Dual-Gated Motion-Frozen Cardiac PET with Flurpiridaz F 18

Abstract

A novel PET radiotracer, Flurpiridaz F 18, has undergone phase II clinical trial evaluation as a high-resolution PET cardiac perfusion imaging agent. In a subgroup of patients imaged with this agent, we assessed the feasibility and benefit of simultaneous correction of respiratory and cardiac motion. Methods: In 16 patients, PET imaging was performed on a 4-ring scanner in dual cardiac and respiratory gating mode. Four sets of data were reconstructed with high-definition reconstruction (HD•PET): ungated and 8-bin electrocardiographygated images using 5-min acquisition, optimal respiratory gating (ORG)-as developed for oncologic imaging-using a narrow range of breathing amplitude around end-expiration level with 35% of the counts in a 7-min acquisition, and 4-bin respiration-gated and 8-bin electrocardiography-gated images (32 bins in total) using the 7-min acquisition (dual-gating, using all data). Motion-frozen (MF) registration algorithms were applied to electrocardiography-gated and dual-gated data, creating cardiac-MF and dual-MF images. We computed wall thickness, wall/cavity contrast, and contrast-to-noise ratio for standard, ORG, cardiac-MF, and dual-MF images to assess image quality. Results: The wall/cavity contrast was similar for ungated (9.3 ± 2.9) and ORG (9.5 ± 3.2) images and improved for cardiac-MF (10.8 ± 3.6) and dual-MF images (14.8 ± 8.0) (P , 0.05). The contrast-to-noise ratio was 22.2 ± 9.1 with ungated, 24.7 ± 12.2 with ORG, 35.5 ± 12.8 with cardiac-MF, and 42.1 ± 13.2 with dual-MF images (all P , 0.05). The wall thickness was significantly decreased (P , 0.05) with dual-MF (11.6 ± 1.9 mm) compared with ungated (13.9 ± 2.8 mm), ORG (13.1 ± 2.9 mm), and cardiac-MF images (12.1 ± 2.7 mm). Conclusion: Dual (respiratory/cardiac)-gated perfusion imaging with Flurpiridaz F 18 is feasible and improves image resolution, contrast, and contrastto-noise ratio when MF registration methods are applied. (2) and better image quality, interpretative certainty, and diagnostic performance than SPECT in a phase 2 clinical trial (3). In particular, imaging with this 18 F-based radiotracer generated higher-resolution cardiac images (4).However, the high image resolution associated with an 18 F-based tracer can be degraded by cardiac and respiratory motion during PET acquisition, leading to image blurring. If such motion is not corrected, the full-potential imaging resolution of Flurpiridaz F 18 may not be realized. We have previously developed a motion-frozen (MF) technique for myocardial perfusion imaging, which recovers resolution lost due to cardiac motion, improving contrast and quantitative diagnostic accuracy (5,6). This technique was also successfully used for automatic coregistration of SPECT with CT angiography (CTA) (7,8) and for contrast improvement in cardiac PET (9).The aim of this study was to investigate the feasibility of myocardial perfusion imaging by Flurpiridaz F 18 PET with correction of both cardiac and respiratory motion. We hypothesized that the myocardial perfusion image quality for F...

Motion Correction of 18F-NaF PET for Imaging Coronary Atherosclerotic Plaques

“…All patients underwent 18 F-NaF PET/CT imaging of the coronary arteries with cardiac gating on a hybrid scanner (64-detector Biograph mCT; Siemens Medical Systems). The subjects were administered a target dose of 125 MBq of 18 F-NaF intravenously and subsequently rested in a quiet environment for 60 min.…”

“…The difference in target-to-background ratio (TBR) between culprit plaques (implicated in acute MI) and nonculprit plaques in 18 F-NaF PET is relatively small (;34%) because of blurring of coronary uptake by cardiac, respiratory, and patient motion. The implication is a greater risk of misclassification when this technique is applied to real-world, unselected populations.…”

“…Among these, microcalcification is a consistent finding, believed to represent the very early stages of the body's attempt to heal inflamed necrotic plaque. A recent series of studies (2)(3)(4) demonstrated that 18 F-sodium fluoride ( 18 F-NaF)-an inexpensive, Food and Drug Administrationapproved, widely available PET tracer-binds preferentially to regions of vascular microcalcification and can be used to identify high-risk plaques and plaque rupture in the coronary arteries. In particular, in a study by Joshi et al increased 18 F-NaF PET activity was found to localize to the exact site of plaque rupture in more than 90% of patients who had recently experienced an acute MI, independent of stenting (2).…”

“…In the present study, we aimed to overcome some of the current limitations of 18 F-NaF PET by developing a motion correction method for coronary 18 F-NaF PET to optimize this promising plaque-imaging technique.…”

Advances in dual respiratory and ECG-gated SPECT imaging

“…At many institutions, myocardial perfusion analysis is assessed by summing all ECG-gated images into a single tomogram without any gating corrections at all, but alternatives exist to freeze-frame LV motion, 17 and an extension of this approach for dual-gating has been reported for PET imaging. 18 Techniques that freeze-frame the heart, mapping counts from all phases into a single breathing phase as well as a single ECG phase, may be preferable to effectively summing position counts for the first half of the respiratory cycle, which is effectively what is done by Kortelainen et al 1 As mentioned above, cardiac motion does not only consist of translation and contraction. There are additional motion components, including torque and hysteresis.…”