The invention relates to a leaf module (1) for a multi-leaf collimator, comprising a leaf unit (2) and a leaf drive unit (3), wherein the leaf unit (2) comprises a leaf (4) for shielding beams from a selected area, the leaf unit (2) is mounted displaceably in an adjusting direction (5) with relation to the leaf drive unit (3), wherein the leaf drive unit (3) is designed to displace the leaf unit (2) linearly in the adjusting direction (5), and the leaf drive unit (3) comprises at least one drive mechanism (9) which operates based on piezoelectric actuation, being designed in such a way that the leaf drive unit (3) thoroughly encloses the leaf unit (2) within a plane being oriented substantially perpendicularly related to the adjusting direction (5). Furthermore, the invention relates to a multi-leaf collimator comprising a plurality of leaf modules (1) according to the invention. The invention facilitates a design of leaf modules (1) with a shape being as compact as possible, and wherein both precise and stable adjustability of the leaf unit (2) is achieved. In this way improvements to multi-leaf collimators are provided likewise.
