SPECT images

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of the activity, energy window and collimator effects on SPECT images by using images simulated by SIMIND software

of the activity, energy window and collimator effects on SPECT images by using images simulated by SIMIND software

In LEGP collimator, the holes diameter is relatively larger and the acceptance solid angle is wider. Its spatial resolution is degraded in relative to LEHR but its sensitivity is increased. In fact, this collimator is something between LEHR and LEHS. Image quality plays an important role in nuclear medicine imaging because the goal is to create a reliable image of the irradiated organs to diagnose or treat it correctly. The quality of the SPECT images are limited by several factors such as the attenuation and scatter of gamma ray photons inside the patient body, the detection efficiency of system and the spatial resolution of the collimator-detector system. Amount of the injected activity into the patient body, selection of energy window and intrinsic spatial resolution of collimator are major factors, which affect on the image quality. Because of the quantification of physical parameters are difficult or even impossible to calculate by experimental measurements. Many, papers have been focused on the simulation study based on the Monte carol method. Various simulation programs such as SIMIND, SIMSET, GEANT4 and … has been successfully applied in a variety of nuclear medicine procedure. In 1989, Ljungberg and colleagues at Lund University in Sweden introduced SIMIND as a proprietary code of SPECT. SIMIND software is written in Fortran 90 and includes two main parts: The first section defines the parameter (CHANGE) and the second part (SIMIND) performs the actual simulation (Ljungberg, 2009; Ljungberg, 2012).
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Platelet-based MPLE algorithm for denoising of SPECT images: phantom and patient study

Platelet-based MPLE algorithm for denoising of SPECT images: phantom and patient study

Introduction: In this study the evaluation of a Platelet-based Maximum Penalized Likelihood Estimation (MPLE) for denoising SPECT images was performed and compared with other denoising[r]

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Effects of attenuation map accuracy on attenuation-corrected micro-SPECT images

Effects of attenuation map accuracy on attenuation-corrected micro-SPECT images

To investigate the effect of misregistration, we shifted the original TF maps for phantom studies in either + x (towards the right side of the system) or + y (downwards) direction and the maps for animal studies in + x , + y or + z (towards the back side of the system) direction. The distances of shifting in each direction were set to 1 mm and 3 mm. All original TF maps were also rotated anti- clockwise by 15° to emulate the consequences of animal movement during scans. All these shifted and rotated TF maps were used for attenuation correction of their corresponding SPECT images. Later on, we globally changed the attenuation coefficients in the attenuation maps by ±10% of the original values. This was to emu- late errors introduced by CT itself and/or from convert- ing CT values to attenuation coefficients. TF maps were again calculated with the non-uniform Chang algorithm from these altered attenuation maps and then used for correcting for attenuation in their corresponding SPECT images. As a final test, the TF maps calculated with the +10% attenuation coefficient maps were also rotated anticlockwise by 15° and shifted by 3 mm in the x direc- tion. This way, we introduced a combination of ‘worst- case’ errors. These TF maps were then employed for attenuation correction. All images that were corrected with the abovementioned inaccurate attenuation maps were compared to the reference images.
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Determination of Three-Dimensional Left Ventricle Motion to Analyze Ventricular Dyssyncrony in SPECT Images

Determination of Three-Dimensional Left Ventricle Motion to Analyze Ventricular Dyssyncrony in SPECT Images

A method to compute three-dimension (3D) left ventricle (LV) motion and its color coded visualization scheme for the qualitative analysis in SPECT images is proposed. It is used to investigate some aspects of Cardiac Resynchronization Therapy (CRT). The method was applied to 3D gated-SPECT images sets from normal subjects and patients with severe Idiopathic Heart Failure, before and after CRT. Color coded visualization maps representing the LV regional motion showed significant difference between patients and normal subjects. Moreover, they indicated a difference between the two groups. Numerical results of regional mean values representing the intensity and direction of movement in radial direction are presented. A difference of one order of magnitude in the intensity of the movement on patients in relation to the normal subjects was observed. Quantitative and qualitative parameters gave good indications of potential application of the technique to diagnosis and follow up of patients submitted to CRT.
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Study of the effect of energy window width and peak shift on SPECT images to evaluate false diagnosis

Study of the effect of energy window width and peak shift on SPECT images to evaluate false diagnosis

The peak shift percentage effect on SPECT images using heart phantoms shows four rows of vertical long axis cuts of the heart phantom SPECT study with 4 peak shi[r]

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223Ra-dichloride therapy of bone metastasis: optimization of SPECT images for quantification

223Ra-dichloride therapy of bone metastasis: optimization of SPECT images for quantification

Three energy emission windows (85.0 keV ± 20%, 154.0 keV ± 10%, and 270.0 keV ± 10%) and three scatter windows (47.0 keV to 67.0 keV, 103.0 keV to 123.0 keV, and 210.2 keV to 242.8 keV) are recommended. Al- though Owaki et al. [24] used a single energy window at 84 keV ± 20%, we precise that the gamma camera used in our study is equipped with a 5/8-in. crystal. This crystal gives a better sensitivity than the more common 3/8-in. crystal. This percentage loss of sensi- tivity increases with rising photon energy [29]: the loss in sensitivity can approach 20% at 140 keV and 35% at 190 keV. We found that our crystal allow the use of the sum of the images from three energy windows without loss of spatial resolution. Our study with the NEMA phantom enabled the optimization of the reconstruc- tion parameters (OSEM algorithm with 2 iterations, 10 subsets, and the Butterworth filter) yielding the best compromise between sensitivity and noise.
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Evaluation of attenuation correction process in cardiac SPECT images

Evaluation of attenuation correction process in cardiac SPECT images

Introduction : Attenuation correction is a useful process for improving myocardial perfusion SPECT and is dependent on activity and distribution of attenuation coefficients in the body [r]

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The influence of misregistration between CT and SPECT images on the accuracy of CT-based attenuation correction of cardiac SPECT/CT imaging: Phantom and clinical studies

The influence of misregistration between CT and SPECT images on the accuracy of CT-based attenuation correction of cardiac SPECT/CT imaging: Phantom and clinical studies

effect when respiratory motion correction was applied. All segments in misalignment along Y-axis showed significant effect for uptake value with more impact in lateral wall in[r]

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Evaluation of the role of system matrix in SPECT images reconstructed by OSEM technique

Evaluation of the role of system matrix in SPECT images reconstructed by OSEM technique

Although applying different beam radiation models in system matrix has no significant effect on the image quality, however linear and rectangular detection models at least theoretica[r]

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A new approach to scatter correction in SPECT images
 based on Klein_Nishina equation

A new approach to scatter correction in SPECT images based on Klein_Nishina equation

Corresponding author: Shabnam Oloomi, Medical Physics Department, Mashhad University of Medical Science, Mashhad, Iran.. Such removal of scattered photons leads to incr[r]

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Quantification of Partial Volume Effects in Single Photon Computed Tomography

Quantification of Partial Volume Effects in Single Photon Computed Tomography

Accurate quantification of activity in voxels, tumours as well as in targeted organs is important also for approval of new imaging agents. SPECT images of tumours are required to evaluate the success of therapy and also in cases where monitoring of therapy is essential in order to arrive at a decision on whether to continue or discontinue therapy based on patient benefit. Therapy usually is discontinued in cases where toxicity to patient outweighs benefit. Accurate quantification of SPECT images is however hindered by partial volume effects (PVEs). The latter are attributed to the limited spatial resolution of the imaging system. PVEs may result in either loss or gain in activity counts within a targeted structure leading to failure to obtain accurate quantitative values from nuclear medicine images. Section 1.1 discusses PVEs in detail. Failure to prioritise PVEs when monitoring treatment of smaller tumours may portray them as less aggressive compared to a bigger ones when they are actually more aggressive. 4 Pharmacokinetics studies also rely on quantification of activity for approval of new radiopharmaceutical drugs. 5
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Diagnosis of Acute Myocardial Infarction using Random Forest classifier through SPECT

Diagnosis of Acute Myocardial Infarction using Random Forest classifier through SPECT

between the two are used to update the estimated image. This is repeated till the variation between the calculated and the measured data are smaller than a specific preselected value. Algebraic reconstruction algorithm and maximum like-hood expectation maximization algorithm are part of iterative reconstruction methods. Second reconstruction algorithm called Filtered Back projection algorithm and it is a type of analytical model widely used in SPECT images due to its speed, computational accuracy and simplicity. It is a 2-step process as filtering of images and back projection of filtered image data. Cardiac SPECT images are difficult to interpret due to its high noisy level and poor contrast. Quality of the SPECT images is enhanced using Fourier Filtering the projection image set [3] before image reconstruction. In this method, 2-Dimensional circularly Gaussian model is applied as the spatial frequency filter. This filter is capable to enhance the contrast and reduce noises in the projection image set in a straight forward projection. This technique is used to improve the quality of the images.Patient movement during acquisition of SPECT imaging will be a reason for imaging artifacts during SPECT diagnostic and degrade the image quality and reduce the accuracy of results. This artifact can be reduced by neural network approach [4] using Polaris stereo-Infrared real time monitoring system. Cardiac SPECT images are considered as the key element to find the occurrence of ischemia heart disease [5].Support vector machine can be used for diagnosis of heart disease with 92.3% accuracy, 73.3% specificity, and 98% sensitivity. For Alzheimer’s disease, early diagnosis has great impact and delay the progress of the disease. This can be achieved using novel CAD [6] (Computer-Aided Designing) for Brain SPECT images. As a relevance analysis, Fisher discriminant ratio is used for feature selection and non-negative matrix factorization (NMF) algorithm is used for feature extraction for relevant component of each subset of image in order to minimize the curse of dimensionality. Reduced number of features from NMF is used in SVM algorithm for classification task. The novel approach (NMF+SVM) produced 94% accuracy with 90% sensitivity and specificity.
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Quantitative analysis of phantom studies of 111In and 68Ga imaging of neuroendocrine tumours

Quantitative analysis of phantom studies of 111In and 68Ga imaging of neuroendocrine tumours

than 17 mm were visible in the 111 In-SPECT image, while all spheres were visible in the 68 Ga-PET image. With a further increase of the background activity, SBR of 1.25:1 (Fig. 1d, h), no spheres were clearly seen in the SPECT image whereas spheres with inner diameters equal to and larger than 22 mm were visible in the PET image. To fur- ther compare the image quality of the 111 In-SPECT and 68 Ga-PET images, line profiles were drawn over the 37- and 17-mm spheres, in the SPECT images (Fig. 1a–d) and the PET images (Fig. 1e – h) for the different SBRs. The line profiles support the visual results of the axial slice images of the phantom. For example, for the highest background activity (SBR 1.25:1), the line profile shows no peaks at all related to the spheres in the SPECT images while the 37-mm sphere appears as a peak in the profile in the PET image.
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Evaluation of both perfusion and atrophy in multiple system atrophy of the cerebellar type using brain SPECT alone

Evaluation of both perfusion and atrophy in multiple system atrophy of the cerebellar type using brain SPECT alone

The present study applied tensor-based morphometry (TBM) to SPECT for the assessment of local atrophy according to the procedure shown in Fig. 1. The basic principle of TBM is to analyze the local deformations of an image and to infer local differences in brain structure [3]. First, a linear spatial normalization algorithm in sta- tistical parametric mapping (SPM2) resized all SPECT images of individual subjects to a voxel size of 2.0 mm and adjusted for orientation, and overall width, length and height. This step transformed brains to the anato- mical space of a template brain based on Talairach space. Subsequent non-linear spatial normalization introduced local deformations to each brain to match it to an original template brain for 99m Tc-ECD [4]. This non-linear spatial normalization was done using the high-dimension-warping algorithm [5]. We obtained high-dimensionally warped SPECT images and three- dimensional (3D) deformation fields for every brain using a univariate Jacobian approach. Each of these 3 D deformation fields consists of displacement vectors for every voxel, which describes the 3 D displacement
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Operculum Movement and Microanatomy Skin Structure of Periophthalmodon Schlosseri in Estuary of Barito River

Operculum Movement and Microanatomy Skin Structure of Periophthalmodon Schlosseri in Estuary of Barito River

The non-uniform pixel intensities of the reconstructed SPECT images at end diastole and end systole stages were not significant (p<0.05) when compared. However, the non- uniform pixel intensities were significant (p >0.05) particularly in the anterior and inferior segments) as the positioning moved. The non-uniform pixel intensities in all segments of the reconstructed SPECT slices are at the minimum values when the phantoms were positioned at the center in comparison with off-center. On the other hand, non-uniform pixel intensities at either end diastole or end systole became greater in inferior segments when the positioning of the phantom became eccen- tric until 5 cm off-center, but this non-uniformity changed to be greater in anterior wall when positioning was increased by 10 and 15 cm off-centre. The greatest non-uniformity occurred in the inferior wall due to loss of counts may be caused by artifacts related to poor spatial resolution or non-attenuating gamma rays within the phantom materials. This artifact was observed in clinical studies [19, 20], and in phantom study [21]. Positioning of the phantom may be one of the reasons causing the loss in counts. The effect is clearly seen that the non-uniform pixel intensities changed to be greater in the anterior wall instead of in the inferior wall positioning were increased from 5 cm to 15 cm. The previously elaborated rea- sons which caused artifacts may incur due to the difference in distribution of pixel intensities (density) in the reconstruction of myocardial SPECT image, therefore degradation of SPECT image quality.
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Effective diagnosis of Alzheimer’s disease by means of large margin-based methodology

Effective diagnosis of Alzheimer’s disease by means of large margin-based methodology

different subjects. In this work, the images have been nor- malized using a general affine model, with 12 parameters ([20-22]). After the affine normalization, the resulting image is registered using a more complex non-rigid spa- tial transformation model [21]. The deformations are parameterized by a linear combination of the lowest frequency components of the three-dimensional cosine transform bases [23]. A small-deformation approach is used, and regularization is by the bending energy of the displacement field. Then, we normalize the intensities of the SPECT images with respect to the maximum intensity, which is computed for each image individually by aver- aging over 3% of the highest voxel intensities, similarly as in [24]. After the spatial normalization, one obtains a 95 × 69 × 79 voxel representation of each subject, where each voxel represents a brain volume of 2 × 2 × 2 mm 3 . The database is built up of imaging studies of subjects fol- lowing the protocol of an hospital-based service. First, the neurologist evaluated the cognitive function, and those patients with findings of memory loss or dementia were referred to the nuclear medicine department in the Virgen de las Nieves hospital (Granada, Spain), in order to acquire complementary screening information for diagnosis b . Experienced physicians evaluated the images visually. The images were assessed using 4 different labels: Control (CTRL) for subjects without scintigraphic abnormalities and mild perfusion deficit (AD1), moderate deficit (AD2) and severe deficit (AD3), to distinguish between different levels of presence of hypo-perfusion patterns compatible with AD. In total, the database consists of N =97 subjects: 41 CTRL, 30 AD1, 22 AD2 and 4 AD3 (see Table 1(a) for demographic details). Since the patients are not patholog- ically confirmed, the subject’s labels possess some degree of uncertainty, as the pattern of hypo-perfusion may not reflect the underlying pathology of AD, nor the differ- ent classification of scans necessarily reflect the severity of the patients symptoms. However, when pathological information is available, visual assessments by experts
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Accuracy of coregistration of single photon emission CT with MR via a brain surface matching technique

Accuracy of coregistration of single photon emission CT with MR via a brain surface matching technique

The average error of our coregistrations is higher than that reported in other studies (3, 6, 9). This may be the result of several factors in addition to changes in brain size and shape as discussed above. The markers introduce a de- gree of error relating to the elasticity of the skin and to distortions caused by the head clamps. Also, since rotations around the x-axis cause the greatest error in coregistration of the brain surface (9), the position of our markers on the scalp will produce a greater error measurement than would occur at structures near the center of the brain. Given the above factors, our average error of 4.2 mm is probably an overestimation of the coregistration mismatch. This degree of accuracy is greater than the resolution of our SPECT images, which was approximately 10 mm. The root mean square distance calculated by the mismatch of the binary rendered images is somewhat less than that measured by the markers in each coregistered study. Since this value is determined by calculating the error in the matching of transformed images, it may not reflect the true accuracy of the coregistration. Artifacts in the acquisition or processing of im- age data will artificially increase the root mean square distance, while matching of symmetrical
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Susceptibility weighted MR for evaluation of vasodilatory capacity with acetazolamide challenge

Susceptibility weighted MR for evaluation of vasodilatory capacity with acetazolamide challenge

PURPOSE: To investigate cerebral vasodilatory capacity by acetazolamide challenge in healthy subjects and in patients with chronic occlusive cerebrovascular disease by using susceptibility- weighted gradient-echo MR imaging. METHODS: Eight patients with chronic occlusive cerebro- vascular disease and four healthy volunteers were studied with susceptibility-weighted MR imaging before and after intravenous administration of 1000 mg of acetazolamide. Signal intensities were measured as a function of time in several regions of interest defined on anatomic images. In all patients with chronic occlusive cerebrovascular disease, acetazolamide challenge and resting regional cerebral blood flow were also evaluated with single-photon emission CT (SPECT). RESULTS: In healthy volunteers, signal intensities began to increase at 3 to 4 minutes after acetazolamide administration, with a continuous increase during the subsequent 10 minutes. The effect lasted for approximately 45 minutes after administration. In patients with chronic occlusive cerebrovascular disease, signal changes on susceptibility-weighted MR images of occluded areas with normal vasodilatory capacity on SPECT images did not differ from signal changes of nonoc- clusive areas. In those patients with changes that reflected diminished vasodilatory capacity, the MR images showed a lower percentage of signal changes after acetazolamide administration than those in normally perfused areas. CONCLUSION: Susceptibility-weighted MR imaging offers an alternative method for estimating vasodilatory capacity.
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Search | Preprints

Search | Preprints

Imaging: The myocardium and skeletal muscles were only visible in the initial whole body and SPECT images, but not on the later images in this study (Fig. 3). The early, intermediate and late post-dosing whole-body images were consistent with those reported for rested volunteers [16]. On the earliest images, the organs with the highest radioactivity accumulation were the bladder, liver and the kidneys. The i.v. injection site was also visible on the immediate images of one volunteer, but the percent of radioactive dose in that area, as estimated by image inspection, was negligible and therefore not expected to alter the distribution kinetics of the radiopharmaceutical. There was a striking absence of radioactivity in the brains of all the volunteers in early- and intermediate-time images, indicating effective exclusion of [ 123 I]IAZA by the blood brain barrier. Later images,
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Breath-hold CT attenuation correction for quantitative cardiac SPECT

Breath-hold CT attenuation correction for quantitative cardiac SPECT

The registration of an attenuation map and a pre- reconstructed SPECT image, prior to reconstruction of a quantitative SPECT image corrected for attenuation and scatter, was limited to translations in three spatial direc- tions. If a rigid-body model including rotations or a non-linear registration was employed, an image cor- rected with CT-AC at the EXP phase might provide a consistent result with a TCT-based scan or CT-AC at the other respiratory phases. However, the use of INS or MID attenuation maps has an advantage over the EXP attenuation map in terms of separation between the heart and the liver surfaces, which would contribute to accurate registration of attenuation maps and pre- reconstructed SPECT images. As shown in Table 1, translations toward caudal directions were needed to align CT attenuation maps at any respiration phases to SPECT images. The reason could be different baseline positions of the hearts during breath-hold CT acquisi- tions and SPECT acquisitions with breathing freely, as previously reported by Pan et al. [25]. For TCT attenu- ation map, no alignment between the attenuation map and SPECT image was needed essentially because tem- poral resolutions of TCT and SPECT scans for respira- tory motions were nearly identical. The slight shifts of TCT attenuation maps to SPECT images in cephalad/ caudal directions, 2.4 ± 2.1 mm, might be caused by glo- bal and/or intra-torso motions of subjects.
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