Effect of Reconstruction Algorithms on Myocardial Blood Flow Measurement with 13N-Ammonia PET

Abstract

Filtered backprojection (FBP) is the traditional method for 13 N-NH 3 PET studies. Ordered-subsets expectation maximization (OSEM) is popular for PET studies because of better noise properties. Scant data exist on the effect of reconstruction algorithms on quantitative myocardial blood flow (MBF) estimation. Methods: Twenty patients underwent dynamic acquisition rest/stress 13 N-NH 3 studies. In Part 1, 19 rest/stress image pairs were reconstructed by FBP (10-mm Hanning filter) and by OSEM with 28 subsets and 2 (OSEM2), 6 (OSEM6), or 8 iterations (OSEM8), and a 10-mm postreconstruction smoothing gaussian filter. In Part 2, 9 image pairs were reconstructed by FBP (10-mm Hanning filter) and by OSEM with 28 subsets, 8 iterations, and a gaussian 5-, 10-, or 15-mm postreconstruction smoothing filter. Average MBF (mL/min/mL of myocardium) was calculated using a 3-compartment model. Results: Part 1: For rest MBF, the correlations between FBP and each of the OSEM algorithms were r 2 5 0.71, 0.73, and 0.77, respectively. MBF by OSEM6 (0.98 6 0.48 [mean 6 SD]) and OSEM8 (0.96 6 0.46) was not significantly different from FBP (1.02 6 0.39), but OSEM2 (0.80 6 0.37) was significantly lower (P , 0.0003). With stress, the correlations were high between FBP and OSEM6 and OSEM8 (r 2 5 0.85 and 0.90), and MBF by OSEM6 and OSEM8 was not significantly different from FBP. Part 2: Resting MBF correlated well between FBP and all OSEM smoothing filters (r 2 5 0.82, 0.85, and 0.88). Rest MBF using postsmoothing 5-or 10-mm filters was not different from FBP but was significantly lower with the 15-mm filter (P , 0.05). With stress, the correlations were good between FBP and OSEM regardless of smoothing (r 2 5 0.76, 0.77, and 0.79). However, MBF with postsmoothing 10-and 15-mm filters was significantly lower than by FBP (P , 0.05). Conclusion: Reconstruction algorithms significantly affect the estimation of quantitative blood flow data and should not be assumed to be interchangeable. Although aggressive smoothing may produce visually appealing images with reduced noise levels, it may cause an underestimation of absolute quantitative MBF. In selecting a reconstruction algorithm, an optimal balance between noise properties and diagnostic accuracy must be emphasized.

Image‐derived and arterial blood sampled input functions for quantitative PET imaging of the angiotensin II subtype 1 receptor in the kidney

“…The partial volume effect (PVE) has been widely recognized as a factor affecting the accuracy of the ID-IF. 11 It has been shown that filtered back projection (FBP) and ordered subset expectation maximization (OS-EM) reconstruction techniques can also result in quantitative differences 12 but their effect is often neglected. In the present work, we investigated the effect of PVE correction methods and also the effect of image reconstruction algorithms.…”

How to reconstruct dynamic cardiac PET data?

“…A decade ago, when first-generation iterative techniques were introduced to clinical practice, some investigators found that the results were not interchangeable when compared to FBP. 8 It has been demonstrated that iterative technique such as OSEM do not provide accurate image-derived input functions for cardiac PET studies because of bias in count estimation, 9 although this bias can be potentially compensated by smoothing.…”

“…On the other hand, new reconstruction methods offer great potential for improved noise statistics 8 and improved image fidelity. 10 It has been demonstrated for cardiac dynamic applications that iterative techniques also yield improved image accuracy and less noise compared with FBP.…”

Advances in rubidium PET and integrated imaging with CT angiography

“…A recent analysis for N-13 ammonia flow studies found that image reconstruction type (ie, filtered backprojection or iterative) can significantly affect blood flow estimates, and smoothing filters after image reconstruction cause underestimation of absolute blood flow [31]. It is reasonable to assume that Rb-82 flow estimates will be influenced similarly by image reconstruction type and smoothing filter; however, this has not yet been studied.…”