RESUMEN
UNSCEAR concluded that increased use of CT scanning caused dramatic changes in population dose. Therefore, international radiation protection authorities demand: 1) periodical quality assurance tests with respect to image quality and radiation dose, and 2) optimization of all examination protocols with respect to image quality and radiation dose. This study aimed to evaluate and analyze multiple image quality parameters and variability measured throughout time for six different CT scanners from four different vendors, in order to evaluate the current methodology for QA controls of CT systems. The results from this study indicate that there is minor drifting in the image noise and uniformity and in the spatial resolution over time for CT scanners, independent of vendors. The HU for different object densities vary between different CT scanner models from different vendors, and over time for one specific CT scanner. Future tests of interphantom and intraphantom variations, along with inclusion of more CT scanners, are necessary to establish robust baselines and recommendations of methodology for QA controls of CT systems, independent of model and vendor.
Asunto(s)
Procesamiento de Imagen Asistido por Computador/métodos , Fantasmas de Imagen , Garantía de la Calidad de Atención de Salud/métodos , Tomógrafos Computarizados por Rayos X/clasificación , Tomografía Computarizada por Rayos X/instrumentación , Tomografía Computarizada por Rayos X/métodos , Algoritmos , Humanos , Garantía de la Calidad de Atención de Salud/normas , Dosis de Radiación , Factores de Tiempo , Tomografía Computarizada por Rayos X/normasRESUMEN
BACKGROUND: The aim of this study was to evaluate the amount of radiation doses absorbed by soft tissues (entrance skin dose) with a low-dose spiral computed tomography (CT) protocol compared to conventional X-ray techniques commonly used in orthodontics. METHODS: The amount of skin dose has been evaluated using a tissue-equivalent head-neck radiotherapy humanoid phantom with thermoluminescent dosimeters placed at the level of eye lens, parotid glands, and thyroid glands. CT images have been taken using a Sensation 16 Siemens CT scan and a low-dose protocol (15 mAs, 1 pitch, 2.5 mGy (CTDIvol), 80 kV, 1-mm slice thickness). RESULTS: The difference in image quality between traditional X-ray techniques and low-dose spiral CT was statistically significant (P<0.05). The difference in mean absorbed dose instead was not statistically significant. CONCLUSIONS: Our protocol allows a more accurate orthodontic diagnosis without an increase of radiological risk for the patients in comparison to traditional X-ray techniques.
Asunto(s)
Ortodoncia Correctiva , Dosis de Radiación , Radiografía Dental/métodos , Piel/efectos de la radiación , Tomografía Computarizada Espiral/métodos , Puntos Anatómicos de Referencia/diagnóstico por imagen , Cefalometría/métodos , Mentón/diagnóstico por imagen , Humanos , Cristalino/efectos de la radiación , Mandíbula/diagnóstico por imagen , Cóndilo Mandibular/diagnóstico por imagen , Maxilar/diagnóstico por imagen , Hueso Nasal/diagnóstico por imagen , Cavidad Nasal/diagnóstico por imagen , Glándula Parótida/efectos de la radiación , Fantasmas de Imagen , Intensificación de Imagen Radiográfica/métodos , Radiografía Panorámica/métodos , Silla Turca/diagnóstico por imagen , Dosimetría Termoluminiscente/instrumentación , Glándula Tiroides/efectos de la radiación , Tomógrafos Computarizados por Rayos X/clasificación , Cigoma/diagnóstico por imagenRESUMEN
PURPOSE: To assess the differences between the target delineation using computed tomography (CT) and imaging fusion CT/magnetic resonance imaging (MRI) for the radiotherapy planning of glioblastoma. METHODS: One hundred-twenty gross tumor volume and clinical target volume on CT and MRI (GTVCT/CTVCT, GTVMRI/CTVMRI, respectively) were contoured and evaluated. The treatments planning (total dose 60 Gy) based on CTVCT were analysed in terms of percentage of CTVCT and CTVMRI receiving 95 % of the prescribed dose (V95-CTVCT, V95-CTVMRI). RESULTS: GTVs and CTVs contoured on MRI were significantly larger than those delineated on CT (p = 0.0003, p = 0.0006, respectively). Nighty-two percent of CTVCT was coincident with the CTVMRI and 8 % was normal tissue; 20 % of CTVMRI, considered as tumor volume, was not included on CTVCT. The V95-CTVMRI was significantly lower than the V95-CTVCT (p = 0.0005). CONCLUSIONS: In the delineation of glioblastoma target volume, fusion CT/MRI was preferred. The CT only is insufficient for the CTV dose coverage (AU)
Asunto(s)
Humanos , Masculino , Femenino , Glioblastoma/inducido químicamente , Glioblastoma/metabolismo , Glioblastoma/radioterapia , Glioblastoma/clasificación , Glioblastoma/diagnóstico , Tomógrafos Computarizados por Rayos X/clasificación , Espectroscopía de Resonancia MagnéticaRESUMEN
The aims of this study were to compare measurements on three-dimensional (3D) models of human skulls derived from two different cone beam CT scanners (CBCT) and to evaluate if the used hardware can influence the performed measurements. CBCT scans of 40 dry human skulls with both the i-CAT and the Iluma cone beam CT scanners were made. From the CBCT scans, 3D models were constructed. One operator identified 19 landmarks five times on both types of 3D models with a time interval of 1 week. Intra-observer reliability was high for most measurements. There was a statistically significant and clinically relevant difference for some measurements between constructed 3D models of the same skull from the two different CBCT devices. Used hardware for scanning might influence the measurements performed. This means that care should be taken when interpreting measurements made on CBCT 3D models derived from different CBCT devices.
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Cefalometría/métodos , Tomografía Computarizada de Haz Cónico/instrumentación , Imagenología Tridimensional/métodos , Modelos Anatómicos , Cráneo/diagnóstico por imagen , Tomógrafos Computarizados por Rayos X/clasificación , Puntos Anatómicos de Referencia/anatomía & histología , Puntos Anatómicos de Referencia/diagnóstico por imagen , Cefalometría/normas , Mentón/anatomía & histología , Mentón/diagnóstico por imagen , Tomografía Computarizada de Haz Cónico/métodos , Oclusión Dental , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Procesamiento de Imagen Asistido por Computador/normas , Incisivo/anatomía & histología , Incisivo/diagnóstico por imagen , Mandíbula/anatomía & histología , Mandíbula/diagnóstico por imagen , Cóndilo Mandibular/anatomía & histología , Cóndilo Mandibular/diagnóstico por imagen , Maxilar/anatomía & histología , Maxilar/diagnóstico por imagen , Diente Molar/anatomía & histología , Diente Molar/diagnóstico por imagen , Hueso Nasal/anatomía & histología , Hueso Nasal/diagnóstico por imagen , Variaciones Dependientes del Observador , Órbita/anatomía & histología , Órbita/diagnóstico por imagen , Paladar Duro/anatomía & histología , Paladar Duro/diagnóstico por imagen , Reproducibilidad de los Resultados , Silla Turca/anatomía & histología , Silla Turca/diagnóstico por imagen , Cráneo/anatomía & histología , Hueso Esfenoides/anatomía & histología , Hueso Esfenoides/diagnóstico por imagen , Hueso Temporal/anatomía & histología , Hueso Temporal/diagnóstico por imagenRESUMEN
BACKGROUND: Today, practically all computed tomography (CT) systems are delivered with automatic exposure control (AEC) systems operating with tube current modulation in three dimensions. Each of these systems has different specifications and operates somewhat differently. PURPOSE: To evaluate AEC systems from four different CT scanner manufacturers: General Electric (GE), Philips, Siemens, and Toshiba, considering their potential for reducing radiation exposure to the patient while maintaining adequate image quality. MATERIAL AND METHODS: The dynamics (adaptation along the longitudinal axis) of tube current modulation of each AEC system were investigated by scanning an anthropomorphic chest phantom using both 16- and 64-slice CT scanners from each manufacturer with the AEC systems activated and inactivated. The radiation dose was estimated using the parameters in the DICOM image information and image quality was evaluated based on image noise (standard deviation of CT numbers) calculated in 0.5 cm(2) circular regions of interest situated throughout the spine region of the chest phantom. RESULTS: We found that tube current modulation dynamics were similar among the different AEC systems, especially between GE and Toshiba systems and between Philips and Siemens systems. Furthermore, the magnitude of the reduction in the exposure dose was considerable, in the range of 35-60%. However, in general the image noise increased when the AEC systems were used, especially in regions where the tube current was greatly decreased, such as the lung region. However, the variation in image noise among images obtained along the scanning direction was lower when using the AEC systems compared with fixed mAs. CONCLUSION: The AEC systems available in modern CT scanners can contribute to a significant reduction in radiation exposure to the patient and the image noise becomes more uniform within any given scan.
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Dosis de Radiación , Protección Radiológica , Tomógrafos Computarizados por Rayos X , Seguridad de Productos para el Consumidor , Fantasmas de Imagen , Equipos de Seguridad/clasificación , Tomógrafos Computarizados por Rayos X/clasificación , Tomógrafos Computarizados por Rayos X/normas , Tomografía Computarizada por Rayos X/efectos adversosRESUMEN
PURPOSE: To investigate the diagnostic accuracy and limitations of 16-slice multidetector computed tomography (MDCT) in the detection of significant ( > 50%) stenosis of coronary artery bypass grafts (CABG) and native coronary arteries. MATERIALS AND METHODS: One hundred two patients with 236 grafts were investigated by 16-slice MDCT. Native coronary arteries were also investigated. The image quality was assessed in terms of artifact, and the evaluable segments were screened for the presence of occlusion and significant ( > 50%) stenosis. MDCT results were compared with conventional coronary angiography. RESULTS: The evaluability of MDCT was 90.4% for CABG and 71.2% for native coronary arteries. The most frequent causes of nonevaluable segments were motion artifact in venous grafts, metallic clip artifact in arterial grafts, and severe calcification in native coronary arteries. MDCT correctly diagnosed all of the 46 occluded grafts. The sensitivity, specificity, and the positive and negative predictive value of MDCT for the detection of significant CABG stenoses were 91.4%, 98.5%, 84.2%, and 99.2%, respectively. Including nonevaluable segments in the analysis, overall sensitivity was 84.2%. For the evaluation of native coronary arteries, MDCT had a sensitivity of 82.1% and a specificity of 75.3%, but evaluability was only 71.2%, resulting in overall sensitivity of 62.1%. CONCLUSION: Use of 16-slice MDCT angiography allows very accurate evaluation of CABG patency and has high diagnostic accuracy in detecting graft stenoses. But evaluation of native coronary artery stenosis is limited, particularly in patients with advanced coronary artery disease with severe calcification.
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Puente de Arteria Coronaria/normas , Estenosis Coronaria/diagnóstico por imagen , Oclusión de Injerto Vascular/diagnóstico por imagen , Tomógrafos Computarizados por Rayos X/normas , Tomografía Computarizada por Rayos X/normas , Adulto , Anciano , Algoritmos , Electrocardiografía , Femenino , Frecuencia Cardíaca , Humanos , Procesamiento de Imagen Asistido por Computador , Masculino , Persona de Mediana Edad , Sensibilidad y Especificidad , Tomógrafos Computarizados por Rayos X/clasificación , Tomografía Computarizada por Rayos X/clasificaciónRESUMEN
PURPOSE: To evaluate image quality of coronal reformations of chest performed on 64-row MDCT in comparison with 16-, 8- and 4-row MDCT. MATERIALS AND METHODS: Consecutive patients who underwent pulmonary CT angiography using four different MDCT scanners were retrospectively studied with IRB approval: (1) n=30, 64-row MDCT; (2) n=30, 16-row MDCT; (3) n=30, 8-row MDCT; (4) n=30, 4-row MDCT. Coronal reformatted images (2 mm thickness and 2mm intervals for 64-row MDCT; 5 mm thickness and 5 mm intervals for 16-, 8- and 4-row MDCT) were evaluated by consensus reading of two board-certified radiologists who were blinded to scanner type. The image quality of overall chest appearance and individual thoracic structures including heart, aorta and pulmonary arteries was graded using five-point scale. Grades from four different scanners were compared using Kruskal-Wallis test. A second evaluation was performed in 48 randomly selected patients (12 patients for each scanner). Reproducibility was assessed using weighted-kappa analysis. RESULT: Significant reproducibility was observed between the first and second evaluations in 48 patients both for image quality of overall chest (weighted kappa=0.826) and each thoracic structure (mean weighted kappa=0.803; range, 0.729-0.858). Image quality of overall chest and individual thoracic structures differed significantly among four different MDCT groups, with 64-row MDCT having the highest grades, followed by 16-, 8- and 4-row MDCT (mean grades for overall chest in each scanner: 3.9, 3.0, 2.4 and 1.9, respectively) (P<0.0001 for overall chest and each thoracic structure). CONCLUSION: When comparing coronal reformations of chest using four different MDCT scanners, the 64-row MDCT had the highest image quality for overall chest appearance and individual thoracic structures, followed by 16-, 8- and finally 4-row MDCT.
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Procesamiento de Imagen Asistido por Computador , Radiografía Torácica/instrumentación , Tomógrafos Computarizados por Rayos X/normas , Tomografía Computarizada por Rayos X/instrumentación , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Reproducibilidad de los Resultados , Estudios Retrospectivos , Tomógrafos Computarizados por Rayos X/clasificaciónRESUMEN
PURPOSE: To evaluate the accuracy of left ventricular volumetric and functional parameters from multi-slice computed tomography using automated analysis software, and to correlate results with those of invasive left ventriculography. MATERIALS AND METHODS: In 145 consecutive patients (mean age, 61 years+/-12) known or suspected to have coronary artery disease, a 16-channel multi-slice computed tomography (Philips Mx8000 IDT 16) was performed using a standard technique. Using short-axis secondary multi-slice computed tomography reformations, we determined end-diastolic and end-systolic left ventricular volumes and ejection fraction with a commercially available analysis software capable of automated contour detection. Conventional left ventriculography was performed according to standard techniques within the following 24 h. Bland-Altman analysis was performed to calculate the limits of agreement and systematic errors between multi-slice computed tomography and conventional left ventriculography. RESULTS: As determined by computer tomography, mean end-systolic (53+/-29 mL) left ventricular volumes had an acceptable correlation with conventional ventriculography (67+/-50 mL; r=0.74; p<0.001) and mean end-diastolic (119+/-33 mL) left ventricular volumes a poor correlation with conventional ventriculography measurements (154+/-69 mL; r=0.41). Left ventricular ejection fraction (57%+/-14 versus 55%+/-14 for conventional ventriculography; r=0.79) showed a very good correlation (p<0.001). Bland-Altman analysis showed acceptable limits of agreement (+/-9.2% for ejection fraction) without systematic errors. CONCLUSION: The use of a multi-slice computed tomography with an automatic calculation software has a good correlation with conventional ventriculography findings and could accurately assess left ventricular function, but should not be used for ventricular volumes, because of biased estimations.
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Enfermedad de la Arteria Coronaria/diagnóstico por imagen , Técnicas de Diagnóstico Cardiovascular/instrumentación , Intensificación de Imagen Radiográfica , Programas Informáticos , Tomógrafos Computarizados por Rayos X/normas , Función Ventricular Izquierda , Cinerradiografía/métodos , Medios de Contraste/administración & dosificación , Diagnóstico por Computador , Técnicas de Diagnóstico Cardiovascular/normas , Estudios de Factibilidad , Femenino , Ventrículos Cardíacos/diagnóstico por imagen , Humanos , Masculino , Persona de Mediana Edad , Tomógrafos Computarizados por Rayos X/clasificaciónAsunto(s)
Humanos , Femenino , Preescolar , Anemia , Tomógrafos Computarizados por Rayos X/clasificación , Tomógrafos Computarizados por Rayos X , Retinopatía de la Prematuridad/cirugía , Retinopatía de la Prematuridad/clasificación , Retinopatía de la Prematuridad/complicaciones , Retinopatía de la Prematuridad/diagnóstico , Angiografía , Angiografía CerebralRESUMEN
I hope that you will find the product matrix to be a useful tool for making comparisons between vendors and scanners. Please keep in mind that the vendors have directly provided the specific answers to the questions within the matrix. Neither the author nor Radiology Management shall be held responsible for any misrepresented or erroneous data.
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Tomógrafos Computarizados por Rayos X/clasificación , Catálogos Comerciales como Asunto , Recolección de Datos , Toma de Decisiones , Directorios como Asunto , Humanos , Departamento de Compras en Hospital , Tomógrafos Computarizados por Rayos X/economía , Tomografía Computarizada por Rayos X/instrumentación , Estados UnidosRESUMEN
Computed tomography (CT) scanners use x-rays to produce thin cross-sectional images, or slices, of human anatomy. Their applications include diagnosing head and body masses, assessing bone mineral content, displaying vasculature, and detecting and evaluating stenosis in blood vessels. Currently, three different CT scanning methods are available: (1) conventional CT; (2) spiral scanning, in which information is collected in a single continuous scan rather than in discrete slices; and (3) ultrafast CT, in which a rotating x-ray beam is produced without the movement of mechanical components. ECRI conducted this Evaluation at a hospital that had just taken delivery of a new GE Medical Systems HiSpeed Advantage CT scanner, a third-generation unit that can perform conventional or spiral scanning. This study, which was performed in conjunction with acceptance testing, provides the essential information required to ensure adequate system performance. The capabilities that we tested include tomographic slice geometry, radiation output, image quality, and human factors design. Readers are cautioned not to base purchasing decisions on our rating of this device alone, but on a thorough understanding of the issues surrounding CT scanners and the factors used to develop our conclusions, which can be acquired only by reading this study in its entirety. Reviewing the entire study will also help readers to gain the perspectives necessary to judge units other than the one we have evaluated.