Spectral Computed Tomography Imaging Research Articles

Application of low dose computed tomography spectral imaging combined with adaptive statistical iterative reconstruction techniques in rabbit VX2 liver tumor model

Application of low dose computed tomography spectral imaging combined with adaptive statistical iterative reconstruction techniques in rabbit VX2 liver tumor model

Optimal monochromatic images of abdominal arteries with low concentrations of contrast agents in spectral computed tomography imaging

To explore the application of optimal monochromatic images according to computed tomography (CT) values of conventional CT scans with high concentration contrast agent and the feasibility in guiding abdominal arteries imaging with low concentration contrast. From March 2013 to February 2014, 160 patients of suspected celiac disease with a body mass index (BMI) of >25 kg/m(2) underwent spectral CT scan. And they were randomly divided into two groups. In group A (n = 61), 270 mgI/ml low concentrations of contrast agents and spectral CT imaging; in group B (n = 99), 350 mgI/ml high concentrations of contrast agents and 120 kVp scan. For CT values of the first measurement of abdominal aorta B group of patients, the average CT value was calculated . The optimal monochromatic images of group A according to CT values of group B were reconstructed and 70 keV images (group C) also reconstructed. The CT values of hepatic, splenic, right renal and superior mesenteric arteries were measured and contrast to noise ratios (CNRs) calculated. CT values and CNR were compared through t test on independent samples. P > 0.05 indicated no significant difference. Mean CT value of abdominal aorta was (422 ± 65) HU in group B. And optimal keV was (67 ± 5) keV in group A. CT values of abdominal aorta and its branches showed no statistical significance; the CNRs of abdominal aorta and its branches showed statistical significance. The scoring consistency between two observers was excellent and the score (4.1 ± 0.9 vs 4.2 ± 0.7) showed no significant difference (P > 0.05). GSI abdominal scans with low concentration contrast may obtain better image qualities compared to conventional CTA of high concentration. And (67 ± 5) keV is recommended.

Spectral CT using multiple balanced K-edge filters.

Our goal is to validate a spectral computed tomography (CT) system design that uses a conventional X-ray source with multiple balanced K-edge filters. By performing a simultaneously synthetic reconstruction in multiple energy bins, we obtained a good agreement between measurements and model expectations for a reasonably complex phantom. We performed simulation and data acquisition on a phantom containing multiple rods of different materials using a NeuroLogica CT scanner. Five balanced K-edge filters including Molybdenum, Cerium, Dysprosium, Erbium, and Tungsten were used separately proximal to the X-ray tube. For each sinogram bin, measured filtered vector can be defined as a product of a transmission matrix, which is determined by the filters and is independent of the imaging object, and energy-binned intensity vector. The energy-binned sinograms were then obtained by inverting the transmission matrix followed by a multiplication of the filter measurement vector. For each energy bin defined by two consecutive K-edges, a synthesized energy-binned attenuation image was obtained using filtered back-projection reconstruction. The reconstructed attenuation coefficients for each rod obtained from the experiment was in good agreement with the corresponding simulated results. Furthermore, the reconstructed attenuation coefficients for a given energy bin, agreed with National Institute of Standards and Technology reference values when beam hardening within the energy bin is small. The proposed cost-effective system design using multiple balanced K-edge filters can be used to perform spectral CT imaging at clinically relevant flux rates using conventional detectors and integrating electronics.

Differential diagnosis of pancreatic serous oligocystic adenoma and mucinous cystic neoplasm with spectral CT imaging: Initial results

To investigate the imaging characteristics of pancreatic serous oligocystic adenoma (SOA) and mucinous cystic neoplasms (MCNs) using spectral computed tomography (CT) and to evaluate whether quantitative information derived from spectral imaging can improve the differential diagnosis of these diseases. From February 2010 to June 2013, 44 patients (24 SOAs and 20 MCNs) who underwent spectral CT imaging were included in the study. Conventional characteristics and quantitative parameters were compared between the two disease groups. Logistic regression was used for multiparametric analysis. The receiver-operating characteristic curve was used to evaluate the diagnostic performance of single parameter and multiparametric analysis. Two radiologists diagnosed the diseases blinded and independently, without and with the information of the statistical analysis. Tumour location, contour, size, and monochromatic CT values at 40 keV to 70 keV, iodine concentration, and effective atomic number (effective-Z) in the late arterial phase were the independent factors correlated with category. Multiparametric analysis with logistic regression showed that tumour size, location, and contour were the most effective variations, and obtained an area under the ROC curve (AUC) of 0.934. With the knowledge of statistical analysis, the accuracy of the first reader increased from 70.5% to 86.4%, and the accuracy of the second reader increased from 81.8% to 90.9%. Although CT spectral imaging provided additional information and multiparametric analysis obtained better performance than single-parameter analysis in differentiating MCNs from SOAs, multiparametric analysis with the combination of quantitative parameters derived from CT spectral imaging did not improve the diagnostic performance. Tumour size, location, and contour played an important role in differentiating MCNs from SOAs.

Usefulness of Dual-Energy Computed Tomography Imaging in the Differential Diagnosis of Sellar Meningiomas and Pituitary Adenomas: Preliminary Report

ObjectiveTo quantitatively assess the imaging characteristics of sellar lesion in dual-energy computed tomography (CT) imaging for differentiation of sellar meningiomas and pituitary adenomas during the arterial phase (AP) and venous phase (VP).Materials and Methods51 patients with sellar/parasellar tumors (33 macroadenomas and 18 meningiomas) were examined with CT spectral imaging during the AP and the VP. Iodine concentrations were derived from iodine-based material-decomposition CT images and normalized to the iodine concentration in the aorta. The difference in Normalized iodine concentrations (NICs), HU curve slope (λHU), and mean CT values of lesions between the AP and VP were calculated. The two-sample t test was performed to compare quantitative parameters between sellar meningiomas and pituitary adenomas.ResultsNICs, λHU, and mean CT values in patients with sellar meningiomas differed significantly from those in patients with pituitary adenomas: Mean NICs were 43.52 mg/mL±1.35 versus 9.23 mg/mL ±2.44, respectively, during the AP and 52.13 mg/mL ±1.04 versus 24.37 mg/mL ±2.23 respectively, during the VP. λHU were −3.03±3.42 versus −0.53±0.23, respectively, during the AP and −2.96±0.41 versus −0.47±0.25, respectively, during the VP. Mean CT values were 193.63±2.08 versus 63.98±2.85, respectively, during the AP and 203.98±0.18 versus 77.66±0.91, respectively, during the VP. The combination of NIC and Mean CT value during VP had highest sensitivity (90.9%) and specificity (100%) among all phases.ConclusionQuantitative dual-energy CT imaging has promising potential for diagnostic differentiation of sellar meningiomas and pituitary adenomas.

Comparison of gastric vascular anatomy by monochromatic and polychromatic dual-energy spectral computed tomography imaging

To evaluate the use of monochromatic and polychromatic dual-energy spectral computed tomography (CT) imaging for preoperative assessment of gastric vascular anatomy. Patients with suspected gastric cancer underwent spectral CT to generate conventional 140 kVp polychromatic and monochromatic images with energy levels ranging from 40 to 140 keV during the late arterial and portal venous phases. Optimal monochromatic images were selected according to the contrast-to-noise ratio (CNR) for the gastric artery. Image quality was subjectively assessed. Display rates of the arteries were recorded. The study included 64 patients. Monochromatic images at 53 ± 3 keV provided the optimum CNR. At this energy level, subjective image scores were significantly higher for monochromatic images than polychromatic images. There were no significant differences in the display rates of arteries between polychromatic and optimal monochromatic images. Monochromatic images obtained with spectral CT can improve the visualization of gastric arteries.

Recent advances in ytterbium‐based contrast agents for in vivo X‐ray computed tomography imaging: promises and prospects

X-ray computed tomography (CT) imaging is one of the most widely used diagnostic imaging techniques in the clinic, and has raised significant interest in recent years both in research and practice owing to its many advantages such as deep penetration depth, high resolution and facile image processing. Developing heavy metal-based CT contrast agents, especially heavy metal-containing nanoparticulate CT contrast agents, has become a key focus in research fields to address issues of clinical iodinated agents involving short circulation time, low contrast efficiency and potential renal toxicity. In this review, we summarize the development of ytterbium (Yb)-based CT contrast agents and highlight the design and applications of Yb-based nanoparticulate CT contrast agents. Yb has high atomic number and higher abundance in the earth's crust relative to Au, Ta and Bi, which have received much attention as a CT contrast agents. In particular, in contrast to these metal elements, as well as I, Yb has K-edge energy that is located just within the higher-intensity region of X-ray spectra, which can induce significant enhancement in the contrast efficiency. When encapsulated in nanoparticles, Yb can remain in the circulation for a long time. This long in vivo circulation time, combined with the proper K-edge energy and a large absorption cross-section of Yb in the near-infrared region, makes Yb-based nanoparticles particularly promising in angiography, 'multicolor' spectral CT imaging, and multimodal imaging. Finally, we also discuss the prospects and the challenges in the development of Yb-based CT contrast agents.

Spectral CT imaging as a new quantitative tool? Assessment of perfusion defects of pulmonary parenchyma in patients with lung cancer.

This study investigated the capability of dual-energy spectral computed tomography (CT) to quantitatively evaluate lung perfusion defects that are induced by central lung cancer. Thirty-two patients with central lung cancer underwent CT angiography using spectral imaging. A univariate general linear model was conducted to analyze the variance of iodine concentration/CT value with three factors of lung fields. A paired t-test was used to compare iodine concentrations and CT values between the distal end of lung cancer and the corresponding area in the contralateral normal lung. Iodine concentrations increased progressively in the far, intermediate and near ground sides in the normal lung fields at 0.60±0.28, 0.93±0.27 and 1.25±0.38 mg/mL, respectively (P<0.001). The same trend was observed for the CT values [-(840.64±49.08), -(812.66±50.85) and -(760.83±89.17) HU, P<0.001]. The iodine concentration (0.70±0.42 mg/mL) of the lung field in the distal end of lung cancer was significantly lower than the corresponding area in the contralateral normal lung (1.19±0.62 mg/mL) (t=-7.23, P<0.001). However, the CT value of lung field in the distal end of lung cancer was significantly higher than the corresponding area in the contralateral normal lung [-(765.29±93.34) HU vs. -(800.07±76.18) HU, t=3.564, P=0.001]. Spectral CT imaging based on the spectral differentiation of iodine is feasible and can quantitatively evaluate pulmonary perfusion and identify perfusion defects that are induced by central lung cancer. Spectral CT seems to be a promising technique for the simultaneous evaluation of both morphological and functional lung information.

Gold Nanocrystal Labeling Allows Low-Density Lipoprotein Imaging from the Subcellular to Macroscopic Level

Low-density lipoprotein (LDL) plays a critical role in cholesterol transport and is closely linked to the progression of several diseases. This motivates the development of methods to study LDL behavior from the microscopic to whole-body level. We have developed an approach to efficiently load LDL with a range of diagnostically active nanocrystals or hydrophobic agents. We performed focused experiments on LDL labeled with gold nanocrystals (Au-LDL). The labeling procedure had minimal effect on LDL size, morphology, or composition. Biological function was found to be maintained from both in vitro and in vivo experiments. Tumor-bearing mice were injected intravenously with LDL, DiR-LDL, Au-LDL, or a gold-loaded nanoemulsion. LDL accumulation in the tumors was detected with whole-body imaging methods, such as computed tomography (CT), spectral CT, and fluorescence imaging. Cellular localization was studied with transmission electron microscopy and fluorescence techniques. This LDL labeling procedure should permit the study of lipoprotein biointeractions in unprecedented detail.

Quantitative Iodine-Based Material Decomposition Images with Spectral CT Imaging for Differentiating Prostatic Carcinoma from Benign Prostatic Hyperplasia

To investigate the value of iodine-based material decomposition images produced via spectral computed tomography (CT) in differentiating prostate cancer (PCa) from benign prostate hyperplasia (BPH). Fifty-six male patients underwent CT examination with spectral imaging during arterial phase (AP), venous phase (VP), and parenchymal phase (PP) of enhancement. Iodine concentrations of lesions were measured and normalized to that of the obturator internus muscle. Lesion CT values at 75keV (corresponding to the energy of polychromatic images at 120 kVp) were measured and also normalized; their differences between AP and VP, VP and PP, and PP and AP were also obtained. The two-sample t-test was performed for comparisons. A receiver operating characteristic curve was generated to establish the threshold for normalized iodine concentration (NIC). Fifty-two peripheral lesions were found, which were confirmed by biopsy as 28 cases of PCa and 24 BPHs. The NICs of prostate cancers significantly differed from those of the BPHs: 2.38±1.72 compared with 1.21±0.72 in AP, respectively, and 2.67±0.61 compared with 2.27±0.77 in VP. Receiver operating characteristic analysis indicated that an NIC of 1.24 in the AP provided a sensitivity of 88% and a specificity of 71% for differentiating PCa from BPH. Spectral CT imaging enabled quantitative depiction of contrast medium uptake in prostatic lesions and improved sensitivity and specificity for differentiating PCa from BPH.

Differentiating hepatocellular carcinoma from angiomyolipoma of the liver with CT spectral imaging: A preliminary study

To investigate the value of computed tomography (CT) spectral imaging in differentiating hepatocellular carcinoma (HCC) from angiomyolipoma (AML) during the arterial phase (AP) and portal venous phase (PP). Fifty-three patients underwent spectral CT during the AP and PP. Forty-five patients had 45 HCC and eight patients had eight AML. Iodine concentrations in the lesions were normalized to those of the aorta. The normalized iodine concentrations (NIC) and the lesion-normal parenchyma iodine concentration ratio (LNR) were calculated. The two-sample t-test was performed to compare quantitative parameters. Two readers qualitatively assessed lesion types on the basis of imaging features. Sensitivity and specificity were compared between the qualitative and quantitative studies. NICs and LNRs in patients with HCC differed significantly from those in patients with AML: mean NICs were 0.25±0.06mg/ml versus 0.59±0.03mg/ml, respectively, during the AP and 0.52±0.12mg/ml versus 0.78±0.03mg/ml, respectively, during the PP. Mean LNRs were 2.97±0.42 versus 5.85±0.43, respectively, during the AP and 0.99±0.17 versus 1.36±0.05, respectively, during the PP. The NICs and LNRs for HCC were lower than those of AML during the AP and PP. The differences were significant (p<0.05). The threshold NIC and LNR had high sensitivity and specificity in differentiating HCC from AML. CT spectral imaging with the quantitative analysis of iodine concentration may help increase the accuracy of differentiating HCC from AML.

Photon counting spectral breast CT: Effect of adaptive filtration on CT numbers, noise, and contrast to noise ratio

Photon counting spectral (PCS) computed tomography (CT) shows promise for breast imaging. An issue with current photon-counting detectors is low count rate capabilities, artifacts resulting from nonuniform count rate across the field of view, and suboptimal spectral information. These issues are addressed in part by using tissue-equivalent adaptive filtration of the x-ray beam. The purpose of the study was to investigate the effect of adaptive filtration on different aspects of PCS breast CT. The theoretical formulation for the filter shape was derived for different filter materials and evaluated by simulation and an experimental prototype of the filter was fabricated from a tissue-like material (acrylic). The PCS CT images of a glandular breast phantom with adipose and iodine contrast elements were simulated at 40, 60, 90, and 120 kVp tube voltages, with and without adaptive filter. The CT numbers, CT noise, and contrast-to-noise ratio (CNR) were compared for spectral CT images acquired with and without adaptive filters. Similar comparison was made for material-decomposed PCS CT images. The adaptive filter improved the uniformity of CT numbers, CT noise, and CNR in both ordinary and material decomposed PCS CT images. At the same tube output the average CT noise with adaptive filter, although uniform, was higher than the average noise without adaptive filter due to x-ray absorption by the filter. Increasing tube output, so that average skin exposure with the adaptive filter was same as without filter, made the noise with adaptive filter comparable to or lower than that without adaptive filter. Similar effects were observed when energy weighting was applied, and when material decompositions were performed using energy selective CT data. An adaptive filter decreases count rate requirements to the photon counting detectors which enables PCS breast CT based on commercially available detector technologies. Adaptive filter also improves image quality in PCS breast CT by decreasing beam hardening artifacts and by eliminating spatial nonuniformities of CT numbers, noise, and CNR.

Assessment of Hepatic Fatty Infiltration Using Spectral Computed Tomography Imaging

The objective of this study was to investigate the feasibility of using monochromatic spectral computed tomography (CT) imaging to assess fatty infiltration in liver. With spectral CT imaging, phantoms with known fat concentrations were studied for scanning parameter optimization, then 52 patients enrolled into 4 groups (healthy, mild, moderate, and severe fatty infiltration) received abdominal scanning. Based on reconstructed monochromatic images, hepatic attenuation was analyzed, and dual-energy subtraction imaging (DESI) was created for quantifying fat infiltration. Corresponding to various hepatic fat infiltrations, 4 characteristic CT attenuation curve patterns were described. In DESI images, only fat and fatty components appeared bright. For livers without abnormal fat deposition, isolated bright pixels were visualized (% area = 0.5% ± 0.3%). With hepatic fat accumulation increasing, more bright pixels appeared in subtraction images with percentages of total liver area involved in 2.5%, 6.7%, and 13.4% of mild, moderate, and severe fat infiltration cases, respectively (P < 0.05). The corresponding CT values were as follows: 1.33, 2.53, 8.69, and 16.4 Hounsfield units (P < 0.01), which correlated with the % DESI area values (r = 0.9811). Spectral CT imaging is a promising method to quantitatively assess hepatic fat content and fatty infiltration with advantages compared with conventional CT imaging.

Differentiation of neoplastic from bland macroscopic portal vein thrombi using dual-energy spectral CT imaging: a pilot study

To assess the feasibility and value of dual-energy spectral computed tomography (DESCT) imaging for differentiating neoplastic from bland macroscopic portal vein (PV) thrombi. Computed tomography (CT) images of 44 patients with macroscopic PV thrombus (bland group, n = 16; neoplastic group, n = 28) were reviewed. Iodine-based material decomposition images in the portal venous phase were reconstructed to compare the iodine indices between groups, including thrombus iodine density (I (T)), thrombus-aorta iodine density ratio (I (T)/I (A)), and thrombus-PV iodine density ratio (I (T)/I (P)). Differential diagnostic performances of DESCT were calculated in the subgroup of 21 patients with histopathological evidence (bland group, n = 12; neoplastic group, n = 9). The iodine indices of the neoplastic group were significantly higher than those in the bland group (P < 0.001). A threshold I (T) of 1.14mg/mL, I (T)/I (A) of 0.17, and I (T)/I (P) of 0.17 in the portal venous phase yielded 100%, 88.9%, and 100% sensitivity, and 91.7%, 91.7%, and 83.3% specificity, respectively, in differentiating neoplastic from bland PV thrombi. DESCT imaging with quantification of thrombus iodine density in the portal venous phase appears to be a promising new method for distinguishing neoplastic from bland macroscopic PV thrombi. • Differentiating the nature of portal vein thrombus is of great clinical significance. • Iodine-based material decomposition imaging reflects iodine distribution after contrast media administration. • Dual-energy CT with iodine quantification can distinguish bland from neoplastic PV thrombi.

An Early Investigation of Ytterbium Nanocolloids for Selective and Quantitative “Multicolor” Spectral CT Imaging

We report a novel molecular imaging agent based on ytterbium designed for use with spectral "multicolor" computed tomography (CT). Spectral CT or multicolored CT provides all of the benefits of traditional CT, such as rapid tomographic X-ray imaging, but in addition, it simultaneously discriminates metal-rich contrast agents based on the element's unique X-ray K-edge energy signature. Our synthetic approach involved the use of organically soluble Yb(III) complex to produce nanocolloids of Yb of noncrystalline nature incorporating a high density of Yb (>500K/nanoparticle) into a stable metal particle. The resultant particles are constrained to vasculature (∼200 nm) and are highly selective for binding fibrin in the ruptured atherosclerotic plaque. Nanoparticles exhibited excellent signal sensitivity, and the spectral CT technique uniquely discriminates the K-edge signal (60 keV) of Yb from calcium (bones). Bioelimination and preliminary biodistribution reflected the overall safety and defined clearance of these particles in a rodent model.

Pulmonary Embolism Detection and Characterization Through Quantitative Iodine-Based Material Decomposition Images With Spectral Computed Tomography Imaging

To assess the diagnostic value of pulmonary embolism (PE) detection and characterization through quantitative iodine-based material decomposition images with spectral computed tomography (CT) imaging. Fifty-three patients underwent CT pulmonary angiography (CTPA) with spectral imaging mode with the simultaneous acquisition of 80 kVp and 140 kVp on a GE Discovery CT750HD scanner to generate monochromatic CTPA and material decomposition images. CTPA images were reviewed for the presence, localization, and degree (occlusive or nonocclusive) of PE. The iodine distribution in the lung parenchyma on the iodine-based material decomposition images was used to identify perfusion defects, which were then correlated to the CTPA findings. The iodine densities for the perfusion defects and the normal lung parenchyma were measured and statistically compared. Twelve PE patients underwent anticoagulation, and the iodine densities for the perfusion defects before and after the treatment were also measured and compared. The receiver operating characteristics curve was generated to assess the differential diagnostic performances of iodine density in distinguishing the presence or absence of PE and the occlusive or nonocclusive PE. A total of 93 clots (51 occlusive and 42 nonocclusive) were found in 19 patients with lobar (26), segmental (54), or subsegmental (13) distribution. CTPA identified 88 clots initially and 5 more retrospectively with the help of iodine mapping. Thirty-three of 34 normal CTPA patients had symmetric iodine distribution. All occlusive clots and 11 nonocclusive clots showed clear evidence of iodine distribution defects. There was a significant difference for the iodine density among normal lung parenchyma (1.89 mg/mL [0.85-3.29 mg/mL]), nonocclusive perfusion defects (0.83 mg/mL [0.44-1.26 mg/mL]), and occlusive perfusion defects (0.27 mg/mL [0.00-0.62 mg/mL]) (P < 0.001). The iodine densities of perfusion defects before and after anticoagulation were significantly different (P < 0.001). Receiver operating characteristics analyses showed high discriminatory power for using the quantification of iodine density in distinguishing the presence or absence of PE and the occlusive or nonocclusive PE. Spectral CT imaging generated both monochromatic CTPA images for morphologic analysis of PE and material decomposition images for quantitative depiction of pulmonary blood flow and perfusion defects. Quantification of iodine density may be used as a predictor in distinguishing the presence or absence of PE and the severity of PE.

Precision of the measurement of CT numbers: comparison of dual-energy CT spectral imaging with fast kVp switching and conventional CT with phantoms

To compare dual-energy computed tomography (CT) spectral imaging and conventional CT imaging in terms of precision of the measurement of CT numbers in phantoms. A circular phantom (CP) and an elliptical phantom (EP) were used. Capsules filled with iodine contrast media solutions at various concentration levels were placed in the phantoms. Conventional CT was performed at a tube voltage of 120 kVp. Simulated monochromatic images at 65 keV were obtained by dual-energy CT spectral imaging. The CT number of each iodine capsule was measured. A linear regression model was used to evaluate linearity, while analysis of covariance was used to investigate the degree of variability according to phantom shape for each imaging method. With conventional imaging, the slopes of the regression lines for CT numbers measured at the EP center and EP periphery were significantly lower than those measured for CP (P < 0.0001 for both EP center vs. CP and for EP periphery vs. CP). No significant difference in slope was found among phantom shapes in dual-energy spectral CT imaging. Computed tomography numbers varied considerably depending on the phantom shape in conventional CT, whereas dual-energy CT provided consistent CT numbers regardless of the phantom shape.