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Identifying Image Artifacts, Their Causes and How to Fix Them: PET Brad J Kemp, PhD Mayo Clinic, Rochester, MN

Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

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Page 1: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

Identifying Image Artifacts, Their Causes and How to Fix Them: PETBrad J Kemp, PhDMayo Clinic, Rochester, MN

Page 2: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 1

2

Can we scan with a defective block detector?

Daily Quality Assurance Results

Singles

Coincidence

Timing

Energy

Page 3: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 1

Uniform phantom of F-18 in water

3

Current Day Defective Block

non-TOF

TOF

Previous Day System Okay

Page 4: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 1

Uniform phantom of F-18 in water

3

Current Day Defective Block

SUV: TOFSUV:non-TOF

non-TOF

TOF

Previous Day System Okay

Page 5: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 1

Uniform phantom of F-18 in water

3

Current Day Defective Block

SUV: TOFSUV:non-TOF

non-TOF

TOF

Previous Day System Okay

Discussion:• Artifacts will depend on • whether system is PET-only or hybrid • number of blocks and their location within scanner • activity distribution within the object

• SUVs will be affected

Page 6: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 2

4

Description:• Streaks throughout reconstructed PET images

N-13 ammonia cardiac PET study

Transaxial image Coronal image

Page 7: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 2

5

Cause:• Failure of two modules (16 block detectors) during the day

Resolution:• Reboot system • Replace hardware

Singles

Coincidence

Timing

Transaxial imageDaily Quality Assurance Results (mid-day)

Page 8: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 3

Description:• Streaks in coronal PET images • Large photopenic areas with no apparent uptake

6

CT PET/CT Fused PET with CTAC

Page 9: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 3

7

PET with CTACPET/CT Fused

Page 10: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 3

7

PET with CTAC PET NACPET/CT Fused

Page 11: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 3

Cause:• Patient motion between CT and PET scans • Activity appears to be outside the body • Overcorrection of scatter • There will be errors in attenuation correction too

7

PET with CTAC PET NACPET/CT Fused

Page 12: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 3

Cause:• Patient motion between CT and PET scans • Activity appears to be outside the body • Overcorrection of scatter • There will be errors in attenuation correction too

7

PET with CTAC

Resolution:• Do not apply scatter correction • Limit the scatter correction

PET with CTACNo scatter correction

PET with CTACLimit scatter correction

PET NACPET/CT Fused

Page 13: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

Description:• Photopenic areas over diaphragm and dome of liver

WE-G-209-3 Artifacts: PET

Case 4

8

CT PET with CTACCT

Page 14: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 4

9

CT PET with CTAC

Page 15: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 4

9

CT PET with CTAC PET NAC

Page 16: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 4

9

CT PET with CTAC PET with CTACTOF

PET NAC

Page 17: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 4

9

Resolution:• Breathing techniques • Respiratory gated PET and CT • Apply TOF

Cause:• Respiratory motion • Misregistration of PET and CT at

the diaphragm • Undercorrection of attenuation

CT PET with CTAC PET with CTACTOF

PET NAC

Page 18: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 5

10

Description:• Reduced blood flow in anterior region of an N-13 ammonia myocardial blood flow study

SA slices: Apex to base

Polar Map

Page 19: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

Resolution:• Re-align CT AC images onto PET images • Re-reconstruct PET data with re-aligned CT AC images • Limitations: Rigid body realignment with translations only • Apply TOF

WE-G-209-3 Artifacts: PET

Case 5

11

SA slices: Apex to base

Polar Map

Cause:• Respiratory motion • Misregistration of the myocardium

in PET and CT • Undercorrection of attenuation

Original Images Corrected Images

Page 20: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Patient moves between CT and PET

Case 5

12

Z-scores, compared with normals databaseOriginal images

Corrected images (re-aligned, re-reconstructed with proper attenuation correction) Z-scores, compared with normals database

Page 21: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 6

13

Description:• Increased uptake in abdomen

CT PET/CT Fused PET with CTAC

Page 22: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 6

14

CT PET with CTAC

Page 23: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 6

14

CT PET with CTAC PET NAC

Page 24: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Case 6

14

CT PET with CTAC PET NAC

Resolution:• Apply bilinear HU ➛ 𝜇 conversion

with contrast correction

Cause:• Overcorrection of attenuation due

to presence of contrast

PET with CTACContrast Correction

Page 25: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

Recommendations

If artifacts are present:

• Investigate the PET data• Review sinograms • Review PET NAC

• Investigate the attenuation correction data• Review AC maps (especially for PET/MR studies) • Are PET and AC maps registered? • Is contrast media, metal, truncation present?

To reduce artifacts:• better algorithms • reduce patient motion • use TOF whenever possible

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Page 26: Identifying Image Artifacts, Their Causes and How to Fix ...amos3.aapm.org/abstracts/pdf/115-31944-387514-119635.pdf · WE-G-209-3 Artifacts: PET Case 3 Cause: • Patient motion

WE-G-209-3 Artifacts: PET

References

• Elhami E, Samiee M, et al. On the significance of defective block detectors in clinical 18F-FDG PET/CT. Mol Imaging Biol 2011;13:265-274.

• Gould KL, Pan T, et al. Frequent diagnostic errors in cardiac PET/CT due to misregistration of CT attenuation and emission PET images: a definitive analysis of causes, consequences and corrections. J Nucl Med 2007; 48:1112-1121.

• Lodge MA, Mhlanga JC, Wahl RL. Effect of patient arm motion in whole-body PET/CT. J Nucl Med 2011;52:464P.

• Sureshbabu W, Mawlawi O. PET/CT imaging artifacts. J Nucl Med Tech 2005;33:156-161.

• Surti S. Update on time-of-flight PET imaging. J Nucl Med 2015;56:96-105.

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