exam 2 ultra study guide

all three lectures

nuclear cardiology

RPs used to eval cardiac funtion and anatomy

cardiac NM procedures help diagnose…

CAD, myocardial infarction, heart failure

what are the cardiac NM studies

MPI, myocardial viability, MUGA scan, first pass, PET

myocardial perfusion imaging (MPI)

evaluates blood flow to the heart muscle

can be PET or SPECT

what isotopes used for MPI

SPECT: Tc99m sestamibi/tetrofosmin (cardiolite, myoveiw)

PET: Rb82 chloride or N13 ammonia (NH3)

blood supply is ___ proportional to blood flow

directly proportional

MPI: if an artery is blocked, the region of the heart it supplies will…

receive reduced (ischemia) or no (infarct) blood flow

myocardial viability procedures

helps clinicians figure out if heart muscle that isnt working well is still alive and if it can recover w treatment

when are myocardial viabilities usually done?

after pt has a heart attack, or if doctors suspect part of the heart muscle might be damaged

myocardial viability isotopes

SPECT: Tl201 thallous chloride

PET: Rb82 chloride or N13 ammonia

MUGA (multi gated acquisition scan)

aka cardiac blood pool

assesses ventricular function (EF and wall motion)

“how well is the heart pumping blood?”

isotope for MUGA scans

Tc-99m labeled red blood cells

the goal of a MUGA scan is to

measure ejection fraction pumped out of heart w each beat.

also assesses how well muscle contracts/relaxes

MUGA can help to diagnose or monitor…

heart failure, check heart function during chemotherapy (especially w drugs that affect the heart)

first pass radionuclide angiography

captures very first pass of tracer through heart/lungs right after injected into a vein

very quick scan, often a few seconds

first pass radionuclide angiography isotopes used

Tc99m DTPA (pentetate)

Tc99m TcO4 (pertechnetate)

a first pass scan evaluates what four things about the heart?

cardiac function, pulmonary circulation, shunts, ventricular function (including EF, motion, chamber volumes)

PET cardiac imaging

used for metabolic eval and MPI

higher resolution, quantitative capabilities

PET tracers used

MPI: Rb82 chloride or N13 ammonia

metabolic/inflammation: F18 FDG

common indications for cardiac NM scans

CAD, cardiac function eval

what causes CAD

usually atherosclerosis, buildup of plaque in coronaries

CAD can result in what

angina, MI, heart failure

what is evaluated to determine cardiac function

EF (vol of blood pumped out of a ventricle w each beat)

wall motion (normal, hypokinetic, akinetic, dyskinetic)

perfusion defects (ischemia, infarction)

stress testing (adenosine, regadenoson, excercise)

gated imaging

synchronizing physiological occurrence with imaging

ex: monitor heartbeat w EKG during MPI

gating imaging techniques use EKGs to

eval how heart moves and pumps during each beat

the EKG, when hooked up during imaging, tells the camera to…

take images when triggered (at R interval)

gamma camera captures imagest at…

different points in heartbeat, usually divided into 8 or 16 frames per cycle

allows clinicians to see both perfusion + function

gating adds valuable ___ data to perfusion studies

functional data

SPECT is commonly used in MPI because it has been shown to have high ___ and…

high accuracy and incremental prognostic value

MPI indications

diagnosis of CAD, assessment of coronary artery stenosis, assessment of myocardial viability, prognosis post MI, monitoring effects of treatment

what diagnoses can be made after an MPI performed

myocardial ischemia, myocardial infarct, hibernating/stunned myocardium

ischemia

diminished volume of perfusion

infarction

cellular response to lack of perfusion (i.e. heart attack)

contraindications for MPI

pregnant/breastfeeding

recent NM study depending on RP

others depending on stress method (i.e. certain medications)

patient prep MPI

4-6 hr fast

no caffeine/xanthine 12 hrs prior

withhold dipyridamole 48 hrs prior

other meds depending on physician discretion

what focused history aspects of a patient should be acquired before imaging

indications

meds

symptoms

cardiac risk factors

results of prior procedures

MPI protocols- name 4

1 day, 2 day, rest only (pain study), dual isotope

1 day MPI protocol simplified

rest phase: RP IV injection, 45 min uptake, EKG, rest images (supine, arms up), 10 mins

stress: either exercise/meds, RP injection during peak, exercise is 15 min uptake and meds is 45, images (supine, arms up)

prone imaging optional, ~8 mins

1 day protocol: dose values for rest and stress- sodium iodide cameras and czt cameras

Sodium Iodide:

rest- 8-12 mCi (8 rec)

stress- 24-36 mCi (24 rec)

CZT:

rest- 4-8 mCi (rec 4)

stress- 12-24 mCi (rec 12)

the stress dose in MPI is ___ times the rest dose

three times

camera positions for rest/stress 1 day protocol

RAO to LAO (for all cameras)

injection to imaging time for 1 day protocol MPI (all cameras)

stress: 15-60 min after exercise, 30-60 after meds

rest: 30-60 mins after injection

what is the primary purpose of MPI?

to evaluate blood flow to heart muscle

what RP commonly used in SPECT MPI studies?

Tc-99m sestamibi

dose ratio between injections for 1 day protocol

1:3

on the camera, patient should be raised until they are…

isocenter

to avoid artifacts, ensure the activity or counts in the heart appear as…

hot as those in the liver; should be no bowel activity interfering w visualization of the heart

if bowel in the way, delay for adequate clearance if necessary

after rest imaging, and before stressing the patient, what should you always do?

review the rest images to ensure they’re good quality- once patient is stressed, there’s no going back

because MPI is a comparative study, every effort should be made to..

acquire rest and stress SPECT in same fashion (machine, positioning, etc)

best stress method is

exercise

gut activity can cause what to mess up in a scan?

LVEF value will be extremely low

infiltration messes up a scan how?

RP fills at injection site, heart does not get adequate amount of tracer resulting in low counts; tracer will uptake elsewhere (ex. lymph nodes)

how to reduce chances of port retention?

flush with saline well to ensure all of the tracer makes it into bloodstream

attenuation correction is used to reduce…

artifacts

when patient has irregular heart rhythm, what should be done?

non-gated SPECT

what’s a good way to reduce chance of artifacts on MPI positioning-wise?

patient in prone position (moves diaphragm/breast tissue out of the way)

2 day MPI protocol is performed when…

pt has a large body habitus that would result in nondiagnostic, low dose images as part of a low dose single day study

for a 2 day MPI protocol, indications and contraindications are…

the same as the 1 day protocol

2 day protocol MPI dosages range and recommended values: anger cameras

recommended:

stress AND rest doses-

1. BMI >35 = 18 mCi

2. BMI <35 = 8 mCi

range:

stress AND rest doses-

1. BMI >35 = 18-30 mCi

2. BMI <35 = 8-12 mCi

2 day protocol MPI dosages range and recommended values: CZT cameras

recommended:

stress AND rest doses-

1. BMI >35 = 9 mCi

2. BMI <35 = 4 mCi

range:

stress AND rest doses-

1. BMI >35 = 9-15 mCi

2. BMI <35 = 4-6 mCi

2 day protocol MPI camera positioning is

the same as 1 day protocol:

RAo to LAO

in 2 day MPI protocol, what is performed first?

stress portion of test

what is cardiac creep

imaging too early after stress shows cardiac movement of the images

MPI 2 day: for heavier patients, radiopharmaceutical doses may be adjusted….

upward by 0.31 mCi/kg for Tc99m

2 day MPI protocol: if stress scan is normal (day 1), then…

rest imaging not needed

“pain study” (rest only) protocol

when patient is having extreme pain and risk of stress testing is higher; physician will determine if stress should be performed or not following a rest test

what benefits are there from Tl201 compared to Tc99m (in dual isotope imaging)

Tl201 has higher first pass extracting, ability to keep up w blood flows at higher rates and w larger defect sizes at stress

also generally cheaper

Tl201 is a ___ produced isotope and is widely available

cyclotron produced

drawbacks to using Tl201 / dual isotope protocol

radiation is 2-2.5 times greater compared to Tech

highest pt radiation burden of any myocardial perfusion protocols

photon attentuation coefficient 20% higher than tech

high rad burden, lack of Tl201 availability can limit performance of DI protocol

dual isotope MPI protocol: dosage range/rec for Tl201 (REST)

2.5 mCi rec, can range from 2.5-4.0 mCi

dual isotope MPI protocol: Tech range/recommended (STRESS)

24 mCi rec, range is 24-36 mCi

Tl201 injection to imaging time

20 mins after injection

short axis

.

horizontal long axis

.

vertical long axis

.

what is located below the diaphragm

liver, stomach, spleen, kidneys, bowels

if a patient is moving too much…

sinogram will not be smooth

if patient is minorly movement

use motion correction in software

if pt is majorly moving

stop scan, instruct pt not to move

notify physician is movement unable to be controlled

alt option: offer statics

symptoms of CAD often appear during…

exertion

stress only defects are

ischemic and reversable

fixed defects on both stress and rest are

infarcted and might not be reversible

in CAD, bc coronary circulation cannot meet O2 demand, what symptoms may arise

inadequate perfusion leads to chest pain, arm pain, SOB

all stressed patients must do what prior to being stressed?

consent to procedure, sign paperwork

natural stressing (e.g. treadmill) means less..

adverse effects, quick recovery

contraindications to exercise stressing

irregular BP/HR for 48 hrs prior. anything that is not normal like patient is struggling to breath or HR is crazy, etc.

absolute contraindication to exercise stress is if pt has had MI within…

2-4 days

patient prep for exercise stress

NPO 4 hours prior, no physical exertion at least 12 hrs prior

medications that interfere with exercise stress

beta, calcium channel blockers

nitroglycerin

when to discontinue certain medications before exercise stress testing

nitroglycerin - 1 hour

beta/calcium channel blockers - 24-48 hours

12 lead EKG monitoring

only 10 actual leads are placed; check leads for response on the computer

quality stress test (exercise)

12 lead EKG correctly placed

large bore (18-20 G) , preferably in hand

communication w pt and physician during injection

observe rad safety precautions

Bruce protocol (w name)

speed, elevation increase every 3 min

each interval is a “stage” and increases pts workload

modified Bruce protocol

elevation increases slightly every 3 min, constant slow speed

pts w limited exercise capability

exercise stress- radiotracer injected at…

peak exercise, aka 85% of pt’s max predicted HR

85% = 220- pt age

pt should continue to exercise for how long after tracer administration?

1-2 min, to maintain max myocardial O2 demand

when to terminate a stress test?

pt asks to stop

can’t reach peak over extended period

marked ST segment dep

marked ST segment elevation

ventricular/supraventricular tachycardia

prog. decrease in BP

abnormal BP elevation (>250/130 mmHg)

what do stress drugs do to the heart

causes vasodilation or increases myocardial oxygen demand

what are the pharmacological stress agents

dipyridamole (persantine)

adenosine (adenocard)

regadenoson (lexiscan)

dobutamine (dobutrex)

dipyridamole (persantine) mechanism of action, half life

indirect coronary artery vasodilator, increases tissue lvls of adenosine by preventing cell uptake/deamination of adenosine

half life is 30-45 mins

peak vasodilation is 6.5 mins after infusion starts