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Myocardial Perfusion Imaging
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Elin Trägårdh, David Minarik, Mark Lubberink
Tomographic images must be reconstructed from the acquired projection data. Historically the reconstruction algorithm mostly used was the filtered back projection (FBP) algorithm but has now mostly been replaced with statistical reconstruction methods such as the ordered subset expectation maximization (OSEM) algorithm [9] or variants thereof. The OSEM algorithm and other iterative methods have been adapted for the specific heart cameras and collimators [10, 11]. An algorithm developed for the SMARTZOOM collimator is derived from an objective function based on a modified chi-squared distribution instead of the Poisson distribution, which the OSEM algorithm is derived from, and optimized with a gradient descent algorithm instead of the expectation maximization algorithm [12]. To facilitate an easier review of the images by the physician, the reconstructed transaxial images are then re-orientated with a new z-axis parallel to long axis of the left ventricle yielding images in the short axis (SA) plane of the LV (Figure 15.4). Coronal and sagittal views then represent horizontal and vertical planes with one axis parallel to the long axis of the LV, also called horizontal (HLA) and vertical (VLA) long axis images (Figure 15.5).
Nuclear Medicine Imaging and Therapy
Published in Debbie Peet, Emma Chung, Practical Medical Physics, 2021
David Towey, Lisa Rowley, Debbie Peet
Iterative reconstruction is more computationally intensive than FPB. To address this, a variation on the standard iterative process called Ordered Subsets Expectation Maximisation (OSEM) is often used. In this method, only a subset of projections is used for the first iteration. A second iteration uses a different subset of projections, and so on. In this way, the activity distribution estimate is updated many more times than in standard iterative reconstruction techniques, and the image converges more quickly. Reconstructing with five iterations using ten subsets has been shown to give similar results as 50 iterations and one subset (i.e. standard iterative reconstruction).
Cardiovascular system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
The following parameters are required as an example technical scan set up: 3D OSEM.Time-of-flight is recommended if available.PSF modelling is optional.Matrix and zoom factors to give voxel size of between 2.0 and 3.0 mm.6.5mm Gaussian post-filter (smoothing will suppress noise).Attenuation and scatter correction.8 bins for gating.The static relative perfusion images and gated images are reconstructed with a 120–150 second delay to allow clearance of the blood pool.Dynamic reconstructions can also be performed to determine the absolute myocardial blood flow at stress and rest.
Efficiency of 123I-ioflupane SPECT as the marker of basal ganglia damage in acute methanol poisoning: 6-year prospective study
Published in Clinical Toxicology, 2021
Katerina Kotikova, David Zogala, Vaclav Ptacnik, Jiri Trnka, Karel Kupka, Manuela Vaneckova, Zdenek Seidl, Pavel Diblik, Jarmila Heissigerova, Tomas Navratil, Martin Komarc, Ivan Zak, Kamila Polakova, Hana Brozova, Sergey Zakharov
123I-ioflupane (DATSCANTM, GE Healthcare, B.V Eindhoven, Netherlands) was used for DaT SPECT performed twice (4 and 6 years after discharge) during a 6-year period. Dosage and scanning procedures were in accordance with the manufacturer’s recommendations. Images were acquired using a dual-head SPECT scanner, the GE Infinia HawkEye4 (GE Healthcare, Milwaukee, WI) equipped with a parallel collimator. Imaging was commenced 3 h after an intravenous bolus injection of standard activity (185 MBq) of the radiopharmaceutical. The SPECT projections were acquired for 40 s per projection in a 360° stepwise rotation of detectors, with a rotation radius of 15 cm. Data were collected in 128 × 128 matrices with a zoom factor of 1.33, rendering a pixel size of 3.32 × 3.32 mm. Image reconstruction was done with OSEM (2 iterations, 10 subsets) and post-filtered with a Butterworth filter (critical frequency 0.6 cm−1, order 10). The triple energy window technique was applied for scatter correction. The total scanning time of the protocol was 45 min. A representative example of DaT SPECT image is shown in Figure 1. The review of DaT SPECT images was examiner blinded.
A lack of association between online pornography exposure, sexual functioning, and mental well-being
Published in Sexual and Relationship Therapy, 2020
Ruth Charig, Nima G. Moghaddam, David L. Dawson, Hannah L. Merdian, Roshan das Nair
A key focus of this research was to examine (1) whether perceived realism might account for individual differences in oSEM-outcome relationships and (2) whether familial communication about sex could moderate relationships between oSEM-use, perceived realism, and outcomes of interest. We observed a small, non-significant association between oSEM consumption and perceived realism of oSEM’s portrayals of sexual activity. Specifically, the higher the frequency of oSEM-use, the more realistic the individual perceived oSEM to be. This finding is (somewhat) congruent with previous research which has established a positive association between oSEM-use and perceived realism (Peter & Valkenburg, 2010) – and not inconsistent with the Cultivation Hypothesis (Gerbner & Gross 1976), which postulates a positive relationship between media consumption and the extent to which its content is perceived to reflect real life. However, most of the sample perceived pornography to be more unrealistic than realistic.
99mTc-MIBI SPECT/CT imaging had high sensitivity in accurate localization of parathyroids before parathyroidectomy for patients with secondary hyperparathyroidism
Published in Renal Failure, 2019
Ming Zeng, Wei Liu, Xiaoming Zha, Shaowen Tang, Jin Liu, Guang Yang, Huijuan Mao, Xiangbao Yu, Bin Sun, Bo Zhang, Chun Ouyang, Lina Zhang, Jing Guo, Jing Wang, Yaoyu Huang, Yogendranath Purrunsing, Hanyang Qian, Ningning Wang, Changying Xing
Patients in group B received dual-phase 99mTc-MIBI planar imaging plus early phase SPECT/CT imaging. The SPECT dual detectors (Siemens, Germany, Symbia T6) were placed at the 180° position and rotated 180° around the patients, with the field of view covering the patient’s neck and upper chest. A total of 48 frames (20 s/frame, matrix 128 × 128, zoom 1.0) were acquired. After the completion of SPECT acquisition, the bed was moved forward to the CT scan position, matching the CT scan field of view with the SPECT imaging field of view, and then CT transmission scan was performed (CT acquisition and reconstruction conditions: 120 kV, 80 mA, matrix 512 × 512, layer thickness 3.75 mm, pitch 1). For image reconstruction, Ordered Subsets Expectation Maximization (OSEM) iteration technology was used. Image analysis was focused with high radioactivity distribution on the early or delayed phase planar images or SPECT/CT images, excluding other image interferences was judged as positive. Interpretation of 99mTc-MIBI scintigraphy was performed in consensus by two experienced nuclear medicine physicians. The image findings were scored as positive or negative.