Dedicated gamma camera for single photon emission mammography (SPEM)

Prone scintimammography with Tc-99m SestaMIBI has been proposed as a method of detecting breast cancers in women with dense breasts. Clinical reports have shown that this technique lacks sensitivity for cancer smaller than 1 cm. To overcome some limitations offered by Auger camera on breast imaging was realized a new scintigraphic detector dedicated to SPEM (Single Photon Emission Mammography). This novel small FOV device, shows high spatial resolution performances (<2 mm), but poorer energy resolution values, than Auger camera (17% vs. 10%, respectively). In this paper the authors examine the spatial distribution of Compton-to-photopeak ratio in planar scintimammographic images in order to elucidate the causes of lack of scintimammography in visualizing deep or posteriorly located cancers introduced by the scatter from the patient´s body. Phantom and clinical studies with several instruments including a general purpose gamma camera, a dedicated camera and a non-imaging Germanium detector were performed. The results obtained suggest that scatter from extramammary sources plays an important role in breast imaging with radiotracers. By using gentle breast compression in cranio-caudal view the energy resolution attained with the dedicated camera is adequate to differentiate between photopeak and Compton counts; the Compton-to photopeak mean ratio resulted 4.5 and 6.9 for mid portion and posterior breast respectively