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Cancers Sep 2023Prostate cancer (PCa) is one of the most prevalent cancer diagnoses among men in the United States and in several other developed countries. The prostate specific... (Review)
Review
Prostate cancer (PCa) is one of the most prevalent cancer diagnoses among men in the United States and in several other developed countries. The prostate specific membrane antigen (PSMA) has been recognized as a promising molecular target in PCa, which has led to the development of specific radionuclide-based tracers for imaging and radiopharmaceuticals for PSMA targeted therapy. These compounds range from small molecule ligands to monoclonal antibodies (mAbs). Monoclonal antibodies play a crucial role in targeting cancer cell-specific antigens with a high degree of specificity while minimizing side effects to normal cells. The same mAb can often be labeled in different ways, such as with radionuclides suitable for imaging with Positron Emission Tomography (β+ positrons), Gamma Camera Scintigraphy (γ photons), or radiotherapy (β- electrons, α-emitters, or Auger electrons). Accordingly, the use of radionuclide-based PSMA-targeting compounds in molecular imaging and therapeutic applications has significantly grown in recent years. In this article, we will highlight the latest developments and prospects of radiolabeled mAbs that target PSMA for the detection and treatment of prostate cancer.
PubMed: 37760506
DOI: 10.3390/cancers15184537 -
Medical Physics Jul 2023During recent years FLASH radiotherapy (FLASH-RT) has shown promising results in radiation oncology, with the potential to spare normal tissue while maintaining the...
BACKGROUND
During recent years FLASH radiotherapy (FLASH-RT) has shown promising results in radiation oncology, with the potential to spare normal tissue while maintaining the antitumor effects. The high speed of the FLASH-RT delivery increases the need for fast and precise motion monitoring to avoid underdosing the target. Surface guided radiotherapy (SGRT) uses surface imaging (SI) to render a 3D surface of the patient. SI provides real-time motion monitoring and has a large scanning field of view, covering off-isocentric positions. However, SI has so far only been used for human patients with conventional setup and treatment.
PURPOSE
The aim of this study was to investigate the performance of SI as a motion management tool during electron FLASH-RT of canine cancer patients.
METHODS
To evaluate the SI system's ability to render surfaces of fur, three fur-like blankets in white, grey, and black were used to imitate the surface of canine patients and the camera settings were optimized for each blanket. Phantom measurements using the fur blankets were carried out, simulating respiratory motion and sudden shift. Respiratory motion was simulated using the QUASAR Respiratory Motion Phantom with the fur blankets placed on the phantom platform, which moved 10 mm vertically with a simulated respiratory period of 4 s. Sudden motion was simulated with an in-house developed phantom, consisting of a platform which was moved vertically in a stepwise motion at a chosen frequency. For sudden measurements, 1, 2, 3, 4, 5, 6, 7, and 10 Hz were measured. All measurements were both carried out at the conventional source-to-surface distance (SSD) of 100 cm, and in the locally used FLASH-RT setup at SSD = 70 cm. The capability of the SI system to reproduce the simulated motion and the sampling time were evaluated. As an initial step towards clinical implementation, the feasibility of SI for surface guided FLASH-RT was evaluated for 11 canine cancer patients.
RESULTS
The SI camera was capable of rendering surfaces for all blankets. The deviation between simulated and measured mean peak-to-peak breathing amplitude was within 0.6 mm for all blankets. The sampling time was generally higher for the black fur than for the white and grey fur, for the measurement of both respiratory and sudden motion. The SI system could measure sudden motion within 62.5 ms and detect motion with a frequency of 10 Hz. The feasibility study of the canine patients showed that the SI system could be an important tool to ensure patient safety. By using this system we could ensure and document that 10 out of 11 canine patients had a total vector offset from the reference setup position <2 mm immediately before and after irradiation.
CONCLUSIONS
We have shown that SI can be used for surface guided FLASH-RT of canine patients. The SI system is currently not fast enough to interrupt a FLASH-RT beam while irradiating but with the short sampling time sudden motion can be detected. The beam can therefore be held just prior to irradiation, preventing treatment errors such as underdosing the target.
Topics: Humans; Animals; Dogs; Electrons; Neoplasms; Diagnostic Imaging; Phantoms, Imaging; Radiotherapy Planning, Computer-Assisted
PubMed: 37190907
DOI: 10.1002/mp.16453 -
Seminars in Nuclear Medicine Jul 2020Autonomic innervation plays an important role in proper functioning of the cardiovascular system. Altered cardiac sympathetic function is present in a variety of... (Review)
Review
Autonomic innervation plays an important role in proper functioning of the cardiovascular system. Altered cardiac sympathetic function is present in a variety of diseases, and can be assessed with radionuclide imaging using sympathetic neurotransmitter analogues. The most studied adrenergic radiotracer is cardiac I-meta-iodobenzylguanidine (I-mIBG). Cardiac I-mIBG uptake can be evaluated using both planar and tomographic imaging, thereby providing insight into global and regional sympathetic innervation. Standardly assessed imaging parameters are the heart-to-mediastinum ratio and washout rate, customarily derived from planar images. Focal tracer deficits on tomographic imaging also show prognostic utility, with some data suggesting that the best approach to tomographic image interpretation may differ from conventional methods. Cardiac I-mIBG image findings strongly correlate with the severity and prognosis of many cardiovascular diseases, especially heart failure and ventricular arrhythmias. Cardiac I-mIBG imaging in heart failure is FDA approved for prognostic purposes. With the robustly demonstrated ability to predict occurrence of potentially fatal arrhythmias, cardiac I-mIBG imaging shows promise for better selecting patients who will benefit from an implantable cardioverter defibrillator, but clinical use has been hampered by lack of the randomized trial needed for incorporation into societal guidelines. In patients with ischemic heart disease, cardiac I-mIBG imaging aids in assessing the extent of damage and in identifying arrhythmogenic regions. There have also been studies using cardiac I-mIBG for other conditions, including patients following heart transplantation, diabetic related cardiac abnormalities and chemotherapy induced cardiotoxicity. Positron emission tomographic adrenergic radiotracers, that improve image quality, have been investigated, especially C-meta-hydroxyephedrine, and most recently F-fluorbenguan. Cadmium-zinc-telluride cameras also improve image quality. With better spatial resolution and quantification, PET tracers and advanced camera technologies promise to expand the clinical utility of cardiac sympathetic imaging.
Topics: 3-Iodobenzylguanidine; Heart; Humans; Positron-Emission Tomography; Radioactive Tracers
PubMed: 32540030
DOI: 10.1053/j.semnuclmed.2020.03.001 -
Optics Letters Jan 2023A photoelectrochemical (PEC) cell produces hydrogen energy using solar energy and an electrochemical reaction. In the hydrogen production process with water...
A photoelectrochemical (PEC) cell produces hydrogen energy using solar energy and an electrochemical reaction. In the hydrogen production process with water decomposition, electrons move from the anode to the cathode, and by measuring the current value at this time, the PEC cell can generate hydrogen and function as an image sensor at the same time. Due to the characteristics of the PEC cell that can perform both functions simultaneously, it can be applied as a device that can detect and respond to the surrounding environment without the need for an observation system such as a camera. We present the imaging performance of PEC cells. The effectiveness of the experiment was confirmed by applying the PEC cells to integral imaging, one of the three-dimensional (3D) imaging techniques.
Topics: Electrochemical Techniques; Imaging, Three-Dimensional; Solar Energy; Hydrogen
PubMed: 36638454
DOI: 10.1364/OL.476115 -
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 -
Medical Physics Mar 2024Glass Y microspheres are produced with known radionuclide impurities. These impurities are not independently monitored. Clinical instruments, including ionization... (Review)
Review
BACKGROUND
Glass Y microspheres are produced with known radionuclide impurities. These impurities are not independently monitored. Clinical instruments, including ionization chamber dose calibrators and positron emmission tomography (PET) cameras, can be much more sensitive in detecting signals from these impurities than to signals from Y itself.
PURPOSE
The "typical" levels of Y impurities have been studied to assess their impact on dosimetry during internal implantation, and for the management of waste. However, unaccounted-for decay spectra of impurities can also have an impact on dose calibrator and PET readings. Thus, even what might be considered negligibly small impurity fractions, can in principle cause substantial overestimates of the amount of Y activity present in a sample. To our knowledge, quantitative effects of radionuclide impurities in glass microspheres on activity measurements have not been documented in the field. As activity quantitation for dosimetry and its correlations with outcome becomes more prevalent, the effects of impurities on measurements may remain unaccounted for in dosimetry studies.
METHODS
In this letter, we review theoretical and physical considerations that will result in asymmetric errors in quantitation from Y impurities and estimate their typical and potential impact on clinical utilization. Among the common impurities Y is of particular concern for its impact on Y dose measurements because of its decay characteristics, along with other isotopes Y and Sc which can also impact measurements.
RESULTS
The typical level of Y impurities reported by the manufacturer should only cause small errors in dose calibrator and PET measurements made within the 12-day label-specified use-by period, up to 2.0% and 1.6%, respectively. However, the product specification max allowable impurity levels, specified by the manufacturer, leave open the potential for much greater bias from within the 12-day use-by period, potentially as high as 13.2% for dose calibrator measurements and 10.6% for PET from the Y impurities.
CONCLUSIONS
While typical levels of impurities appear to have acceptable impact on patient absorbed dose, it should be noted that they can have adverse effects on Y radioactivity measurements. Furthermore, there is currently minimal independent verification and/or monitoring of impurity levels within the field.
Topics: Humans; Microspheres; Yttrium Radioisotopes; Radiometry; Tomography, Emission-Computed; Glass; Liver Neoplasms; Embolization, Therapeutic
PubMed: 37956259
DOI: 10.1002/mp.16828 -
ACS Central Science Sep 2019Here we apply microcrystal electron diffraction (MicroED) to the structural determination of transition-metal complexes. We find that the simultaneous use of 300 keV...
Here we apply microcrystal electron diffraction (MicroED) to the structural determination of transition-metal complexes. We find that the simultaneous use of 300 keV electrons, very low electron doses, and an ultrasensitive camera allows for the collection of data without cryogenic cooling of the stage. This technique reveals the first crystal structures of the classic zirconocene hydride, colloquially known as "Schwartz's reagent", a novel Pd(II) complex not amenable to solution-state NMR or X-ray crystallography, and five other paramagnetic and diamagnetic transition-metal complexes.
PubMed: 31572777
DOI: 10.1021/acscentsci.9b00403 -
Microscopy Research and Technique Feb 2023The achievement of this work is that fine tuning of experimental and evaluation parameters can improve the absolute accuracy and reproducibility of selected area...
The achievement of this work is that fine tuning of experimental and evaluation parameters can improve the absolute accuracy and reproducibility of selected area electron diffraction (SAED) to 0.1% without using internal standard. Due to the proposed procedure it was possible to reach a reproducibility better than 0.03% for camera length between sessions by careful control of specimen height and illumination conditions by monitoring lens currents. We applied a calibration specimen composed of nanocrystalline grains free of texture and providing narrow diffraction rings. Refinements of the centre of the diffraction pattern and corrections for elliptic ring distortions allowed for determining the ring diameters with an accuracy of 0.1%. We analyze the effect of different error sources and reason the achieved absolute accuracy of the measurement. Application of the proposed evaluation procedure is inevitable in case of multicomponent nanocomposites or textured materials and/or having close diffraction rings where application of automated procedures is limited. The achieved accuracy of 0.1% without internal standard is approaching that of routine laboratory XRD, and reduction of instrumental broadening due to the elaborated evaluation procedure allows for separation of close reflections, provides more reliable ring width and thus improved input parameters for further nanostructure analysis as demonstrated on dental enamel bioapatite.
Topics: Electrons; Reproducibility of Results; Nanocomposites
PubMed: 36069159
DOI: 10.1002/jemt.24229 -
The British Journal of Radiology Jul 2022The Ionising Radiation (Medical Exposure) Regulations require employers to appoint suitable medical physics experts (MPE) for nuclear medicine services, and they also...
The Ionising Radiation (Medical Exposure) Regulations require employers to appoint suitable medical physics experts (MPE) for nuclear medicine services, and they also define the areas where MPEs are required to provide advice and specify matters that they must contribute towards. Applications for employer licences under IR(ME)R require employers to specify the level of MPE support available and if this is provided by onsite MPEs or remotely. Assessment of these applications by the Administration of Radioactive Substances Advisory Committee (ARSAC) has highlighted variability in the levels of MPE support being provided for similar services across the UK. A working party including representatives from IPEM, ARSAC, BIR and BNMS was formed and has produced these recommendations on MPE support. Nuclear medicine services were divided into seven broad categories and MPE support for each category has been considered. However, some services that differ from the scenarios provided in this guidance may require different levels of MPE support. Positron emission tomography (PET)/CT and gamma camera imaging have been considered separately here, although it is recognised that both PET/CT and gamma cameras are often sited within the same department in many centres. The separation has been done for pragmatic purposes, as there are felt to be sufficient differences in the MPE role requirements. This guidance sets out recommendations for MPE support, and broader physics support, to run a safe nuclear medicine service and defines the responsibilities of these staff for a range of clinical nuclear medicine services. The recommendations on MPE support made are advice, but will assist employers in meeting regulatory requirements.
Topics: Humans; Muscle Spasticity; Nuclear Medicine; Physics; Positron Emission Tomography Computed Tomography; Spinocerebellar Ataxias; Tomography, X-Ray Computed
PubMed: 35604659
DOI: 10.1259/bjr.20211393 -
Physics in Medicine and Biology Sep 2020Quality control tests of molecular imaging systems are hampered by the complexity of phantom preparation. It is proposed that radioisotopes can be directly incorporated...
Quality control tests of molecular imaging systems are hampered by the complexity of phantom preparation. It is proposed that radioisotopes can be directly incorporated into photo-polymer resins. Use of the radio-polymer in a 3D printer allows phantoms with more complex and reliable activity distributions to be produced whilst simplifying source preparation. Initial tests have been performed to determine the practicality of integrating Tc-99m into a photo-polymer and example phantoms produced to test suitability for quality control. Samples of build and support resins were extracted from the print cartridges of an Objet30Pro Polyjet 3D printer. The response of the resin to external factors including ionising radiation, light and dilution with Tc-99m pertechnetate were explored. After success of the initial tests the radio-polymer was used in the production of different phantoms. Radionuclide dose calibrator and gamma camera acquisitions of the phantoms were used to test accuracy of activity concentration, print consistency, uniformity and heterogeneous reproducibility. Tomographic phantoms were also produced including a uniform hot sphere, a complex configuration of spheres and interlacing torus's and a hot rod phantom. The coefficient of variation between repeat prints of a 12 g disk phantom was 0.08%. Measured activity within the disks agreed to within 98 ± 2% of the expected activity based on initial resin concentration. Gamma camera integral uniformity measured across a 3D printed flood field phantom was 5.2% compared to 6.0% measured with a commercial Co-57 flood source. Heterogeneous distributions of activity were successfully reproduced for both 2D and 3D imaging phantoms. Count concentration across regions of heterogeneity agreed with the planned activity assigned to those regions on the phantom design. 3D printing of radioactive phantoms has been successfully demonstrated and is a promising application for quality control of Positron Emission Tomography and Single Photon Emission Computed Tomography systems.
Topics: Calibration; Humans; Imaging, Three-Dimensional; Molecular Imaging; Phantoms, Imaging; Printing, Three-Dimensional; Reproducibility of Results; Technetium
PubMed: 32640429
DOI: 10.1088/1361-6560/aba40e