Breast tumor imaging using a tiltable head SPECT camera

As a test bed for dedicated breast single-photon emission computed tomography (SPECT) cameras that are under development, a general purpose SPECT system with two tiltable heads was used to image fillable breast and torso phantoms containing multiple lesions. Breast, liver, and myocardial activity were included in order to simulate direct contamination and Compton scattering expected in clinical scans. The tiltable-head SPECT (TH-SPECT) data were reconstructed using an OS-EM algorithm which accounted for the tilted geometry. High-count planar images were acquired for comparison with TH-SPECT. In order to characterize axial blurring effects inherent with TH-SPECT reconstructions, two cylindrical disk Defrise phantoms, one large Defrise phantom and one mini-Defrise phantom placed inside the fillable breast phantom, were imaged at various tilt angles. Results indicate an increase in axial blurring with greater tilt angle. Reconstructions of the combined fillable breast and torso phantoms containing two 1.15 ml lesions, one centered axially and one proximal to the anterior chest wall within the breast, were most clearly visible in the 30 degrees reconstructed TH-SPECT images, providing lesion signal-to-noise ratio (SNR) and contrast improvements of nearly three times compared to the high-count planar images.