Breast tumour imaging using incomplete circular orbit pinhole SPET: a phantom study

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Oncology

Background:

• Single photon emission tomography (SPET) using 99Tcm-sestamibi is being evaluated for breast cancer diagnosis.
• Pinhole SPET offers higher resolution and sensitivity than parallel-beam collimation for near-aperture sources.
• The clinical utility of SPET alongside mammography requires improved visualization of small breast lesions.

Purpose of the Study:

• To investigate the potential of incomplete circular orbit (ICO) pinhole SPET for visualizing small simulated breast tumors.
• To compare ICO pinhole SPET with complete circular orbit (CCO) pinhole SPET and planar scintimammography.
• To assess the efficacy of ICO pinhole SPET at clinical count densities and tumor-to-background ratios.

Main Methods:

• A breast phantom with simulated tumors (6.4 and 9.6 mm) was imaged using a prototype pinhole collimator.
• Projections were acquired using ICO and CCO pinhole SPET, and planar scintimammography (parallel-beam and pinhole).
• Phantom data were reconstructed using filtered backprojection (FBP) and maximum likelihood-expectation maximization (ML-EM).

Main Results:

• Simulated tumors were not visualized with scintimammography (contrast < 2%, signal-to-noise < 0.01).
• ICO pinhole SPET achieved average contrast of 33% and signal-to-noise of 1.72.
• CCO pinhole SPET showed similar contrast (34%) but lower signal-to-noise (1.3).

Conclusions:

• ICO pinhole SPET demonstrates potential for improved visualization of small (< 10 mm) breast tumors compared to scintimammography.
• Enhanced visualization may aid in the early classification of breast cancers.
• Further research is warranted to define the clinical role of ICO pinhole SPET in breast cancer management.