FIGURE 1.
Parameter measurement diagram. For each patient, at the height of the vertebral body corresponding to the right diaphragm top during free breathing, anteroposterior thoracic diameter (ATD), transverse thoracic diameter (TTD) and maximum heart distance (MHD) were measured on free breathing CT images and deep inspiration breath-hold CT images respectively. Point A at the center of the sternum, and point B at the center of the medulla, the line AB was constructed as the ATD. Through the center of the line AB at M, a second line was constructed perpendicular to AB reaching the lateral edge of the lung at C and D, and the line CD was the TTD. The line AD approximates the direction of the tangential field, and the maximum distance from the left edge of the heart to AD is taken as the MHD.
TABLE 1.
The values of respiratory characteristic parameters in free breathing (FB) and/or deep inspiration breath holding (DIBH), and the differences in the values of some respiratory characteristic parameters between DIBH and FB (N = 98)
| Parameters | FB | DIBH | Δ |
|---|---|---|---|
| MHD (mm) | 26.8 (±5.1) | 18.4(±7.5) | −8.3 (±5.9) |
| ATD (mm) | 127. 0(±11.6) | 139.0(±11.6) | 11.0 (±3.8) |
| TTD (mm) | 227.0 (±10.6) | 235.6(±10.4) | 8.6 (±4.4) |
| RDD (mm) | 35.0(0.0 – 60.0) | ||
| LDD (mm) | 35.0(0.0 – 55.0) | ||
| GWL (mm) | 11.1(4.6 – 20.7) |
[i] ATD = anteroposterior thoracic diameter; GWL = gating-window level; LDD = left diaphragmatic descent; MHD = maximum heart distance; RDD = right diaphragmatic descent; TTD = transverse thoracic diameter; Δ = differences between DIBH and FB
FIGURE 2.
Correlation between ΔMHD and left diaphragmatic descent, right diaphragmatic descent [r: Spearman rank correlation coefficient; p: p-value (2-tailed)].
ΔMHD = maximum heart distance in deep inspiration breath-hold minus maximum heart distance in free breathing
TABLE 2.
Comparison of the mean of parameters in ΔATDlow (n = 46) and ΔATDhigh (n = 52) and in ΔTTDlow (n = 51) and ΔTTDhigh (n = 47)
| LDD | RDD | ΔATD | ΔTTD | ΔMHD | |
|---|---|---|---|---|---|
| ΔATDlow (mm) | 32.2 | 34.0 | 7.7 | 7.5 | −7.0 |
| ΔATDhigh (mm) | 34.2 | 35.4 | 13.8 | 9.6 | −9.5 |
| Increase of ΔATDhigh (mm) | 2.0 | 1.4 | 6.1 | 2.1 | −2.5 |
| Increase of ΔATDhigh (%) | 6.2% | 4.1% | 78.9% | 27.9% | 36.5% |
| ΔTTDlow(mm) | 35.3 | 37.1 | 10.5 | 5.4 | −9.7 |
| ΔTTDhigh (mm) | 31.1 | 32.2 | 11.4 | 12.0 | −6.9 |
| Increase of ΔTTDhigh (mm) | −4.2 | −4.9 | 0.8 | 6.6 | 2.8 |
| Increase of ΔTTDhigh (%) | −12.0% | −13.2% | 7.9% | 122.2% | −29.3% |
[i] ATD = anteroposterior thoracic diameter: ΔATDlow = group with ΔATD < 11 mm; ΔATDhigh = group with ΔATD > =11 mm; ΔTTDlow = group with ΔTTD < 8.6 mm; TTD = transverse thoracic diameter; ΔTTDhigh = group with ΔTTD > = 8.6 mm
TABLE 3.
Correlation between dosimetric parameters and geometric parameters
| ΔDmean | ΔHVIF | ΔV10 | ΔV5 | ||
|---|---|---|---|---|---|
| ΔMHD | r | 0.468 | 0.464 | 0.481 | 0.484 |
| p | < 0.001 | < 0.001 | < 0.001 | < 0.001 | |
| LDD | r | − 0.340 | − 0.365 | − 0.382 | − 0.373 |
| p | = 0.001 | < 0.001 | < 0.001 | < 0.001 | |
| RDD | r | − 0.439 | − 0.449 | − 0.462 | − 0.458 |
| p | < 0.001 | < 0.001 | < 0.001 | < 0.001 | |
| ΔATD | r | 0.007 | 0.044 | 0.026 | 0.008 |
| p | 0.943 | 0.669 | 0.801 | 0.935 | |
| ΔTTD | r | 0.012 | 0.055 | 0.062 | 0.065 |
| P | 0.906 | 0.593 | 0.545 | 0.527 |
[i] ATD = anteroposterior thoracic diameter; Dmean = heart mean dose; HVIF = heart volume in field, that's the heart volume within the 50% isodose line; LDD = left diaphragmatic descent; MHD = maximum heart distance; RDD = right diaphragmatic descent; TTD = transverse thoracic diameter; V5 = percentage volumes of heart receiving doses ≥ 5Gy; V10 = percentage volumes of heart receiving doses ≥ 10 Gy; Δ the value of a parameter in deep inspiration breath holding (DIBH) minus the value of this parameter in free breathing (FB)