Room: Exhibit Hall | Forum 8
Purpose: Mammography is currently the gold standard for breast cancer screening and has significantly reduced breast cancer mortality worldwide. Coincident with 2D radiography developed from X-rays penetrating breasts being imaged, 3D ultrasound signals are generated by tissue absorbing photon energy due to a process analogous to the photoacoustic effect, known as the X-ray-induced acoustic effect first observed in the 1980s. The latter has potential for use to reconstruct 3D computed tomography (XACT) images â€œfor freeâ€? in parallel with/to complement radiography. In theory, the single pulse of a mammography system is sufficient to generate ultrasound signals in 3D. Here, we investigated feasibility of the technique for low-dose volumetric X-ray acoustic imaging of the breast.
Methods: A noise equivalent pressure (NEP) model was developed for a commercial ultrasound transducer chosen for this study. GATE/Geant4 Monte Carlo simulations of breast phantoms irradiated with pulsing pencil beams were performed. Maps of energy deposition/dose absorption and NEP were calculated for use with the k-Wave acoustics toolbox to perform k-space pseudospectral time domain simulations of ultrasound signals and subsequently, time-reversal XACT reconstructions. Signal-to-noise ratio (SNR) analysis was performed on XACT images produced against dose absorbed. Dose fluence distribution were also investigated in a case-study of an average fibroglandular tissue density breast.
Results: A novel X-ray acoustic imaging platform is designed. Our studies showed the XACT technique has the ability to detect micro-calcifications expressed in typical breasts as small as 100Âµm in size within dose levels of standard mammographic exams as well with high SNR.
Conclusion: Exploration for feasibility of breast XACT has been conducted with initial characterization illustrating positive value of the technique. XACT has the potential to augment diagnostic systems to produce 3D XACT images in parallel with mammographic radiography within the same dose levels, especially if mammography could make use of pulsed X-ray tubes.