Radionuclide Ventricular Function Imaging

Question 1

First pass imaging

High counts
Time-activity curve gives you VOLUMES and accurate EF (calculated somehow)

Highest temporal resolution of all techniques (most frames per second)

Time activity curve is vacillating peaks and valleys with each heartbeat, assuming good fast bolus, and regular rhythm;
Needs to look like this to get accurate study info

Usually RAO projection (not great for RWMAs bc no lateral wall in there)

Can do rest and stress:
Look to see stress EF increase by at least 5% vs rest;
Decline in EF abnormal;
If increases by <5%, it’s indeterminate

If EDV and ESV both go UP at stress, but overall EF increases appropriately, it suggests significant valve regurg

Best technique for RV EF–but need slower bolus if this is you’re main question

Left to right shunts can be detected, and shunt fraction calculated.
(See early re-appearance of activity curve in lungs, before the first pass activity curve completely runs its course)

Answer 1

K

Question 2

Labeled RBC gated blood pool imaging
(Equilibrium RNV, aka MUGA)

In vivo method for tagging:
Some of injected per technetium binds elsewhere: salivary glands, thyroid, stomach

65-85% labeling efficiency

Modified in vivo:
Draw pts blood and introduce the pertechnetate into the syringe

85-90% efficiency

Kit labeling:
95% efficiency

Answer 2

K

Question 3

ERNV (MUGA)

high reproducibility (both inter-, and intra-observer)…better than echo for serial EF monitoring

Guidelines for doxorubicin

If start with normal EF (50%):

Stop chemo if EF drops 10% AND reaches 50% or lower

1st scan is within first 100 mg/m2
2nd is btw 250-300 mg/m2
3rd is at 450 mg/m2
Then rescan prior to each chemo dose once you’ve surpassed 450 total dose

If start with abnormal EF (<50%):

Stop chemo if EF drops by 10% OR reaches 30% or less

After baseline MUGA in these abnormal EF pts, you then rescan prior to every subsequent chemo dose

Answer 3

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Question 4

ERNV technique

Start with best septal view = around 45 degrees LAO
LV cavity has to be exactly vertical (see septum clearly down the middle, crescent shaped)

Anterior view = always exactly 45 degrees less oblique from the best septal

Left Lateral view = always exactly 45 degrees more oblique from best septal

You don’t get VOLUMES, as with First-Pass imaging, but rather you get counts (at ED and ES)

32 frames per cardiac cycle, so good temporal resolution

EF = (ED counts) - (ES counts)/ (ED counts) - (Background counts)

Answer 4

K

Question 5

LBBB appearance in ERNV

Dyssynchrony: RV contracts first, then LV
Can see this in the phase histogram–instead of RV and LV peaks being nearly simultaneous, you see 2 distinct peaks (first RV, then LV)

Can determine rate of diastolic filling from the counts vs time curve;
The counts per time curve is transformed into its first derivative curve–this gives you filling rate

Answer 5

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Question 6

Sources of error in ERNV

Misorientation of LV:
If not true best septal positioning, you can get LA overlap with LV and erroneously include LA counts (hence overestimate LV end-systole volume)

Gating issues:
If gate on R and T–“systole” counts changes negate each other (one positive, one negative)–EF is 0%

If gate only on T waves bc they’re higher amplitude than QRS–every “systole” shows negative counts changes (bc they’re actually increasing when should be decreasing)–get negative EF

Answer 6

K

Question 7

SPECT RNV

Best for looking at RWMA (best spatial resolution)

But lowest temporal resolution (8-16 frames per cardiac cycle), so not as precise for EF assessment–hence not used for chemo monitoring

Answer 7

K