Edinburgh Imaging


06 Jun 19. Featured Paper

Injection-to-scan delay correction improves scan-rescan reproducibility sodium fluoride (18F-NaF) coronary plaque imaging.

Link to paper on The Journal of Nuclear Medicine.



Martin Lyngby Lassen, Jacek Kwiecinski, Damini Dey,  Sebastien Cadet, Guido Germano, Daniel Berman, Philip Adamson, Alastair Moss, Marc Dweck, David Newby and Piotr Slomka



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.


Methods: Twenty patients with coronary artery disease who underwent repeated hybrid PET/CT angiography (CTA) imaging within 3 weeks were recruited.

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.