A method, signal processor, device, and system for estimating a parametric or functional image 47 mapping a biological process on the basis of a limited or incomplete sequence of biological process images 40 recorded as a function of time, e.g. by a PET or SPECT scanner after injection of a radio tracer. One or more kinetic parameters 43 are first extracted by applying a pharmacokinetic model 42 (compartmental model of the underlying tracer kinetics) to the sequence of biological process images 40. Additional data 41 are used in the model, comprising at least a predetermined kinetic parameter range (e.g. from the literature), and optionally an input function or a blood clearance function. Next, an iterative algorithm 44 is applied to arrive at a modified sequence of images 45, e.g. by inserting an estimated image into the incomplete sequence of images, utilizing the one or more kinetic parameters 43. After a stop criterion has been fulfilled, the resulting image 47 is finally estimated 46 from the modified sequence of images 45. The method can be used e.g. to estimate a hypoxia parameter k3 image in the case of a FMISO data set where only late-time images are available. The method may be implemented as part of existing PET, SPECT, CT, MR or Ultrasound scanner software, and since only a limited amount of late time post injection images are necessary to provide a reliable result, the method helps to increase patient comfort and clinical throughput.
Method, signal processor, device, and system for estimating image mapping biological process