PET MYOCARDIAL PERFUSION AND QUANTIFICATION OF FLOW

Robert Bober, MD, FACC Director of Nuclear Cardiology and John Ochsner and Vascular Institute The Ochsner Clinical School University of Queensland Ochsner Medical Center, New Orleans, LA Disclosures

• Bracco – research support, consultant • Off-label discussions - None Learning Objectives

1. Discuss the basics of positron emission (PET) imaging and how PET differs from standard single-photon emission computed tomography (SPECT) 2. Discuss evaluation of coronary flow reserve, myocardial perfusion, and absolute myocardial flow by PET imaging and their value in the assessment and management of (CAD) 3. Introduce the concept of coronary flow capacity and its potential impact on patient care 4. Use cardiac PET imaging to help identify patients for whom procedures may reduce coronary events Program Agenda

• PET Instrumentation and how it differs from SPECT

• Using PET and Flow to Guide Revascularization

• Measurements of Myocardial Flow Kinetic Models

• Cases

• Self Assessment Module PET Instrumentation Conventional SPECT

• Limited count sensitivity • Limited energy resolution • Limited spatial and contrast resolution • Limited accuracy of measuring uptake without AC

Garcia EV, et al. Cardiol Clin. 2009;27(2):227-236. PET Instrumentation

Line of Response

P N N B+ N P P P P N 0-5 mm Annihilation γ 511 KeV 511 KeV γ B+

Coincidence Event Detected in Ring PET Scanner

Cardiac PET. In: Heller GV, Hendel RC. Handbook of Turkington TG. J Nucl Med Technol. 2001;29(1):4-11. Nuclear Cardiology. 1st ed. London, UK: Springer; 2013. 2D vs 3D Acquisition

2D 3D Multi-ring PET Acquisition Modes Turkington TG. J Nucl Med Technol. 2001;29(1):4-11. Camera Specifications

PET SPECT • 511 KeV photons • Photon energies <140KeV • LIST mode (most) • Binned mode (most) • >3 million counts/sec • 500-3000 counts/sec • ~35 M counts/study • 7-10 M counts/study • Sensitivity (detection of emitted photons) 2%-15% • Sensitivity 2-3x’s less than PETàlonger acquisition • Spatial resolution < 2-3 mm • Spatial resolution 6.0-10.1 mm

• Wackers, JACC. 2010;55(18) • GB Saha, Basics of Pet Imaging • Gould, State of the Art PET 2013, supplement • Salerno, Circ Imaging. 2009;2:412-424 Attenuation Correction

• Photon attenuation results from emitted radiation interacting with tissue.

• For PET, the path length represents the LOR, along which the dually emitted photons travel.

– Therefore, attenuation is independent of the point of origin along the LOR.

• For SPECT, due to its single-photon emission nature, attenuation changes depending on the point of emission.

LOR, line of response.

Courtesy K. Lance Gould, MD. Courtesy K. Lance Gould, MD. How PET Differs From SPECT Higher Accuracy

• Current literature supports a high diagnostic accuracy for cardiac PET perfusion imaging, due to: – Robust attenuation correction – High count densities (improved image quality and interpretation) – Tracers that follow MBF in a more linear fashion than current SPECT tracers

MBF, myocardial blood flow SROC Curves for Diagnostic Accuracy of Rb-82 PET and Tc-99m SPECT With ECG-Gating and Attenuation Correction

Sensivity 85% Sensivity 90% Specificity 85% Specificity 88%

N = 1755 N = 1344 AUC, area under the curve; Q, Cochran Q statistic; SROC, summary receiver-operating characteristic. Mc Ardle BA, et al. J Am Coll Cardiol. 2012;60(18):1828-1837. Summary ROC Curves for SPECT and PET MPI

N = 11,862 patients

MPI, myocardial perfusion imaging; ROC, receiver operating characteristic Parker MW, et al. Circ Cardiovasc Imaging. 2012;5(6):700-707. Overall Diagnostic Accuracy for PET and SPECT: 70% Stenosis Threshold

100 93 87 89 90 82 79 80 73 70 P = 0.02 P = 0.03 60 50 SPECT PET 40 30 20 10 0 Sensivity Specificity Accuracy

Bateman TM, et al. J Nucl Cardiol. 2006;13(1):24-33. Diagnostic Accuracy for Localizing Disease to Individual Coronary Arteries: 70% Threshold

100 P = 0.007 90 P = 0.0001 80 P = 0.003 70 60 50 40 30 20 10 0 Sensivity Specificity Accuracy SPECT PET

Bateman TM, et al. J Nucl Cardiol.2006;13:24-33. Body Habitus and Gender

Results from studies by Bateman and colleagues demonstrate superior accuracy of PET, independent of both body habitus and gender

Bateman TM, et al. J Nucl Cardiol. 2006;13(1):24-33. Diagnostic Accuracy

69% *P=0.05 Men 84% 67% Women 88% *P=0.01

70% *P=0.05 BMI<30 87% 67% *P=0.02 BMI>30 85%

48% *P=0.03 MVD Sensivity 71%

0 25 50 75 100

SPECT PET MVD, multivessel disease. Based on data from Bateman TM, et al. J Nucl Cardiol. 2006;13(1):24-33. Risk Stratification

• SPECT has a wealth of data on risk stratification. • More data are emerging for cardiac PET risk stratification. • For PET, risk stratification is based on: – Size and severity of perfusion abnormalities – Decreased ejection fraction at stress – Overall ventricular function – Coronary flow reserve (CFR) Unadjusted Hazard of Events by % Myocardium Abnormal on Vasodilator Stress Rb-82 PET

All-cause Death Cardiac Death

Dorbala S, et al. J Am Coll Cardiol. 2013;61(2):176-184. Downstream Testing

• Because of improved image quality, reader confidence is increased.

• The downstream effect is referral to catheterization for consideration for potential revascularization, NOT to confirm diagnosis.

• Studies have demonstrated fewer catheterizations following PET compared with SPECT studies. CAD Intervention Utilization Rates vs CAD Management Costs

Utilization Rates of Diagnostic Coronary Arteriography, PTCI, and CABG in Pts Studied with SPECT vs PET MPI CAD Management Costs in Pts Studied with SPECT vs PET MPI

50% ↓ 67% ↓ 50% ↓ CABG, coronary artery bypass graft; CAD, coronary artery disease; PTCI, percutaneous transluminal coronary intervention Merhige ME, et al. J Nucl Med. 2007;48(7):1069-1076. Radiation Exposure

• Radiation exposure reduction has become an import consideration when selecting a test.

• ASNC recommended target dose <9 mSv for a routine study (recommended to be implemented by 2014).

• PET flow tracers have been examined, and it has been demonstrated that patient exposure is below that recommended by ASNC.

ASNC, American Society of Nuclear Cardiology Cerqueira MD, et al. J Nucl Cardiol. 2010; 17(4):709-718. Typical Effective Doses From Procedures

Einstein AJ. J Am Coll Cardiol. 2012;59(6):553-565. Protocol – Patient Convenience

Rest/stress Rb-82 protocols can be accomplished in 30-45 minutes.

Rb-82 Rb-82 20-60 mCi 20-60 mCi Pharmacologic stress*

Gated Gated CT transmission rest stress CT transmission

70-90 sec 70-90 sec

Approx 1 min Approx 7 min Approx 6 min Approx 7 min Approx 1 min

*Dipyridamole, adenosine, or dobutamine USING PET AND FLOW TO GUIDE REVASCULARIZATION

Current Revascularization Practice

• LHC (angiogram) – “gold standard” • “See and fix” approach based on % stenosis • Current guidelines: 50% LM and 70% for revascularization • FFR/stress “intermediate lesions”1 • FFR used in 6% of patients2

LHC, left heart catheterization; LM, left main; FFR, fractional flow reserve

1. Levine GN, et al. J Am Coll Cardiol. 2011;58(24):e44-e122. 2. Dattilo PB, et al. J Am Coll Cardiol. 2012;60(22):2337-2339. Revascularization guided by % stenosis will lead to better outcomes

DATA??? COURAGE and STICH • Revascularization based on % stenosis • Stress testing NOT mandatory • Decisions to guide revascularization based on judgment of angiographer • FFR not utilized

Boden WE, et al. N Engl J Med. 2007;356(15):1503-1516. Velazquez EJ, et al. N Engl J Med. 2011;364(17):1607-1616. COURAGE, Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation; STICH, Surgical Treatment for Ischemic Heart Failure. Rates of SurvivalRates of Survival and and Freedom Freedom from Major From Cardiovascular Events Major Cardiovascular Events

The BARI 2D Study Group. N Engl J Med. 2009;360(24):2503-2515.

The BARI 2D Study Group. N Engl J Med 2009;360:2503-2515 Revascularization Guided by % Stenosis Will Lead to Better Outcomes

DATA

Revascularizaon guided by % stenosis will lead to beer outcomes

“Repeon of Error Does Not Constute Experience” – Edmund Tramont, MD 1999ish FAME I and II

• FFR-guided revascularization • I - FFR vs • II - FFR vs optimal medical therapy

Pijls N, et al. J Am Coll Cardiol. 2010;56(3):177-184. De Bruyne B, et al. N Engl J Med. 2012;367(11):991-1001.

FAME, Fractional Flow Reserve versus Angiography for Multivessel Evaluation; MACE, major adverse cardiac events; PCI, percutaneous coronary intervention Herzog BA, et al. J Am Coll Cardiol. 2009;54(2):150-156.

Ziadi MC, et al. J Am Coll Cardiol. 2011;58(7):740-748.

MFR, myocardial flow reserve; SSS, Murthy VL, et al. Circulation. 2011;124(20):2215-2224. summed stress score. Introduction to Coronary Blood Flow

• Ischemia – myocardial O2 supply vs demand • Adequate supply is maintained with ability to increase CBF • 2 major resistances to flow – Epicardial arteries (>350 µm) – Arterioles and capillaries (microvasculature)

§ Resting microvascular (R2) >>> epicardial (R1) § Normally regulation occurs at level of microvasculature

• CBF increases automatically to increase O2 demands – Exercise – Pharmacologic stress – Neurohormonal

CBF, coronary blood flow Epicardial Vessels and the Microvasculature Pathologic Conditions

• R1 > R2 – Coronary stenosis and diffuse disease à Flow impaired at level of epicardial artery

• R2 > R1

– Autoregulation impaired à Flow impaired within microvasculature Coronary Flow Reserve

3.2 = 2.9 1.1

• Baseline flow remains stable up to ~83% stenosis. • Hyperemic flow starts diminishing ~40% stenosis.

Gould KL, et al. Am J Cardiol. 1974;33(1):87-94. A Brief Word on FFR

• FFR = fractional flow reserve • Pressure-derived flow surrogate • “Stress test” of an artery in the

Distal coronary pressure FFR = ------Proximal coronary pressure

During Maximal Hyperemia Relationships of CFR, FFR, and Absolute Flow

Danad I, et al. J Am Coll Cardiol. Johnson NP, et al. JACC Cardiovasc 2014;64(14):1464-1475. Imaging. 2012;5(2):193-202. Relationships of CFR, FFR, and Absolute Flow

Johnson NP, et al. JACC Cardiovasc Imaging. 2012;5(2):193-202. Invasive CFR vs % Stenosis

CFR, coronary flow reserve; LAD, left anterior descending artery White CW, et al. N Engl J Med. 1984;310(13):819-824. % Stenosis vs FFR

Tonino PA, et al. J Am Coll Cardiol. 2010;55(25):2816-2821. Why is there a huge disparity between flow and anatomy?

Flow Dynamics

• Dependent on lesion length • Dependent on lesion diameter to the 4th power • A small decrease in diameter or increase in length has a profound effect on flow

Gould KL. Circ Res. 1985;57(3):341-353. Limitations of Anatomic Measures of Stenosis Severity by Angiogram or IVUS

Blood Flow No stenosis CFR = 4.0

87% stenosis CFR = 1.0

63% stenosis CFR = 3.4

Diffuse no stenosis IVUS 38% CFR = 1.4

Diffuse + 60% Artgm IVUS 75% CFR = 1.0

Diffuse + 62% Artgm IVUS 75% & adaptive remodeling CFR = 3.5

IVUS, ; Artgm, arteriogram Gould KL. JACC Cardiovasc Imaging. 2009;2(8):1009-1023. Flow vs Stenosis Paradox

• Flow is determined by a combination of • Stenosis • Diffuse disease • Arterial remodeling • Microvascular function • Impossible to visually determine the physiologic impact of aggregate disease Measurements of Myocardial Flow Kinetic Models Analogy of Kinetic Modeling

• Problem: measure height of a tree • Solutions – Chop it down – Sun + shadow + trigonometry – Photograph tree and yard stick; scaling • All methods are valid and should yield similar results How Is Flow Calculated?

• Kinetic modeling (various models) • Basic principles Flow = (myocardial activity) ÷ (time activity of arterial blood pool) (extraction coefficient) • PET is capable of measuring myocardial activity (M) and activity blood pool (A). • Extraction coefficient of Rb-82 and N-13 calculated experimentally. • F = M/(1 – e-(0.45 + 0.16F/F))(A) for Rb-82. • Different kinetic models have different assumptions for extraction coefficient and measurements of A. Yoshida K, et al. J Nucl Med. 1996;37(10):1701-1712. Relative Imaging Activity

Myocardial Activity

0 120 240 360 480 600 720 Time (s) Time-Activity Curves, Rb-82

Blood Pool Activity Activity

Myocardial Activity

0 120 240 360 480 600 720 Time (s) For Each Site Percent with Optimal Arterial Input (highest arterial input without spillover)

Vasquez AF, et al. JACC Cardiovasc Imaging. 2013;6(5):559-568. Arterial Input Function (Ao)

• Most SP automated – selection typically at basal plane of LV and LA • Some SP allows manual choice • Best Ao could differ between stress and rest

LA, left ; LV, left ; SP, software package 2D vs 3D

• 3D >10Mcps (~30 mCi, 1100 MBq), decline in accuracy and increased image noise from high randoms and dead-time factors • At higher activities, the random rate becomes prohibitive in 3D • Reduced dose of isotope required to obtain accurate input function • Reduced dose reduces myocardial count density Technical Requirements of Flow?

• Register attenuation/emission images • 2D - Linear count recovery up to 3M cps • 3D - Linear count recovery up to 12M cps and avoid scanner saturation from 1st pass bolus (need for internal QC on all images) • Selection and QC of input function – Confirm not in or on LV

LV, left ventricle; QC, quality control

Gould KL, et al. J Am Coll Cardiol. 2013;62(18):1639-1653. CFR in 1674 Rest Dipyridamole Quantitative PET Perfusion Images

Based on data from Sdringola S, et al. JACC Cardiovasc Imaging. 2011;4(4):402-412. Courtesy of K. Lance Gould, MD. Is My Software Correct? (assuming technical requirements are met)

• Sample 20 NORMAL patients. • Young, no risk factors, no tobacco, screen for caffeine • Resting flows should all be <1 cc/min/gm AND • Stress flows should all be ~3.5 cc/min/gm ∴ CFR ~>4.3

Something is wrong if you do not get these values! Is My Software Correct? (assuming technical requirements are met)

• Sample 20 ABNORMAL patients with definite ischemia (classic angina, perfusion abnormality, and cath-correlated disease) – Low stress in ischemic zone should be <0.9 cc/min/gm with low CFR <1.74 – Occluded vessels CFR <1.0

Something is wrong if you do not get these values! • 25 patients with “low-to-intermediate probability of CAD” • 26 patients with “known CAD” • 3 different software applications • GE Discovery VCT PET/CT (2D mode, FBP)

Tahari AK, et al. Eur J Nucl Med Mol Imaging. 2014;(1):126-135. Tahari AK, et al. Eur J Nucl Med Mol Imaging. 2014;(1):126-135. Tahari AK, et al. Eur J Nucl Med Mol Imaging. 2014;(1):126-135. Measurement of Absolute Flow

• Requires blood pool and myocardial activity

• Extraction coefficient and kinetic modeling software

• Results typically in cc/min/g of myocardium

• Absolute flow measured at rest and stress (rMBF and sMBF) We Can Measure Flow … Now What?

• What is “normal”? • Is there a point where flow drops below metabolic demand? • Is there a flow “threshold” that is associated with angina or ST depression? • Is CFR or stress flow more important?

CFR, coronary flow reserve Conceptual Thresholds of Flow Causing Ischemia

Flow Value(s) ?? Percent or Number of Cases

FLOW

Stents/CABG Medical Therapy

Courtesy of K. Lance Gould, MD. Ischemic Thresholds for Flow

CFR <2.03 +

CFR <1.74 +

CFR, coronary flow reserve

Johnson NP, et al. JACC Cardiovasc Imaging. 2011;4(9):990-998. Conceptual Thresholds of Flow Causing Ischemia

Stress flow 0.9 cc/min/g and CFR of 1.7 PercentCasesNumber or of

FLOW

Stents/CABG Medical Therapy

Courtesy of K. Lance Gould, MD. Coronary Flow Capacity

Johnson NP, et al. JACC Cardiovasc Imaging. 2012;5(4):430-440. Invasive Coronary Flow Capacity Map

van de Hoef TP, et al. JACC Cardiovasc Interv. 2015;8(13):1670-1680. Scatter Plot of Invasive Flow Data Across the Coronary Flow Capacity Concept

van de Hoef TP, et al. JACC Cardiovasc Interv. 2015;8(13):1670-1680. Scatter Plots of Fractional Flow Reserve Across Map of Coronary Flow Capacity

van de Hoef TP, et al. JACC Cardiovasc Interv. 2015;8(13):1670-1680. Risk of Major Adverse Cardiac Events According to Coronary Flow Capacity Strata

van de Hoef TP, et al. JACC Cardiovasc Interv. 2015;8(13):1670-1680. Left Ventricular Quadrants in Cardiac PET

Johnson NP, et al. JACC Cardiovasc Imaging. 2011;5(4):430-440. Case 1

• 49-year-old female admitted for chest pain • mellitus, , and tobacco use • BP 173/109 mm Hg • Troponin negative • ECG sinus rhythm, no acute ST changes Case 1

AV, atrioventricular; D1, first diagonal branch; D2, second diagonal branch; LAD, left anterior descending artery; LCx, left circumflex artery; LV, left ventricular; OM1, first obtuse marginal branch; OM2, second obtuse marginal branch; PDA, posterior descending artery; RI, ramus intermedius Case 1 CASE #1 Case 1 CASE #1 Case 5

• 65-year-old woman with chest pain in ED • BP 170/110 mm Hg • Tobacco use, hypertension, unknown lipids, denies diabetes mellitus • ECG – left ventricular hypertrophy with strain • Troponin borderline

ED, emergency department. Case 5 Case 5 Case 5 Case 6

• 44-year-old woman transferred for TMR for lifestyle-limiting angina • h/o: >5 PCIs, 5-vessel CABG, 4/5 grafts occluded • Known RCA and LCX occlusion • Patent SVG jump to OM1-OM2 • Patient arrived and PCI of LAD was performed • Angina walking to bathroom later that PM

CABG, coronary artery bypass graft; TMR, transmyocardial revascularization; LAD, left anterior descending artery; SVG, saphenous vein graft. Case 6 Case 6 Case 6 Case 7

• 87-year-old man with chest pain and SOB • Found to be in atrial fibrillation with RVR • Hypertension, hyperlipidemia, diabetes mellitus • Troponin 3.5 • Beta-blockers à converted to sinus • LHC occluded RCA and “3VD” referred for CABG • PET requested for 2nd opinion by patient

RVR, rapid ventricular response; 3VD, three-vessel disease. Case 7 Case 7 Case 7 Defect, No Defect, No Defect, Intervenon Intervenon No Intervenon

Increased 0.6±0.7 cc/min/g sMBF no change sMBF no change (2.0±0.6 vs 1.9±0.7 (1.2±0.4 vs 1.7±0.8, p<0.001). (1.7±0.3 vs 1.5±0.4 cc/min/g, p=0.7). cc/min/g, p=0.16)

Bober, R, The Effect of Coronary Revascularization on Regional Myocardial Blood Flow. J Nucl Cardiol. 2016 Cardiac PET With Flow Reserve Measuring the Effects of Revascularization

• 65-year-old man • History of HTN, DM, CAD s/p CABG • LIMA to LAD, SVG to PLB, and SVG to OM2 • PET to assess symptoms of exertional dyspnea • Angiogram with 2-vessel PCI performed • No change in symptoms • Repeat PET

PET, positron emission tomography; HTN, hypertension; DM, diabetes mellitus; CAD, coronary artery disease; s/p, status post; CABG, coronary artery bypass graft; LIMA, left internal mammary artery; LAD, left anterior descending artery; SVG, saphenous vein graft; PLB, posterolateral branch; OM2, second obtuse marginal branch; PCI, percutaneous coronary intervention. PET Prior to PCI PET 4 weeks after PCI

SUCCESS??

Bober R, et al. Progress in Cardiovascular Diseases, 2015;57(6): 537-554 PET Prior to PCI PET 4 weeks after PCI

NO BENEFIT (at best) Case #

• 65 y/o female presented with NSTEMI • Occluded high OM (culprit) – PCI, high grade disease in PDA and proximal LAD medically managed • CP recurred in ~ 1 week • Returned and underwent LHC • Prox LAD FFR = .82 • Therefore PCI of PDA • Continued with angina Case # Case

1.27 1.04/1.27=.82

.89/1.27=.70 1.04

.73/1.27=.57 .89 .73 .82

.70

.57 LE

• 67-70 y/o man with HTN, HPL, DM, tobacco use, Hep C, CKD • Initial SPECT 5-12 for DOE and CP • fixed defect base to mid inferior wall • Normal wall motion on gated SPECT and ECHO • Interpreted as likely diaphragm attenuation • Medically managed • Second SPECT 8-14 for DOE and fatigue • Fixed defect base to distal inferior wall • Abnormal inferior wall motion (low normal LVEF) • Interpreted as infarct with peri-infarct ischemia • Medically optimized. No LHC as patients sxs improved and no angina LE SPECT 5-2012 LE SPECT 8-2014 LE 7-2015

• Was CP free for ~ 3 years however started to develop exertional CP and worsening DOE • Opted for repeat stress for risk stratification over LHC. • SPECT interpreted as no change since 2014 however, – “…in this patient with angina and a known fixed perfusion abnormality, SPECT scanning with Tc-99 based isotopes can misclassify ischemic tissue as infarction (based on the flow properties of Tc-99 and tissue attenuation) Consider PET stress testing with absolute flow.” • PET stress flow obtained LE SPECT 7-2015 LE Review of 2014 and 2015 SPECTS

2014 2015 Preview of 2014 and 2015 SPECTS

2014 2015 LE PET LE PET LE PET Flows LE PET Flow Capacity LE Summary • SPECTS 2012-2015 • All with FIXED (rest and stress) inferior wall defects • 2012 thought to be attenuation • 2014-2015 thought to be secondary to CAD (infarct) • PET – No resting defect à no infarction – Ischemic flows in RCA and LCX territory – LAD flows – not normal however, not “ischemic” • Presence of disease expected • Not flow limiting • LHC- – High grade disease in OM1 and RCA – Mild/moderate distal LAD disease Polling Question

When comparing the difference between photons of SPECT and PET tracers, the true statement regarding SPECT photons: a) Are emitted at ~ 511KeV b) Are emitted as single photons c) Attenuation is independent of the point of origin along the Line of Response d) Are higher energy than PET photons

• GB Saha, Basics of Pet Imaging Polling Question

Coronary Flow Reserve (CFR) is: a) Absolute hyperemic flow minus absolute resting flow b) Absolute resting flow minus absolute hyperemic flow c) The ratio of absolute hyperemic flow to absolute resting flow d) The ratio of absolute resting flow to hyperemic flow

Gould KL, et al. Am J Cardiol. 1974;33(1):87-94. Polling Question

The estimated effective dose of radiation for cardiac PET rest/stress study with Rb-82 is: a) 10 mSv b) <5 mSv c) 11-15 mSv d) 6-9 mSV

Einstein AJ. J Am Coll Cardiol. 2012;59(6):553-565. Polling Question

Under normal conditions, what is the major resistance to coronary flow? a) Myocardial microvasculature b) Sympathetic nervous system c) Epicardial vessel d) Diastolic filling time

Gould KL. Circ Res. 1985;57(3):341-353. Polling Question

Identify the true statement regarding Coronary Flow Capacity a) Is the integration of both CFR and absolute myocardial stress flow due to a combination of discrete, diffuse and microvascular disease. b) Is the ratio of stress to resting myocardial blood flow. c) Is dependent on patient BMI (body mass index). d) Doesn’t not fluctuate within an individual.

Johnson NP, et al. JACC Cardiovasc Imaging. 2012;5(4):430-440.

PET Myocardial Perfusion and Quantification of Flow, Robert Bober, MD

1. When comparing the difference between photons of SPECT and PET tracers, the true statement regarding SPECT photons: A. Are emitted at ~ 511KeV B. Are emitted as single photons (KEY) C. Attenuation is independent of the point of origin along the Line of Response D. Are higher energy than PET photons

B is correct GB Saha, Basics of PET Imaging

2. Coronary Flow Reserve (CFR) is: A. Absolute hyperemic flow minus absolute resting flow B. Absolute resting flow minus absolute hyperemic flow C. The ratio of absolute hyperemic flow to absolute resting flow (KEY) D. The ratio of absolute resting flow to hyperemic flow

C is correct Gould KL, et al. Am J Cardiol. 1974;33(1):87-94.

3. The estimated effective dose of radiation for cardiac PET rest/stress study with Rb-82 is: A. 10 mSv B. <5 mSv (KEY) C. 11-15 mSv D. 6-9 mSV

B is correct Einstein AJ. J Am Coll Cardiol. 2012;59(6):553-565.

4. Under normal conditions, what is the major resistance to coronary flow? A. Myocardial microvasculature (KEY) B. Sympathetic nervous system C. Epicardial vessel D. Diastolic filling time

A is correct Gould KL. Circ Res. 1985;57(3):341-353.

5. Identify the true statement regarding Coronary Flow Capacity A. Is the integration of both CFR and absolute myocardial stress flow due to a combination of discrete, diffuse and microvascular disease. (KEY) B. Is the ratio of stress to resting myocardial blood flow. C. Is dependent on patient BMI (body mass index). D. Doesn’t not fluctuate within an individual.

A is correct Johnson NP, et al. JACC Cardiovasc Imaging. 2012;5(4):430-440.