Analytical Study of the Effect of the System Geometry on Photon Sensitivity and Depth of Interaction of Positron Emission Mammography

Pablo Aguiar,Cristina Lois

doi:10.1155/2012/605076

Abstract

Positron emission mammography (PEM) cameras are novel-dedicated PET systems optimized to image the breast. For these cameras it is essential to achieve an optimum trade-off between sensitivity and spatial resolution and therefore the main challenge for the novel cameras is to improve the sensitivity without degrading the spatial resolution. We carry out an analytical study of the effect of the different detector geometries on the photon sensitivity and the angle of incidence of the detected photons which is related to the DOI effect and therefore to the intrinsic spatial resolution. To this end, dual head detectors were compared to box and different polygon-detector configurations. Our results showed that higher sensitivity and uniformity were found for box and polygon-detector configurations compared to dual-head cameras. Thus, the optimal configuration in terms of sensitivity is a PEM scanner based on a polygon of twelve (dodecagon) or more detectors. We have shown that this configuration is clearly superior to dual-head detectors and slightly higher than box, octagon, and hexagon detectors. Nevertheless, DOI effects are increased for this configuration compared to dual head and box scanners and therefore an accurate compensation for this effect is required.

Highlights

Breast cancer is one of the most commonly diagnosed cancers and one of the leading causes of cancer related deaths in women [1]
The results showed that the box geometry encircling the breast had better performance than the dual head detector as long as the depth of interaction (DOI) effect is compensated
Very high maximum mis-positioning values were found for all geometries at center and edge of the FOV. These results show a significant effect of the DOI on the mis-positioning of the photon interaction point and on the intrinsic spatial resolution for all detector geometries

Summary

Introduction

Breast cancer is one of the most commonly diagnosed cancers and one of the leading causes of cancer related deaths in women [1]. A number of imaging techniques can be used to aid in the diagnosis and staging of breast cancer, being anatomical imaging techniques such as X-ray mammography, ultrasonography, and magnetic resonance imaging (MRI) the most employed [2,3,4] These techniques are affected by two factors that limit their effectiveness: breast density and the woman’s hormonal status [5, 6]. Because of these limitations, many women with suspicious breast masses have to undergo invasive breast biopsies for accurate diagnosis. PET potentially translates into reduction in unnecessary breast biopsies, which could significantly lower costs associated with breast cancer detection and staging, and reduce patient trauma

Methods

Results

Conclusion