The invention is related to an apparatus and method for charged hadron therapy verification by detecting and/or quantifying prompt gammas produced when irradiating a target (6) with a charged hadron beam. The apparatus comprises a collimator (1) provided with a slit-shaped portion (2) configured to be arranged perpendicularly to the beam line and facing the target, a detection means (3,4) suitable for detecting said prompt gammas and a calculation and representation means. In the apparatus and method of the invention, the slit is configured to allow the passage of prompt gammas emitted from a range of depths in said target (6), said depths being measured in the direction of the charged hadron beam. Furthermore, said detection means is configured to detect prompt gammas emitted from each location within said range, and said calculation and representation means is configured to derive from a detected prompt gamma a value representative of the dose at the location from where said prompt gamma is emitted, and to represent a dose-related distribution for a plurality of locations within said range.
