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Artigo em Inglês | MEDLINE | ID: mdl-31755031


A computed tomography (CT) image is generally reconstructed by a filtered back projection (FBP) algorithm. In an FBP algorithm, the image quality primarily depends on a reconstruction filter kernel. Although the details of the filter kernel are not disclosed to users, the frequency response of the filter kernel can theoretically be calculated using the relational formula of the filter kernel and the modulation transfer function (MTF) of the reconstruction algorithm (MTFA). In this study, we proposed a method to determine the frequency response of a filter kernel and verify its validity. Two clinical CT scanners were used to derive the filter kernel. The MTF was obtained and subsequently separated to the MTF of the scanner system and MTFA. Using the relational formula of the filter kernel and MTFA, we calculated the frequency response of the filter kernel. To verify the calculated result, we measured the noise power spectrum (NPS). Additionally, the filter kernel was calculated using the relational formula of the filter kernel and NPS. In both CT scanners, the filter kernels calculated by the two methods showed good agreement, and we confirmed the validity of the results and the effectiveness of the proposed method. Furthermore, the inherent image quality performance of the CT scanner could be clarified by the reconstruction filter kernel.

Medicine (Baltimore) ; 98(45): e17940, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31702683


Venous air embolism (VAE) can be observed in the right heart system on contrast-enhanced computed tomography (CT), following injection of contrast media with a power injector system. Although most VAEs are mostly asymptomatic, they may result in paradoxical air embolism (PAE).To evaluate whether the incidence of VAE on coronary CT angiography is associated with the process of preparation of the intravenous access route.We retrospectively evaluated 692 coronary CT examinations at 3 institutions. Trained CT nurses placed an intravenous cannula in the forearm. Tubes connected to the cannula were prepared in the following ways: A, using an interposed three-way cock and a 20-mL syringe filled with normal saline to collect air contamination in the tube; B, through direct connection to the power injector system without the interposed 3-way cock; and C, using an interposed three-way cock and a 100-mL normal saline drip infusion bottle system to keep the tube patent. The incidence and location of VAE and preparation of intravenous injection were assessed.The overall incidence of VAE was 55.3% (383/692), most frequently observed in the right atrium (81.5%, 312/383). Its incidence varied significantly across the 3 techniques (A: 21.6% (35/162), B: 63.2% (237/375) and C: 71.6% (111/155); P < .001). No patient demonstrated any symptom associated with VAE.Using a 3-way cock with syringe demonstrated the lowest incidence of VAE on coronary CT angiography. It is thus recommended to reduce potential complication risks related to intravenous contrast media injection.

Angiografia por Tomografia Computadorizada/efeitos adversos , Embolia Aérea/etiologia , Embolia Paradoxal/etiologia , Átrios do Coração/diagnóstico por imagem , Idoso , Meios de Contraste/administração & dosagem , Embolia Aérea/complicações , Embolia Aérea/epidemiologia , Embolia Paradoxal/epidemiologia , Humanos , Injeções Intravenosas/efeitos adversos , Injeções Intravenosas/instrumentação , Injeções Intravenosas/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
Radiol Case Rep ; 14(6): 687-691, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30976369


We report a case of asymptomatic iatrogenic air bubbles in the left ventricle observed by coronary computed tomographic angiography. Air bubbles are rarely found in the left ventricle and could prove fatal should they migrate to the brain or coronary arteries. We believe that the cause is micro air bubbles in the tubing system between the intravenous catheter and power injector.

Artigo em Japonês | MEDLINE | ID: mdl-30890672


Dual-energy computed tomography (DE-CT) is the promising technology, such as enabling material decomposition, generation of the virtual monochromatic image, and measurement of effective atomic numbers. There are reports that utilization of the virtual non-contrast (VNC) image, the iodine map image, and the virtual monochromatic image can contribute to the improvement of lesion detection and its characterization, compared with conventional contrast CT by single-energy computed tomography (SE-CT). In addition, acquisition of the VNC images makes it possible to skip scanning of true non-contrast CT, which is also expected to reduce exposure. However, a reliable evaluation of the accuracy of the VNC image has not been established, and only a few reports have verified their accuracy. In this study, we evaluated the relationship between the quantitativeness of iodine and the CT value of VNC image. As a result of our study, when the iodine volume was overestimated, the CT value of the VNC image was lower than the reference value, and when the iodine volume was underestimated, the CT value was upper than the reference value. Moreover, we clarified that the CT value of the VNC image greatly diverges as the iodine volume increases.

Iodo , Imagem Radiográfica a Partir de Emissão de Duplo Fóton , Tomografia Computadorizada por Raios X , Meios de Contraste
Nihon Hoshasen Gijutsu Gakkai Zasshi ; 69(11): 1225-31, 2013 Nov.
Artigo em Japonês | MEDLINE | ID: mdl-24256645


Coil-embolized cerebral aneurysms are difficult to evaluate using computed tomography (CT) angiography (CTA) due to artifacts caused by the coil devices. This study was conducted to assess the practicality of energy subtraction processing using monochromatic images obtained using CTA after coil embolization of a cerebral aneurysm. In this study, the changes in the CT value of the contrast agent and the coil were analyzed not only at varying monochromatic energy levels but also by energy subtraction processing. Our analyses revealed an exponential change in the CT value of the contrast agent at any desired energy. We also found that the CT value of the coil was unchanged at the upper threshold of the grayscale limit. Based on these results, we were able to create images of changes in material-specific CT values and thus eliminate the material. Energy subtraction processing enabled us to distinguish between the contrast agent, the coil, and the artifacts from coil devices. We suggest that energy subtraction processing using monochromatic images can resolve the limitations of CTA after coil embolization of cerebral aneurysms.

Angiografia/métodos , Embolização Terapêutica/métodos , Processamento de Imagem Assistida por Computador/métodos , Aneurisma Intracraniano/terapia , Técnica de Subtração , Tomografia Computadorizada por Raios X/métodos , Artefatos , Humanos , Imagens de Fantasmas