What is the diagnostic value of dual-energy computed tomography in patients with clinical diagnosis of gout?

Abstract Objectives: To investigate the frequency of monosodium urate (MSU) crystal deposits on dual-energy computed tomography (DECT) in patients with clinical diagnosis of gout and the factors associated MSU crystal positivity. Methods: This study was conducted in patients with clinical diagnosis of gout who underwent DECT. Clinical features were compared between patients with positive and those with negative DECT results. A logistic regression analysis was performed to determine the factors associated with MSU crystal positivity on DECT. Results: A total of 148 patients with clinical diagnosis of gout were included, and MSU crystal deposition on DECT was observed in 64 patients (43.3%). The patients with positive DECT results were more likely to have renal insufficiency, longer disease duration, and higher serum urate level than those with negative. In the multivariable analysis, first gout attack (odds ratio 0.462; 95% confidence interval 0.229-0.931, p = 0.031) was associated with a less likely MSU crystal deposit-positive DECT result. In the subgroup analysis of patients with first attack, serum urate level > 8 mg/dL was associated with DECT positivity. Conclusion: Of the patients with clinical diagnosis of gout, those with renal insufficiency, longer disease duration, and high serum urate level were more likely to be positive of gout on DECT. First gout attack was associated with less likely to be positive for MSU crystal on DECT. Thus, performing DECT scan in the selected patients who had characteristics that highly probability of DECT positivity could increase positive predictive value.

Relationship between Urate Crystal Deposits Detected by Dual-energy Computed Tomography and Bone Erosions in Symptomatic Gout Patients without Clinically Apparent Tophi

OBJECTIVE: Dual-energy computed tomography (DECT) allows sensitive detection of monosodium urate (MSU) crystal deposits in gout. However, the role of MSU deposits on DECT during the disease process of gout is not clear. The aim of our study was to evaluate the relationship between joint damage and MSU deposits detected by DECT in symptomatic non-tophaceous gout. METHODS: DECT scans of 51 gout patients without clinically apparent tophi were assessed. Individual ankle and foot joints and Achilles tendon insertion sites were evaluated for the presence of MSU deposits and bone erosions. The total volume of MSU crystal on DECT was quantified using an automated software program. Clinical and laboratory data at the time of the DECT evaluation were obtained from medical record. RESULTS: MSU deposits were detected in 92.2% of the patients evaluated. Median number and total volume of MSU deposit per patient was 5.0 and 0.6 cm3, respectively. Bone erosion was found in 54.9% of patients. MSU deposits in the first (1st) metatarsophalangeal (MTP) joints were significantly associated with presence of bone erosions (odds ratio [OR] 3.77, 95% confidence interval [CI] 1.06~13.38, p=0.040). Older age and frequent gout attack were associated with development of bone erosion in patients with MSU deposits (OR 1.12 and 2.57, 95% CI 1.04~1.22 and 1.02~6.50, p-value 0.004 and 0.047, respectively). CONCLUSION: MSU deposits and erosions were frequently detected by DECT in symptomatic non-tophaceous gout patients, and MSU deposits in 1st MTP joints were associated with presence of bone erosions especially in patients with older age and frequent gout attack.

Value of dual-energy CT-based volumetric iodine-uptake in the evaluation of chemotherapy efficacy in advanced gastric cancer / 中华胃肠外科杂志

Objective@#To explore the value of dual-energy CT-based volumetric iodine-uptake (VIU) in the evaluation of chemotherapy efficacy in advanced gastric cancer.@*Methods@#Inclusion criteria of subjects: (1) without previous systematic therapy; (2) with complete clinical information before and after chemotherapy; (3) without contraindications of chemotherapy. Exclusion criteria of subjects: (1) unfinished duration and times of chemotherapy; (2) unmeasurable primary lesions; (3) poor imaging quality or poor gastric filling. Clinical and image data of 52 patients with advanced gastric cancer who were diagnosed by pathology from gastroscopic biopsy, and needed chemotherapy evaluated by imaging and clinical information in the First Affiliated Hospital of Wenzhou Medical University from February 2017 to February 2018 were collected and analyzed. Of 52 patients, 38 were male and 14 were female with the median age of 65 (31-88) years old. All the patients underwent a dual-energy, dual phase-enhanced CT scanning before chemotherapy and after the third chemotherapy session. The parameters of the lesions measured before and after chemotherapy in portal vein phase were as follows: the maximum diameter (the largest diameter among those measured in the cross-sectional, coronal, and sagittal planes), average CT value (the regions of interest were manually pinpointed under cross-sectional planes with largest diameter of the tumor, which did not include regions less than 2 mm to the edge of the tumor) and VIU (lesion volume × iodine concentration). The change rates of maximum lesion diameter, average CT value and VIU before and after chemotherapy were calculated [(post-chemotherapy parameters-pre-chemotherapy parameters)/ pre-chemotherapy parameters]. The efficacy of chemotherapy was evaluated by RECIST 1.1 (the change of maximum tumor diameter after chemotherapy), Choi (the change of average CT value after chemotherapy) and VIU (the change of VIU after chemotherapy), respectively, which was categorized by complete response (CR), partial response (PR), stable disease (SD) and progressive disease (PD). Patients with CR, PR, and SD were assigned to the effective group, while those with PD were classified as the ineffective group. Paired t - test or Wilcoxon signed ranks test was used to compare the changes of parameters before and after chemotherapy, whereas Spearman correlation analysis and Kappa test were used for the correlation analysis and the consistency test between the three evaluation criteria (Kappa≥0.75 indicated good consistency).@*Results@#After chemotherapy, the average CT value [(74.01±16.75) HU vs. (81.06±15.87) HU, t=2.202, P=0.030] and median VIU (668.53×102 μg vs. 272.52×102 μg, Z=4.761, P<0.001) decreased significantly, while the difference of the maximum diameter was not statistically significant [(66.71±34.49) mm vs. (78.45±35.62) mm, t=1.708, P=0.091]. The median change rate of VIU (–53.33%) was greater than that of CT values (–5.75%) with significant difference (Z=-5.408, P<0.001). According to the RECIST 1.1 criteria, 47 patients (90.4%, including 19 with PR and 28 with SD) were effective and 5 patients (9.6%) were ineffective. According to the Choi criteria, 45 patients (86.5%, including 37 with PR and 8 with SD) were effective and 7 patients (13.5%) were ineffective. According to the VIU criteria, 46 patients (88.5%, including 41 with PR and 5 with SD) were effective and 6 patients (11.5%) were ineffective. Efficacy comparison among these three criteria showed no significant difference (χ2=0.377, P=0.828). As compared to RECIST 1.1 evaluation, the proportion of PR evaluated by Choi and VIU was significantly higher (χ2=16.861, P<0.001), whereas the proportion of SD was significantly lower (χ2=24.089, P<0.001). There was no significant difference in the proportions of PR and SD between VIU and Choi criteria (χ2=0.887, P=0.346). Consistency and correlation analysis showed that the VIU and Choi evaluation criteria presented the highest consistency and correlation (Kappa=0.912, P<0.001; r=0.916, P<0.001).@*Conclusion@#VIU is a feasible parameter for the evaluation of chemotherapy efficacy in advanced gastric cancer, and may be more sensitive than the evaluation criteria based on maximum diameter or change of CT value in the tumor.

Radiation dose reduction in chest dual-energy computed tomography: effect on image quality and diagnostic information / Redução da dose de radiação na tomografia computadorizada de dupla energia do tórax: efeito na qualidade das imagens e na informação diagnóstica

Abstract Objective: To determine whether dual-energy computed tomography (DECT) of the chest can be performed at a reduced radiation dose, with an emphasis on images generated with post-processing techniques. Materials and Methods: In 21 patients undergoing DECT of the chest in a dual-source scanner, an additional image series was acquired at a reduced radiation dose. Four thoracic radiologists assessed both image series for image quality, normal thoracic structures, as well as pulmonary and mediastinal abnormalities, on virtual monochromatic images at 40 keV and 60 keV. Data were analyzed with Student's t-test, kappa statistics, analysis of variance, and the Wilcoxon signed-rank test. Results: The overall image quality of 60 keV virtual monochromatic images at a reduced radiation dose was considered optimal in all patients, and no abnormalities were missed. Contrast enhancement and lesion detection performance were comparable between reduced-dose images at 40 keV and standard-of-care images at 60 keV. The intraobserver and interobserver agreement were both good. The mean volumetric CT dose index (CTDIvol), size-specific dose estimate (SSDE), dose-length product (DLP), and effective dose (ED) for reduced-dose DECT were 3.0 ± 0.6 mGy, 4.0 ± 0.6 mGy, 107 ± 30 mGy.cm, and 1.5 ± 0.4 mSv, respectively. Conclusion: DECT of the chest can be performed at a reduced radiation dose (CTDIvol < 3 mGy) without loss of diagnostic information.

Resumo Objetivo: Verificar se a tomografia computadorizada de dupla energia (TCDE) do tórax pode ser realizada com baixas doses de radiação, com ênfase em imagens pós-processadas. Materiais e Métodos: Em 21 pacientes submetidos a DECT do tórax foi adicionada uma série de imagens adquiridas com baixas doses de radiação. Quatro radiologistas com especialidade em tórax avaliaram a qualidade, visualização de estruturas torácicas normais e também anormalidades pulmonares e mediastinais das imagens monocromáticas de baixa energia (40 e 60 keV). Os dados foram analisados utilizando t-test, estatística kappa, análise de variância e teste Wilcoxon. Resultados: A qualidade das imagens monocromáticas de baixa energia (60 keV) com doses reduzidas foi considerada ótima para todos os pacientes e nenhuma anormalidade no tórax foi perdida. O realce pelo contraste e a performance de detecção de lesões foram similares nas imagens com radiação reduzida e com radiação padrão. Boa concordância intra-avaliadores e interavaliadores foi observada. A média dos parâmetros CTDIvol, SSDE, DLP e ED para TCDE de baixa dose foram 3,0 ± 0,6 mGy, 4,0 ± 0,6 mGy, 107 ± 30 mGy.cm e 1,5 ± 0,4 mSv, respectivamente. Conclusão: TCDE do tórax pode ser realizada com baixas doses de radiação (CTDIvol < 3 mGy), sem perder informações diagnósticas.

Iodine Quantification on Spectral Detector-Based Dual-Energy CT Enterography: Correlation with Crohn's Disease Activity Index and External Validation

OBJECTIVE: To correlate CT parameters on detector-based dual-energy CT enterography (DECTE) with Crohn's disease activity index (CDAI) and externally validate quantitative CT parameters. MATERIALS AND METHODS: Thirty-nine patients with CD were retrospectively enrolled. Two radiologists reviewed DECTE images by consensus for qualitative and quantitative CT features. CT attenuation and iodine concentration for the diseased bowel were also measured. Univariate statistical tests were used to evaluate whether there was a significant difference in CTE features between remission and active groups, on the basis of the CDAI score. Pearson's correlation test and multiple linear regression analyses were used to assess the correlation between quantitative CT parameters and CDAI. For external validation, an additional 33 consecutive patients were recruited. The correlation and concordance rate were calculated between real and estimated CDAI. RESULTS: There were significant differences between remission and active groups in the bowel enhancement pattern, subjective degree of enhancement, mesenteric fat infiltration, comb sign, and obstruction (p < 0.05). Significant correlations were found between CDAI and quantitative CT parameters, including number of lesions (correlation coefficient, r = 0.573), bowel wall thickness (r = 0.477), iodine concentration (r = 0.744), and relative degree of enhancement (r = 0.541; p < 0.05). Iodine concentration remained the sole independent variable associated with CDAI in multivariate analysis (p = 0.001). The linear regression equation for CDAI (y) and iodine concentration (x) was y = 53.549x + 55.111. For validation patients, a significant correlation (r = 0.925; p < 0.001) and high concordance rate (87.9%, 29/33) were observed between real and estimated CDAIs. CONCLUSION: Iodine concentration, measured on detector-based DECTE, represents a convenient and reproducible biomarker to monitor disease activity in CD.

The acceleration algorithm for projection decomposition of dual-energy computed tomography image reconstruction based on projection matching / 生物医学工程学杂志

Dual-energy computed tomography (CT) reconstruction imaging technology is an important development direction in the field of CT imaging. The mainstream model of dual-energy CT reconstruction algorithm is the basis material decomposition model, and the projection decomposition is the crucial technique. The projection decomposition algorithm based on projection matching was a general method. With establishing the energy spectrum lookup table, we can obtain the stable solution by the least squares matching method. But the computation cost will increase dramatically when size of lookup table enlarges and it will slow down the computer. In this paper, an acceleration algorithm based on projection matching is proposed. The proposed algorithm makes use of linear equations and plane equations to fit the lookup table data, so that the projection value of the decomposition coefficients can be calculated quickly. As the result of simulation experiment, the acceleration algorithm can greatly shorten the running time of the program to get the stable and correct solution.

Relevant aspects of imaging in the diagnosis and management of gout / Aspectos relevantes do diagnóstico e seguimento por imagem na gota

ABSTRACT Gout is an inflammatory arthritis characterized by the deposition of monosodium urate crystals in the synovial membrane, articular cartilage and periarticular tissues leading to inflammation. Men are more commonly affected, mainly after the 5th decade of life. Its incidence has been growing with the population aging.In the majority of the cases, the diagnosis is made by clinical criteria and synovial fluid analysis, in search for monosodium urate crystals. Nonetheless, gout may sometimes have atypical presentations, complicating the diagnosis. In these situations, imaging methods have a fundamental role, aiding in the diagnostic confirmation or excluding other possible differential diagnosis. Conventional radiographs are still the most commonly used method in gout patients’ evaluation; nevertheless, this is not a sensitive method, since it detect only late alterations. In the last years, there have been several advances in imaging methods for gout patients. Ultrasound has shown a great accuracy in the diagnosis of gout, identifying monosodium urate deposits in the synovial membrane and articular cartilage, in detecting and characterizing tophi and in identifying tophaceous tendinopathy and enthesopathy. Ultrasound has also been able to show crystal deposition in patients with articular pain in the absence of a classical gout crisis. Computed tomography is an excellent method for detecting bone erosions, being useful in spine involvement. Dual-energy CT is a new method able to provide information about the chemical composition of tissues, with high accuracy in the identification of monosodium urate deposits, even in the early stages of the disease and in cases of difficult characterization. Magnetic resonance imaging is useful in the evaluation of deep tissues not accessible by ultrasound. Besides the diagnosis, with the emergence of new drugs that aim to reduce tophaceous burden, imaging methods have become useful tools in monitoring the treatment of patients with gout.

RESUMO A gota é uma artrite caracterizada pela deposição de cristais de monourato sódico na membrana sinovial, na cartilagem articular e nos tecidos periarticulares que leva a um processo inflamatório. Na maioria dos casos o diagnóstico é estabelecido por critérios clínicos e pela análise do líquido sinovial, em busca dos cristais de MSU. Porém, a gota pode se manifestar de maneiras atípicas e dificultar o diagnóstico. Nessas situações, os exames de imagem têm papel fundamental, auxiliam na confirmação diagnóstica ou ainda excluem outros diagnósticos diferenciais. A radiografia convencional ainda é o método mais usado no acompanhamento desses pacientes, porém é um exame pouco sensível, por detectar somente alterações tardias. Nos últimos anos, surgiram avanços nos métodos de imagem em relação à gota. O ultrassom se mostra um exame de grande acurácia no diagnóstico de gota, identifica depósitos de MSU na cartilagem articular e nos tecidos periarticulares e detecta e caracteriza tofos, tendinopatias e entesopatias por tofos. A tomografia computadorizada é um ótimo exame para a detecção de erosões ósseas e avaliação do acometimento na coluna. A tomografia computadorizada de dupla-energia, um método novo, fornece informações sobre a composição química dos tecidos, permite a identificação dos depósitos de MSU com elevada acurácia. A ressonância magnética pode ser útil na avalição dos tecidos profundos, não acessíveis ao ultrassom. Além do diagnóstico, com o surgimento de drogas que visam reduzir a carga tofácea, os exames de imagem se tornam uma ferramenta útil no acompanhamento do tratamento dos pacientes com gota.

Dual-energy CT virtual non-contrast technology in the diagnosis of osteoporosis: a preliminary study / 中华放射学杂志

Objective To investigate the diagnostic value of dual-energy CT virtual non-contrast (VNC) technology for osteoporosis(OP). Methods Dual-energy CT images of 50 patients with lumbar traumas were collected prospectively.Patients who suffer from vertebral bodies fractures between lumbar 1 to 4, have internal metal fixations or underwent percutaneous vertebroplasty, or presented tumors or compromised bone metabolism induced by diseases or medications were excluded.The scanning range was from the upper edge of the 12th thoracic vertebral body to the lower edge of the first sacral vertebral body. The voltages of tubes A and B were 90 kV and Sn 150 kV,and the reference tubes currents were 220 mAs and 138 mAs. Image reconstruction was performed using Advanced Modeled Iterative Reconstruction (ADMIRE)with iterative strength of 3 and convolution kernel of Qr 40.The default parameters of the virtual non-contrast software were corrected by the standard recommended by the Bone Marrow software of the post-processing platform Syngo.via,and the CT value of calcium(contrast media CM),the CT value of mixed energy images(regular CT value,rCT),the calcium density(CaD)and the fat fraction(Fat)were measured. The bone mineral density (BMD) and T score of each lumbar vertebra from lumbar 1 to lumbar 4 were measured by dual energy X-ray absorptiometry(DXA).With T score less than or equal to the 2.5 standard deviation as the gold standard for the diagnosis of OP,correlations between CT measurements and vertebral BMDs were analyzed using Pearson correlation analysis and linear regression and the diagnostic values of different CT measurements for OP were compared using receiver operating characteristic curve. Results Each of the vertebral bodies was analyzed as a single unit.Fifty of them were osteoporotic and the rest 116 were non-osteoporotic.Except for Fat,the CT measurement parameters of the osteoporotic vertebral bodies were lower than those of the ones without osteoporosis, and the difference was statistically significant (P<0.01).CM,rCT and CaD were significantly correlated with BMD(r were 0.75,0.65,0.71,all P<0.01)and there was a linear relationship(F were 209.91,120.24,167.69,all P<0.01).Meanwhile,CM,rCT,CaD and T score were also significantly correlated (r were 0.74, 0.65, 0.70, all P<0.01) with a linear relationship (F were 195.04,120.29,156.37,all P<0.01).CM,rCT and CaD had relatively high concordance rates against the OP diagnosis gold standard (respectively 81.9%, 62.2% and 81.9%). CM and CaD had higher concordance rates than rCT,the difference being statistically significant(P<0.01),and by the CM less than 239.5 HU or CaD less than 10.9 mg/cm3standard, their sensitivities of diagnosing osteoporosis were respectively 86.0% and 84.0%,while the specificities,80.2% and 81.0%.After superimposing CM and CaD, the results did not improve the diagnosis efficiency of OP (pre-superposition diagnostic performance better than post-superposition (P<0.05). Conclusion The VNC technology on DECT can do both vertebral fractures diagnosis and osteoporosis assessment at the same time, thus optimizing the clinical examination process.

Clinics in diagnostic imaging (167). Total shoulder arthroplasty glenoid component loosening with secondary rotator cuff failure

A 59-year-old woman who had previously undergone an anatomic left total shoulder arthroplasty presented with increasing left shoulder pain and significant reduction in motion of the left shoulder joint. No evidence of prosthetic loosening or periprosthetic fracture was detected on the radiographs or fluoroscopic arthrogram images. Dual-energy computed tomography (DECT) images revealed evidence of loosening of the glenoid component and secondary rotator cuff failure. This case illustrates how a combination of detailed clinical history, careful physical examination and DECT arthrogram evaluation may be used to identify complications of an anatomic total shoulder arthroplasty.

Estudo da perfusão pulmonar por angiotomografia computadorizada em pacientes com hipertensão pulmonar / Pulmonary perfusion imaging derived from computed tomography pulmonary angiograms in patients with pulmonary hypertension

Introdução: A hipertensão arterial pulmonar (HAP) é uma doença grave da circulação pulmonar, cujo diagnóstico e cuja avaliação funcional dependem do cateterismo cardíaco direito. A tomografia de dupla energia (TCDE), por meio da técnica de decomposição de materiais, permite obter um mapa de Iodo do parênquima pulmonar, que pode ser avaliado de forma qualitativa e quantitativa, e pode ser útil na avaliação da HAP. Objetivos: Avaliar a distribuição de Iodo no parênquima pulmonar, comparando com marcadores hemodinâmicos, marcadores de gravidade e com grupo-controle normopressórico. Métodos: Pacientes com HAP, acompanhados na Unidade de Circulação Pulmonar (InCor-HCFMUSP), foram avaliados por angiotomografia das artérias pulmonares (angioTC) como parte de sua rotina diagnóstica, em modo de dupla energia. O grupo-controle foi composto por pacientes com suspeita clínica de tromboembolismo pulmonar (TEP), com angioTC negativa para TEP e com ecocardiograma normal. Foram avaliadas as concentrações de Iodo no pulmão (mg/mL) por meio de 8 regiões de interesse redondas com 1 cm2 de área, distribuídas ao longo do eixo ântero-posterior do pulmão direito, em 3 níveis predeterminados. Foram obtidas, também, as medidas do ventrículo direito (VD), ventrículo esquerdo (VE), razão VD/VE, diâmetros da aorta (AO) e artéria pulmonar (AP). O realce da artéria pulmonar por meio da TCDE (PAenh) também foi obtido. Os resultados foram comparados entre os grupos, e correlacionados no grupo HAP com parâmetros hemodinâmicos invasivos e marcadores de gravidade. Resultados: O grupo HAP foi composto por 21 pacientes, com idade média de 42 anos, 47,6% em classe funcional I/II. Houve diferença significativa nos diâmetros da AP (p<0,01), VD (p<0,01), e VE (p=0,01), entre os grupos HAP e controle. Também demonstraram diferenças significativas às relações entre os diâmetros AP/AO (p < 0,01) e VD/VE (p < 0,01)...

Background: Pulmonary arterial hypertension (PAH) is a severe disease of the pulmonary circulation. Right heart catheterization (RHC) is crucial for diagnosis and management of these patients. High-resolution computed tomography (CT) and CT angiography play a crucial role in the diagnostic work-up of pulmonary hypertension. Dual energy computed tomography (DECT) is a technique of acquisition of modern CT scanners that allows obtaining a computed tomography of the pulmonary arteries with low iodine dose, and providing an estimation of iodine distribution in the lungs. Although the search for non-invasive methods for evaluation of PAH is developing, data concerning application of DECT on PAH patients remain scarce. Objectives: To evaluate the iodine distribution in the lungs obtained by DECT in PAH patients and a control group and compare to the hemodynamic profile, and prognostic markers of PAH patients. Methods: 21 patients followed at the Pulmonary Circulation Unit (InCor-HCFMUSP) and submitted to CT angiography were evaluated by DECT. A matched control group was composed by patients routinely referred to CT angiography to rule out pulmonary embolism with negative results and also a normal echocardiogram obtained at the same day. Eight circular 1cm2 ROIs were placed along the anteroposterior axis, at the middle of the right lung and at predetermined levels to measure the Iodine concentration in the lungs. Measurements of the pulmonary artery (PA), ascending aorta (AO), right ventricle (RV) and left ventricles (LV) were obtained, as well as enhancement of the PA (PAenh). Results were compared to the control group, and correlated with hemodynamic parameters in the PAH group. Results: PAH patients averaged 42 y/o, female/male ratio of 7/1, NYA functional classes I/II. Statistically significant differences between PAH patients and controls were found regarding measurements of PA (p < 0,01), RV (p < 0,01), LV (p=0,01), PA/AO (p < 0,01) and RV/LV (p < 0,01)...

Dual-Energy Computed Tomography Arthrography of the Shoulder Joint Using Virtual Monochromatic Spectral Imaging: Optimal Dose of Contrast Agent and Monochromatic Energy Level

OBJECTIVE: To optimize the dose of contrast agent and the level of energy for dual-energy computed tomography (DECT) arthrography of the shoulder joint and to evaluate the benefits of the optimized imaging protocol. MATERIALS AND METHODS: Dual-energy scans with monochromatic spectral imaging mode and conventional single energy scans were performed on a shoulder phantom with 10 concentrations from 0 to 210 mg/mL of iodinated contrast medium at intervals of 15 or 30 mg/mL. Image noise, tissue contrast, and beam hardening artifacts were assessed to determine the optimum dose of contrast agent and the level of monochromatic energy for DECT shoulder arthrography in terms of the lowest image noise and the least beam hardening artifacts while good tissue contrast was maintained. Material decomposition (MD) imaging for bone-iodine differentiation was qualitatively assessed. The optimized protocol was applied and evaluated in 23 patients. RESULTS: The optimal contrast dose and energy level were determined by the phantom study at 60 mg/mL and 72 keV, respectively. This optimized protocol for human study reduced the image noise and the beam-hardening artifacts by 35.9% and 44.5%, respectively. Bone-iodine differentiation by MD imaging was not affected by the iodine concentration or level of energy. CONCLUSION: Dual-energy scan with monochromatic spectral imaging mode results in reduced image noise and beam hardening artifacts.

The value of dual energy computed tomography for the diagnosis of gout / 中华风湿病学杂志

Objective To evaluate the value of dual energy computed tomography (DECT) for the diagnosis of gout.Methods Twenty-fivc consccutive patients with gout were selected as the experimental group and 20 patients with rheumatoid arthritis (RA) were selected as the control group.DECT scans were performed for every patient (all peripheral joints for the experimental group and affected joints for the control group).And every patient with gout had X-ray examination of the involved joints.x2 test and t-test were used for statistical analysis.Results All 25 patients with gout showed urate deposits on their DECT scans,whereas none of 20 controls showed urate deposits (P＜0.01).DECT scans revealed a total of 184 areas of urate deposition in 25 patients,in which 107 (58.2％) were at feet and ankle,72 (39.1％) were at knees,4 (2.2％) were at hands and wrists,1 (0.5％) was at elbows,whereas physical examination only showed 64 areas of urate deposition,in which 38(59.4％) were at feet and ankle,24(37.5％) were at knees,2(3.1％) at hands and wrists,0 was at elbows(P＜0.01 ).Only 6 patients with gout showed nonspecific manifestations on X-ray.Conclusion DECT scans may have potential value for the diagnosis of gout since it could produce evident colour displays for urate deposits and help to identify subclinical tophus deposits.

IMAGE-QUALITY OPTIMIZATION FOR DUAL ENERGY COMPUTED TOMOGRAPHY (DECT) THREE-MATERIAL DECOMPOSITION / OPTIMIZACIÓN DE LA CALIDAD DE LA IMAGEN PARA LA SEPARACIÓN DE TRES MATERIALES UTILIZANDO LA TOMOGRAFÍA COMPUTARIZADA DE DOS ENERGÍAS (TCDE)

Dual energy computed tomography, which consists of the acquisition of two images of a given region of interest using two different x-ray energies, has been used to decompose images. For example, it has been proposed to estimate the degree of stenosis of blood vessels with calcified plaques. Pragmatic realities, though, such as beam hardening, scattered radiation and mostly quantum noise, reduce the ideal of a perfect decomposition. In this study, a dual energy separation method for iodinated contrast media, cortical bone and soft tissue was implemented; afterwards, it was tested in simulated noiseless and noisy situations. The noise propagation was modeled mathematically, and an image-quality optimization technique regarding the right distribution of radiation dose between the high and low energy images was proposed. The results obtained suggest that in the absence of noise and using mono-energetic beams, an accurate separation is possible, but when noise is added and poly-chromatic spectra used this decomposition becomes more challenging.

La tomografía computarizada de dos energías, que consiste en la adquisición de dos imágenes de una región de interés dada usando rayos X de dos energías distintas, ha sido utilizada para descomponer imágenes. Por ejemplo, esta técnica ha sido propuesta para estimar el grado de estenosis de vasos sanguíneos obstruidos con placas de calcio. Sin embargo, fenómenos como el endurecimiento del rayo, la radiación dispersada y principalmente el ruido cuántico, impiden que esta separación sea perfecta. En este estudio, se implementó un método de separación de medio de contraste yodado, tejido blando y hueso cortical; este se evaluó en simulaciones, tanto en presencia como en ausencia de ruido. Posteriormente, se modeló matemáticamente la propagación del ruido y, con base en los resultados de estos modelos, se propuso una técnica de optimización de la imagen basada en la distribución adecuada de la dosis de radiación entre las imágenes de energías alta y baja. Los resultados evidencian que en ausencia de ruido y con rayos mono-energéticos, es posible obtener una separación precisa, pero cuando se adiciona ruido a las imágenes y se trabaja con espectros policromáticos, la descomposición resulta más complicada.