Preliminary study of the detectability of coronary plaque with PET

Abstract

The evaluation of coronary plaque vulnerability could be of great diagnostic value in cardiology. Positron emission tomography (PET) is a good candidate due to its ability to quantify micromolar concentrations of targeted drugs. However, the detectability of sub-voxel targets such as coronary plaque is limited by partial volume effects and by cardiorespiratory motion. The goal of this paper is to investigate the impact of these factors in the detectability of plaque uptake. Radioactive markers were implanted on the epicardium of a pig and in vivo scans were performed. This was complemented with phantom measurements to determine the minimum detectable uptake as a function of background activity. Simulations were used to evaluate the effect of cardiorespiratory motion on the reconstructed lesions. Despite cardiorespiratory motion of up to 7 mm, the markers were detectable in the in vivo scans even after the injection of background. A lower limit of 250 Bq was found for a target to be detectable. Motion reduced the contrast of the reconstructed lesions to 23% of their static counterpart. Respiratory gating improved this to 49% of the static value. The results suggest that coronary plaque evaluation with PET is possible, provided that sufficient plaque-to-myocardium uptake contrast (50 to 100) can be achieved. This requirement increases exponentially for lesions with uptake below 250 Bq. The described experiments provide a means of estimating the minimum uptake and contrast required to ensure the detectability of plaque lesions.

A review of partial volume correction techniques for emission tomography and their applications in neurology, cardiology and oncology

“…It can be argued that PVC should be applied in all emission tomography studies, especially those involving tracer uptake in small structures; indeed PVC is particularly challenging in areas where small structures are the primary focus; an example of this is in imaging plaque in major vessels (e.g. carotid arteries) where the vessel wall is well below the spatial resolution of the instrument (Delso et al 2011, Izquierdo-Garcia et al 2009. The coverage here, however, focuses on the application of PVC in studies of the brain, the heart and cancer.…”

Partial volume effect estimation and correction in the aortic vascular wall in PET imaging

“…Delso et al showed that lesions smaller than the voxel size could be seen when their activity was greater than ≈250 Bq with an activity ratio with respect to background over 50-100 (Bazañez-Borgert et al 2008, Delso et al 2011. The two major factors of signal loss were PVE (≈90% signal loss in phantom acquisitions) and cardio-respiratory motions (≈75-90% signal loss in GATE simulations with the NCAT phantom).…”

Attenuation correction in cardiac PET: To raise awareness for a problem which is as old as PET/CT

“…These acquisition modes might show their potential in the accurate delineation of tracer uptake in the coronaries. 13 However, in such a setting, an image-based registration will most likely be replaced by elastic registration, ideally incorporated in the image reconstruction to make optimal use of all emission events acquired.…”

“…Example of a cardiac 13 NH 3 PET/MRI scan with a misaligned MR-derived lmap and the scan after correcting the lmap for misalignment (6 mm). In this case, a significant lung uptake of 13 NH 3 was present and was projected onto the chest wall-lung interface fully obscuring the reduced perfusion in the lateral wall of this infarct patient. even more complex.…”