A positron emission local tomography method, comprising: acquiring projection data indicative of positron annihilations occurring in an object in a positron emission examination of the object; identifying a local region of interest of an object, wherein the object encompasses the local region of interest; spatially truncating the projection data, wherein the spatially truncating includes identifying projection data acquired along lines of response that intersect the identified local region of interest; iteratively reconstructing the spatially truncated projection data to produce first image space data indicative of the object; wherein the iteratively reconstructing includes forward projecting an image estimate to produce image estimate projection data for a plurality of lines of response yielding ∑ n ′ H mn ′ f ^ n ′ k; comparing image estimate projection data for lines of response that intersect the local region of interest and the spatially truncated projection data yielding g ̃ m ∑ n ′ H mn ′ f ^ n ′ k; backprojecting the compared projections yielding ∑ m ∈ ε s 0 φ H mn g ̃ m ∑ n ′ H mn ′ f ^ n ′ k; using the backprojected compared projections to update the image estimate, wherein the forward projecting, comparing, backprojecting and updating yields an update of an image element of the form: f ^ n k + 1 = f ^ n k ∑ m ∈ ε s 0 φ H mn ∑ m ∈ ε s 0 φ H mn g ̃ m ∑ n ′ H mn ′ f ^ n ′ k, wherein f ^ n k + 1 indicates an image element for an object element indicated by an index n of the updated image estimate, f ^ n k indicates an image element for the object element indicated by the index n of the image estimate to be updated, g̃ m indicates a projection data value of the truncated projection data detected at a detector element m, H mn indicates a system matrix representing a probability of a photon emitted from an object element n to be detected at a detector element m and ε { s 0 ( φ)} indicates the identified local region of interest, wherein the forward projection is performed on all object elements n '. acquiring projection data indicative of positron annihilations occurring in an object in a positron emission examination of the object; identifying a local region of interest of an object, wherein the object encompasses the local region of interest; spatially truncating the projection data, wherein the spatially truncating includes identifying projection data acquired along lines of response that intersect the identified local region of interest; iteratively reconstructing the spatially truncated projection data to produce first image space data indicative of the object; wherein the iteratively reconstructing includes forward projecting an image estimate to produce image estimate projection data for a plurality of lines of response yielding ∑ n ′ H mn ′ f ^ n ′ k; comparing image estimate projection data for lines of response that intersect the local region of interest and the spatially truncated projection data yielding g ̃ m ∑ n ′ H mn ′ f ^ n ′ k; backprojecting the compared projections yielding ∑ m ∈ ε s 0 φ H mn g ̃ m ∑ n ′ H mn ′ f ^ n ′ k; using the backprojected compared projections to update the image estimate, wherein the forward projecting, comparing, backprojecting and updating yields an update of an image element of the form: f ^ n k + 1 = f ^ n k ∑ m ∈ ε s 0 φ H mn ∑ m ∈ ε s 0 φ H mn g ̃ m ∑ n ′ H mn ′ f ^ n ′ k, wherein f ^ n k + 1 indicates an image element for an object element indicated by an index n of the updated image estimate, f ^ n k indicates an image element for the object element indicated by the index n of the image estimate to be updated, g̃ m indicates a projection data value of the truncated projection data detected at a detector element m, H mn indicates a system matrix representing a probability of a photon emitted from an object element n to be detected at a detector element m and ε { s 0 ( φ)} indicates the identified local region of interest, wherein the forward projection is performed on all object elements n '.