Evaluation of fully 3-D emission mammotomography with a compact cadmium zinc telluride detector

Abstract

A compact, dedicated cadmium zinc telluride (CZT) gamma camera coupled with a fully three-dimensional (3-D) acquisition system may serve as a secondary diagnostic tool for volumetric molecular imaging of breast cancers, particularly in cases when mammographic findings are inconclusive. The developed emission mammotomography system comprises a medium field-of-view, quantized CZT detector and 3-D positioning gantry. The intrinsic energy resolution, sensitivity and spatial resolution of the detector are evaluated with Tc-99m (140 keV) filled flood sources, capillary line sources, and a 3-D frequency-resolution phantom. To mimic realistic human pendant, uncompressed breast imaging, two different phantom shapes of an average sized breast, and three different lesion diameters are imaged to evaluate the system for 3-D mammotomography. Acquisition orbits not possible with conventional emission, or transmission, systems are designed to optimize the viewable breast volume while improving sampling of the breast and anterior chest wall. Complications in camera positioning about the patient necessitate a compromise in these two orbit design criteria. Image quality is evaluated with signal-to-noise ratios and contrasts of the lesions, both with and without additional torso phantom background. Reconstructed results indicate that 3-D mammotomography, incorporating a compact CZT detector, is a promising, dedicated breast imaging technique for visualization of tumors < 1 cm in diameter. Additionally, there are no outstanding trajectories that consistently yield optimized quantitative lesion imaging parameters. Qualitatively, imaging breasts with realistic torso backgrounds (out-of-field activity) substantially alters image characteristics and breast morphology unless orbits which improve sampling are utilized. In practice, the sampling requirement may be less strict than initially anticipated.

Breast-Dedicated Radionuclide Imaging Systems

“…BD SINGLE-PHOTON CAMERA DESIGNS System Configuration BD single-photon (g) cameras can be split into 3 categories: SPECT (21,22); limited-angle tomography, commonly called breast tomosynthesis (23); and projection imaging by compressing the breast between two stationary collimated scintillation detection panels, a technique referred to as breast-specific g-imaging (BSGI) (24) or molecular breast imaging (MBI) (25). In contrast to breast imaging performed with PET, imaging using single-photon radiotracers requires the use of a collimator in front of a detector to provide directional information about the incoming photon.…”

Development and Optimization of a Dedicated, Hybrid Dual-Modality SPECT-CmT System for Improved Breast Lesion Diagnosis

“…SPECT images were acquired using a complex acquisition trajectory, three-lobed sinusoid projected onto a hemisphere (PROJSINE) with polar tilting range (sinusodial amplitude) from 15 to 45°. This trajectory for SPECT has been investigated previously [19,27]. CT images were acquired using a fixed 6.2° tilted circular trajectory.…”

Characterization of simulated incident scatter and the impact on quantification in dedicated breast single-photon emission computed tomography

“…Several groups, including our lab, have investigated breast SPECT as a tool for improved detection, diagnosis, or treatment monitoring. [11][12][13][14][15][16][17][18] Additionally, both nontraditional acquisition trajectories and variable-angle collimators with dedicated breast SPECT have shown promise for improved lesion detection, [11][12][13]18 but these data acquisition methods may involve inclusion of high-activity regions outside of the breast.…”

“…11,12 Truly, any arbitrary trajectory in a hemispherical geometry is possible with the dedicated breast SPECT system in our lab. [11][12][13] Understanding the impact of scatter in projections from these nontraditional trajectories is necessary for the application of any scatter correction method for quantitative imaging.…”

“…Both traditional and nontraditional acquisition trajectories, such as those possible with the SPECT subsystem of our dedicated breast SPECT-CT system, 11 are included to determine the change in the incident scatter distribution on a detector as a function of detector position. The impact on the application of the DEW scatter correction method with various acquisition trajectories is also investigated.…”