Contrast resolution in multidetector-row CT with 16 detector rows: phantom study

Abstract

This study was performed for evaluation of high- and low-contrast resolution in multidetector-row CT (MDCT) with 16 detector rows. For evaluating high-contrast resolution, a phantom was scanned ten times at 100 mA s with 24 patterns of scan parameters under several X-ray beam widths, X-ray tube voltages, X-ray tube rotation times, and helical pitches. Three radiological technologists observed the images visually. For evaluating low-contrast resolution, a phantom was scanned ten times at 100 mA s with the 24 patterns of scan parameters, which were the same as for high-contrast resolution. The images were examined based on receiver operating characteristic (ROC) curves. The high-contrast resolution deteriorated in the off-center locations when helical pitches of 1.375:1 or 1.75:1 were used. High helical pitch (>0.9375:1) and low tube voltage had significant effects on the low-contrast resolution. However, a wide X-ray beam width and short X-ray tube rotation time had no definite influence. Therefore, a helical pitch of 0.5625:1 should be used when the contrast resolutions are really important, and a wide X-ray beam width and short X-ray tube rotation time can improve the temporal resolution without deterioration of contrast resolution.

Contrast-to-noise ratio difference in small field of view cone beam computed tomography machines

“…An important aspect of image quality in CBCT other than spatial resolution is contrast resolution. Contrast resolution is referred to as the ability of an imaging modality to distinguish between various contrast levels in an acquired image (19). In general, a lesion-tobackground contrast is related to the contrast-to-noise ratio (CNR), and CNR has been considered to be more closely related to image quality than image noise (20).…”