 45, and 50keV half-dose DE-VM images were superior compared to other half-dose image sets (p<0.0001). Per-lesion diagnostic confidence was similar between half-dose SE-LTP compared to half-dose DE-VM images (p≥0.05; 1.19 vs. 1.24-1.32). However, SE-LTP images had less noise and artifacts and were sharper compared to DE-VM images less than 70keV (p<0.05). On a per-patient basis, radiologists preferred SE-LTP images the most and preferred 40-50keV the least (p<0.0001). Lesion CNR was also higher in SE-LTP images than DE-VM images (p<0.01). For the same applied dose level, liver lesions were more conspicuous using DE-VM compared to SE-LTP; however, SE-LTP images were preferred more than any single DE-VM energy level, likely due to lower noise and artifacts.

Abstract ID: 91 Image acquisition and material differentiation for Dual Energy Computed Tomography by Monte Carlo simulations

Dual Energy Computed Tomography (DECT) is an innovative and developing technique that uses two different x-spectra to get material differentiation in diagnostic imaging [1] . As a different modality from standard CT, it requires specified phantoms for quality control. Currently, there are few phantoms specialized for DECT and its price is quite high. Therefore, the aim of this study is to simulate the CT images of a DECT phantom whose compounds are combination of thermoplastic materials that could be manufactured. The present work uses Phase Space Files (PSF) computed from PENELOPE/PenEasy Monte Carlo code as a validated X-ray source model to obtain DECT images. The simulation process is divided in two steps: the first one compute the PSFs for two different X-ray spectra and the second one simulate the radiation transport through the phantom and detectors. The particles stored in PSFs were used to compute the energy deposition in each detector after the interaction with the phantom. For each angular projection it was used one of the two PSF. As a result, two sinograms were obtained and two images were reconstructed, each one representing the attenuation properties of its respective spectrum [2] . The thermoplastic material combinations were obtained using a methodology developed by our group [3] . Differentiation characteristics of the DECT were determined for materials commonly used in clinical practice as uric acid, iodine and calcium. The results demonstrate the capabilities of DECT/MC simulation for improving material visualization and identification, development of dedicated phantoms and for educational purposes.

Assessing lung function using contrast-enhanced dual-energy computed tomography for potential applications in radiation therapy.

There is an increasing interest in the evaluation of lung function from physiological images in radiation therapy treatment planning to reduce the extent of postradiation toxicities. The purpose of this work was to retrieve reliable functional information from contrast-enhanced dual-energy computed tomography (DECT) for new applications in radiation therapy. The functional information obtained by DECT is also compared with other methods using single-energy CT (SECT) and single-photon emission computed tomography (SPECT) with CT. The differential function between left and right lung, as well as between lobes is computed for all methods. Five lung cancer patients were retrospectively selected for this study; each underwent a SPECT/CT scan and a contrast-injected DECT scan, using 100 and 140 Sn kVp. The DECT images are postprocessed into iodine concentration maps, which are further used to determine the perfused blood volume. These maps are calculated in two steps: (a) a DECT stoichiometric calibration adapted to the presence of iodine and followed by (b) a two-material decomposition technique. The functional information from SECT is assumed proportional to the HU numbers from a mixed CT image. The functional data from SPECT/CT are considered proportional to the number of counts. A radiation oncologist segmented the entire lung volume into five lobes on both mixed CT images and low-dose CT images from SPECT/CT to allow a regional comparison. The differential function for each subvolume is computed relative to the entire lung volume. The differential function per lobe derived from SPECT/CT correlates strongly with DECT (Pearson's coefficient r = 0.91) and moderately with SECT (r = 0.46). The differential function for the left lung shows a mean difference of 7% between SPECT/CT and DECT; and 17% between SPECT/CT and SECT. The presence of nonfunctional areas, such as localized emphysema or a lung tumor, is reflected by an intensity drop in the iodine concentration maps. Functional dose volume histograms (fDVH) are also generated for two patients as a proof of concept. The extraction of iodine concentration maps from a contrast-enhanced DECT scan is achieved to compute the differential function for each lung subvolume and good agreement is found in respect to SPECT/CT. One promising avenue in radiation therapy is to include such functional information during treatment planning dose optimization to spare functional lung tissues.

Multiple Myeloma and Dual-Energy CT: Diagnostic Accuracy of Virtual Noncalcium Technique for Detection of Bone Marrow Infiltration of the Spine and Pelvis

Purpose To determine the diagnostic performance of dual-energy computed tomography (CT) for detection of bone marrow (BM) infiltration in patients with multiple myeloma by using a virtual noncalcium (VNCa) technique. Materials and Methods In this prospective study, 34 consecutive patients with multiple myeloma or monoclonal gammopathy of unknown significance sequentially underwent dual-energy CT and magnetic resonance (MR) imaging of the axial skeleton. Two independent readers visually evaluated standard CT and color-coded VNCa images for the presence of BM involvement. MR imaging served as the reference standard. Analysis on the basis of the region of interest (ROI) of VNCa CT numbers of infiltrated (n = 75) and normal (n = 170) BM was performed and CT numbers were subjected to receiver operating characteristic analysis to calculate cutoff values. Results In the visual analysis, VNCa images had an overall sensitivity of 91.3% (21 of 23), specificity of 90.9% (10 of 11), accuracy of 91.2% (31 of 34), positive predictive value of 95.5% (21 of 22), and a negative predictive value of 83.3% (10 of 12). ROI-based analysis of VNCa CT numbers showed a significant difference between infiltrated and normal BM (P < .001). Receiver operating characteristic analysis revealed an area under the curve of 0.978. A cutoff of -44.9 HU provided a sensitivity of 93.3% (70 of 75), specificity of 92.4% (157 of 170), accuracy of 92.7% (227 of 245), positive predictive value of 84.3% (70 of 83), and negative predictive value of 96.9% (157 of 162) for the detection of BM infiltration. Conclusion Visual and ROI-based analyses of dual-energy VNCa images had excellent diagnostic performance for assessing BM infiltration in patients with multiple myeloma with precision comparable to that of MR imaging. © RSNA, 2017 Online supplemental material is available for this article.

Applications of Dual-Energy Computed Tomography for the Evaluation of Head and Neck Squamous Cell Carcinoma.

There are multiple emerging applications of dual-energy computed tomography (DECT) for the evaluation of pathology in the head and neck, in particular head and neck squamous cell carcinoma. Studies suggest that DECT image sets reconstructed as supplements to routine diagnostic images may improve lesion visualization, determination of tumor extent, and identification of invasion of critical anatomic structures. This article reviews the evidence for the use and potential advantages of supplementary DECT reconstructions for the evaluation of head and neck squamous cell carcinoma. A summary of potentially useful reconstructions and a suggested approach for multiparametric DECT evaluation of head and neck cancer based on current evidence are presented.

Technical Note: Comparison of megavoltage, dual-energy, and single-energy CT-based μ-maps for a four-channel breast coil in PET/MRI.

The purpose of this study was to describe and evaluate methods for calculating a megavoltage computed tomography (MVCT)-derived MR hardware attenuation map (μ-map) and dual-energy CT (DECT) for 511 keV photons. Phantom measurements were acquired on a whole-body hybrid PET/MRI system, using a four-channel receive-only MR radiofrequency (RF) breast coil. Two acquisitions were performed: with the phantoms positioned in the four-channel RF breast coil, and without the breast coil. PET attenuation from the breast coil was corrected using three different CT-derived hardware μ-maps: (a) Single-energy CT (SECT), (b) DECT, and (c) MVCT. Each attenuation-corrected (AC) PET volume was evaluated and compared with the acquisition performed without the breast coil. The breast coil attenuated PET photons by 10% overall. Threshold values were applied to the SECT μ-map to reduce the effects of metal artifacts, but overcorrection occurred in more highly attenuated regions. The DECT-derived virtual monochromatic image reduced beam-hardening artifacts, but other metal artifacts remained. Despite the remaining metal artifacts in the DECT image, it led to an improvement in the more attenuated regions. The MVCT images appear to be free from metal artifacts leading to an artifact-free μ-map and a further improvement AC-PET images. Our MVCT-based approach for creating μ-maps for MR RF coils greatly reduces artifacts produced by metal in a SECT approach. This eliminates the need for other artifact reduction methods, including the application of a threshold of narrow beam attenuation coefficients, or disassembling hardware to remove high-Z components before imaging with a kilovoltage source.

Iodine concentration calculated by dual-energy computed tomography (DECT) as a functional parameter to evaluate thyroid metabolism in patients with hyperthyroidism

BackgroundThyroid function in patients with Grave’s disease is usually evaluated by thyroid scintigraphy with radioactive iodine. Recently, dual-energy computed tomography (DECT) with two different energy X-rays can calculate iodine concentrations and can be applied for iodine measurements in thyroid glands. This study aimed to assess the potential use of DECT for the functional assessment of the thyroid gland.MethodsThirteen patients with Grave’s disease treated at our hospital from May to September 2015 were included in this retrospective study. Before treatments, all subjects had undergone both iodine scintigraphy [three and 24 h after oral administration of 123I (20 μCi)] and non-enhanced DECT. The region of interests (ROIs) were placed in both lobes of the thyroid glands, and CT values (HU: Hounsfield unit) and iodine concentrations (mg/mL) calculated from DECT images were measured. The correlation between CT values and iodine concentrations from DECT in the thyroid gland was evaluated and then the iodine concentrations were compared with radioactive iodine uptake ratios by thyroid scintigraphy.ResultsMean (±SD) 123I uptake increased from 46.3 (±22.2) % (range, 11.1–80.1) at 3 h, to 66.5 (±15.2) % (range, 40.0–86.1) at 24 h (p < 0.01). CT values ranged from 34.5 to 98.7 HU [mean: 67.8 (±18.6)], while the iodine concentrations calculated with DECT ranged from 0.0 to 1.3 mg/mL [mean: 0.5 (±0.4)]. A moderate positive correlation between CT values and the calculated iodine concentrations in the thyroid gland was seen (R = 0.429, p < 0.05). A significant negative correlation between 123I uptake at 3 h and iodine concentration by DECT were seen (R = −0.680, p < 0.05), although no correlation was observed between 123I uptake at 3 h and CT values (p = 0.087). No correlation was observed between 123I uptake at 24 h and CT values (p = 0.153) or that between 123I uptake at 24 h and iodine concentration by DECT (p = 0.073).ConclusionThe negative correlation of 123I uptake at 3 h with iodine concentration evaluated by DECT was better than that observed with simple CT value. DECT may have a potential role in the evaluation of iodine turnover in hyperthyroid patients.

Imaging the Spine with Dual-Energy CT

This review article aims to summarize the available literature regarding the utility of Dual-Energy CT (DECT) in spine imaging. DECT using virtual non-calcium images, virtual monoenergetic images, and material decomposition techniques have shown promise in bone marrow edema visualization associated with vertebral fractures, metallic artifact reduction related to spinal hardware, axial monosodium urate deposit detection, bone marrow composition evaluation, and bone marrow lesion identification. In our experience, DECT may also be an assuring technique in evaluation of disc degeneration, and disc herniation. DECT imaging of the spine has numerous clinical applications, potential advantages over single-energy CT and other imaging modalities, and future promising avenues.

Iterative reconstruction for dual energy CT with an average image-induced nonlocal means regularization

Reducing radiation dose in dual energy computed tomography (DECT) is highly desirable but it may lead to excessive noise in the filtered backprojection (FBP) reconstructed DECT images, which can inevitably increase the diagnostic uncertainty. To obtain clinically acceptable DECT images from low-mAs acquisitions, in this work we develop a novel scheme based on measurement of DECT data. In this scheme, inspired by the success of edge-preserving non-local means (NLM) filtering in CT imaging and the intrinsic characteristics underlying DECT images, i.e. global correlation and non-local similarity, an averaged image induced NLM-based (aviNLM) regularization is incorporated into the penalized weighted least-squares (PWLS) framework. Specifically, the presented NLM-based regularization is designed by averaging the acquired DECT images, which takes the image similarity within the two energies into consideration. In addition, the weighted least-squares term takes into account DECT data-dependent variance. For simplicity, the presented scheme was termed as ‘PWLS-aviNLM’. The performance of the presented PWLS-aviNLM algorithm was validated and evaluated on digital phantom, physical phantom and patient data. The extensive experiments validated that the presented PWLS-aviNLM algorithm outperforms the FBP, PWLS-TV and PWLS-NLM algorithms quantitatively. More importantly, it delivers the best qualitative results with the finest details and the fewest noise-induced artifacts, due to the aviNLM regularization learned from DECT images. This study demonstrated the feasibility and efficacy of the presented PWLS-aviNLM algorithm to improve the DECT reconstruction and resulting material decomposition.

Characteristics of Chinese Costal Cartilage and Costa Calcification Using Dual-Energy Computed Tomography Imaging

To assess characteristics of Chinese costal cartilage and costa calcification using Dual-Energy computed tomography(DECT). 154 patients who underwent chest DECT scanning were included in our study. They were divided into following groups: less than 30 years old, 31–40 years old, 41–50 years old, 51–60 years old and over 60 years old. The sixth, seventh and eighth costal cartilages and costas were evaluated. Calcification patterns of cartilage were classified as central(C), peripheral(P), mixed(M) and no calcification(N) types. Calcification degree of cartilage was distinguished as 1(0–25%), 2(26–50%) and 3(>50%). CT value, calcium and water concentrations were measured in costal cartilage, cortical or cancellous bone respectively. An increasing C pattern of cartilage was displayed in females, while P type preferred in males as age increased. Calcification degree generally changed from 1 to 2 or 3 in females. CT value and calcium concentration of cartilage went through a gradual rising course and peaked in their 40–50 years, while those two indices of cancellous bone decreased gradually since their 50 years in females. The findings suggest a gradual calcification of the costal cartilage took place before 40–50 years old and a sharp bone loss of the costa happened after 40–50 years old in females.

Quantitative assessment of the degree of differentiation in colon cancer with dual-energy spectral CT.

To evaluate dual-energy spectral CT imaging in evaluating the degree of differentiation in colon cancer. Forty-seven colon cancer patients underwent spectral CT during arterial phase (AP) and portal venous phase (PP), and were characterized pathologically differentiated to well-differentiated (A, n=18) and poorly differentiated or undifferentiated carcinoma group (B, n=29). Lesion iodine concentration (IC) was measured and normalized to that of aorta (NIC). CT numbers were measured and the slope (λ HU) of the spectral HU curve was calculated. These parameters were statistically compared between the two groups. ROC curves were used to evaluate their diagnostic efficacies. There were significant differences in IC (1.01±0.20 vs. 1.59±0.57mg/ml), NIC (0.12±0.03 vs. 0.19±0.09), λ HU (1.41±0.29 vs. 2.03±0.85), and CT number at 70keV (48.61±9.03HU vs. 63.97±15.86HU) between groups A and B in AP (p<0.05), but no difference in PP. Using IC=1.13mg/ml in AP as the threshold, one obtained a sensitivity of 81.8% and a specificity of 71.4% for differentiating well-differentiated from poorly differentiated or undifferentiated carcinoma. These values were statistically higher than those (64.7% and 62.3%) using CT number at 70keV. Spectral CT imaging parameters (IC, NIC, and λ HU) in AP provide improved accuracy for evaluating the degrees of differentiation in colon cancer than CT number at 70keV.

Multimaterial Decomposition Algorithm for the Quantification of Liver Fat Content by Using Fast-Kilovolt-Peak Switching Dual-Energy CT: Clinical Evaluation.

Purpose To assess the clinical accuracy and reproducibility of liver fat quantification with the multimaterial decomposition (MMD) algorithm, comparing the performance of MMD with that of magnetic resonance (MR) spectroscopy by using liver biopsy as the reference standard. Materials and Methods This prospective study was approved by the institutional ethics committee, and patients provided written informed consent. Thirty-three patients suspected of having hepatic steatosis underwent non-contrast material-enhanced and triple-phase dynamic contrast-enhanced dual-energy computed tomography (CT) (80 and 140 kVp) and single-voxel proton MR spectroscopy within 30 days before liver biopsy. Percentage fat volume fraction (FVF) images were generated by using the MMD algorithm on dual-energy CT data to measure hepatic fat content. FVFs determined by using dual-energy CT and percentage fat fractions (FFs) determined by using MR spectroscopy were compared with histologic steatosis grade (0-3, as defined by the nonalcoholic fatty liver disease activity score system) by using Jonckheere-Terpstra trend tests and were compared with each other by using Bland-Altman analysis. Real non-contrast-enhanced FVFs were compared with triple-phase contrast-enhanced FVFs to determine the reproducibility of MMD by using Bland-Altman analyses. Results Both dual-energy CT FVF and MR spectroscopy FF increased with increasing histologic steatosis grade (trend test, P < .001 for each). The Bland-Altman plot of dual-energy CT FVF and MR spectroscopy FF revealed a proportional bias, as indicated by the significant positive slope of the line regressing the difference on the average (P < .001). The 95% limits of agreement for the differences between real non-contrast-enhanced and contrast-enhanced FVFs were not greater than about 2%. Conclusion The MMD algorithm quantifying hepatic fat in dual-energy CT images is accurate and reproducible across imaging phases. © RSNA, 2017 Online supplemental material is available for this article.

Calcium Crystal Deposition in Patients of Knee Osteoarthritis (OA) Using Ultrasonography and Dual Energy Computed Tomography

Purpose: Calcium Crystal Deposition is common in OA knee. This study looked for Calcium crystal deposition in Osteoarthritis knee by different methodologies which included Dual Energy Computed Tomography, Ultrasonography, Digital X-ray and Synovial fluid examination by Polarized light microscopy. Methods: 32 patients of knee OA Kellgren and Lawrence grade II and III (Sex ratio F = 21 M = 11, mean age 59.9, Range 43–76 years, mean BMI 26.7, Range BMI 16.9–40.1)were enrolled in this study. Patients with Synovial Chondromatosis were excluded. X-ray of knees was done in weight bearing position. Ultrasonography of knee joints was done by using multifrequency linear array transducer on Logiq E, GE Medical Systems Ultrasound, B mode gray scale with dynamic range of 40–50 dB, GS frequency of 11–13 MHz and GS gain of 60 dB. Knee joint was kept in maximum flexion for femoral condyle cartilage and 45 degree flexion for menisci, patellar tendon, collateral ligaments and supra patellar soft tissues. Presence of hyperechoic aggregates, intra cartilage calcifications were looked for in above mentioned sites. Femoral condylar cartilage was also looked for presence of Double / Triple contour sign. Synovial effusion was tapped in 9 patients for microscopic examination by polarized light microscopy for CPP crystals. 17 patients agreed for Dual energy computed tomography (DECT) and their right Knees were scanned for any calcifications in the joint other than the bones and Osteophytes. Results: Of X-rays of knees of 32 patients, 32 (100%) showed osteophytes, 14 (43.8%) cartilage calcification, 5 (15.6%) meniscal calcification, 16 (50%) soft tissue calcification, 1 (3.1%) blood vessel calcification, 27 (82.3%) joint space narrowing and 2 (6.3%) erosions. Ultrasonograpic finding showed osteophytes in 30 (93.8%), cartilage calcification in 24 (75%) (Double / triple contour sign in 5 (15.6%)), meniscal calcification in 30 (93.8%) soft tissue calcifications in 3 (9.4%) and erosions in 14 (43.8%). DECT images of 17 patients were observed in 17 knees in 25 sub regions and showed calcification within and around the tibio-femoral and patello-femoral joints in 15 (88.2%) knees. 41.2% had hyaline cartilage, 78.6% cruciate ligaments, 23.5% medial collateral ligament and 5.9% joint capsule calcifications. Nine patients had inflammation in the knee joint. These patients were subjected to Synovial Fluid aspiration. 4 out of these 9 showed presence of CPP crystals. Out of these 9 patients, 4 patients had meniscal calcification, 8 patients had cruciate ligament calcification, all 9 patients had cartilage calcification, and none had capsule calcification. Conclusions: Nearly all patients with KL grade II/III knee OA had calcium deposits in the knee. DECT is a more useful tool for describing calcium crystal deposition in the knee as compared to X-ray, ultrasonography and synovial fluid examination. Calcium crystal deposition by DECT was seen in 15 (88.2%) patients. All modalities are complementary to each other. While USG was better than X-Rays to show Meniscal and Cartilage calcifications DECT was particularly useful to detect Cruciate Ligament Calcifications.

O2-2-7 - Different diagnosis with Dual energy CT imaging between hemorrhage and contrast agents for acute revascularization therapy patients

O2-2-7 - Different diagnosis with Dual energy CT imaging between hemorrhage and contrast agents for acute revascularization therapy patients

Preliminary study on the differentiation between parapelvic cyst and hydronephrosis with non-calculous using only pre-contrast dual-energy spectral CT scans

To investigate the value of using the quantitative parameters from only the pre-contrast dual-energy spectral CT imaging for distinguishing between parapelvic cyst and hydronephrosis with non-calculous (HNC). This retrospective study was approved by the institutional review board. 28 patients with parapelvic cyst and 24 patients with HNC who underwent standard pre-contrast and multiphase contrast-enhanced dual-energy spectral CT imaging were retrospectively identified. The parapelvic cyst and HNC were identified using the contrast-enhanced scans, and their CT number in the 70-keV monochromatic images, effective atomic number (Zeff), iodine concentration (IC) and water concentration in the pre-contrast images were measured. The slope of the spectral curve (λ) was calculated. The difference in the measurements between parapelvic cyst and HNC was statistically analyzed using SPSS® v. 19.0 (IBM Corp., New York, NY; formerly SPSS Inc., Chicago, IL) statistical software. Receiver-operating characteristic analysis was performed to assess the diagnostic performance. The CT numbers in the 70-keV images, Zeff and IC values were statistically different between parapelvic cyst and HNC (all p < 0.05). The sensitivity, specificity and accuracy of these parameters for distinguishing between parapelvic cyst and HNC were 89.2%, 73.3% and 82.1%; 86.5%, 43.3% and 67.2%; 91.9%, 40.0% and 68.7%; and 64.9%, 73.3% and 83.6%, respectively, and the combined specificity was 92.9%. There was no statistical difference in λ between the two groups (p > 0.05). The quantitative parameters obtained in the pre-contrast dual-energy spectral CT imaging may be used to differentiate between parapelvic cyst and HNC. Advances in knowledge: The pre-contrast dual-energy spectral CT scans may be used to screen parapelvic cysts for patients who are asymptomatic, thereby avoiding contrast-enhanced CT or CT urography examination for these patients to reduce ionizing radiation dose and contrast dose.

Total variation superiorization in dual-energy CT reconstruction for proton therapy treatment planning

Proton therapy is a precise form of radiotherapy in which the range of an energetic beam of protons within a patient must be accurately known. The current approach based on single-energy computed tomography (SECT) can lead to uncertainties in the proton range of approximately 3%. This range of uncertainty may lead to under-dosing of the tumour or over-dosing of healthy tissues. Dual-energy CT (DECT) theoretically has the potential to reduce these range uncertainties by quantifying electron density and the effective atomic number. In practice, however, DECT images reconstructed with filtered backprojection (FBP) tend to suffer from high levels of noise. The objective of the current work was to examine the effect of total variation superiorization (TVS) on proton therapy planning accuracy when compared with FBP. A virtual CT scanner was created with the Monte Carlo toolkit Geant4. Tomographic images were reconstructed with FBP and TVS combined with diagonally relaxed orthogonal projections (TVS-DROP). A total variation minimization (TVM) filter was also applied to the image reconstructed with FBP (FBP-TVM). Quantitative accuracy and variance of proton relative stopping power (RSP) derived from each image set was assessed. Mean RSPs were comparable with each image; however, the standard deviation of pixel values with TVS-DROP was reduced by a factor of 0.44 compared with the FBP image and a factor of 0.66 when compared with the FBP-TVM image. Proton doses calculated with the TVS-DROP image set were also better able to predict a reference dose distribution when compared with the FBP and FBP-TVM image sets. The study demonstrated the potential advantages of TVS-DROP as an image reconstruction method for DECT applied to proton therapy treatment planning.

Recent progress on X-ray security inspection technologies

Emerging terrorist attacks seriously impacted the global security situation which brings unprecedented challenges to public transportation. Effectual anti-terrorist ways to protect personal safety and assets security become an important global demand. Consequently, to improve security inspection capabilities with state-of-art technology has long been a serious issue and hot research topic. Recent years, with the rapid development of X-ray detection technology, utilizing X-rays to inspect hidden explosives and contrabands in cargo, luggage, vehicle and on human body become both effective and efficient. Based on different X-ray interaction behaviors with matter, a variety of inspection techniques have been researched and developed which show great potentials for security applications. This paper provides a general review on different X-ray inspection techniques such as X-ray transmission imaging, backscatter imaging, phase-contrast imaging, spectral imaging, CT reconstruction, X-ray diffraction and so on. Basic physical mechanisms, research progresses and application features are investigated. And outlooks to new technologies and applications are given. X-ray transmission imaging detects the attenuation of X-ray flux while penetrating objects. The transmission image has a strong discrimination for high-density materials with strong X-ray absorption, such as guns, knives, grenades, detonators and other high atomic number items. Dual-energy X-ray imaging is an important complement that provides preliminary material classification capability. The technology has been widely used for sea freight cargo and passenger luggage inspection. X-ray back-scatter imaging detects X-rays that reflects from the scanned objects (e.g., vehicle, container and human body). It is good for imaging low density (or low atomic number) materials. The source and detectors of the scanning device are usually designed on one side of the target object, and a rotating wheel with pencil beam collimators is the key to scan in a point-by-point method. Computed tomography (CT) inspection system generates volumetric image of scanned item. It provides high resolution 3D inner structures nondestructively and without overlap. Due to the rapid development in CT reconstruction theory, various applications for security inspection have emerged. Hot research and development topics include material classification method, dual-energy and multi-energy CT imaging, non-spiral trajectory CT scan, artifacts correction and scan speed improvement. X-ray diffraction (XRD) technique has been widely used to identify minerals and other crystalline materials. It also shows good ability for detecting drug, explosives and hazardous liquids in security examination. Photo-counting detectors are utilized to measure scatter flux on different photon energy levels to form diffraction spectrum. Currently research on XRD for security application is focused on improving signal-to-noise ratio, reducing scanning time, material recognition method and system design. Phase-contrast imaging (PCI) calculates X-ray phase-shift when traversing the item. For low atomic number materials the cross section of the phase-shift can achieve up to 103 times larger than the one of attenuation. Thus it gains much better image contrast for fruits, clothes, drugs, liquids and other low atomic number items. Grating-based imaging has been regarded as the most promising PCI method because it is a first approach that requires only conventional X-ray source rather than synchrotron or micro-focus X-ray sources. Preliminary research work can be found on the security application potentials of grating-based PCI systems and methods.

Joint Segmentation and Material Recognition in Dual-Energy CT Images

Joint Segmentation and Material Recognition in Dual-Energy CT Images

Role of Dual Energy Computed Tomography Imaging in the Diagnosis of Gout

Gout is a well-known inflammatory arthritis and affects four percent of the United States population. It results from the deposition of uric acid crystals in joints, tendons, bursae, and other surrounding tissues. Prevalence of gout has increased in the recent decade. Gout is usually seen in conjunction with other chronic comorbid conditions like cardiac disease, metabolic syndrome, and renal disease. The diagnosis of this inflammatory arthritis is confirmed by visualization of monosodium urate (MSU) crystals in the synovial fluid. Though synovial fluid aspiration is the standard of care, it is often deferred because of inaccessibility of small joints, patient assessment during intercritical period, or procedural inexperience in a primary care office. Dual energy computed tomography (DECT) is a relatively new imaging modality which shows great promise in the diagnosis of gout. It is a good noninvasive alternative to synovial fluid aspiration. DECT is increasingly useful in diagnosing cases of gout where synovial fluid fails to demonstrate monosodium urate crystals. In this article, we will review the mechanism, types, advantages, and disadvantages of DECT.

Xenon-Enhanced Dual-Energy CT Imaging in Combined Pulmonary Fibrosis and Emphysema.

BackgroundLittle has been reported on the feasibility of xenon-enhanced dual-energy computed tomography (Xe-DECT) in the visual and quantitative analysis of combined pulmonary fibrosis and emphysema (CPFE).ObjectivesWe compared CPFE with idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD), as well as correlation with parameters of pulmonary function tests (PFTs).MethodsStudied in 3 groups were 25 patients with CPFE, 25 with IPF without emphysema (IPF alone), 30 with COPD. Xe-DECT of the patients’ entire thorax was taken from apex to base after a patient’s single deep inspiration of 35% stable nonradioactive xenon. The differences in several parameters of PFTs and percentage of areas enhanced by xenon between 3 groups were compared and analyzed retrospectively.ResultsThe percentage of areas enhanced by xenon in both lungs were calculated as CPFE/IPF alone/COPD = 72.2 ± 15.1% / 82.2 ± 14.7% /45.2 ± 23.2%, respectively. In the entire patients, the percentage of areas enhanced by xenon showed significantly a positive correlation with FEV1/FVC (R = 0.558, P < 0.0001) and %FEV1, (R = 0.528, P < 0.0001) and a negative correlation with %RV (R = -0.594, P < 0.0001) and RV/TLC (R = -0.579, P < 0.0001). The percentage of areas enhanced by xenon in patients with CPFE showed significantly a negative correlation with RV/TLC (R = -0.529, P = 0.007). Xenon enhancement of CPFE indicated 3 different patterns such as upper predominant, diffuse, and multifocal defect. The percentage of areas enhanced by xenon in upper predominant defect pattern was significantly higher than that in diffuse defect and multifocal defect pattern among these 3 different patterns in CPFE.ConclusionThe percentage of areas enhanced by xenon demonstrated strong correlations with obstructive ventilation impairment. Therefore, we conclude that Xe-DECT may be useful for distinguishing emphysema lesion from fibrotic lesion in CPFE.