Comparison of 2D scintimammography and 3D dedicated breast SPECT using a compressible breast phantom and lesions of varying size and tracer uptake

This study aims to qualitatively and quantitatively compare 2D planar scintimammography imaging of the breast under various degrees of compression with uncompressed, dedicated 3D SPECT using dedicated acquisition trajectories. A 700mL compressible anthropomorphic breast phantom containing small lesions was developed to compare 2D and 3D breast imaging. Thin walled, deformable lesions ranging from 40 to 500uL volume suspended on a thin plastic sheet in the phantom were used to mimic breast lesions undergoing different degrees of compression. Using a 16×20cm² CZT-based gamma camera, ^99mTc-scintimammography was performed for 10min imaging times for compression thicknesses of 6 and 12cm (fully uncompressed) using a single mediolateral view. Dedicated breast SPECT was then performed for 10min using the uncompressed breast acquired with a simple tilted rotation, and a complex 3D acquisition trajectory. Experimental variables include: (1) background torso contamination; (2) (in)homogeneous breast composition; and (3) low count (clinically relevant) and high count (low noise) images. The radioactivity lesion:background concentration ratio was varied from 12:1 down to 3:1. A comparison between the two modalities was made in a limited observer study with independent observers evaluating reconstructed images for the smallest detectable lesion and total number of lesions. Image quality, based on lesion SNRs and contrasts were also evaluated. SPECT images appear to yield observation of smaller and more simulated lesions than those seen in scintimammography, additionally with more than twice the SNR and contrast. Due to greater positioning flexibility of the SPECT system gantry, under a wide range of measurement conditions, statistically significantly (p≪0.05) more lesions, smaller lesion sizes, and (3D) lesion locations were detected with dedicated breast SPECT than with compressed breast scintimammography.