1. BMME 560 & BME 590I Medical Imaging: X-ray, CT, and Nuclear Methods Nuclear Medicine Imaging Part 2

2. Today Clinical and research applications –Planar scintigraphy –Cardiac imaging –Cancer imaging –Neurological imaging –Other

3. Planar Scintigraphy Basically, this is SPECT without the CT part. Take one or two views of the emission data and base the diagnosis on that Like projection radiography vs. X-ray CT For focal areas, use pinhole

4. Thyroid Scan A common procedure is to study the function of the thyroid gland Use a pinhole collimator to get magnification and focus on the organ. IsotopeHalf-lifeEnergy 123 I13 hours159 keV 131 I8 days356 keV 99m TcO 4 (pertechnetate) 6 hours140 keV High-energy, betas Expensive, 4-24 hours distribution Less efficient uptake, cheap, 15- 30 min distn

5. Thyroid Scan Studies regional function of thyroid via its uptake Hyperthyroidism, hypothyroidism, benign masses vs. cancers Cold nodule Source: http://www.uhrad.com/spectarc/nucs022.htm

6. Bone Scan 99mTc-MDP is incorporated into extracellular matrix as new bone is formed Uptake depends on local blood flow and osteoblast activity Used to examine cancer metastasis to bones Also, stress fractures and other bone functional abnormalities Also, functional abnormalities when other tissues act like bone

7. Bone Scans Metastatic involvement Source: http://www.mcg.edu/radscape/CaseStudies/Christy_Barnosky/MetStats.htm

8. Bone Scans Calcified uterine fibroids above the bladder Source: http://www.uhrad.com/spectarc/nucs020.htm Stress fracture of the foot Source: http://www.uhrad.com/spectarc/nucs012.htm

9. SPECT Bone Scan Reference: http://www.uhrad.com/spectarc/nucs010.htm http://www.uhrad.com/spectarc/nucs010.htm

10. Cardiac Functional Imaging All major imaging modalities are working on the heart –CT: Fast multislice cardiac CT –Cardiac MRI –Echocardiography –SPECT: Cardiac perfusion imaging –PET: Cardiac viability and perfusion

11. Cardiac Perfusion Imaging Measurement of blood flow to cardiac tissue via coronary arteries Coronary arteries may be blocked by plaques Stress versus rest studies may reveal a difference SPECT is cheap and has long been used for this purpose –Several agents, mostly 201 Tl (older) and 99m Tc

12. SPECT Cardiac Imaging The left ventricle takes most of the blood flow to the heart. It is shaped like a rounded cone. Dark regions indicate reduced blood flow to a portion of the myocardium

13. SPECT Cardiac Imaging But, reduced blood flow could have more than one reason: –The coronary artery supplying it is partially blocked –The tissue is dead Which is worse? To determine, try imaging at stress and rest

14. Cardiac Imaging If the coronary artery is blocked, the physician must make a treatment decision: –Revascularize (coronary bypass) –Pharmaceuticals This depends on the assessment of the outcome of each procedure –If an expensive procedure (bypass) will help, do it. –Otherwise, don’t Depends on viability: Could the cardiac tissue be restored?

15. PET Cardiac Imaging FDG is a glucose analog; stunned cardiac tissue still uses some glucose. FDG helps determine the viability of tissue: could it be brought back? 13 NH3 and rubidium are PET perfusion agents

16. Cardiac PET 13 N FDG 10 min half-life! Can also use 82 Rb – 6- hour half-life and generator-produced Would you send to bypass? Source: http://www.thompsonpet.com/zportal/portals/phys/clinical/jnmpetlit/index_html/JNM_CardApps

17. Gated Imaging Each event recorded by the detector has a time associated with it. By synchronizing these times with the ECG signal, we can divide the events into different pars of the cardiac cycle A 3D movie of SPECT or PET Assess wall motion as well as perfusion What price do we pay?

18. Gated Imaging Conventional SPECT Gated SPECT Sixteen 3D datasets or one 4D dataset One 3D dataset

19. Gated SPECT

20. Cancer Imaging Cancers may be anatomically similar to the surrounding tissue, but functionally different. Active cancers take up lots of glucose –So do inflammations PET’s first approved clinical application was in the study of lung cancer SPECT is used to image cancers as well

21. PET Cancer Imaging Pre- and post-therapy images of lung cancer and metastases Source: Appl Radiol 31(6):9-17, 2002. © 2002 Anderson Publishing, Ltd.

22. PET Cancer Imaging Source: http://www.bocaradiology.com/Procedures/PET.html Liver, but no mets Diffuse spread of prostate cancer to bone

23. PET Cancer Imaging Whole-body PET is currently approved for: –Non-small-cell lung carcinoma –Head and neck carcinoma –Lymphoma –Melanoma –Colorectal carcinoma –Esophageal carcinoma –Thyroid carcinoma –Solitary pulmonary nodule (lung)

24. SPECT Cancer Imaging 111 In-Prostascint SPECT/CT –Binds to Prostate-specific membrane antigen –FDG PET is not very good for this purpose – Why? Source: http://ieeexplore.ieee.org/iel5/9892/31436/01462741.pdf?arnumber=1462741

25. Neurological Imaging The brain is important, too. Applications include regional cerebral blood flow (SPECT) and brain activation studies (PET)

26. Brain SPECT 99m Tc-HMPAO and 99m Tc-ECD are brain perfusion agents –Cross blood-brain barrier and are then trapped –Highest signal from gray matter – 123 I-IMP behaves similarly Some development of neuroreceptor ligands –For imaging of dementia and other neurological disorders Reference: http://brighamrad.harvard.edu/education/online/BrainSPECT/BrSPECT.htmlhttp://brighamrad.harvard.edu/education/online/BrainSPECT/BrSPECT.html

27. Brain SPECT Ischemic stroke via 99m Tc-HMPAO Source: http://brighamrad.harvard.edu/education/online/BrainSPECT/Contents.html Physicians look for asymmetry

28. PET Neuroimaging Can use FDG Interesting things can be done with other radionuclides – 11 C (20 minutes) is used to label all kinds of organic molecules – 15 O (2 minutes) is incorporated into water Source: http://clinicalcenter.nih.gov/pet/images.html

29. FDG Brain PET Shows brain metabolic activity Gray matter is hot This patient is normal. What would a dark region indicate?

30. 11 C Raclopride This is a dopamine receptor antagonist. The basal ganglia light up.

31. 15 O-water Shows cerebral blood flow, but a little different from SPECT ligands Shows tissue function with respect to water transport – does not get trapped in tissue Noisy 2 minute half-life!

32. PET Neuroimaging Abnormally low activity in right temporal lobe in epileptic patient Source: http://www.bocaradiology.com/Procedures/PET.html

33. FDG and C-11 FDG C-11 methionine Patient imaged post-radiation therapy for brain tumor. FDG shows suspicious region, but C-11 is more specific Source: http://www.med.harvard.edu/JPNM/TF00_01/Sept26/WriteUp.html

34. White blood cell SPECT Tried-and-true method: Extract patient’s blood sample, isolate leukocytes, label with 111 In, and reinject –Can also use 99m Tc Newer method: “in vivo labeling” of leukocytes with 99m Tc LeukoScan™ Leukocytes collect at sites of infection and inflammation –Used in all parts of the body

35. 111 In WBC SPECT Source: http://www.rad.kumc.edu/nucmed/clinical/wbcscan.htm

36. 67 Ga-citrate Gallium was one of the earliest NM agents It binds to a protein (transferrin) in the circulating blood and follows it to sites of infection Problems with gallium –Messy – 3 energy peaks (93, 185, 300 keV) –Long-lived – 78 hour half-life

37. Ga-67 vs. In-111 Patient has pneumonia – Ga-67 is better for opportunistic infections Source: Journal of Nuclear Medicine Technology Volume 32, Number 2, 2004 47-57

38. SPECT Aerosol Agents 133 Xe and 99m Tc- Technegas are delivered through inhalation Lung ventilation is assessed by gating to respiratory cycle Often compared with lung perfusion via 99m Tc-MAA Source: radchem.nevada.edu/chem312/lectures/chem%20312%20lect%204%20radiotracer.ppt

39. New Things Radiolabeled antibodies Reporter genes –Via NaI symporter (NIS) molecule NIS gene product mediates radioiodine (PET, SPECT) transport into the cell NIS has been sequenced Faster, cheaper labeling methods