A newly designed technique for experimental single-photon emission tomography (SPET) and positron emission tomography (PET) data acquisition with minor disturbing effects from scatter and attenuation has been developed. In principle, the method is based on discrete sampling of the radioactivity distribution in 3D objects by means of equidistant 2D planes. The starting point is a set of digitised 2D sections representing the radioactiv- ity distribution of the 3D object. Having a radioactivity- related grey scale, the 2D images are printed on paper sheets using radioactive ink. The radioactive sheets can be shaped to the outline of the object and stacked into a 3D structure with air or some arbitrary dense material in between. For this work, equidistantly spaced transverse images of a uniform cylindrical phantom and of the digi- tised Hoffman rCBF phantom were selected and printed out on paper sheets. The uniform radioactivity sheets were imaged on the surface of a low-energy ultra-high- resolution collimator (4 mm full-width at half-maxi- mum) of a three-headed SPET camera. The reproducibil- ity was 0.7% and the uniformity was 1.2%. Each rCBF sheet, containing between 8.3 and 80 MBq of 99m TcO 4 - depending on size, was first imaged on the collimator and then stacked into a 3D structure with constant 12 mm air spacing between the slices. SPET was performed with the sheets perpendicular to the central axis of the camera. The total weight of the stacked rCBF phantom in air was 63 g, giving a scatter contribution comparable to that of a point source in air. The overall attenuation losses were <20%. A second SPET study was performed with 12-mm polystyrene plates in between the radioac- tive sheets. With polystyrene plates, the total phantom weight was 2300 g, giving a scatter and attenuation mag- nitude similar to that of a patient study. With the pro- posed technique, it is possible to obtain "ideal" experimental images (essentially built up by primary photons) for comparison with "real" images degraded by photon scattering and attenuation losses. The method can serve as a tool for experimental validation and intercomparison of attenuation and scatter correction methods. Moreover, the large flexibility of this phantom design will allow in- vestigations of arbitrary activity distributions and autora- diography or other imaging techniques such as PET, x-ray computed tomography or magnetic resonance imaging.
A novel phantom design for emission tomography enabling scatter- and attenuation-"free" single photon emission tomography imaging
Pagani M;
2000
Abstract
A newly designed technique for experimental single-photon emission tomography (SPET) and positron emission tomography (PET) data acquisition with minor disturbing effects from scatter and attenuation has been developed. In principle, the method is based on discrete sampling of the radioactivity distribution in 3D objects by means of equidistant 2D planes. The starting point is a set of digitised 2D sections representing the radioactiv- ity distribution of the 3D object. Having a radioactivity- related grey scale, the 2D images are printed on paper sheets using radioactive ink. The radioactive sheets can be shaped to the outline of the object and stacked into a 3D structure with air or some arbitrary dense material in between. For this work, equidistantly spaced transverse images of a uniform cylindrical phantom and of the digi- tised Hoffman rCBF phantom were selected and printed out on paper sheets. The uniform radioactivity sheets were imaged on the surface of a low-energy ultra-high- resolution collimator (4 mm full-width at half-maxi- mum) of a three-headed SPET camera. The reproducibil- ity was 0.7% and the uniformity was 1.2%. Each rCBF sheet, containing between 8.3 and 80 MBq of 99m TcO 4 - depending on size, was first imaged on the collimator and then stacked into a 3D structure with constant 12 mm air spacing between the slices. SPET was performed with the sheets perpendicular to the central axis of the camera. The total weight of the stacked rCBF phantom in air was 63 g, giving a scatter contribution comparable to that of a point source in air. The overall attenuation losses were <20%. A second SPET study was performed with 12-mm polystyrene plates in between the radioac- tive sheets. With polystyrene plates, the total phantom weight was 2300 g, giving a scatter and attenuation mag- nitude similar to that of a patient study. With the pro- posed technique, it is possible to obtain "ideal" experimental images (essentially built up by primary photons) for comparison with "real" images degraded by photon scattering and attenuation losses. The method can serve as a tool for experimental validation and intercomparison of attenuation and scatter correction methods. Moreover, the large flexibility of this phantom design will allow in- vestigations of arbitrary activity distributions and autora- diography or other imaging techniques such as PET, x-ray computed tomography or magnetic resonance imaging.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
