1. Evaluation of Average CT to reduce the artifact in PET/CT
Department of Nuclear Medicine Asan Medical Center
Kim Jung Sun

2. Introduction
PET shows accuracy in staging, restaging of cancer and assessment of treatment response.
To predict treatment response, SUV have been used in cancer.
Respiratory motion often hampers SUV in FDG PET/CT images.
Respiratory motion
often makes artifacts
of PET/CT image.

3. Introduction Artifact is due to discrepancy of the diaphragm position.
Because of different scan time.
CT scan takes a few seconds, but PET scan takes 3~5min per bed.
Breathing Cycle
PET Scan
CT scan

4. To reduce respiration artifact
Introduction
To reduce respiration artifact
Equipments
Methods
- Pressure Sensor
- Spirometer
- Temperature Sensor
- RPM Respiratory Gating System
-Deep-Inspiration BH PET/CT
-Attenuation correction with average CT(ACT)

5. Cine CT Introduction Average CT
AC of PET data with ACT has been proposed for improving the artifact by Tinsu Pan.
Cine CT
Average CT
Improved artifact
average
Attenuation
Correction
Cine CT acquires multiple CT images in on breathing cycle.

6. Introduction
Cine CT
AC MAP
average
ACT
HCT
*Helical CT( HCT)

7. To evaluate usefulness of ACT
Introduction
• Purpose
To evaluate usefulness of ACT
for AC of PET data

8. Object Materials and Methods Equipments Analysis Software
Whole Body PET/CT 13 Patients
Mean Age=61.6
9 Lung cancer(20 tumors),4 Liver cancer(8 tumors)
Object
Equipments
Discovery STe8, GE helthcare
Workstation V4.3 Volume viewer
,GE helthcare
Analysis Software

9. Materials and Methods • Acquisition Procedure ACT Scan CT Scan
Toposcan
CT Scan
120kV, auto mA
ACT Scan
(Lower thorax)
120kV,10mA
2cm/5.9s Cine duration
PET Scan
3min/bed

10. Materials and Methods • Measurement of the artifact
Measured the highest magnitude of artifact slice by slice with coronal images.

11. Materials and Methods • Measurement of SUVmax ACT HCT
Measured max SUV of primary tumors.
ROIs were set to include tumor using 3D box tool with coronal and axial image.
Measured maximum SUV of primary tumors.
ROIs were set to include tumor using 3D box with coronal and axial image.

12. Materials and Methods • Statistical analysis paired t-test and
Wilcoxon rank sum test
SPSS v12.0
Attenuation Correction
With HCT
Attenuation Correction
With ACT
p values <0.05 were considered statistically significant.

13. Result • Frequency of artifact • Magnitude of artifact HCT ACT 2 / 13
8 / 13
2 / 13
HCT
ACT
• Magnitude of artifact

14. Result • Example of breathing artifact HCT ACT
Breathing artifact was removed in AC with ACT image.

15. Result • SUVmax of Lung 13% n SUV Mean±SD Differnce %Differnce t p HCT20
5.7±3.4
0.3±0.4
5.6±5.3%
-3.472
0.03
ACT
6.0 ±3.5
13%

16. Result • SUVmax of Middle Lung • SUVmax of Lower Lung n SUV Mean±SD
Differnce
%Differnce z p
HCT 9
5.2±2.8
0.2±0.4
4.6±6.6%
-1.005a
0.315
ACT
5.4±3.0
• SUVmax of Lower Lung n
SUV
Mean±SD
Differnce
%Differnce t p
HCT 11
6.1±3.8
0.3±0.3
6.4±4.0%
-3.472
0.03
ACT
6.5±3.8

17. Result • SUVmax of Liver 9% n SUV Mean±SD Differnce %Differnce z p HCT8
5.6±2.2
0.3±0.3
3.9±3.1%
-2.636a
0.08
ACT
5.9±2.5

18. Result • SUVmean of Background n SUV Mean±SD Differnce %Differnce t p
HCT 13
1.1±0.2
0.0±0.0
-0.4±4.7%
0.562
0.584
ACT

19. Limitation
• We could not control patient breath regularly during the scan.
- It could have probability that affect to comparison of artifact and SUV.
• Limited number of patients(n=13).
• Artifacts caused by overcorrection was not included.
- We suspected one case to be a artifact caused by overcorrection. But we couldn’t decide artifact.

20. Conclusion If consider additional dose (7~8% of FDG PET/CT dose)
The artifacts were significantly reduced in ACT.
Accordingly these tumor were closer to diaphragm
and had a probability of being corrected by ACT.
Tumors located in Lower Lung and Liver showed
increase in maxSUV.
If consider additional dose (7~8% of FDG PET/CT dose)
ACT may useful in treatment planning and
monitoring treatment response.

21. Thank You