Evaluation of MLACF based calculated attenuation brain PET imaging for FDG patient studies

Abstract

Calculating attenuation correction for brain PET imaging rather than using CT presents opportunities for low radiation dose applications such as pediatric imaging and serial scans to monitor disease progression. Our goal is to evaluate the iterative time-of-flight based maximum-likelihood activity and attenuation correction factors estimation (MLACF) method for clinical FDG brain PET imaging. FDG PET/CT brain studies were performed in 57 patients using the Biograph mCT (Siemens) four-ring scanner. The time-of-flight PET sinograms were acquired using the standard clinical protocol consisting of a CT scan followed by 10 min of single-bed PET acquisition. Images were reconstructed using CT-based attenuation correction (CTAC) and used as a gold standard for comparison. Two methods were compared with respect to CTAC: a calculated brain attenuation correction (CBAC) and MLACF based PET reconstruction. Plane-by-plane scaling was performed for MLACF images in order to fix the variable axial scaling observed. The noise structure of the MLACF images was different compared to those obtained using CTAC and the reconstruction required a higher number of iterations to obtain comparable image quality. To analyze the pooled data, each dataset was registered to a standard template and standard regions of interest were extracted. An SUVr analysis of the brain regions of interest showed that CBAC and MLACF were each well correlated with CTAC SUVrs. A plane-by-plane error analysis indicated that there were local differences for both CBAC and MLACF images with respect to CTAC. Mean relative error in the standard regions of interest was less than 5% for both methods and the mean absolute relative errors for both methods were similar (3.4% ± 3.1% for CBAC and 3.5% ± 3.1% for MLACF). However, the MLACF method recovered activity adjoining the frontal sinus regions more accurately than CBAC method. The use of plane-by-plane scaling of MLACF images was found to be a crucial step in order to obtain improved activity estimates. Presence of local errors in both MLACF and CBAC based reconstructions would require the use of a normal database for clinical assessment. However, further work is required in order to assess the clinical advantage of MLACF over CBAC based method.

Application of siemens SMART neuro attenuation correction in brain PET imaging

“…In addition, its correlation with the “criterion standard” was not very good ( R 2 = 0.54). In this study, although the SNAC increased the SUV mean of different brain regions to a various degree, it was significantly correlated with CTAC results ( r = 0.988), consistent with a recent research ( r = 0.98) by Bal et al, [ 25 ] suggesting that the SNAC method is significantly improved compared with the traditional CAC.…”

“…Because of the presence of relatively low-density ventricular system in the brain, and CAC does not consider the attenuation coefficient of the sinus cavity and sinus cavity differences in different patients, which will lead to metabolic differences between the peripheral brain and mesial brain regions. [ 4 , 25 ] Zaidi et al [ 5 ] found that the relative difference of CAC's mean regional cerebral glucose metabolism was <8%. It has been shown that ignoring sinus air-like attenuation coefficient values can result in an overestimation of the tracer uptake by up to 20% in adjacent brain regions.…”

Magnetic Resonance-Based Attenuation Correction and Scatter Correction in Neurological Positron Emission Tomography/Magnetic Resonance Imaging—Current Status With Emerging Applications

“…It can be seen that emission-based attenuation correction is an active field of research, where large clinical validation studies have begun to emerge. A scale-corrected MLACF has recently been shown to provide images that quantitatively and visually correspond to CTAC-reconstructed PET images in 57 patients [131]. Benoit MLAA method was compared with state-of-the-art MRAC and CTAC, producing errors within a few percent [45].…”

Joint Reconstruction of Activity and Attenuation in Time-of-Flight PET: A Quantitative Analysis

“…However, another study (24) found that in a collection of 18 F-FDG brain scans, activity in the reconstructed activity images was more biased with the jointreconstruction method than with an atlas-based correction of attenuation. Finally, there was a study (25) in which the accuracy of another joint-reconstruction method-maximum-likelihood attenuation correction factors-was analyzed on a set of patient brain scans. The authors reported that the joint reconstruction was comparable to the gold standard once a plane-dependent scaling of the activity had been applied.…”