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Annals of Nuclear Cardiology 2022The International Study of Comparative Health Effectiveness with Medical and Invasive Approaches (ISCHEMIA) trial has had a great impact on the management of chronic... (Review)
Review
The International Study of Comparative Health Effectiveness with Medical and Invasive Approaches (ISCHEMIA) trial has had a great impact on the management of chronic coronary artery disease (CAD). One of the implications of this trial is the importance of close patient follow-up. To improve patient prognosis, evaluation of the residual extent of ischemia after treatment may be important because several studies have shown a close relationship between residual ischemia and cardiac events. For this assessment, myocardial perfusion single-photon emission computed tomography (MPS) has been utilized and is almost the only modality. Among the participants in the ISCHEMIA trial, more than 10% were excluded due to the absence of obstructive CAD. The pathophysiology of ischemia without non-obstructive coronary artery disease (INOCA) is gaining recognition; however, diagnosis is difficult, except for the assessment of myocardial flow reserve (MFR). Myocardial perfusion positron emission tomography (PET) is the most common modality for noninvasive evaluation of MFR; however, its availability in Japan is limited. For a breakthrough in this situation, a novel gamma camera with a cadmium zinc telluride (CZT) semiconductor might be one of the solutions that enables the evaluation of MFR with a commercially available perfusion tracer, similar to PET. Another solution is a novel PET tracer with a longer half-life. Clinical trials with F labeled perfusion agents have been initiated in Japan, and in a few years, delivery of this perfusion tracer will result in more frequent and easier assessment of MFR.
PubMed: 36540172
DOI: 10.17996/anc.22-00168 -
JACC. Cardiovascular Imaging Dec 2022For molecular imaging of atherosclerotic vessel wall activity, tracer kinetic analysis may yield improved contrast versus blood, more robust quantitative parameters, and...
BACKGROUND
For molecular imaging of atherosclerotic vessel wall activity, tracer kinetic analysis may yield improved contrast versus blood, more robust quantitative parameters, and more reliable characterization of systems biology.
OBJECTIVES
The authors introduce a novel dynamic whole-body positron emission tomography (PET) protocol that is enabled by rapid continuous camera table motion, followed by reconstruction of parametric data sets using voxel-based Patlak graphical analysis.
METHODS
Twenty-five subjects were prospectively enrolled and underwent dynamic PET up to 90 minutes after injection of 2-[F]fluoro-2-deoxy-D-glucose (FDG). Two sets of images were generated: 1) the established standard of static standardized uptake value (SUV) images; and 2) parametric images of the metabolic rate of FDG (MR) using the Patlak plot-derived influx rate. Arterial wall signal was measured and compared using the volume-of-interest technique, and its association with hematopoietic and lymphoid organ signal and atherosclerotic risk factors was explored.
RESULTS
Parametric MR images provided excellent arterial wall visualization, with elimination of blood-pool activity, and enhanced focus detectability and reader confidence. Target-to-background ratio (TBR) from MR images was significantly higher compared with SUV images (2.6 ± 0.8 vs 1.4 ± 0.2; P < 0.0001), confirming improved arterial wall contrast. On MR images, arterial wall signal showed improved correlation with hematopoietic and lymphoid organ activity (spleen P = 0.0009; lymph nodes P = 0.0055; and bone marrow P = 0.0202) and increased with the number of atherosclerotic risk factors (r = 0.49; P = 0.0138), where signal from SUV images (SUVP = 0.9754; TBRP = 0.8760) did not.
CONCLUSIONS
Absolute quantification of MR is feasible for arterial wall using dynamic whole-body PET imaging. Parametric images provide superior arterial wall contrast, and they might be better suited to explore the relationship between arterial wall activity, systemic organ networks, and cardiovascular risk. This novel methodology may serve as a platform for future diagnostic and therapeutic clinical studies targeting the biology of arterial wall disease.
Topics: Humans; Kinetics; Predictive Value of Tests; Positron-Emission Tomography
PubMed: 36481078
DOI: 10.1016/j.jcmg.2022.05.008 -
Radiology Oct 2019Existing surveys of radiopharmaceutical doses for U.S. nuclear medicine laboratories are of limited scope and size. Dose data are important because they can be used to...
Existing surveys of radiopharmaceutical doses for U.S. nuclear medicine laboratories are of limited scope and size. Dose data are important because they can be used to benchmark individual laboratories, understand geographic variations in practice, and provide source data for societal guidelines and appropriateness criteria. Diagnostic reference levels (DRLs) and achievable administered activities (AAAs) for 13 noncardiac adult gamma camera and PET/CT examinations were derived retrospectively from American College of Radiology accreditation data (January 1, 2015, to December 31, 2017). The calculated DRL and AAA are consistent with previously published surveys. The distributions of radiopharmaceutical doses across facilities are in general consistent but show variation within a particular examination. Analysis of dose distribution suggests this variation results from differences in clinical protocols, educational gaps, and/or equipment factors. The AAA for the surveyed facilities exceeds dose ranges proposed in societal practice guidelines for several common nuclear medicine studies. Compared with similar surveys from Europe and Japan, geographic variation is observed, with some doses greater and others lower than used in the United States. Overall, radiopharmaceutical dose variation within the United States and internationally, and deviation from societal guidelines, imply that these dose-related benchmarks may be used to further standardize and improve clinical practice.
Topics: Adult; Gamma Cameras; Humans; Nuclear Medicine; Positron Emission Tomography Computed Tomography; Radiopharmaceuticals; Reference Values; Retrospective Studies; United States
PubMed: 31407971
DOI: 10.1148/radiol.2019190623 -
Radiation Protection Dosimetry Dec 2019This study aimed to set a dose constraint for certain duties of radiological technologists in the department of nuclear medicine. From 2013 to 2017, the 5 y radiation...
This study aimed to set a dose constraint for certain duties of radiological technologists in the department of nuclear medicine. From 2013 to 2017, the 5 y radiation exposure data of employees performing PET-CT and γ-CAMERA of eight hospitals in Korea were measured individual exposure doses to estimate the frequency and set a representative dose of 75 and 95% from the low dose in the whole category is presented. The dose constraint was 5.5 mSv for PET-CT, 4.5 mSv for γ-CAMERA and 3.5 mSv for Positron Emission Tomography (PET)-Computed Tomography(CT) and Gamma CAMERA (γ-CAMERA). Therefore, it would be appropriate to set a dose-limit value of ~5 mSv corresponding to 75-80% of the individual exposure dose of radiological technologists in the department of nuclear medicine. The finding of this study may be used as reference data for setting future radiation dose limits.
Topics: Humans; Nuclear Medicine; Occupational Exposure; Positron Emission Tomography Computed Tomography; Radiation Dosage; Radiation Exposure; Radiation Protection; Radionuclide Imaging; Radiopharmaceuticals; Republic of Korea
PubMed: 31746341
DOI: 10.1093/rpd/ncz249 -
Harefuah Jul 2021Nuclear medicine (NM) in Israel started in 1952 with the use of isotopes in medicine, using I-131 for thyroid disorders, initiated by Prof. Czerniak, founder of the... (Review)
Review
Nuclear medicine (NM) in Israel started in 1952 with the use of isotopes in medicine, using I-131 for thyroid disorders, initiated by Prof. Czerniak, founder of the profession. The first institute opened in 1954. For the first three decades, NM paved the way for novel diagnoses and treatments. An increase in the number of institutes, the introduction of specially trained physicians and paramedical teams, and recognition of NM as an independent specialty, all produced increased activity. During NM's early period, functional examinations were common such as the Schilling Test (labeled vitamin B12 absorption), or blood volume in polycythemia. These were used according to clinical demands, isotopic variety and instrumentation. Diagnosis and treatment with isotopes in NM are based on target cells, functional and molecular mechanisms, absorbing the "labeled" materials reaching targets in tumors, etc. NM always integrated "theranostic" use of the same isotope for both diagnosis and treatment (like iodine). The scans were performed using rectilinear scanners, replaced by efficient gamma cameras; they developed rapidly following dramatic changes with the introduction of technetium-99m that advanced labeling and scintigraphy methods from the early 1970s, greatly improving quality and availability of scans. Gamma cameras are the basic equipment in NM, enabling whole body tomography scans, single-photon emission computerized tomography (SPECT). During the last two decades, new short-life, positron-emitter isotopic agents such as fluoride-F18-FDG were developed, requiring dedicated positron emission tomography (PET) cameras, followed by the development of integrated cameras with CT/MR (computed tomography (CT) magnetic resonance (MR)) hybrid imaging of two scan types in one camera: SPECT/CT and PET/CT/MR. This article reviews NM's development, recognition, establishment of its professional society, and arrival at the frontier of personalized medicine, in an ongoing process.
Topics: Fluorodeoxyglucose F18; Humans; Iodine Radioisotopes; Israel; Nuclear Medicine; Positron Emission Tomography Computed Tomography; Positron-Emission Tomography
PubMed: 34263576
DOI: No ID Found -
Fluorescence real-time kinetics of protoporphyrin IX after 5-ALA administration in low-grade glioma.Journal of Neurosurgery Jan 20225-Aminolevulinic acid (5-ALA) induces fluorescence in high-grade glioma (HGG), which is used for resection. However, the value of 5-ALA-induced fluorescence in low-grade...
OBJECTIVE
5-Aminolevulinic acid (5-ALA) induces fluorescence in high-grade glioma (HGG), which is used for resection. However, the value of 5-ALA-induced fluorescence in low-grade glioma (LGG) is unclear. Time dependency and time kinetics have not yet been investigated. The purpose of this study was to investigate real-time kinetics of protoporphyrin IX (PpIX) in LGG based on hyperspectral fluorescence-based measurements and identify factors that predict fluorescence.
METHODS
Patients with grade II gliomas and imaging from which HGGs could not be completely ruled out received 5-ALA at 20 mg/kg body weight 4 hours prior to surgery. Fluorescence intensity (FI) and PpIX concentration (CPpIX) were measured in tumor tissue utilizing a hyperspectral camera. Apparent diffusion coefficient (ADC)-based tumor cell density, Ki-67/MIB-1 index, chromosomal 1p/19q codeletion, and 18F-fluoroethyl-l-tyrosine (18F-FET) PET values and their role for predicting fluorescence were evaluated.
RESULTS
Eighty-one biopsies from 25 patients were included. Tissues with fluorescence demonstrated FI and CPpIX maxima between 7 and 8 hours after administration. When visible fluorescence was observed, peaks of FI and CPpIX were observed within this 7- to 8-hour time frame, regardless of any MRI gadolinium contrast enhancement. Gadolinium enhancement (p = 0.008), Ki-67/MIB-1 index (p < 0.001), 18F-FET PET uptake ratio (p = 0.004), and ADC-based tumor cellularity (p = 0.017) significantly differed between fluorescing and nonfluorescing tissue, but not 1p/19q codeletions. Logistic regression demonstrated that 18F-FET PET uptake and Ki-67/MIB-1 index were independently related to fluorescence.
CONCLUSIONS
This study reports a fluorescence-based assessment of CPpIX in human LGG tissues related to 18F-FET PET uptake and Ki-67/MIB-1. As in HGGs, fluorescence in LGGs peaked between 7 and 8 hours after 5-ALA application, which has consequences for the timing of administration.
Topics: Adult; Aminolevulinic Acid; Brain Neoplasms; Chromosome Deletion; Female; Fluorescence; Glioma; Humans; Ki-67 Antigen; Magnetic Resonance Imaging; Male; Middle Aged; Photosensitizing Agents; Positron-Emission Tomography; Protoporphyrins; Radiopharmaceuticals; Spectrometry, Fluorescence; Tyrosine
PubMed: 34144512
DOI: 10.3171/2020.10.JNS202881 -
Clinical Oncology (Royal College of... Feb 2021The aim of this review is to summarise the efforts undertaken so far to compare or standardise quantitative imaging with gamma cameras across centres for multicentre... (Review)
Review
The aim of this review is to summarise the efforts undertaken so far to compare or standardise quantitative imaging with gamma cameras across centres for multicentre trials in radionuclide therapies. Overall, 10 studies were identified, five of which were set up as a multicentre effort for standardising and comparing methods for quantitative imaging. One study used positron emission tomography imaging with I. In the remaining studies, measurements were carried out with planar imaging, single photon emission computed tomography/computed tomography (SPECT/CT) or a combination of both. Three studies used radioactive calibration sources that were traceable to national standards. Most of the studies were set up in the framework of multicentre clinical trials in an effort to obtain comparable quantification across sites. The use of state-of-the-art SPECT/CT systems and reconstructions has emerged as the method of choice for dosimetry in clinical trials for radionuclide therapies.
Topics: Calibration; Humans; Positron-Emission Tomography; Radiometry; Single Photon Emission Computed Tomography Computed Tomography
PubMed: 33277151
DOI: 10.1016/j.clon.2020.11.008 -
NeuroImage May 2023Super-resolution (SR) is a methodology that seeks to improve image resolution by exploiting the increased spatial sampling information obtained from multiple...
Super-resolution (SR) is a methodology that seeks to improve image resolution by exploiting the increased spatial sampling information obtained from multiple acquisitions of the same target with accurately known sub-resolution shifts. This work aims to develop and evaluate an SR estimation framework for brain positron emission tomography (PET), taking advantage of a high-resolution infra-red tracking camera to measure shifts precisely and continuously. Moving phantoms and non-human primate (NHP) experiments were performed on a GE Discovery MI PET/CT scanner (GE Healthcare) using an NDI Polaris Vega (Northern Digital Inc), an external optical motion tracking device. To enable SR, a robust temporal and spatial calibration of the two devices was developed as well as a list-mode Ordered Subset Expectation Maximization PET reconstruction algorithm, incorporating the high-resolution tracking data from the Polaris Vega to correct motion for measured line of responses on an event-by-event basis. For both phantoms and NHP studies, the SR reconstruction method yielded PET images with visibly increased spatial resolution compared to standard static acquisitions, allowing improved visualization of small structures. Quantitative analysis in terms of SSIM, CNR and line profiles were conducted and validated our observations. The results demonstrate that SR can be achieved in brain PET by measuring target motion in real-time using a high-resolution infrared tracking camera.
Topics: Animals; Positron Emission Tomography Computed Tomography; Motion Capture; Positron-Emission Tomography; Motion; Brain; Phantoms, Imaging; Algorithms; Image Processing, Computer-Assisted
PubMed: 36977452
DOI: 10.1016/j.neuroimage.2023.120056 -
Cancer Imaging : the Official... Apr 2024PSMA PET/CT is the most sensitive molecular imaging modality for prostate cancer (PCa), yet much of the developing world has little or no access to PET/CT. [Tc]Tc-PSMA...
BACKGROUND
PSMA PET/CT is the most sensitive molecular imaging modality for prostate cancer (PCa), yet much of the developing world has little or no access to PET/CT. [Tc]Tc-PSMA scintigraphy (PS) is a cheaper and more accessible gamma camera-based alternative. However, many resource-constrained departments have only a single camera without tomographic or hybrid imaging functionality, and camera time is frequently in high demand. Simplifying imaging protocols by limiting the field of view (FOV) and omitting SPECT/CT or even SPECT may provide a partial solution. The aim was thus to determine the adequacy of PS planar-only and/or SPECT-only imaging protocols with a limited FOV.
METHODS
The scans of 95 patients with histologically proven PCa who underwent PS with full-body planar and multi-FOV SPECT/CT were reviewed. The detection rates for uptake in the prostate gland/bed and in metastases were compared on planar, SPECT, and SPECT/CT. The agreement between modalities was calculated for the detection of metastases and for staging. The impact of imaging a limited FOV was determined.
RESULTS
Pathological prostatic uptake was seen in all cases on SPECT/CT (excluding two post-prostatectomy patients), 90.3% of cases on SPECT, and 15.1% on planar images (p < 0.001). Eleven (11.7%) patients had seminal vesicle involvement on SPECT/CT, which was undetectable/indistinguishable on planar images and SPECT. The agreement between modalities was moderate to good (κ = 0.41 to 0.61) for the detection of nodal metastases, with detection rates that did not differ significantly (SPECT/CT = 11.6%, SPECT = 8.4%, planar = 5.3%). Detection rates for bone metastases were 14.7% (SPECT/CT) and 11.6% (SPECT and planar). Agreement between modalities for the detection of bone metastases was good (κ = 0.73 to 0.77). Three (3.1%) patients had visceral metastases on SPECT/CT, two of which were detected on SPECT and planar. There was good agreement between modalities for the TNM staging of patients (κ = 0.70 to 0.88). No metastatic lesions were missed on the limited FOV images.
CONCLUSION
When PS scintigraphy is performed, SPECT/CT is recommended. However, the lack of SPECT/CT capabilities should not preclude the use of PS in the presence of limited resources, as both planar and SPECT imaging are adequate and will correctly stage most PCa patients. Furthermore, time-based optimisations are achievable by limiting the FOV to exclude the distal lower limbs.
Topics: Male; Humans; Positron Emission Tomography Computed Tomography; Retrospective Studies; Resource-Limited Settings; Tomography, Emission-Computed, Single-Photon; Single Photon Emission Computed Tomography Computed Tomography; Prostatic Neoplasms; Bone Neoplasms
PubMed: 38556864
DOI: 10.1186/s40644-024-00693-9 -
Communications Biology Apr 2022Relative to the 300-kV accelerating field, electrons accelerated under lower voltages are potentially scattered more strongly. Lowering the accelerate voltage has been...
Relative to the 300-kV accelerating field, electrons accelerated under lower voltages are potentially scattered more strongly. Lowering the accelerate voltage has been suggested to enhance the signal-to-noise ratio (SNR) of cryo-electron microscopy (cryo-EM) images of small-molecular-weight proteins (<100 kD). However, the detection efficient of current Direct Detection Devices (DDDs) and temporal coherence of cryo-EM decrease at lower voltage, leading to loss of SNR. Here, we present an electron counting algorithm to improve the detection of low-energy electrons. The counting algorithm increased the SNR of 120-kV and 200-kV cryo-EM image from a Falcon III camera by 8%, 20% at half the Nyquist frequency and 21%, 80% at Nyquist frequency, respectively, resulting in a considerable improvement in resolution of 3D reconstructions. Our results indicate that with further improved temporal coherence and a dedicated designed camera, a 120-kV cryo-electron microscope has potential to match the 300-kV microscope at imaging small proteins.
Topics: Acceleration; Algorithms; Cryoelectron Microscopy; Electrons; Proteins; Signal-To-Noise Ratio
PubMed: 35388174
DOI: 10.1038/s42003-022-03284-1