Prone breast tumor imaging using vertical axis-of-rotation (VAOR) SPECT systems: an initial study

The authors propose the use of a single photon emission computed tomography (SPECT) system equipped with multiple cameras which revolve around a vertical axis-of-rotation (VAOR) for prone-dependent (i.e., patient in prone position) breast tumor imaging. This geometry for nuclear medicine breast imaging reduces the amount of attenuating material between the breast tissue and the gamma camera and, in addition, it offers a minimal radius-of-rotation compared to breast imaging using conventional (i.e., 360°, horizontal axis-of-rotation) SPECT. The decrease in attenuation and radius-of-rotation results in an increase in detected counts and increased collimator resolution. Because VAOR SPECT systems are currently not commercially available, the authors conducted their experiments on a conventional SPECT system using an isolated breast phantom to investigate the proposed VAOR method. The authors´ experimental setup simulated a VAOR SPECT study with a prone-dependent breast in the camera´s field-of-view. The results of the experiment indicate that VAOR breast SPECT with Trionix low-energy super-high resolution (LESR) parallel-hole collimation is capable of detecting a breast lesion with an outer diameter of 10 mm and a lesion-to-background concentration ratio of 6-to-1. The results also demonstrate that VAOR breast SPECT provides improved lesion parallel-hole planar imaging (i.e., scintimammography) and breast imaging using horizontal axis-of-rotation SPECT