SP7:Central Nervous System Scintigraphy Flashcards
The venous phase of a cerebral blood flow study is signaled by:
(a)Visualization of the jugular veins
(b) Appearance of the radiopharmaceutical in the superior sagittal sinus
(c) Disappearance of radiopharmaceutical from the carotid arteries
(d) Appearance of radiopharmaceutical in the middle cerebral arteries
(b) The superior sagittal sinus is a dural venous sinus located in the midline. Tracer usually appears thereafter about 15 s signifying the venous phase of the blood flow study. In some cases, low-level activity in the sagittal sinus from the scalp can be mistaken for venous flow.
The localization of 99mTc HMPAO is related to:
(a)A breakdown of the blood–brain barrier
(b) Cerebral blood flow
(c) Glucose metabolism
(d) Distribution of neuroreceptors
(b) Exametazime enters the brain via the cerebral blood flow. It then crosses the blood–brain barrier and is metabolized to a form that cannot diffuse out of the brain.
CSF is made mostly of:
(a)Protein
(b) Water
(c) Glucose
(d) Blood
(b) Cerebrospinal fluid, which is produced in the choroid plexus and serves to cushion the brain and spinal cord, is about 99% water. It also contains a small percentage of plasma proteins.
The function of cerebrospinal fluid is to:
(a)Protect the brain and spinal cord against shock.
(b) Filter plasma.
(c) Produce neurotransmitters.
(d) All of the above.
(a) Cerebrospinal fluid acts as a shock absorber for the brain and spinal cord. It occupies the subarachnoid space and the cord’s central canal.
When positioning for a radionuclide angiogram, the patient should be positioned:
(a)Posteriorly
(b) Anteriorly
(c) With as much facial activity as possible excluded
(d) None of the above
(b) Images are ideally obtained anteriorly, with the patient upright whenever feasible. The neck should be included, and the top of the head should not be outside the FOV. However, in many cases, the condition of the patient makes this positioning impossible.
Exametazime is also known as:
(a)DTPA
(b) MAG3
(c) HMPAO
(d) ECD
(c) HMPAO is hexamethyl propylene amine oxime and is also known as exametazime. ECD means ethylene l-cysteinate dimer and is also known as bicisate. MAG3 is mertiatide, and DTPA is diethylenetriaminepentaacetic acid.
Bicisate is also known as:
(a)DTPA
(b) MAG3
(c) HMPAO
(d) ECD
(d) HMPAO is hexamethyl propylene amine oxime and is also known as exametazime. ECD means ethylene l-cysteinate dimer and is also known as bicisate. MAG3 is mertiatide, and DTPA is diethylenetriaminepentaacetic acid.
CSF dynamics are studies following administration of 111In DTPA:
(a)Via intravenous injection
(b) Via intraperitoneal injection
(c) Via intrathecal injection
(d) Via intradermal injection
(c) 111In DTPA (or other radiopharmaceuticals) is injected by lumbar puncture into the aubarachnoid space, the intrathecal space surrounding the spinal cord.
The dose which would commonly be used for a radionuclide angiogram with 99mTc DTPA is:
(a)5 mCi
(b) 10 mCi
(c) 20 mCi
(d) 25 mCi
(c) The Society of Nuclear Medicine (Feb 2003) recommends 15-20 mCi of 99mTc DTPA for brain death scintigraphy. Ten to 30 mCi is recommended for 99mTc HMPAO and 99mTc ECD.
Which of the following is true regarding injection of the radiopharmaceuticals for SPECT brain imaging?
(a)Lights should be dimmed during injection
(b) The patient should be encouraged to read or watch TV during injection to take his or her mind off any pain.
(c) Family members should be allowed to talk to the patient during injection.
(d) Injection should be made immediately after venous puncture to avoid clot formation.
(a) Since various stimuli and cognitive functions will affect regional blood flow, the venous access should be achieved a few minutes before injection. The patient should then wait in an atmosphere of minimal stimuli (light, noise, pain, etc.).
Which dose could be used for 99mTc ECD or 99mTc HMPAO for SPECT brain imaging?
(a)2-5 mCi
(b) 5-7 mCi
(c) 7-10 mCi
(d) 20 mCi
(d) 15 to 30 mCi of 99mTc HMPAO or 99mTc ECD is injected for SPECT brain imaging.
Ictal SPECT and PET studies require an injection of radiopharmaceutical:
(a)During a seizure
(b) Immediately after a seizure
(c) Between seizures
(d) Both (a) and (b)
(d) Ictal examinations are performed by injecting the radiopharmaceutical during or within 30 s following a seizure. Interictal examinations are those performed between seizures.
HMPAO and ECD are lipophilic agents that do not significantly redistribute in the brain.
(a)True
(b)False
(a) Because HMPAO and ECD do not restistribute in the brain for at least an hour following intravenous injection, they are particularly useful for ictal studies, allowing an image of blood flow during seizure activity.
Advantages of using ECD over HMPAO for SPECT imaging of the brain include:
(a)Can be injected up to 6 h after preparation
(b) More rapid clearance from the bloodstream
(c) Better target to background ratio
(d) All of the above
(e) None of the above
(d) HMPAO should be used within 4 h after kit preparation. ECD can be injected up to 6 h after labeling and clears more quickly from the blood. This rapid clearance results in increased target to background.
White matter has about four times greater blood flow than gray matter:
(a)True
(b)False
(b) Gray matter has much greater blood flow than white matter. For this reason, gray matter will have greater activity than white matter when performing these examinations with HMPAO or ECD.
Planar images of the brain using 99mTc DTPA are obtained:
(a)Immediately after the dynamic exam
(b) 30 min after injection
(c) 1 h after injection
(d) 1.5 h after injection
(a) A dynamic study is usually obtained immediately following injection, and further imaging may be carried out at any time up to 2 h after injection> If brain-specific agents are used, images may be obtained after a delay of at least 20 min.
The purpose of placing an elastic band around a patient’s head just above the orbits during a radionuclide angiogram is:
(a)To decrease the activity from the orbits
(b) To increase intracranial pressure
(c) To decrease blood supply to small scalp vessels
(d) To immobilize the patient
(c) When a radionuclide angiogram is used to confirm brain death, it may be difficult to differentiate scalp perfusion from intercerebral blood flow. An elastic band situated above the orbits can reduce the flow to scalp vessels.
The images obtained with PET study using 18FDG can best be described as:
(a)Anatomical
(b) Perfusion
(c) Metabolic
(d) Dynamic
(c) Metabolic refers to the building up to substances (anabolism) and the breaking down of substances (catabolism). FDG is a glucose analog and therefore is metabolized initially in the same way that glucose is. Unlike glucose, it is not further metabolized after localizing in the brain substance (because it is phosphorylated) and is therefore a useful imaging agent.
In a Diamox challenge study, vascular disease will appear as decreased perfusion after the use of Diamox.
(a)True
(b)False
(a) In areas of normal perfusion, blood flow increases by three to four times following the administration of Diamox, or acetazolamide, which causes vasodilatation. In patients with decreased regional perfusion, the Diamox challenge study may show a perfusion increase. About half of patients will experience side effects, and so all patients should be carefully monitored, although symptoms (lightheadedness, facial flushing and numbness, and numbness in the fingers) usually resolve themselves in about 15 min.
The injection for a CSF shunt patency study is:
(a)Intravenous
(b) Subcutaneous
(c) Intrathecal
(d) Into the shunt reservoir or tubing
(d) In a shunt patency study, the radiopharmaceutical is administered directly into the shunt reservoir or the tubing. Activity is then followed to diagnose a malfunction of the shunt. It is necessary to understand the particular type of shunt and its path to diagnose obstruction.
Shunts which divert the flow of CSF are often used to treat:
(a)Communicating hydrocephalus
(b) Noncommunicating hydrocephalus
(c) CSF leak
(d) All of the above
(e) (a) and (b) only
(e) Communicating hydrocephalus results when CSF resorption is faulty. Noncommunicating hydrocephalus is caused by obstruction of CSF flow. Shunts may be used to treat communicating hydrocephalus. CSF leaks may result from hydrocephalus (among many other things), but shunts are not used to treat the leak.
Which of the following agents will cross a intact blood-brain barrier?
(a)99mTc DTPA
(b) 99mTc GH
(c) 99mTc pertechnetate
(d) 99mTc HMPAO
(d) 99mTc HMPAO, or exametazime, is a lipophilic radiopharmaceutical. It crosses the blood-brain and then is metabolized to another form which does not diffuse out of the brain. The other choices only cross a compromised blood-brain barrier.
Which radiopharmaceutical is not commonly used for brain perfusion imaging with SPECT?
(a)99mTc DTPA
(b) 99mTc HMPAO
(c) 99mTc ECD
(a) 99mTc DTPA does not cross the blood-brain barrier and is useful for radionuclide cerebral angiograms. 99mTc HMPAO and 99mTc ECD are used for SPECT studies of brain perfusion.
A technologist neglects to give a patient potassium perchlorate before injection with 20 mCi of 99mTc pertechnetate. How will this affect the static brain images taken at 1 h after injection?
(a)Thyroid activity may be seen.
(b) Choroid plexus may be seen.
(c) Salivary glands may be seen.
(b) 99mTc pertechnetate will eventually collect in the choroid plexus. Therefore, if delayed static images are planned, oral potassium perchlorate should be given, or another radiopharmaceutical should be used.