Accurate scatter correction for transmission computed tomography using an uncollimated line array source

Abstract

We investigated scatter correction in transmission computed tomography (TCT) imaging by the combination of an uncollimated transmission source and a parallel-hole collimator. We employed the triple energy window (TEW) as the scatter correction and found that the conventional TEW method, which is accurate in emission computed tomography (ECT) imaging, needs some modification in TCT imaging based on our phantom studies. In this study a Tc-99m uncollimated line array source (area: 55 cm x 40 cm) was attached to one camera head of a dual-head gamma camera as a transmission source, and TCT data were acquired with a low-energy, general purpose (LEGP), parallel-hole collimator equipped on the other camera head. The energy spectra for 140 keV-photons transmitted through various attenuating material thicknesses were measured and analyzed for scatter fraction. The results of the energy spectra showed that the photons transmitted had an energy distribution that constructs a scatter peak within the 140 keV-photopeak energy window. In TCT imaging with a cylindrical water phantom, the conventional TEW method with triangle estimates (subtraction factor, K = 0.5) was not sufficient for accurate scatter correction (micro = 0.131 cm(-1) for water), whereas the modified TEW method with K = 1.0 gave the accurate attenuation coefficient of 0.153 cm(-1) for water. For the TCT imaging with the combination of the uncollimated Tc-99m line array source and parallel hole collimator, the modified TEW method with K = 1.0 gives the accurate TCT data for quantitative SPECT imaging in comparison with the conventional TEW method with K = 0.5.

Usefulness of imaging studies for diagnosing and localizing cerebrospinal fluid rhinorrhea: A systematic review and meta‐analysis

“…In general, gamma‐camera imaging is performed immediately after 6 and 24 hours after injection, and in some cases tracking is required after 48 and 72 hours. However, direct evidence of CSF leakage is not well confirmed, because there are many cases of leakage below the resolution limit 51 . In our study, RNC demonstrated significantly lower sensitivity compared with the other imaging modalities.…”

Scatter Correction for Heart SPECT images Using TEW method

“…Kojima et al (6) also showed that scattered photons transmitted through the object have a peak within the main energy window. Therefore, this study subtracted the Compton scatter windows (side windows) from the main window for scatter correction.…”

“…Perisinakis et al, (5) using double energy window (DEW) and TEW for scatter correction could distinguish lesions in liver studies. Akihiro Kojima et al, (6) investigated scatter correction in transmission computed tomography (TCT) imaging by the combination of an uncollimated transmission source and a parallel‐hole collimator. They employed the TEW as the scatter correction and found scattered photons transmitting through the object have a peak within the main energy window, based on their phantom studies.…”

The effect of milk, water and lemon juice on various subdiaphragmatic activity-related artifacts in myocardial perfusion imaging

“…Numerous studies have introduced many methods for eliminating the source of artifacts and for augmenting MPI accuracy ( 12 - 22 ). However, no investigations have been conducted so far on the effects of different protocols on various artifacts related to gastrointestinal activity.…”

“…Water, milk, soda, lemon juice, and fatty meals are different substances that investigators have tested, and they are known to change the pattern of extracardiac activity in MPI; however, there is still a paucity of data in the existing literature on the possible effects of those substances on different artifacts ( 12 - 22 ). Hara et al noted that reduction of subcardiac activity can occur by drinking small amounts of soda as the result of stomach distention, drawing gastrointestinal activity away from the myocardium ( 5 ).…”