Transcript SUMMARY OF PSYCHIATRIST GUIDE TO NUCLEAR MEDICINE

SUMMARY OF PSYCHIATRIST
GUIDE TO NUCLEAR MEDICINE
Maroun Karam MD FACP
Professor of Radiology and Nuclear
Medicine
Somatic symptoms with frequent
psychological causes
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Nausea and vomiting
Abdominal pain
Chest pain
Generally the psychiatrist refers first to medical
specialist to exclude organic cause but
- some symptoms such as vomiting can be
dramatic and require immediate attention
- it is important to be aware of nuclear tests that
can be done
Nausea, Flatulence and
Dyspepsia,
are non specific abdominal complaints
commonly encountered in a primary care
setting.
Routine work-up is often unproductive.
Two Nuclear medicine tests may provide an
answer.
1. Measurement of gastric emptying
2. HIDA scan with measurement of GB EF
for detecting biliary dyskinesia.
Common drugs and gastric emptying
• Erythromycin accelerates considerably GE
• Opiates slow down GE ( nausea as side effect)
• SSRI and most psychotropic drugs slow down
GE ( except stimulants ) but stimulate appetite
• Antisecretory drugs slow down GE
• NICOTINE decreases significantly gastric
emptying . This mechanism explains frequent
gain weight after smoking cessation
GASTROPARESIS
Definition: Delayed gastric emptying in the
absence of mechanical obstruction.
- Relatively uncommon as compared to other
causes of nausea such as gastroenteritis
- Very common in long-standing diabetes (3050%).
- Diagnosis difficult to make on clinical
grounds alone.
- Present in over 40% of pts with severe reflux
Principles and technique
• Universal tracer : Technetium sulfur colloid
• Standard international meal
- 2 slices of toast bread
- 125 ml of eggwhite or “Eggbeaters”cooked
- 30 gr of jelly
- 0.5 mci Tc SC ( 50 times less than the dose
for bone scan)
Normal Values
Time Elapsed
Lower Normal Limit for
Gastric Emptying
60 min
10%
120 min
40%
240 min
90%
Values are the 95th%ile CI
*
Tougas et al,
Abell et al,
Lin et al.
Nl 60 min 10-20%
120 min 40- 80%
240 min 90-100%
Patient with long history of mental
illness and daily vomiting Psychogenic?
GE at 1 hr : 8% ( 10-40%)
GE at 2hrs : 21% ( 40-80)
GE at 4 hrs : 43% ( 90-100)
LESSON
• Measurement of GE can help distinguish
psychogenic from real gastroparesis in pts
with mental illness
• Discontinuation of opiates, erythromycine and
psychotropic drugs 24 hr before the trst is
necessary to avoid drug interference
Psychological symptoms
Organic brain disease or mental illness
• At least 30% of patients with Alzheimer disease
present with atypical symptoms mostly
psychiatric such as agitation , hostile behavior ,
depression etc
• The opposite is true : 30% of elderly patients
with cognitive decline DO NOT have dementia but
underlying depression
• Some symptoms such as tremor may be
psychogenic vs essential vs Parkinsonian
• Intermittent acute confusion may be due to
occult temporal epilepsy
WHY IMAGE DEMENTIA?
• It is important for the psychiatrist to determine if there is
underlying dementia because we have now at least symptomatic
treatment for certain types
• In medico-legal cases the physician expert designated by the courts
needs to show OBJECTIVE EVIDENCE OF DEMENTIA
• The best and most experienced physician will make diagnostic
mistakes bases on clinical evaluation only (example : since we have
Nuc imaging of Parkinsonian syndromes , when compared to
postmortem evaluation there remains 10% error in clinical
classification( essential tremor vs PD , PD vs APD)
• Clinical diagnosis of dementia by expert is only 65% accurate as
compared to postmortem evaluation
WHY NUCLEAR IMAGING?
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Because MRI although very good to confirm or exclude vascular
disease is limited for evaluation of other types of dementia
Because the best way to detect dementia is through
Molecular Imaging
Molecular imaging is the visualization, characterization, and
measurement of biological processes at the molecular and
cellular levels in humans and other living systems
The greatest fruits of this approach will be in understanding
the brain and psychiatric illness because it has escaped so far
detection with Conventional imaging
For instance in AD FDG PET is more accurate than initial clinical
evaluation ( sens 84% Spec 74% vs 66% and 58% )
FDG PET is more accurate in distinguishing FTD from AD than
other methods ( Sens 96% , Spec 85% )
WHY TRY TO DETERMINE THE TYPE OF DEMENTIA ?
1.Medications we are using for the symptomatic treatment of Alzheimer disease
do not work on vascular dementia
2 Making a diagnosis of fronto- temporal dementia may have ethical implications
( 50% are familial : genetic counseling etc
3 Antipsychotic medications given to certain patients with dementia can be harmful
If they suffer from fronto -temporal dementia
4There is at least one promising drug in clinical trial for AD
WHY PET HAS BECOME SO IMPORTANT?
BECAUSE OF FGD NAMED BY TIME MAGAZINE MOLECULE OF THE CENTURY
1. FDG ( fluoro 18 desoxyglucose)was discovered in 1976 and was used extensively in
to study glucose brain metabolism but it remained limited to large research
centers . Desoxyglucose is an analog of glucose labeled with F 18, a positron emitter
2. Many insights were gained about brain metabolism when the brain engages in
Various mental functions and various patterns of neuronal loss in dementia
3. We have now almost 40 yrs of data on brain metabolism with FDG
- in healthy brain : Before functional MRI we have detected what happens to
Various brain areas during certain tasks ( reading, listening to music )
- we know what areas of the brain grow during certain development stages of
the brain in the child
- We have detailed regional changes of brain metabolism with age and we have
Maps of brain FDG UPTAKE in normal individuals from age 50 to 90
- Plotting the findings of a patient against the data of age matched controls allows
us to detect subtle regional abnormalities
Alzheimer’s
disease is not
the only cause of
dementia.
After age 85 , 50% of individuals have
dementia and 90% of these have AD
Because of the aging of the population
AD has become the major target of research
Fronto
Temporal
Dementia
MRI was nl
TYPICAL FDG PET PATTERNS IN A: AD, B: DLB ( OCCIPTAL ) C: FRONTAL VARIANT FTD; D:
NONFLUENT APHASIA FTD WITH MARKED ASSYMETRY INVOLVING L TEMP AND PAR LOBES
CLINICAL USEFULNESS OF FDG PET IN DEMENTIAS
1. Very effective in answering the question : Dementia or non dementia ?
when symptoms are atypical or very mild .
2. Very effective in confirming vascular dementia ( random distribution of defects)
3. Very effective in confirming frontotemporal dementia ( SPECT as good as PET for this
Indication but more difficult to obtain SPECT tracer than PET tracer in Lebanon )
4. Moderately effective in distinguishing between AD and DLB ( Occipital involvement )
LIMITATIONS OF FDG PET IMAGING IN
DEMENTIA
• FDG PET is excellent to confirm the diagnosis
but is moderately effective to distinguish
between AD and DLB
• When FDG PET becomes clearly positive there
has been great amount of neuronal loss and it
is probably too late to change the course of
disease
• However until we have drugs that effect
disease course this limitation is irrelevant
SOME IMPORTANT PRACTICAL CONSIDERATIONS
• Currently the only place I have access to do PET
is LAU/Rizk hospital
• Through negotiations I was able to bring down
the price of PET from 750 USD for cancer to 500
USD for brain only ( private payer ) and 600
(private insurance)
• Remains the problem of DAMAN I need your help
• If MRI has excluded vascular etiology how can we
get DAMAN reimbursement for FDG PET?
• In the USA brain PET is also reimbursed for brain
tumors and epilepsy diagnosis