Patient Care
12%of exam
Informed ConsentHIPAAStandard PrecautionsAllergic Reactions
Safety
12.5%of exam
Image Production
16.5%of exam
Procedures
59%of exam
Radionuclide TableCardiac ProceduresEndocrine & OncologyGI & GU ProceduresOther ImagingGenerator & Radiopharmacy QC
Quick Facts
- Exam
- ARRT NMT (N)
- Credential
- Nuclear Medicine Technology
- Time
- 230 min (250 total)
- Pass
- Scaled score 75
- Fee
- $225
- Questions
- 230 (200 scored)
- Provider
- Pearson VUE
- Blueprint
- Jan 1 2022
Patient Care Essentials
- Informed consent
- Physician explains; tech witnesses
- HIPAA minimum necessary
- Access only what's needed
- Chain of infection
- 6 links; break one
- Standard precautions
- All patients; PPE by exposure
- Early allergy signs
- Urticaria, pruritus, flushing
- Metformin and FDG PET
- Hold ~48h before scan
Cardinal Principles
Time, Distance, Shielding = ALARA
Time: minimize durationDistance: inverse square lawShielding: match radiation typeALARA: as low as achievable
Radiation Area vs High Radiation Area
Radiation Area
- Over 5 mrem/hr
- At 30 cm
- Standard posting required
High Radiation Area
- Over 100 mrem/hr
- At 30 cm
- Stricter access control
20x higher threshold
Radiation Protection Cardinals
- Time
- Minimize exposure duration
- Distance
- Inverse square law falloff
- Shielding
- Match material to radiation
- ALARA
- As low as reasonably achievable
- Deterministic effects
- Threshold dose; severity increases
- Stochastic effects
- No threshold; only probability increases
NRC Dose Limits
Public -> Occupational -> Eye -> Skin
Public: 100 mrem/yrOccupational: 5 rem/yrEye: 15 rem/yrSkin: 50 rem/yr
Photoelectric Effect vs Compton Scattering
Photoelectric
- Low-energy photon absorbed
- Ejects inner-shell electron
- No scatter produced
Compton
- Higher-energy photon interaction
- Ejects outer-shell electron
- Main source of scatter
Absorption vs scatter
NRC Dose Limits (10 CFR 20)
- Occupational whole-body
- 5 rem (50 mSv)/year
- Public dose limit
- 100 mrem (1 mSv)/year
- Declared pregnant worker
- 500 mrem per gestation
- Lens of eye
- 15 rem (150 mSv)/year
- Skin extremities
- 50 rem (0.5 Sv)/year
- Minor worker (under 18)
- 10% of adult limits
GM Counter vs Ionization Chamber
GM Counter
- Highly sensitive
- For low-level contamination
- Saturates at high dose
Ion Chamber
- Less sensitive
- Accurate at high dose
- For area, spill surveys
Low-level vs high dose-rate
Posting & Area Classifications
- Radiation area
- Over 5 mrem/hr at 30cm
- High radiation area
- Over 100 mrem/hr at 30cm
- Very high radiation area
- Over 500 rad/hr at 1m
- Restricted area
- Access controlled for protection
- Controlled area
- Occupational dose is managed
- Airborne radioactivity area
- Airborne concentration limits exceeded
Survey & Dosimetry Instruments
- GM counter
- Low-level contamination; saturates high-dose
- Ion chamber
- Higher dose rates; less sensitive
- Well counter
- In vitro samples; high sensitivity
- Thyroid probe
- In vivo uptake; collimated NaI
- Pocket dosimeter
- Real-time direct-reading personal dose
- TLD/OSL badge
- Cumulative personnel dose record
SPECT vs Planar
SPECT
- 3D tomographic imaging
- Multiple angle views
- Better contrast resolution
Planar
- 2D single view
- Faster acquisition time
- Whole-body screening
Depth vs speed
Image Artifact Troubleshooting
- Cold or hot spot→Check PMT/crystal(Recalibrate camera)
- Nonuniform flood, edge packing→Reset energy window(Off-peak photopeak)
- Blurred edges, streaking→Repeat acquisition(Patient motion)
- Star-pattern artifact→High-energy collimator(Septal penetration)
- Ring artifact on SPECT→Update uniformity map(Detector nonuniformity)
- Missing outer body (PET/CT)→Extend CT field(Truncation artifact)
- Photopenic rim at edges→Re-register CT/PET(Attenuation misalignment)
- Diffuse extra-osseous uptake→Check free pertechnetate(Poor labeling)
Collimator Types
- Parallel-hole
- General purpose; no magnification
- Pinhole
- Magnifies small superficial organs
- Converging (fan-beam)
- Magnifies; smaller field size
- Diverging
- Minifies; wider field coverage
- LEHR
- Best resolution; longer scan time
- ME/HE collimators
- For I-131, higher-energy isotopes
Gamma Camera QC
- Uniformity (flood)
- Daily; extrinsic or intrinsic
- Center of rotation
- Weekly; SPECT cameras only
- Resolution/linearity
- Monthly; bar phantom test
- Multi-window registration
- Quarterly; dual-isotope alignment check
- Energy resolution
- Acceptance testing; annual verification
PET/CT & SPECT Terms
- Attenuation correction
- CT density corrects photon loss
- SUV
- Standardized uptake value; tumor metric
- Coincidence detection
- Two 511 keV photons simultaneously
- Iterative reconstruction
- OSEM; better noise than FBP
- Filtered back projection (FBP)
- Older method; streak artifacts
- CTAC artifact
- Metal, contrast, or motion misregistration
- Matrix size
- Pixel grid; affects resolution
Health IT & Informatics
- DICOM
- Transmits/stores medical images
- HL7
- Exchanges orders and reports
- PACS
- Archives and displays images
- RIS
- Scheduling, orders, and reporting
Half-Life Order
F-18 -> Tc-99m -> I-123 -> Mo-99
F-18: 110 minTc-99m: 6 hoursI-123: 13 hoursMo-99: 66 hours
Constancy vs Accuracy
Constancy
- Daily check
- Cs-137 reference source
- Detects day-to-day drift
Accuracy
- Install + annual check
- NIST-traceable source
- Confirms true activity
Drift check vs true value
Radiopharmaceutical Selection by Indication
- Thyroid uptake or Graves→I-123(Oral capsule)
- Thyroid ablation or therapy→I-131(High-dose therapy)
- Myocardial perfusion imaging→Tc-99m sestamibi/tetrofosmin(Or Tl-201)
- Bone metastases survey→Tc-99m MDP(3-phase for infection)
- Acute cholecystitis workup→Tc-99m mebrofenin (HIDA)(Nonvis at 60 min)
- Parathyroid adenoma localization→Tc-99m sestamibi dual-phase(Delayed washout)
- Neuroendocrine tumor imaging→Ga-68 DOTATATE(Replaced OctreoScan)
- Pheochromocytoma or neuroblastoma→I-123 MIBG(Block thyroid first)
- GFR calculation needed→Tc-99m DTPA(Glomerular filtration)
- Poor renal function→Tc-99m MAG3(Tubular secretion)
Radionuclide Table
- Tc-99m
- 6 h, 140 keVIT decay; workhorse agent
- Mo-99
- 66 h, generator parentβ⁻ decay to Tc-99m
- I-123
- 13 h, 159 keVEC decay; diagnostic thyroid
- I-131
- 8 d, 364 keVβ⁻/γ; thyroid ablation
- F-18
- 110 min, 511 keVβ+ decay; PET FDG
- Ga-67
- 78 h, 93/184/300 keVEC decay; infection, tumor
- In-111
- 2.8 d, 171/245 keVEC decay; tumor, infection
- Tl-201
- 73 h, 69-83/167 keVEC decay; cardiac perfusion
- Xe-133
- 5.24 d, 81 keVβ⁻/γ; lung ventilation
- Lu-177
- 6.65 d, 208 keVβ⁻ decay; PRRT, PSMA
- Y-90
- 64 h, pure betaNo primary gamma photon
Dose Calibrator QC
C-A-L-G: Constancy, Accuracy, Linearity, Geometry
Constancy: daily checkAccuracy: install, annualLinearity: install, quarterlyGeometry: install only
Linearity vs Geometry
Linearity
- Across activity range
- Install + quarterly
- Catches nonlinear response
Geometry
- Different volumes, containers
- Install only
- Catches volume-dependent error
Activity range vs container size
Pharmacologic Stress Agent Picker
- Standard vasodilator stress needed→Regadenoson(Fixed dose)
- Reactive airway disease→Regadenoson preferred(A2A selective)
- AV block, no pacemaker→Avoid vasodilators(Use dobutamine)
- Recent caffeine or theophylline→Hold before vasodilator(Antagonizes receptors)
- Cannot exercise, no contraindication→Adenosine or dipyridamole(Alternative vasodilators)
- Vasodilator contraindicated→Dobutamine(Inotrope, chronotrope)
Generator & Radiopharmacy QC
- Mo-99 breakthrough
- ≤0.15 µCi/mCi Tc-99m
- Al breakthrough
- ≤10 µg/mL eluate
- Stannous ion
- Reduces Tc for labeling
- Labeling efficiency
- Depends on pH, time, temp
- Radiochemical purity (RCP)
- TLC measures unbound activity
- Elution
- Saline extracts Tc-99m only
Thyroid Iodine Choice
I-123 diagnoses; I-131 treats
I-123: 13h imagingI-131: 8d therapyLow-iodine diet: before I-131TSH stimulation required
Free vs Hydrolyzed-Reduced Tc
Free Pertechnetate
- Unbound Tc-99m
- Thyroid, stomach, salivary uptake
- Signals poor labeling
Hydrolyzed-Reduced Tc
- Under-reduced by stannous ion
- Liver, spleen uptake
- Colloid-like behavior
Both are labeling failures
Dose Calibrator QC
- Constancy
- Daily, Cs-137 source
- Accuracy
- Install + annual, NIST source
- Linearity
- Install + quarterly, activity range
- Geometry
- Install only, varied containers
- Attenuators (liners)
- Match isotope energy range
Stress vs Rest Imaging
Stress
- Pharmacologic or exercise
- Reveals reversible ischemia
- Usually acquired first
Rest
- Baseline perfusion state
- Confirms fixed defects
- Redistribution comparison point
Compare for reversibility
Cardiac Procedures
- Reversible defect
- Stress only; ischemic, viable
- Fixed defect
- Stress and rest; scarred tissue
- MUGA
- ECG-gated; ejection fraction calc
- Sestamibi/tetrofosmin
- Mitochondrial uptake; no redistribution
- Vasodilator stress
- Regadenoson, adenosine, or dipyridamole
- Dobutamine
- Inotrope; used if contraindicated
MAG3 vs DTPA
MAG3
- Tubular secretion
- High extraction efficiency
- Preferred, poor function
DTPA
- Glomerular filtration
- Calculates GFR
- Normal renal function
Secretion vs filtration
Endocrine & Oncology Procedures
- RAIU
- % uptake at set intervals
- Parathyroid scan
- Dual-phase sestamibi; adenoma persists
- Low-iodine diet
- Before I-131; maximizes uptake
- MIBG
- Norepinephrine analog; neuroendocrine tumors
- Ga-68 DOTATATE
- Somatostatin receptor; replaces OctreoScan
- FDG prep
- Fast 4-6h; check glucose
In-111 Pentetreotide vs Ga-68 DOTATATE
In-111 Pentetreotide
- Older SPECT agent
- OctreoScan brand name
Ga-68 DOTATATE
- Newer PET agent
- Higher resolution imaging
Largely replaced by PET
GI & GU Procedures
- Gastric emptying
- Solid meal; 4-hour protocol
- Meckel scan
- Pertechnetate; ectopic gastric mucosa
- HIDA scan
- No gallbladder by 60 min
- GI bleed scan
- Tagged RBCs; detects slow bleeds
- MAG3
- Tubular secretion; poor renal function
- DTPA renal
- Glomerular filtration; calculates GFR
Other Imaging Procedures
- 3-phase bone scan
- Flow, blood pool, delayed
- Brain death study
- No flow; hollow skull sign
- MAA lung perfusion
- Microembolizes capillaries; reduce dose caution
- Xe-133 ventilation
- True gas; closed delivery system
- DTPA aerosol
- Nebulized; uneven obstructed deposition
- Sentinel node mapping
- Sulfur colloid; first-draining node
- Cisternography/shunt patency
- CSF flow; confirms patency, leaks
Common Traps
Constancy vs Accuracy
Constancy checks daily drift ≠ Accuracy confirms true activity value
Radiation Area vs High Radiation Area
5 mrem/hr threshold ≠ 100 mrem/hr threshold
Free vs Bound Pertechnetate
Free causes thyroid, stomach uptake ≠ Bound stays on kit ligand
Reversible vs Fixed Defect
Reversible resolves at rest ≠ Fixed persists at rest too
I-123 vs I-131 Use
I-123 is for diagnosis ≠ I-131 is for therapy
GM Counter vs Ion Chamber
GM for low-level survey work ≠ Chamber for high dose rates
Deterministic vs Stochastic Effects
Deterministic has a dose threshold ≠ Stochastic has no dose threshold
Last Minute
- 1.Tc-99m: 6h, 140 keV
- 2.F-18: 110 min, 511 keV
- 3.I-123 diagnoses; I-131 treats
- 4.Occupational 5 rem; public 100 mrem
- 5.Radiation Area = 5 mrem/hr
- 6.Medical event: 20% + threshold rem
- 7.Mo-99 breakthrough ≤0.15 µCi/mCi
- 8.Constancy daily; accuracy install + annual
- 9.MAG3 = poor function; DTPA = GFR
- 10.SPECT 180° arc for cardiac
- 11.Free pertechnetate = poor labeling
- 12.Y-90 = pure beta, no gamma
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