ARRT Nuclear Medicine Technology (N) Cheat Sheet

Patient Care

12% of exam
Informed Consent HIPAA Standard Precautions Allergic Reactions

Safety

12.5% of exam
Radiation Protection Cardinals NRC Dose Limits Posting & Area Classifications Survey & Dosimetry Instruments

Image Production

16.5% of exam
Collimator Types Gamma Camera QC PET/CT & SPECT Terms Health IT & Informatics

Procedures

59% of exam
Radionuclide Table Cardiac Procedures Endocrine & Oncology GI & GU Procedures Other Imaging Generator & 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 PA

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 SA

Time, Distance, Shielding = ALARA
Time: minimize duration Distance: inverse square law Shielding: match radiation type ALARA: as low as achievable

Radiation Area vs High Radiation Area SA

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 SA

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 SA

Public -> Occupational -> Eye -> Skin
Public: 100 mrem/yr Occupational: 5 rem/yr Eye: 15 rem/yr Skin: 50 rem/yr

Photoelectric Effect vs Compton Scattering SA

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) SA

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 SA

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 SA

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 SA

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 IM

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 IM

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 IM

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 IM

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 IM

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 IM

DICOM Transmits/stores medical images
HL7 Exchanges orders and reports
PACS Archives and displays images
RIS Scheduling, orders, and reporting

Half-Life Order PR

F-18 -> Tc-99m -> I-123 -> Mo-99
F-18: 110 min Tc-99m: 6 hours I-123: 13 hours Mo-99: 66 hours

Constancy vs Accuracy PR

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 PR

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 PR

Tc-99m 6 h, 140 keV IT decay; workhorse agent
Mo-99 66 h, generator parent β⁻ decay to Tc-99m
I-123 13 h, 159 keV EC decay; diagnostic thyroid
I-131 8 d, 364 keV β⁻/γ; thyroid ablation
F-18 110 min, 511 keV β+ decay; PET FDG
Ga-67 78 h, 93/184/300 keV EC decay; infection, tumor
In-111 2.8 d, 171/245 keV EC decay; tumor, infection
Tl-201 73 h, 69-83/167 keV EC decay; cardiac perfusion
Xe-133 5.24 d, 81 keV β⁻/γ; lung ventilation
Lu-177 6.65 d, 208 keV β⁻ decay; PRRT, PSMA
Y-90 64 h, pure beta No primary gamma photon

Dose Calibrator QC PR

C-A-L-G: Constancy, Accuracy, Linearity, Geometry
Constancy: daily check Accuracy: install, annual Linearity: install, quarterly Geometry: install only

Linearity vs Geometry PR

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 PR

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 PR

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 PR

I-123 diagnoses; I-131 treats
I-123: 13h imaging I-131: 8d therapy Low-iodine diet: before I-131 TSH stimulation required

Free vs Hydrolyzed-Reduced Tc PR

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 PR

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 PR

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 PR

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 PR

MAG3

Tubular secretion
High extraction efficiency
Preferred, poor function

DTPA

Glomerular filtration
Calculates GFR
Normal renal function
Secretion vs filtration

Endocrine & Oncology Procedures PR

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 PR

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 PR

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 PR

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

ARRT Nuclear Medicine

Practice Questions 270 questions Study Guide 36 topics Cheat Sheet 99 facts Flashcards 50 cards Videos 1 video Blogs 1 blog Free CE Podcast