Investigation of the performance characteristics of 16-slice and 64-slice multi-detector computed tomography in coronary angiogram : an image quality study

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Investigation of the performance characteristics of 16-slice and 64-slice multi-detector computed tomography in coronary angiogram : an image quality study

 

Author: Chung, Yee-kwan Elaine
Title: Investigation of the performance characteristics of 16-slice and 64-slice multi-detector computed tomography in coronary angiogram : an image quality study
Degree: M.Sc.
Year: 2009
Subject: Hong Kong Polytechnic University -- Dissertations.
Coronary arteries -- Radiography.
Heart -- Tomography.
Radiography, Medical -- Image quality.
Department: Dept. of Health Technology and Informatics
Pages: xii, 157 leaves : col. ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2302274
URI: http://theses.lib.polyu.edu.hk/handle/200/5048
Abstract: The increase in spatial and temporal resolution with 64-slice MDCT has rendered better image quality of CT coronary angiograms, but incurs 40% more radiation dose compared with 16-slice MDCT. Both scanners have been used in local clinical workplace for coronary angiogram. Previous studies suggested that 16-slice CT had similar diagnostic accuracy as 64-slice CT regarding to coronary heart disease but yet studies of image quality as an essential factor to accurate diagnosis are needed to elucidate their clinical roles. The purposes of the study are to compare the efficacy of the imaging methods using standardized qualitative and quantitative image evaluation, and taking into consideration of both patients and radiographers which are prime factors in a CT examination. CT coronary angiogram of 80 patients were collected retrospectively with 40 patients examined with 16-slice CT while the other 40 patients examined with 64-slice CT. Totally 320 coronary arteries were evaluated. Overall, the 64 -slice CT coronary angiograms being significantly better subjective image quality than the 16-slice CT coronary angiograms were evaluated by two independent radiographers. Both MDCT showed similar trends in order of subjective image quality evaluation: left main artery (LMA) was excellent; left circumflex artery (LCX) was between excellent and good; left anterior descending artery (LAD) and right coronary artery (RCA) were between good and moderate. There were 16.9% coronary arteries with poor image quality by using 16-slice MDCT, while only 1.8% coronary arteries with poor image quality by using 64-slice MDCT. Moreover, the inter-radiographer agreements of image quality of coronary arteries at both MDCT coronary images were high. Results of quantitative parameters showed that the overall vessel length visualized of LAD and LCX; the ratio of visualized length of LAD and RCA free of motion artifacts and CT attenuation of aortic root were significantly different using 64-slice MDCT as compared with 16-slice MDCT. Apart from the factors of CT scanners and radiographers, patient anthropometric parameters: heart rate, degree of arterial calcium and body mass index (BMI) will influence in image quality of CT coronary angiograms. Simple effects analyses revealed that patients with high heart rate (>65bpm) had higher ratio of visualized length of LCX and RCA free of motion artifacts using 64-slice CT than using 16-slice CT. However, there was no significant interaction effect between calcium score vs. CT machines and BMI vs. CT machines on the quantitative measurements. Optimal image quality between 60% and 75% R-R intervals reconstruction was judged best for image reconstruction for 89% patients. In summary, both 16-slice and 64-slice CT coronary angiograms rendered images qualified well enough for diagnosis in terms of both qualitative and quantitative evaluations. However, offering much lower radiation dose, 16-slice MDCT is proved persevering its clinical values with similar diagnostic accuracy as 64-slice MDCT. Moreover, patients' heart rate is found the only prime factor in the image quality of both MDCT. And, the best image quality was found in patients having low heart rate (<65bpm) with single-segment algorithm reconstruction. Therefore, it is advisable to lower the patients' heart rate before undergoing both MDCT coronary angiographies, especially in 16-slice CT. To further reduce radiation of 64-slice CT coronary angiography without degradation of image quality, ECG-control tube modulation using 60-75% reconstruction windows should be enabled for patients with stable heart rates. Lastly, the high inter-radiographer agreement implied that the reliable and consistent evaluation of CT images by radiographers is crucial to the diagnosis. This substantiates the role development of the radiographers.

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