Motion Artifacts in Subsecond Conventional CT and Electron-Beam CT: Pictorial Demonstration of Temporal Resolution

Abstract

To visually demonstrate the effective temporal resolution of subsecond conventional (slip-ring) and electron-beam computed tomographic (CT) systems, two phantoms containing high-contrast test objects were scanned with a slip-ring CT system (effective exposure time, 0.5 second) and an electron-beam CT system (exposure time, 0.1 second). Images were acquired of each phantom at rest, during translation along the x axis at speeds of 10-100 mm/sec, and during rotation about isocenter at speeds of 0.1 and 0.5 revolution per second. Motion artifacts and loss of spatial resolution were judged to be absent, noticeable, or severe. For 0.5-second conventional CT images, motion artifacts and loss of spatial resolution were noticeable at 10 mm/sec and 0.1 revolution per second and were severe at speeds greater than or equal to 20 mm/sec and at 0.5 revolution per second. For 0.1-second electron-beam CT scans, noticeable, but not severe, motion artifacts and loss of spatial resolution occurred at speeds between 40 and 100 mm/sec and at 0.5 revolution per second. Over the range of physiologic speeds examined, the images provide visually compelling evidence of the effect of improving temporal resolution in CT.

Study on motion artifacts in coronary arteries with an anthropomorphic moving heart phantom on an ECG-gated multidetector computed tomography unit

“…A decrease in image quality is usually correlated to the synchronization of the rotation time and the movement of the heart. Because a synchronization effect is not playing Table 3 Comparison by heart rate (HR) in beats per minute of the blind ranking of the coronary arteries of the moving heart phantom in three independent series by two independent readers (R1 and R2) from good (8) Sum the sum of the ranking, ave average, stdev standard deviation in the sum, rank ranking of the average a role at this heart rate (1,091 ms/500 ms=2.18) an explanation may be that the movement of the heart phantom shows very different behavior at 55 bpm compared with at the other heart rates, for which the movement is more or less smooth and predictable. The occurrence of resonances in the heart movement may cause a high-amplitude movement of the coronary arteries, causing severe artifacts in the reconstructed images.…”

“…The use of a phantom mimicking the movement of the heart and the coronary arteries can be useful to study the image quality in a systematic way. Several studies demonstrating the influence of motion on the image quality have been performed with a phantom [6][7][8][9]. To our knowledge only in one study an anthropomorphic heart phantom was used [10].…”

Characterization of Human Renal Stones with MDCT: Advantage of Dual Energy and Limitations Due to Respiratory Motion

“…McCollough et al [27], Alfidi et al [28], and Ritchie et al [29] have proved that physiologic motion decreases the quality of CT images. To our knowledge, no studies have been conducted to evaluate the influence of residual respiratory motion on the…”

MDCT artifact related to the intra-scan gravitational flow of opacified luminal fluid (the “Dense Waterfall” sign)

“…The degree of the artifact on the reconstructed image is dependent upon the distance travelled by the object, in this case enteric contrast, during the image acquisition [5]. The further the object moves during image acquisition, or the slower the gantry rotation relative to the speed of the fluid motion, the more pronounced the artifact [6]. We have since noticed this artifact on routine CT examinations related to the intra-scan motion of opacified fluid within an otherwise unopacified lumen (Fig.…”