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1.
J Comput Assist Tomogr ; 44(2): 223-229, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32195800

RESUMO

OBJECTIVES: This study aimed to assess if dual-energy computed tomography (DECT) quantitative analysis and radiomics can differentiate normal liver, hepatic steatosis, and cirrhosis. MATERIALS AND METHODS: Our retrospective study included 75 adult patients (mean age, 54 ± 16 years) who underwent contrast-enhanced, dual-source DECT of the abdomen. We used Dual-Energy Tumor Analysis prototype for semiautomatic liver segmentation and DECT and radiomic features. The data were analyzed with multiple logistic regression and random forest classifier to determine area under the curve (AUC). RESULTS: Iodine quantification (AUC, 0.95) and radiomic features (AUC, 0.97) differentiate between healthy and abnormal liver. Combined fat ratio percent and mean mixed CT values (AUC, 0.99) were the strongest differentiators of healthy and steatotic liver. The most accurate differentiating parameters of normal liver and cirrhosis were a combination of first-order statistics (90th percentile), gray-level run length matrix (short-run low gray-level emphasis), and gray-level size zone matrix (gray-level nonuniformity normalized; AUC, 0.99). CONCLUSION: Dual-energy computed tomography iodine quantification and radiomics accurately differentiate normal liver from steatosis and cirrhosis from single-section analyses.


Assuntos
Fígado Gorduroso/diagnóstico por imagem , Cirrose Hepática/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Meios de Contraste , Diagnóstico Diferencial , Estudos de Avaliação como Assunto , Feminino , Humanos , Fígado/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Intensificação de Imagem Radiográfica/métodos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Estudos Retrospectivos
2.
J Comput Assist Tomogr ; 44(1): 78-82, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31939886

RESUMO

OBJECTIVE: This study aimed to evaluate virtual monochromatic images (VMIs) obtained using dual-layer dual-energy computed tomography (CT) for breast carcinoma. METHODS: We retrospectively enrolled 28 patients with breast cancer who were pathologically diagnosed using dual-layer dual-energy CT. Virtual monochromatic images (40-200 keV) were generated. We compared CT number, image noise, contrast, and contrast-to-noise ratio (CNR) between VMIs with the highest CNR and conventional CT images. We performed qualitative image analysis between VMIs at optimized energy and conventional CT images. RESULTS: Image noise of VMIs was not significantly different from that of the conventional CT images. As the x-ray energy decreased, CNR increased. The 40-keV VMIs were highest CNR and higher than that of the conventional CT images. In qualitative image analysis, the 40-keV images were significantly higher than conventional CT images. CONCLUSION: Both qualitative and quantitative analyses showed that the image quality of VMIs at 40 keV was significantly higher than that of conventional CT images.


Assuntos
Neoplasias da Mama/diagnóstico por imagem , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Pessoa de Meia-Idade , Intensificação de Imagem Radiográfica , Interpretação de Imagem Radiográfica Assistida por Computador , Estudos Retrospectivos , Razão Sinal-Ruído
3.
J Comput Assist Tomogr ; 44(1): 138-144, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31939895

RESUMO

OBJECTIVE: The aim of this study was to determine the influence of virtual monoenergetic images (vMEIs) on renal cortex volumetry (RCV) and estimation of split-renal function. METHODS: Twenty-five patients (mean ± SD, 64.7 ± 9.9 years) underwent a contrast-enhanced dual-layer spectral detector computed tomography. Images were reconstructed with a reference standard (iterative model reconstruction, IMRRef), a newly spectral detector computed tomography algorithm (SPcon) and vMEI at 40, 60, 80, 100, and 120 keV. Two blinded independent readers performed RCV on all data sets with a semiautomated tool. RESULTS: Total kidney volume was up to 15% higher in vMEI at 40/60 keV compared with IMRRef (P < 0.001). Total kidney volume with vMEI at 80/100 keV was similar to IMRRef (P < 0.001). Split-renal function was similar in all reconstructions at approximately 50% ± 3%. Bland-Altman analysis showed no significant differences (P > 0.05), except for 40 keV versus SPcon (P < 0.05). The time required to perform RCV was reasonable, approximately 4 minutes, and showed no significant differences among reconstructions. Interreader agreement was greatest with vMEI at 80 keV (r = 0.68; 95% confidence interval, 0.39-0.85; P < 0.0002) followed by IMRRef images (r = 0.67; 95% confidence interval, 0.37-0.84; P < 0.0003). IMRRef showed the highest mean Hounsfield unit for cortex/medulla of 223.4 ± 73.7/62.5 ± 19.7 and a ratio of 3.7. CONCLUSIONS: Semiautomated RCV performed with vMEI and IMRRef/SPcon is feasible and showed no clinically relevant differences with regard to split-renal function. Low-kiloelectron volt vMEI showed greater tissue contrast and total kidney volume but no benefit for RCV. Moderate-kiloelectron volt vMEI (80 keV) results were similar to IMRRef with a faster postprocessing time.


Assuntos
Córtex Renal/diagnóstico por imagem , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Idoso , Algoritmos , Feminino , Humanos , Córtex Renal/patologia , Masculino , Pessoa de Meia-Idade , Variações Dependentes do Observador , Estudos Retrospectivos , Sensibilidade e Especificidade , Razão Sinal-Ruído
4.
Br J Radiol ; 93(1107): 20190590, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31642709

RESUMO

Pre-treatment CT imaging is a topic of growing importance in particle therapy. Improvements in the accuracy of stopping-power prediction are demanded to allow for a dose conformality that is not inferior to state-of-the-art image-guided photon therapy. Although range uncertainty has been kept practically constant over the last decades, recent technological and methodological developments, like the clinical application of dual-energy CT, have been introduced or arise at least on the horizon to improve the accuracy and precision of range prediction. This review gives an overview of the current status, summarizes the innovations in dual-energy CT and its potential impact on the field as well as potential alternative technologies for stopping-power prediction.


Assuntos
Terapia com Prótons , Radioterapia Guiada por Imagem/métodos , Tomografia Computadorizada por Raios X/métodos , Incerteza , Algoritmos , Humanos , Imagem por Ressonância Magnética , Fótons/uso terapêutico , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/instrumentação , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Radioterapia Guiada por Imagem/instrumentação , Tomografia Computadorizada por Raios X/instrumentação
5.
Br J Radiol ; 93(1106): 20180850, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31825643

RESUMO

OBJECTIVE: Determination of the optimal energy level of virtual monochromatic image (VMI) for brain metastases in contrast-enhanced dual-energy CT (DECT) for radiosurgery and assessment of the subjective and objective image quality of VMI at the optimal energy level. METHODS: 20 patients (total of 42 metastases) underwent contrast-enhanced DECT. Spectral image analysis of VMIs at energy levels ranging from 40 to 140 keV in 1 keV increments was performed to determine the optimal VMI (VMIopt) as the one corresponding to the highest contrast-to-noise ratio (CNR) between brain parenchyma and the metastases. The objective and subjective values of VMIopt were compared to those of the VMI with 120 kVp equivalent, defined as reference VMI (VMIref, 77 keV). The objective measurement parameters included mean HU value and SD of tumor and brain parenchyma, absolute lesion contrast (LC), and CNR. The subjective measurements included five-point scale assessment of "overall image quality" and "tumor delineation" by three radiation oncologists. RESULTS: The VMI at 63 keV was defined as VMIopt. The LC and CNR of VMIopt were significantly (p < 0.01) higher than those of VMIref (LC: 37.4 HU vs 24.7 HU; CNR: 1.1 vs 0.8, respectively). Subjective analysis rated VMIopt significantly (p < 0.01) superior to VMIref with respect to the overall image quality (3.2 vs 2.9, respectively) and tumor delineation (3.5 vs 2.9, respectively). CONCLUSION: The VMI at 63 keV derived from contrast-enhanced DECT yielded the highest CNR and improved the objective and subjective image quality for radiosurgery, compared to VMIref. ADVANCES IN KNOWLEDGE: This paper investigated for the first time the optimal energy level of VMI in DECT for brain metastases. The findings will lead to improvement in tumor visibility with optimal VMI and consequently supplement accuracy delineation of brain metastases.


Assuntos
Neoplasias Encefálicas/radioterapia , Radiocirurgia/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/secundário , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Radioterapia Guiada por Imagem , Estudos Retrospectivos , Tomografia Computadorizada por Raios X/métodos , Carga Tumoral , Adulto Jovem
6.
Eur Radiol ; 30(1): 394-403, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31312889

RESUMO

OBJECTIVES: To evaluate the image quality and optimal energies of virtual monoenergetic images (VMIs) from dual-layer spectral detector computed tomography (DLCT) in multiphasic pancreatic CT and investigate whether low-keV VMI at the portal venous phase (PVP) provides sufficient tumor conspicuity and arterial depiction relative to conventional pancreatic parenchymal phase (PPP) images. METHODS: Forty-eight patients with pancreatic ductal adenocarcinoma (PDAC) underwent contrast-enhanced DLCT during PPP and PVP. Conventional polyenergetic images (PEIs) and VMI at 40-100 keV (VMI40-100, 10-keV increments) were reconstructed at each enhancement phase. Image noise and the contrast-to-noise ratio (CNR) of the pancreas, tumors, arteries, and veins were quantified. Two radiologists independently assessed tumor conspicuity, margin delineation, image noise, sharpness of pancreatic duct, and depiction of arteries and veins on a five-point scale. Size-specific dose estimate (SSDE) was calculated. RESULTS: Image noise for VMI40-100 was significantly lower than that for PEI (p < 0.01). The CNR in VMI increased gradually with decreasing energy; CNRs for VMI40-60 were significantly greater than that for PEI (p < 0.01). All subjective VMI scores were maximized at VMI40, followed by VMI50-60, all of which were significantly better than of PEI (p < 0.01). Objective and subjective image qualities of VMI40-50 at the PVP were equivalent to or even better compared with conventional PPP images. No significant difference in SSDE was observed between phases (p = 0.10). CONCLUSIONS: DLCT-VMI improved the subjective and objective image quality in multiphasic pancreatic CT for patients with PDAC. Low-keV PVP imaging may yield diagnostically adequate tumor conspicuity and arterial assessment compared with polyenergetic PPP images. KEY POINTS: • Low-keV VMI from DLCT yields better subjective and objective image quality of multiphasic pancreas CT in comparison with conventional PEI for the assessment of pancreatic ductal adenocarcinoma. • Tumor conspicuity and depiction of peripancreatic vasculature were maximized at VMI 40without an increase in the image noise. • Low-keV VMI of the portal venous phase provides sufficient tumor conspicuity and arterial depiction, potentially allowing the early detection and local staging of PDAC on routine abdominal CT performed for various clinical indications.


Assuntos
Carcinoma Ductal Pancreático/diagnóstico por imagem , Pâncreas/diagnóstico por imagem , Neoplasias Pancreáticas/diagnóstico por imagem , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Adulto , Idoso , Algoritmos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Razão Sinal-Ruído
7.
Eur Radiol ; 30(1): 404-412, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31332560

RESUMO

OBJECTIVES: To develop a method that allows approximating the mass of monosodium uric acid (MSU) in a gouty tophus using phantom measurements and including tophus density into the calculation of the dual-energy computed tomography (DECT) tophus volumetry. METHODS: We prepared specimens of different concentrations of MSU placed in an epoxy-based phantom and an excised porcine foreleg. Density and volumetric measurements were performed in sequential single-source DECT scans acquired with increasingly higher tube currents. We developed a method for estimating the tophus mass by multiplying the detected tophus volume with its mean density and adding a specific gravimetric coefficient k. k was derived from the DECT scans by comparing the approximated MSU masses in the epoxy phantom with the known true MSU masses of the specimens. RESULTS: Comparison of the approximated MSU masses in the porcine foreleg scans with the true MSU masses of the syringe contents showed similar performance to sole volume measurement while providing additional information on the true uric acid burden: Over 70% of the true urate masses have been detected in MSU concentrations ≥ 45%, while the detection rate was much lower for MSU concentrations ≤ 40%. Retrospective analysis of patients with proven gouty arthritis confirmed the diagnostic potential of the mass approximation technique. CONCLUSIONS: We successfully established a method to include tophus density measurement for estimation of the uric acid burden in milligrams (instead of ml) in a phantom setting for MSU concentrations above 40%. Future studies should validate its use for follow-up in clinical practice. KEY POINTS: • Including tophus density measurement in dual-energy computed tomography scans in a phantom setting can be used for estimating the urate burden in milligrams, which might be useful for imaging follow-up. • The mass [mg] of the uric acid burden in a patient with gouty arthritis can be calculated by multiplying volume [ml] with mean density [HU] using a specific gravimetric coefficient. • Retrospective analysis of two patients with gouty tophi showed the relevance of measuring urate mass in addition to urate volume alone.


Assuntos
Artrite Gotosa/diagnóstico por imagem , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Ácido Úrico/análise , Algoritmos , Animais , Artrite Gotosa/metabolismo , Humanos , Masculino , Imagens de Fantasmas , Estudos Retrospectivos , Suínos
8.
Radiol Med ; 124(12): 1281-1295, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31792703

RESUMO

The physical principles of dual-energy computed tomography (DECT) are as old as computed tomography (CT) itself. To understand the strengths and the limits of this technology, a brief overview of theoretical basis of DECT will be provided. Specific attention will be focused on the interaction of X-rays with matter, on the principles of attenuation of X-rays in CT toward the intrinsic limits of conventional CT, on the material decomposition algorithms (two- and three-basis-material decomposition algorithms) and on effective Rho-Z methods. The progresses in material decomposition algorithms, in computational power of computers and in CT hardware, lead to the development of different technological solutions for DECT in clinical practice. The clinical applications of DECT are briefly reviewed in relation to the specific algorithms.


Assuntos
Algoritmos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tecnologia Radiológica/métodos , Tomografia Computadorizada por Raios X/métodos , Feminino , Humanos , Masculino , Espalhamento de Radiação , Raios X
9.
Radiol Med ; 124(12): 1238-1252, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31630332

RESUMO

Cardiovascular computer tomography (CT) in pediatric congenital heart disease (CHD) patients is often challenging. This might be due to limited patient cooperation, the high heart rate, the complexity and variety of diseases and the need for radiation dose minimization. The recent developments in CT technology with the introduction of the third-generation dual-source (DS) dual-energy (DE) CT scanners well suited to respond to these challenges. DSCT is characterized by high-pitch, long anatomic coverage and a more flexible electrocardiogram-synchronized scan. DE provides additional clinical information about vascular structures, myocardial and lung perfusion and allows artifacts reduction. These advances have increased clinical indications and modified CT protocol for pediatric CHD patients. In our hospital, DSCT with DE technology has rapidly become an important imaging technique for both pre- and postoperative management of pediatric patients with CHDs. The aim of this article is to describe the state-of-the-art in DSCT protocol with DE technology in pediatric CHD patients, providing some case examples of our experience over an 18-month period.


Assuntos
Cardiopatias Congênitas/diagnóstico por imagem , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Artefatos , Criança , Pré-Escolar , Meios de Contraste/administração & dosagem , Filtração/instrumentação , Frequência Cardíaca , Humanos , Lactente , Recém-Nascido , Movimentos dos Órgãos , Doses de Radiação , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/instrumentação , Respiração , Tomografia Computadorizada por Raios X/instrumentação
10.
Eur J Radiol ; 120: 108698, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31600640

RESUMO

PURPOSE: The aim of the study is to explore the patient's and scan's parameters that affect the iodine concentration in the abdomen using dual energy computed tomography (DECT) in an oncologic population. METHOD: This is a retrospective study with consecutive patients with different cancers who underwent a single-source DECT (ssDECT) examinations at our institution between years 2015 and 2017. On axial IODINE images, the radiologist manually drew a circular ROI along the inner contour of the aorta. Mean iodine concentration and ROI areas were recorded. Body mass index for every patient was recorded. Descriptive statistics were summarized for iodine concentration and patient/scan characteristics. Linear regression was used to examine associations between iodine concentration in aorta and studied characteristics. Statistical significance was set at a p value < 0.05. RESULTS: The univariate analysis, showed a statistically significant association between iodine concentration within the aorta and the area of ROI (Estimated Coefficient ß: -0.013), the rate of injection (Estimated Coefficient ß: 2.09), the acquisition time (Estimated Coefficient ß: -0.195). In multivariable analysis iodine concentration in the aorta increased with higher rate of injection (4 ml/sec), smaller ROI area and lower BMI. CONCLUSION: Our results showed how iodine concentration is highly dependent on some intrinsic and extrinsic parameters of the examination. These parameters should be taken into account since lower concentration of iodine decrease contrast-to-noise ratio, and in longitudinal follow up studies, they would affect iodine quantitive assessments in cancer patients with frequent chemotherapy-induced variations in BMI and cardiac function.


Assuntos
Meios de Contraste/farmacocinética , Iodo/farmacocinética , Neoplasias/diagnóstico por imagem , Intensificação de Imagem Radiográfica/métodos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Adulto , Aorta/metabolismo , Índice de Massa Corporal , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
11.
Br J Radiol ; 92(1104): 20190530, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31559858

RESUMO

OBJECTIVES: To estimate the minimum detectable iodine concentration on multiple dual-energy CT (DECT) platforms. METHODS AND MATERIALS: A phantom containing iodine concentrations ranging from 0 to 10 mg ml-1 was scanned with five dual-energy platforms (two rapid kilo volt switching (r-kVs), one dual source (DS), one sequential acquisition and one split-filter). Serial dilutions of 300 mg ml-1 iodinated contrast material were used to generate concentrations below 2 mg ml-1. Iodine density and virtual monoenergetic images were reviewed by three radiologists to determine the minimum visually detectable iodine concentration. Contrast-to-noise ratios (CNRs) were calculated. RESULTS: 1 mg mL-1 (~0.8 mg mL-1 corrected) was the minimum visually detectable concentration among the platforms and could be seen by all readers on the third-generation r-kVs and DS platforms. CONCLUSIONS: At low concentrations, CNR for monoenergetic images was highest on the DS platform and lowest in the sequential acquisition and split-filter platforms. ADVANCES IN KNOWLEDGE: The results of this study corroborate previous in vivo estimates of iodine detection limits at DECT and provide a comparison for the performance of different DECT platforms at low iodine concentrations in vitro.


Assuntos
Meios de Contraste/química , Iodo/análise , Imagens de Fantasmas , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Biomarcadores/análise
12.
BMC Med Imaging ; 19(1): 64, 2019 08 09.
Artigo em Inglês | MEDLINE | ID: mdl-31399078

RESUMO

BACKGROUND: Our aim was to compare CT images from native, nephrographic and excretory phases using image quality criteria as well as the detection of positive pathological findings in CT Urography, to explore if the radiation burden to the younger group of patients or patients with negative outcomes can be reduced. METHODS: This is a retrospective study of 40 patients who underwent a CT Urography examination on a 192-slice dual source scanner. Image quality was assessed for four specific renal image criteria from the European guidelines, together with pathological assessment in three categories: renal, other abdominal, and incidental findings without clinical significance. Each phase was assessed individually by three radiologists with varying experience using a graded scale. Certainty scores were derived based on the graded assessments. Statistical analysis was performed using visual grading regression (VGR). The limit for significance was set at p = 0.05. RESULTS: For visual reproduction of the renal parenchyma and renal arteries, the image quality was judged better for the nephrogram phase (p < 0.001), whereas renal pelvis/calyces and proximal ureters were better reproduced in the excretory phase compared to the native phase (p < 0.001). Similarly, significantly higher certainty scores were obtained in the nephrogram phase for renal parenchyma and renal arteries, but in the excretory phase for renal pelvis/calyxes and proximal ureters. Assessment of pathology in the three categories showed no statistically significant differences between the three phases. Certainty scores for assessment of pathology, however, showed a significantly higher certainty for renal pathology when comparing the native phase to nephrogram and excretory phase and a significantly higher score for nephrographic phase but only for incidental findings. CONCLUSION: Visualisation of renal anatomy was as expected with each post-contrast phase showing favourable scores compared to the native phase. No statistically significant differences in the assessment of pathology were found between the three phases. The low-dose CT (LDCT) seems to be sufficient in differentiating between normal and pathological examinations. To reduce the radiation burden in certain patient groups, the LDCT could be considered a suitable alternative as a first line imaging method. However, radiologists should be aware of its limitations.


Assuntos
Rim/diagnóstico por imagem , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Artéria Renal/diagnóstico por imagem , Urografia/instrumentação , Adulto , Idoso , Meios de Contraste , Feminino , Humanos , Rim/irrigação sanguínea , Masculino , Pessoa de Meia-Idade , Tecido Parenquimatoso/diagnóstico por imagem , Doses de Radiação , Interpretação de Imagem Radiográfica Assistida por Computador/instrumentação , Estudos Retrospectivos , Tomografia Computadorizada por Raios X/instrumentação
13.
Br J Radiol ; 92(1103): 20180734, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31430185

RESUMO

OBJECTIVE: The purpose of our study was to evaluate the visibility of the hilar lymph nodes (LNs) using advanced virtual monoenergetic low-keV images compared with early-phase contrast-enhanced CT. METHODS: Dual energy contrast-enhanced CT was performed for pre-operative evaluation of lung cancer at 20 and 60 s after administration of contrast media in 50 patients (32 males and 18 females; mean age, 69 years). Five kinds of images (A: 20 s/120 kV; B: 60 s/40 keV; C: 60 s/50 keV; D: 60 s/120 kV; E: 60 s/100 kV) were reconstructed. We measured the CT number of the bilateral main pulmonary arteries (PAs), pulmonary veins (PVs) and hilar LNs, and evaluated the differences in CT number (Hounsfield units, HUs) between the PA/PV and LNs (PA-LN and PV-LN contrast). Artifacts from the superior vena cava (SVC) were also evaluated. RESULTS: The mean PA-LN contrast (HU) was 415 in image group A, 299 in B, 180 in C, 80 in D, and 100 in E. The mean PV-LN contrasts in each group were 306, 287, 177, 78, and 99, respectively. Image group B showed the second highest PA-LN contrast following image group A. There was no significant difference in the PV-LN contrast between image groups A and B. The PA-LN and PV-LN contrasts of image groups B and C were significantly higher than those of E. SVC artifacts were lower in the delayed-phase images (Group B-E) than in Group A. CONCLUSION: To evaluate the hilar LNs with a single image series, advanced virtual monoenergetic 40-keV imaging at the delayed 60-s phase seems to be the most valuable. ADVANCES IN KNOWLEDGE: Advanced virtual monoenergetic image is useful for evaluation of both hilar LNs and tumors in the delayed phase without artifact derived from the streak artifact from dense contrast media in the SVC.


Assuntos
Neoplasias Pulmonares/diagnóstico por imagem , Linfonodos/efeitos dos fármacos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Viabilidade , Feminino , Humanos , Metástase Linfática , Masculino , Pessoa de Meia-Idade , Tomografia Computadorizada Multidetectores/métodos , Cuidados Pré-Operatórios/métodos , Interpretação de Imagem Radiográfica Assistida por Computador , Estudos Retrospectivos
14.
J Appl Clin Med Phys ; 20(8): 171-179, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31423728

RESUMO

Multiphase computed tomography (CT) exams are a commonly used imaging technique for the diagnosis of renal lesions and involve the acquisition of a true unenhanced (TUE) series followed by one or more postcontrast series. The difference in CT number of the mass in pre- and postcontrast images is used to quantify enhancement, which is an important criterion used for diagnosis. This study sought to assess the feasibility of replacing TUE images with virtual unenhanced (VUE) images derived from Dual-Energy CT datasets in renal CT exams. Eliminating TUE image acquisition could reduce patient dose and improve clinical efficiency. A rapid kVp-switching CT scanner was used to assess enhancement accuracy when using VUE compared to TUE images as the baseline for enhancement calculations across a wide range of clinical scenarios simulated in a phantom study. Three phantoms were constructed to simulate small, medium, and large patients, each with varying lesion size and location. Nonenhancing cystic lesions were simulated using distilled water. Intermediate (10-20 HU [Hounsfield units]) and positively enhancing masses (≥20 HU) were simulated by filling the spherical inserts in each phantom with varied levels of iodinated contrast mixed with a blood surrogate. The results were analyzed using Bayesian hierarchical models. Posterior probabilities were used to classify enhancement measured using VUE compared to TUE images as significantly less, not significantly different, or significantly higher. Enhancement measured using TUE images was considered the ground truth in this study. For simulation of nonenhancing renal lesions, enhancement values were not significantly different when using VUE versus TUE images, with posterior probabilities ranging from 0.23-0.56 across all phantom sizes and an associated specificity of 100%. However, for simulation of intermediate and positively enhancing lesions significant differences were observed, with posterior probabilities < 0.05, indicating significantly lower measured enhancement when using VUE versus TUE images. Positively enhancing masses were categorized accurately, with a sensitivity of 91.2%, when using VUE images as the baseline. For all scenarios where iodine was present, VUE-based enhancement measurements classified lesions with a sensitivity of 43.2%, a specificity of 100%, and an accuracy of 78.1%. Enhancement calculated using VUE images proved to be feasible for classifying nonenhancing and highly enhancing lesions. However, differences in measured enhancement for simulation of intermediately enhancing lesions demonstrated that replacement of TUE with VUE images may not be advisable for renal CT exams.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Imagens de Fantasmas , Intensificação de Imagem Radiográfica/métodos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/instrumentação , Tomografia Computadorizada por Raios X/métodos , Algoritmos , Teorema de Bayes , Meios de Contraste , Humanos , Doses de Radiação
15.
J Comput Assist Tomogr ; 43(5): 770-774, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31425308

RESUMO

BACKGROUND: Follow-up with computed tomographic angiography is recommended after endovascular aneurysm repair, exposing patients to significant levels of radiation and iodine contrast medium. Dual-energy computed tomography allows virtual noncontrast (VNC) images to be reconstructed from contrast-enhanced images using a software algorithm. If the VNC images are a good-enough approximation of true noncontrast (TNC) images, a reduction in radiation dose can be ensured through omitting a TNC scan. PURPOSE: To compare image quality of VNC images reconstructed from arterial phase and venous phase dual-energy computed tomographic angiography to TNC images and to assess which one is more suitable to replace TNC images. METHODS: Sixty-three consecutive patients were examined using a dual-energy computed tomography as elective follow-up after endovascular aneurysm repair. The examination protocol included 1 unenhanced and 2 contrast-enhanced scans (80 kV/Sn140 kV) of the aorta. Virtual noncontrast data sets were reconstructed from the arterial (A-VNC) and venous (V-VNC) phase scans, respectively. Mean attenuation and image noise were measured for TNC, A-VNC, and V-VNC images within regions of interest at 2 levels in the aorta, the liver, retroperitoneal fat, and psoas muscle. Subjective image quality was assessed on a 4-point scale by 2 blinded readers. RESULTS: The differences between A-VNC and TNC, and between A-VNC and V-VNC, were substantial aorta at the level of diaphragm and aorta at the level of renal arteries. The difference between V-VNC and TNC was, on the other hand, very small and not statistically significant for the renal artery aorta. For liver, fat, and muscle tissue, there were significant differences between both A-VNC and V-VNC compared with TNC, but findings were similar between A-VNC and V-VNC. CONCLUSIONS: Virtual noncontrast images based on venous-phase scans appear to be a more accurate representation of TNC scans than VNC images based on arterial-phase scans.


Assuntos
Aneurisma Aórtico/diagnóstico por imagem , Angiografia por Tomografia Computadorizada/métodos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Idoso , Algoritmos , Aneurisma Aórtico/cirurgia , Meios de Contraste , Procedimentos Endovasculares , Feminino , Humanos , Iohexol , Masculino , Estudos Prospectivos , Interpretação de Imagem Radiográfica Assistida por Computador
16.
J Appl Clin Med Phys ; 20(9): 104-113, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31390137

RESUMO

PURPOSE: Virtual monoenergetic images (VMIs) derived from dual-energy computed tomography (DECT) have been explored for several clinical applications in recent years. However, VMIs at low and high keVs have high levels of noise. The aim of this study was to reduce image noise in VMIs by using a two-step noise reduction technique. METHODS: VMI was first denoised using a modified highly constrained backprojection (HYPR) method. After the first-step denoising, a general-threshold filtering method was performed. Two sets of anthropomorphic phantoms were scanned with a clinical dual-source DECT system. DECT data (80/140Sn kV) were reconstructed as VMI series at 12 different energy levels (range, 40-150 keV, interval, 10 keV). For comparison, the averaged VMIs obtained from 10 repeated DECT scans were used as the reference standard. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and root-mean-square error (RMSE) were used to evaluate the quality of VMIs. RESULTS: Compared to the original HYPR method, the proposed two-step image denoising method could provide better performance in terms of SNR, CNR, and RMSE. In addition, the proposed method could achieve effective noise reduction while preserving edges and small structures, especially for low-keV VMIs. CONCLUSION: The proposed two-step image denoising method is a feasible method for reducing noise in VMIs obtained from a clinical DECT scanner. The proposed method can also reduce edge blurring and the loss of intensity in small lesions.


Assuntos
Algoritmos , Encéfalo/diagnóstico por imagem , Imagens de Fantasmas , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Razão Sinal-Ruído , Tomografia Computadorizada por Raios X/métodos , Humanos
17.
Medicine (Baltimore) ; 98(33): e16606, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31415352

RESUMO

OBJECTIVE: The aim of this study was to determine optimal window settings for conventional polyenergetic and virtual monoenergetic images derived from computed tomography pulmonary angiogram (CTPA) examinations of a novel dual-layer spectral detector computed tomography system (DLCT). METHODS: Monoenergetic (40 keV) and polyenergetic images of 50 CTPA examinations were calculated and the best individual window width and level (W/L) values were manually assessed. Optimized values were obtained afterwards based on regression analysis. Diameters of standardized pulmonary artery segments and subjective image quality parameters were evaluated and compared. RESULTS: Attenuation and contrast-to-noise values were higher in monoenergetic than in polyenergetic images (P≤.001). Averaged best individual W/L for polyenergetic and monoenergetic were 1020/170 and 2070/480 HU, respectively.All adjusted W/L-settings varied significantly compared to standard settings (700/100 HU) and obtained higher subjective image quality scores. A systematic overestimation of artery diameters for standard window settings in monoenergetic images was observed. CONCLUSIONS: Appropriate W/L-settings are required to assess polyenergetic and monoenergetic CTPA images of a novel DLCT. W/L-settings of 1020/170 HU and 2070/480 HU were found to be the best averaged values for polyenergetic and monoenergetic CTPA images, respectively.


Assuntos
Angiografia por Tomografia Computadorizada/métodos , Processamento de Imagem Assistida por Computador/métodos , Pulmão/diagnóstico por imagem , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Humanos , Pneumologia/métodos , Razão Sinal-Ruído
18.
Eur Radiol ; 29(12): 6762-6771, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31264015

RESUMO

PURPOSE: To assess whether virtual non-contrast (VNC) images derived from contrast dual-layer dual-energy computed tomography (DL-DECT) images could replace true non-contrast (TNC) images for aortic intramural hematoma (IMH) diagnosis in acute aortic syndrome (AAS) imaging protocols by performing quantitative as well as qualitative phantom and clinical studies. MATERIALS AND METHODS: Patients with confirmed IMH were included retrospectively in two centers. For in vitro imaging, a custom-made phantom of IMH was placed in a semi-anthropomorphic thorax phantom (QRM GmbH) and imaged on a DL-DECT at 120 kVp under various conditions of patient size, radiation exposure, and reconstruction modes. For in vivo imaging, 21 patients (70 ± 13 years) who underwent AAS imaging protocols at 120 kVp were included. In both studies, contrast-to-noise ratio (CNR) between hematoma and lumen was compared using a paired t test. Diagnostic confidence (1 = non-diagnostic, 4 = exemplary) for VNC and TNC images was rated by two radiologists and compared. Effective radiation doses for each acquisition were calculated. RESULTS: In both the phantom and clinical studies, we observed that the CNRs were similar between the VNC and TNC images. Moreover, both methods allowed differentiating the hyper-attenuation within the hematoma from the blood. Finally, we obtained equivalent high diagnostic confidence with both VNC and TNC images (VNC = 3.2 ± 0.7, TNC = 3.1 ± 0.7; p = 0.3). Finally, by suppressing TNC acquisition and using VNC, the mean effective dose reduction would be 40%. CONCLUSION: DL-DECT offers similar performances with VNC and TNC images for IMH diagnosis without compromise in diagnostic image quality. KEY POINTS: • Dual-layer dual-energy CT enables virtual non-contrast imaging from a contrast-enhanced acquisition. • Virtual non-contrast imaging with dual-layer dual-energy CT reduces the number of acquisitions and radiation exposure in acute aortic syndrome imaging protocol. • Dual-layer dual-energy CT has the potential to become a suitable imaging tool for acute aortic syndrome.


Assuntos
Doenças da Aorta/diagnóstico por imagem , Hematoma/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Idoso , Algoritmos , Feminino , Humanos , Técnicas In Vitro , Masculino , Pessoa de Meia-Idade , Imagens de Fantasmas , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Reprodutibilidade dos Testes , Estudos Retrospectivos , Sensibilidade e Especificidade
19.
Jpn J Radiol ; 37(9): 660-665, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31338722

RESUMO

PURPOSE: To evaluate the opacity of DC beads® (DCB) loaded with mineral ions on low-keV monochromatic images from dual energy computed tomography (DECT) and T1-weighted gradient-echo (T1-GRE) MRI. MATERIALS AND METHODS: Fe2+ or Ca2+-loaded DCBs were prepared by mixing DCBs in 100 mM FeSO4 or CaSO4 solution and scanned by DECT from 10 min to 27 h after mixing. The Hounsfield units (HUs) of sedimented DCBs on 40-keV monochromatic images were measured. Next, we mixed DCBs in 100, 10, 5 and 1 mM FeSO4 solutions, and scanned these solutions from 15 to 120 min after mixing using a 3 T MR scanner. The signal-noise ratios (SNRs) of sedimented DCBs on T1-GRE were measured. Venous blood was scanned to compare with DCBs. RESULTS: The CT values of DCBs in FeSO4 and CaCl2 solutions gradually increased, and were 113.3 and 43.1 HU at 27 h, respectively; that of blood was 17.8 HU. The SNR of DCB in 1 mM FeSO4 solution increased and achieved equilibrium at 120 min, and was 120.5 and higher than in the other FeSO4 solutions. The SNR of blood was 49.7. CONCLUSION: Optimally Fe2+-loaded DCBs can be discriminated from venous blood on 40-keV monochromatic images from DECT and T1-GRE.


Assuntos
Sulfato de Cobre , Compostos Ferrosos , Imagem por Ressonância Magnética/métodos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Íons , Minerais
20.
Diagn Interv Radiol ; 25(4): 257-264, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31213426

RESUMO

PURPOSE: We aimed to assess the utility of dual-energy computed tomography (DECT) imaging in diagnosing acute appendicitis (AA) with density measurements of the appendix vermiformis. METHODS: A total of 210 consecutive patients presenting with acute abdominal pain were scanned using DECT between January and October 2016. Twenty-six patients had pathologically confirmed AA, while 30 had normal appendices. Appendiceal densities were measured in the true axial section of the appendix vermiformis at 80 kVp, 140 kVp, virtual noncontrast, iodine overlay, mixed, and monoenergetic (40, 50, 60, 70, 80, 90, 100 keV) images. RESULTS: Comparison of the appendix at different kVp and keV energy levels, virtual noncontrast, iodine overlay, and mixed images yielded significant differences between patients with appendicitis and those with a normal appendix (P < 0.001 for all). Receiver operating characteristic (ROC) curve analysis revealed that the 80 kVp image set yielded the best diagnostic performance among all image sets (area under the ROC curve [AUC], 0.996; P < 0.001), while 70 keV images yielded the highest diagnostic performance among the virtual monoenergetic image sets (AUC, 0.958; P < 0.001). Inter-rater agreement was good at 80 kVp images (intraclass correlation coefficient [ICC], 0.78, P < 0.001). CONCLUSION: Evaluation of DECT image reconstructions suggested that low tube voltage with 80 kVp demonstrated accurate diagnostic performance for AA. This finding suggests that low kVp CT may be useful for diagnosing AA with reduced patient radiation exposure.


Assuntos
Apendicite/diagnóstico por imagem , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Doença Aguda , Adulto , Idoso , Apendicite/patologia , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Doses de Radiação , Exposição à Radiação/prevenção & controle , Interpretação de Imagem Radiográfica Assistida por Computador/métodos
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