Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
1.
Eur J Radiol ; 20(3): 179-84, 1995 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-8536744

RESUMO

The introduction of new devices demands the assessment of their capabilities in established terms. The accuracy, reproducibility and spatial resolution of in vitro (phantom) osteodensitometric and morphometric measurements of QDR 2000 Plus and EXPERT are presented. Design details of these DXA/MXA-devices are listed and discussed in combination with the data acquired in the test measurements and calculations. The image quality will improve with further software developments. The long-term reproducibility and in vivo reliability remains to be evaluated.


Assuntos
Absorciometria de Fóton/instrumentação , Densidade Óssea , Osso e Ossos/anatomia & histologia , Absorciometria de Fóton/estatística & dados numéricos , Absorciometria de Fóton/tendências , Desenho de Equipamento , Fêmur/anatomia & histologia , Antebraço/anatomia & histologia , Humanos , Aumento da Imagem , Processamento de Imagem Assistida por Computador , Modelos Estruturais , Osteoporose/diagnóstico , Reprodutibilidade dos Testes , Software , Coluna Vertebral/anatomia & histologia
2.
Rofo ; 166(2): 140-5, 1997 Feb.
Artigo em Alemão | MEDLINE | ID: mdl-9116256

RESUMO

PURPOSE: The accuracy and reproducibility of morphometric measurements (Morphometric X-ray Absorptiometry = MXA) of vertebrae were determined. The significant difference of the change in height of vertebral bodies in follow-up studies was computed for MXA methods and digitised spinal radiographs as well. MATERIAL AND METHODS: The measurements were carried out on two new Dual X-ray Absorptiometry (DXA) devices (device A = Expert, Lunar Corp., device B = QDR 2000 Plus, Hologic Inc.). The data were obtained by using the European Spine Phantom (ESP) and lumbar spine specimens. RESULTS: The accuracy of vertebral morphometry performed on radiographs is 2.0%, on the device A 2.3%, and on the device B 4.9%. Measurements taken with the ESP showed a reproducibility of 1.0 to 3.0%, whereas measurements of fractured vertebrae resulted in 5.1 to 6.0%. CONCLUSION: The results of the morphometric measurements demonstrate that a reliable fracture analysis in phantoms and specimens is possible. Further in-vivo studies are necessary.


Assuntos
Absorciometria de Fóton/instrumentação , Coluna Vertebral/diagnóstico por imagem , Absorciometria de Fóton/métodos , Absorciometria de Fóton/estatística & dados numéricos , Humanos , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/lesões , Imagens de Fantasmas , Intensificação de Imagem Radiográfica/instrumentação , Intensificação de Imagem Radiográfica/métodos , Reprodutibilidade dos Testes , Software , Fraturas da Coluna Vertebral/diagnóstico por imagem
3.
Rofo ; 175(9): 1264-71, 2003 Sep.
Artigo em Alemão | MEDLINE | ID: mdl-12964084

RESUMO

The use of the CT scanner for cardiac imaging is mainly influenced by the spatial and temporal resolution that can be achieved with the applied technologies and procedures. The data acquisition with 16 x 0.5 mm scan slice thickness and a special multisegment image reconstruction procedure are a new combination for accurate imaging of the cardiac morphology. A 0.5 mm slice thickness and an overlapping pitch < 0.35 generate an isotropic image voxel of 0.35 x 0.35 x 0.35 mm. The object size of a coronary artery with a diameter of 2.5 mm amounts to a relative spatial blurring factor K (d) of approximately 15 %. The segment reconstruction with 4 segments from 4 consecutive cardiac cycles requires the optimum acquisition time of 50 ms for one frame. The relative exposure factor K (t) with reference to the R-R interval is an appropriate measure to validate the influence of coronary artery movement on the image quality at different heart rates. This relative exposure varies between 10 % and 20 % for a heart rate of 40 to 140 beats per minutes (bpm) and its mean is approximated by a linear trend function with K (t) = 14 %. A constant value in this linear trend function means a constant "blurring" of the imaged coronary arteries, independent of the actual heart rate. Thus, computed tomographic examinations can be carried out for heart rates between 40 and 140 bpm without using beta-blocking medication. Case studies of the 3D reconstruction and curved reformatting of coronary arteries with stents and calcifications show the achievable image quality at different heart rates.


Assuntos
Coração/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Algoritmos , Angiografia Coronária , Coração/anatomia & histologia , Frequência Cardíaca , Humanos , Imageamento Tridimensional , Modelos Teóricos , Imagens de Fantasmas , Fatores de Tempo
4.
Rofo ; 175(6): 780-5, 2003 Jun.
Artigo em Alemão | MEDLINE | ID: mdl-12811690

RESUMO

PURPOSE: To evaluate the potential of multisegmental reconstruction and variable gantry rotation time for reducing motion-induced artifacts in coronary artery imaging by multislice helical CT. MATERIALS AND METHODS: The data sets of 20 patients (8 with HR < 60 bpm, 12 with HR > 60 bpm) were analyzed. The patients underwent multislice helical CT (Aquilion 8, Toshiba, Otawara, Japan) using the following parameters: 0.5 mm slice thickness, 250 mA, 120 kV, pitch of 0.25 and variable gantry rotation times of 400, 500, or 600 msec. Images were generated by halfscan and multisegmental reconstruction. In 9 coronary segments of each patient, the presence and severity of motion artifacts were assessed and graded on a scale between 5 (no artifacts) and 1 (heaviest artifacts). RESULTS: Diagnostically relevant motion artifacts were rare at low heart rates (< 60 bpm) for both types of image reconstruction (4 % of all segments). Higher heart rates (> 60 bpm) were associated with an increase in motion artifacts on halfscan reconstructions (33% of all segments, p < 0.05) but not on multisegmental reconstructions (4% of all segments). At low heart rates mean image quality did not differ between multisegmental and halfscan reconstruction (4.28 +/- 0.37 vs. 4.22 +/- 0.41; p > 0.05), whereas at higher heart rates image quality was better for multisegmental reconstruction than for halfscan reconstruction (4.23 +/- 0.47 vs. 3.11 +/- 0.63; p < 0.05). CONCLUSION: Multisegmental reconstruction with variable gantry rotation times suppresses motion artifacts and thus improves assessment of the coronary arteries in patients with higher heart rates.


Assuntos
Angiografia Coronária/métodos , Doença das Coronárias/diagnóstico por imagem , Processamento de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Tomografia Computadorizada Espiral/métodos , Artefatos , Eletrocardiografia , Frequência Cardíaca , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Sensibilidade e Especificidade , Software
5.
Br J Radiol ; 82(979): 561-70, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19221186

RESUMO

The aim of this study was to report initial clinical experience with a 320-slice CT scanner and to perform an image quality evaluation. 26 patients with presumptive cerebrovascular pathology underwent 320-slice CT. Single-rotation CT of the head, incremental CT angiography (three-dimensional (3D) CTA) as well as four-dimensional whole-brain CTA (4D CTA) and whole-brain CT perfusion (CTP) were performed and the resulting images were assessed for quality and compared with those obtained with 64-slice CT protocols. 320-slice CT neuroimaging could be performed in all cases. The image quality of 320-slice CT of the head and 3D CTA was inferior to that of the 64-slice protocols. The image quality of 4D 320-slice CTA was rated as inferior to both 320- and 64-slice 3D CTA. 4D CTA-CTP imaging added information with pivotal clinical implications. 320-slice CT neuroimaging is feasible technique that permits whole-brain 4D imaging and has the potential to identify pathologies with altered haemodynamics. However, image quality is a limitation of this technique at present.


Assuntos
Transtornos Cerebrovasculares/diagnóstico por imagem , Tomografia Computadorizada de Feixe Cônico/normas , Tomógrafos Computadorizados/normas , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Artefatos , Angiografia Cerebral/métodos , Angiografia Cerebral/normas , Circulação Cerebrovascular , Estudos de Viabilidade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
7.
Acta Radiol ; 45(8): 819-27, 2004 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-15690611

RESUMO

PURPOSE: To evaluate multi-slice spiral computed tomography (MSCT) for measurements of left ventricular volumes, ejection fraction (EF), and myocardial mass in comparison with electron beam CT (EBCT) as a reference method. MATERIAL AND METHODS: Six minipigs underwent both standardized contrast-enhanced MSCT (effective acquisition time per cardiac cycle 125.7+/-30.1 ms, reconstructed slice thickness 8 mm) and EBCT (acquisition time 50 ms, collimated slice thickness 8 mm). The contrast-to-noise ratio of the left ventricle was measured in each animal, and the contour sharpness of the myocardium was analyzed. Volumes (EDV, ESV, SV) ejection fraction (EF), and muscle mass were calculated by MSCT and by EBCT using the slice summation method. RESULTS: MSCT had a higher contrast-to-noise ratio and delineated the myocardial contours more sharply than EBCT. There was a close linear correlation between both modalities for all parameters (EDV: rP=0.88, ESV: rP=0.91, SV: rP=0.85, EF: rP=0.93; mass: rP=0.90; P<0.05 each). MSCT slightly overestimated ESV and slightly underestimated SV and EF compared with EBCT (P<0.05 each). CONCLUSIONS: Image quality in MSCT is superior to that of EBCT. Functional parameters correlate well between both modalities, but the accuracy of MSCT is limited by its lower temporal resolution.


Assuntos
Ventrículos do Coração/anatomia & histologia , Ventrículos do Coração/diagnóstico por imagem , Volume Sistólico , Tomografia Computadorizada Espiral , Função Ventricular Esquerda , Animais , Modelos Animais , Suínos , Porco Miniatura , Tomografia Computadorizada por Raios X
8.
Br J Orthod ; 14(4): 329, 1987 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-3481285
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA