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.