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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Evaluation of attenuation and scatter correction requirements in small animal PET and SPECT imaging

Konik, Arda Bekir 01 July 2010 (has links)
Positron emission tomography (PET) and single photon emission tomography (SPECT) are two nuclear emission-imaging modalities that rely on the detection of high-energy photons emitted from radiotracers administered to the subject. The majority of these photons are attenuated (absorbed or scattered) in the body, resulting in count losses or deviations from true detection, which in turn degrades the accuracy of images. In clinical emission tomography, sophisticated correction methods are often required employing additional x-ray CT or radionuclide transmission scans. Having proven their potential in both clinical and research areas, both PET and SPECT are being adapted for small animal imaging. However, despite the growing interest in small animal emission tomography, little scientific information exists about the accuracy of these correction methods on smaller size objects, and what level of correction is required. The purpose of this work is to determine the role of attenuation and scatter corrections as a function of object size through simulations. The simulations were performed using Interactive Data Language (IDL) and a Monte Carlo based package, Geant4 application for emission tomography (GATE). In IDL simulations, PET and SPECT data acquisition were modeled in the presence of attenuation. A mathematical emission and attenuation phantom approximating a thorax slice and slices from real PET/CT data were scaled to 5 different sizes (i.e., human, dog, rabbit, rat and mouse). The simulated emission data collected from these objects were reconstructed. The reconstructed images, with and without attenuation correction, were compared to the ideal (i.e., non-attenuated) reconstruction. Next, using GATE, scatter fraction values (the ratio of the scatter counts to the total counts) of PET and SPECT scanners were measured for various sizes of NEMA (cylindrical phantoms representing small animals and human), MOBY (realistic mouse/rat model) and XCAT (realistic human model) digital phantoms. In addition, PET projection files for different sizes of MOBY phantoms were reconstructed in 6 different conditions including attenuation and scatter corrections. Selected regions were analyzed for these different reconstruction conditions and object sizes. Finally, real mouse data from the real version of the same small animal PET scanner we modeled in our simulations were analyzed for similar reconstruction conditions. Both our IDL and GATE simulations showed that, for small animal PET and SPECT, even the smallest size objects (~2 cm diameter) showed ~15% error when both attenuation and scatter were not corrected. However, a simple attenuation correction using a uniform attenuation map and object boundary obtained from emission data significantly reduces this error (~1% for smallest size and ~6% for largest size, in non-lung regions). In addition, we did not observe any significant improvement between the uses of uniform or actual attenuation map (e.g., only ~0.5% for largest size in PET studies). The scatter correction was not significant for smaller size objects, but became increasingly important for larger sizes objects. These results suggest that for all mouse sizes and most rat sizes, uniform attenuation correction can be performed using emission data only. For smaller sizes up to ~ 4 cm, scatter correction is not required even in lung regions. For larger sizes if accurate quantization needed, additional transmission scan may be required to estimate an accurate attenuation map for both attenuation and scatter corrections.
12

A Novel Methodology for Iterative Image Reconstruction in SPECT Using Deterministic Particle Transport

Royston, Katherine 30 April 2015 (has links)
Single photon emission computed tomography (SPECT) is used in a variety of medical procedures, including myocardial perfusion, bone metabolism, and thyroid function studies. In SPECT, the emissions of a radionuclide within a patient are counted at a gamma camera to form a 2-dimensional projection of the 3-dimensional radionuclide distribution within the patient. This unknown 3-dimensional source distribution can be reconstructed from many 2-dimensional projections obtained at different angles around the patient. This reconstruction can be improved by properly modeling the physics in the patient, i.e., particle absorption and scattering. Currently, such modeling is done using statistical Monte Carlo methods, but deterministic codes have the potential to offer fast computation speeds while fully modeling particle interactions within the patient. Deterministic codes are not susceptible to statistical uncertainty, but have been over-looked for applications to nuclear medicine, most likely due to their own limitations, including discretization and large memory requirements. A novel deterministic reconstruction methodology for SPECT (DRS) has been developed to apply the advantages of deterministic algorithms to SPECT iterative image reconstruction. Using a maximum likelihood expectation maximization (ML-EM) algorithm, a deterministic code can fully model particle transport in the patient in the forward projection step, without the need of a large system matrix. The TITAN deterministic transport code has a SPECT formulation that allows for fast simulation of SPECT projection images and has been benchmarked through comparison with results from the SIMIND and MCNP5 Monte Carlo codes in this dissertation. The TITAN SPECT formulation has been improved through a modified collimator representation and full parallelization. The DRS methodology has been implemented in the TITAN code to create TITAN with Image Reconstruction (TITAN-IR). The TITAN-IR code has been used to successfully reconstruct the source distribution from SPECT data for the Jaszczak and NCAT phantoms. Extensive studies have been conducted to examine the sensitivity of TITAN-IR image quality to deterministic parameter selection as well as collimator blur and noise in the projection data being reconstructed. The TITAN-IR reconstruction has also been compared with other reconstruction algorithms. This novel image reconstruction methodology has been shown to reconstruct images in short computation times, demonstrating its potential in a clinical setting with further development. / Ph. D.
13

Capabilities of a multi-pinhole SPECT system with two stationary detectors for in vivo imaging in rodents / Leistungsfähigkeit eines Multi-Pinhole SPECT-Systems mit zwei stationären Detektoren zur In-vivo-Bildgebung in Nagetiermodellen

Janßen, Jan Paul January 2023 (has links) (PDF)
Molecular imaging of rats is of great importance for basic and translational research. As a powerful tool in nuclear medicine, SPECT can be used to visualize specific functional processes in the body, such as myocardial perfusion or bone metabolism. Typical applications in laboratory animals are imaging diagnostics or the development of new tracers for clinical use. Innovations have enabled resolutions of up to a quarter of a millimeter with acceptable sensitivity. These advances have recently led to significantly more interest in SPECT both clinically and preclinically. The objective of this thesis was to evaluate the performance of the new U-SPECT5/CT E-Class by MILabs with a dedicated ultra-high resolution multi-pinhole collimator for rats and its potential for in vivo imaging of rats. The unique features of the U-SPECT are the large stationary detectors and the new iterative reconstruction algorithm. In addition, compared to the conventional system, the "E-Class" uses only two detectors instead of three. First, the sensitivity, maximum resolution, and uniformity were determined as performance parameters. Thereafter, CNRs for different activity levels comparable to those of typical in vivo activities were examined. Finally, two example protocols were carried out for imaging with 99mTc-MIBI and 99mTc-HMDP in healthy rats to evaluate the in vivo capabilities. For this purpose, CNR calculations and an image quality assessment were performed. The focus was on image quality as a function of scan time and post-reconstruction filter across a wide range of realistically achievable in vivo conditions. Performance was reasonable compared to other systems in the literature, with a sensitivity of 567 cps/MBq, a maximum resolution of 1.20 mm, and a uniformity of 55.5%. At the lower activities, resolution in phantom studies decreased to ≥1.80 mm while maintaining good image quality. High-quality bone and myocardial perfusion SPECTs were obtained in rats with a resolution of ≥1.80 mm and ≥2.20 mm, respectively. Although limited sensitivity remains a weakness of SPECT, the U-SPECT5/CT E-Class with the UHR-RM collimator can achieve in vivo results of the highest standard despite the missing third detector. Currently, it is one of the best options for high-resolution radionuclide imaging in rats. / Die molekulare Bildgebung bei Ratten hat einen hohen Stellenwert in der Grundlagenforschung und der translationale Forschung. Dabei ist SPECT ein leistungsfähiges Instrument zur Visualisierung spezifischer funktioneller Prozesse im Körper, wie z. B. der Herzmuskeldurchblutung oder des Knochenstoffwechsels. Typische Anwendungsbereiche an Labortieren sind die bildgebende Diagnostik im Rahmen von Studien oder die Entwicklung neuer Tracer für den klinischen Einsatz. Durch Innovationen wurden Auflösungen von bis zu einem Viertelmillimeter bei akzeptabler Empfindlichkeit erreichbar. Diese Fortschritte haben in letzter Zeit zu einem deutlich gestiegenen Interesse an SPECT sowohl im klinischen als auch im präklinischen Bereich geführt. Ziel dieser Arbeit war es, die Leistung des neuen U-SPECT5/CT E-Class von MILabs mit einem speziellen ultra-hochauflösenden Multi-Pinhole-Kollimator für Ratten und das Potenzial für die In-vivo-Bildgebung bei Ratten zu untersuchen. Dabei sind die Besonderheiten des U-SPECTs die großen stationären Detektoren und der neue iterative Rekonstruktionsalgorithmus. Außerdem verfügt die von uns verwendete „E-Klasse“ im Vergleich zum konventionellen System nur über zwei statt drei Detektoren. Zunächst wurden die Sensitivität, die maximale Ortsauflösung und die Homogenität als Leistungsparameter bestimmt. Anschließend wurde das Kontrast-Rausch-Verhältnis für verschiedene Aktivitätsniveaus, die mit denen typischer In-vivo-Studien vergleichbar sind, untersucht. Schließlich wurden zwei Beispielprotokolle für die Bildgebung mit 99mTc-MIBI und 99mTc-HMDP bei gesunden Ratten durchgeführt, um die In-vivo-Kapazitäten zu erfassen. Zur Bewertung wurden eine Kontrast-Rausch-Analyse und eine Bildqualitätsumfrage genutzt. Der Schwerpunkt lag dabei auf der Bildqualität in Abhängigkeit von der Scanzeit sowie dem Postrekonstruktionsfilters für ein breites Spektrum realistisch erreichbarer In-vivo-Bedingungen. Die Leistung war mit einer Sensitivität von 567 cps/MBq, einer maximalen Ortsauflösung von 1,20 mm und einer Homogenität von 55,5% mit anderen in der Literatur beschriebenen Systemen vergleichbar. Bei niedrigeren Aktivitäten verringerte sich die Auflösung in Phantomstudien auf ≥1,80 mm bei gleichbleibend guter Bildqualität. Es wurden hochqualitative Knochen- und Myokardperfusions-SPECTs mit einer Auflösung von ≥1,80 mm bzw. ≥2,20 mm bei Ratten erzielt. Obwohl die begrenzte Empfindlichkeit nach wie vor eine Schwäche der SPECT ist, kann das U-SPECT5/CT E-Class mit dem UHR-RM-Kollimator, trotz des fehlenden dritten Detektors, In-vivo-Ergebnisse auf höchstem Niveau erzielen. Es ist derzeit eine der besten Optionen für die hochauflösende Radionuklid-Bildgebung bei Ratten.
14

Investigation of Improved Quantification Techniques in Dedicated Breast SPECT-CT

Mann, Steve Dean January 2015 (has links)
<p>The work presented in this dissertation focuses on evaluation of absolute quantification accuracy in dedicated breast SPECT-CT. The overall goal was to investigate through simulations and measurements the impact and utilization of various correction methods for scattered and attenuated photons, characterization of incomplete charge collection in Cadmium Zinc Telluride detectors as a surrogate means of improving scatter correction, and resolution recovery methods for modeling collimator blur during image reconstruction. The quantification accuracy of attenuation coefficients in CT reconstructions was evaluated in geometric phantoms, and a slice-by-slice breast segmentation algorithm was developed to separate adipose and glandular tissue. All correction and segmentation methods were then applied to a pilot study imaging parathyroid patients to determine the average uptake of Tc-99m Sestamibi in healthy breast tissue, including tissue specific uptake in adipose and glandular tissue. </p><p>Monte Carlo methods were utilized to examine the changes in incident scatter energy distribution on the SPECT detector as a function of 3D detector position about a pendant breast geometry. A simulated prone breast geometry with torso, heart, and liver was designed. An ideal detector was positioned at various azimuthal and tilted positions to mimic the capabilities of the breast SPECT subsystem. The limited near-photopeak scatter energy range in simulated spectra was linearly fit and the slope used to characterize changes in scatter distribution as a function of detector position. Results show that the detected scatter distribution changes with detector tilt, with increasing incidence of high energy scattered photons at larger detector tilts. However, reconstructions of various simulated trajectories show minimal impact on quantification (<5%) compared to a primary-only reconstruction.</p><p>Two scatter compensation methods were investigated and compared to a narrow photopeak-only windowing for quantification accuracy in large uniform regions and small, regional uptake areas: 1) a narrow ±4% photopeak energy window to minimize scatter in the photopeak window, 2) the previously calibrated dual-energy window scatter correction method, and 3) a modified dual-energy window correction method that attempts to account for the effects of incomplete charge collection in Cadmium Zinc Telluride detectors. Various cylindrical phantoms, including those with imbedded hot and cold regions, were evaluated. Results show that the Photopeak-only and DEW methods yield reasonable quantification accuracy (within 10%) for a wide range of activity concentrations and phantom configurations. The mDEW demonstrated highly accurate quantification measurements in large, uniform regions with improved uniformity compared to the DEW method. However, the mDEW method is susceptible to the calibration parameters and the activity concentration of the scanned phantom. The sensitivity of the mDEW to these factors makes it a poor choice for robust quantification applications. Thus, the DEW method using a high-performance CZT gamma camera is still a better choice for quantification purposes</p><p>Phantoms studies were performed to investigate the application of SPECT vs CT attenuation correction. Minor differences were observed between SPECT and CT maps when assuming a uniformly filled phantom with the attenuation coefficient of water, except when the SPECT attenuation map volume was significantly larger than the CT volume. Material specific attenuation coefficients reduce the corresponding measured activity concentrations compared to a water-only correction, but the results do not appear more accurate than a water-only attenuation map. Investigations on the impact of image registration show that accurate registration is necessary for absolute quantification, with errors up to 14% observed for 1.5cm shifts. </p><p>A method of modeling collimator resolution within the SPECT reconstruction algorithm was investigated for its impact on contrast and quantification accuracy. Three levels of resolution modeling, each with increasing ray-sampling, were investigated. The resolution model was applied to both cylindrical and anthropomorphic breast phantoms with hot and cold regions. Large volume quantification results (background measurements) are unaffected by the application of resolution modeling. For smaller chambers and simulated lesions, contrast generally increases with resolution modeling. Edges of lesions also appear sharper with resolution modeling. No significant differences were seen between the various levels of resolution modeling. However, Gibbs artifacts are amplified at the boundaries of high contrast regions, which can significantly affect absolute quantification measurements. Convergence with resolution modeling is also notably slower, requiring more iterations with OSEM to reach a stable mean activity concentration. Additionally, reconstructions require far more computing time with resolution modeling due to the increase in number of sampling rays. Thus while the edge enhancement and contrast improvements may benefit lesion detection, the artifacts, slower convergence, and increased reconstruction time limit the utility of resolution modeling for both absolute quantification and clinical imaging studies. </p><p>Finally, a clinical pilot study was initiated to measure the average uptake of Tc-99m Sestamibi in healthy breast tissue. Subjects were consented from those undergoing diagnostic parathyroid studies at Duke. Each subject was injected with 25mCi of Sestamibi as part of their pre-surgical parathyroid SPECT imaging studies and scanned with the dedicated breast SPECT-CT system before their diagnostic parathyroid SPECT scan. Based on phantom studies of CT reconstructed attenuation coefficient accuracy, a slice-by-slice segmentation algorithm was developed to separate breast CT data into adipose and glandular tissue. SPECT data were scatter, attenuation, and decay corrected to the time of injection. Segmented CT images were used to measure average radiotracer concentration in the whole breast, as well as adipose and glandular tissue. With 8 subjects scanned, the average measured whole breast activity concentration was found to be 0.10µCi/mL. No significant differences were seen between adipose and glandular tissue uptake. </p><p>In conclusion, the application of various characterization and correct methods for quantitative SPECT imaging were investigated. Changes in detected scatter distribution appear to have minimal impact on quantification, and characterization of low-energy tailing for a modified scatter subtraction method yields inferior overall quantification results. Comparable quantification accuracy is seen with SPECT and CT-based attenuation maps, assuming the SPECT-based volume is fairly accurate. In general, resolution recovery within OSEM yields higher contrast, but quantification accuracy appears more susceptible to measurement location. Finally, scatter, attenuation, and resolution recovery methods, along with a breast segmentation algorithm, were implemented in a clinical imaging study for quantifying Tc-99m Sestamibi uptake. While the average whole breast uptake was measured to be 0. 10µCi/mL, no significant differences were seen between adipose and glandular tissue or when implementing resolution recovery. Thus, for future clinical imaging, it's recommended that the application of the investigated correction methods should be limited to the traditional DEW method and CT-based attenuation maps for quantification studies.</p> / Dissertation
15

Design and Assessment of Cardiac SPECT Systems

Lee, Chih-Jie January 2012 (has links)
Single-photon emission computed tomography (SPECT) is a modality widely used to detect myocardial ischemia and myocardial infarction. Objectively assessing and comparing different SPECT systems is important so that the best detectability of cardiac defects can be achieved. Whitaker, Clarkson, and Barrett's study on the scanning linear observer (SLO) shows that the SLO can be used to estimate the location and size of signals. One major advantage of the SLO is that it can be used with projection data rather than reconstruction data. Thus, this observer model assesses overall hardware performance independent by any reconstruction algorithm. In addition, we will show that the run time of image-quality studies is significantly reduced. Several systems derived from the GE CZT-based dedicated cardiac SPECT camera Discovery 530c design, which is officially named the Alcyone Technology: Discovery NM 530c, were assessed using the performance of the SLO for the task of detecting cardiac defects and estimating the properties of the defects. Clinically, hearts can be virtually segmented into three coronary artery territories: left anterior descending artery (LAD), left circumflex artery (LCX), and right coronary artery (RCA). One of the most important functions of a cardiac SPECT system is to produce images from which a radiologist can correctly predict in which territory the defect exists. A good estimation of the defect extent from the images is also very helpful for determining the seriousness of the myocardial ischemia. In this dissertation, both locations and extent of defects were estimated by the SLO, and system performance was assessed using localization receiver operating characteristic (LROC) / estimation receiver operating characteristic (EROC) curves. Area under LROC curve (AULC) / area under EROC curve (AUEC) and true positive fraction (TPF) at specific false positive fraction (FPF) can be treated as the figures of merit (FOMs). As the results will show, a combination of the SLO and LROC / EROC curves can determine the configuration that has the most estimation/detection information and thus is a useful method for assessing cardiac SPECT systems.
16

Differential diagnosis of parkinsonism and tremor disorders : basal ganglia imaging with a novel isotope

Amer, Hani Taha Sherif Ben January 1999 (has links)
No description available.
17

3D adaptive Wiener filter to restore brain SPECT image with reference MRI

Li, Wei January 2005 (has links)
Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.
18

Visualización de la pared inferior y Ápex cardiaco con la ingesta de agua fría en el estudio de CARDIO SPECT

Prado Cardenas, Mauricio January 2016 (has links)
Se ha realizado un estudio de tipo observacional, método descriptivo - comparativo, prospectivo y de corte transversal. Para evaluar el uso de la ingesta de agua fría como método para eliminar el artefacto de superposición intestinal en el estudio de spect miocárdica. La población de 69 casos de la clínica San Gabriel del área de radiología por medicina nuclear que se realizaron un estudio de cardio SPECT en el periodo de abril a octubre del 2015. La muestras, se seleccionó de manera no probabilística, con la modalidad intencional o por conveniencia, constituida por 9 casos que presenta incidentalmente el artefacto de superposición. El resultado mostro un 13% de artefactos de superposición. El sexo femenino muestra la mayor frecuencia con un 66.7%. La edad media en mujeres es 56,5 años y la edad media en hombres es 55 años. El uso del agua fría mostro un valor de índice kappa de 0,750 y un test de wilcoxon en cada observador con valores muy cercanos a 3 (visible). Lo cual representa una buena concordancia y un alto valor de significancia en la apreciación de la pared inferior del ápex cardiaco por los observadores post ingesta de agua fría. Conclusión: La ingesta de agua fría es efectiva en cuanto a la eliminación del artefacto de superposición intestinal en estudios de perfusión miocárdica. / --- There has been an observational study, descriptive method - comparative, prospective and cross-sectional. To evaluate the use of cold water intake as a method for removing artifact intestinal overlap in the study of myocardial SPECT. The population of 69 cases of the San Gabriel area clinic radiology nuclear medicine SPECT study of cardio performed in the period from April to October 2015. The sample was selected non probabilistic with intentional conduct or for convenience, consisting of 9 cases that incidentally presents the overlap artifact. The result showed a 13% overlap artifacts. The female shows more frequently with 66.7%. The average age for women is 56.5 years and the average age for men is 55 years. The use of cold water showed a kappa value of 0.750 and Wilcoxon test for each observer with close to 3 (visible) values. Which is a good agreement and a high value of significance in the assessment of the bottom wall of the cardiac apex by post cold water intake observers. Conclusion: Cold water intake is effective in terms of removing the artifact intestinal overlap in myocardial perfusion.
19

Variaciones de la calidad de imagen en spect óseo de columna lumbar con el método de reconstrucción iterativo – Clínica San Gabriel enero – diciembre 2014.

Chimoy Crispin, Katherine Giuliana January 2016 (has links)
OBJETIVO: Identificar las variaciones de la calidad de imagen en SPECT óseo de columna lumbar con el método de reconstrucción iterativo. MATERIAL Y MÉTODOS: Estudio observacional, explicativo, retrospectivo, transversal, que incluyó 47 estudios de imágenes de SPECT óseo de columna lumbar durante el periodo de enero a diciembre del año 2014, estos estudios fueron realizados en el área de Medicina Nuclear de la Clínica San Gabriel. Los datos fueron ingresados a programa estadístico SPSS v.22; se estimaron frecuencias, media y desviación estándar. Para el análisis relacional se determinó la distribución normal (Kolmogorov - Smirnov) y luego se aplicó la prueba estadística Kruskal-Wallis. Por último se hizo la comparación por pares por medio de la prueba U de Mann-Whitney. RESULTADOS: Se identificó que la calidad de imagen con valores de 6i x 8s y 8i x 8s presentaron los mayores valores homogéneos para las variaciones de iteraciones, por lo que se presentan como mejores puntos de referencia para una mejor calidad de imagen. Asimismo al evaluar los subconjuntos, los valores de rango promedio representan una calidad de imagen igual, observándose que la calidad de imagen con 4i x 8s y 4i x 4s presentaron los mayores valores homogéneos para las variaciones de subconjuntos. CONCLUSIÓN: Las variaciones de la calidad de imagen en SPECT óseo de columna lumbar utilizando el método de reconstrucción iterativo mejoran con 6i x 8s y 8i x 8s, puesto que con esas combinaciones el tiempo de reconstrucción de una imagen de mejor calidad sería mínimo. PALABRAS CLAVES: SPECT óseo, iteraciones, subconjuntos, calidad de imagen, método de reconstrucción iterativo. / --- OBJECTIVE: To identify the variations of image quality in lumbar spine bone SPECT using the method of iterative reconstruction. METHODOLOGY: Observational, explanatory, retrospective, cross-sectional study that includes 47 SPECT imaging studies of lumbar spine bone during the period from January to December 2014, these studies were conducted in the area of Nuclear Medicine of the San Gabriel Clinic. The data were entered into SPSS v.22, and frequencies, mean and standard deviation were estimated. Relational analysis for normal distribution (Kolmogorov - Smirnov) was determined and then applied Kruskal-Wallis. Finally the comparison was made pairwise by the Mann-Whitney U test. RESULTS: It was identified that the image quality values 6i x 8s and 8i x 8s homogeneous showed the highest values for variations of iterations, which are presented as best reference points for better image quality. Also when evaluating subassemblies, the values for represent average range equal image quality observed that the image quality 4i x 8s and 4i x 4s showed the highest values for homogeneous subsets variations. CONCLUSIONS: Variations in image quality in lumbar spine bone SPECT using the iterative reconstruction method improve with 6ix8s and 8ix8s, with these combinations the time reconstruction for a better quality imaging would be minimal. KEYWORDS: SPECT bone, iterations, subsets, image quality, iterative reconstruction method.
20

Body Deformation Correction for SPECT Imaging

Gu, Songxiang 09 July 2009 (has links)
"Single Photon Emission Computed Tomography (SPECT) is a medical imaging modality that allows us to visualize functional information about a patient's specific organ or body systems. During 20 minute scan, patients may move. Such motion will cause misalignment in the reconstruction, degrade the quality of 3D images and potentially lead to errors in diagnosis. Body bend and twist are types of patient motion that may occur during SPECT imaging and which has been generally ignored in SPECT motion correction strategies. To correct for these types of motion we propose a deformation model and its inclusion within an iterative reconstruction algorithm. One simulation and three experiments were conducted to investigate the applicability of our model. The simulation employed simulated projections of the MCAT phantom formed using an analytical projector which includes attenuation and distance-dependent resolution to investigate applications of our model in reconstruction. We demonstrate in the simulation studies that twist and bend can significantly degrade SPECT image quality visually. Our correction strategy is shown to be able to greatly diminish the degradation seen in the slices, provided the parameters are estimated accurately. To verify the correctness of our deformation model, we design the first experiment. In this experiment, the return of the post-motion-compensation locations of markers on the body-surface of a volunteer to approximate their original coordinates is used to examine our method of estimating the parameters of our model and the parameters' use in undoing deformation. Then, we design an MRI based experiment to validate our deformation model without any reconstruction. We use the surface marker motion to alter an MRI body volume to compensate the deformation the volunteer undergoes during data acquisition, and compare the motion-compensated volume with the motionless volume. Finally, an experiment with SPECT acquisitions and modified MLEM algorithm is designed to show the contribution of our deformation correction for clinical SPECT imaging. We view this work as a first step towards being able to estimate and correct patient deformation based on information obtained from marker tracking data."

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