PT  - JOURNAL ARTICLE
AU  - deKemp, Robert
AU  - Hunter, Chad
AU  - Pelletier-Galarneau, Matthieu
AU  - Klein, Michael
AU  - Ironstone, Joel
AU  - Fisher, Joseph
AU  - Ruddy, Terrence
TI  - Respiratory phase-matched attenuation correction improves uniformity of hypercapnea-stress PET myocardial perfusion images
DP  - 2015 May 01
TA  - Journal of Nuclear Medicine
PG  - 483--483
VI  - 56
IP  - supplement 3
4099  - http://jnm.snmjournals.org/content/56/supplement_3/483.short
4100  - http://jnm.snmjournals.org/content/56/supplement_3/483.full
SO  - J Nucl Med2015 May 01; 56
AB  - 483 Objectives The safety profile of adenosine (&analogs) has been questioned recently as a pharmacologic stress agent for myocardial perfusion imaging (MPI). Increased end-tidal partial pressure of CO2 (PetCO2), termed hypercapnea was investigated as an alternative hyperemic stressor.Methods Ten healthy volunteers (9 male) underwent rest + hypercapnea (PETCO2 = 60 mmHg) + adenosine MPI using Rb-82 PET. A low-dose CT scan was acquired at normal end-expiration for attenuation correction of the PET images. ECG- and respiratory-gated images were reconstructed from 1.5 to 8 min after tracer injection. End-expiration gated and ungated (summed) stress images were scored from 0 to 4, using the AHA standard 17-segment model. A sum-stress-score (SSS) ≥ 4 (out of 68 maximum) was considered abnormal. End-expiration gated and ungated CO2 SSS values were compared to ungated adenosine as the clinical standard.Results Ungated perfusion images acquired at peak CO2-stress demonstrated high apparent tracer uptake in the inferior wall, due to over-correction of attenuation effects from PET-CT misalignment due to the increased respiratory tidal volume (12 to 22 L/min; p<0.001). Ungated SSS values were higher using CO2 vs adenosine stress (2.9 vs 1.4; p=0.004) consistent with an apparent increase in heterogeneity of tracer uptake in the myocardium. Respiratory gating allowed reconstruction of end-expiration CO2-stress images with phase-matched attenuation correction. Myocardial uptake uniformity was improved in these end-expiration CO2-stress images; the SSS was not significantly different vs adenosine (1.5 vs 1.4; p=0.4), suggesting that this approach may be used for stress MPI with rubidium PET-CT.Conclusions Controlled CO2 inhalation may be a viable alternative to adenosine for stress MPI, but requires respiratory-gating for accurate end-expiration imaging at peak stress. Post-stress imaging may be more practical for routine clinical application, following the return to normal breathing.Research Support NSERC-ENGAGE grant