GE Medical Systems
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  1. 1. GE Medical Systems Healthcare Services GEMS 1877 © 2001 General Electric Company. All rights reserved. TiP-TVGE Training in Partnership Television ™ Program SupplementProgram SupplementProgram SupplementProgram Supplement NM: Brain ImagingNM: Brain ImagingNM: Brain ImagingNM: Brain Imaging
  2. 2. 2 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 TABLE OF CONTENTS PREFACE Table of Contents.............................................................................................................................. 2 Presenter Biographies....................................................................................................................... 3 Program Objectives, Target Audience, and Productivity Statement ...................................................... 5 Continuing Education Credit Eligibility ............................................................................................... 5 INTRODUCTION ..................................................................................................................................................6 BRAIN ANATOMY ................................................................................................................................................7 Cerebrum........................................................................................................................................................7 Brain Stem....................................................................................................................................................11 Cerebellum ...................................................................................................................................................12 Blood Supply ................................................................................................................................................13 Blood-Brain Barrier.......................................................................................................................................14 PLANAR BRAIN IMAGING .................................................................................................................................15 Indications ....................................................................................................................................................15 Imaging Agents.............................................................................................................................................15 Acquisition Guidelines ..................................................................................................................................16 Brain Death Exam ........................................................................................................................................16 SPECT BRAIN IMAGING ...................................................................................................................................18 Indications ....................................................................................................................................................18 Imaging Agents.............................................................................................................................................18 Pharmacologic Intervention ..........................................................................................................................20 Acquisition Guidelines ..................................................................................................................................21 Transient Ischemic Attacks...........................................................................................................................22 NEURORECEPTOR IMAGING...........................................................................................................................23 CISTERNOGRAPHY ..........................................................................................................................................25 Indications ....................................................................................................................................................25 Imaging Agents.............................................................................................................................................25 Acquisition Guidelines ..................................................................................................................................25 CSF Leak......................................................................................................................................................26
  3. 3. 3 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 PRESENTER BIOGRAPHIES Laura L. Edwards, B.S., CNMT Laura holds a Bachelor of Science degree in Management and Computer Information Systems, as well as an Associates of Arts degree in Accounting from Robert Morris College in Pittsburgh, Pennsylvania. She completed her Nuclear Medicine training at Community College of Allegheny College, also in Pittsburgh. Prior to joining GE Medical Systems, she was a staff technologist at The Medical Center in Beaver, Pennsylvania. Laura is a certified Nuclear Medicine Technologist and has nine years of experience in nuclear medicine. She worked at GE Medical Systems as a Nuclear Applications Specialist for the east coast for several years. Jean A. Schmitz, BS, CNMT – GE Medical Systems eLead System Designer, Learning Solutions Jean holds a Bachelor of Science degree in Nuclear Medicine Technology with a Chemistry minor from the University of Wisconsin - LaCrosse. She worked as a staff nuclear medicine technologist and clinical instructor at St. Joseph’s Hospital/Marshfield Clinic in Marshfield, Wisconsin for five years. Jean joined GE Medical Systems in 1988 and was responsible for training applications personnel world-wide, and assisted in product development and validation. She has developed various customer training programs, including technologist training seminars, videotapes, customer reference guides, broadcasts, etc. Jean was a member of the team that developed and implemented the TiP, Training in Partnership, education program platform. As Nuclear and Mammography TiP-TV Program Manager, Jean was responsible for coordinating, developing and presenting training programs to nuclear medicine and mammography personnel via the TiP-TV satellite network. Currently, she is responsible for designing multi-modality and electronic training programs for GEMS Learning Solutions. Lisa K. Armstrong, BS, CNMT – GE Medical Systems Program Manager, PET/NM Clinical Learning Lisa received a Bachelor of Science degree in Allied Health from Oregon Institute of Technology. She obtained her certification in Nuclear Medicine in 1982. Before joining GEMS in early 1990, Lisa held positions as the Assistant Technical Director at the University of Utah and as the Chief Technologist at the Salt Lake Clinic. Within GEMS, Lisa has held a variety of positions including Applications Specialist, Sales Specialist, a position in Marketing and recently her current position as the Program Manager for PET/Nuclear Medicine Clinical Learning. In this role, Lisa is responsible for managing clinical learning offerings including web-based products, satellite broadcasts, and CD ROM for the PET/Nuclear Medicine modality.
  4. 4. 4 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 SPECIAL CONTRIBUTORS We extend a special thanks to the following people for their contributions to this program. Masanori Ichise, M.D. Director, Division of Nuclear Medicine University of Toronto Mount Sinai Hospital Toronto, Ontario, Canada Michael A. Wilson, M.D., F.R.A.C.P. Chief of Nuclear Medicine University Hospital and Clinics Madison, Wisconsin Scott Perlman, M.D. Director of PET Imaging University of Wisconsin PET Imaging Center Madison, Wisconsin Ronald S. Tikofsky, Ph.D. Associate Research Scientist Columbia College of Physicians and Surgeons & Columbia University - Harlem Hospital Center Department of Radiology New York, New York Steven N. Sireci, M.D. Associate Director of Medical Affairs Nycomed Amersham Imaging Princeton, New Jersey Douglass Vines, BSc., CNMT Clinical Coordinator Mount Sinai Hospital Toronto, Ontario, Canada
  5. 5. 5 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 PROGRAM OBJECTIVES, TARGET AUDIENCE, AND PRODUCTIVITY STATEMENT Program Objectives By the end of this program, the viewer should be able to: • Explain the anatomy and basic physiology of the brain. • Discuss the radiopharmaceuticals available for imaging. • Discuss imaging techniques for various neurology procedures. Target Audience Course objectives for this program specifically target nuclear medicine technologists. While not limited to this audience group, the technical content will be most effective when applied to people with this training. NOTE: Viewers who apply for continuing education (CE) credit and meet the application requirements are eligible for credit, regardless of their audience status. Productivity Statement This program was developed to enhance your professional and educational level, and increase your productivity and skills. CONTINUING EDUCATION CREDIT ELIGIBILITY IMPORTANT NOTICE! You may only receive continuing education (CE) credit once for a particular course, regardless of the format in which it was viewed. This GE Medical Systems TiP-TV course may be available in several different formats, such as, but not limited to, an Online Web course or videotape. If you have already applied for and/or received CE credit for this course, you are NOT eligible to receive CE credit for this TiP-TV broadcast. Contact your CE accreditation organization for additional information as needed.
  6. 6. 6 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 INTRODUCTION Brain imaging is a standard procedure that has been performed for several years. During this program we will review the anatomy and physiology of the brain and discuss the various pharmaceuticals available for imaging. A brief update on PET imaging will also be provided during this program.
  7. 7. 7 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 BRAIN ANATOMY • The brain can be divided into three major divisions – Cerebrum – Brain stem – Cerebellum CEREBRUM • The cerebrum is the largest portion of the brain and is considered to be the “top executive” of the body • The cerebrum consists of two hemispheres that are divided by a deep groove called the longitudinal fissure – Tracts of white matter called the corpus callosum connect the hemispheres medially
  8. 8. 8 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 • Fissures subdivide each cerebral hemisphere into four lobes – Fissures are named after the bone that lies over that part of the brain: ! Frontal ! Parietal ! Temporal ! Occipital • There is a fifth lobe that is hidden inside the lateral fissure and can only be seen if the brain is dissected – Insula or island of Reil Frontal lobe Temporal lobe Occipital lobe Parietal lobe
  9. 9. 9 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 • Each hemisphere contains three layers – Cerebral cortex – White matter – Basal ganglia • The outer surface is the cerebral cortex and consists of about 2 to 4 millimeters of gray matter • The next layer is the white matter that makes up the majority of the cerebrum • The third layer consists of islands of internal gray matter called basal ganglia or cerebral nuclei – These basal ganglia are involved in somatic motor functions Cerebral cortex White matter
  10. 10. 10 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 • The central portion of the cerebrum contains four cavities or spaces called ventricles, which are all connected – These ventricles contain the choroid plexus that produces the cerebrospinal fluid (CSF) – CSF is a blood transudate that surrounds and protects the brain and spinal cord • It is important to be familiar with the appearance of the ventricles when you are performing cisternograms • First and second ventricles – Lateral ventricles – There is one located in each hemisphere • Third ventricle – The lateral ventricles are connected to the third ventricle – This ventricle is a narrow chamber located beneath the corpus callosum and the longitudinal fissure • Fourth ventricle – The fourth ventricle is a diamond-shaped space positioned between the cerebellum and the brain stem – It is actually an expansion of the central canal of the spinal cord Lateral ventricle Third ventricle Fourth ventricle
  11. 11. 11 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 BRAIN STEM • The second division of the brain is the brain stem • The brain stem consists of three structures – Midbrain – Pons – Medulla • The brain stem provides the connection between the spinal cord and the brain – This allows messages or information to be passed from the brain to the rest of the body, controlling voluntary and involuntary movements Midbrain Pons Medulla oblongata
  12. 12. 12 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 CEREBELLUM • The cerebellum is the third division and the second largest portion of the brain • It is located just below the posterior aspect of the cerebrum • It is separated from the cerebrum by a deep transverse fissure • This structure is most commonly cut off or positioned outside of the field of view when imaging the brain • The cerebellum is responsible for the proper control of skeletal muscles, providing smooth movements and maintaining posture and equilibrium Cerebelllum
  13. 13. 13 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 BLOOD SUPPLY • When performing cerebral blood flow exams, it is important to understand the major blood supply to the brain • The brain receives about 20 percent of the cardiac output (1 liter/minute) via the right and left common carotid and vertebrobasilar artery systems • The carotids divide into the anterior and middle cerebral arteries – Anterior cerebral artery ! Tip of the frontal lobe ! Inner (mesial) surface of the hemisphere – Middle cerebral artery ! Frontal lobe ! Temporal lobe (all but the inferior portion) ! Parietal lobe • The vertebral arteries join to form the basilar artery, which then divides into the posterior cerebral arteries – Posterior cerebral artery ! Inferior portion of temporal lobe ! Occipital lobe ! Posterior inner (mesial) surface of the hemisphere • There is a structure called the Circle of Willis located at the base of the brain – This is formed by the convergence of the anterior, middle, and posterior cerebral arteries and the anterior and posterior communicating arteries – The communicating arteries connect the left and right sides of an artery, e.g., right posterior cerebral artery to left posterior cerebral artery Circle of Willis Anterior cerebral artery Posterior cerebral artery Basiliar artery Vertebral arteries Middle cerebral artery
  14. 14. 14 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 • Large dural sinuses drain the cortex through the internal jugular veins – Superior sagittal sinus – Inferior sagittal sinus – Straight sinus – Transverse sinus • The mean blood flow to the gray matter (or cerebral cortex) is greater than to the white matter • The brain is the largest energy consumer in the body due to the constant activity of the neurons • The rate of metabolism is measured by the consumption of oxygen and glucose – Positron emission imaging uses metabolism as the basis for its imaging technique – Oxygen: 3.5 milliliter of oxygen per 100 grams of brain tissue per minute – Glucose: 130 milligram of glucose per 100 grams of brain tissue per 24 hours • This rate of metabolism is constant – If the brain is deprived of oxygen for longer than 3 to 5 minutes, permanent damage may result • Energy production is created solely by the aerobic oxidation of blood glucose – The uptake of glucose is directly proportional to the functional demands from the neurons – This means there is more glucose accumulation or metabolism in areas that receive multiple stimuli • Nuclear imaging typically relies on increased or decreased blood flow to see abnormalities • Positron emission imaging relies on changes in the glucose metabolism to see abnormalities BLOOD-BRAIN BARRIER • The blood-brain barrier has a selective permeability and, when intact, only allows essential compounds from the blood stream to pass to the individual brain cells • Nutrients, such as glucose or oxygen, readily pass into the brain to maintain integrity • Large molecules, such as urea and most serum proteins, are not permitted across the barrier unless a regional or diffuse change has taken place – This change could be caused by a tumor, infarct, or abscess, etc.
  15. 15. 15 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 PLANAR BRAIN IMAGING INDICATIONS • Planar imaging indications – Identification of primary and metastatic brain tumors – Evaluation of cerebrovascular accidents – Evaluation and monitoring of cerebral infectious disease – Evaluation of trauma, e.g., subdural hematomas – Evaluation of arteriovenous malformations – Follow-up of patients after neurosurgery, radiotherapy, or chemotherapy of brain lesions – Evaluation of patients with unexplained neurologic symptoms – Evaluation of intracerebral inflammatory or degenerative diseases (e.g., AIDS, multiple sclerosis, collagen diseases) IMAGING AGENTS • Imaging agents that do not cross the blood-brain barrier are typically used in planar imaging to identify lesions in the brain – If the blood-brain barrier is disrupted, the tracer can cross the barrier and accumulates in the lesion • Commonly used agents – 99m Tc-pertechnetate – 99m Tc-diethylenetriamine pentaacetic acid (DTPA) – 99m Tc-glucoheptonate (GHA) • All three of these agents provide about the same imaging results although the imaging times vary based on the uptake and clearance rates • Additional planar imaging agents – 99m Tc-labeled red blood cells – 99m Tc-labeled phosphonates (MDP or HDP) – 67Ga-citrate – 201 Tl-chloride
  16. 16. 16 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 Table 1 Planar imaging agents (non-blood-brain barrier penetration) ACQUISITION GUIDELINES • Flow study acquisition guidelines – Bolus dose – Anterior or vertex view – Head holder or immobilization device to restrain patient’s head – 2 seconds per frame for 1 to 3 minutes – 64x64 matrix – Low energy, general purpose or high-resolution collimator – Immediate static image ! Anterior or vertex view for 500K counts • Delay (equilibrium) imaging acquisition guidelines – Image at optimum imaging time based on agent used – Typical views: anterior, posterior, right lateral, left lateral, vertex – 500K – 750K counts per view – Low energy, general purpose or high-resolution collimator – 64x64 or 128x128 matrix BRAIN DEATH EXAM • Brain death confirmation exam is performed with a planar imaging technique and a cerebral perfusion imaging agent – Typically use an agent that does cross the blood-brain barrier Radiopharmaceutical Usual dose Optimum Imaging Time Comments 99mTc-pertechnetate 15 – 20 mCi 555 – 740 MBq 2 – 4 hours Pretreat with potassium perchlorate (KCIO4), atropine 99m Tc-glucoheptonate (GHA) 15 – 20 mCi 555 – 740 MBq 1 – 4 hours ------ 99m Tc-diethylenetriamine pentaacetic acid (DTPA) 15 – 20 mCi 555 – 740 MBq 0.5 – 1 hour Rapid uptake 99m Tc-red blood cells (in-vivo) 15 – 20 mCi 555 – 740 MBq 0.5 – 1 hour Blood pool 201 Tl-chloride 2 – 3 mCi 74 – 111 MBq Immediately Metastases 67 Ga-citrate 3 – 6 mCi 111 – 222 MBq 24 – 72 hours Inflammation 99m Tc-phosphonate (MDP, HDP) 15 – 20 mCi 555 – 740 MBq 2 – 4 hours Infarcts
  17. 17. 17 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 • Evaluation of patients suspected of having brain death (typically the patient is in an unresponsive coma with a silent electroencephalogram) – This determination helps to identify the management of the patient • Flow study acquisition guidelines – Bolus dose – Anterior view – Immobilize the patient’s head – 2 seconds per frame for 1 to 3 minutes – 64x64 matrix – Low energy, general purpose, or high-resolution collimator • Delay imaging acquisition guidelines – Typical views: anterior, posterior, right lateral, left lateral, vertex ! Be sure to include the posterior fossa in the field of view for evaluation of cerebellar and brain stem activity – 500K – 750K counts per view – Low energy, general purpose, or high-resolution collimator – 64x64 or 128x128 matrix • If there is some brain function, the early equilibrium images will demonstrate some cortical circulation in the cerebral dural sinuses • If the patient is brain dead, the cortical flow will be absent – It is possible to see extracortical perfusion, but without activity in the dural sinuses • Brain death case review Notes:
  18. 18. 18 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 SPECT BRAIN IMAGING • SPECT = Single Photon Emission Computed Tomography INDICATIONS • SPECT imaging indications – Evaluation of cerebrovascular diseases, e.g., infarction, hemorrhage, transient ischemic attacks (TIA) – Evaluation of neuropsychiatric disorders such as dementia – Evaluation of head trauma – Evaluation of epilepsy – Assessment of cognitive functions IMAGING AGENTS • SPECT imaging agents are able to cross the intact blood-brain barrier – These tracers will diffusely distribute throughout the cerebral cortex, demonstrating the regional cerebral blood flow (rCBF) • Commonly used SPECT imaging agents – 99m Tc- d,l-hexamethyl propylene amine oxime (HMPAO), Ceretec – 99m Tc- oxo-l,l-N,N’-ethylenediylbis-d,d-cysteinediethyl ester (ECD), Neurolite • HMPAO is a neutral-charged lipophilic 99m Tc chelate with prolonged retention in the cortex (T½ => 6 hours) • HMPAO biodistribution – Transported to the brain via cerebral perfusion – Crosses the blood-brain barrier – Once inside the brain, it becomes trapped indicating the state of perfusion at the time of the injection – About 7 – 10% of the dosage is taken up by the brain ! Glutathione in the cells of the brain converts HMPAO to a hydrophilic form, trapping it inside the blood-brain barrier – Remainder of dosage is in blood pool and is excreted by the bowel and kidneys • HMPAO indications – Approved as an adjunct in the detection of alterations of cerebral perfusion in stroke – Labeling white blood cells to evaluate for infection • HMPAO injection technique – Essential to create same environment for every patient as the distribution and uptake is affected by disease and the current status of the brain – Inject patient in a quiet room with dim lighting – Patient should be lying down with eyes open – Start IV line several minutes prior to injection so any pain or anxiety from insertion is gone at the time of the injection
  19. 19. 19 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 • ECD biodistribution – Lipophilic tracer, which crosses the blood-brain barrier – Tracer reacts with estrase and becomes hydrophilic – Hydrophilic substances cannot pass back over blood-brain barrier – Tracer remains in brain tissue, reflecting the perfusion at the time of injection • ECD has a rapid clearance from body giving slightly higher image contrast than HMPAO – Faster blood clearance results in smaller radiation dose • If you need to sedate your patient for the exam, perform the injection prior to sedating – The perfusion will be affected by the patient’s condition at the time of the injection • Comparison of HMPAO and ECD – Difference in uptake areas – ECD has greatest uptake in occipital lobes and some believe has greater uptake in parietal lobes and superior temporal lobes – HMPAO has greatest uptake in the brain stem, cerebelli, and deep gray structures (hippocampi, thalami, basal ganglia) Notes: 133 Xenon Gas • Inert 133 Xenon gas is used to evaluate regional cerebral blood flow • When Xenon is dissolved in saline and injected or inhaled, it travels to the brain and quickly diffuses into the cerebral cortex • The Xenon rapidly clears multiexponentially from the brain – Its rate of clearance is used to calculate the regional blood flow in milliliters/100 grams/minute • The lower gamma photon energy of 81 keV reduces the detection accuracy at increasing depths – SPECT imaging can overcome this limitation • Xenon imaging – Provides quantitative information – Used for activation studies – Dual isotope studies – Use is limited by availability of equipment to optimize imaging of Xenon Notes:
  20. 20. 20 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 123 Iodine-Iodoamphetamine (IMP) and 123 Iodine-HIPDM • 123 I-IMP and 123 Iodine-HIPDM have limitations of relatively short brain retention and redistribution • Redistribution appears to occur from the initial high lung uptake pool and may be a way to detect cerebral ischemia and to image remaining viable metabolically intact cerebral tissue • These agents are no longer commercially available in the United States SPECT Imaging Agents Summary Table 2 SPECT imaging agents (blood-brain barrier penetration) PHARMACOLOGIC INTERVENTION • Pharmacologic agents can be used to help identify the cerebral area at risk in patients experiencing transient ischemic attacks (TIA) or be used as a screening tool in asymptomatic patients – Acetazolamide (ACZ), sold under the name of Diamox (Lederle, Inc.) • Acetazolamide is a vasodilator, causing increased blood flow in normal cerebral vessels • If an area already has decreased blood flow and therefore, loss of cerebrovascular reserve, the acetazolamide will have little to no effect on the perfusion • Acetazolamide procedure – Usually perform routine perfusion exam for baseline – Diamox is injected slowly over a 2-minute time period – Inject second dosage and perform Diamox exam to evaluate changes in perfusion – Contraindications: Allergies to sulfur, recent stroke Notes: Radiopharmaceutical Usual Dose Optimum Imaging Time Comments 99m Tc-HMPAO 20 mCi 740 MBq 0.25 – 3 hours rCBF 123 I-iodoamphetamine 3 – 5 mCi 111 – 185 MBq 0.5 – 1 hour rCBF 133 Xe (gas) 0.5 – 10 mCi 18.5 – 370 MBq Immediately rCBF 99m Tc-ECD 20 mCi 740 MBq 2 – 3 hours rCBF
  21. 21. 21 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 ACQUISITION GUIDELINES • Proper quality control evaluation is essential for high quality SPECT brain images – Center of rotation – Uniformity correction – Others as recommended by the equipment manufacturer • The acquisition parameters will vary depending upon the number of detectors used for imaging • SPECT acquisition guidelines – Low energy, general purpose or high-resolution collimator – Head holder or immobilization device to restrain patient’s head – 128x128 or 64x64 matrix – Apply appropriate zoom factor for system being used – 360-degree total rotation – 64 or 128 total views – Time per view dependent upon the number of detectors used for imaging ! Single head system " 30 seconds per view, 64 views " 15 – 20 seconds per view, 128 views ! Dual head system " 30 – 60 seconds per view, 32 views " 15 – 30 seconds per view, 64 views • SPECT reconstruction guidelines – Reconstruction parameters will vary depending upon the system used for imaging and your facility’s preference – 1 – 2 pixel slice thickness – Butterworth pre-filter ! Critical frequency: 0.5 – 0.7 cycles/centimeter ! Power factor: 10 – Ramp back projection filter – Attenuation correction – Uniformity correction • ECD case review Notes:
  22. 22. 22 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 TRANSIENT ISCHEMIC ATTACKS • Transient ischemic attacks (TIA) occur in 10 to 20 percent of stroke patients • If this condition goes untreated, as many as 60 percent of these patients will have one or more completed strokes in the future • It is important to verify a diagnosis of a TIA quickly – Cerebral blood flow images reflect the perfusion to the brain at the time of the injection • In the case of a TIA, the perfusion may have already returned to normal by the time the exam is performed, thus showing normal results • The sensitivity of the nuclear perfusion exam is about 60% during the first 24 hours post-TIA and drops to less than 40% by 1 week
  23. 23. 23 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 NEURORECEPTOR IMAGING • There are several agents that have been developed for imaging various brain disorders and neuroreceptors – In the United States, these agents are still undergoing clinical investigation • These agents have increased the ability to evaluate certain cerebral neoplasms and disorders, such as Parkinson’s disease and Alzheimer’s disease Notes: • An important aspect of performing neuroreceptor imaging is to understand the systems involved in the function of the receptors • One area of receptors that is undergoing significant investigation is dopamine receptors • The brain uses several different types of neurotransmitters, which are the chemicals that transmit nerve impulses from cell to cell – The cell transmitting the nerve impulse emits these neurotransmitters • Two types of receptors receive the neurotransmitters – Postsynaptic receptors, which are on the receiving cell and allow the neurotransmitter to stimulate an impulse in that cell – Presynaptic receptors or transporters, which are on the transmitting cell and reabsorbs the neurotransmitter molecules, thus terminating the transmission • Neural cells specialize in whichever type of neurotransmitter molecule they use • The dopaminergic neurons, the brain cells that use dopamine as the neurotransmitter, are concentrated in the substantia nigra areas of the brain stem (which is not well imaged with nuclear medicine) and in the putamen and caudate nucleus areas of the basal ganglia, at the center of the cerebrum (which can be easily imaged) • These dopaminergic neurons degenerate in Parkinson’s disease and some other similar, but less common conditions – The hallmark of these conditions is disorders of motion • The classic example of over stimulation of dopamine activity is seen in cocaine abuse – Psychotics also have an imbalance in this regard – Antipsychotic drugs have the known side effect of the production of motion disorders, which can be treated with anti-Parkinsonian drugs • Many of the agents being used for receptor imaging are not commercially available in North America – Most of the work is being performed in Europe and Japan • 123 I-FP-CIT (Datscan) – Agent being investigated by Nycomed Amersham for the evaluation of Parkinson’s disease – This agent uses tropane molecules, which are cocaine analogues • 123 I-Beta-CIT – Evaluate movement disorders such as Parkinson’s and Huntington’s disease
  24. 24. 24 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 • 123 I-iodobenzamide (IBZM) and 123 I-iodobenzofuran (IBF) – Dopamine D2-receptor imaging for neuropsychiatric disorders • 123 I-iomazenil (IMZ) – Evaluate benzodiazepine receptor distribution in patients with Alzheimer’s disease – IMZ is a benzodiazepine receptor agent, which binds to those receptors that bind tranquilizers such as Valium and Xanax • Additional information can be found in Diagnostic Nuclear Medicine, Third Edition, Volume Two, written by Sandler, Coleman, Wackers, Patton, Gottschalk and Hoffer. Published by Williams and Wilkins, 1996. Pages 1135 – 1145 • IBF case review Notes:
  25. 25. 25 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 CISTERNOGRAPHY INDICATIONS • The choroid plexuses in the ventricles are continually producing cerebral spinal fluid or CSF – Radionuclide cisternography is one of the most reliable methods available to evaluate the dynamics of cerebral spinal fluid • Cisternography indications – Evaluation of normal and abnormal pathways of cerebral spinal fluid drainage – Evaluation of cerebral spinal fluid hydrodynamics – Evaluation of shunting in hydrocephalus – Assessment of shunt patency – Diagnosis and localization of cerebral spinal fluid leaks such as in rhinorrhea and otorrhea IMAGING AGENTS • In adult imaging, DTPA labeled with Indium-111 is used as the radionuclide – This agent provides a good amount of gamma photons with energies of 173 and 247 keV and a physical half-life of 2.8 days – This allows serial imaging for several days • When performing cisternography on a pediatric patient, Indium-111 is typically not used because of the higher radiation exposure – 99m Tc-labeled human serum albumin is recommended – The shorter half-life of technetium does not cause a significant limitation because the CSF hydrodynamics in children are more rapid ACQUISITION GUIDELINES • The imaging agent is injected by a physician using a sterile, atraumatic injection into the lumbar intrathecal space • Immediately after the injection, acquire an image at the site of the lumbar puncture to make sure the tracer was injected into the intrathecal space – Static image – 100K counts • The tracer will move along with the CSF – With a good administration, you should see a short vertical line of activity in the spinal column
  26. 26. 26 of 26 © 2001 General Electric Company. All rights reserved. GE Medical Systems NM: Brain Imaging Program Supplement REV 1 • Acquisition guidelines – Medium energy, general-purpose collimator for Indium-111 – Low energy, general-purpose collimator for technetium-99m imaging – Series of static images obtained over a period of 2 to 48 hours, depending upon the patient – Typically acquire 4 views: anterior, posterior, right lateral, and left lateral ! Vertex view may be acquired as needed – 100K counts or 10 minutes per view – 64x64 matrix • Routine imaging times for adults is performed at 2 hours, 6 hours, 24 hours, and 48 hours post-injection – If the movement of the tracer is significantly slow, you may have to acquire images at 72 and possibly even up to 96 hours post-injection • For children, the imaging times are much closer together – Imaging usually occurs at 1 to 2 hours, 4 to 6 hours, 8 hours, and 24 hours post-injection CSF LEAK • Sometimes, the physician may suspect a cerebrospinal fluid leak in the nose (rhinorrhea) or ear (otorrhea) • The CSF leak can be evaluated by using pledgets inserted into the appropriate location – The physician prior to the injection of the imaging agent inserts the pledgets – At the appropriate time, the pledgets are removed and counted • The patient pledget counts are compared to the counts from a standard, background pledget ! If the patient counts are three to four times higher than background, a significant leakage is indicated • Case review

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