Abstract
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Objectives A dedicated breast PET camera potentially has 10-20 times higher detection sensitivity than a conventional PET because of its larger solid angle and lower attenuation of not having the chest in the field-of-view (FOV). However, such a dedicated PET cannot perform cancer staging and axillary-lesion imaging as the body cannot be fitted into the small ring. We have constructed a PET camera (HOTPET) with resolution better than 3 mm that can be transformed between breast mode and whole-body mode. In the breast (whole-body) mode HOTPET has transverse FOV of 39 (60) cm and axial FOV of 21 (13) cm. We compared the performance of the two modes of HOTPET for detection of breast lesions to measure the effective sensitivity gain in lesion detection by using a dedicated breast ring PET.
Methods We scanned a breast phantom with lesion inserts attached to a torso phantom. We used several lesions with diameters in the range of 3.95 to 7.86 mm for several lesion activities with standard uptake value (SUV) in the range of 0.8 to 8. The SUV of the breast, torso and heart were 0.8, 1, and 4, respectively.
Results The 7.86-mm lesion is observable for SUV of 1.75 in breast mode and for SUV of 2.5 body mode. The 4.95-mm lesion with SUV of 2.5 is observable in breast mode and with SUV of 5.5 in body mode. The 3.95-mm lesion is observable in breast mode for SUV of 4.
Conclusions For SUV of 2.5, we observe the 7.86-mm lesion in whole-body mode and the 4.95-mm lesion in breast mode. This shows the advantage of a dedicated breast PET camera. For small lesions, for typical clinical tumor threshold (SUV=3) lesion detectability based on lesion total activity can be improved by a factor of 3.5-4 with a dedicated breast ring PET.
Research Support This work was supported in part by the NIH Grant RO1 CA76246, NIH Grant RO1 EB00217, NIH Grant RO1 EB001038, NIH Grant RO1 EB001481 and US Army Breast Cancer Grant.
- © 2009 by Society of Nuclear Medicine