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Positron emission mammography

Alla Reznik

Breast cancer is a serious and widespread disease that affects about one in eight women during their lifetime. Early diagnosis is crucial for effective treatment; there is a need for better and more specific detection than currently possible by screening using only X-ray mammography, now the primary imaging technique for the detection of breast lesions.

We are developing a positron emission mammography (PEM) camera that maintains the established high specificity of positron emission tomography (PET) for breast cancer detection while providing improved collection efficiency for the radiotracer signal and the potential for images with better spatial resolution [1]. The camera will use an amorphous selenium (a-Se) avalanche layer to capture light from a scintillation crystal.

A conceptual view of the system is shown in Figure 1. The PEM and X-ray mammography components are designed to image the lightly compressed breast in a single session, enabling efficient spatial registration of images from the two modalities. The PEM detectors are sensitive to the signal from a radiotracer (e.g., fluorodeoxyglucose) that is administered to the patient and accumulates at a higher rate in cancerous regions than in healthy tissue or benign lesions.

Figure 2 is an exploded view of the components in a PEM detector. High-energy photons from the decaying radiotracer are stopped in the scintillation array and produce visible light. The light is converted into an electrical signal and amplified by the a-Se layer. The signal is then read out by an active matrix array.

Our experimental work is concerned with the following:

  1. measurement of the gain that is available from an a-Se avalanche layer
  2. the transit time for charge transfer across the layer
  3. evaluation of the energy resolution of a prototype in which the scintillator LYSO is used

This project is funded by a Susan G. Komen Breast Cancer Foundation Research Grant (SHARP Camera for Positron Emission Mammography).

Reference

  1. A. Reznik, B.J.M. Lui, J.A. Rowlands, “An amorphous selenium based positron emission mammography camera with avalanche gain,” Technology in Cancer Research and Treatment, 4(1), 61-68 (2005).