Abstract
The relationship of the detectability to the size and depth in water of a cold lesion and the total image counts (information density) of scintigram were assessed by means of the averaged receiver operating characteristic (ROC) curves. As a result, the detectability of a cold lesion depends on the total image counts required to compose a scintigram and the dot size of a micro-dot imager. The more the total image counts and the smaller the dot size, the better the detectability of the cold lesionis. The contrast between the cold lesion (signal) and the background (noise) is improved by effective utilization of the film characteristic curve. A cold lesion of 1.5 cm in diameter can not be detected at a depth of 3 cm, even if the most suitable condition is chosen. However, a cold lesion of 2.3 cm in diameter can be detected perfectly. Similarly, a cold lesion of 9 cm in depth is almost imppossible to detect no matter what the size used in this study. It seems that the depth with meaningful information can be obtained is up to 5 cm. As the total image counts of a scintigram increases, the detectability of a cold lesion increases.
