Optimisation of window settings for quantitative 111In imaging – a comparison of measurements to Monte Carlo

Abstract: Quantification in Nuclear Medicine Imaging is highly desirable for a number of reasons. In Targeted Radionuclide Therapy for example, accurate estimation of the absorbed dose delivered to the patient depends upon accurately quantified images. In Tracer Kinetic Studies quantification is also required in order to obtain accurate biodistribution data. One of the major problems connected with Nuclear Medicine Imaging is scattered radiation. Photons emitted within the patient can be scattered by the patients themselves or by the collimator of the imaging system. This results in loss of energy and spatial information leading to degradation in image quality.A widely used method for scatter correction is subtraction of images formed using energy windows in the region of the photopeaks. In this thesis a number of different energy window settings for the isotope 111In are investigated using both phantom experiments and Monte Carlo simulations with the code SIMIND. Parameters used for comparison of the different window settings include; spatial resolution, sensitivity, image contrast, activity quantification and spill out. Also, the fraction of scattered photons in the detected spectra is investigated for the Monte Carlo modelled data and compared to the calculated experimental Scatter to Total Ratios for the various window settings.For each of the scatter correction techniques experimental and Monte Carlo calculated results are tabulated and compared. The scatter correction techniques are then intercompared. Finally recommendations are made as to which is the best performing technique.