Monte Carlo simulation of breast tumor imaging properties with compact, discrete gamma cameras

Abstract

We describe Monte Carlo simulation results for breast tumor imaging using a compact, discrete gamma camera. The simulations were designed to analyze and optimize camera design, particularly collimator configuration and detector pixel size. Simulated planar images of 5-15 mm diameter tumors in a phantom patient (including a breast, torso, and heart) were generated for imaging distances of 5-55 mm, pixel sizes of 2x2-4x4 mm2, and hexagonal and square hole collimators with sensitivities from 4000 to 16,000 counts/mCi/sec. Other factors considered included T/B (tumor-to-background tissue uptake ratio) and detector energy resolution. Image properties were quantified by computing the observed tumor fwhm (fullwidth at half-maximum) and S/N (sum of detected tumor events divided by the statistical noise). Results suggest that hexagonal and square hole collimators perform comparably, that higher sensitivity collimators provide higher tumor SM with little increase in the observed tumor fwhm, that smaller pixels only slightly improve tumor fwhm and S/N, and that improved detector energy resolution has little impact on either the observed tumor fwhm or the observed tumor S/N.

Molecular breast imaging: First results from Italian-National-Institute-of-Health clinical trials

“…Key parameters for detecting small lesions are: spatial resolution, signal to noise Ratio (SNR) and contrast. Energy resolution plays only a secondary additional role in imaging breast under compression [4,5]. After through optimization of intrinsic detector properties, the collimation technique has to be carefully designed in order to maximize the SNR, which is critical in the detection of small lesions with low uptake.…”

Molecular imaging: High-resolution detectors for early diagnosis and therapy monitoring of breast cancer

“…Key parameters for detecting small lesions are: spatial resolution, Signal to Noise Ratio (SNR) and contrast. Energy resolution plays only a secondary additional role when imaging breast under compression [4,5]. After thorough optimisation of intrinsic detector properties, the collimation technique has to be carefully designed in order to maximise the SNR, which is critical in the detection of small lesions with low uptake.…”

A Modular Description of the Geometry in Monte Carlo Modeling Studies for Nuclear Medicine

“…This apparatus represents a common phantom used in scintimammographic studies. 3 In order to emulate a clinical examination, the number of simulated photons is calculated from an imaging time of 10 minutes and a background activity of 80 nCi/cc is assumed for the torso and the breast. Heart and tumor are characterized by a Tumor to Background (T/B) ratio of, respectively, 20:1 and 5:1, gaining a specific activity of 1600 nCi/cc and 400 nCi/cc.…”

“…Monte Carlo methods offer a possibility of gaining an understanding of the physics that forms images and provide help in developing procedures to improve these images. Simulations can also be helpful in the choice of the camera design in SPECT (Single Photon Emission Computed Tomography) studies 3 : parameters such as collimator configuration and detector pixel size are often first optimized by means of simulated data and then experimentally tested.…”