High-resolution scintimammography improves the accuracy of technetium-99m methoxyisobutylisonitrile scintimammography: use of a new dedicated gamma camera

The main disadvantage of technetium-99m methoxyisobutylisonitrile (MIBI) pr one scintimammography is its limited sensitivity for T1a and T1b cancers wi th a size of less than 1 cm. We have developed a high-resolution scintimamm ographic technique using a gamma camera based on a new concept, namely a po sition-sensitive photo-multiplier tube. The field of view of this camera, p reviously known as the SPEM (single photon emission mammography) camera, wa s 10 cm diameter. Scintimammographic images were acquired in the axial view ; each breast was compressed to a thickness of 3-6 cm, modal class 4 cm. Wh en the compressed breast was larger than the field of view, more than one s tudy was performed in order to image the entire gland. Fifty-three patients were studied with high-resolution-scintimammography (HRSM) and Anger camer a prone scintimammography (ACPSM), HRSM was performed 70 min after i.v. adm inistration of 740 Mbq of Tc-99m-MIBI; ACPSM images were acquired 10 and 60 min following the injection. Early 10-min ACPSM images were only evaluated for routine diagnostic purposes, while comparison was carried out between the 60-min ACPSM and 70-min HRSM images, At fine-needle aspiration (FNA) an d/or open biopsy, 31 patients showed cancer: 15 T1c, 11 T1b and 5 T1a, In T 1a-T1b cancers, the sensitivity of scintimammography was 50% with ACPSM and 81.2% with HRSM (P<0.01). Specificity was 86% with both techniques. HRSM i s a promising new technique that improves the sensitivity of 99mTc-MIBI sci ntimammography in tumours sized less than 1 cm without apparently reducing its specificity. We are now working on a larger field-of-view camera.