Image assessment and post-processing with multislice CT angiography in highly calcified coronary arteries

Abstract

In response to the article by Cordeiro et al., CT angiography in highly calcified arteries: 2D vs. modified automated 3D approach to identify coronary stenoses (DOI 100.1007/s10554-005-9044-9) Since the introduction of the first generation of computed tomography (CT) in 1972, the technique has undergone many technological innovations. In 1998, mechanical spiral CT with simultaneous acquisition by 4-detector rows has been introduced as a noninvasive imaging modality for direct visualization of the coronary arteries. The reported sensitivities for the detection of significant stenoses with the 4-slice multislice computed tomography (MSCT) systems ranged from 67 to 91%, while the specificities ranged from 75 to 99%, and the negative predictive values were particularly high, reaching up to 97% [1][2][3][4][5][6]. Inadequate image quality mainly due to cardiac and respiratory motion artifacts and severe calcifications, however, resulted in the exclusion of 22% of all coronary segments, which was a major limitation of the technique [7]. Sixteen-slice MSCT scanners with higher temporal and spatial resolution showed better results. The sensitivities ranged between 70 and 98%, whereas the specificities varied between 93 and 98%, with only 4% of coronary segments being excluded as not evaluable [7]. With the introduction of 64-slice MSCT systems, further substantial improvement in image quality is anticipated. The new generation scanners allow gantry rotation time of 330 ms and provide nearly isotropic voxels of 0.4 mm [8]. Leschka et al. [9] performed MSCT in comparison to invasive coronary angiography in 67 patients. All coronary segments were included in the analysis.The authors reported a sensitivity of 94% and a specificity of 97% to detect significant coronary stenoses. Mollet et al.[10] evaluated the performance of 64-slice MSCT in 52 patients. Again, all available coronary segments were included in the evaluation; the sensitivity and specificity for detecting significant coronary stenoses on a segment-persegment basis showed promising results and were 99% and 95%, respectively.Several image post-processing techniques are available to allow clinically useful information to be extracted from several hundreds of individual axial images generated during single MSCT examination of the coronary arteries [8,11]. The evaluation often begins with the scrolling through axial images, which are considered to be the source images for image post-processing. Multiplanar reconstructions (MPRs) are generated from the volume data set reconstructed from axial images in several arbitrary imaging planes. MPRs can be easily and quickly performed on any dedicated workstation, with all available data being represented in the images. Curved MPR (cMPR) enables the entire coronary artery to be displayed in one reconstruction. Two or more images in orthogonal planes are examined to render correct evaluation of coronary lesions. Depending on the vascular tissue densities encountered by each ray in the three-dimensional volume, maximum inte...

Comparação das dimensões das artérias coronárias e da composição da placa aterosclerótica entre a angiografia coronária por tomografia de 64 colunas de detectores e a ultrassonografia intracoronária com a técnica de histologia virtual

“…A inclusão de vários segmentos relativamente sadios (pequena carga de placa) pode ser responsável por este achado, uma vez que, o erro entre as medidas de área da luz em nosso estudo foi menor, em regiões com maior carga de placa. A influência do grau de calcificação coronária sobre as medidas de dimensões vasculares, em tomógrafos de 16 colunas de detectores, já havia sido avaliada em modelos experimentais (ex vivo e in vitro)(37,44,48), porém estudos mais recentes, com tomógrafos de 64 colunas de detectores, sugerem que este parâmetro poderia não ter tanta influência sobre as medidas de dimensões vasculares quanto previamente observado em tomógrafos de 16 colunas de detectores(38).Foi também interesse deste estudo avaliar a influência de parâmetros relacionados à qualidade da imagem radiológica sobre a caracterização da placa aterosclerótica à tomografia. Para este fim, restringimo-nos à analise de fatores relacionados ao grau de contrastação da luz arterial.…”