A method of planning an image-guided needle insertion procedure in a region of interest of a subject, comprising: (a) obtaining a plurality of time-separated images of the region of interest, said plurality of time-separated images derived at different times during breathing motion of said subject; (b) defining on a first image of said plurality of time-separated images an entry point (11, 21), a target point (13, 23) and one or more regions into which entry by said needle insertion procedure is forbidden (12, 22); (c) calculating on said first image a first trajectory for said needle insertion procedure between said entry point (11, 21) and said target point (13, 23), which avoids entry into all of said one or more forbidden regions (12, 22); (d) selecting a second image of said plurality of time-separated images; (e) determining the position of said entry point (11, 21), said target point (13, 23) and said one or more regions into which entry by said needle insertion procedure is forbidden (12, 22) in said second image of said plurality of time-separated images; (f) calculating, on at least said second image, a new trajectory between said entry point (11, 21) and said target point (13, 23), which avoids entry into all of said one or more forbidden regions (12, 22); (g) checking one or more of: (i) the proximity of said first and said new calculated trajectories to any of said one or more regions into which entry by said needle insertion procedure is forbidden (12, 22), and (ii) the curvature of said first and said new calculated trajectories, to determine if at least one preselected level relating to said one or more of said proximity and said curvature is exceeded. (a) obtaining a plurality of time-separated images of the region of interest, said plurality of time-separated images derived at different times during breathing motion of said subject; (b) defining on a first image of said plurality of time-separated images an entry point (11, 21), a target point (13, 23) and one or more regions into which entry by said needle insertion procedure is forbidden (12, 22); (c) calculating on said first image a first trajectory for said needle insertion procedure between said entry point (11, 21) and said target point (13, 23), which avoids entry into all of said one or more forbidden regions (12, 22); (d) selecting a second image of said plurality of time-separated images; (e) determining the position of said entry point (11, 21), said target point (13, 23) and said one or more regions into which entry by said needle insertion procedure is forbidden (12, 22) in said second image of said plurality of time-separated images; (f) calculating, on at least said second image, a new trajectory between said entry point (11, 21) and said target point (13, 23), which avoids entry into all of said one or more forbidden regions (12, 22); (g) checking one or more of: (i) the proximity of said first and said new calculated trajectories to any of said one or more regions into which entry by said needle insertion procedure is forbidden (12, 22), and (ii) the curvature of said first and said new calculated trajectories, to determine if at least one preselected level relating to said one or more of said proximity and said curvature is exceeded. (i) the proximity of said first and said new calculated trajectories to any of said one or more regions into which entry by said needle insertion procedure is forbidden (12, 22), and (ii) the curvature of said first and said new calculated trajectories, to determine if at least one preselected level relating to said one or more of said proximity and said curvature is exceeded.