Seminars Flashcards
Extrapyramidal definition
corticospinal motor pathways (pyramidal projections) are not the primary site(s) of dysfunction
PSP
Bradykinesia/rigidity, supranuclear ocular palsy
FDG: Decrased striatum
DATSCAN: symmetric defects
No Lewy Body’s, TAU positive
MSA
Autonomic dysfunction
FDG: Decfreased striatum
DATSCAN: Symmetric defects
Corticobasilar degeneration
Dystonia, myoclonis, alien limb
FDG: Decreased precentral and post central gyri, decreased striatum, decreased thalamus
DATSCAN: assymetric reduction
Parkinson’s features
FDG: increased striatum (early stages)
I123-ioflupane (DATSCAN) - assymetric defect putamen > caudate
Lewy body deposition
Protein deposition in LBD
All have alpha-Syn protein deposition; subset have beta amyloid and tau (overlap with AD)
3 Pillars of drug survival
tissue exposure
target engagement
pharmacologic activity
NeuroPET targers
Dopamine:
- D1, D2/D3 (C11-raclopride), DAT (I123-Ioflupane), 5-L AA transporter (DOPA)
Seratonin:
- 5HT receptor agonists/antagonists
Opiod:
- u opiod receptor agonist - C11-carfentanyl
GABA
- GABA receptor antagonist (C11-flumazenil)
Beta amyloid -
- C11PIB
- F18-flurbetapir
Combined beta amyloid and neurofibrillary tangles:
- F18-FDDNP
Appropriate use amyloid PET
- Cognitive complaint with objectively confirmed impairment
- AD is a possible diagnosis, but diagnosis is uncertain after a comprehensive evaluation
- Knowledge of the presence or absence of Aβ pathology will aid diagnosis or management
- Persistent or progressive unexplained MCI
- Possible AD with an unclear clinical presentation (see text)
- Atypically early-age-onset progressive dementia (less than ~65 y in age)
PET tracers being used for gliomas
C11-MET
C11-AMT
F18-FET
F18-DOPA
PET findings in addiction
low striatal D2 receptors and dopamine transmission
Applications of beta amyloid imaging and tau
Noninvasive identification of Alzheimer disease pathology
Early diagnosis
Prediction of disease progression and response to disease-specific therapy
Subject selection for disease-specific trials
Monitor target engagement and effectiveness of disease-specific therapy
Tau tracers
F18-AV1451
Dosimetry before I131 therapy in children
Measure RAIU with < 10-15 MBq of I131 or I124 PET to avoid stunning
Two neurocutaneous syndromes with epilepsy ammendable to surgical treatment
TS
Sturge-Weber (angiomatosis, calcifictions, atrophy, gliosis)
Children - differences in MIBI and tetrofosmin biodistribution
Higher hepatic retention - do delayed at 90 min
Sp I123 and 131-MIBG
Specificity between 90-100%
PET tracers for NB
F18-FDG
F18-DOPA
Ga68-DOTATATE
BEIR statement on radiation carcinogenic risk in children
2-3 x higher than adults
ICRP Effective Dose Organ radiosensitivity weights
- 12 = Breast, Red Marrow, Lung, Colon, Stomach
- 08 = gonads
Lowest = 0.01 (brain, bone surface, salivary glands)
Rank effective dose (mSv) for the following studies: DMSA, MDP, MAG3, FDG
FDG (7.0) > MDP (4.2) > MAG3 (2.6) > DMSA (1.1)
Most common cause congenital hypothyroidism
Thyroid dysgenesis
ROME consensus for imaging in congenital hypothyroidismn
Knee radiographs (absent femoral and tibial epiphyses) reflect severity of hypothyroidism
Thyroid US
Thyroid scintigraphy
Timing of scintigraphy for CH and initiation of L-thyroxine
Imaging must be done within a week of beginning therapy
Protocol for congenital hypo
Prep: ensure < 1 week since starting therapy
Tracer: I123 - 0.03 mCi, image after 1 hour; Tc99m - 0.11-0.22 mCi, image after 15 minutes
Dose: I123 - 3.6 mSv; Tc99m - 1.2 mSv
Collimator: LEHR
Matrix: 128 x 128
FOV: anterior acquisition of trunk
Milk scan protocol
Prep - 4-6 hr fast
Tracer: 0.25 mCi Tc99m-SC
Position: Supine; posterior images
Matrix: 128 x 128, 5-10s vs 30s frames x 60 minutes, then static chest with 256 x 256 matrix
FOV: mouth to upper abdomen
Critical organ - lower large bowel
Salivagram protocol
Prep: None
Tracer: 0.3 mCi Tc99m-SC
LEHR collimator, 128 x 128, dynamic 60min 30s frames, then static A and P chest at 256 x 256 for 3-5 min
Dose reduction strategies pediatric PET/CT
- Eliminate unnecessary tests
- Reduce dose of tracer
- Reduce CT imaging params - decrase mAs, kvp; Incrase pitch; use dose modulation
- Reduce area imaged
- Choose appropriate CT - diagnostic vs non-diagnostic
Pediatric MDP dose and timing
0.25 mCi/kg, image at 2-4 hrs
Main advantage of direct RNC vs indirect
Both the filling and micturition phases assessed, increasing sensitivity of study
Expected bladder capacity for age
30 + (30*age in yrs)
International Reflux grading system
1 = Contrast refluxes into normal sized ureter
2 = Contrast reflues into non-dilated ureter and pelvicalyceal system
3 = Mild hydronephrosis, sharp angle of fornices blunted
4 = Moderate dilatation with distortion of fornices
5 = severe dilatation, tortuosity of ureter, clubbing of calyces
Techniques for Crohn’s imaging
- WBC scintigraphy - extent of active disease; differentiates inflammatory from fibrotic strictures
- FDG-PET - Non-specific pan-inflammatory marker; high radiation dose
- FDG PET-MRI -
Nuc medicine tracers for type 1 diabetes
F18-DOPA - quantifying functional beta cell mass
Radiolabeled IL-2 - Uptake correlates with duration of disease
Classic Hodgkin’s lymphoma classification
- Nodular sclerosing
- Mixed cellularity
- Lymphocyte rich
- Lymphocyte depleted
PET tracers for imaging bone marrow
- F18-FDG (glucose metabolism)
2. F18-FLT (DNA proliferation)
SPECT tracers for imaging bone marrow
- Tc-SC (RES)
- Tc-nannocolloid (RES)
- Tc/In111-WBCs - RES/neutrophils
Dual time point imaging (DTPI)
Malignant lesions tend to accumulate FDG more than normal tissues, therefore higher target to background on delayed
Benign bone/soft tissues lesions with high FDG uptake (false positives)
Hibernoma Sarcoid Myosotis ossificans Infection \+ Bone lesions (osteoid osteoma, GCT, enchondroma)
Malignant bone/soft tissue lesions with low FDG uptake (false negative)
well diff liposarc
myxoid liposarc
chondrosarcoma
chordoma
PET findings relapsing polychondritis
Auricular, nasal, larynx, tracheal chondritis
Bronchial chondritis
Relapsing polychondritis
3 major types of aggregated amyloid proteins
- beta amyloid
- Tau
- alpha-synuclein (alpha-syn)
Desired amyloid PET properties
- Selectively binds amyloid
- Crosses BBB
- No radiolabeled metabolites in brain
Venn diagram aggregated amyloid proteins
- Pure beta amyloid = cerebral amyloid angiopathy
- Pure tau = Frontotemporal dementia, CBD, PSP
- Pure alpha-syn = PD, DLB, MSA
- Beta amyloid + tau = AD
- All 3 = Lewy Body variant AD
Radiolabeled peptide definition
Between small molecules and large biologics
Eg. SSTRs, PSMA
C11 production
N14(p,alpha)C11
Y90
From Sr90->Y90
T1/2 64h
100% beta
mean energy 935 keV; mean path 2.5 mm
Lu177
From neutron activation of Lu176(n,gamma)Lu177
T/1/2 6.7d; 79% beta; mean free path 0.7 mm; mean free energy 130 kev
Perfusion changes following surgery for CHD
- Fontan - preferential drainage to one lung if only upper limb injected -> need to do upper and lower limb injection
- Unidirectional Glenn - same
3.
Tc99m-tilmanocept
Used for lymphscintigraphy
targets CD206 receptor on macrophages and dendritic cells
Sustained uptake in first order lymph nodes
When to not do lymphoscintigraphy for breast CA
Invasive cancer T3/T4
Inflammatory breast cancer
DCIS with plan for conservative surgery
Pregnancy
Most important prognostic factors in a patient with GI cancer?
- Tumor depth
2. Metastatic lymph node spread
Normal HIDA scan time reference poitns
Peak liver by 10 min
CBD by 20min in most
GB and small bowel by 30 min in most
SB by 60 min in 80%
Pros Radiation planning based on PET/CT derived volumes
- Less risk of missing disease, small nodes
2. Incidental synchronous tumours
Cons Radiation planning based on PET/CT derived volumes
- FDG uptake in non-malignant tissues
- Non-FDG avid lesions could be overlooked
- PET does not detect microscopic disease
Lymphoma histologies not well evaluated by PET due to variable uptake
- CLL
- Marginal zone lymphoma
- Lymphoplasmacytic lymphoma
- Cutaneous T cell lymphoma including mycosis fungoidfes
Lymphoma staging according to Lugano classification
Limited = Stage I and II
I - one node or group of adjacent nodes; single extranodal lesion without nodal involvement
II - Two or more nodal groups on either side of the diaphgragm; Stage I or II with limited contiguous extranodal involvement
Advanced = III and IV III = Nodes on both side of diaphgram; nodes above the diaghragm with spleen involvement
IV = Additonal non-contiguous extralymphatic invovlement
Nodal tissues according to Lugano
Tonsils, weldeyer ring, and spleen are considered nodal tissues not extranodal sites of disease
FDG avid lymphomas
HL DLBC lymphoma Follicular Mantle cell Burkitt Marginal zone
SUVpeak
Maximum tumor activity within a 1-cm3 VOI in the hottest part of the tumor volume
Does not require definition of tumour boundaries
Slightly affected by noise (better than SUVmax)
SUVmean
Depends on segmention method
Moderately affected by noise
MTV
Metabolic tumour volume
MTV represents the total volume of the metabolically active tumor in a VOI, expressed in cubic centimeters or millili- ters, and is slightly affected by noise
TLG
Total lesion glycolysis
= semented tumour volume SUVmean x MTV
PET image segmentation techniques
- Manual
- Fixed - fixed threshold of SUV
- Adaptive - adapted to tumour to background ratio
- Gradient - Edge detection methods
Purpose of DEXA images
- Confirm ROIs
- Detect motion
- Identify overlying structures, hardware, calc
- Incidental disease
Risk factors for osteoporotic fractures
- Prior fragility fracture
- Age
- Sex
- Low BMI
- Race (white > black)
- Alcohol/smoking
- FH hip fracture
- Glucocorticoid use
Cardiac sympathetic NS tracer for PET
C11-HED
Clinical uses for PET myocardial blood flow
- Identification/characterization subclinical CAD
- Extent and severity of multivessel CAD
- Detecting balanced ischemia
Indications for viability imaging with PET
- EF<40% and known or suspected CAD
2. NYHA class >= 2
Who does not need viability imaging
Angina CCS >=2
Normal or mild LV dysfunction
Critical L main disease
Good targets
Rank resolution for cardiac PET perfusion tracers
F18 flurpiridaz > N13 ammonia > O15 water > Rb 82
Also same rank of positron range
Rank extraction fraction for cardiac PET perfusion tracers
O18 H20 (100%) > Flurpiridaz (94%) > N13 ammonia (80) > Rb82 (65)
i131 gamma and beta energies
356kev gamma
606 kev beta
Which is better for retrosternal evaluation: Tc99m-pertechnetate or I123
123
Normal distribution FDOPA
Basal ganglia, pancreas, liver, duodenum, gallbladder, biliary tracts, kidneys, ureter
CrCl formula
[(140-age) x weight]/(72xsCr); multiple by 0.85 if female
Broad classification of artifacts
Instrumental Technical Radiopharmaceutical Patient Treatment related
C11-flumazenil
GABA
Delineates seizure focus better than FDG
Sensitiive in mesial temp sclerosis
Hypoxia imaging agent
F18-FMISO, can be used for gliomas
Scintomammography indications
- Equivocal findings on mammo, US, MRI
- Non-diagnostic mammo and contraindication to MR
- Nipple discharge, no abnormality on other modalities
- Suspected recurrence
- Response to neoadjuvant chemo
ATA pediatric intermediate risk thyroid cancer
- Extensive N1a (level VI) or minimal N1b (I-V) nodes
- Low risk for distant mets but increased risk for incomplete nodal dissection
Should have I131
ATA pediatric high risk group
- Extensive N1b nodes
- Locally invasive disease (T4)
Should have I131
Advantages Ga68-EDTA PET/CT compared with gamma camera renal imaging
- Better SR
- Better temporal resolution
- Quantification more accurate and quantitiave
Advantages Ga68 V/Q imaging
- Better SR
- Improved sensitiivity
- Quantification
- Respiratory gating of the PET
Potential PET tracers for protate CA and targets
- FDG
- C11/F18 acetate (lipid metabolism)
- Choline (lipid metabolism)
- C11-methionine (AA transport)
- Ga68-PSMA (PSMA antibodies)
- F18-FDHT (androgen receptor)
- F18-FLT (DNA/Cell proliferation)
- F18-NaF - Calcium analog (binds to hydroxy group, incorporated into hydroxyappetite)
CT truncation artifact
when anatomy extends beyond the axial field of view of the scanner (typically 50 cm) and is common in CT whole-body imaging
CT truncation effects can propagate to PET by causing regions of overcorrection and undercorrection of attenuation in the arms.
Physiologic distribution of Choline
Low level brain
SG
Liver and pancreas most intense
Excretion via GU so kidneys, ureters, bladder hot
Abnormal focal brain = meningioma or high grade glioma
Suspect peripheral osteomyelitis - correct tracer choice?
If no ORIF hardware or surgery > 6 months -> FDG
If ORIF and hardware < 2 years old -> WBC
if ORIF and hardware > 2 years old -> bone scan +/- WBC
Suspect hip prosthesis infection, - correct tracer choice?
If placement < 2 years WBC
If > 2 years, bone scan +/- WBC
Suspect knee prosthesis infection, - correct tracer choice?
If placement < 5 years WBC
If > 5 years bone scan +/- WBC
Suspect spondylodisciitis
FDG
Absorbed dose
energy imparted by ionizing radiation per unit mass of irradiated material (Gy)
Collective dose
The sum of the individual doses received in a given period by a specified population from exposure
to a specified source of radiation.
Annual limit on intake
The derived limit for the amount of radioactive material allowed to be taken into the body of an adult
worker by inhalation or ingestion in a year.
Unrestricted area
Dose rate does not exceed 0.02 mSv/hr
Activity limit for Classification of a Major Spill
Tc = 100 mCi TI201 = 100mCi I123 = 10 mCi Ga67 = 10mCi In111 = 10 mCi I131 = 1 mCi
Law of Bergonie Tribondeau
Radiosensitivity of living cells proportional to rate of division and inversely proportional to their degree of specialization
Stage of gestation, possible effect of radiation
3-4 weeks = death
4-8 weeks = death, growth retardation, anatomic malformations
8-15 - weeks = growth retardation, microcephaly, MR, anatomic malformations
16-40 weeks = growth retardation, decreased brian size, MR
Hypoxia imaging agents
FAZA
FMISO
Two radioimmunoconjugates in clinical use
Y90-Zevalin; Pure beta 2.29 MeV Path length = 5 mm Half life = 64 hrs No isolation required Dosimetry not requred
I131-Bexar Gamma (364) + beta 606 kev Path length 0.8 mm Half life 8 days Isolation required Dosimetry required
Tumours expressing somatostatin receptors
SCLC GI and pancreatic tumours CNS malignancies Breast Prostate
Goals for MAA study prior to radiomicrosphere therapy
- Identify/quantify intrahepatic shunting to lungs
- Extrahepatic GI uptake due to vascular connection
- Blood flow ratio to tumour vs normal parenchyma
CANMEDS ROLES
- Medical Expert - central role
- Communicator - relationships with physicians and patients
- Collaborator - work effectively with other health care providers to provide patient centred care
- Leader - Contribute to a high quality health system
- Health Advocate - use their influence to improve health
- Scholar - lifelong commitment to continuous learning and teaching
- Professional - ethical practice, high personal standards of behaviour
Accuracy
Degree to which a variable represents what it is suppose to represent; affected by systematic error/bias
Precision
Degree to which a variable can be repeated (affected by random error - variance)
ROC curve
True positive rate vs false positive rate (sn vs 1-sp) for a binary classifier system as the disrimination threshold is changed
Odds ratio
= (EE/EN)/(CE/CN)
EE = experimental events EN = Experimental non events
C = control
Observational study designs
No intervention
Cross sectional, cohort, case control, case series
Cross sectional
Determines prevalence; all measures made at one point in time
No distinction between cause and effect
Selection bias
“patients who participate in screening may have more indolent cancers”. Systematic error due to a non-random sample of a population causing some members of the population to be less likely to be included than others resulting in a biased sample
Length time bias
Periodic screening finds slower growing cancers
Therefore patients with tumors detected by means of screening will have better prognosis.
Lead time bias
Lead time bias – “cancer may be found earlier, but the time of death is unchanged”.
Recall bias
Recall bias - type of systematic bias which occurs when the way a survey respondent answers a question is affected not just by the correct answer, but also by the respondent’s memory
Dose Length Product
CTDI x scan length (cm); approximates the total energy imparted to the patient (mGy cm)
CT Dose Index (CTDI) - mean absorbed radiation dose over total volume scanned (Gy); obtained by phantom measurements
Heterogeneous flood field causes
- Inadequate mixing of radiopharmaceutical
- Loss of coupling between crystal and PMT
- Incorrect PMT voltate correction
