Schematic diagram of the SMOG system. (a) The grid is placed between the x-ray source and patient, and oscillates rapidly in the direction marked by the arrow. At each gantry angle, multiple exposures are taken with the grid moving by a distance equal to the grid interspace after each exposure. (b) Frontal view of the grid.
Data acquisition scheme of a triple-exposure SMOG system. Three partial projections are acquired at the same gantry angle. Each projection has the pattern of repetition of three different strips. The lags at the points A–D in the image strip can be corrected by lag at corresponding points A1–D1 in the dark shadow strip.
Model fitting for image lag weighting factor L n . The measured data were adapted from the paper published by Mail et al. (Ref. 30).
Change of scatter to primary ratio (SPR) with phantom thickness and transmission factor (TF).
Axial, coronal, and sagittal images of the enlarged CATphan phantom. (a) Conventional CBCT, (b) SMOG with 2-exposure (TF = 0.5), and (c) SMOG with 4-exposure (TF = 0.25).
(a) Open field and scatter distributions at different gantry positions (represented by projection numbers) for points A and C, and the corresponding points A1 and C1 at the imager. High intensity peaks correspond to x-ray passing through the air instead of the imaging object. (b) Initial lags and residual lags after correction using the SMOG system with 2- or 3-exposure at point A and C at different projections.
(a) Conventional CBCT with scatter and image lag. (b) CBCT after scatter correction using static grid (TF = 1/3, grid interspace width = 1.4 cm). (c) CBCT after scatter correction using SMOG (TF = 1/2, grid interspace width = 1.4 cm). (d) CBCT after scatter correction using SMOG (TF = 1/3, grid interspace width = 1.4 cm). (e) True CBCT with no scatter or image lag.
Profiles through the CBCT image reconstructed using different techniques; the profile position is indicated by a dotted line in Fig. 7(e).
CBCT imaging dose measurement for different scanning techniques using a CIRS CT dose phantom and a 0.6 cm3 Farmer-type chamber. Dose was measured at center of the phantom (position A), peripheral region of the head phantom inside (position B), and peripheral region of the abdominal phantom (position C).
Acquisition scheme of the static grid method. The grid is stationary, while projections are acquired at different gantry angles.
Schematic drawing of a simple crank and slider system.
CNR for different scanning techniques using a CATphan phantom.
Summary of lag simulation results for four points (A–D in Fig. 2), 2 grid interspace widths (1.4 and 2.8 cm in imaging plane), and different number of exposures in SMOG.
Total imaging dose measured with a 0.6 cm3 Farmer-type chamber in a CT dose phantom for different CBCT scanning techniques (scanning protocol: pelvis half-fan 125 kVp, 80 mA, 13 ms). Position A, B, and C are indicated in Fig. 9, Unit: cGy.
Comparison between estimated and measured CNR percentage enhancement for different SMOG scanning techniques.
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