Breast tumor imaging using a tiltable head SPECT camera

As a test bed for dedicated breast single-photon emission computed tomograp hy (SPECT) cameras that are under development, a general purpose SPECT syst em with two tiltable heads was used to image fillable breast and torso phan toms containing multiple lesions. Breast, liver, and myocardial activity we re included in order to simulate direct contamination and Compton scatterin g expected in clinical scans. The tiltable-head SPECT (TH-SPECT) data were reconstructed using an OS-EM algorithm which accounted for the tilted geome try. High-count planar images were acquired for comparison with TH-SPECT. I n order to characterize axial blurring effects inherent with TH-SPECT recon structions, two cylindrical disk Defrise phantoms, one large Defrise phanto m and one mini-Defrise phantom placed inside the fillable breast phantom, w ere imaged at various tilt angles. Results indicate an increase in axial bl urring with greater tilt angle. Reconstructions of the combined fillable br east and torso phantoms containing two 1.15 ml lesions, one centered axiall y 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 thre e times compared to the high-count planar images.