Iodine Images Research Articles

SU-G-IeP2-09: Iodine Imaging at Spectral CT with a Dual-Layer Detector

Purpose: To evaluate the attenuation response of iodine and the accuracy of iodine quantification on a detector-based spectral CT scanner. Methods: A Gammex 461A phantom was scanned using a dual-layer detector (IQon, Philips) at 120 kVp using helical acquisition with a CDTIvol of 15 mGy to approximate the hospital's clinical body protocol. No modifications to the standard protocol were necessary to enable spectral imaging. Iodine inserts at 6 concentrations (2, 5, 7.5, 10, 15, 20 mg/ml) were scanned individually at the center of the phantom and the 20 mg/ml insert was additionally scanned at the 3, 6, and 12 o'clock positions. Scans were repeated 10 times. Conventional, virtual monoenergetic (40–200 keV) and iodine-no-water images (with pixel values equal to iodine concentration of corresponding tissue) were reconstructed from acquired data. A circular ROI (diameter=30 pixels) was used in each conventional and monoenergetic image to measure the mean and standard deviation of the CT number in HU and in each iodine-no-water image to measure iodine concentration in mg/ml. Results: Mean CT number and contrast-to-noise ratio (CNR) measured from monoenergetic images increased with decreasing keV for all iodine concentrations and matched measurements from conventional images at 75 keV. Measurements from the 20 ml insert showed the CT number is independent of location and CNR is a function only of noise, which was higher in the center. Measured concentration from iodine-no-water images matched phantom manufacturer suggested concentration to within 6% on average for inserts at the center of the phantom. Measured concentrations were systematically higher due to optimization of iodine quantification parameters for clinical mixtures of iodine and blood/tissue. Conclusion: Spectral acquisition and reconstruction with a dual-layer detector represents the physical behavior of iodine as expected and accurately quantifies the material concentration. This should permit a variety of clinical applications including lesion characterization, vessel patency, and myocardial perfusion. This study was performed as part of a research agreement among Philips Healthcare, University Hospitals of Cleveland, and Case Western Reserve University.

SU‐G‐206‐07: Dual‐Energy CT Inter‐ and Intra‐Scanner Variability Within One Make and Model

Purpose:It can be logistically quite difficult to scan patients on the same exact device for their repeat visits in multi‐scanner facilities. The reliability between dual‐energy CT scanners’ quantitative results is not known, nor is their individual repeatability. Therefore, we evaluated inter‐ and intra‐scanner variability with respect to several key clinical quantitative metrics specific to dual‐energy CT.Methods:Eleven identical GE HD‐750 CT scanners in a busy clinical environment were used to perform dual‐energy (DE) CT scans of a large elliptical quality control (QC) phantom (Gammex, Inc.; Middleton, WI) which contains many standard insert materials. The DE‐QC phantom was scanned bi‐weekly during 2016; 3 to 4 scans were obtained from each scanner (a total of 35 data sets were used for analysis). Iodine accuracy for the 2mg/ml, 5mg/ml and 15mg/ml rods (from the Iodine(Water) image set) and soft tissue HU (40 HU based on NIST constants) from the 50keV data set were used to assess inter‐ and intra‐scanner variability (standard deviation).Results:Intra‐scanner variability average for 2mg/ml Iodine was 0.10 mg/ml (range 0.05–0.15 mg/ml), for 5mg/ml Iodine was 0.12 mg/ml (range 0.07–0.16 mg/ml), for 15 mg/ml Iodine was 0.25 mg/ml (range 0.16–0.37 mg/ml), and for the soft tissue inserts was 2.1 HU (range 1.8–2.6 HU). Inter‐scanner variability average for 2mg/ml Iodine was 0.16 mg/ml (range 0.11–0.19 mg/ml), for 5mg/ml Iodine was 0.18 mg/ml (range 0.11–0.22 mg/ml), for 15 mg/ml Iodine was 0.35 mg/ml (range 0.23–0.44 mg/ml), and for the soft tissue inserts was 3.8 HU (range 3.1–4.5 HU).Conclusion:Intra‐scanner variability for the iodine and soft tissue inserts averaged 3.1% and 5.2% respectively, and inter‐scanner variability for these regions analyzed averaged 5.0% and 9.5%, respectively. Future work will include determination of smallest measurable change and acceptable limits for DE‐CT scanner variability over longer time intervals.This research has been supported by funds from Dr. William Murphy, Jr., the John S. Dunn, Sr. Distinguished Chair in Diagnostic Imaging at MD Anderson Cancer Center.

413. Effect of Adenoviral Death Protein on NIS-Based Iodine Therapy and Imaging for Pancreatic Cancer

In this study, we assess our novel Oncolytic Adenovirus (OAd) expressing a dual function therapeutic and imaging transgene, the sodium-iodide symporter (NIS) as a promising alternative for pancreatic cancer treatment. We hypothesized that NIS expression in pancreatic cancer will induce uptake of radioiodine and allow noninvasive SPECT/CT imaging with 123I. We designed our OAd-NIS to overcome the low efficacy of previous vectors. These viruses have a modified Ad5/Ad3 fiber-knob shown to improve the poor transduction of pancreatic cancer cells. Viral replication is controlled under the Cox2 promoter allowing specific delivery of viral genes, and most of adenoviral E3 genes are deleted and replaced with NIS and Adenovirus Death Protein (ADP) genes. We have previously demonstrated significantly improved ability of ADP-overexpressing OAds to enhance viral release and cytolytic activity. Although improved oncolysis enhances viral release and improve the therapeutic effect in solid tumors, it can potentially reduce radioiodide tracer uptake. To test this possibility we designed and compared identical vectors with ADP (OAd-NIS-ADP) and without ADP (OAd-NIS-noADP) in vitro and in vivo. We first compared virus killing ability in pancreatic cancer cell lines. The ADP+ vector was significantly more cytolytic that no-ADP counterpart and showed improved viral replication and spread. Cox2-controlled OAd did not produce cell death in Cox2-negative control, confirming selectivity. We next assessed OAds ability to induce NIS protein expression and radioiodine uptake. NIS-OAds efficiently produce glycosylated NIS multimers as early as 2-days post infection. Infection with no-ADP vectors resulted in a significantly greater radioiodine uptake (125I) compared to ADP+ viruses. Importantly, ex vivo uptake test in human patient tissues confirmed the high level of NIS in pancreatic adenocarcinoma samples, and revealed no 125I uptake in normal pancreas. We further assessed the ability of our vectors to visualize human pancreatic cancer xenografts in a mouse model by monitoring 99mTcO4− accumulation with SPECT-CT. The OAd-NIS-noADP showed an earlier and more sustained radioisotope uptake when compared to ADP+ supporting its use as a more sensitive diagnostic tool for pancreatic cancer. Of contrary, the ADP+ vector significantly outperformed OAd-NIS-noADP in tumor shrinkage. These results suggest that while OAd-NIS-noADP produces a greater radiotracer uptake and can be used as a diagnostic tool, its ADP+ counterpart results in a better therapeutic effect when applied as a monotherapy. It is now essential to estimate the therapeutic ability of both vectors upon combination with I-131 (ongoing study). Further investigation will include the imaging and therapeutic studies in patient-derived xenografts. Ultimately, the goal of our research is to design a multimodal therapy with radiation and oncolytic virus for diagnosis and therapy of cancers.

Calibration Free Beam Hardening Correction for Cardiac CT Perfusion Imaging.

Myocardial perfusion imaging using CT (MPI-CT) and coronary CTA have the potential to make CT an ideal noninvasive gate-keeper for invasive coronary angiography. However, beam hardening artifacts (BHA) prevent accurate blood flow calculation in MPI-CT. BH Correction (BHC) methods require either energy-sensitive CT, not widely available, or typically a calibration-based method. We developed a calibration-free, automatic BHC (ABHC) method suitable for MPI-CT. The algorithm works with any BHC method and iteratively determines model parameters using proposed BHA-specific cost function. In this work, we use the polynomial BHC extended to three materials. The image is segmented into soft tissue, bone, and iodine images, based on mean HU and temporal enhancement. Forward projections of bone and iodine images are obtained, and in each iteration polynomial correction is applied. Corrections are then back projected and combined to obtain the current iteration's BHC image. This process is iterated until cost is minimized. We evaluate the algorithm on simulated and physical phantom images and on preclinical MPI-CT data. The scans were obtained on a prototype spectral detector CT (SDCT) scanner (Philips Healthcare). Mono-energetic reconstructed images were used as the reference. In the simulated phantom, BH streak artifacts were reduced from 12±2HU to 1±1HU and cupping was reduced by 81%. Similarly, in physical phantom, BH streak artifacts were reduced from 48±6HU to 1±5HU and cupping was reduced by 86%. In preclinical MPI-CT images, BHA was reduced from 28±6 HU to less than 4±4HU at peak enhancement. Results suggest that the algorithm can be used to reduce BHA in conventional CT and improve MPI-CT accuracy.

A method for material decomposition in dual-energy contrast enhancement digital mammography

Background and purpose: Dual-energy mammography is a technique which is being used for accuracy enhancement of the breast cancer diagnosis especially in dense breasts. It is also a valuable and practical way for obtaining detailed information about tumor’s size, disease progression and micro-calcification detection which is the earlier sign of breast cancer. The aim of this study was to investigate the possibility of separating different thicknesses of micro-calcifications, Iodine, and Bismuth contrast agents, simultaneously.Material and methods: A breast phantom was made from acrylic and olive oil containing various density thicknesses of Iodine and Bismuth contrast agents. To simulate micro-calcifications, different thicknesses of the Aluminum sheets were used and placed in the phantom as well. In this work, an X-ray tube with Tungsten anode and a flat panel semiconductor detector were used for imaging processes. To customize the X-ray spectrum, a combination of copper and aluminum were used as filters to optimize the X-ray high energy spectrum in dual energy imaging.Results: According to the results, separating of Iodine images was prepared by using of Iodine’s k-edge property for thicknesses greater than 0.5mg/cm2. Also, Bismuth and Aluminum images with thicknesses greater than 0.53mg/cm2 and 200μm, respectively, were isolated automatically by material thicknesses estimation method in dual-energy imaging technique.Conclusion: The results demonstrated that Iodine and Bismuth contrast agents together with micro-calcifications can be separated from breast tissue with good accuracy by using proposed dual-energy contrast enhanced mammography technique.

Reduction of peristalsis-related gastrointestinal streak artifacts with dual-energy CT: a patient and phantom study.

The purpose of the study was to assess the ability of rapid-kV switching (rs) dual-energy computed tomography (DECT) to reduce peristalsis-related streak artifact. rsDECT images of 100 consecutive patients (48 male, 52 female, mean age 57years) were retrospectively evaluated in this institutional review board-approved study. Image reconstructions included virtual monochromatic 70 and 120keV images, as well as iodine(-water) and water(-iodine) material decomposition images. We recorded the presence and severity of artifacts qualitatively (4-point scale) and quantitatively [iodine/water concentrations, Hounsfield units, gray scale values (GY)] and compared to corresponding unaffected reference tissue. Similar measures were obtained in DECT images of a peristalsis phantom. Wilcoxon signed-rank and paired t tests were used to compare results between different image reconstructions. Peristalsis-related streak artifacts were found in 49 (49%) of the DECT examinations. Artifacts were significantly more severe in 70, 120, and water(-iodine) images than in iodine(-water) images (qualitative readout P<0.001, each). Quantitative measurements were significantly different between the artifact and the reference tissue in 70, 120keV, and water(-iodine) images (P<0.001 for both HU and GY for each image reconstruction), but not significantly different in iodine(-water) images (iodine concentrations P=0.088 and GY P=0.111). Similar results were seen in the peristalsis DECT phantom study. Peristalsis-related streak artifacts seen in 70, 120keV, and water(-iodine) images are substantially reduced in iodine(-water) images at rsDECT.

Dual-energy CT of pancreatic adenocarcinoma: reproducibility of primary tumor measurements and assessment of tumor conspicuity and margin sharpness.

To determine the inter- and intra-reader agreement of size, conspicuity, and margin sharpness of pancreatic adenocarcinoma on monochromatic, polychromatic, and iodine map dual-energy CT (DECT) images. Retrospective review of DECT images from 61 patients with untreated pancreatic adenocarcinoma was performed by three radiologists independently. Pancreatic parenchymal phase images were generated as 50and 70keV, 140 kVp quality control (QC), and iodine map images. These were analyzed in a blinded randomized order during four reading sessions separated by 5-7days. For each image set, readers recorded the longest axial and perpendicular primary tumor dimensions, and qualitatively scored tumor conspicuity and edge sharpness on 5-point scales. Linear mixed model was used to estimate and compare tumor measurements, tumor conspicuity, and tumor edge sharpness scores between readers and image sets. Kappa statistics were used to determine inter-observer agreement for tumor conspicuity and edge sharpness. The range of tumor measures (mean of longest dimension±standard deviation) was 3.18±1.41 to 3.83±1.57cm. Reproducibility of tumor measurements was very high with mild variability (s (2)=0.01-0.10) between readers for the different image sets. Inter-observer agreement values for tumor conspicuity (κ=0.01-0.17) and edge sharpness (κ=0.12-0.25) were low for all image sets, although two of three readers scored tumor conspicuity and edge sharpness higher on monochromatic and iodine map DECT images than on 140 kVp QC images (p<0.05). Pancreatic adenocarcinoma measurements were highly reproducible on DECT images, and subjective reader preference trended toward monochromatic and iodine images rather than polychromatic images.

Use of Dual-Energy CT and Iodine Maps in Evaluation of Bowel Disease.

Dual-energy computed tomography (CT) relies on material-dependent x-ray absorption behavior from concurrently acquired high- and low-kilovolt peak data and has a range of imaging applications. This article focuses on use of dual-energy CT in assessment of bowel disease. After a summary of relevant dual-energy CT image acquisition and postprocessing principles, the authors describe dual-energy techniques of greatest utility in evaluation of benign and malignant pathologic conditions in the bowel, including neoplastic, vascular, infectious, and inflammatory disorders, as well as in assessment of abdominopelvic trauma. The dual-energy postprocessing techniques of iodine-selective imaging and virtual monochromatic imaging have the broadest applicability in bowel imaging. They may be used for improved visualization of subtle differences in bowel wall enhancement or for quantitative assessment of altered enhancement for evaluation of a neoplasm or bowel ischemia. Iodine images and virtual monochromatic low-kiloelectron volt images are particularly helpful for assessment of a neoplasm, ischemia, infection, or inflammation, while iodine maps paired with virtual nonenhanced images are most helpful to differentiate iodine from other dense materials, as in gastrointestinal bleeding or trauma. In most applications, radiation doses at dual-energy CT are comparable to those at traditional CT. However, dual-energy CT may allow reduction in radiation dose by using virtual nonenhanced images that obviate an additional nonenhanced CT acquisition. Limitations of dual-energy CT are discussed, including potential challenges in acquisition, postprocessing, and interpretation.

Spectral Imaging for Intracranial Stents and Stent Lumen

IntroductionApplication of computed tomography for monitoring intracranial stents is limited because of stent-related artifacts. Our purpose was to evaluate the effect of gemstone spectral imaging on the intracranial stent and stent lumen.Materials and MethodsIn vitro, we scanned Enterprise stent phantom and a stent–cheese complex using the gemstone spectral imaging protocol. Follow-up gemstone spectral images of 15 consecutive patients with placement of Enterprise from January 2013 to September 2014 were also retrospectively reviewed. We used 70-keV, 140-keV, iodine (water), iodine (calcium), and iodine (hydroxyapatite) images to evaluate their effect on the intracranial stent and stent lumen. Two regions of interest were individually placed in stent lumen and adjacent brain tissue. Contrast-to-noise ratio was measured to determine image quality. The maximal diameter of stent markers was also measured to evaluate stent-related artifact. Two radiologists independently graded the visibility of the lumen at the maker location by using a 4-point scale. The mean of grading score, contrast/noise ratio and maximal diameter of stent markers were compared among all modes. All results were analyzed by SPSS version 20.ResultsIn vitro, iodine (water) images decreased metallic artifact of stent makers to the greatest degree. The most areas of cheese were observed on iodine (water) images. In vivo, iodine (water) images had the smallest average diameter of stent markers (0.33 ± 0.17mm; P < .05) and showed the highest mean grading score (2.94 ± 0.94; P < .05) and contrast/noise ratio of in-stent lumen (160.03 ±37.79; P < .05) among all the modes.ConclusionIodine (water) images can help reduce stent-related artifacts of Enterprise and enhance contrast of in-stent lumen. Spectral imaging may be considered a noninvasive modality for following-up patients with in-stent stenosis.

Dual-Energy CT: Spectrum of Thoracic Abnormalities.

Recent studies have demonstrated that dual-energy computed tomography (CT) can provide useful information in several chest-related clinical indications. Compared with single-energy CT, dual-energy CT of the chest is feasible with the use of a radiation-dose-neutral scanning protocol. This article highlights the different types of images that can be generated by using dual-energy CT protocols such as virtual monochromatic, virtual unenhanced (ie, water), and pulmonary blood volume (ie, iodine) images. The physical basis of dual-energy CT and material decomposition are explained. The advantages of the use of virtual low-monochromatic images include reduced volume of intravenous contrast material and improved contrast resolution of images. The use of virtual high-monochromatic images can reduce beam hardening and contrast streak artifacts. The pulmonary blood volume images can help differentiate various parenchymal abnormalities, such as infarcts, atelectasis, and pneumonias, as well as airway abnormalities. The pulmonary blood volume images allow quantitative and qualitative assessment of iodine distribution. The estimation of iodine concentration (quantitative assessment) provides objective analysis of enhancement. The advantages of virtual unenhanced images include differentiation of calcifications, talc, and enhanced thoracic structures. Dual-energy CT has applications in oncologic imaging, including diagnosis of thoracic masses, treatment planning, and assessment of response to treatment. Understanding the concept of dual-energy CT and its clinical application in the chest are the goals of this article.

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.

Burst predicting neurons survive an in vitro glutamate injury model of cerebral ischemia.

Neuronal activity in vitro exhibits network bursts characterized by brief periods of increased spike rates. Recent work shows that a subpopulation of neurons reliably predicts the occurrence of network bursts. Here, we examined the role of burst predictors in cultures undergoing an in vitro model of cerebral ischemia. Dissociated primary cortical neurons were plated on multielectrode arrays and spontaneous activity was recorded at 17 days in vitro (DIV). This activity was characterized by neuronal avalanches where burst statistics followed a power law. We identified burst predictors as channels that consistently fired immediately prior to network bursts. The timing of these predictors relative to bursts followed a skewed distribution that differed sharply from a null model based on branching ratio. A portion of cultures were subjected to an excitotoxic insult (DIV 18). Propidium iodine and fluorescence imaging confirmed cell death in these cultures. While the insult did not alter the distribution of avalanches, it resulted in alterations in overall spike rates. Burst predictors, however, maintained baseline levels of activity. The resilience of burst predictors following excitotoxic insult suggests a key role of these units in maintaining network activity following injury, with implications for the selective effects of ischemia in the brain.

Lowering iodinated contrast concentration in infrainguinal endovascular interventions: a three-armed randomized controlled non-inferiority trial.

ObjectivesTo determine the influence of lowering iodinated contrast concentration on confidence of interventional radiologists in diagnosing and treating lesions during endovascular interventions in patients with symptomatic peripheral arterial disease (PAD).MethodsA randomized controlled non-inferiority trial was performed in 60 patients. Intervention was performed with contrast concentrations (in mg of iodine per mL, mgI/mL) of 300 (standard), 240, or 140 mgI/mL. Primary outcome was confidence (score 0-100 %) of radiologists in diagnosing and treating arterial lesions. Secondary outcomes were procedural iodine load and image quality (i.e. non-diagnostic, limited, diagnostic, exemplary).ResultsMedian confidence scores in diagnosing lesions were 100 % (range 81-100 %) for the 300 group (n = 21), 100 % (range 82-100 %) for the 240 group (n = 19), and 100 % (range 91-100 %) for the 140 group (n = 20) (both p = 1.00 compared to the 300 group). Median scores for treating lesions in the 240 and 140 groups, 100 % (range 79-100 %, p = 0.40), and 100 % (range 63-100 %, p = 0.25), respectively, were not lower compared to the 300 group (median 100 %, range 78-100 %). Procedural iodine load was lower in the 240 (24.3 ± 7.6 g, p = 0.022) and 140 groups (17.8 ± 5.6 g, p < 0.001) compared to the 300 group (29.7 ± 6.3 g). Image quality was diagnostic for all groups.ConclusionUsing iodine contrast of 140 mgI/mL for diagnosis and interventions in PAD patients significantly reduces administered iodine load without compromising image quality. Future use of lower iodine dose is recommended.Key Points• Lower iodinated contrast concentration during endovascular intervention does not decrease radiologist’s confidence.• Image quality of standardized angiographies remains diagnostic using 140 mgI/mL iodinated contrast concentration.• Iodine load during intervention can be decreased by >40 % when using 140 mgI/mL.• Implementing the use of a lower iodinated contrast concentration will reduce the costs of the procedure.

Feasibility of virtual nonenhanced images derived from single-source fast kVp-switching dual-energy CT in evaluating gastric tumors

PurposeTo assess the feasibility of virtual nonenhanced (VNE) images derived from single-source fast kVp-switching dual-energy CT, namely material suppressed iodine (MSI) images in evaluating gastric tumors, and to calculate potential radiation dose reductions for a dual-phase gemstone spectral imaging (GSI) abdominal CT compared with a standard triple-phase protocol. Materials and methodsThe institutional review board approved this prospective study; all patients provided written informed consent. 95 patients underwent preoperative enhanced CT that included true nonenhanced (TNE) with conventional 120kVp mode, arterial phase (AP) and venous phase (VP) with GSI mode. MSI images were obtained from enhanced images of AP. Two abdominal radiologists independently evaluated the image quality of TNE and MSI images using a 5-point scale. Interobserver agreement was accessed by kappa value. The sensitivity for lesions on TNE and MSI images were evaluated. The CT number of various regions and image noise was measured on TNE and MSI images. The relative enhancement CT value of lesions, contrast to noise(CNR) of gastric tumors and effective radiation doses for triple-phase and dual-phase protocol were calculated. Differences were tested for statistical significance using Wilcoxon signed rank test and paired t-test. ResultsInterobserver agreement about image quality was excellent(all kappa>0.750). No significant difference in image quality was found between TNE 4.32±0.53 and MSI 4.21±0.51 images (P>0.05). In respect to the sensitivities for gastric tumors, lymph node and liver metastasis, there were no significant differences between TNE and MSI images (all P>0.05). The CT number on TNE and MSI images, respectively, for gastric tumor were 32.79HU±6.45 and 35.02HU±5.01 (P=0.006); lymph nodes, 31.33HU±6.37 and 31.61HU±5.73 (P=0.334); liver metastasis, 37.79HU±8.40 and 39.76HU±8.50 (P=0.041); liver, 56.56HU±7.87 and 58.32HU±8.73 (P=0.057); psoas muscle, 52.30HU±5.63 and 51.80HU±6.86 (P=0.533); aorta, 38.16HU±4.91 and 42.49HU±4.49 (P<0.001). The CT relative enhancement value of gastric tumors, lymph node and liver metastasis had no significant difference between TNE and MSI images (P=0.083, 0.194, 0.156). MSI images had higher image noise than TNE images (P<0.001). The CNR of gastric tumor on MSI images was higher than that on TNE images (P<0.001). The effective dose for triple-phase was 25.1mSv±6.2 and that for dual-phase was 17.7mSv±4.1. The dose saving by removing the TNE was 7.5mSv (30.5%). ConclusionIn patients with gastric tumors, the MSI images derived from single-source fast kVp-switching dual-energy CT can provide comparable image quality to TNE images and reliable diagnostic information; replacing TNE images will lower radiation dose by 30.5%.

Optimization of beam quality for photon-counting spectral computed tomography in head imaging: simulation study.

Head computed tomography (CT) plays an important role in the comprehensive evaluation of acute stroke. Photon-counting spectral detectors, as promising candidates for use in the next generation of x-ray CT systems, allow for assigning more weight to low-energy x-rays that generally contain more contrast information. Most importantly, the spectral information can be utilized to decompose the original set of energy-selective images into several basis function images that are inherently free of beam-hardening artifacts, a potential advantage for further improving the diagnosis accuracy. We are developing a photon-counting spectral detector for CT applications. The purpose of this work is to determine the optimal beam quality for material decomposition in two head imaging cases: nonenhanced imaging and K-edge imaging. A cylindrical brain tissue of 16-cm diameter, coated by a 6-mm-thick bone layer and 2-mm-thick skin layer, was used as a head phantom. The imaging target was a 5-mm-thick blood vessel centered in the head phantom. In K-edge imaging, two contrast agents, iodine and gadolinium, with the same concentration ([Formula: see text]) were studied. Three parameters that affect beam quality were evaluated: kVp settings (50 to 130kVp), filter materials ([Formula: see text] to 83), and filter thicknesses [0 to 2 half-value layer (HVL)]. The image qualities resulting from the varying x-ray beams were compared in terms of two figures of merit (FOMs): squared signal-difference-to-noise ratio normalized by brain dose ([Formula: see text]) and that normalized by skin dose ([Formula: see text]). For nonenhanced imaging, the results show that the use of the 120-kVp spectrum filtered by 2 HVL copper ([Formula: see text]) provides the best performance in both FOMs. When iodine is used in K-edge imaging, the optimal filter is 2 HVL iodine ([Formula: see text]) and the optimal kVps are 60kVp in terms of [Formula: see text] and 75kVp in terms of [Formula: see text]. A tradeoff of 65kVp was proposed to lower the potential risk of skin injuries if a relatively long exposure time is necessarily performed in the iodinated imaging. In the case of gadolinium imaging, both SD and BD can be minimized at 120kVp filtered with 2 HVL thulium ([Formula: see text]). The results also indicate that with the same concentration and their respective optimal spectrum, the values of [Formula: see text] and [Formula: see text] in gadolinium imaging are, respectively, around 3 and 10 times larger than those in iodine imaging. However, since gadolinium is used in much lower concentrations than iodine in the clinic, iodine may be a preferable candidate for K-edge imaging.

Feasibility study on application of gemstone spectral CT material suppressed iodine as virtual non-contrast CT scan in head and neck neoplasms

Objective To evaluate the feasibility of applying spectral CT material suppressed iodine (MSI) imaging as virtual plain CT scan to replace traditional non-contrast (TNC) CT in head and neck neoplasms. Methods A total of 52 patients with initial diagnosis of head and neck neoplasms underwent TNC CT scanning and spectrum mode enhanced scanning in the head and neck with spectral CT. With GSI Volume Viewer software from GE AW4.6 workstation, the enhanced scanning data were processed and MSI images were acquired. The CT values of different tissues (fat, erector spinae, cervical vertebrae, thyroid, and brain parenchyma) and the enhancement rate in erector spinae, carotid sinus were compared between MSI and TNC images. Image quality was objectively evaluated in noise and SNR for MSI and TNC images, while the subjective evaluation included the visibility of lesions, subjective acceptance rate, diagnostic efficacy (with/without lesions or lesion calcification, necrosis). Radiation dose including volume CT dose index (CTDIvol) and effective dose (ED) was compared between MSI and TNC. Results (1) CT values of erector spinae on MSI and TNC imaging were (52±6) and (52±7) HU respectively, and the difference between the two image modes was not significant (t=0.39, P>0.05). CT values on MSI and TNC Imaging were [-74 (-86, -59) HU] and [-79 (-73, -61) HU] for fat (Z=-2.71, P 0.05). The difference of carotid sinus enhancement rate was significant 5.75(4.70, 6.73) and 4.37(3.91, 5.61) respectively,Z=-5.50,P 0.05 ).Unacceptable and acceptable cases in imaging quality of MSI were 3 and 49 respectively, while those were 2 and 50 in TNC group. Subjective acceptance rate between MST and TNC images was not significantly different (χ2=0.01, P>0.05). (5) Diagnostic performance evaluation showed that the consistency of two observers was good in detecting lesions, necrosis and calcification between MSI and TNC image, with K value 0.93, 0.83 and 0.90 respectively (P<0.05). (6) Radiation doses between pure energy spectrum enhanced mode and conventional pre plus post contrast enhanced mode were compared. And differences of CTDIvol [11.78(10.98, 17.30) mGy] and [23.89 (22.42, 29.98) mGy] respectively],ED [1.89(1.63, 2.29) mSv] and [3.77(3.21, 4.16 ) mSv] respectively] were significant (Z=-6.28, P<0.05). Pure energy spectrum enhanced mode reduced 39.07% of CTDIvol and 45.75% of ED respectively. Conclusions MSI imaging can be a potential substitute for TNC imaging. And it has clinical values in the diagnosis of head and neck neoplasms. Key words: Tomography, X-ray computed; Head and neck neoplasms

Quasi‐monochromatic X‐ray photon counting using a silicon‐PIN detector and an energy‐selecting device and its application to iodine imaging

Quasi‐monochromatic X‐ray photon counting using a silicon‐PIN detector and an energy‐selecting device and its application to iodine imaging

Dual-energy CT after radiofrequency ablation of liver, kidney, and lung lesions: a review of features.

Early detection of residual tumour and local tumour progression (LTP) after radiofrequency (RF) ablation is crucial in the decision whether or not to re-ablate. In general, standard contrast-enhanced computed tomography (CT) is used to evaluate the technique effectiveness; however, it is difficult to differentiate post-treatment changes from residual tumour. Dual-energy CT (DECT) is a relatively new technique that enables more specific tissue characterisation of iodine-enhanced structures because of the isolation of iodine in the imaging data. Necrotic post-ablation zones can be depicted as avascular regions by DECT on greyscale- and colour-coded iodine images. Synthesised monochromatic images from dual-energy CT with spectral analysis can be used to select the optimal keV to achieve the highest contrast-to-noise ratio between tissues. This facilitates outlining the interface between the ablation zone and surrounding tissue. Post-processing of DECT data can lead to an improved characterisation and delineation of benign post-ablation changes from LTP. Radiologists need to be familiar with typical post-ablation image interpretations when using DECT techniques. Here, we review the spectrum of changes after RF ablation of liver, kidney, and lung lesions using single-source DECT imaging, with the emphasis on the additional information obtained and pitfalls encountered with this relatively new technique. Teaching Points •Technical success of RF ablation means complete destruction of the tumour. •Assessment of residual tumour on contrast-enhanced CT is hindered by post-ablative changes. •DECT improves material differentiation and may improve focal lesion characterisation. •Iodine maps delineate the treated area from the surrounding parenchyma well.

The value of using iodine maps in distinguishing the benign and malignant thyroid nodule with dual-source CT by dual energy

Objective To investigate the clinical application of iodine-enhanced image of dual-source computed tomography(DSCT)in distinguishing benign and malignant thyroid nodules. Methods Thirty patients with thyroid nodules underwent DSCT imaging with dual-source computed tomography. All thyroid nodules were confirmed by operation or biopsy. Iodine concentration in the thyroid nodule and normal thyroid tissue were calculated and not enhanced. A receiver operator characteristic curve in SPSS software was utilized to select critical value of optimum sensitivity and specificity. The data were retrospectively analyzed. Results There were 30 patients with 40 thyroid nodules(17 malignant nodules, 23 benign nodules). The range of iodine concentration in malignant nodules was -2.4-0.9 mg/ml(median -0.5 mg/ml), and that in normal thyroid tissue was -0.9-2.2 mg/ml(median 0.7 mg/ml). The range of iodine concentration in benign nodules was 1.5-4.4 mg/ml(median 2.4 mg/ml), and that in normal thyroid tissue was 1.5-4.3 mg/ml(median 2.6 mg/ml). Among them, the iodine concentration in the solid part of benign nodules was significantly higher than that in malignant nodules, the difference was statistically significant(Z=-3.23, P=0.21). When critical value was 0.15 mg/ml, sensitivity was 82.40%, specificity was 81.00%. Conclusion Iodine-enhanced images with DSCT in non-enhanced weighted images may be an implement tool for differential diagnosis of benign and malignant nodules of the thyroid gland. (Chin J Endocrinol Metab, 2015, 31: 333-336) Key words: Thyroid nodule; Tomography, X-ray computed; Iodine image

Non-invasive deep tissue imaging of iodine modified poly(caprolactone-co-1-4-oxepan-1,5-dione) using X-ray

When biodegradable polyester devices, like sutures and screws, are implanted into the body, it is very challenging to image them in deep tissue, monitor their degradation, and detect defects. We report our recent findings on non-invasive deep tissue imaging of polyester degradation, stability and integrity using an iodinated-polycaprolactone (i-P(CLcoOPD)) X-ray imaging contrast agent. The results of experiments performed with i-P(CLcoOPD) demonstrate the feasibility to quantify in-situ polyester degradation in vitro and in vivo using rats. We also demonstrate that X-ray imaging could be used to identify and quantify physical defects, such as cracks, in polymeric implants using rabbit animal models. This approach enables non-invasive monitoring of polyester materials and is expected to become an important technology for improving the imaging of polymers at clinically relevant depths.