Mixed wavelet-watershed method for nodule detection in high resolution scintigraphy

The recent developments in gamma cameras have lead to significant improvement of intrinsic spatial resolution in radioisotopic imaging. Moreover, the use of smaller photodetectors (PSPMT, photodiodes) enables to build more compact devices which allows to place the detector very near from the organ under study and thus to enhance the global spatial resolution. However, these improvements need the use of smaller image pixel sizes which worsens signal to noise ratio in every pixel. Moreover, a lot of examinations, such as scintimammography will be all the more useful since small nodules can be detected. In this work, we present a method combining a denoising wavelet filtering method with watershed determination, both leading to hot nodule enhancement. This method was applied to Monte Carlo simulations of a 64 mm high volume containing hot nodules of various sizes with a tumor to background ratio equal to 5. Although nodules were not visible in raw images corresponding to 10 min acquisition, the described process allowed to detect 87% of 6 mm nodules and more than 97% of nodules whose diameter was greater or equal to 7 mm. Furthermore, the whole process runs very fast