Nuclear Medicine Physics Image Artifacts in Nuclear Medicine

Nuclear Medicine Physics Image Artifacts in Nuclear Medicine Jerry Allison, Ph. D. Department of Radiology Medical College of Georgia Augusta University

A note of thanks to Z. J. Cao, Ph. D. Medical College of Georgia And Sameer Tipnis, Ph. D. G. Donald Frey, Ph. D. Medical University of South Carolina for Sharing nuclear medicine presentation content

Artifacts in NM images § Defects of gamma camera or suboptimal data § § acquisition Photon attenuation Compensation of photon attenuation in PET/CT and SPECT/CT Patient motion Undesired uptake of radiopharmaceutical 3

Defects of gamma camera § Defect of collimator or detector § Bad PMT § Shift of energy peak out of energy window § High count rate (> 250, 000 counts/sec) § SPECT artifacts 4

Effect of counts on perceived noise Image of a brain phantom. As counts increase, noise decreases. © 1999 by Radiological Society of North America Rzeszotarski M S Radiographics 1999; 19: 765 -782

Effect of counts on contrast End –diastole image © 1999 by Radiological Society of North America Rzeszotarski M S Radiographics 1999; 19: 765 -782

Small dot: collimator defect 7

One PMT a defective PMT Multiple PMTs offset of energy peak 8

Shift of energy peak 9

A defective PMT in SPECT 10

Line: cracked detector Caused by mechanical impact 11

pulse height High count rate pile-up time 12

High count rate 13

COR shift in SPECT 14

Contamination of the patient's clothing with radioactivity 15

Myocardial perfusion studies Attenuation compensated vs Non-compensated 16

Attenuation by left breast an apparent defect in the anterior wall 17

Attenuation by diaphragm an apparent defect in the inferior wall 18

Cerebral perfusion studies Tc-HMPAO or Tc-ECD Without attenuation correction Correcteded 19

Misalignment in SPECT/CT 20

Misalignment in SPECT/CT 21

Septal Penetration Thyroid scan on a patient imaged with a low energy collimator.

Septal Penetration These 111 In images were obtained simultaneously with a dual head camera, and the collimator for the posterior head had not been changed to a medium energy collimator. Therefore, there is significant septal penetration (typical star pattern). 2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, Ph. D, DABR

A telemetry monitor on patient's chest 24

PET/CT issues § Metallic artifact § Truncated CT § CT contrast § Respiration misalignment § Motion § Brown fat § Scar 25

Attenuation correction in PET § High uptake in lungs § Low uptake in others § High uptake in skin w/o comp 26

2014 PET image of the ACR phantom 7. 9 mm 27

2014 SPECT image of the ACR phantom • as 9. 5 mm 31. 8 mm 15. 9 mm 28 Sphere diameters: 9. 5, 12. 7, 15. 9, 19. 1, 25. 4, and 31. 8 mm

Metallic implant PET comp PET w/o CT 29

Truncated CT PET comp CT 30

Truncated CT SUV=1. 96 Corrected SUV=7. 44 31

CT contrast CT PET comp PET w/o 32

Respiration misalignment in PET/CT PET comp 33

Respiration misalignment in PET/CT PET comp PET w/o 34

Head motion in PET Corrected 35

Head motion increased uptake in right face as compared with the left side 36

Brown fat uptake of 18 F-FDG keep patient warm 37

Question PET comp Pace maker PET w/o CT 38

Question CT truncation SUV=0. 32 Corrected SUV=0. 79 39

Question PET comp Metallic implant PET w/o CT 40

Question Scar uptake of 18 F-FDG PET comp 41

Time of flight PET image of a big patient Why better resolution? Less noise lighter filtering more resolution preserved (electronic collimation)