Title :
Multiscale wavelet filter for high resolution radioisotopic images
Author :
Pousse, A. ; Dornier, C. ; Fagot, L. ; Parmentier, M. ; Kastler, B.
Author_Institution :
Lab. d´´Imagerie et d´´Ingenierie pour la Sante, Univ. de Franche-Comte, Besancon, France
fDate :
12/1/2000 12:00:00 AM
Abstract :
Radioisotopic Investigations are very useful for functional diagnosis, but available gamma cameras have poor spatial resolution. Development of new PSPMT based high-resolution detectors brings new interests to this medical imaging technique. However, the Poissonian nature of emitted photon flux and low count images due to low doses administered to the patients and to collimation, lead to images with granular aspect. This noisy appearance is particularly inconvenient when looking for cold nodules as in thyroid examinations. Low-pass filters, which reduce noise, are not well suited for detecting small cold nodules. An adapted translation invariant wavelet filter is designed which takes into account the poissonian feature of noise and preserves small sized structures. The filter was tested by Monte Carlo simulations, phantom and clinical thyroid scintigraphies. Cold spherical nodules as small as 4 mm in diameter are easily detected on filtered images acquired with IRIS (ARIES) high-resolution gamma ray imaging probe. Presentation of filtered images at different scales offering enhanced visual quality and lowered noise, simultaneously with original image, allows more comfortable analysis and improves scintigraphic diagnosis ability
Keywords :
Monte Carlo methods; biological organs; image resolution; medical image processing; radioisotope imaging; wavelet transforms; 4 mm; Monte Carlo simulations; PSPMT based high-resolution detectors; Poissonian nature; adapted translation invariant wavelet filter; clinical thyroid scintigraphies; cold nodules; cold spherical nodules; emitted photon flux; granular aspect; medical diagnostic imaging; medical imaging technique; noisy appearance; nuclear medicine; phantom scintigraphies; spatial resolution; thyroid examinations; Biomedical imaging; Cameras; Detectors; Image resolution; Imaging phantoms; Low pass filters; Noise reduction; Optical collimators; Spatial resolution; Testing;
Journal_Title :
Nuclear Science, IEEE Transactions on