Table 1. Contrast injection protocols.
Injection Protocols
(N = Number of swine)
|
Iodine dose per body weight
(ml/kg)
|
Saline Flush
(ml/kg)
|
Injection rate
(ml/s)
|
Protocol A (N = 20)
|
1
|
0.5
|
5
|
Protocol B (N = 10)
|
0.5
|
0.25
|
5
|
Protocol C (N = 5)
|
0.5
|
0.25
|
10
|
Protocol D (N = 5)
|
0.25
|
0.125
|
10
|
Table 2. Simulated Prospective Acquisition Time versus Optimal Acquisition Time
Triggering Offsets (HU)
|
V1
|
V2
|
Time Difference (s)
|
RMSE
|
P-value
|
Time Difference (s)
|
RMSE
|
P-value
|
40
|
0.61 ± 0.61
|
0.86
|
<0.05
|
-0.61 ± 0.98
|
1.16
|
<0.05
|
60
|
0.87 ± 0.66
|
1.03
|
<0.05
|
-0.34 ± 0.96
|
1.02
|
<0.05
|
80
|
1.05 ± 0.66
|
1.24
|
<0.05
|
-0.17 ± 0.90
|
0.91
|
0.252
|
100
|
1.20 ± 0.69
|
1.37
|
<0.05
|
-0.03 ± 0.85
|
0.85
|
0.921
|
120
|
1.38 ± 0.72
|
1.56
|
<0.05
|
0.16 ± 0.83
|
0.84
|
0.056
|
140
|
1.53 ± 0.77
|
1.70
|
<0.05
|
0.31 ± 0.82
|
0.88
|
<0.05
|
Note-: The “Time Difference” shows the time difference between each bolus-tracking simulation and the optimal acquisition timing. The optimal acquisition timing is obtained from the gamma variate fitting AIF curve, where V1 at the second derivative peak of AIF and V2 at the AIF peak. RMSE: Root mean square error.
Table 3. Simulated Prospective Enhancement versus Optimal Enhancement in the Pulmonary Artery
Triggering Offsets (HU)
|
CV1
|
CV2
|
CV2 – CV1
|
Enhancement (HU)
|
RMSE
|
Enhancement (HU)
|
RMSE
|
Difference (∆HU)
|
Optimal
|
228.8 ± 92.5
|
/
|
963.1 ± 294.4
|
/
|
735.1 ± 240.0
|
40
|
340.1 ± 151.9
|
161.0
|
923.1 ± 302.8
|
77.8
|
583.0 ± 295.5
|
60
|
389.1 ± 173.4
|
214.9
|
914.6 ± 311.2
|
96.4
|
525.6 ± 337.8
|
80
|
422. 5 ± 172.4
|
237.7
|
915.3 ± 316.2
|
97.8
|
493.6 ± 332.9
|
100
|
446.3 ± 183.2
|
255.9
|
914.9 ± 319.9
|
98.3
|
468.4 ± 334.5
|
120
|
486. 3 ±187.4
|
300.0
|
900.0 ± 332.5
|
122.3
|
413.5 ± 357.5
|
140
|
514. 5 ± 190.5
|
325.3
|
891.4 ± 330.5
|
134.6
|
377.3 ± 364.0
|
Note-: The "Optimal Enhancement” in the pulmonary artery is the simulated result from the gamma variate fitting curve. Specifically, CV1 was calculated as the average enhancement within the PA region at the time of the second derivative peak, CV2 was the average enhancement within the PA region at the time of peak enhancement. The root-mean-square-error (RMSE) between each triggering protocol and the ideal enhancement was also calculated.
The change in contrast enhancements (∆HU) between CV1 and CV2 is shown in the last column. P-values in all comparisons are less than 0.001. Blood flow is measured based on ∆HU. Therefore, it is best for CV1 to be as low as possible and CV2 to be as high as possible.
Table 4. Regression of Simulated Two-Volume Prospective FPA Perfusion versus Retrospective FPA Perfusion
Segments (n)
|
Slope
|
Intercept
|
Pearson r
|
CCC
|
RMSE
(ml/min/g)
|
RMSD
(ml/min/g)
|
P-value
|
All (540)
|
0.87
(0.83, 0.90)
|
0.56
(0.18, 0.93)
|
0.88
(0.85, 0.89)
|
0.87
(0.85, 0.89)
|
2.29
|
0.85
|
<0.001
|
R_Cranial (60)
|
0.82
(0.66, 0.98)
|
1.13
(-0.42, 2.68)
|
0.81
(0.77, 0.83)
|
0.80
(0.77, 0.83)
|
2.23
|
0.83
|
0.051
|
R_Middle (60)
|
0.77
(0.62, 0.93)
|
0.91
(-0.26, 2.07)
|
0.80
(0.77, 0.83)
|
0.78
(0.75, 0.81)
|
2.19
|
0.90
|
0.019
|
R_Caudal (120)
|
0.91
(0.91, 1.00)
|
0.49
(-0.69, 1.66)
|
0.86
(0.83, 0.88)
|
0.85
(0.82, 0.87)
|
2.56
|
0.68
|
0.022
|
AL (60)
|
0.69
(0.53, 0.84)
|
1.90
(0.65, 3.16)
|
0.76
(0.72, 0.79)
|
0.74
(0.71, 0.78)
|
2.20
|
1.09
|
0.150
|
L_Cranial (60)
|
0.84
(0.69, 0.99)
|
0.87
(-0.69, 2.42)
|
0.82
(0.81, 0.86)
|
0.81
(0.78, 0.84)
|
1.87
|
0.85
|
0.036
|
L_Lingula (60)
|
0.80
(0.66, 0.93)
|
0.63
(-0.37, 1.64)
|
0.82
(0.79, 0.85)
|
0.81
(0.78, 0.84)
|
1.87
|
1.00
|
0.001
|
L_Caudal (120)
|
0.84
(0.77, 0.91)
|
0.50
(-0.10, 1.08)
|
0.92
(0.90, 0.93)
|
0.91
(0.89, 0.92)
|
2.31
|
1.08
|
0.003
|
Note.—Data in parentheses are 95% confidence intervals. P-value less than 0.05 indicate significant difference. CCC: concordance correlation coefficient, RMSD: root-mean-square deviation, RMSE: root-mean-square error.
AL: Accessory Lobe, R: right lung, L: left lung.