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Nuclear Medicine Communications Sep 1996Optimized positron emission tomographs have begun to demonstrate an ever widening range of clinical applications for positron labelled pharmaceuticals. This potential... (Review)
Review
Optimized positron emission tomographs have begun to demonstrate an ever widening range of clinical applications for positron labelled pharmaceuticals. This potential has led to a renewed interest in the use of the more widely available Anger gamma camera detectors for imaging the 511 keV photons from the positron decay process. Two forms of detection can be considered: either the detection of the 511 keV photons as single events or the detection of coincidence events from the opposed pair annihilation photons. The widespread availability of dual, opposed-pair, large field-of-view detectors has promoted the development of coincidence detection without collimation. With detector rotation, positron emission tomography (PET) can be performed. An alternative and lower cost option has been the universal development of ultra high-energy collimators to perform single photon emission tomography (SPET) with 511 keV photons. This review outlines the currently available performance characteristics of these two approaches and compares them with those from two- and three-dimensional PET optimized systems. The limitations on the development of these systems is discussed through the analysis of the principles underlying both single photon and coincidence detection. Preliminary clinical experience indicates that limitations in the performance characteristics of these systems has implications for their potential role, although applications in cardiology and oncology are being pursued.
Topics: Gamma Cameras; Humans; Image Processing, Computer-Assisted; Nuclear Medicine; Scattering, Radiation; Sensitivity and Specificity; Tomography, Emission-Computed
PubMed: 8895903
DOI: 10.1097/00006231-199609000-00006 -
Frontiers of Hormone Research 2016Radioactive isotopes of radioiodine are frequently used in differentiated thyroid carcinoma (DTC) both for diagnosis and therapy. Their accumulation in thyroid cancer... (Review)
Review
Radioactive isotopes of radioiodine are frequently used in differentiated thyroid carcinoma (DTC) both for diagnosis and therapy. Their accumulation in thyroid cancer tissue is dependent on the expression and activity of the sodium-iodide symporter (NIS). Scintigraphic imaging using either planar or single-photon emission computed tomography (SPECT) cameras allows the visualization of their distribution within the human body. Due to only a poor visualization of morphology by these techniques, their diagnostic accuracy is, however, limited. This limitation is overcome when hybrid systems integrating a SPECT camera with an X-ray CT scanner are used. Roughly one third of patients with diagnostically unclear foci of radioiodine accumulation will benefit from the use of SPECT/CT, also in terms of therapeutic management. SPECT/CT has, therefore, become the gold standard of nuclear imaging in DTC. NIS expression may be absent in DTC. In this case, the glucose transporters are usually upregulated. Therefore, PET/CT using 18F-deoxyglucose can be used to diagnose and localize tumor recurrence as a prerequisite to, in particular, surgical intervention.
Topics: Humans; Positron Emission Tomography Computed Tomography; Single Photon Emission Computed Tomography Computed Tomography; Thyroid Neoplasms
PubMed: 27003310
DOI: 10.1159/000442276 -
Journal of Nuclear Medicine : Official... May 1990A high-resolution, whole-body positron camera, POSICAM 6.5 BGO, has been designed, built, and tested; results from it are presented. The camera utilizes 1,320 BGO...
A high-resolution, whole-body positron camera, POSICAM 6.5 BGO, has been designed, built, and tested; results from it are presented. The camera utilizes 1,320 BGO crystals and 720 PMTS in a staggered geometry to produce high resolution of 5.8 mm FWHM and 21 image planes simultaneously. The axial resolution of the camera is measured at 11.9 mm at the center. High axial sampling is achieved with 5.125 mm separation of the image planes such that three-dimensional imaging of an object can be carried out in a single scan. Recovery of volumetric distribution of radioactivity and object dimensions in axial and sagittal views is demonstrated by imaging spherical objects 13 mm to 39 mm in diameter.
Topics: Equipment Design; Evaluation Studies as Topic; Tomography, Emission-Computed
PubMed: 2341897
DOI: No ID Found -
Physics in Medicine and Biology Jul 1978A positron camera is proposed for nuclear medical imaging of radionuclide distributions in a series of isolated planes. This three-dimensional localisation is achieved...
A positron camera is proposed for nuclear medical imaging of radionuclide distributions in a series of isolated planes. This three-dimensional localisation is achieved through analysis of four time signals, whose differences directly measure the position (x, y, z) of individual positron annihilation events. A tetrahedronal symmetry is exploited, with two skewed plastic scintillator bars spanning a large sensitive volume. Phototubes on each end of both bars generate fast timing pulses uniquely determining the decay position through a time-of-flight technique. The mathematical properties of the transformation from the observed quantities to the spatial distribution of the radionuclide are investigated. A discussion of the efficiency of the system and the effects of Compton scattering in tissue is given. A one-dimensional pilot study encourages the development of the prototype three-dimensional positron camera.
Topics: Gamma Rays; Radionuclide Imaging
PubMed: 704671
DOI: 10.1088/0031-9155/23/4/010 -
Journal of Cardiology Apr 20092-[(18)F] fluoro-2-deoxy-D-glucose ((18)F-FDG) began to be supplied commercially to our hospital, which does not have a cyclotron, in autumn of 2005. The purpose of this... (Comparative Study)
Comparative Study
Practical assessment of myocardial viability with a positron coincidence gamma camera using 18F-fluorodeoxyglucose in acute myocardial infarction: comparison with dedicated positron emission tomography and 201Tl single photon emission computed tomography.
OBJECTIVE
2-[(18)F] fluoro-2-deoxy-D-glucose ((18)F-FDG) began to be supplied commercially to our hospital, which does not have a cyclotron, in autumn of 2005. The purpose of this study was to compare the utility of a dual-head positron coincidence detection (PCD) gamma camera in the detection of myocardial viability using (18)F-FDG with that of dedicated positron emission tomography (PET) and with that of thallium-201 ((201)Tl) single photon emission computed tomography (SPECT).
METHODS
A total of 15 patients (14 men and 1 woman, mean age: 60+/-7 years, range: 46-73) with a large acute myocardial infarction (AMI) underwent (18)F-FDG PET, (18)F-FDG PCD imaging after oral glucose loading (75 g) and (201)Tl SPECT imaging. We divided the SPECT and PET images into a total of 20 segments, and semiquantitative visual analysis was performed by assessing regional tracer activities on a 4-point scoring system (DS): 0=normal uptake, 1=mildly reduced uptake, 2=severely reduced uptake, and 3=no uptake. We summed the DS in each patient as the total DS (TDS).
RESULTS
The TDS of the (18)F-FDG PET image was 14.4+/-7.7. The TDS of the (18)F-FDG PCD image was 18.7+/-7.7. The TDS of the (201)Tl SPECT image was 24.1+/-11.5. The TDS of the (18)F-FDG PET image was significantly smaller than that of the (18)F-FDG PCD image. The TDS of the (18)F-FDG PET image was significantly smaller than that of the (201)Tl SPECT image. The TDS of the (18)F-FDG PCD image was significantly smaller than that of the (201)Tl SPECT image.
CONCLUSION
The findings of the project suggest that (18)F-FDG PCD is a good modality based on its accuracy, convenience, and cost-performance for detecting myocardial viability in hospitals that do not have a PET system.
Topics: Aged; Female; Fluorodeoxyglucose F18; Gamma Cameras; Heart; Humans; Male; Middle Aged; Myocardial Infarction; Positron-Emission Tomography; Thallium Radioisotopes; Tissue Survival; Tomography, Emission-Computed, Single-Photon
PubMed: 19304132
DOI: 10.1016/j.jjcc.2008.11.009 -
Heliyon Oct 2020Accurate, robust and reproducible delineation of tumour in Positron Emission Tomography (PET) is essential for diagnosis, treatment planning and response assessment.... (Review)
Review
Accurate, robust and reproducible delineation of tumour in Positron Emission Tomography (PET) is essential for diagnosis, treatment planning and response assessment. Since standardized uptake value (SUV) - a normalized semiquantitative parameter used in PET is represented by the intensity of the PET images and related to the radiotracer uptake, a SUV based threshold method is a natural choice to delineate the tumour. However, determination of an optimum threshold value is a challenging task due to low spatial resolution, and signal-to-noise ratio (SNR) along with finite image sampling constraint. The aim of the review is to summarize different fixed and adaptive threshold-based PET image segmentation approaches under a common mathematical framework Advantages and disadvantages of different threshold based methods are also highlighted from the perspectives of diagnosis, treatment planning and response assessment. Several fixed threshold values (30%-70% of the maximum SUV of the tumour (SUV)) have been investigated. It has been reported that the fixed threshold-based method is very much dependent on the SNR, tumour to background ratio (TBR) and the size of the tumour. Adaptive threshold-based method, an alternative to fixed threshold, can minimize these dependencies by accounting for tumour to background ratio (TBR) and tumour size. However, the parameters for the adaptive methods need to be calibrated for each PET camera system (e.g., scanner geometry, image acquisition protocol, reconstruction algorithm etc.) and it is not straight forward to implement the same procedure to other PET systems to obtain similar results. It has been reported that the performance of the adaptive methods is also not optimum for smaller volumes with lower TBR and SNR. Statistical analysis carried out on the NEMA thorax phantom images also indicates that regions segmented by the fixed threshold method are significantly different for all cases. On the other hand, the adaptive method provides significantly different segmented regions only for low TBR with different SNR. From this viewpoint, a robust threshold based segmentation method that will be less sensitive to , SNR, TBR and volume needs to be developed. It was really challenging to compare the performance of different threshold-based methods because the performance of each method was tested on dissimilar data set with different data acquisition and reconstruction protocols along with different TBR, SNR and volumes. To avoid such difficulties, it will be desirable to have a common database of clinical PET images acquired with different image acquisition protocols and different PET cameras to compare the performance of automatic segmentation methods. It is also suggested to report the changes in SNR and TBR while reporting the response using threshold based methods.
PubMed: 33163642
DOI: 10.1016/j.heliyon.2020.e05267 -
Journal of Nuclear Medicine : Official... Oct 1987A prototype positron camera has been constructed consisting of two high density avalanche chamber (HIDAC) detectors operated in coincidence with a resolving time (2 tau)...
A prototype positron camera has been constructed consisting of two high density avalanche chamber (HIDAC) detectors operated in coincidence with a resolving time (2 tau) of 40 nsec. The detectors are multiwire chambers, with specially constructed lead converters added to improve the photon detection efficiency at 511 keV. The current HIDAC detectors have a singles efficiency of approximately 12%, a sensitive area of 31 X 31 cm and an intrinsic spatial resolution of less than 2 mm full width at half maximum (FWHM). During data acquisition, the detectors are rotated around the patient in order to collect a complete angular data set. A three-dimensional image of the positron distribution is reconstructed from a single scan by weighted backprojection of the data into a matrix of either 64 X 64 X 64 or 128 X 128 X 16 voxels. The camera point response function is deconvolved by frequency-space filtering. Corrections are made during backprojection both for photon attenuation and for spatial variations in point source sensitivity. The reconstructed image is further corrected for contributions from accidental and scattered coincidences and displayed as a sequence of two-dimensional transverse, sagittal, or coronal sections. In addition, three-dimensional display is available using shaded graphics techniques. The prototype camera is currently undergoing clinical evaluation.
Topics: Bone Neoplasms; Brain Neoplasms; Humans; Liver Neoplasms; Models, Structural; Thyroid Gland; Tomography, Emission-Computed
PubMed: 3498804
DOI: No ID Found -
Acta Otorrinolaringologica Espanola 2004Positron Emission Tomography (PET) with 18F-Fluordeoxyglucose is a diagnostic imaging technique very useful in the management of head and neck cancer, better than... (Review)
Review
Positron Emission Tomography (PET) with 18F-Fluordeoxyglucose is a diagnostic imaging technique very useful in the management of head and neck cancer, better than anatomic imaging in most cases. PET shows higher diagnostic accuracy in the detection of local and regional tumor recurrences. PET is also indicated for the identification of unknown primary tumors when regional nodal metastasis is the presenting feature. The improved planning of radiation therapy with hybrid cameras PET-CT, the earlier diagnosis of post-radiotherapy residual disease and the possibility of monitoring the effects of chemotherapy makes PET imaging an important tool in evaluating tumor response to treatment.
Topics: Algorithms; Head and Neck Neoplasms; Humans; Neoplasm Staging; Positron-Emission Tomography
PubMed: 15554584
DOI: 10.1016/s0001-6519(04)78527-1 -
Seminars in Nuclear Medicine May 2011Cardiac imaging with radiotracers plays an important role in patient evaluation, and the development of suitable imaging instruments has been crucial. While initially... (Review)
Review
Cardiac imaging with radiotracers plays an important role in patient evaluation, and the development of suitable imaging instruments has been crucial. While initially performed with the rectilinear scanner that slowly transmitted, in a row-by-row fashion, cardiac count distributions onto various printing media, the Anger scintillation camera allowed electronic determination of tracer energies and of the distribution of radioactive counts in 2D space. Increased sophistication of cardiac cameras and development of powerful computers to analyze, display, and quantify data has been essential to making radionuclide cardiac imaging a key component of the cardiac work-up. Newer processing algorithms and solid state cameras, fundamentally different from the Anger camera, show promise to provide higher counting efficiency and resolution, leading to better image quality, more patient comfort and potentially lower radiation exposure. While the focus has been on myocardial perfusion imaging with single-photon emission computed tomography, increased use of positron emission tomography is broadening the field to include molecular imaging of the myocardium and of the coronary vasculature. Further advances may require integrating cardiac nuclear cameras with other imaging devices, ie, hybrid imaging cameras. The goal is to image the heart and its physiological processes as accurately as possible, to prevent and cure disease processes.
Topics: Animals; Diagnostic Imaging; Gamma Cameras; Heart; Humans; Image Processing, Computer-Assisted; Radionuclide Imaging; Software; Systems Integration
PubMed: 21440695
DOI: 10.1053/j.semnuclmed.2010.12.007 -
Journal of Nuclear Cardiology :... Feb 2018As the second term of our commitment to Journal begins, we, the editors, would like to reflect on a few topics that have relevance today. These include prognostication... (Review)
Review
As the second term of our commitment to Journal begins, we, the editors, would like to reflect on a few topics that have relevance today. These include prognostication and paradigm shifts; Serial testing: How to handle data? Is the change in perfusion predictive of outcome and which one? Ischemia-guided therapy: fractional flow reserve vs perfusion vs myocardial blood flow; positron emission tomography (PET) imaging using Rubidium-82 vs N-13 ammonia vs F-18 Flurpiridaz; How to differentiate microvascular disease from 3-vessel disease by PET? The imaging scene outside the United States, what are the differences and similarities? Radiation exposure; Special issues with the new cameras? Is attenuation correction needed? Are there normal databases and are these specific to each camera system? And finally, hybrid imaging with single-photon emission tomography or PET combined with computed tomography angiography or coronary calcium score. We hope these topics are of interest to our readers.
Topics: Ammonia; Coronary Artery Disease; Coronary Circulation; Coronary Vessels; Databases, Factual; Fractional Flow Reserve, Myocardial; Humans; Microcirculation; Multimodal Imaging; Myocardial Ischemia; Myocardial Perfusion Imaging; Nitrogen Radioisotopes; Positron Emission Tomography Computed Tomography; Positron-Emission Tomography; Predictive Value of Tests; Prognosis; Pyridazines; Rubidium Radioisotopes; Tomography, Emission-Computed, Single-Photon; United States
PubMed: 29110288
DOI: 10.1007/s12350-017-1093-7