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Stanford University. PET Myocardial Perfusion Imaging: Protocols and Procedures. George Segall, M.D. PET Perfusion Agents. Diffusible tracers. Radioisotope Form Half-life MeV. Rubidium-82 ( 82 Rb) Chloride 75 sec 3.15 Nitrogen-13 ( 13 N) Ammonia 10 min 1.19

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Stanford University

PET Myocardial Perfusion Imaging: Protocols and Procedures

George Segall, M.D.


PET Perfusion Agents

Diffusible tracers

Radioisotope Form Half-life MeV

Rubidium-82 (82Rb) Chloride 75 sec 3.15

Nitrogen-13 (13N) Ammonia 10 min 1.19

O-15 (15O) Water 110 sec 1.72

Copper-62 (62Cu) PTSM 9.8 min 2.94

Potassium-38 (38K) Chloride 7.6 min 2.70

Carbon-11 (11C) Butanol 20 min 0.96

PTSM, pyruvaldehyde methylthiosemicarbazone


Medicare Coverage Policy

1995 Rb-82 PET for myocardial perfusion

1998 F-18 deoxyglucose PET and SPECT for myocardial viability

2003 N-13 ammonia for myocardial perfusion


Medicare Coverage Policy for

Rb-82 and N-13 ammonia

PET whether at rest alone, or rest with stress, is approved when PET is

• performed in place of SPECT, or

• used following SPECT when results are equivocal, technically uninterpretable, or discordant with clinical care

SPECT may not be used following an inconclusive PET


RAM License

Strontium-82

200 mCi

Rubidium-82

200 mCi

Strontium-85

1000 mCi



Relative Advantages

Rb-82 N-13 ammonia

Availability Excellent Limited

Logistics Easy Difficult

Cost Fixed Variable


Decision Analysis

On-site cyclotron

Occasional Imaging

N-13 ammonia

and

PET/CT capacity

Daily Imaging

Rb-82 chloride

and


Decision Analysis

Flexibility

Exercise

Regadenoson

Adenosine

N-13 ammonia

Dipyridamole

Dobutamine

Convenience

Regadenoson

Rb-82 chloride

Adenosine

Dipyridamole


Scheduling

Rb-82 chloride

N-13 ammonia

scheduled > 1D in advance

• problematic cases

inconclusive SPECT

high BMI

scheduled day of exam

• ED and inpatients


Emission protocol

N-13 ammonia

• 20-30 mCi

• 2D gated emission

• start 10 min p injection

Rb-82 chloride

• 40-60 mCi

• 2D gated emission

• start 90 sec p injection


2D vs 3D Gated Rb-82 PET

Knesaurek. BMC Nucl Med 2007;7:4

16 normal volunteers had resting Rb-82 on a BGO PET camera

Low dose (20 mCi) 3D acquisition compared to high dose (60 mCi) 2D acquisition


Emission Reconstruction

Rb-82 chloride

• reconstruction filter: Butterworth 0.4 roll-off / power 10

• post reconstruction: axial smoothing

N-13 ammonia

• reconstruction filter: Butterworth 0.40 roll-off / power 10

• no post reconstruction smoothing


CT protocol

• 140 keV

• 30-210 mAs (noise index 25.0)

• pitch 0.5

• ungated


PET Perfusion Agents

•Rb-82 Chloride and N-13 ammonia are both extractable agents which passively diffuse across cell membranes

•Both tracers have high first-pass myocardial extraction fractions, which are inversely related to flow is a non-linear manner.


Rb-82 chloride

Tang. Phys Med Biol 2009;54:3161-3171

•Rb-82 is rapidly cleared from the circulation


N-13 ammonia

•N13 is rapidly cleared from the circulation


N-13 ammonia

•N-13 ammonia is trapped in the myocardium from the action of glutamate dehydrogenase1 and glutamine synthetase2

NH3

-ketoglutarate

2

1

13NH4+

13NH3

13NH3

glutamine

glutamate

glutamine

urea


PET Perfusion Agents

Relationship to CBF

Rb-82 Chloride

N-13 ammonia

Schelbert Hr, Schwaiger M. In: PET and Autoradiography. Eds: Phelps ME, Mazziotta JC, Schelbert H 1986

Bergman SR. In: PET of the Heart. Eds: Bergmann SR, Sobel BE. 1992


Rb-82

40-60 mCi

60

55

50

45

40

35

30

25

0

20

15

10

5

N-13 ammonia

20-30 mCi

Work Flow

inject

inject

Pers

scan

CT

scan

min

CT

scan

scan

Pers

inject

inject


60

55

50

45

40

35

30

25

0

20

15

10

5

Rb-82 chloride

inject

inject

Pers

scan

CT

scan

min

scan

scan

Aden

CT

inject

inject


60

55

50

45

40

35

30

25

0

20

15

10

5

Rb-82 chloride

inject

inject

Pers

scan

CT

scan

min

scan

scan

Reg

CT

inject

inject


inject

inject

scan

CT

scan

Pers

min

60

55

50

45

40

35

30

25

0

20

15

10

5

inject

inject

25

0

20

15

10

5

CT

scan

Ex

CT

scan

90

85

80

75

70

65

60

•••

min

N-13 ammonia


= inject

60

55

50

45

40

35

30

25

0

20

15

10

5

Injection times

Cyclotron starts production 23 minutes prior to calibration time

Ex

Reg

Ad

Per

Dob










Abnormal N-13 perfusion study

72 year old man with peripheral vascular disease.

Coronary arteriography:

•LAD: 60% ostial and 80% mid vessel stenoses

•LCX: 90% proximal stenosis and occluded OM

•RCA: 90% ostial stenosis


Summary

• PET myocardial perfusion protocols are simple and easy to incorporate in most practices

• Rb-82 and N-13 ammonia are qualitatively equivalent


Summary

• High throughput, and low cost per patient makes Rb-82 PET practical in a high volume practice

• NH3-ammonia PET is better suited for occasional use in patients with inconclusive SPECT, or as the test of choice in problematic patients


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