The concept of in-air output ratio (Sc) was introduced to characterize how the incident photon fluence per monitor unit (or unit time for a Co-60 unit) varies with collimator settings. 2 This quantity is also called inair output factor, collimator-scatter factor, and headscatter factor. 6 The latter two names were somewhat misleading since they emphasized a single component of the output ratio....

The modeling of 3D Compton scatter in SPECT is complicated by the use of a variety of collimator geometry. To date, effective and efficient modeling of 3D Compton scatter in parallel-beam SPECT has been made possible by Frey and Tsui [1], Zeng et al [2], and Bai et al [3]. For fan-beam and cone-beam SPECT, the model in [3] can effectively model first order 3D Compton scatter. But for varying-fo...

Abstract Purpose The quantitative accuracy of Nuclear Medicine images, acquired for both planar and SPECT studies, is influenced by the isotope-collimator combination as well image corrections incorporated in iterative reconstruction process. These factors can be investigated optimised using Monte Carlo simulations. This study aimed to evaluate quantification 123 I with low-energy high resoluti...

The characterization of the incident photon beam is usually divided into its dependence on collimator setting (head-scatter factor) and off-axis position (primary off-axis ratio). These parameters are normally measured "in air" with a build-up cap thick enough to generate full dose build-up at the depth of dose maximum. In order to prevent any influence from contaminating electrons, it has been...

A dosimetry system based on Al2O3:C radioluminescence (RL), and RADPOS, a novel 4D dosimetry system using microMOSFETs, were used to measure total scatter factors, (S(c,p))(f(clin))(det), for the CyberKnife robotic radiosugery system. New Monte Carlo calculated correction factors are presented and applied for the RL detector response for the 5, 7.5 and 10 mm collimators in order to correct for ...

UNLABELLED We determined the relative effect of corrections for scatter, depth-dependent collimator response, attenuation, and finite spatial resolution on various image characteristics in cardiac SPECT. METHODS Monte Carlo simulations and real acquisition of a 99mTc cardiac phantom were performed under comparable conditions. Simulated and acquired data were reconstructed using several correc...