Blind Deblurring Reconstruction Technique with Applications in PET Imaging

We developed an empirical PET model taking into account system blurring and a blind iterative reconstruction scheme that estimates both the actual image and the point spread function of the system. Reconstruction images of high quality can be acquired by using the proposed reconstruction technique for both synthetic and experimental data. In the synthetic data study, the algorithm reduces image blurring and preserves the edges without introducing extra artifacts. The localized measurement shows that the performance of the reconstruction image improved by up to 100%. In experimental data studies, the contrast and quality of reconstruction is substantially improved. The proposed method shows promise in tumor localization and quantification

90Y PET/CT quantitative accuracy and image quality

Purpose: To optimize 90Y-PET/CT image reconstruction for quantitative accuracy and optimal image quality.Methods: PET/CT scans of a NEMA IEC phantom (3GBq 90YCl2, sphere uptake ratio of ~7) were acquired on 4 GE (BGO:DSTE, DST & LYSO:DRX, D690) and 1 Siemens (LSO:mCT) scanners in 3D list mode with 30 min/bed; replayed to 20, 15, 10 min/bed. Iterative reconstruction parameters explored were SUB × IT (3 – 80) and post-reconstruction filters: transaxial: 5 – 25 mm cutoff & z-axis (GE only): std vs. heavy. The effects of PSF modeling and TOF correction were evaluated for D690 and mCT. VOIs were drawn inside spheres and in adjacent background regions. The accuracy of sphere activity concentration (AC in kBq/mL) and contrast to noise ratio (CNR) was calculated as function of SUB × IT. Reconstructed PET images were also evaluated qualitatively for sphere detectability and artifacts.Results: AC converged to 70 – 90% accuracy for 37 mm sphere and further degraded for smaller spheres. Spheres at max CNR might not reach AC convergence yet. Smaller spheres have slower convergence but reach CNR max together with other spheres. Scan duration did not strongly affect sphere convergence but shorter scans increased noise and reduced detectability; 13 mm spheres were not visible going from 30 to 15 min/bed. Heavy z-axis (GE) and transaxial filter with 10 – 15 mm cutoff helped suppress noise and increase sphere detectability at the expense of accuracy. Images with PSF+TOF corrections had higher sphere detectability and converged faster. Hot cluster artifacts 5 – 7 times the background were seen in some cases with SUB × IT near convergence and lower filtration.Conclusion: Accurate 90Y AC was not achieved even at convergence and noise is a major concern. 90YPET/CT reconstruction parameters are different than those for 18F and benefit substantially from PSF+TOF corrections. Optimum image quality and accurate AC may not be simultaneously achievable.----------------------------------------Cite this article as: Siman W, Mawlawi O, Kappadath SC. 90Y PET/CT quantitative accuracy and image quality. Int J Cancer Ther Oncol 2014; 2(2):020235. DOI: 10.14319/ijcto.0202.3

Dose volume histogram‐based optimization of image reconstruction parameters for quantitative 90Y‐PET imaging

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147185/1/mp13269.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147185/2/mp13269_am.pd

Performance Characteristics of the 5-Ring GE Discovery Mi PET/CT Scanner Using AAPM Tg-126 Report

AIM: To report on the performance characteristics of the 5-ring GE Discovery MI PET/CT systems using the AAPM TG-126 report and compare these results to NEMA NU 2-2012 where applicable. MATERIALS AND METHODS: TG-126 testing was performed on two GE 5-Rings Discovery MI scanners. Tests performed included spatial resolution, PET/CT image-registration accuracy, sensitivity, count rate performance, accuracy of corrections, image contrast, scatter/attenuation correction, and image uniformity. All acquired data were analyzed using scanner console or free software tools as described by TG-126 and the results were then compared to published NEMA NU 2-2012 values. RESULTS: Both scanners gave similar resolution results for TG-126 and NEMA NU 2-2012 and were within manufacturer specifications. Image-registration accuracy between PET and CT using our clinical protocol showed excellent results with values ≤1 mm. Sensitivity using TG-126 was 19.43 cps/kBq while for NEMA the value was 20.73 cps/kBq. The peak noise-equivalent counting rate was 2174 kcps at 63.1 kBq/mL and is not comparable to NEMA NU 2-2012 due to differences in phantoms and methods used to measure and calculate this parameter. The accuracy of corrections for count losses for TG-126 were expressed in SUV values and found to be within 10% of the expected SUV measurement of 1. Image contrast and scatter/attenuation correction using the TG-126 method gave acceptable results. Image uniformity assessment resulted in values within the recommended ± 5% limits. CONCLUSION: These results show that the 5-ring GE Discovery MI PET/CT scanner testing using TG-126 is reproducible and has similar results to NEMA NU 2-2012 tests where applicable. We hope these results start to form the basis to compare PET/CT systems using TG-126

Sequential Targeting of Retinoblastoma and DNA Synthesis Pathways Is a Therapeutic Strategy for Sarcomas That Can Be Monitored in Real Time

Treatment strategies with a strong scientific rationale based on specific biomarkers are needed to improve outcomes in patients with advanced sarcomas. Suppression of cell-cycle progression through reactivation of the tumor suppressor retinoblastoma (Rb) using CDK4/6 inhibitors is a potential avenue for novel targeted therapies in sarcomas that harbor intact Rb signaling. Here, we evaluated combination treatment strategies (sequential and concomitant) with the CDK4/6 inhibitor abemacicib to identify optimal combination strategies. Expression of Rb was examined in 1,043 sarcoma tumor specimens, and 50% were found to be Rb-positive. Using in vitro and in vivo models, an effective two-step sequential combination strategy was developed. Abemaciclib was used first to prime Rb-positive sarcoma cells to reversibly arrest in G1 phase. Upon drug removal, cells synchronously traversed to S phase, where a second treatment with S-phase targeted agents (gemcitabine or Wee1 kinase inhibitor) mediated a synergistic response by inducing DNA damage. The response to treatment could be noninvasively monitored using real-time positron emission tomography imaging and serum thymidine kinase activity. Collectively, these results show that a novel, sequential treatment strategy with a CDK4/6 inhibitor followed by a DNA-damaging agent was effective, resulting in synergistic tumor cell killing. This approach can be readily translated into a clinical trial with noninvasive functional imaging and serum biomarkers as indicators of response and cell cycling

Toward a standard for the evaluation of PET-Auto-Segmentation methods following the recommendations of AAPM task group No. 211: Requirements and implementation

Purpose: The aim of this paper is to define the requirements and describe the design and implementation of a standard benchmark tool for evaluation and validation of PET-auto-segmentation (PET-AS) algorithms. This work follows the recommendations of Task Group 211 (TG211) appointed by the American Association of Physicists in Medicine (AAPM).Methods: The recommendations published in the AAPM TG211 report were used to derive a set of required features and to guide the design and structure of a benchmarking software tool. These items included the selection of appropriate representative data and reference contours obtained from established approaches and the description of available metrics. The benchmark was designed in a way that it could be extendable by inclusion of bespoke segmentation methods, while maintaining its main purpose of being a standard testing platform for newly developed PET-AS methods. An example of implementation of the proposed framework, named PETASset, was built. In this work, a selection of PET-AS methods representing common approaches to PET image segmentation was evaluated within PETASset for the purpose of testing and demonstrating the capabilities of the software as a benchmark platform.Results: A selection of clinical, physical, and simulated phantom data, including "best estimates" reference contours from macroscopic specimens, simulation template, and CT scans was built into the PETASset application database. Specific metrics such as Dice Similarity Coefficient (DSC), Positive Predictive Value (PPV), and Sensitivity (S), were included to allow the user to compare the results of any given PET-AS algorithm to the reference contours. In addition, a tool to generate structured reports on the evaluation of the performance of PET-AS algorithms against the reference contours was built. The variation of the metric agreement values with the reference contours across the PET-AS methods evaluated for demonstration were between 0.51 and 0.83, 0.44 and 0.86, and 0.61 and 1.00 for DSC, PPV, and the S metric, respectively. Examples of agreement limits were provided to show how the software could be used to evaluate a new algorithm against the existing state-of-the art.Conclusions: PETASset provides a platform that allows standardizing the evaluation and comparison of different PET-AS methods on a wide range of PET datasets. The developed platform will be available to users willing to evaluate their PET-AS methods and contribute with more evaluation datasets. </p

Imaging Long-Term Fate of Intramyocardially Implanted Mesenchymal Stem Cells in a Porcine Myocardial Infarction Model

The long-term fate of stem cells after intramyocardial delivery is unknown. We used noninvasive, repetitive PET/CT imaging with [18F]FEAU to monitor the long-term (up to 5 months) spatial-temporal dynamics of MSCs retrovirally transduced with the sr39HSV1-tk gene (sr39HSV1-tk-MSC) and implanted intramyocardially in pigs with induced acute myocardial infarction. Repetitive [18F]FEAU PET/CT revealed a biphasic pattern of sr39HSV1-tk-MSC dynamics; cell proliferation peaked at 33–35 days after injection, in periinfarct regions and the major cardiac lymphatic vessels and lymph nodes. The sr39HSV1-tk-MSC–associated [18F]FEAU signals gradually decreased thereafter. Cardiac lymphography studies using PG-Gd-NIRF813 contrast for MRI and near-infrared fluorescence imaging showed rapid clearance of the contrast from the site of intramyocardial injection through the subepicardial lymphatic network into the lymphatic vessels and periaortic lymph nodes. Immunohistochemical analysis of cardiac tissue obtained at 35 and 150 days demonstrated several types of sr39HSV1-tk expressing cells, including fibro-myoblasts, lymphovascular cells, and microvascular and arterial endothelium. In summary, this study demonstrated the feasibility and sensitivity of [18F]FEAU PET/CT imaging for long-term, in-vivo monitoring (up to 5 months) of the fate of intramyocardially injected sr39HSV1-tk-MSC cells. Intramyocardially transplanted MSCs appear to integrate into the lymphatic endothelium and may help improve myocardial lymphatic system function after MI

90Y PET/CT quantitative accuracy and image quality

Purpose: To optimize 90Y-PET/CT image reconstruction for quantitative accuracy and optimal image quality.Methods: PET/CT scans of a NEMA IEC phantom (3GBq 90YCl2, sphere uptake ratio of ~7) were acquired on 4 GE (BGO:DSTE, DST &amp; LYSO:DRX, D690) and 1 Siemens (LSO:mCT) scanners in 3D list mode with 30 min/bed; replayed to 20, 15, 10 min/bed. Iterative reconstruction parameters explored were SUB × IT (3 – 80) and post-reconstruction filters: transaxial: 5 – 25 mm cutoff &amp; z-axis (GE only): std vs. heavy. The effects of PSF modeling and TOF correction were evaluated for D690 and mCT. VOIs were drawn inside spheres and in adjacent background regions. The accuracy of sphere activity concentration (AC in kBq/mL) and contrast to noise ratio (CNR) was calculated as function of SUB × IT. Reconstructed PET images were also evaluated qualitatively for sphere detectability and artifacts.Results: AC converged to 70 – 90% accuracy for 37 mm sphere and further degraded for smaller spheres. Spheres at max CNR might not reach AC convergence yet. Smaller spheres have slower convergence but reach CNR max together with other spheres. Scan duration did not strongly affect sphere convergence but shorter scans increased noise and reduced detectability; 13 mm spheres were not visible going from 30 to 15 min/bed. Heavy z-axis (GE) and transaxial filter with 10 – 15 mm cutoff helped suppress noise and increase sphere detectability at the expense of accuracy. Images with PSF+TOF corrections had higher sphere detectability and converged faster. Hot cluster artifacts 5 – 7 times the background were seen in some cases with SUB × IT near convergence and lower filtration.Conclusion: Accurate 90Y AC was not achieved even at convergence and noise is a major concern. 90YPET/CT reconstruction parameters are different than those for 18F and benefit substantially from PSF+TOF corrections. Optimum image quality and accurate AC may not be simultaneously achievable.----------------------------------------Cite this article as: Siman W, Mawlawi O, Kappadath SC. 90Y PET/CT quantitative accuracy and image quality. Int J Cancer Ther Oncol 2014; 2(2):020235. DOI: 10.14319/ijcto.0202.35</p