Spatial resolution and geometric efficiency of pinhole collimator in scintimammography

Scintimammogram(SM) using Tc-99m labeled sestamibi is a sensitive and specific diagnostic technique for breast cancer detection when cancers are more than 1 cm in size. However the sensitivity falls in the case of subcentimetric lesions. The aim of this study is to evaluate the spatial resolution and geometric efficiency of pinhole(PH) SM and a conventional camera system equipped with low energy all purpose (LEAP) collimator. A scintillation camera used is a single head Siemens Orbiter. The scintigrams were obtained experimentally with a 4 mm aperture PH and LEAP collimator. The resolutions were measured in terms of the full width at half maximum (FWHM) of the line spread function. A breast phantom was home made using paraffin of a realistic size, shape and tissue composition of the breasts. By using aperture size of 4 mm, PH and LEAP collimator the following results were obtained; the spatial resolutions of 4.98 and 9.17 mm respectively in acquisition matrix of 128 x 128 at 10 cm distance from aperture and at the surface of LEAP collimator. The geometric efficiency of pinhole collimator was 0.5 times of LEAP collimator. In conclusion our study shows the image resolution of pinhole collimator is better than that of single or dual head Siemens Mutispect2 which has resolution of 7.64 mm. Using this information we are doing clinical research comparing between PHSM and conventional prone lateral scintimammogram