MIP imaging and processing and Radiopharmacuticals with procedures

What are the two main reasons we would perform planar MPI imaging over SPECT?

if pt is claustrophobic or exceeding weight limit of SPECT table

How is the gamma camera set up for planar imaging? (what FOV, and collimator do we use?)

SFOV or LFOV with zoom

LEAP collimator for Tl, or LEHR for Tc

T/F: when performing planar imaging, both sets of images should be acquired in the same way (positioning, angles)

true

Why is it important that both sets of planar images images be acquired in the same way

so that they’re comparable

What are we looking at with MPI(myocardial perfusion imaging)

blood flow to left ventricle

How do we position the patient for MP imaging?

either both arms or left arm over head

pt should be made as comfortable as possible

can be imaged supine, prone, or decubitis position

If we were imaging the patient in a decubitis position, which side should they be laying on?

right side (so that left side is up)

What is the benefit of imaging a patient in a prone position?

helps eliminate diaphragm artifact

What types of planar views are we acquiring during MPI?

anterior

LAO (45-55 degree)

left lateral (90 degree)

Why do we acquire LAO (45-55 degree) planar views?

best for septal visualization

What is the idea patient positioning for L. lateral planar views and why?

decubitus - decreases diaphragm attenuation, which can cause false postiive defect in inferior wall of L. ventricle

What view of the heart is represented in this image?

anterior

What view of the heart is represented in this image?

LAO (left anterior oblique)

What view of the heart is represented in this image?

Left lateral

What view of the heart is represented in this image?

anterior

What view of the heart is represented in this image?

LAO (left anterior oblique)

What view of the heart is represented in this image?

Left lateral

When do we begin our first set of Tl-201 planar images? Are we taking stress or rest images.

5-10 min post-injection

stress

What is the imaging parameters for Tl-201 planar images?

30% window centered over 72keV

• optional 20% window on 167 keV

128×128 matrix

minimum 600,000 counts/image or 8min/image

When would we perform redistribution planar images when using Tl-201?

3-4 hrs post injection

What view is shown in A?

anterior

What view is shown in B?

LAO (30 degree)

What view is shown in D?

left lateral

When do we begin stress imaging when taking Tc planar images?

15-60 min after stress injection

When do we begin rest imaging when taking Tc planar images?

30-90min after rest injection

What is the energy window for tc planar imaging?

20% window over 140keV

When performing planar MPI images, we take ___min/images, or ___min/image if gated.

5, 10

How are planar MPI images processed?

Side-by side display of background subtracted and smoothed stress and rest or redistribution images

if using Tl-201 - Heart lung ratio can be calculated

When processing Tl-201 planar images, what does a high heart-lung ratio likely indicate?

greater chance PT has CAD

This is a photo of a planar Sestamibi MPI image, what might the circled object be?

Liver (MPI tc agents leave body thru liver)

How many images are acquired each stop in gated SPECT imaging?

8 images at each stop then put together in composite to make beating heart

What triggers data collection during gated SPECT imaging?

R-wave of ECG

What can be assessed with gated SPECT acquisition

wall motion

wall thickening

estimate of EF

ventricular volume

How is gated data useful?

helps differentiate true perfusion defect from attenuation

Female with fixed defect in anterior wall

• if it’s MI or breast attenuation

How can gated data be used when determining if its MI or breast attenuation?

if wall motion and thickening are normal in anterior wall, physician can confidently interpret study as being normal with attenuation artifact

What is the gamma energy level for Tl-201 SPECT imaging?

very low gamma energy (68-80keV)

What is the physical half-life of Tl-201?

73.1 hr

How is Tl-201 produced?

in a cyclotron

How many injections are given during a Tl-201 SPECT imaging? What is the dose?

1 injection

3-4mCi

In what order are the rest/redistribution and stress images performed using Tl-201 SPECT imaging

Stress-rest protocol only

When is the pt placed under the camera immediately after stress?

immediately after stress

What is the general Tl-201 SPECT imaging protocol?

Typically 1 injection used (3.0-4.0 mCi)

Stress-Rest protocol only

Patient placed under camera immediately after stress

3-hour rest period required before delay images

Redistribution begins at about 10-15 minutes post injection

What is the mechanism of uptake of Tc-Sestamibi?

mitochondria of myocardium

Which Tc agent has a higher extraction fraction, Sestamibi or Tetrofosmin?

Sestamibi

What is the benefit of using Tc agent Tetrofosmin over Sestamibi

Tetrofosmin has faster liver clearance, can image quicker

T/F: uptake of Tc agents is dependent on mitochondrial membranes

True

T/F: Tc agents have minimal redistribution, especially compared to Tl-201

true

What is the major pathway for clearance of Tc agents?

hepatobilliary system (liver)

What is the general dose range for Tc-99m agents?

10-30mCI

How does the dosage differ when using Tc-99m in a 1 day protocol?

2nd dose is 3 times that of first

• ex. if first dose was 10mCi, 2nd dose is 30mi

When imaging patients with a large body habitus using Tc-99m, is a 1-day or 2-day protocol better?

2 day

If performing a 2 day protocol using Tc-99m, is it more ideal to perform the stress or rest first?

stress

If we wanted a TRUE rest image, should we perform the stress or rest images first?

rest

What is the protocol for a Dual isotope imaging protocol? (dose, timings, processing precautions)

3mCi Tl-201 - rest images

• wait 10-15min

20-30mCi Tc-99m agent - stress images

• wait desired time

processing - use different filters

For all protocols, what are the two most important things to remember?

all counts count

ALALRA

What types of protocols can we perform using Tc-agents only?

1 day R/S - Tc99m (most typical)

1 day S/R - Tc99m

2 day - Tc99m (preferred for obese patients)

What protocols use Tl (not exclusively)

1 day Tl only

1 day dual isotope Tl/Tc99m

What are the indications for myocardial perfusion imaging?

Assessment of the presence, location, extent, and severity of CAD

Risk stratification of patients after MI

Risk stratification before non-cardiac surgery in patients with known CAD or high risk factor of CAD

What is the patient prep for MPI?

NPO for 4 hrs

no caffeine 12 hrs before the stress test

certain medications may need to be stopped for stress test

• i.e. beta blockers

What is the general protocol for a 1 day R/S Tc-99m stress test?

inject low dose at rest [8-10mCi]

• wait 30min for myoview, 45min for Mibi

image rest

stress test

• inject high dose [24-30mCI] at peak exercise or peak coronary vasodialation

wait 30-45 min

image stress

process images

always review images for movement and artifacts (bowel or liver interference)

What should MPI images always be reviewed for before releasing patients?

movement and artifacts (from bowel or liver interference)

What is the general protocol for a dual isotope Tl/Tc protocol?

inject Tl at rest

• wait 20min

image rest

Stress: inject high dose of Tc-99m agent (24-30mCi) at peak exercise or peak coronary vasodilation

image stress

always review images for movement and artifacts (from bowel or liver interference)

Describe the 1 day protocol using Tl

 Inject 3-4mCi TL at peak exercise or peak coronary vasodilatation

 Wait 10min

 Image Stress

 Wait 4hours

 Image Rest

Describe a 2 day protocol using Tc-99m agents

Day 1

• Inject high dose of Tc99m agent (24-30mCi) at peak exercise or peak coronary vasodilatation 

• Wait 30-45min

• Image Stress

Day 2

• Inject low dose at rest (24-30mCi)

• Wait 30min for myoview

• Wait 45min for Mibi

  • Image Rest

What tracer/agent protocol is best for image quality?

Dual tracer protocol using Tl for stress and Tc for rest

Why is the Dual tracer protocol (Tl/Tc) best for best image quality?

◦Has a better extraction fraction w/TL

◦Maximizing dosage

◦Saves money

What are the downfalls of a Dual tracer protocol (Tl/Tc)?

◦Increased radiation exposure

◦Lots of scatter radiation in the body

◦Motion after stress

◦Long study

Which is preferred in a SPECT image study, circular or elliptical orbit?

elliptical orbit

Are SPECT images typically acquired in 180 degrees or 360?

180

When acquiring images for Tl SPECT study in step-and-shoot mode, for how long is each image acquired? (answer in ___sec/stop)

40 sec/stop

When acquiring images for Tc-agents SPECT study in step-and-shoot mode, for how long is each image acquired? (answer in ___sec/stop)

20-25 sec/stop

What are the different methods of attenuation correction?

transmission source

CT

computer based programs

none

What is a flood uniformity correction?

correct images for uniformity by applying flood correction

What is involved in SPECT imaging processing?

define reconstruction boundries

manually draw line thru heart cavity parallel to long axis of ventricle

reconstruction performed w/ either back-projection or iterative reconstruction

What would happen if the long axis of the ventricle is selected incorectly during SPECT image processing?

reconstructed images and polar plots will be distorted

What is the purpose of image filters?

enhance resolution and supress noise

What plane is A?

horizontal long axis

From what to what is A “slicing”?

from inferior to anterior [superior]

What plane is B?

Short axis

From what to what is B “slicing”?

from apex to base

What plane is C?

Vertical Long axis

C is slicing ___ to ___ (hint-anatomical directions/landmarks)

medial to lateral (septal to lateral)

What type of slice is A?

top transaxial

What slice is B?

vertical long axis

What slice is C?

Horizontal long axis

What slice is D?

Short axis

Which artery supplies the septum?

left anterior descending

Which artery supplies the apex?

left anterior descending

Which artery supplies the anterior wall of the heart?

left anterior desending

Which artery supplies the lateral wall of the heart?

circumflex

Which artery supplies the inferior wall?

Right main coronary

What are the other types of plots we can generate for MPI?

reversibility plot

blackened pixel plot

standard deviation plot

What is the purpose of a quantitative polar plot?

provides way to visualize entire left ventricle in one image

analysis of SPECT data can detect and/or verify perfusion abnormalities

What are volume images?

3d images that allows for surface of heart to be viewed in systole and diastole

Can we generate volume images without gated imaging?

no - need gated info to generate volume images

What is the purpose of a reversibility plot?

generated to show extent of reversibility

What is the purpose of a blackened pixel plot?

shows which areas are greater than a specified standard deviation below the mean

What is the purpose of a standard deviation plot?

color codes myocardium based on number of standard deviations below the mean of the normal database

What are the two types of Radiopharmaceuticals we can use for a cardiology procedure?

Thallium-201 chloride

Tc-99m labeled agents`

What is the extraction Fraction?

amount of radioisotope taken up in myocardium the first pass thru the heart