Table 1.
Results from Monte Carlo simulations of several conical slant-hole (CSH) collimator designs with varying parameters. The default CSH parameter configuration was θ = 30°, A = 2 cm2, t = 0.3 mm, h = 1 cm, and k = 1, designated by bold. The parameters were allowed to deviate from the default value, with only a single parameter changing in each simulation. Count sensitivity was measured in images of the background only and in images of the lesion only relative to that of the current parallel-hole collimator design. Full-width-at-half-maximum (FWHM) of the circumferential count profile of a 1-cm lesion at 3 cm from the collimator and the absolute error of the estimated lesion depth are reported as the mean ± standard deviation for ten independent simulations that represented image acquisition times of 10 and 1 min.
| Background count | Lesion count | Absolute error of depth | FWHM of 1-cm lesion | ||||
|---|---|---|---|---|---|---|---|
| at 3 cm sensitivity (relative to | sensitivity (relative to | estimate (mm) |
from the collimator (cm) |
||||
| Variable | Value | parallel-hole design) | parallel-hole design) | 10 min | 1 min | 10 min | 1 min |
| Angle θ (deg) | 30 | 0.94 | 21.14 | 0.5 ± 0.2 | 1.1 ± 0.7 | 2.0 ± 0.1 | 2.0 ± 0.2 |
| 25 | 1.22 | 11.02 | 1.3 ± 0.5 | 1.0 ± 0.7 | 2.6 ± 0.0 | 2.7 ± 0.1 | |
| 20 | 1.56 | 9.84 | 2.0 ± 0.2 | 2.0 ± 1.2 | 3.5 ± 0.1 | 3.4 ± 0.2 | |
| 15 | 1.91 | 7.66 | 5.7 ± 0.5 | 5.6 ± 1.0 | 4.3 ± 0.2 | 4.4 ± 0.6 | |
| Area A (cm2) | 1.5 | 0.62 | 7.56 | 0.5 ± 0.2 | 0.8 ± 0.5 | 1.8 ± 0.0 | 1.8 ± 0.2 |
| 2 | 0.94 | 21.14 | 0.5 ± 0.2 | 1.1 ± 0.7 | 2.0 ± 0.1 | 2.0 ± 0.2 | |
| 2.5 | 1.35 | 14.48 | 0.4 ± 0.1 | 1.3 ± 0.8 | 2.3 ± 0.1 | 2.5 ± 0.3 | |
| 3 | 1.80 | 17.72 | 0.5 ± 0.2 | 1.5 ± 1.0 | 2.7 ± 0.2 | 2.9 ± 0.3 | |
| Thickness t (mm) | 0.2 | 1.34 | 12.58 | 0.4 ± 0.2 | 0.8 ± 0.5 | 2.8 ± 0.7 | 2.5 ± 0.2 |
| 0.3 | 0.94 | 21.14 | 0.5 ± 0.2 | 1.1 ± 0.7 | 2.0 ± 0.1 | 2.0 ± 0.2 | |
| 0.4 | 0.86 | 10.20 | 0.9 ± 0.3 | 0.7 ± 0.3 | 1.8 ± 0.1 | 1.9 ± 0.2 | |
| 0.5 | 0.81 | 9.60 | 0.9 ± 0.3 | 1.2 ± 0.9 | 1.8 ± 0.0 | 1.7 ± 0.1 | |
| Height h (cm) | 0.5 | 9.60 | 34.57 | 21.8 ± 0.2 | 21.2 ± 0.9 | Undefined | Undefined |
| 0.75 | 2.44 | 18.86 | 1.0 ± 0.3 | 1.2 ± 0.9 | Undefined | Undefined | |
| 1 | 0.94 | 21.14 | 0.5 ± 0.2 | 1.1 ± 0.7 | 2.0 ± 0.1 | 2.0 ± 0.2 | |
| 1.25 | 0.49 | 6.96 | 1.7 ± 0.5 | 1.5 ± 1.1 | 1.7 ± 0.1 | 1.7 ± 0.2 | |
| Wedge thickness | 0.5 | 1.68 | 13.25 | 0.7 ± 0.2 | 0.9 ± 0.6 | Undefined | Undefined |
| factor k | 0.75 | 1.16 | 12.00 | 0.3 ± 0.1 | 0.9 ± 0.6 | 2.7 ± 0.7 | 2.2 ± 0.3 |
| 1 | 0.94 | 21.14 | 0.5 ± 0.2 | 1.1 ± 0.7 | 2.0 ± 0.1 | 2.0 ± 0.2 | |
| 1.25 | 0.82 | 10.07 | 0.6 ± 0.3 | 1.0 ± 0.6 | 2.0 ± 0.0 | 2.0 ± 0.2 | |
| 1.5 | 0.72 | 9.17 | 0.7 ± 0.3 | 0.9 ± 0.6 | 2.0 ± 0.0 | 1.9 ± 0.2 | |