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EJNMMI Physics Apr 2023The Jagiellonian Positron Emission Tomograph is the 3-layer prototype of the first scanner based on plastic scintillators, consisting of 192 half-metre-long strips with...
BACKGROUND
The Jagiellonian Positron Emission Tomograph is the 3-layer prototype of the first scanner based on plastic scintillators, consisting of 192 half-metre-long strips with readouts at both ends. Compared to crystal-based detectors, plastic scintillators are several times cheaper and could be considered as a more economical alternative to crystal scintillators in future PETs. JPET is also a first multi-photon PET prototype. For the development of multi-photon detection, with photon characterized by the continuous energy spectrum, it is important to estimate the efficiency of J-PET as a function of energy deposition. The aim of this work is to determine the registration efficiency of the J-PET tomograph as a function of energy deposition by incident photons and the intrinsic efficiency of the J-PET scanner in detecting photons of different incident energies. In this study, 3-hit events are investigated, where 2-hits are caused by 511 keV photons emitted in [Formula: see text] annihilations, while the third hit is caused by one of the scattered photons. The scattered photon is used to accurately measure the scattering angle and thus the energy deposition. Two hits by a primary and a scattered photon are sufficient to calculate the scattering angle of a photon, while the third hit ensures the precise labeling of the 511 keV photons.
RESULTS
By comparing experimental and simulated energy distribution spectra, the registration efficiency of the J-PET scanner was determined in the energy deposition range of 70-270 keV, where it varies between 20 and 100[Formula: see text]. In addition, the intrinsic efficiency of the J-PET was also determined as a function of the energy of the incident photons.
CONCLUSION
A method for determining registration efficiency as a function of energy deposition and intrinsic efficiency as a function of incident photon energy of the J-PET scanner was demonstrated. This study is crucial for evaluating the performance of the scanner based on plastic scintillators and its applications as a standard and multi-photon PET systems. The method may be also used in the calibration of Compton-cameras developed for the ion-beam therapy monitoring and simultaneous multi-radionuclide imaging in nuclear medicine.
PubMed: 37029849
DOI: 10.1186/s40658-023-00546-7 -
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 -
European Journal of Nuclear Medicine... Jul 2023Monoclonal antibody (mAb)-based PET (immunoPET) imaging can characterise tumour lesions non-invasively. It may be a valuable tool to determine which patients may benefit...
PURPOSE
Monoclonal antibody (mAb)-based PET (immunoPET) imaging can characterise tumour lesions non-invasively. It may be a valuable tool to determine which patients may benefit from treatment with a specific monoclonal antibody (mAb) and evaluate treatment response. For Zr immunoPET imaging, higher sensitivity of state-of-the art PET/CT systems equipped with silicon photomultiplier (SiPM)-based detector elements may be beneficial as the low positron abundance of Zr causes a low signal-to-noise level. Moreover, the long physical half-life limits the amount of activity that can be administered to the patients leading to poor image quality even when using long scan durations. Here, we investigated the difference in semiquantitative performance between the PMT-based Biograph mCT, our clinical reference system, and the SiPM-based Biograph Vision PET/CT in Zr immunoPET imaging. Furthermore, the effects of scan duration reduction using the Vision on semiquantitative imaging parameters and its influence on image quality assessment were evaluated.
METHODS
Data were acquired on day 4 post 37 MBq Zr-labelled mAb injection. Five patients underwent a double scan protocol on both systems. Ten patients were scanned only on the Vision. For PET image reconstruction, three protocols were used, i.e. one camera-dependent protocol and European Association of Nuclear Medicine Research Limited (EARL) standards 1 and 2 compliant protocols. Vision data were acquired in listmode and were reprocessed to obtain images at shorter scan durations. Semiquantitative PET image parameters were derived from tumour lesions and healthy tissues to assess differences between systems and scan durations. Differently reconstructed images obtained using the Vision were visually scored regarding image quality by two nuclear medicine physicians.
RESULTS
When images were reconstructed using 100% acquisition time on both systems following EARL standard 1 compliant reconstruction protocols, results regarding semiquantification were comparable. For Vision data, reconstructed images that conform to EARL1 standards still resulted in comparable semiquantification at shorter scan durations (75% and 50%) regarding 100% acquisition time.
CONCLUSION
Scan duration of Zr immunoPET imaging using the Vision can be decreased up to 50% compared with using the mCT while maintaining image quality using the EARL1 compliant reconstruction protocol.
Topics: Humans; Positron Emission Tomography Computed Tomography; Neoplasms; Reference Standards; Antibodies, Monoclonal; Positron-Emission Tomography; Image Processing, Computer-Assisted
PubMed: 36947185
DOI: 10.1007/s00259-023-06194-4 -
Molecular Imaging and Biology Aug 2023NMDA receptors (NMDARs) dysfunction plays a central role in the physiopathology of psychiatric and neurodegenerative disorders whose mechanisms are still poorly...
PURPOSE
NMDA receptors (NMDARs) dysfunction plays a central role in the physiopathology of psychiatric and neurodegenerative disorders whose mechanisms are still poorly understood. The development of a PET (positron emission tomography) tracer able to selectively bind to the NMDARs intra-channel PCP site may make it possible to visualize NMDARs in an open and active state. We describe the in vitro pharmacological characterization of [F]-fluoroethylnormemantine ([F]-FNM) and evaluate its ability to localize activated NMDA receptors in a rat preclinical model of excitotoxicity.
PROCEDURES
The affinity of the non-radioactive analog for the intra-channel PCP site was determined in a radioligand competition assay using [H]TCP ([H]N-(1-[thienyl]cyclohexyl)piperidine) on rat brain homogenates. Selectivity was also investigated by the displacement of specific radioligands targeting various cerebral receptors. In vivo brain lesions were performed using stereotaxic quinolinic acid (QA) injections in the left motor area (M1) of seven Sprague Dawley rats. Each rat was imaged with a microPET/CT camera, 40 min after receiving a dose of 30 MBq + / - 20 of [F]-FNM, 24 and 72 h after injury. Nine non-injured rats were also imaged using the same protocol.
RESULTS
FNM displayed IC value of 13.0 ± 8.9 µM in rat forebrain homogenates but also showed significant bindings on opioid receptors. In the frontal and left somatosensory areas, [F]FNM PET detected a mean of 37% and 41% increase in [F]FNM uptake (p < 0,0001) 24 and 72 h after QA stereotaxic injection, respectively, compared to the control group.
CONCLUSIONS
In spite of FNM's poor affinity for NMDAR PCP site, this study supports the ability of this tracer to track massive activation of NMDARs in neurological diseases.
Topics: Rats; Animals; Receptors, N-Methyl-D-Aspartate; Rats, Sprague-Dawley; Phencyclidine; Brain Injuries; Positron-Emission Tomography; Brain
PubMed: 36944798
DOI: 10.1007/s11307-023-01811-y -
Saudi Pharmaceutical Journal : SPJ :... Feb 2023The paper begins by identifying the key historical elements in the development of nuclear medicine imaging, focusing on the Anger camera and single photon emission... (Review)
Review
The paper begins by identifying the key historical elements in the development of nuclear medicine imaging, focusing on the Anger camera and single photon emission computed tomography (SPECT) technologies. In this context, key reference is made to the physics of detection in Anger camera systems, especially key components such as the sodium iodide crystal, the function and performance of photomultiplier tubes, and the collimator design. It is discovered that within each component of technology, there are fundamental physical relationships that govern the performance of each component, and that overall image quality is the result of the complex interaction of all such elements. The increasing use of SPECT/CT imaging is described and illustrated with a range of typical clinical applications, which include brain, spinal, cardiac, and cancer studies. The use of CT imaging functionality allows for SPECT image correction based on compensation for absorption within tissue. Reference is also made to the basics of positron emission tomography (PET) imaging and, in particular, to the integration of PET/CT systems where the anatomy profile of the CT image is used to provide correction for photon absorption. A summary is provided of the radionuclides and radiopharmaceuticals commonly used in PET/CT imaging and a range of image studies referenced includes those of nasopharyngeal carcinoma, lung cancer investigation, brain investigation (cancer detection and dementia) and cardiac function. Reference is made to the development of "time of flight" (TOF) technology for improving of image resolution in PET/CT systems. Furthermore, SPECT/CT and PET/CT imaging systems are compared, where a key factor identified is the significantly higher number of photons detected with PET/CT technology and improved image resolution.
PubMed: 36942267
DOI: 10.1016/j.jsps.2022.12.013 -
Molecular Imaging and Biology Aug 2023The preferred nuclear medicine method for identification of hyperfunctioning parathyroid glands in hyperparathyroidism (HPT) develops continuously in relation to the...
PURPOSE
The preferred nuclear medicine method for identification of hyperfunctioning parathyroid glands in hyperparathyroidism (HPT) develops continuously in relation to the technological progress. Diagnostic methods based on PET/CT have during recent years evolved with new tracer possibilities competing with traditional scintigraphic methods. This investigation is a head-to-head comparison of Tc-99m-sestamibi SPECT/CT gamma camera scintigraphy (sestamibi SPECT/CT) and C-11-L-methionin PET/CT imaging (methionine PET/CT) for preoperative identification of hyperfunctioning parathyroid glands.
PROCEDURES
The study is a prospective cohort study including 27 patients diagnosed with primary hyperparathyroidism (PHPT). Two nuclear medicine physicians assessed all examinations independently and blinded. All scanning assessments were matched to the final surgical diagnosis as confirmed by histopathology. Biochemical monitoring of the therapeutical effects was performed preoperatively by PTH-measurements and followed postoperatively for up to 12 months. Comparisons were made for differences in sensitivity and positive predictive value (PPV).
RESULTS
Twenty-seven patients (18 females, 9 males; mean age (range): 58.9 years (34.1-79)) were enrolled into the study. The 27 patients had a total of 33 identified sites of lesions of which 28 (85%) turned out to be histopathological verified hyperfunctioning parathyroid glands. The sensitivity and PPV for sestamibi SPECT/CT were 0.71 and 0.95; that of methionine PET/CT was 0.82 and 1, respectively. Both sensitivity and PPV were slightly lower for sestamibi SPECT/CT than for methionine PET PET/CT (-0.11, 95% confidence interval (95% CI): -0.29 to 0.08; -0.05, 95% CI: -0.14 to 0.04, respectively), but not to a statistically significant extent (p=0.38 and p=0.31). The sensitivity and PPV for diagnostic CT were 0.64 (95% CI: 0.44 to 0.81) and 1 (95% CI: 0.81 to 1).
CONCLUSIONS
Methionine PET/CT performed comparable to sestamibi SPECT/CT with respect to identification and localization of hyperfunctioning parathyroid glands prior to surgery.
Topics: Male; Female; Humans; Positron Emission Tomography Computed Tomography; Carbon Radioisotopes; Hyperparathyroidism, Primary; Prospective Studies; Technetium Tc 99m Sestamibi; Radionuclide Imaging; Tomography, X-Ray Computed; Radiopharmaceuticals; Tomography, Emission-Computed, Single-Photon; Organotechnetium Compounds; Methionine; Racemethionine; Nitriles
PubMed: 36881250
DOI: 10.1007/s11307-023-01808-7 -
Radiological Physics and Technology Jun 2023This study aimed to evaluate the effects of dipotassium hydrogen phosphate (KHPO) solution density on single-photon emission computed tomography (SPECT) image quality...
This study aimed to evaluate the effects of dipotassium hydrogen phosphate (KHPO) solution density on single-photon emission computed tomography (SPECT) image quality and quantification. We used a JSP phantom containing six cylinders filled with KHPO solutions of varying densities. Computed tomography (CT) was performed, and CT values and linear attenuation coefficients were measured. Subsequently, SPECT images of an SIM bone phantom filled with Tc with/without KHPO solution were acquired using a SPECT/CT camera. The full width at half maximum (FWHM), percentage coefficient of variation (%CV), recovery coefficient, and standardized uptake value (SUV) were evaluated to investigate the impact of the KHPO solution density. The CT values and linear attenuation coefficients increased with the KHPO solution density. The CT values for cancellous and cortical bones were reflected by KHPO solution densities of 0.15-0.20 and 1.50-1.70 g/cm, respectively. FWHM values were significantly lower with the KHPO solution than those with water alone (18.0 ± 0.9 mm with water alone, 15.6 ± 0.2 mm with 0.15 g/cm KHPO, and 16.1 ± 0.3 mm with 1.49 g/cm KHPO). Although the %CVs showed no significant differences, the recovery coefficients obtained with water alone tended to be slightly lower than those obtained with the KHPO solution. The SUV obtained using the standard density of the KHPO solution differed from that obtained using the optimized density. In conclusion, SPECT image quality and quantification depends on the presence and concentration of the bone-equivalent solution. The optimal bone-equivalent solution density should be used to evaluate the bone image phantoms.
Topics: Tomography, Emission-Computed, Single-Photon; Bone Density; Tomography, X-Ray Computed; Single Photon Emission Computed Tomography Computed Tomography; Phantoms, Imaging
PubMed: 36877399
DOI: 10.1007/s12194-023-00706-5 -
Micromachines Jan 2023In this paper, a blue fluorescent organic light-emitting diode (OLED) with a 1 cm emitting area was fabricated by a solution process. The ITO/spin MADN:13%...
In this paper, a blue fluorescent organic light-emitting diode (OLED) with a 1 cm emitting area was fabricated by a solution process. The ITO/spin MADN:13% UBD-07/TPBi/Al was used as the basic structure in which to add a hole-injection layer PEDOT:PSS and an electron-injection layer LiF, respectively. The device structure was optimized to obtain a longer lifetime. Firstly, the TPBi, which is an electron transport layer and a hole-blocking layer, was added to the structure to increase the electron transport rate. When the TPBi thickness was increased to 20 nm, the luminance was 221 cd/m, and the efficiency was 0.52 cd/A at a voltage of 8 V. Since the addition of the hole-injection layer (HIL) increased the hole current but did not increase the electron current, the electron transport layer (ETL) Alq with the lowest unoccupied molecular orbital (LUMO) was added as stepped ETL to help the TPBi transport more electron current into the emitting layer. When the thickness of the TPBi/Alq was 10 nm/15 nm, the luminance reached 862 cd/m, the efficiency was 1.29 cd/A, and the lifetime increased to 252 min. Subsequently, a hole-injection layer PEDOT:PSS with a thickness of 55 nm was added to make the ITO surface flatter and to reduce the probability of a short circuit caused by the spike effect. At this time, the luminance of 311 cd/m, the efficiency of 0.64 cd/A, and the lifetime of 121 min were obtained. Following this, the thickness of the emitting layer was doubled to increase the recombination probability of the electrons and the holes. When the thickness of the emitting layer was 90 nm, and the thermal evaporation method was used, the efficiency was 3.23 cd/A at a voltage of 8V, and the lifetime was improved to 482 min. Furthermore, when the thickness of the hole-injection layer PEDOT:PSS was increased to 220 nm, the efficiency increased to 3.86 cd/A, and the lifetime was increased to 529 min. An infrared thermal image camera was employed to detect the temperature variation of the blue OLEDs. After the current was gradually increased, it was found that the heat accumulation of the device became more and more significant. When the driving current reached 50 mA, the device burnt out. It was found that the maximum temperature that the OLED device could withstand was approximately 58.83 degrees C at a current of 36.36 mA.
PubMed: 36837978
DOI: 10.3390/mi14020278 -
Diagnostic and Interventional Imaging 2023Myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) assessment with non-invasive techniques represent an important tool to evaluate both coronary artery... (Review)
Review
Myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) assessment with non-invasive techniques represent an important tool to evaluate both coronary artery disease severity and extent. Currently, cardiac positron emission tomography-computed tomography (PET-CT) is the "gold standard" for the assessment of coronary function and provides accurate estimations of baseline and hyperemic MBF and MFR. Nevertheless, due to the high cost and complexity, PET-CT is not widely used in clinical practice. The introduction of cardiac-dedicated cadmium-zinc-telluride (CZT) cameras has renewed researchers' interest on MBF quantitation by single-photon emission computed tomography (SPECT). Indeed, many studies evaluated MPR and MBF measurements by dynamic CZT-SPECT in different cohorts of patients with suspected or overt coronary artery disease. As well, many others have compared the values obtained by CZT-SPECT to the ones by PET-CT, showing good correlations in detecting significant stenosis, although with different and non-standardized cut-off values. Nevertheless, the lack of standardized protocol for acquisition, reconstruction and elaboration makes more difficult to compare different studies and to further assess the real advantages of MBF quantitation by dynamic CZT-SPECT in clinical routine. Many are the issues involved in the bright and dark sides of dynamic CZT-SPECT. They include different type of CZT cameras, different execution protocols, different tracers with different myocardial extraction fraction and distribution, different software packages with different tools and algorithms, often requiring manual post-processing elaboration. This review article provides a clear summary of the state of the art on MBF and MPR evaluation by dynamic CZT-SPECT and outlines the major issues to solve to optimize this technique.
Topics: Humans; Coronary Artery Disease; Positron Emission Tomography Computed Tomography; Tomography, Emission-Computed, Single-Photon; Cadmium; Myocardial Perfusion Imaging
PubMed: 36797156
DOI: 10.1016/j.diii.2023.02.001 -
The Review of Scientific Instruments Jan 2023Since their inception, velocity map imaging (VMI) techniques have received continued interest in their expansion from 2D to 3D momentum measurements through either...
Since their inception, velocity map imaging (VMI) techniques have received continued interest in their expansion from 2D to 3D momentum measurements through either reconstructive or direct methods. Recently, much work has been devoted to the latter of these by relating electron time-of-flight (TOF) to the third momentum component. The challenge is having a timing resolution sufficient to resolve the structure in the narrow (<10 ns) electron TOF spread. Here, we build upon the work in VMI lens design and 3D VMI measurement by using a plano-convex thick-lens (PCTL) VMI in conjunction with an event-driven camera (TPX3CAM) providing TOF information for high resolution 3D electron momentum measurements. We perform simulations to show that, with the addition of a mesh electrode to the thick-lens geometry, the resulting plano-convex electrostatic field extends the detectable electron cutoff energy range while retaining the high resolution. This design also extends the electron TOF range, allowing for a better momentum resolution along this axis. We experimentally demonstrate these capabilities by examining above-threshold ionization in xenon, where the apparatus is shown to collect electrons of energy up to ∼7 eV with a TOF spread of ∼30 ns, both of which are improved compared to a previous work by factors of ∼1.4 and ∼3.75, respectively. Finally, the PCTL-VMI is equipped with a coincident ion TOF spectrometer, which is shown to effectively extract unique 3D momentum distributions for different ionic species in a gas mixture. These techniques have the potential to lend themselves to more advanced measurements involving systems where the electron momentum distributions possess non-trivial symmetries.
PubMed: 36725611
DOI: 10.1063/5.0129900