How Do the More Recent Reconstruction Algorithms Affect the Interpretation Criteria of PET/CT Images?

PURPOSE: Recently, a new Bayesian Penalized Likelihood (BPL) Reconstruction Algorithm was introduced by GE Healthcare, Q.Clear; it promises to provide better PET image resolution compared to the widely used Ordered Subset Expectation Maximization (OSEM). The aim of this study is to compare the performance of these two algorithms on several types of findings, in terms of image quality, lesion detectability, sensitivity, and specificity. METHODS: Between September 6th 2017 and July 31st 2018, 663 whole body 18F-FDG PET/CT scans were performed at the Nuclear Medicine Department of S. Martino Hospital (Belluno, Italy). Based on the availability of clinical/radiological follow-up data, 240 scans were retrospectively reviewed. For each scan, a hypermetabolic finding was selected, reporting both for OSEM and Q.Clear: SUVmax and SUVmean values of the finding, the liver and the background close to the finding; size of the finding; percentage variations of SUVmax and SUVmean. Each finding was subsequently correlated with clinical and radiological follow-up, to define its benign/malignant nature. RESULTS: Overall, Q.Clear improved the SUV values in each scan, especially in small findings (< 10 mm), high SUVmax values (≥ 10), and medium/low backgrounds. Furthermore, Q.Clear amplifies the signal of hypermetabolic findings without modifying the background signal, which leads to an increase in signal-to-noise ratio, improving overall image quality. Finally, Q.Clear did not affect PET sensitivity or specificity, in terms of number of reported findings and characterization of their nature. CONCLUSIONS: Q.Clear is an iterative algorithm that improves significantly the quality of PET images compared to OSEM, increasing the SUVmax of findings (in particular for small findings) and the signal-to-noise ratio. However, due to the intrinsic characteristics of this algorithm, it will be necessary to adapt and/or modify the current interpretative criteria based of quantitative evaluation, to avoid an overestimation of the disease burden.

Assessment of dyssynchrony in patients with severe heart failure by nuclear imaging: paradise lost and regained or lost and gone forever?

Cardiac resynchronization therapy, based on biventricular and/or left ventricular preexcitation, is a recently introduced therapeutic option for patients with severe heart failure and intraventricular conduction disturbances. The invasive nature and expense of resynchronization therapy has highlighted the need to prospectively identify optimal candidates, because of the poor correlation of QRS duration with patient response. Scintigraphy and positron emission tomography made it possible the research investigation of the pathophysiological consequences of cardiac conduction disturbances on myocardial contraction, metabolism, and perfusion. Increasing evidence shows that nuclear imaging techniques allow a comprehensive evaluation of the candidates to resynchronization. In fact, phase analysis of equilibrium radionuclide angiography enables a simple, quick and reliable measurement of both of inter- and intraventricular mechanical dyssynchrony, affording an optimal predictive accuracy of the response. In addition, being scintigraphic data highly reproducible, they are suitable for sequential longitudinal follow-up of the ventricular performance and mechanical dyssynchrony in patients implanted with devices.

The beneficial effect of revascularization on jeopardized myocardium: reverse remodeling and improved long-term prognosis.

OBJECTIVES: To evaluate the impact of viability/ischemia before revascularization on improvement in systolic performance, reverse remodeling, symptoms and long-term prognosis post-revascularization. METHODS: Fifty patients underwent thallium-201 imaging before revascularization to assess stress-induced ischemia and viability ('jeopardized myocardium'). Left ventricular (LV) ejection fraction (EF), LV end-systolic volume index (LVESVI) and LV end-diastolic volume index (LVEDVI) were determined before and 3 months post-revascularization. Graft/vessel patency was controlled by repeat angiography. Long-term follow-up data (New York Heart Association (NYHA) class, hard events) were acquired up to 3 years. RESULTS: Patients with > or = 5 jeopardized segments on thallium-201 imaging demonstrated improvement of LVEF at 3 months (from 35+/-6 to 43+/-6%, P<0.001), with reverse remodeling (LVESVI decreased from 68+/-16 to 52+/-14 ml/m(2), P<0.001; LVEDVI decreased from 103+/-21 to 91+/-18 ml/m(2), P<0.001), and improved in NYHA class with excellent long-term prognosis (0% event rate). Conversely, patients with <5 jeopardized segments failed to improve in LVEF (34+/-4 vs. 33+/-7%, NS), and exhibited ongoing remodeling (LVESVI increased from 70+/-14 to 78+/-23 ml/m(2), P<0.001; LVEDVI increased from 106+/-19 to 116+/-25 ml/m(2), P<0.001), without improvement in NYHA class, and worse long-term prognosis (29% event rate). CONCLUSION: Patients with jeopardized myocardium benefit from revascularization with improvement in LVEF, reverse remodeling, improvement in NYHA class and favorable long-term prognosis.