CT Contrast Agent Research Articles

Non-Rigid Registration of Liver CT Images for CT-Guided Ablation of Liver Tumors.

CT-guided percutaneous ablation for liver cancer treatment is a relevant technique for patients not eligible for surgery and with tumors that are inconspicuous on US imaging. The lack of real-time imaging and the use of a limited amount of CT contrast agent make targeting the tumor with the needle challenging. In this study, we evaluate a registration framework that allows the integration of diagnostic pre-operative contrast enhanced CT images and intra-operative non-contrast enhanced CT images to improve image guidance in the intervention. The liver and tumor are segmented in the pre-operative contrast enhanced CT images. Next, the contrast enhanced image is registered to the intra-operative CT images in a two-stage approach. First, the contrast-enhanced diagnostic image is non-rigidly registered to a non-contrast enhanced image that is conventionally acquired at the start of the intervention. In case the initial registration is not sufficiently accurate, a refinement step is applied using non-rigid registration method with a local rigidity term. In the second stage, the intra-operative CT-images that are used to check the needle position, which often consist of only a few slices, are registered rigidly to the intra-operative image that was acquired at the start of the intervention. Subsequently, the diagnostic image is registered to the current intra-operative image, using both transformations, this allows the visualization of the tumor region extracted from pre-operative data in the intra-operative CT images containing needle. The method is evaluated on imaging data of 19 patients at the Erasmus MC. Quantitative evaluation is performed using the Dice metric, mean surface distance of the liver border and corresponding landmarks in the diagnostic and the intra-operative images. The registration of the diagnostic CT image to the initial intra-operative CT image did not require a refinement step in 13 cases. For those cases, the resulting registration had a Dice coefficient for the livers of 91.4%, a mean surface distance of 4.4 mm and a mean distance between corresponding landmarks of 4.7 mm. For the three cases with a refinement step, the registration result significantly improved (p<0.05) compared to the result of the initial non rigid registration method (DICE of 90.3% vs 71.3% and mean surface distance of 5.1 mm vs 11.3 mm and mean distance between corresponding landmark of 6.4 mm vs 10.2 mm). The registration of the preoperative data with the needle image in 16 cases yielded a DICE of 90.1% and a mean surface distance of 5.2 mm. The remaining three cases with DICE smaller than 80% were classified as unsuccessful registration. The results show that this is promising tool for liver image registration in interventional radiology.

Assessment of low energy X-ray imaging for magnetic and gold nanoparticles

Introduction Gold and magnetic nanoparticles (NPs) are already used as contrast agents in CT and MRI diagnosis respectively, as well as in hyperthermia treatments. In both cases it is very important to be able to determine in vivo the distribution of the NPs. This can be done by radiolabeling the NPs or via MRI. These methods however present serious drawbacks in terms of cost and complexity. Purpose The purpose of this study is to explore and standardize a procedure of in vivo X-ray imaging for magnetic and gold NPs for diagnostic and pre-therapeutic purposes, using this low-cost, simple, readily available technology. Materials and methods The measurements were carried out on a prototype bench top x-ray system, consisting of an X-ray tube of a maximum beam energy of 80 keV and a minimum focal spot of 33 μm and of a CMOS detector with an active area of 12 × 12 cm and a spatial resolution of 0.1 mm. NPs samples of concentrations ranging between 1 and 500 mg of substance/ml were studied and compared with standard iodine solutions. Results All substances are found to present significant contrast enhancement properties and are used to create a standardized imaging procedure with respect to their concentrations. Gold nanoparticles are easily seen in lower concentrations and dual energy subtraction offers a greater differentiation in the observed attenuation properties. Localization and distribution information can be obtained in vivo through X-ray imaging. Conclusion A standardized procedure of in vivo X-ray imaging is set up for magnetic and gold NPs for diagnostic and pre-therapeutic purposes. Disclosure There is no relationship to be disclosed that may bias this presentation.

18F-FDG PET/CT 검사에서 정량분석에 관한 CT와 MRI 조영제의 효과

PET/CT 촬영에서 정량분석에 영향을 주는 다양한 인자 중 현재 상품화된 CT 조영제와 MRI 조영제의 종류별 각 성분의 특성에 따른 SUV의 변화를 비교·분석하고자 하였다. 실험장비는 Discovery 690 PET/CT(Ge)와 NEMA NU2- 1994 PET phantom를 이용하였고, 팬텀에 증류수 2/3를 채워 넣은 후 방사성동위원소(18F-FDG 37 MBq)와 각각의 CT와 MRI 조영제를 순차적으로 주입하여 팬텀을 고르게 교반하고 다시 증류수를 가득 채운 후 기포가 생기지 않게 하였다. 방출스캔은 FDG 또는 FDG와 혼합한 조영제를 넣고 40분에 15분 동안 스캔하였으며, 투과스캔은 CT로 관전압 120 kVp, 관전류 40 mA, 회전시간 0.5 sec, 단면두께 3.27 mm, DFOV 30 cm의 조건으로 스캔하였다. 분석방법으로 정량분석은 각각 10, 15, 20, 25, 30번째 slice에서 region of interest (ROI)를 설정하여 각각 SUVmean, SUVmax를 구하였다. 결과적으로 순수 FDG 영상과 비교에서 MRI 조영제를 혼합한 3종류의 영상 모두에서 SUVmean 가 높게 측정되었으나 통계적 유의성은 없었고, SUVmax 에서는 유의한 결과를 얻었다. 또한 4종류의 CT 조영제 영상은 SUVmean, SUVmax 모두 유의한 결과를 얻었다. PET/CT는 영상의 정확도를 위해 감쇠 보정은 다양한 방법으로 시행되고 있지만 CT와 MRI 조영제는 감쇠보정 시 영상의 왜곡에 의한 진단적 가치를 저하시킬 수 있다. 이러한 이유로 진료 당일 여러 종류의 검사를 시행하기 전 반드시 선행되어야 할 검사를 선별하여 서로 영향을 주지 않도록 함으로서 고객에게 차별화된 양질의 의료서비스를 제공해야 한다.

External application of ethanol combined with polygonum cuspidatum cream for prevention of phlebitis caused by enhanced CT contrast agent leakage

Objective To investigate the effects of external application of ethanol combined with polygonum cuspidatum cream for the prevention of phlebitis caused by enhanced CT contrast agent leakage and summarize nursing experience. Methods A total of 82 patients with enhanced CT contrast agent leakage from October 2013 to March 2015 were selected and randomly divided into observation group (n=41) and control group (n=41). The patients in observation group were treated by ethanol combined with polygonum cuspidatum cream for external application, while the patients in control group were treated by ethanol combined with magnesium sulphate. Phlebitis occurrence were compared between two groups. Results The severity of phlebitis in observation group was lower than those of control group (P<0.05). In observation group, the time of swelling reduction and pain disappearance were significantly shorter than those of control group (P<0.05). Conclusions External application of ethanol combined with polygonum cuspidatum cream can prevent the phlebitis caused by enhanced CT contrast agent leakage effectively and relieve local swelling and pain with excellent security. Key words: Phlebitis; Polygonum cuspidatum cream; Ethanol; External application; CT

SU‐F‐T‐662: Feasibility Study of Fe3O4/TaOx Nano Particles as a Radiosensitizer for Radiation Therapy

Purpose:To investigate the feasibility of using multifunctional Fe3O4/TaOx(core / shell) nano particles developed for CT and MRI contrast agent as dose enhancing radiosensitizers.Methods:Firstly, to verify the imaging detectability of Fe3O4/TaOx nano particles, in‐vivo tests were conducted. Approximately 600 mg/kg of 19 nm diameter Fe3O4/TaOx nano particles dispersed in phosphate buffered saline(PBS) were injected to ten nude Balb/c mice through the tail vein. Difference between pre‐ and post‐injection images was analyzed by computing the pixel histogram and correlation coefficient factor using MATLAB in the user defined ROI. Secondly, to quantify the potential therapeutic enhancement with nano materials, DER (Dose Enhancement Ratio) and number of SER (Secondary Electron Ratio) were computed using TOPAS(ver.2.0 P‐03) MC simulation.Results:In CT, MRI imaging, the aorta, the blood vessel, and the liver were clearly visualized after intravenous injection of Fe3O4/TaOx nano particles. There was large different between pre and post‐injection images of Histogram data and Coefficients of correlation factor in CT and MR are 0.006, 0.060, respectively. When 70 MeV protons were irradiated for a Gold, Tantalum, TaOx, Fe3O4/TaOx, Fe3O4 nano particle, DER was 2.59, 2.41, 1.68, 1.54 and 1.36 respectively. Similarly, SER increment was 2.31, 2.15, 1.56, 1.46, and 1.27 for Gold, Tantalum, TaOx, Fe3O4/TaOx, Fe3O4 nano particle, respectively.Conclusion:Fe3O4/TaOx nano particles have potential as a multifunctional agent which enhances the accuracy in cancer detection through visualization of developed tumor lesion and increases the therapeutic effect in proton therapy. The dose enhancement with Fe3O4/TaOx was estimated as half of the Gold. However, tumor targeting such as combined with magnetic field may overcome the low DER.This research was supported by the NRF funded by the Ministry of Science, ICT &amp; Future Planning (2012M3A9B6055201 and 2012R1A1A2042414), Samsung Medical Center grant[GFO1130081]

Contrast-enhanced ultrasound in gallbladder disease: a pictorial review.

With its excellent contrast and spatial resolution, and the ability to image in real-time, ultrasound is the main imaging modality for assessing the gallbladder (GB). The application of contrast-enhanced ultrasound (CEUS) of the GB is now increasingly recognized as a useful addition to ultrasound and other cross-sectional imaging in the assessment of neoplastic and non-neoplastic GB disease. With the ability to image microcirculation and optimal contrast resolution, CEUS allows high-quality delineation in real-time, allowing for increased diagnostic confidence. In addition, ultrasound contrast agents have a favorable safety profile and can be used if CT or MR contrast agents are contraindicated or undesired. In this review, the CEUS appearances of a range of GB diseases encountered are presented, including adenomyomatosis, polyps, carcinoma, sludge, and cholecystitis with mural ulceration or perforation.

Respiration gating and Bloch fitting improve pH measurements with acidoCEST MRI in an ovarian orthotopic tumor model.

We have developed a MRI method that can measure extracellular pH in tumor tissues, known as acidoCEST MRI. This method relies on the detection of Chemical Exchange Saturation Transfer (CEST) of iopamidol, an FDA-approved CT contrast agent that has two CEST signals. A log10 ratio of the two CEST signals is linearly correlated with pH, but independent of agent concentration, endogenous T1 relaxation time, and B1 inhomogeneity. Therefore, detecting both CEST effects of iopamidol during in vivo studies can be used to accurately measure the extracellular pH in tumor tissues. Past in vivo studies using acidoCEST MRI have suffered from respiration artifacts in orthotopic and lung tumor models that have corrupted pH measurements. In addition, the non-linear fitting method used to analyze results is unreliable as it is subject to over-fitting especially with noisy CEST spectra. To improve the technique, we have recently developed a respiration gated CEST MRI pulse sequence that has greatly reduced motion artifacts, and we have included both a prescan and post scan to remove endogenous CEST effects. In addition, we fit the results by parameterizing the contrast of the exogenous agent with respect to pH via the Bloch equations modified for chemical exchange, which is less subject to over-fitting than the non-linear method. These advances in the acidoCEST MRI technique and analysis methods have made pH measurements more reliable, especially in areas of the body subject to respiratory motion.

Multifunctional pDNA-Conjugated Polycationic Au Nanorod-Coated Fe3 O4 Hierarchical Nanocomposites for Trimodal Imaging and Combined Photothermal/Gene Therapy.

It is very desirable to design multifunctional nanocomposites for theranostic applications via flexible strategies. The synthesis of one new multifunctional polycationic Au nanorod (NR)-coated Fe3 O4 nanosphere (NS) hierarchical nanocomposite (Au@pDM/Fe3 O4 ) based on the ternary assemblies of negatively charged Fe3 O4 cores (Fe3 O4 -PDA), polycation-modified Au nanorods (Au NR-pDM), and polycations is proposed. For such nanocomposites, the combined near-infrared absorbance properties of Fe3 O4 -PDA and Au NR-pDM are applied to photoacoustic imaging and photothermal therapy. Besides, Fe3 O4 and Au NR components allow the nanocomposites to serve as MRI and CT contrast agents. The prepared positively charged Au@pDM/Fe3 O4 also can complex plasmid DNA into pDNA/Au@pDM/Fe3 O4 and efficiently mediated gene therapy. The multifunctional applications of pDNA/Au@pDM/Fe3 O4 nanocomposites in trimodal imaging and combined photothermal/gene therapy are demonstrated using a xenografted rat glioma nude mouse model. The present study demonstrates that the proper assembly of different inorganic nanoparticles and polycations is an effective strategy to construct new multifunctional theranostic systems.

Differentiating Between Cancer and Inflammation: A Metabolic-Based Method for Functional Computed Tomography Imaging.

One of the main limitations of the highly used cancer imaging technique, PET-CT, is its inability to distinguish between cancerous lesions and post treatment inflammatory conditions. The reason for this lack of specificity is that [(18)F]FDG-PET is based on increased glucose metabolic activity, which characterizes both cancerous tissues and inflammatory cells. To overcome this limitation, we developed a nanoparticle-based approach, utilizing glucose-functionalized gold nanoparticles (GF-GNPs) as a metabolically targeted CT contrast agent. Our approach demonstrates specific tumor targeting and has successfully distinguished between cancer and inflammatory processes in a combined tumor-inflammation mouse model, due to dissimilarities in angiogenesis occurring under different pathologic conditions. This study provides a set of capabilities in cancer detection, staging and follow-up, and can be applicable to a wide range of cancers that exhibit high metabolic activity.

Novel Cs-Based Upconversion Nanoparticles as Dual-Modal CT and UCL Imaging Agents for Chemo-Photothermal Synergistic Therapy.

Lanthanide-based contrast agents have attracted increasing attention for their unique properties and potential applications in cancer theranostics. To date, many of these agents have been studied extensively in cells and small animal models. However, performance of these theranostic nanoparticles requires further improvement. In this study, a novel CsLu2F7:Yb,Er,Tm-based visual therapeutic platform was developed for imaging-guided synergistic cancer therapy. Due to the presence of the heavy alkali metal Cesium (Cs) in host lattice, the nanoplatform can provide a higher resolution X-ray CT imaging than many other reported lanthanide-based CT contrast agents. Furthermore, by using the targeted RGD motif, chemotherapy drug alpha-tocopheryl succinate (α-TOS), and photothermal coupling agent ICG, this nanoplatform simultaneously provides multifunctional imaging and targeted synergistic therapy. To demonstrate the theranostic performance of this novel nanoplatform in vivo, visual diagnosis in the small animal model was realized by UCL/CT imaging which was further integrated with targeted chemo-photothermal synergistic therapy. These results provided evidence for the successful construction of a novel lanthanide-based nanoplatform coupled with multimodal imaging diagnosis and potential application in synergistic cancer theranostics.

PEG-phospholipid-encapsulated bismuth sulfide and CdSe/ZnS quantum dot core–shell nanoparticle and its computed tomography/fluorescence performance

In this paper, polyethylene glycol-phospholipid structure is used to synthesize hybrid cluster of 40–50 nm diameter that contains hydrophobic bismuth sulfide nanoparticles and CdSe/ZnS quantum dots. The composite probe’s toxicity, CT imaging, and fluorescence imaging performance are also studied. Experimental results show that the nanocomposite hybrid cluster has obvious CT contrast enhancement and fluorescence imaging capability in vitro even after cellular uptake. It gives a CT number of 700 (Hounsfield units) at 15 mg/mL, higher than that of the current iobitridol CT contrast agent. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide experiment reveals that it has low cytotoxicity at concentration up to of 3.14 mg/mL of Bi, indicating the composite probe has potential ability for CT and fluorescence bimodal imaging.

VALIDATION OF [18F]-SODIUM FLUORIDE AS A MARKER OF ACTIVE CALCIFICATION AND HIGH-RISK CAROTID PLAQUE: A SUB-STUDY OF THE CANADIAN ATHEROSCLEROSIS IMAGING NETWORK (CAIN-2)

[18F]-sodium fluoride (NaF) positron emission tomography (PET) uptake may serve as an imaging-derived biomarker of active calcification. It is postulated that NaF binds to hydroxyapatite molecules that are expressed in regions with active calcification. We aimed to: 1. Validate NaF uptake imaged with PET/CT, as a direct marker of active calcification within carotid plaque, as determined by its association with intraplaque expression of hydroxyapatite; and 2. Determine whether NaF uptake is related to cerebrovascular events. Eleven patients (69 ± 5 years, 3 females) scheduled for carotid endarterectomy were prospectively recruited. Patients underwent NaF PET and contrast-enhanced CTA imaging of carotid vasculature. The bifurcation of the common carotid was used as a reference point; maximum NaF uptake normalized to blood (tissue to blood ratio - TBR) was measured at every PET slice extending 2 cm above and below the bifurcation. Following endarterectomy, excised carotid plaque was fixed, sectioned and stained with Goldner’s Trichrome (marker of hydroxyapatite expression). An electronic algorithm was applied to quantify hydroxyapatite expression on whole-slide digitized images. Using the distance from the bifurcation, pathology was aligned with CTA and co-registered with PET. To determine the relationship between NaF uptake and cerebrovascular events, bilateral carotid plaque was classified as either symptomatic (associated with cerebrovascular events) or clinically silent, asymptomatic plaque. Carotid endarterectomy was performed in 11 patients; one patient received a 2nd carotid endarterectomy due to bilateral disease. Two patients were excluded (intolerance to CT contrast agent and PET/CT misalignment). Staining was available for 8 excised plaques. NaF uptake was related to intraplaque hydroxyapatite expression (r=0.45, p<0.001) (Figure 1). NaF uptake was greater at the side of carotid endarterectomy (endarterectomy: 3.73±1.1 TBR vs. contralateral: 2.82±0.6 TBR, p=0.030). Symptomatic carotid plaque had evidence for greater NaF uptake (symptomatic plaque: 3.75±1.1 TBR vs. asymptomatic plaque: 2.79±0.6 TBR p=0.04) NaF uptake imaged with PET/CT is related to intraplaque expression of hydroxyapatite, which is expressed in regions with active calcific activity. NaF uptake was greater in plaque that was scheduled for endarterectomy, as well as symptomatic plaque associated with cerebrovascular events. NaF PET/CT may serve as a novel biomarker of active calcification and enable identification of high-risk patients. Larger outcome based follow-up studies are underway.

EANM procedural guidelines for radionuclide myocardial perfusion imaging with SPECT and SPECT/CT: 2015 revision.

Since the publication of the European Association of Nuclear Medicine (EANM) procedural guidelines for radionuclide myocardial perfusion imaging (MPI) in 2005, many small and some larger steps of progress have been made, improving MPI procedures. In this paper, the major changes from the updated 2015 procedural guidelines are highlighted, focusing on the important changes related to new instrumentation with improved image information and the possibility to reduce radiation exposure, which is further discussed in relation to the recent developments of new International Commission on Radiological Protection (ICRP) models. Introduction of the selective coronary vasodilator regadenoson and the use of coronary CT-contrast agents for hybrid imaging with SPECT/CT angiography are other important areas for nuclear cardiology that were not included in the previous guidelines. A large number of minor changes have been described in more detail in the fully revised version available at the EANM home page: http://eanm.org/publications/guidelines/2015_07_EANM_FINAL_myocardial_perfusion_guideline.pdf.

BaHoF5 nanoprobes as high-performance contrast agents for multi-modal CT imaging of ischemic stroke

CT angiography (CTA) and CT perfusion (CTP) imaging can play important roles in the workup of acute ischemic stroke. However, these techniques are hindered by the large amounts of contrast agents (CAs) required, high doses of X-ray radiation exposure, and nephrotoxicity of the clinical used iodinated CAs. To address these problems, we synthesized and validated a novel class of CT CAs, PEGylated BaHoF5 nanoparticles (NPs), for CTA and CTP imaging, which can greatly enhance the diagnostic sensitivity and accuracy of ischemic stroke. These agents have unique advantages over conventional iodinated CT agents, including much lower dosage required, major metabolism through liver and better imaging efficiency at different voltages. Once translated, these PEGylated BaHoF5 NPs can replace iodine-based CAs for diagnostic contrast-enhanced imaging of patients with kidney/heart diseases and improve the overall diagnostic index with negligible side effects.

Abstract 3685: Managing cervical cancer using multifunctional gold nanorods

Abstract Introduction: Treatment of, cervical cancer, the third most prevalent cancer in women, is challenged by resistance to chemo and radio therapy, organ toxicities and disease relapse which is mainly due to undiagnosed small metastases and failure in monitoring the course of treatment. Imaging is therefore another critical aspect in overall cancer management. We designed a triple combination treatment modality involving photo thermal therapy, EGFR mAb and GW627368X, an EP4 prostanoid receptor antagonist in a single nanoprobe which also serves as an efficient X-ray CT contrast agents. Methodology: Stimuli responsive, GW627368X loaded, EGFR mAb tagged gold nanorods(GNRs) were prepared by seed mediated method and characterized by TEM, NMR, IR and UV absorption spectroscopy. Cellular uptake of nanoparticles was studied by flow cytometry and fluorescent imaging. Drug release kinetics was studied prior to in vitro study. Cervical cancer cells, SiHa and ME180, were incubated with GNRs for 45mins, irradiated with cw-NIR laser (808nm) for various time periods and incubated for 12 hours. Cellular effects were studied by viability assays, flow cytometry, florescent staining, SEM, ELISA and western blot analysis. The X-ray attenuation property of nanoprobe was demonstrated by CT imaging of GNR incubated cervical cancer cells compared with untreated cells. Results: Due to surface plasmone resonance of GNRs, energy from incident NIR rays are converted into heat inducing apoptosis evident in viability assays further confirmed by flow cytometry, microscopy and western blot. Accumulation of the GNRs around the EGFR overexpressing transformed cells and subsequent uptake was confirmed microscopically and by increase in SSC of cells. EGFR blockade disrupts ligand receptor interaction down regulating survival pathways like Ras/MAPK, PI3K/Akt and JAK/STAT. Stimuli dependent drug release inhibits EP4 receptor in turn down regulating COX-2, PI3K/Akt and angiogenesis. Reduced VEGF, EGF and PGE-2 production was confirmed by ELISA and down regulation of pAkt, pMAPK, pEGFR, COX-2 and EP4 proteins was confirmed by western blot analysis. Prominently distinguishable CT attenuation was obtained with gold nanoprobes compared to untreated cells. Conclusion: EGFR mAb tagged, GW627368X loaded GNRs is novel therapeutic approach merging multiple strategies in single nanoprobe. Besides targeted accumulation, EGFR mAb disrupts EGFR signaling which along with stimuli dependent drug release block multiple downstream pathways. Photothermal therapy is highly efficient, selective approach as NIR has high tissue permeability but is harmless to normal tissue. Moreover, high X-ray atteneuation of gold makes it suitable a CT contrast agent for both diagnosis and monitoring the course of treatment. The proposed modality would thus prove to be highly efficient in overall management of cervical cancer. Citation Format: Sheetal Parida, Mahitosh Mandal. Managing cervical cancer using multifunctional gold nanorods. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3685. doi:10.1158/1538-7445.AM2015-3685

Quantitative spectral K-edge imaging in preclinical photon-counting x-ray computed tomography.

The objective of this study was to investigate the feasibility and the accuracy of spectral computed tomography (spectral CT) to determine the tissue concentrations and localization of high-attenuation, iodine-based contrast agents in mice. Iodine tissue concentrations determined with spectral CT are compared with concentrations measured with single-photon emission computed tomography (SPECT) and inductively coupled plasma mass spectrometry (ICP-MS). All animal procedures were performed according to the US National Institutes of Health principles of laboratory animal care and were approved by the ethical review committee of Maastricht, The Netherlands. Healthy Swiss mice (n = 4) were injected with an iodinated emulsion radiolabeled with indium as multimodal contrast agent for CT and SPECT. The CT and SPECT scans were acquired using a dedicated small-animal SPECT/CT system. Subsequently, scans were performed with a preclinical spectral CT scanner equipped with a photon-counting detector and 6 energy threshold levels. Quantitative data analysis of SPECT and spectral CT scans were obtained using 3-dimensional volumes-of-interest drawing methods. The ICP-MS on dissected organs was performed to determine iodine uptake per organ and was compared with the amounts determined from spectral CT and SPECT. Iodine concentrations obtained with image-processed spectral CT data correlated well with data obtained either with noninvasive SPECT imaging (slope = 0.96, r = 0.75) or with ICP-MS (slope = 0.99, r = 0.89) in tissue samples. This preclinical proof-of-concept study shows the in vivo quantification of iodine concentrations in tissues using spectral CT. Our multimodal imaging approach with spectral CT and SPECT using radiolabeled iodinated emulsions together with ICP-based quantification allows a direct comparison of all methods. Benchmarked against ICP-MS data, spectral CT in the present implementation shows a slight underestimation of organ iodine concentrations compared with SPECT but with a more narrow distribution. This slight deviation is most likely caused by experimental rather than technical issues.

Curricula for Teaching MRI Safety, and MRI and CT Contrast Safety to Residents: How Effective Are Live Lectures and Online Modules?

PurposeThe advent of the diagnostic radiology core examination and the new ACGME “milestone” evaluation system for radiology residents places new emphasis on topics in MRI and CT safety, and MRI and CT contrast agents. We evaluated whether either lecture-based teaching or online modules would improve baseline resident knowledge in these areas, and assessed which intervention was more effective. MethodsBefore didactic intervention, 2 cohorts were created from 57 radiology residents, with equal numbers and a matched level of training. The residents were tested on their baseline knowledge of MRI, MRI contrast safety, and CT contrast safety, using a multiple-choice examination. One group attended a live, 1-hour lecture on the preceding topics. The other engaged in 3 short online educational modules. After 6 weeks, the residents were again tested with the same questions to assess for improvement in their understanding. ResultsBoth the module and lecture cohorts demonstrated a statistically significant increase in questions answered correctly on CT contrast safety (13.1%, P < .001, and 19.1%, P < .001, respectively), and on MRI and MRI contrast safety (12.9%, P < .001, and 14.4%, P < .001). The preintervention and postintervention scores, and degree of improvement postintervention, were similar for the module versus lecture groups, without a statistically significant difference (P = .70). Resident confidence improved in both groups, for both modalities. ConclusionsFocused didactic intervention improves resident knowledge of MRI and CT safety, and MRI and CT contrast agents. Live lectures and online modules can be equally effective, allowing residency programs flexibility.

Feasibility of spectral CT imaging for the detection of liver lesions with gold-based contrast agents – A simulation study

PurposeTo demonstrate the feasibility of gold-specific spectral CT imaging for the detection of liver lesions in humans at low concentrations of gold as targeted contrast agent. MethodsA Monte Carlo simulation study of spectral CT imaging with a photon-counting and energy-resolving detector (with 6 energy bins) was performed in a realistic phantom of the human abdomen. The detector energy thresholds were optimized for the detection of gold. The simulation results were reconstructed with the K-edge imaging algorithm; the reconstructed gold-specific images were filtered and evaluated with respect to signal-to-noise ratio and contrast-to-noise ratio (CNR). ResultsThe simulations demonstrate the feasibility of spectral CT with CNRs of the specific gold signal between 2.7 and 4.8 after bilateral filtering. Using the optimized bin thresholds increases the CNRs of the lesions by up to 23% compared to bin thresholds described in former studies. ConclusionsGold is a promising new CT contrast agent for spectral CT in humans; minimum tissue mass fractions of 0.2 wt% of gold are required for sufficient image contrast.

SURGICAL MANAGEMENT OF TYPE B AORTIC DISSECTION AND PHEOCHROMOCYTOMA

Arterial hypertension is the most important risk factor for aortic dissection. Arterial hypertension has been found in approximately 80% of aortic dissection patients. Typically, arterial hypertension is long-standing and poorly regulated in aortic dissection patients. A pheochromocytoma is a rare, catecholamine-secreting tumour that may precipitate life-threatening hypertension. The tumour is malignant in 10% of cases but may be cured completely by surgical removal. We present the case of a 49-year-old patient, heavy smoker, hypertensive, who addressed the hospital in the context of acute interscapulovertebral pain (November 2014). After a contrast agent CT scan of the thorax + upper abdomen + pelvis, a type B thoracic aortic dissection was observed, without subdiaphragmatic extension or extension to the supraaortic trunks, without mediastinal effraction, and a right adrenal tumour of approximately 3.6 cm was also detected. The patient was directed to the cardiovascular surgery service, where an endoprosthesis with Vaillant prosthesis of the descending aorta and subclavian carotid bypass were performed, with good postoperative evolution. The patient was then referred to The National Institute of Endocrinology "C.I. Parhon" for further investigations required prior to the adrenal surgery. The suspicion of pheochromocytoma was confirmed by urinary metanephrine and normetanephrine dosing, and adrenal surgery was recommended. The patient was placed under alpha and beta blocker treatment for the prevention of hypertensive flares and any potential arrhythmias. Surgical intervention was performed for adrenal tumour resection. Histopathological examination of the surgical sample confirmed the diagnosis of pheochromocytoma. The particularity of the case is the discovery of an adrenal tumour due to an aortic dissection, the patient having no other symptoms and presenting a recorded history of hypertension.

Water‐Soluble, Monodisperse, Lanthanide‐Doped Y(Gd)VO4 Nanocrystals as Promising Multimodal Bioprobe

AbstractMonodisperse and water‐soluble lanthanide (Ln3+)‐doped Y(Gd)VO4 nanocrystals (NCs) have been successfully synthesized by a fast, facile, and environmentally friendly microwave‐assisted route with poly(acrylic acid) as the surfactant. The Y(Gd)VO4:5 %Ln3+ (Ln = Eu, Dy, Sm) NCs have unique fluorescence properties and polydimethylsiloxane (PDMS)‐based white solid nanocomposites containing YVO4:5 %Eu3+ NCs show red emission upon UV irradiation. GdVO4 NCs can act as CT and MRI contrast agents as a result of their magnetic and X‐ray absorption properties. A layer of SiO2 was coated onto the surfaces of the nanoparticles and MTT assays were carried out to test the cytotoxicity of the YVO4@SiO2 and GdVO4 NCs. The results indicate that the Y(Gd)VO4 NCs have potential in multimodal optical/MRI/CT bio‐imaging.