Nuclear Cardiology Cardiac Myocardial Perfusion with 82 Rb. Dominique Delbeke, MD, PhD Vanderbilt University Medical Center Nashville, TN

Transcription

1 Nuclear Cardiology Cardiac Myocardial Perfusion with 82 Rb Dominique Delbeke, MD, PhD Vanderbilt University Medical Center Nashville, TN VUMC PET/CT conference 2009

2 82 Rb Cardiac Perfusion PET 82 Rb is produced in a generator by decay of 82 Sr- 75 second half-life life Kinetics: Potassium analog similar to 201 Thallium High extraction fraction at high flow rates Defects visualized minutes after injection Equal doses at stress and rest due to short T½T Dose available 24 hours per day, 7 days per week Pharmacologic stress studies (no exercise)

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4 A 75 year-old obese male with a Hx of CAD and atypical chest pain underwent dual isotope adenosine stress/rest SPECT

5 A 75 year-old obese male with a Hx of CAD and atypical chest pain underwent dual isotope adenosine stress/rest SPECT Apical ischemia, small Equivocal basal anterolateral ischemia

6 A 75 year-old obese male with a Hx of CAD and atypical chest pain Dipyridamole 82 Rb Rest 82 Rb

7 A 75 year-old obese male with a Hx of CAD and atypical chest pain Dipyridamole 82 Rb Rest 82 Rb 1) Reversible anterolateral wall perfusion defect c/w ischemia 2) Superb homogeneity

8 Stress Rest A 75 year-old obese male with a Hx of CAD and atypical chest pain SSS 9 SRS 1 SDS 8 Angiography: High-grade grade stenosis of the LCX

9 A 75 year-old obese male with a Hx of CAD and atypical chest pain Stress LVEF 41% Rest LVEF 41% Stress Rest In the absence of significant CAD, true stress EF is higher than rest EF

10 Advantages of PET compared to SPECT Higher extraction at high flow rates Better resolution than SPECT (4-6 6 mm versus 10 mm) Accurate attenuation correction methods Evaluation of ventricular function (real stress EF) Dipyridamole stress during acquisition of the images Evaluation of perfusion and metabolism Rapid perfusion imaging protocols (short half-life) life) T1/2 82 Rb: 78 sec High sensitivity instrumentation and potential for absolute quantification Measurement of coronary blood flow reserve

11 Advantage of PET Perfusion: Accurate attenuation correction! SPECT 99m Tc-MIBI stress-rest rest PET 82 Rb stress-rest rest SPECT Diaphragmatic attenuation artifact Courtesy of J. Machac-Mt Mt Sinai, NY PET with attenuation correction Normal

12 Correction for Attenuation Artifacts Attenuation effects: More significant in PET (coincidence imaging) than SPECT because both annihilation photons must pass through the region without interaction. More accurate algorithm to correct with PET than SPECT Methods: Measured attenuation correction using attenuation maps (transmission scan) obtained with various transmission sources: Sources of Ge-68 on older systems X-ray source with PET/CT

13 30 year-old obese woman with LAD dissection during pregnancy, S/P stents presented with recurrent chest pain Exercise 99m Tc- tetrafosmin no AC Rest 99m Tc- tetrafosmin Anteroseptal ischemia? Stress LVEF: 44%

14 30 year-old obese woman with LAD dissection during pregnancy, S/P stents presented with recurrent chest pain Exercise 99m Tc- tetrafosmin with AC Rest 99m Tc- tetrafosmin AC not helpful Anteroseptal ischemia? Stress LVEF: 44%

15 82 Rb PET in obese woman with prior LAD dissection Rx with PCI Equivocal SPECT and recurrent chest pain Dipyridamole 82 Rb Rest 82 Rb 82 Rb Fixed anterior wall and apex: infarct Stress LVEF: 45% Rest LVEF: 43%

16 Gated 82 Rb PET in obese woman with prior LAD dissection Rx with PCI Equivocal SPECT and recurrent chest pain Fixed anterior wall and apex: infarct Stress LVEF: 45% Rest LVEF: 43% Rest 82 Rb Stress 82 Rb

17 Characteristics of an Abnormal 82 Rb PET MPI Study with Near-Balanced Flow Reduction Either no perfusion abnormalities or more frequently a mild decrease in regional tracer uptake at peak stress in at least one coronary distribution LV cavity at peak stress larger than at rest (increased TID ratio) Peak stress LVEF < rest LVEF

18 Near-balanced perfusion 82 Rb PET Stress Rest Stress Rest Stress Rest Stress The TID ratio was In both image sets, there appears to be relatively uniform distribution of tracer On closer inspection, the entire apical segment is relatively underperfused in the peak stress images Rest Courtesy of Mid-America Heart Institute

19 PEAK STRESS LVEF 50% REST LVEF 61% In the absence of ischemia, the stress EF should be higher than the rest EF when utilizing Rb PET Courtesy of Mid-America Heart Institute

20 A 72 year-old obese female (112 kg) with known CAD s/p non Q wave MI and CABG x 4 three years earlier presented with recurrent syncope. Fixed inferolateral defect Questionable ant ischemia vs breast attenuation

21 Stress 82Rb with AC Stress 82Rb with AC

22 Stress 82Rb with AC Stress 82Rb with AC Good quality images Ischemia + infarct inferolateral wall LVEF 37% both during stress and rest Cath: LIMA to LAD: patent SVG to OM1: occluded SVG to OM2: Occluded SVG to RCA: patent

23 Advantage of PET: True stress LVEF 363 patients evaluated with 82 Rb PET Patients without prior CAD and normal perfusion: Rest LVEF: 62% +/-10% Peak stress LVEF: 67% +/- 10% --- LVEF increases at peak vasodilator stress Patients with abnormal perfusion (SSS>2) Rest LVEF: 49% +/- 15% Peak stress LVEF: 52% +/- 15% -- Patients with CAD demonstrate blunting or decrease in LVEF at peak vasodilator stress There is an inverse relationship between delta change in LVEF and magnitude of ischemia during peak vasodilator stress Dorbala S et al. J Nucl Med 2005;46:268P.

24 Advantage of PET: True stress LVEF There is an inverse relationship between delta change in LVEF and magnitude of ischemia during peak vasodilator stress LVEF change of 0 during peak vasodilator stress indicates left main or multivessel CAD Dorbala S et al. J Nucl Med 2007;

25 7% of patients with left main or 3VD (3% of MVD) have homogenous perfusion even with Rb PET Combining perfusion data with LVEF reserve permits 100% detection of balanced ischemia Dorbala S et al. J Nucl Med 2007;

26 Sensitivity/Specificity of PET for CAD Detection Study Gould (86) N 31 PET Sens 95% Spec 100% SPECT Sens - Spec - Tamaki (88) 51 98% Demer (89) % 95% - - Go (90) % 82% 79% 76% Stewart (91) 81 85% 84% 84% 53% Grover-McKay(92) % 73% - - Marwick (92) 74 90% 100% - - Bateman (06) % 93% 82% 73% Sampson (06) % 83% Average >800 90% 89%

27 Rb-82 Myocardial Perfusion Results Diagnostic Certainty: 93% Normal Prob Nl Prob Abnl Abnormal N=142 (39%) N=198 (54%) N=10 (3%) N=14 (4%) N=364 (4%) Courtesy M. Di Carli Courtesy M. Di Carli Brigham and Women s s Hospital

28 Rb-82 Myocardial Perfusion PET/CT Diagnostic Accuracy % 94% /31 16/17 Sensitivity Normalcy Courtesy M. Di Carli Brigham and Women s s Hospital

29 Sensitivity/Specificity of PET for CAD Detection Comparison Tc-MIBI SPECT (n =112)- Cardio-60 (Philips) 82 Rb PET (n = 112)- ECAT Accel (CTI) 99m Tc 82 Image Quality: SPECT: 62% PET: 78% Definitely normal or abnormal: SPECT: 81% PET: 96% PET accuracy higher: In men and women In obese and non obese patients For identification of multivessel disease For detection of stenosis > 50% and >70% Bateman T et al. J Nucl Cardiol 2006;13 (1): 24-33

30 Accuracy of PET and SPECT A. 50% coronary stenosis B. 70% coronary stenosis Bateman T et al. J Nucl Cardiol 2006;13 (1): 24-33

31 Dipyridamole Stress 82 Rb: Risk Stratification Prognostic value of 82 Rb PET MPI as a function of SSS n = ± 0.9 yrs Survival free of HE nl: mild: mod-sev sev: 0.4 % HE 2.3 % HE 7% HE Yoshinaga K et al. J Am Coll Cardiol 2006;48: Survival free of any cardiac event

32 Prognostic value of Rb PET MPI as a function of SSS in patients with equivocal SPECT Survival free of any cardiac event Yoshinaga K et al. J Am Coll Cardiol 2006;48:

33 Prognostic value of Rb PET MPI as a function of SSS in obese patients, BMI > 30 Survival free of any cardiac event Yoshinaga K et al. J Am Coll Cardiol 2006;48:

34 Dipyridamole Stress 82 Rb: Risk Stratification 1,602 patients with median follow-up of 511 days Incremental value of stress perfusion defect over clinical variables in predicting overall survival. 1,274 patients with median follow-up of 511 days Incremental value of LVEF over stress perfusion imaging. Dorbala S et al. J Am Coll cardiol 2007;49:109A

35 Radiation Dose from Cardiovascular Imaging Tc-MIBI (30 mci): ~10 msv (1000 mrem) Tl (3.5 mci): ~20 msv (2,000 mrem) Rb (120 mci) or : 3-15 msv (according to model)# 5 msv (200 mrem)* N-ammonia (40 mci): 2 msv (220 mrem) F-FDG FDG (10 mci): 7 msv (600 mrem) CT Attenuation correction: 0.8 msv ( mrem) CT chest: 4-6 msv ( mrem) CACS (prospective gating): msv ( mrem) CTA (retrospective gating): 8-12 msv ( mrem) With dose reduction: 3-5 msv Catheter angiography 3-12 msv Morin RL, et al. Circulation. 2003;107: Budoff MJ, et al. J Am Coll Cardiol. 2003;42: Thompson RC et al. J Nucl Cardiol 2006;13: #Stabin MG. J Nucl Med 2008;49: * Package insert

36 Why Should We Do 82 Rb Cardiac PET? It is more accurate for detection of CAD It has a higher normalcy rate It has a higher diagnostic certainty It has a high prognostic value It s s safer For the patient For the technologist It is faster

37 82 Rb rest/stress PET/CT Protocol Rb mci Dipy 0.56 mg/kg Rb mci scout CT-trans sec sec gated rest pt out scout sec sec gated stress CT-trans Approx 1 min Approx 7 min Approx 6 min Approx 7 min Approx 1 min Gated rest/stress MP study is completed in approximately 30 mins Courtesy of M. Di Carli, Brigham and Women Hospital

38 CardioGen-82 Generator replaced every 28 days $29,000/month Generator must be utilized with the calibrated CardioGen-82 Infusion System (Start-up cost of $72,000) Infusion System is automated for the infusion and patient dose Permits accurate dosing with minimal operator interface, thus decreasing radiation exposure Contains shielding vault for CardioGen-82 Generator and waste container

39 82 Rb Cardiac PET Acquisition Times Fraction min 80% 95% Fraction of Activity Remaining Fraction of Counts Rec iev ed to Total Pos sible Fraction of counts to be gained by acquiring for 60 Additional Seconds Seconds into Scan Acquisition times need to recognize fast decay of 82 Rb 95% of theoretical max cts will be acquired in first 5 minutes (80% in first 3 minutes) Acquiring an additional 1 min only adds 2.4% more cts

40 In patients with reduced LV function, crucial to wait sufficiently for blood pool to clear to avoid scatter into perfusion defects leading to erroneous diagnosis of ischemia

41 SNM/ASNC : 82 Rb Rest/stress Guidelines Infusion rate 1 ml/s, 30 sec. Max Imaging delay after infusion (LVEF>50%) s Imaging delay after infusion LVEF<50% s. Longer if counts permit. Phased acquisitions (rapid, sequential imaging) can be used to compensate for slow blood pool clear Machac J et al et al. Guidelines J Nucl Cardiol 2006;13 (6):e ),

42 Quality Control for accuracy of co-registration!

43 Middle age female with an equivocal outside stress/rest SPECT Adenosine 13NH3 Rest 13NH 3 Artifactual stress anterolateral defect due to mis-registration

44 Potential Limitations of PET Limited availability of PET Costly initial capital investment Limitation to pharmacological stress Lack of accepted guidelines for indications (PET versus SPECT) Indications accepted now: All pharmacological stress if PET available Obese patients who can not exercise Lack of standardized software for analysis Now: ECTtoolbox: : normal database for 82 Rb and 13 N- ammonia Limited practical capabilities for absolute quantification: Requires dynamic imaging Requires kinetic analysis and compartmental modeling

45 Cardiac PET Conclusions Myocardial PET perfusion High normalcy rate (accurate attenuation correction) High accuracy for detection of CAD Including multi-vessel disease (True LV EF, TID) High diagnostic certainty High prognostic value Indications Same as SPECT Well accepted: Obese ( > 250 lb?) who can not exercise Patients difficult to image by SPECT: Obese, women, children Contradictory or equivocal previous studies Myocardial viability: Perfusion PET/FDG PET

46 Thank you!