06 Jun 19. Featured Paper
Injection-to-scan delay correction improves scan-rescan reproducibility sodium fluoride (18F-NaF) coronary plaque imaging.
Objectives: High test-retest reproducibility is required for the translation of coronary 18F-NaF PET imaging into clinical practice.
In this study we investigate the feasibility of correcting for variations in the injection-to-scan delays and its relative impact on the test-retest reproducibility.
Both imaging sessions included a 30-min PET acquisition following injection of 248±9 MBq 18F-NaF (injection-to-scan delay = 60 min) and a CTA-scan.
All PET datasets were reconstructed in end-diastolic phase (25% of the counts).
Coronary lesions were identified on CTA images in arteries with diameter ≥2mm, with stenosis of >25% in the coronary segment and no prior stents.
Lesion uptake was quantified from spherical Volume of Interests (VOIs) (radius=5 mm), while background activities were obtained in the right atrium using a cylindrical VOI (length=15 mm, radius=10 mm).
Lesions with TBR>1.25 were considered 18F-NaF avid, while lesions with TBR <1.25 were considered 18F-NaF negative.
We corrected injection to imaging intervals for all acquisitions by normalizing the injection-to-scan delays to 60 minutes post injection (equation 1): SUV_(Background Corrected) = SUV_(Background)[asterisk] ((1.5092[asterisk]exp(-0.004[asterisk]60)/(1.5092[asterisk]exp(-0.004[asterisk]t)), based on prior study (1).
The correction was applied to the extracted blood pool activities for all the acquisitions.
We report the injection-to-scan delays and the TBR before and after background blood pool correction (BC).
The test-retest evaluations before and after BC were reported as Bland-Altman analyses and coefficient of reproducibility measures.
Results: A total of 47 unique coronary lesions (15 18F-NaF-avid) were identified on CTA.
Average injection-to-scan delays were found to be (66±9 min, range 59-101 min).
The increased injection-to-scan delays (>60 min) introduced a BC correction factor >1 and, thus, a reduction in the TBR following BC (TBR: Non-corrected=1.18±0.48, BC=1.14±0.46, relative reduction: 2.5±3.8%, range: -0.4% to 17.8%, p=0.98).
Correcting for BC increased test-retest reproducibility for all lesions by 19.7% (Coefficient of reproducibility: Non-corrected = 0.437, BC= 0.365, p<0.001).
Importantly, in a sub-analysis of 18F-NaF-avid lesions only, the test-retest reproducibility was improved by 25.3% (Coefficient of reproducibility: Non-corrected = 0.628, BC=0.501, p<0.001) (Figure 1).
Conclusions: BC technique significantly improves reproducibility of the coronary plaque assessment utilizing only the PET-image data.
(1) Kwiecinski J, Berman DS, Lee S-E, et al. Three-hour delayed imaging improves assessment of coronary 18 F-sodium fluoride PET. J Nucl Med. 2018:jnumed.118.217885.
- Computed tomography angiography (CTA)
- Coronary artery disease
- Coronary Angiography
- Positron emission tomography (PET)