Keywords:
Calcifications / Calculi, Radiation safety, Image manipulation / Reconstruction, CT, Radioprotection / Radiation dose, Computer applications, Arteries / Aorta
Authors:
R. W. van Hamersvelt1, A. M. den Harder1, M. J. Willemink1, A. Schilham1, J. W. J. Lammers1, H. Nathoe1, R. P. J. Budde2, T. Leiner1, P. A. de Jong1; 1Utrecht/NL, 2Rotterdam/NL
Results
In total 48 patients (31 males; 60±8.8 years; BMI 28.4±5.1 kg/m2) were included.
The amount of dose per protocol is depicted in table 1.
AVC was present in 14 (29%) and TAC in 17 (57%) patients.
The amount of false postive and negative and number of diagnostic scans (subjective score ≥2) are shown in Fig. 2 for cardiac and Fig. 3 for chest CT. Median mass scores for AVC and TAC at the reference scan were 12.0(1.4-24.0) and 2.7(1.1-15.8) at cardiac CT and 17.0(4.9-50.2) and 455.6(132.6-1796.9) at chest CT.
At 40/45 and 60% reduced dose,
overall median calcification mass scores were underestimated compared to scores at routine dose FBP and decreased with increase in IR.
At maximum reduced dose median calcification mass scores were overall overestimated at FBP and decreased to underestimation with increase in IR,
except for TAC at chest CT (e.g. Fig. 4).
For patients with non-zero calcifications,
median absolute mass deviation from the mass score measured at the reference scan were calculated (Fig. 5).
At 60% reduced dose cardiac CT (0.3 mSv),
all iDose4 scans were diagnostic (Fig. 2) and no significant differences compared to the reference scan were found.
At 75% reduced dose chest CT (0.5 mSv),
similar results were found for IMR levels 1 and 2 and iDose4 levels 4 and 6 (Fig. 3).
Table 1.
Dose characteristics
Scan protocol |
Dose |
CTDIvol |
DLP |
mSv |
Cardiac CT |
Routine |
4.6±0.4 |
59.5±5.6 |
0.9±0.1 |
|
40% reduced |
2.8±0.2 |
35.8±3.4 |
0.5±0.0 |
|
60% reduced |
1.8±0.2 |
23.9±2.3 |
0.3±0.0 |
|
80% reduced |
0.9±0.1 |
11.9±1.1 |
0.2±0.0
|
Chest CT |
Routine |
3.3±0.8 |
133.7±36.3 |
1.9±0.5 |
|
45% reduced |
1.8±0.5 |
73.5±20.0 |
1.1±0.3 |
|
60% reduced |
1.3±0.3 |
53.3±14.5 |
0.8±0.2 |
|
75% reduced |
0.8±0.2 |
33.5±9.2 |
0.5±0.1 |