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

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.

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

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)

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.

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

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

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

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

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

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.

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.

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

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

Result • SUVmax of Lung 13% n SUV Mean±SD Differnce %Differnce t p HCT 20 5.7±3.4 0.3±0.4 5.6±5.3% -3.472 0.03 ACT 6.0 ±3.5 13%

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

Result • SUVmax of Liver 9% n SUV Mean±SD Differnce %Differnce z p HCT 8 5.6±2.2 0.3±0.3 3.9±3.1% -2.636a 0.08 ACT 5.9±2.5

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

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.

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.

Thank You