Lecture 10- Nuclear Medicine Flashcards
nuclear med technologist vs nuclear med advanced associates
- tech: bachelor degree; (CNMT) NMTCB or (RT (N)) ARRT accredited
- assoc: midlevel provider for NMAA; masters degree
principles of nuclear medicine
- physiologic vs structural imaging
- radiopharmaceuticals (radiotracers; energy spectrum; half-life)
describe radiotracers
radioactive element bound to pharmaceutical
describe the energy spectrum
- gamma radiation (diagnostic)
- beta/alpha (therapeutic)
contraindications for radiopharmaceuticals
- allergy
- hx of adverse rxns (rare, but include erythema, edema, fever)
isotopes used
- 99m TeO4 (most common)
- Xe133 (xenon gas)
- T1201 (thalium)
- I131, I123 (iodine)
- Ga67 (gallium)
- In111 (indium)
radiation exposure with nuclear imaging
- similar to CXR
- one dose for as many films as needed
- gamma rays emitted in all direction
safety components for techs
- time
- distance
- shielding
Image Acquisition
- planar imaging
- SPECT 3D imaging
- Pb (lead) collimator (parallel apertures allows gamma rays) (NOT NEEDED IN NEWER TECH)
- gamma rays hit scintillation crystal
- crystal converts gamma energy to electronic signal (or light)
- cumulative “photo”
Image Resolution
- ability to distinguish 2 different points as such
- high resolution scans require high res collimator, longer acquisition time
sensitivity of images
- ability to pick up gama signal
- high sens scans (low res/high sens collimator; shorter acquisition time)
artifact sources
- affecting apparent distribution (uptake)
- Attenuation: decrease in intensity gamma ray energy
- Scatter: gamma ray changes its path
Image processing/manipulations
- regions of interest: placed by technologist
- reconstruction: SPECT requires; time required to reconstruct
- manipulations can introduce artifact
quality control
- cameras: daily flood field testing
- isotope generators
- radiopharmaceuticals
image interpretation
- read by physician
- hot (increased) or cold (decreased) uptake
ordering studies
- chronological order is important as isotopes need time to decay
- ex: barium, IV contrast will introduce artifacts
how to indicate emergent scan needed?
asteriks ( * )
common studies
- bone scans
- nuclear cardiology (MUGA-ECG gate, exercise MUGA, stress thallium/cardiolite)
- liver/spleen (replaced by US, not common anymore)
- hepatobiliary
- thyroid scan/uptake
- SPECT brain
- V/P or V/Q scans
- VCUG
- renal
- blood flow images (testicular scans, GI bleeds)
Bone Scans
- Planar or SPECT bone
- used to r/o mets, Paget’s (hot spots), avascular necrosis (e.g. femoral neck; cold)
- isotope: 99mTc MDP IV with imaging 4 hours later; inject L wrist; renal clearance of isotope
- look for symmetry; darker spots are increased upate (thick bone, closer to camera, hypermetabolic)
Bone scan film orientation
- Right Anterior Left
- Left Posterior Right
- Cephalad is top of film
- Caudal is bottom
peds bone scan tips
- growth plates darker
- need to give med to block thyroid
- increased uptake in L fibula is most likely a tumor!
why bone scan over XR?
- Catch stress fx earlier than X ray
- Similar concepts for osteomyelitis
- Function changes earlier detected over Xray structural changes
3 phases of a bone scan
- 1: blood flow
- 2: blood pool
- 3: bone imaging
during which phases are following things visible:
* cellulitis
* acute fx/osteomyelitis/loose prosthetic joints
* chronic fx
- cellulitis: phase 1/2
- acute fx/osteomyelitis/loose prosthetic: phase 1/2/3
- chronic fx: none
FUO/Infection
Method 1
* Gallium 67 via IV to r/o osteomyelitis
* image at 24, 48, 72 hrs (96) post infusion
Method 2
* 111 labeled WBCs via collecting pt’s blood, WBCs isolated, radiolabeled, reinjected
* image at 24, 48, 72 hrs
Method 3
* Ceretec HMPAO for same day imaging
Nuclear Cardiology
- echos have replaced but:
MUGA- LV study
* Multi gated acquisition (EKG gated)
* Images Blood Pool; typically 3 view; can view Cardiac wall motion (hypokinesia, akinesia, dyskinesia) and Ejection Fraction (normal is 45-65%)
MUGA for Cardiology
- 99mTc PYP labeled RBCs
- 20 mCi
- IV injection of PYP (pyrophosphate) tags to RBCs
- IV injection 20 min later of 99mTcO4- tags to PYP
- Or ultratag kit - 1 bottle with all reagents
MUGA interpretation
- Septum appears “cold”
- Anterior
- “Best septal” or LAO (left anterior oblique)
- Used to calculate EF
- L lateral images
- Series of 3 different orientation “cine” pictures
- Additive collection of radioactive particles over and over again to make pictures for movie
Abnormal MUGA
- “Flatter” graph
- Decreased EF
- End Diastole and End Systole pictures
- Not much change in size
- This is LAO or best septal view
First pass MUGA
- One chance only for Right Ventricle study
- Left heart will “cover” right heart after “first pass” in circulation
- RV: Normal RVEF=45-55% (10% less ish than LV)
- Utilizes butterfly or other IV access (pertechnetate bolus w pt under camera and Blood flow imaged)
Exercise MUGA
- Modified bicycle table or other device
- Increase work load (can be done w Echo)
- Normally see LVEF increase with exercise
- Wall motion changes
- (Similar to stress echo)
- Can be done with pharmaceuticals to mimic “stress”- EG persantine
Nuclear cardiology stress test
- r/o CAD w SPECT
- Stress Component: Image after exercise protocol completed, LV seen
- Rest Component: Either several hours after exercise (using Thallium- a K+ analog) or first with Cardiolite (pertechnetate derivative); May see RV faintly (Tl)
use ot Tl (or TCO4 agents)
- Same views as MUGA
- Anterior
- LAO (see donut w/o “bite”)
- L Lateral
Liver/Spleen Scan
- Less common due to US
- 99mTc Sulfur Colloid 4 mCi
- Taken up by macrophage Kuppfer Cells of RES thus, does NOT image hepatocytes!
- Homogenous uptake normal
Hepatobiliary Scanning
- r/o biliary obstruction
- Aka HIDA or PIPIDA, DISIDA
- Choletch/mebrofenin: excreted through biliary system
- 99mTc HIDA 4-8 mCi dose: can be adjusted for abnormal LFTs
- should visualize GB by 45-60 min; should visualized SI by 2 hrs
- EF of GB can be calculated after dose of med
GI bleed/Meckel’s Diverticulum
- Labeled RBCs
- Figure of bleed distal descending colon
Gastric Emptying
- Sulfur colloid scrambled eggs for solid
- Sulfur colloid in liquid
- Can follow GI transit time
- Gastroparesis
- E.g. Diabetic
Thyroid Scans
- Pertechnetate
- Iodine isotopes
- Thyroid uptake
- HOT vs COLD nodules
- Cold may be malignant or a cyst; US can help
SPECT Brain uses
- Cerebrovascular Disease
- Ischemia CVA identified earlier than CT
- Brain death
- Dementia evaluation
- PET brain scans “higher tech”
SPECT brain investigations
- DAT (Dementia of Alzheimer’s Type)
- Epilepsy
- Schizophrenia
Brain SPECT views
- Transverse (superior to inferior)
- Coronal (ant to post)
- Sagittal (L to R)
V/P or V/Q scans
- R/o PE (pulmonary embolism)
- Ventilation phase: Xe 133 gas, Tc99m DTPA aerosol (captures inspiration, equilibrium, washout)
- Perfusion phase: Tc 99m MAA which blocks small capillaries
- Ventilation Perfusion “mismatch” for PE: Ventilation normal –> Perfusion absent area(s)
- If perfusion normal, vent not performed w perfusion first technique
V/P COPD findings
- COPD (loner ventilation washout phase; air trapping)
- Area could be infarcted (no ventilation or perfusion)
Voiding Cystourethrogram
- TcO4 saline via bladder (Filling phase, Voiding phase)
- Measures bladder volume
- Looks for reflux
Testicular Scan uses
- US w doppler has largely replaced
- Acute scrotal pain
- Chronic scrotal pain
- Injury
- Mass
- Torsion
- Note: US usually used
- IV Tc blood flow, pool studies
Thyroid Ablation
high dose oral radioactive iodine
Nuclear Oncology
- Theranostics- molecular imaging/treatment
- (aka theragnostic) alpha or beta emitters
- Palliative or curative therapy goals
- E.g. mets, but not cure primary site
bone met radiotherapy
- palliative
- IV strontium 89
