1. Nuclear Medicine -How does it work
Gerald R. Aben, MD FACR
Department of Radiology
College of Osteopathic Medicine
In this presentation we are going to look at how nuclear medicine and radioisotopes can be used in the clinical situation.
9/17/2018
DEPARTMENT OF RADIOLOGY

2. DEPARTMENT OF RADIOLOGY
Nuclear Medicine
In this next segment, we will be discussing basic principle of nuclear medicine imaging.
9/17/2018
DEPARTMENT OF RADIOLOGY

3. Nuclear Medicine Physiological Imaging
Radioactive isotopes which emit gamma rays or other ionizing forms (half life for most is hours to days)
Radionuclides are injected intravenously or inhaled where, depending on substance, they concentrate in organ of study
The emitted gamma rays are then picked up by gamma camera and displayed
Special terms used on nuclear medicine reports
Hot, Photon Rich, Cold, Photon Poor, Photopenic
Nuclear imaging is a form of physiologic imaging. In order to produce images of physiologic processes, we utilize radioactive isotopes, which typically emit gamma rays or another type of ionizing radiation that can be detected. These isotopes have half-lives, in the most part that last hours and in a few occasions, may last days. The radionuclides are either injected intravenously or they are inhaled where, depending upon the carrier substance, they concentrate in an organ of interest. Emitted gamma rays are detected by a gamma camera or other detector device, and are then displayed on a cathode ray tube or a screen. Special terms are used on nuclear medicine reports, including terms such as hot, or photon rich, cold, or photon poor, or sometimes referred to as photon photopenic.
9/17/2018
DEPARTMENT OF RADIOLOGY

4. Nuclear Medicine Physiological Imaging
Conventional Nuclear Medicine
Emitted gamma rays create image
SPECT (Single Photon Emission Computed Tomography)
Tomographic images of emitted gamma rays
Rotating gamma camera creates 3-D data set
Data set is then manipulated to create volume images (sum of all images in stack), multiplanar thin section images and 3-D volume data sets
Convention nuclear medicine utilizes gamma rays to create the image. These gamma rays are of such an energy level that they can be easily detected by a gamma camera. SPECT imaging, single-photon emission computed tomography, is a variation of the conventional nuclear medicine where, by rotating a gamma camera around the patient or the object of interest, we’re able to create a 3-dimensional array of data demonstrating the location of the gamma ray emissions within the body or body part. These tomographic images are then utilized as part of the diagnostic process. With these volume data sets we are able to create volume images with all images in a stack or we are able to create multi-planar thin images, and even 3-D volume data sets that can be rotated or evaluated in various imaging techniques.
9/17/2018
DEPARTMENT OF RADIOLOGY

5. DEPARTMENT OF RADIOLOGY
Gamma Camera
This is a picture of the gamma camera here at Michigan State University. In our installation, this is what is called a two-headed camera. There are actually two gamma cameras attached to single yoke, which allows imaging from two dimensions simultaneously. This particular device has been optimized for evaluation of cardiac imaging.
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DEPARTMENT OF RADIOLOGY

6. DEPARTMENT OF RADIOLOGY
Bone Scan
This is the typical appearance of a bone scan obtained by planar imaging over the anterior portion or posterior portion of the body, following the administration of technetium tagged to a diphosphonate. This allows evaluation of areas of active bone growth, some excretion by the kidney accounts for the activity seen within the kidneys and within the bladder as well. I am uncertain as to the cause of the increased uptake identified in the skull. This could be related to metastatic lesion.
9/17/2018
DEPARTMENT OF RADIOLOGY

7. DEPARTMENT OF RADIOLOGY
Lung Scan
This slide demonstrates the appearance of the Lungs, as obtained by the lung ventilation perfusion scan, ventilation on your left, perfusion on your right. The ventilation scan consists of the patient inhaling either a gas, xenon-133 or a particulate of technetium, which is aerosolized and distributes throughout the ventilated portions of lungs. On the initial breath and equilibrium phase, areas which do not demonstrate distribution of radionuclide would be areas that are not aerated, perhaps areas of atelectasis or areas of air shunting because of underlying vascular problems. The washout phase allows us to determine that there is an even and equal washout from all lobes of the lung and all segments of the lung. Any evidence for air trapping would suggest the possibility of emphysema. The panel to our right consisting of 4 images is following the intravenous injection of the technetium labeled macro aggregated albumin. This particle size is optimized to be trapped within the capillaries of the lung. Several hundred thousand small micro-emboli distribute evenly throughout the perfused portions of the lung. We’re able to identify any areas of poor perfusion or areas of occlusion because of a clot or thrombus as areas of non-perfusion, so absence of perfusion in an area. Typically, images are obtained both anteriorly and posteriorly, as well several oblique views used to allow adequate evaluation of all the segments of a lung.
Ventilation
Perfusion
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DEPARTMENT OF RADIOLOGY

8. DEPARTMENT OF RADIOLOGY
HIDA Scan
Another area that can be evaluated using radionuclide techniques is a the hepatobiliary tree. Using an ida compound, it is possible to visualize the pathways of bile through the hepatocytes on into the gastrointestinal tract. The administered radioisotope tracer rapidly appears within the liver parenchyma, representing the appearance within the hepatocytes, it subsequently can be identified in the common duct extending into the gallbladder if the cystic duct is patent, and also traversing into the small intestine, if there is patency of the common duct. Additionally, cholecystokinin, or a fatty meal, can be administered in order to cause gallbladder contraction and an evaluation of the percentage of evacuation of the gallbladder can be determined using this technology. Arrows here, demonstrating the appearance of normal structures on the HIDA scan.
Common
Duct
Gallbladder
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DEPARTMENT OF RADIOLOGY

9. DEPARTMENT OF RADIOLOGY
CT- PET
PET
Scan
Section CT
Scan
Section
I’d like to spend the rest of the time talking a little bit about CT PET evaluation. We’ve talked about CT scanning, and the technology of CT scanning in other presentations. PET scanning technology was developed approximately at the same time as CT scanning technology, but was hampered until recent years by the inability to place accurately the PET information upon a cross-sectional image or other image in order to allow precise localization of areas of abnormal activity. In today’s scanners, the CT scanner is located in front of the gantry and a PET scanner has been tacked onto the back of the gantry, allowing a careful and precise coordination of locations in the body, both on PET and CT scanning.
9/17/2018
DEPARTMENT OF RADIOLOGY

10. DEPARTMENT OF RADIOLOGY
PET Scanning
Oncology
Function
Metabolism
Perfusion
The applications for PET scanning is primarily oncologic evaluation of various types of neoplasm. There are, however, some functional applications of PET scanning as well as evaluation of metabolic processes. PET scanning can be utilized for evaluation perfusion of the heart, as well.
9/17/2018
DEPARTMENT OF RADIOLOGY

11. Positron Emission Tomography
PET (Positron Emission Tomography)
Tomographic images of emitted positrons
Can be used to study metabolic processes
511 kEv gamma ray Photons emitted simultaneously at 180 degrees to each other
Evaluate location in space
Fusion imaging with CT scanning for precise localization
Positron emission tomography, or PET scanning, allows for the obtaining of tomographic images of the interactions between positrons and electrons. This interaction can be used to study metabolic processes. When a positron interacts with an electron, there is a decay that takes place, and an annihilation that results in the ejection of two 511 KEV gamma rays. These photons are emitted and relatively simultaneously approximately 180 degrees to each other. We are able to evaluate the location of these interactions in space and project this information into the creation of images. By fusing the images obtained in the PET scanner with those obtained simultaneously or sequentially with the CT scanner this allows us to create precise localization of areas of abnormality.
9/17/2018
DEPARTMENT OF RADIOLOGY

12. Nuclear Medicine Physiological Imaging
Positron Emission Tomography
Radionuclide emits positrons which interact with electrons to eject gamma rays at 180°
Use computer to localize in space
Gamma ray
Let me try to show you diagrammatically, this process of positron emission tomography. Remember that our radionuclide’s going to emit a positron, which is going to be blue in our case, and this is going to interact with the electron, yellow, to eject gamma rays at approximately 180 degrees to each other. Our positron emitting element, in this particular case, is red. We’re going to utilize a computer to localize this interaction in space based on the coincidence of two photons of gamma rays being detected simultaneously. The positron strikes the electron creating two green gamma rays in this demonstration. Β+ E-
Positron
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DEPARTMENT OF RADIOLOGY

13. Positron Emission Tomography
Lung Cancer
Mediastinal Metastasis
Subsequent to the detection of this activity, we’re able to project these in various formats. This particular format’s called a maximum intensity projection. This can be rotated around the central axis of the body and allow us to locate areas of abnormal activity in space. Note in this case, the presence of a lung cancer in the left lung, as well as at least two foci of abnormal activity in the mediastinum, indicating mediastinal metastases.
9/17/2018
DEPARTMENT OF RADIOLOGY

14. Positron Emission Tomography
Lung Cancer
Metastases
Obstructed right ureter
In another case, we note a very large mass in the left lung, and we also note other areas of abnormal activity in the chest, representing metastatic disease. Incidentally, an obstructed right ureter was also noted on this examination. On occasion, unsuspected colon cancers have also been detected in utilizing PET scanning for evaluation of other neoplasms.
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DEPARTMENT OF RADIOLOGY

15. Normal Cardiac Perfusion
Perfusion evaluation can be performed. In this case, much like other types of nuclear medicine cardiac evaluation, images are presented showing cross-sectional images through the heart in a tomographic fashion. In this case, the radioisotope utilized was radioactive ammonia, a short half-life positron emitting isotope. This particular technique would require the presence of a cyclotron within the facility.
9/17/2018
DEPARTMENT OF RADIOLOGY

16. Anterior Wall Ischemia
In another patient, we see multiple rows of information. We’ll talk more about these in our lecture on aging, but this demonstrates an area of abnormality, including anterior wall ischemia, a zone of decreased radionuclide uptake, decreased orange coloration on the stress images, which, on the parallel row of rest images demonstrates redistribution of radionuclide indicating an area of stress-induced ischemia.
9/17/2018
DEPARTMENT OF RADIOLOGY

17. Anterior Wall Ischemia
Computer presentations can be utilized to assist in this diagnosis. This “bull’s-eye” type presentation with the cardiac apex centrally and the base of the heart being to the periphery allows us to accurately evaluate and compare the distribution of radionuclide to a group of known normal cardiac scans. This particular technology and technique developed at Emory University in Atlanta, Georgia.
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DEPARTMENT OF RADIOLOGY

18. DEPARTMENT OF RADIOLOGY
13N-Ammonia and 18F-FDG PET-perfusion and viability
And finally, we have the ability, by utilizing a perfusion technique with ammonia, and a metabolic technique, 18- fluorodeoxyglucose(18F FDG), we’re able to identify areas of ischemia that actually do have some metabolic activity. This indicates viability of areas of ischemic myocardium or apparent scarred myocardium that may be assisted in returning to normal cardiac motility if vascularity is returned. This has been a brief review of the application and function of PET imaging. I hope that you have found this valuable.
perfusion
viability
9/17/2018
DEPARTMENT OF RADIOLOGY