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IUCrJ Nov 2019100 kV is investigated as the operating voltage for single-particle electron cryomicroscopy (cryoEM). Reducing the electron energy from the current standard of 300 or...
100 kV is investigated as the operating voltage for single-particle electron cryomicroscopy (cryoEM). Reducing the electron energy from the current standard of 300 or 200 keV offers both cost savings and potentially improved imaging. The latter follows from recent measurements of radiation damage to biological specimens by high-energy electrons, which show that at lower energies there is an increased amount of information available per unit damage. For frozen hydrated specimens around 300 Å in thickness, the predicted optimal electron energy for imaging is 100 keV. Currently available electron cryomicroscopes in the 100-120 keV range are not optimized for cryoEM as they lack both the spatially coherent illumination needed for the high defocus used in cryoEM and imaging detectors optimized for 100 keV electrons. To demonstrate the potential of imaging at 100 kV, the voltage of a standard, commercial 200 kV field-emission gun (FEG) microscope was reduced to 100 kV and a side-entry cryoholder was used. As high-efficiency, large-area cameras are not currently available for 100 keV electrons, a commercial hybrid pixel camera designed for X-ray detection was attached to the camera chamber and was used for low-dose data collection. Using this configuration, five single-particle specimens were imaged: hepatitis B virus capsid, bacterial 70S ribosome, catalase, DNA protection during starvation protein and haemoglobin, ranging in size from 4.5 MDa to 64 kDa with corresponding diameters from 320 to 72 Å. These five data sets were used to reconstruct 3D structures with resolutions between 8.4 and 3.4 Å. Based on this work, the practical advantages and current technological limitations to single-particle cryoEM at 100 keV are considered. These results are also discussed in the context of future microscope development towards the goal of rapid, simple and widely available structure determination of any purified biological specimen.
PubMed: 31709064
DOI: 10.1107/S2052252519012612 -
Ultramicroscopy Oct 2022The noise performance and the detection limits of a direct-counting complementary metal-oxide semiconductor (CMOS) K2 camera and a charge-coupled device (CCD) camera in...
The noise performance and the detection limits of a direct-counting complementary metal-oxide semiconductor (CMOS) K2 camera and a charge-coupled device (CCD) camera in electron energy loss spectroscopy (EELS) experiments were evaluated. In the case of a single spectrum acquired at the shortest dwell times (2.5 ms for K2 and 1 μs for CCD), the detection limit, defined as three times the standard deviation of the spectral noise (3σ), was very low (1 e/channel) in the counting-mode spectrum acquired with the K2 camera compared with that acquired with the CCD camera (5 e/channel). By contrast, the spectral noise of the K2 camera changed depending on the dwell time because of the multiple read-outs related to its fixed frame rate (400 fps). The spectral noise of the K2 camera was greater than that of the CCD camera when the dwell time was longer than ∼30 ms. Thus, the CCD camera was found to still be useful when detecting a very small number of electrons using a long acquisition time. In the case of an accumulated spectrum obtained by acquiring 10,000 spectra after subtracting the ultra-high-quality dark reference signal, the detection limits per read-out were ∼0.016 and ∼0.025 e/channel/read-out for the K2 and CCD cameras, respectively. Because both cameras have advantages and disadvantages with respect to their detection limit, speed, and dynamic range, their proper use is important.
PubMed: 35728341
DOI: 10.1016/j.ultramic.2022.113577 -
Physics in Medicine and Biology Mar 2020The in vivo sensitivity limits and quantification performance of Cerenkov luminescence imaging have been studied using a tissue-like mouse phantom and Y. For a small, 9...
The in vivo sensitivity limits and quantification performance of Cerenkov luminescence imaging have been studied using a tissue-like mouse phantom and Y. For a small, 9 mm deep target in the phantom, with no background activity present, the Cerenkov luminescence Y detection limit determined from contrast-to-noise ratios is 10 nCi for a 2 min exposure with a sensitive CCD camera and no filters. For quantitative performance, the values extracted from regions of interest on the images are linear within 5% of a straight line fit versus target activity for target activity of 70 nCi and above. The small branching ratio to decay with positron emission for Y also permits low-statistics PET imaging of the radionuclide. For PET imaging of the same phantom, with a small animal LSO detector-based scanner, the Y detection limit is approximately 3 orders of magnitude higher at 10 µCi.
Topics: Animals; Electrons; Luminescence; Mice; Phantoms, Imaging; Positron-Emission Tomography; Yttrium Radioisotopes
PubMed: 32045899
DOI: 10.1088/1361-6560/ab7502 -
The Science of the Total Environment Jun 2022Microplastics quantification and classification are demanding jobs to monitor microplastic pollution and evaluate the potential health risks. In this paper,...
Microplastics quantification and classification are demanding jobs to monitor microplastic pollution and evaluate the potential health risks. In this paper, microplastics from daily supplies in diverse chemical compositions and shapes are imaged by scanning electron microscopy. It offers a greater depth and finer details of microplastics at a wider range of magnification than visible light microscopy or a digital camera, and permits further chemical composition analysis. However, it is labour-intensive to manually extract microplastics from micrographs, especially for small particles and thin fibres. A deep learning approach facilitates microplastics quantification and classification with a manually annotated dataset including 237 micrographs of microplastic particles (fragments or beads) in the range of 50 μm-1 mm and fibres with diameters around 10 μm. For microplastics quantification, two deep learning models (U-Net and MultiResUNet) were implemented for semantic segmentation. Both significantly outmatched conventional computer vision techniques and achieved a high average Jaccard index over 0.75. Especially, U-Net was combined with object-aware pixel embedding to perform instance segmentation on densely packed and tangled fibres for further quantification. For shape classification, a fine-tuned VGG16 neural network classifies microplastics based on their shapes with high accuracy of 98.33%. With trained models, it takes only seconds to segment and classify a new micrograph in high accuracy, which is remarkably cheaper and faster than manual labour. The growing datasets may benefit the identification and quantification of microplastics in environmental samples in future work.
Topics: Deep Learning; Electrons; Microplastics; Microscopy; Plastics
PubMed: 35192829
DOI: 10.1016/j.scitotenv.2022.153903 -
Circulation. Cardiovascular Imaging Oct 2023Single-center studies have shown that single photon emission computed tomography myocardial blood flow (MBF) measurement is accurate compared with MBF measured with...
BACKGROUND
Single-center studies have shown that single photon emission computed tomography myocardial blood flow (MBF) measurement is accurate compared with MBF measured with microspheres in a porcine model, positron emission tomography, and angiography. Clinical implementation requires consistency across multiple sites. The study goal is to determine the intersite processing repeatability of single photon emission computed tomography MBF and the additional camera time required.
METHODS
Five sites (Canada, Italy, Japan, Germany, and Singapore) each acquired 25 to 35 MBF studies at rest and with pharmacological stress using technetium-99m-tetrofosmin on a pinhole-collimated cadmium-zinc-telluride-based cardiac single photon emission computed tomography camera with standardized list-mode imaging and processing protocols. Patients had intermediate to high pretest probability of coronary artery disease. MBF was measured locally and at a core laboratory using commercially available software. The time a room was occupied for an MBF study was compared with that for a standard rest/stress myocardial perfusion study.
RESULTS
With motion correction, the overall correlation in MBF between core laboratory and local site was 0.93 (range, 0.87-0.97) at rest, 0.90 (range, 0.84-0.96) at stress, and 0.84 (range, 0.70-0.92) for myocardial flow reserve. The local-to-core difference in global MBF (bias) was 5.4% (-3.8% to 14.8%; median [interquartile range]) at rest and 5.4% (-6.2% to 19.4%) at stress. Between the 5 sites, bias ranged from -1.6% to 11.0% at rest and from -1.9% to 16.3% at stress; the interquartile range in bias was between 9.3% (4.8%-14.0%) and 22.3% (-10.3% to 12.0%) at rest and between 17.0% (-11.3% to 5.6%) and 33.3% (-10.4% to 22.9%) at stress and was not significantly different between most sites. Both bias and interquartile range were like previously reported interobserver variability and less than the SD of the test-retest difference of 30%. The overall difference in myocardial flow reserve was 1.52% (-10.6% to 11.3%). There were no significant differences between with and without motion correction. The average additional acquisition time varied between sites from 44 to 79 minutes.
CONCLUSIONS
The average bias and bias values were small with standard deviations substantially less than the test-retest variability. This demonstrates that MBF can be measured consistently across multiple sites and further supports that this technique can be reliably implemented.
REGISTRATION
URL: https://www.
CLINICALTRIALS
gov; Unique identifier: NCT03427749.
Topics: Animals; Humans; Coronary Artery Disease; Coronary Circulation; Feasibility Studies; Heart; Myocardial Perfusion Imaging; Positron-Emission Tomography; Swine; Tomography, Emission-Computed, Single-Photon
PubMed: 37800325
DOI: 10.1161/CIRCIMAGING.122.015009 -
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 -
Practical Radiation Oncology 2024A 3-dimensinal (3D) stereoscopic camera system developed by .decimal was commissioned and implemented into the clinic to improve the efficiency of clinical electron...
PURPOSE
A 3-dimensinal (3D) stereoscopic camera system developed by .decimal was commissioned and implemented into the clinic to improve the efficiency of clinical electron simulations. Capabilities of the camera allowed simulations to be moved from the treatment vault into any room with a flat surface that could accommodate patient positioning devices, eliminating the need for clinical patient setup timeslots on the treatment machine. This work describes the process used for these simulations and compares the treatment parameters determined by the system to those used in delivery.
METHODS AND MATERIALS
The Decimal3D scanner workflow consisted of: scanning the patient surface; contouring the treatment area; determining gantry, couch, collimator, and source-to-surface distance (SSD) parameters for en face entry of the beam with sufficient clearance at the machine; and ordering custom electron cutouts when needed. Transparencies showing the projection of in-house library cutouts at various clinical SSDs were created to assist in choosing an appropriate library cutout. Data from 73 treatment sites were analyzed to evaluate the accuracy of the scanner-determined beam parameters for each treatment delivery.
RESULTS
Clinical electron simulations for 73 treatment sites, predominately keloids, were transitioned out of the linear accelerator (LINAC) vault using the new workflow. For all patients, gantry, collimator, and couch parameters, along with SSD and cone size, were determined using the Decimal3D scanner with 57% of simulations using library cutouts. Tolerance tables for patient setup were updated to allow differences of 10, 20, and 5° for gantry, collimator, and couch, respectively. Approximately 7% of fractions (N = 181 total fractions) were set up outside of the tolerance table based on physician direction during treatment. This reflects physician preference to adjust the LINAC rather than patient position during treatment setup. No scanner-derived plan was untreatable because of cutout shape inaccuracy or clearance issues.
CONCLUSIONS
Clinical electron simulations were successfully transitioned out of the LINAC vault using the Decimal3D scanner without loss of setup accuracy, as measured through machine parameter determination and electron cutout shape.
Topics: Humans; Radiotherapy Planning, Computer-Assisted; Electrons; Radiotherapy Dosage; Imaging, Three-Dimensional
PubMed: 38325547
DOI: 10.1016/j.prro.2024.01.005 -
Physica Medica : PM : An International... May 2024This paper reports the development of dosimeters based on plastic scintillating fibers imaged by a charge-coupled device camera, and their performance evaluation through...
This paper reports the development of dosimeters based on plastic scintillating fibers imaged by a charge-coupled device camera, and their performance evaluation through irradiations with the electron Flash research accelerator located at the Centro Pisano Flash Radiotherapy. The dosimeter prototypes were composed of a piece of plastic scintillating fiber optically coupled to a clear optical fiber which transported the scintillation signal to the readout systems (an imaging system and a photodiode). The following properties were tested: linearity, capability to reconstruct the percentage depth dose curve in solid water and to sample in time the single beam pulse. The stem effect contribution was evaluated with three methods, and a proof-of-concept one-dimensional array was developed and tested for online beam profiling. Results show linearity up to 10 Gy per pulse, and good capability to reconstruct both the timing and spatial profiles of the beam, thus suggesting that plastic scintillating fibers may be good candidates for low-energy electron Flash dosimetry.
Topics: Plastics; Electrons; Scintillation Counting; Radiation Dosimeters; Radiotherapy Dosage; Radiometry
PubMed: 38692114
DOI: 10.1016/j.ejmp.2024.103360 -
European Urology Open Science Apr 2023Prostate cancer (PCa) remains one of the leading causes of cancer-related deaths in men worldwide. Men at risk are typically offered multiparametric magnetic resonance...
A Systematic Review of the Variability in Performing and Reporting Intraprostatic Prostate-specific Membrane Antigen Positron Emission Tomography in Primary Staging Studies.
CONTEXT
Prostate cancer (PCa) remains one of the leading causes of cancer-related deaths in men worldwide. Men at risk are typically offered multiparametric magnetic resonance imaging and, if suspicious, a targeted biopsy. However, false-negative rates of magnetic resonance imaging are consistently 18%; therefore, there is growing interest in improving the diagnostic performance of imaging through novel technologies. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is being utilised for PCa staging and, more recently, for intraprostatic tumour localisation. However, significant variability has been observed in how PSMA PET is performed and reported.
OBJECTIVE
In this review, we aim to evaluate how pervasive this variability is in trials investigating the performance of PSMA PET in primary PCa workup.
EVIDENCE ACQUISITION
Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, we performed an optimal search in five different databases. After removing duplicates, 65 studies were included in our review.
EVIDENCE SYNTHESIS
Studies dated back as early as 2016, with numerous different source countries. There was variation in the reference standard for PSMA PET, with some using biopsy specimens or surgical specimens, and in some cases, a combination of the two. Similar inconsistencies were noted when studies selected histological definitions of clinically significant PCa, while some omitted their definition altogether. The most significant variations in performing PSMA PET were the radiotracer type, dose, acquisition time after injection, and the PET camera being utilised. Substantial variation in the reporting of PSMA PET was noted, with no consistency in defining what constitutes a positive intraprostatic lesion. Across 65 studies, four different definitions were used.
CONCLUSIONS
This systematic review has highlighted considerable variation in obtaining and performing a PSMA PET study in the context of primary PCa diagnosis. Given the discrepancy in how PSMA PET was performed and reported, it questions the homogony of studies from centre to centre. Standardisation of PSMA PET is required for this to become a consistently useful and reproducible modality in the diagnosis of PCa.
PATIENT SUMMARY
Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is being utilised for staging and localisation of prostate cancer (PCa); however, there is significant variability in performing and reporting PSMA PET. Standardisation of PSMA PET is required for results to be consistently useful and reproducible for the diagnosis of PCa.
PubMed: 37101769
DOI: 10.1016/j.euros.2023.01.010 -
Medical Physics Jan 2020Total skin electron therapy (TSET) utilizes high-energy electrons to treat malignancies on the entire body surface. The otherwise invisible radiation beam can be...
BACKGROUND
Total skin electron therapy (TSET) utilizes high-energy electrons to treat malignancies on the entire body surface. The otherwise invisible radiation beam can be observed via the optical Cherenkov photons emitted from interactions between the high-energy electron beam and tissue.
METHODS AND MATERIALS
With a time-gated intensified camera system, the Cherenkov emission can be used to evaluate the dose uniformity on the surface of the patient in real time. Fifteen patients undergoing TSET in various conditions (whole body and half body) were imaged and analyzed. Each patient was monitored during TSET via in vivo detectors (IVD) in nine locations. For accurate Cherenkov imaging, a comparison between IVD and Cherenkov profiles was conducted using a polyvinyl chloride board to establish the perspective corrections.
RESULTS AND DISCUSSION
With proper corrections developed in this study including the perspective and inverse square corrections, the Cherenkov imaging provided two-dimensional maps proportional to dose and projected on patient skin. The results of ratio between chest and umbilicus points were in good agreement with in vivo point dose measurements, with a standard deviation of 2.4% compared to OSLD measurements.
CONCLUSIONS
Cherenkov imaging is a viable tool for validating patient-specific dose distributions during TSET.
Topics: Adult; Aged; Aged, 80 and over; Electrons; Female; Humans; Male; Middle Aged; Optical Imaging; Radiotherapy Dosage; Skin Neoplasms
PubMed: 31665544
DOI: 10.1002/mp.13881