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1.
Radiol Phys Technol ; 9(1): 69-76, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26404397

RESUMEN

The volume of the temporal horn of the lateral ventricle (THLV) on brain computed tomography (CT) images is important for neurologic diagnosis. Our purpose in this study was to develop a z-score-based semi-quantitative analysis for estimation of the THLV volume by using voxel-based morphometry. The THLV volume was estimated by use of a z-score mapping method that consisted of four main steps: anatomic standardization, construction of a normal reference database, calculation of the z score, and calculation of the mean z score in a volume of interest (VOI). A mean z score of the CT value obtained from a VOI around the THLV was used as an index for the THLV volume. CT scans from 50 subjects were evaluated. For evaluation of the accuracy of this method for estimating the THLV volume, the THLV volume was determined manually by neuroradiologists (serving as the reference volume). A mean z score was calculated from the VOI for each THLV of the 50 subjects by use of the proposed method. The accuracy of this method was evaluated by use of the relationship between the mean z score and the reference volume. The quadratic polynomial regression equation demonstrated a statistically significant correlation between the mean z score and the reference volume of the THLV (R (2) = 0.94; P < 0.0001). In 92 of 100 THLVs (92 %), the 95 % prediction interval of the regional mean z score captured the reference volume of the THLV. The z-score-based semi-quantitative analysis has the potential quantitatively to estimate the THLV volume on CT images.


Asunto(s)
Ventriculografía Cerebral , Ventrículos Laterales/anatomía & histología , Ventrículos Laterales/diagnóstico por imagen , Tomografía Computarizada por Rayos X , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Tamaño de los Órganos
2.
Radiol Phys Technol ; 7(1): 79-88, 2014 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-23996520

RESUMEN

The hyperdense middle cerebral artery (MCA) dot sign representing a thromboembolus is one of the important computed tomography (CT) findings for acute stroke on unenhanced CT images. Our purpose in this study was to develop an automated method for detection of the MCA dot sign of acute stroke on unenhanced CT images. The algorithm of the method which we developed consisted of 5 major steps: extraction of the sylvian fissure region, initial identification of MCA dots based on the morphologic top-hat transformation, feature extraction of candidates, elimination of false positives (FPs) by use of a rule-based scheme, and classification of candidates using a support vector machine (SVM) classifier with four features. Our database comprised 297 CT images obtained from seven patients with the MCA dot sign. The performance of this scheme for classification of the MCA dot sign was evaluated by means of a leave-one-case out method. The performance of the classification by use of the SVM achieved a maximum sensitivity of 97.5% (39/40) at a FP rate of 1.28 per image. The sensitivity for detection of the MCA dot sign was 97.5% (39/40) with a FP rate of 0.5 per hemisphere. The method we developed has the potential to detect the MCA dot sign of acute stroke on unenhanced CT images.


Asunto(s)
Arteria Cerebral Media/diagnóstico por imagen , Reconocimiento de Normas Patrones Automatizadas , Accidente Cerebrovascular/diagnóstico por imagen , Accidente Cerebrovascular/diagnóstico , Tomografía Computarizada por Rayos X , Anciano , Anciano de 80 o más Años , Algoritmos , Encéfalo/patología , Simulación por Computador , Diseño de Equipo , Reacciones Falso Positivas , Femenino , Humanos , Masculino , Variaciones Dependientes del Observador , Curva ROC , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Máquina de Vectores de Soporte , Tromboembolia/diagnóstico , Tromboembolia/diagnóstico por imagen
3.
Conf Proc IEEE Eng Med Biol Soc ; 2013: 3403-6, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-24110459

RESUMEN

The purpose of this study was to evaluate the performance of a conventional discrete wavelet transform (DWT) method and a modified undecimated discrete wavelet transform (M-UDWT) method applied to mammographic image denoising. Mutual information, mean square error, and signal to noise ratio were used as image quality measures of images processed by the two methods. We examined the performance of the two methods with visual perceptual evaluation. A two-tailed F test was used to measure statistical significance. The difference between the M-UDWT processed images and the conventional DWT-method processed images was statistically significant (P<0.01). The authors confirmed the superiority and effectiveness of the M-UDWT method. The results of this study suggest the M-UDWT method may provide better image quality as compared to the conventional DWT.


Asunto(s)
Artefactos , Mamografía/instrumentación , Análisis de Ondículas , Algoritmos , Simulación por Computador , Femenino , Humanos , Intensificación de Imagen Radiográfica , Relación Señal-Ruido
4.
Int J Biomed Imaging ; 2013: 797924, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-24382951

RESUMEN

We propose a method for improving image quality in medical images by using a wavelet-based approach. The proposed method integrates two components: image denoising and image enhancement. In the first component, a modified undecimated discrete wavelet transform is used to eliminate the noise. In the second component, a wavelet coefficient mapping function is applied to enhance the contrast of denoised images obtained from the first component. This methodology can be used not only as a means for improving visual quality of medical images but also as a preprocessing module for computer-aided detection/diagnosis systems to improve the performance of screening and detecting regions of interest in images. To confirm its superiority over existing state-of-the-art methods, the proposed method is experimentally evaluated via 30 mammograms and 20 chest radiographs. It is demonstrated that the proposed method can further improve the image quality of mammograms and chest radiographs, as compared to two other methods in the literature. These results reveal the effectiveness and superiority of the proposed method.

5.
J Digit Imaging ; 26(4): 748-58, 2013 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-23207923

RESUMEN

In this work, the authors present an effective denoising method to attempt reducing the noise in mammographic images. The method is based on using hierarchical correlation of the coefficients of discrete stationary wavelet transforms. The features of the proposed technique include iterative use of undecimated multi-directional wavelet transforms at adjacent scales. To validate the proposed method, computer simulations were conducted, followed by its applications to clinical mammograms. Mutual information originating from information theory was used as an evaluation measure for selection of an optimal wavelet basis function. We examined the performance of the proposed method by comparing it with the conventional undecimated discrete wavelet transform (UDWT) method in terms of processing time-consuming and image quality. Our results showed that with the use of the proposed method the computation time can be reduced to approximately 1/10 of the conventional UDWT method consumed. The results of visual assessment indicated that the images processed with the proposed UDWT method showed statistically significant superior image quality over those processed with the conventional UDWT method. Our research results demonstrate the superiority and effectiveness of the proposed approach.


Asunto(s)
Artefactos , Simulación por Computador , Procesamiento de Imagen Asistida por Computador/métodos , Mamografía/métodos , Análisis de Ondículas , Femenino , Humanos , Reproducibilidad de los Resultados
6.
J Digit Imaging ; 21(3): 338-47, 2008 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-17577596

RESUMEN

This paper presents a simple and straightforward method for synthetically evaluating digital radiographic images by a single parameter in terms of transmitted information (TI). The features of our proposed method are (1) simplicity of computation, (2) simplicity of experimentation, and (3) combined assessment of image noise and resolution (blur). Two acrylic step wedges with 0-1-2-3-4-5 and 0-2-4-6-8-10 mm in thickness were used as phantoms for experiments. In the present study, three experiments were conducted. First, to investigate the relation between the value of TI and image noise, various radiation doses by changing exposure time were employed. Second, we examined the relation between the value of TI and image blurring by shifting the phantoms away from the center of the X-ray beam area toward the cathode end when imaging was performed. Third, we analyzed the combined effect of deteriorated blur and noise on the images by employing three smoothing filters. Experimental results show that the amount of TI is closely related to both image noise and image blurring. The results demonstrate the usefulness of our method for evaluation of physical image quality in medical imaging.


Asunto(s)
Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Sistemas de Información Radiológica , Procesamiento de Señales Asistido por Computador , Algoritmos , Entropía , Humanos , Modelos Teóricos , Control de Calidad , Intensificación de Imagen Radiográfica/métodos , Sensibilidad y Especificidad
7.
Nihon Hoshasen Gijutsu Gakkai Zasshi ; 63(3): 341-4, 2007 Mar 20.
Artículo en Japonés | MEDLINE | ID: mdl-17409626

RESUMEN

Although radiographic image quality is considered difficult to evaluate in a straightforward and systematic manner, it may be possible by using an index of transmitted information. As a preliminary study, relations between transmitted information and two image characteristics, namely, image noise and image blurring, were evaluated by simulation. The value of transmitted information was decreased if image noise and image blurring increased. The relationships were corroborated on an experimental basis. This paper suggests the possibility of a simple, straightforward method for synthetically evaluating radiographic images by a single parameter in terms of transmitted information.


Asunto(s)
Simulación por Computador , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Radiografía , Procesamiento de Señales Asistido por Computador , Algoritmos , Entropía , Sensibilidad y Especificidad
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