RESUMO
Several efforts have been focusing on the development of detectors devoted to high solution (99m)Tc sestamibi scintimammography to improve sensitivity for non palpable lesions. To this aim new high resolution scintillation gamma camera was developed under the "Integiated Mammographic Imaging" project. The gamma camera, made by CAEN and Pol.Hi.Tech, has an overall dimension of 112x120x75mm3. It consists of an array of 1 in. PSPMTs Hamamatsu H8520-C12 closely packed, a NaI(T1) scintillation array (1.8x1.8x6mm(3) pixel) and a general purpose collimator. By this gamma camera a clinical experience on a few patients with breast cancer suspicion was performed. In this paper we show how high resolution approach allows to better categorize the lesions on the basis of the morphology of the spatial distribution of the radiotracer in the breast tissue. By comparing conventional and high resolution images of a young patient (29 y.o.) with breast cancer suspicion, it appears clear how the Anger, camera images showed a defined hot spot, highly suggestive of malignant lesion; on the contrary, the high resolution scan shown a large and inhomogeneous uptake area with the absence of clear and focal character of the uptake, to be considered as a probably non malignant lesions. This resuh was confirmed by byoptical findings that diagnosed the echographic findings as a benign inflammatory lesion.
RESUMO
The recent development of new gamma imagers based on scintillation array with high spatial resolution, has strongly improved the possibility of detecting sub-centimeter cancer in Scintimammography. However, Compton scattering contamination remains the main drawback since it limits the sensitivity of tumor detection. Principal component image analysis (PCA), recently introduced in scintimam nographic imaging, is a data reduction technique able to represent the radiation emitted from chest, breast healthy and damaged tissues as separated images. From these images a Scintimammography can be obtained where the Compton contamination is "removed". In the present paper we compared the PCA reconstructed images with the conventional scintimammographic images resulting from the photopeak (Ph) energy window. Data coming from a clinical trial were used. For both kinds of images the tumor presence was quantified by evaluating the t-student statistics for independent sample as a measure of the signal-to-noise ratio (SNR). Since the absence of Compton scattering, the PCA reconstructed images shows a better noise suppression and allows a more reliable diagnostics in comparison with the images obtained by the photopeak energy window, reducing the trend in producing false positive.
RESUMO
Pinhole gamma camera imaging offers the ability to obtain high resolution images from single gamma ray emitting radiotracers playing a reasonable tradeoff between very small field of view (FoV) and sensitivity. On the other hand the total spatial resolution of a pinhole imaging device is predominantly affected by the detector intrinsic spatial resolution for reduced magnification factors. To design very compact pinhole SPET scanners with very high intrinsic spatial resolution, authors investigated a miniature gamma camera based on the newly developed Hamamatsu H8500 flat panel photomultiplier. The PSPMT was coupled to the following scintillation arrays: CsI(Tl) array with 0.2-mm, 1-mm, 1.4-mm pixel size and NaI (Tl) with 1-mm pixel size. The imaging performances were evaluated by 57Co spot and flood irradiations. NaI(Tl) array shows a better pixel identification for 1 mm pixel size, proving to be a good candidate to make a large area photodetector based on multi PSPMTs closely packed. Although CsI(Tl) array had the smallest pixel size, the low light output limited the best intrinsic spatial resolution to about 0.5 mm.