61 |
Entwicklung eines iterativen 3D Rekonstruktionverfahrens für die Kontrolle der Tumorbehandlung mit Schwerionen mittels der Positronen-Emissions-TomographieLauckner, Kathrin January 1999 (has links)
At the Gesellschaft für Schwerionenforschung in Darmstadt a therapy unit for heavy ion cancer treatment has been established in collaboration with the Deutsches Krebsforschungszentrum Heidelberg, the Radiologische Universitätsklinik Heidelberg and the Forschungszentrum Rossendorf. For quality assurance the dual-head positron camera BASTEI (Beta Activity meaSurements at the Therapy with Energetic Ions) has been integrated into this facility. It measures ß+-activity distributions generated via nuclear fragmentation reactions within the target volume. BASTEI has about 4 million coincidence channels. The emission data are acquired in a 3D regime and stored in a list mode data format. Typically counting statstics is two to three orders of magnitude lower than those of typical PET-scans in nuclear medicine. Two iterative 3D reconstruction algorithms based on ISRA (Image Space Reconstruction Algorithm) and MLEM (Maximum Likelihood Expectation Maximization), respectively, have been adapted to this imaging geometry. The major advantage of the developed approaches are run-time Monte-Carlo simulations which are used to calculate the transition matrix. The influences of detector sensitivity variations, randoms, activity from outside of the field of view and attenuation are corrected for the individual coincidence channels. Performance studies show, that the implementation based on MLEM is the algorithm of merit. Since 1997 it has been applied sucessfully to patient data. The localization of distal and lateral gradients of the ß+-activity distribution is guaranteed in the longitudinal sections. Out of the longitudinal sections the lateral gradients of the ß+-activity distribution should be interpreted using a priori knowledge.
|
62 |
The prevalence of myocardial viability as detected by 18F-Fluorodeoxyglucose positron emission tomographyMpanya, Dineo January 2017 (has links)
A research report submitted to the Faculty of Health Sciences, University of the
Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree
of Master of Medicine.
Johannesburg, October 2017. / Background: Positron Emission Tomography (PET) is an imaging modality that
guides the revascularization management of patients with left ventricular systolic
dysfunction secondary to coronary artery disease. Segments of the myocardium
demonstrating reduced perfusion and increased or preserved 18FFluorodeoxyglucose
(18F-FDG) uptake are considered to be viable and thus suitable
for revascularization. The aim of our study was to determine the prevalence of
myocardial viability as determined by FDG-PET in our local cohort and to compare
our prevalence of myocardial viability to data published elsewhere.
Methods: We retrospectively reviewed 240 consecutive 99mTc-sestamibi
myocardial perfusion Gated Single Photon Emission Tomography (SPECT) and 18FFDG
PET reports of patients referred for evaluation of myocardial viability between
January 2009 and June 2015.
Results: 236 patients met the inclusion criteria. There were 194 (82.2%) males.
The mean age was 59.1 (SD 11.0) years. A total of 4012 segments of the left
ventricle were analyzed on the gated SPECT and reduced perfusion was noted in
1862 (46.4%) segments. Perfusion-metabolism mismatch (viable myocardium) was
observed in 586 (31.5%) out of 1862 perfusion defects. The prevalence of
myocardial viability in the study population was 61.4%. On the multivariate logistic
regression model, aspirin intake [OR:0.37; CI:0.16-0.83; p=0.016] and hypertension
[OR:0.26; CI:0.12-0.58; p=0.001] were associated with the presence of viable
myocardium. Smoking was associated with the likelihood of having non-viable
myocardium [OR:2.31; CI:1.01-5.29; p=0.048]
Conclusion: The prevalence of myocardial viability as detected by 18F FDG PET in
our local cohort is similar to prevalence rates reported in the developed world. / LG2018
|
63 |
Quantification of Respiratory Motion in Positron Emission Tomography for Precise Radiation Treatment of Lung CancerTurner, Chad January 2021 (has links)
A well-established method for treating lung cancer is curative-intent radiation therapy (RT). The most significant challenge for RT is to accurately target the lesion volume while avoiding the irradiation of surrounding healthy tissue. Currently at the Juravinski Cancer Centre (JCC), treatment plans for lung cancer patients are completed using fluorodeoxyglucose positron emission tomography (FDG-PET) and four-dimensional computed tomography (4DCT) images. There is no clear protocol, however, to compensate for respiratory motion in PET images and it is not known how lesion volumes generated from PET reflect the true volume. This project evaluated methods to optimize the use of PET images in the radiation treatment planning workflow and quantify the effects of respiratory motion. First, a 4D XCAT digital phantom was used to quantify respiratory motion and its effects on lesion displacement. A CTN physical phantom and 3D-printed irregularly shaped lesion were imaged to determine the accuracy of the PET EDGE automated segmentation algorithm (ASA). Lastly, rigid and deformable image registration techniques were used to propagate the diagnostic PET scan of the irregular lesion to the 4D planning CT. PET EDGE was used to generate target volumes which were then compared to internal target volumes (ITVs) generated from manual contouring of the 4DCT image alone.
We found that lesion displacement due to respiratory motion can be adequately modeled using a moving platform set to oscillate 1 cm and 2 cm for normal and deep breathing, respectively. Optimal target delineation was found when diagnostic PET was propagated to the planning CT using rigid image registration for lesions that experienced 1 cm of oscillatory motion during imaging. In contrast, PET EDGE would overestimate volumes in static cases and underestimate volumes in instances of 2 cm dynamic motion meant to simulate deep breathing. / Thesis / Master of Science (MSc)
|
64 |
A Positron Emission Tomography (PET)System Comparison Utilizing the American College of Radiology Accreditation PhantomBorrelli, Leonard M. January 2005 (has links)
No description available.
|
65 |
Quantitative PET/CT Imaging Based Biodistribution Validated in a Porcine Model using a Targeted Peptide Radiotracer, AMBALayman, Ricky R., Jr 25 September 2013 (has links)
No description available.
|
66 |
MRI-Based Attenuation Correction for PET ReconstructionSteinberg, Jeffrey 12 September 2008 (has links)
No description available.
|
67 |
Characterization of Center-of-Mass and Rebinning in Positron Emission Tomography with Motion / Karaktärisering av masscentrum och händelseuppdatering i positronemissionstomografi med rörelseHugo, Linder January 2021 (has links)
Medical molecular imaging with positron emission tomography (PET) is sensitive to patient motion since PET scans last several minutes. Despite advancements in PET, such as improved photon-pair time-of-flight (TOF) difference resolution, motion deformations limit image resolution and quantification. Previous research of head motion tracking has produced the data-driven centroid-of-distribution (COD) algorithm. COD generates a 3D center-of-mass (COM) over time via raw list-mode PET data, which can guide motion correction such as gating and event rebinning in non-TOF PET. Knowledge gaps: COD could potentially benefit from sinogram corrections used in image reconstruction, while rebinning has not extended to TOF PET. Methods: This study develops COD with event mass (incorporating random correction and line-of-response (LOR) normalization) and a simplistic TOF rebinner. In scans of phantoms and moving heads with F11 flouro-deoxy-glucose (FDG) tracer, COD alternatives are evaluated with a signal-to-noise ratio (SNR) via linear fit to image COM, while rebinning is evaluated with mean squared error (MSE). Results: COD SNR did not benefit from a corrected event mass. The prototype TOF rebinning reduced MSE, although there were discretization errors and event loss at extreme bins for LOR and TOF due to the simplistic design, which introduced image artifacts. In conclusion, corrected event mass in COD is not promising, while TOF rebinning appears viable if techniques from state-of-the-art LOR rebinning are incorporated.
|
68 |
Attenuation Correction in Positron Emission Tomography Using Single Photon Transmission MeasurementDekemp, Robert A. 09 1900 (has links)
Accurate attenuation correction is essential for quantitative positron emission
tomography. Typically, this correction is based on a coincidence transmission
measurement using an external source of positron emitter, which is positioned close to
the detectors. This technique suffers from poor statistical quality and high dead time
losses, especially with a high transmission source strength.
We have proposed and tested the use of single photon transmission measurement
with a rotating rod source, to measure the attenuation correction factors (ACFs). The
singles projections are resampled into the coincidence geometry using the detector
positions and the r,)d source location. A nonparalyzable dead time correction algorithm
was developed for the block detectors used in the McMaster PET scanner.
Transaxial resolution is approximately 6 mm, which is comparable to emission
scanning performance. Axial resolution is about 25 mm, with only crude source
collimation. ACFs are underestimated by approximately 10% due to increased crossplane
scatter, compared to coincidence transmission scanning. Effective source
collimation is necessary to obtain suitable axial resolution and improved accuracy. The
response of the correction factors to object density is linear to within 15%, when
comparing singles transmission measurement to current coincidence transmission
measurement.
The major advantage of using singles transmission measurement IS a
dramatically increased count rate. A factor of seven increase in count rate over
coincidence scanning is possible with a 2 mCi transmission rod source. There are no
randoms counted in singles transmission scans, which makes the measured count rate
nearly linearly proportional with source activity. Singles detector dead time is
approximately 6% in the detectors opposite a 2 mCi rod source.
Present hardware and software precludes the application of this technique in a
clinical environment. We anticipate that real time acquisition of detector singles can
reduce the transmission scanning time to under 2 minutes, and produce attenuation
coefficient images with under 2% noise. This is a significant improvement compared
to the current coincidence transmission technique. / Thesis / Master of Science (MS)
|
69 |
A Method for Pixel-By-Pixel Absolute Quantitation in Positron Emission TomographyPopescu, Alina 08 1900 (has links)
This study attempts to develop a method for absolute
quantitation in Positron Emission Tomography. This includes the
definition of the dimension and the position of a tumour in the
brain as well as the evaluation of the amount of drug delivered
to the tumour and to surrounding tissues in a pixel-by-pixel way,
from the image. The defined objectives can be achieved using the
calibrated FWHM values of the distribution of events in the tumour
image, versus distance, to determine the dimension and the
position of the tumour. The concentration activity in the tumour
and the tumour-to-nontumour activity ratios can be obtained from
the image, using a modified filter and the calibration of the
tomograph. The colour scale of the image can be expressed in
absolute units (μCi/ml) and the concentration activity can be
evaluated in each pixel of the image or in each volume element of
the body. / Thesis / Master of Science (MS)
|
70 |
Étude et développement d'un imageur TEP ambulatoire pour le suivi thérapeutique individualisé en cancérologie / Study and development of a PET device dedicated to cancer monitoringVandenbussche, Vincent 30 September 2014 (has links)
L'imagerie médicale remonte à la fin du XIXe siècle avec la découverte des rayons X par Röntgen. Depuis, de nombreuses modalités d'imagerie ont été développées, et sont aujourd'hui utilisées dans une large gamme d'indications cliniques. L'imagerie TEP (Tomographie par Émission de Positron) est une modalité fonctionnelle, quantitative et ayant une haute sensibilité, ce qui en fait une modalité de choix, notamment en cancérologie. Hélas, sa diffusion est freinée en comparaison avec le scanner ou l'imagerie par résonance magnétique, en raison de son coût notamment. C'est dans ce contexte que s'insère cette thèse, qui a pour objectif de montrer la faisabilité d'un imageur TEP ambulatoire dédié au suivi thérapeutique en cancérologie. À partir de développements instrumentaux originaux (localisation des gammas par division de lumière dans des barreaux scintillateurs, lecture à l'aide de Silicon PhotoMultiplier, géométrie compacte), ces travaux s'efforcent de baisser les coûts tout en restant compétitif en terme de performances. Dans un premier temps, une étude extensive de la division de lumière à travers toute une série de paramètres (longueur des barreaux scintillateurs, revêtement optique, matériau scintillateur, traitement des données) a été menée. Une résolution spatiale inférieure à 5 mm pour un barreau de 75 mm de LYSO emballé dans du teflon a notamment été obtenue. À partir de cette configuration, une première image a été reconstruite, à partir de deux modules en coïncidence, offrant une résolution spatiale de 5 mm pour un tel imageur. Enfin, toute une série de simulations a été menée, à partir des données expérimentales et avec une géométrie originale. En particulier, les performances ont été mesurées à partir du protocole NEMA, un standard permettant de comparer les performances à travers la littérature. Une résolution spatiale intrinsèque de l'ordre de 4 mm a été obtenue, soit meilleure que le marché actuel. La sensibilité de l'ordre de 2.5 cps/kBq est revanche relativement basse par rapport à l'existant, mais s'explique par un champ de vue axial restreint. Enfin, le potentiel en terme de quantification a été adressé, et est comparable au marché actuel. / Medical imaging first began at the end of the XIXth century with the discover of X-rays by Röntgen. Then, numerous imaging modalities have been developed and are used now for a wide range of cases. Positron Emission Tomography (PET) has a high sensitivity, is functional and quantitative, thus being of high interest in cancer monitoring. Nevertheless, PET is not as much spread in hospitals as magnetic resonance imaging and scanner. In this context, this work aims to prove the faisability of PET dedicated for cancer monitoring. Thanks to instrumental developments such as light sharing in scintillating crystals, use of Silicon Photomultipliers, and an original geometry, cost is expected to be reduced while having same performances as commercial devices. An extensive study of light sharing within scintillating barrels has been made, through many parameters (crystal length, coating, data analysis...). An intrinsic spatial resolution of 4 mm has been measured over a 75 mm long crystal of LYSO, coated with teflon. From such a configuration, a first image has been reconstructed using two modules in coincidence. A spatial resolution of 5 mm has been measured in the image. Finally, Monte Carlo simulations has been made with experimental data as input, in order to measure the performances of the final PET device. Thanks to NEMA standard protocol, performances has been measured and compared to other systems. A spatial resolution of 4 mm has been reached, for a sensitivity of 2.5 cps/kBq. Quantification problem has been assessed, providing results similar to existing devices.
|
Page generated in 0.2173 seconds