A lesion phantom is disclosed, which is a spherical ball having a cavity formed therein for housing contrast agents or medicines, and is enabled for the quantitative evaluation of a medical image in drug development and evaluation. In an embodiment, the cavity of the lesion phantom is coupled to a tapering ring and is configured to be sealed by a silicon plug, in order to ensure that contrast agents or medicines can be fed into the cavity easily and conveniently without causing any problem, such as overflowing, a bubble residue problem, radioactive contamination, etc. Moreover, by the arrangement of a retractable fixing bar, the positioning of the lesion phantom can be adjusted flexibly at will, and additionally by the tapering of the tapering ring, the lesion phantom can be prevented from being damaged by any extreme, sudden, unjust, or improper force exerted, and thus the lifespan of the lesion phantom can be prolonged.
