Utility of 256-slice cone beam tomography for real four-dimensional volumetric analysis without electrocardiogram gated acquisition

Purpose Current ECG-gated multislice CT can reveal any cardiac phase data, including four-dimensional (4D) images, but cannot acquire the whole heart in one scanning, and arrhythmias impair the quality of the images. We used a prototype 256-slice cone beam CT (Athena, Sony Toshiba), with which the whole heart can be acquired in one scanning. Materials and methods A pulsating device with contrast material (300 mgI/dl) diluted 10× with saline was moved at 5, 40, 60, 70, and 90 to-and-fro movements/min. Non-ECG-gated 256-slice cone beam CT with 256 × 0.5 mm slice thickness was performed during one to-and-fro motion at each rate. After acquisition, each to-and-fro motion was divided into 20 frames, and each volume was measured and volumetric curves were constructed. Results Even without ECG-gated acquisition, the configuration of the pulsating device at any rate continued to the through plane without any gaps, and the 4D movie of the pulsating device could be observed at any rate except 60 movements/min. Volumes of end-diastole (ED) and end-systole (ES), and ejection fraction (EF) at static state were 81.7, 17.5 ml, and 79% respectively. ED volumes were 81.7, 81.7, 70.3, 63.7, 68.3 and 65.9 ml, ES volumes were 17.5, 30.9, 39.8, 62.7, 55.0 and 43.2 ml, and EF was 79, 62, 43, 2, 19 and 34% at 0, 5, 40, 60, 70, and 90 to-and-fro movements/min, respectively. The ratios of ED volume, using the static state as the reference, were 100, 86, 78, 84 and 81%, those of ES volume were 177, 227, 358, 314 and 247%, and those of EF were 78, 54, 3, 24 and 43% at 5, 40, 60, 70, and 90 to-and-fro movements/min, respectively. From the configuration of volumetric curves, only 5/min could be evaluated. At 60 movements/min, the same device images without any motion were observed in 4D images during one to-and-fro motion. This may be because one to-and-fro time and one scanning time were the same (1 s). Conclusion Even without ECG-gated acquisition, this new 256-slice cone beam CT achieved real 4D analysis of the pulsating device. The ED volume and the configuration of volumetric curve could only be evaluated up to 5 movements/min, but because of poor spatial resolution (1 s/rotation), even at 5 movements/min ES volume tended to be overestimated. As a result, EF tended to be underestimated, which may be improved in the next generation (0.5 s/rotation).