Article Figures & Data
Figures
- FIGURE 1.
(A) parallel beam collimator and (B) fan beam collimator with cubic holes.
- FIGURE 2.
Calculation of angles in fan beam collimator, in which slanted cubic hole has different cross sections.
- FIGURE 3.
Point source in scatter medium in front of collimator at z = 10 cm (A) and z = 15 cm (B).
- FIGURE 4.
(A) Simulated fan beam geometric efficiency lessens when angle of slant hole is increased. (B) Simulated fan beam geometric efficiency increases when point source distance from collimator surface is increased for different θs.
- FIGURE 5.
(A) Simulated fan beam geometric resolution decreases when angle of cubic hole is reduced for different z values. (B) Simulated effective resolution increases when angle of holes is increased.
- FIGURE 6.
Simulated radial point spread functions for fan beam and parallel beam with cubic hole shape when point source is set at z = 10 cm in air phantom (A) and water phantom (B). FB = fan beam; PB = parallel beam; w = water.
Tables
Characteristic Value Thickness (cm) 3.28 Hole size (cm) 0.140 Septal width (cm) 0.0152 Ratio of hole area to septal area 0.7682 Source–collimator surface distance (cm) Resolution (cm) z = 10 z = 15 Effective 0.6119 0.8314 Total 0.7256 0.9183 Effective hole length = 3.189 cm;
for lead at 140 keV and B = 0.75 cm.
Source–collimator surface distance (cm) Angle (degree) z = 10 z = 15 1.6216 12.0024 15.6770 3.2419 11.9449 15.6010 4.8595 11.8497 15.4770 6.4733 11.7180 15.3050 8.0818 11.5512 15.0870 9.6839 11.3510 14.8260 11.2783 11.1196 14.5236 12.8638 10.8595 14.1838 14.4393 10.5732 13.8099 16.0035 10.2636 13.4055 17.5555 9.9337 12.9746 19.0942 9.5864 12.5211 20.6186 9.2250 12.0490 22.1277 8.8523 11.5623 23.6206 8.4715 11.0648 - TABLE 4
Calculated Fan Beam Effective Resolution at Various Distances from Collimator Surface
Source–collimator surface distance (cm) Angle (degree) z = 10 z = 15 1.6216 0.4274 0.5036 3.2419 0.4279 0.5042 4.8595 0.4287 0.5052 6.4733 0.4299 0.5066 8.0818 0.4315 0.5084 9.6839 0.4334 0.5106 11.2783 0.4356 0.5133 12.8638 0.4382 0.5163 14.4393 0.4411 0.5198 16.0035 0.4444 0.5236 17.5555 0.4480 0.5279 19.0942 0.4521 0.5326 20.6186 0.4564 0.5378 22.1277 0.4612 0.5434 23.6206 0.4663 0.5494 Source–collimator surface distance (cm) Angle (degree) z = 10 z = 15 1.6216 0.5152 0.5636 3.2419 0.5156 0.5641 4.8595 0.5163 0.5650 6.4733 0.5173 0.5663 8.0818 0.5186 0.5679 9.6839 0.5202 0.5699 11.2783 0.5221 0.5722 12.8638 0.5242 0.5750 14.4393 0.5267 0.5781 16.0035 0.5294 0.5816 17.5555 0.5325 0.5855 19.0942 0.5359 0.5897 20.6186 0.5395 0.5944 22.1277 0.5436 0.5994 23.6206 0.5479 0.6049 - TABLE 6
Simulated FWHM (cm) for Parallel Beam and Fan Beam Collimators with Cubic Hole While Point Sources Are Located in Air and Water Phantoms
Source–collimator surface distance (cm) z = 10 z = 15 Collimator Air Phantom (2 cm) Air Phantom (7 cm) System parallel beam 0.80 0.87 0.95 1.22 Geometric parallel beam 0.59 0.86 System fan beam 0.79 0.81 0.91 1.16 Geometric fan beam 0.58 0.82 - TABLE 7
Comparison of Simulated FWHM (cm) with Values Reported by ADAC at z = 10 cm with 89,600 Holes
Parallel beam Fan beam Resolution Simulated Reported Simulated Reported Effective resolution 0.59±0.02 0.63 0.58±0.02 0.60 Total resolution 0.80±0.02 0.74 0.79±0.02 0.71 - TABLE 8
Amount of Simulated Penetration and Scatter Percentage in Air and Water Phantoms Related to Distance from Collimator Surface
z = 10 cm z = 15 cm Collimator Air Phantom Air Phantom Parallel beam 3.07 3.25 1.72 1.97 Fan beam 3.20 5.73 2.15 3.21
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