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Dose reconstruction from PET images in carbon ion therapy: a deconvolution approach
摘要： Dose and range verification have become important tools to bring carbon ion therapy to a higher level of confidence in clinical applications. Positron emission tomography is among the most commonly used approaches for this purpose and relies on the creation of positron emitting nuclei in nuclear interactions of the primary ions with tissue. Predictions of these positron emitter distributions are usually obtained from time-consuming Monte Carlo simulations or measurements from previous treatment fractions, and their comparison to the current, measured image allows for treatment verification. Still, a direct comparison of planned and delivered dose would be highly desirable, since the dose is the quantity of interest in radiation therapy and its confirmation improves quality assurance in carbon ion therapy. In this work, we present a deconvolution approach to predict dose distributions from PET images in carbon ion therapy. Under the assumption that the one-dimensional PET distribution is described by a convolution of the depth dose distribution and a filter kernel, an evolutionary algorithm is introduced to perform the reverse step and predict the depth dose distribution from a measured PET distribution. Filter kernels are obtained from either a library or are created for any given situation on-the-fly, using predictions of the β+-decay and depth dose distributions, and the very same evolutionary algorithm. The applicability of this approach is demonstrated for monoenergetic and polyenergetic carbon ion irradiation of homogeneous and heterogeneous solid phantoms as well as a patient computed tomography image, using Monte Carlo simulated distributions and measured in-beam PET data. Carbon ion ranges are predicted within less than 0.5 mm and 1 mm deviation for simulated and measured distributions, respectively.
关键词： evolutionary algorithm,PET imaging,range verification,carbon ion therapy,dose reconstruction
更新于2025-09-04 15:30:14
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Study of Sensitivity and Resolution for Full Ring PET Prototypes based on Continuous Crystals and analytical modeling of the light distribution
摘要： Sensitivity and spatial resolution are the main parameters to maximize in the performance of a PET scanner. For this purpose, detectors consisting of a combination of continuous crystals optically coupled to segmented photodetectors have been employed. With the use of continuous crystals the sensitivity is increased with respect to the pixelated crystals. In addition, spatial resolution is no longer limited to the crystal size. The main drawback is the difficulty in determining the interaction position. In this work, we present the characterization of the performance of a full ring based on cuboid continuous crystals coupled to SiPMs. To this end, we have employed the simulations developed in a previous work for our experimental detector head. Sensitivity could be further enhanced by using tapered crystals. This enhancement is obtained by increasing the solid angle coverage, reducing the wedge-shaped gaps between contiguous detectors. The performance of the scanners based on both crystal geometries was characterized following NEMA NU 4-2008 standardized protocol in order to compare them. An average sensitivity gain over the entire axial field of view of 13.63% has been obtained with tapered geometry while similar performance of the spatial resolution has been proven with both scanners. The activity at which NECR and True peak occur is smaller and the peak value is greater for tapered crystals than for cuboid crystals. Moreover, a higher degree of homogeneity was obtained in the sensitivity map due to the tighter packing of the crystals, which reduces the gaps and results in a better recovery of homogeneous regions than for the cuboid configuration. Some of the results obtained, such as spatial resolution, depend on the interaction position estimation and may vary if other method is employed.
关键词： NEMA NU 4-2008,Monte Carlo simulations,image reconstruction,continuous crystals,depth of interaction,positron emission tomography (PET)
更新于2025-09-04 15:30:14
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F-18 Fluoride Positron Emission Tomography-Computed Tomography for Detecting Atherosclerotic Plaques
摘要： A large number of major cardiovascular events occur in patients due to minimal or some lumen narrowing of the coronary artery. Recent biological studies have shown that the biological composition or vulnerability of the plaque is more critical for plaque rupture compared to the degree of stenosis. To overcome the limitations of anatomical images, molecular imaging techniques have been suggested as promising imaging tools in various fields. F-18 fluorodeoxyglucose (FDG), which is widely used in the field of oncology, is an example of molecular probes used in atherosclerotic plaque evaluation. FDG is a marker of plaque macrophage glucose utilization and inflammation, which is a prominent characteristic of vulnerable plaque. Recently, F-18 fluoride has been used to visualize vulnerable plaque in clinical studies. F-18 fluoride accumulates in regions of active microcalcification, which is normally observed during the early stages of plaque formation. More studies are warranted on the accumulation of F-18 fluoride and plaque formation/vulnerability; however, due to high specific accumulation, low background activity, and easy accessibility, F-18 fluoride is emerging as a promising non-invasive imaging probe to detect vulnerable plaque.
关键词： PET,Atherosclerosis,Vulnerable plaque,Fluoride
更新于2025-09-04 15:30:14
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Guiding the Design of Organic Photocatalyst for PET-RAFT Polymerization: Halogenated Xanthene Dyes
摘要： By examining structurally similar halogenated xanthene dyes, this study establishes a guiding principle for resolving structure?property?performance relationships in the photocontrolled PET-RAFT polymerization system (PET-RAFT: photoinduced electron/energy transfer?reversible addition?fragmentation chain transfer). We investigated the effect of the halogen substituents on the photophysical and electrochemical properties of the xanthene dyes acting as photocatalysts and their resultant effect on the performance of PET-RAFT polymerization. Consideration of the structure?property?performance relationships allowed design of a new xanthene photocatalyst, where its photocatalytic activity (oxygen tolerance and polymerization rate) was successfully optimized for PET-RAFT polymerization. We expect that this study will serve as a theoretical framework in broadly guiding the design of high performance photocatalysts for organic photocatalysis.
关键词： PET-RAFT polymerization,structure?property?performance relationships,oxygen tolerance,photocatalysts,halogenated xanthene dyes
更新于2025-09-04 15:30:14
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Comparison of noise equivalent count rates (NECRs) for the PET systems with different ring diameter and electronics
摘要： Because the sensitivity of PET system increases in proportion to the inverse of the diameter of the detector ring, brain PET systems are being planned and developed. However, count losses due to the dead-time of the detector blocks increases as the ring diameter decreases. Since the count losses decrease the noise equivalent count rate (NECR) of the system, the NECR of brain PET system may be lower than that of a whole-body PET system in clinical dose range. In this paper, we compared the NECRs of brain PET systems with that of a whole-body PET system using a Monte Carlo simulation. We simulated the PET system for a 27-cm-diameter detector ring, a 54-cm-diameter detector ring and an 89-cm-diameter detector ring and evaluated the NECRs. In the clinical dose range, the NECR of the small-diameter brain PET system was lower than those of the whole-body PET system unless the electronics was advanced. We conclude that the small-diameter brain PET system with conventional electronics has not so much advantage except for the lower cost and the higher spatial resolution. However, advanced electronics can reduce degradation of NECR, so the small-diameter brain PET system with advanced electronics will be useful for clinical studies.
关键词： PET,LGSO,brain,NECR,count loss
更新于2025-09-04 15:30:14
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Changes in cerebral oxygenation and cerebral blood flow during hemodialysis – A simultaneous near-infrared spectroscopy and positron emission tomography study
摘要： Near-infrared spectroscopy (NIRS) is used to monitor cerebral tissue oxygenation (rSO2) depending on cerebral blood flow (CBF), cerebral blood volume and blood oxygen content. We explored whether NIRS might be a more easy applicable proxy to [15O]H2O positron emission tomography (PET) for detecting CBF changes during hemodialysis. Furthermore, we compared potential determinants of rSO2 and CBF. In 12 patients aged (cid:2) 65 years, NIRS and PET were performed simultaneously: before (T1), early after start (T2), and at the end of hemodialysis (T3). Between T1 and T3, the relative change in frontal rSO2 (DrSO2) was (cid:3)8 (cid:4) 9% (P ? 0.001) and (cid:3)5 (cid:4) 11% (P ? 0.08), whereas the relative change in frontal gray matter CBF (DCBF) was (cid:3)11 (cid:4) 18% (P ? 0.009) and (cid:3)12 (cid:4) 16% (P ? 0.007) for the left and right hemisphere, respectively. DrSO2 and DCBF were weakly correlated for the left (r 0.31, P ? 0.4), and moderately correlated for the right (r 0.69, P ? 0.03) hemisphere. The Bland-Altman plot suggested underestimation of DCBF by NIRS. Divergent associations of pH, pCO2 and arterial oxygen content with rSO2 were found compared to corres- ponding associations with CBF. In conclusion, NIRS could be a proxy to PET to detect intradialytic CBF changes, although NIRS and PET capture different physiological parameters of the brain.
关键词： cerebral oximetry,hemodialysis,water-PET,Brain perfusion,NIRS
更新于2025-09-04 15:30:14
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Positron Emission Tomography (PET) Imaging of Prostate Cancer with a Gastrin Releasing Peptide Receptor Antagonist - from Mice to Men
摘要： Ex vivo studies have shown that the gastrin releasing peptide receptor (GRPr) is overexpressed on almost all primary prostate cancers, making it a promising target for prostate cancer imaging and targeted radiotherapy. Methods: Biodistribution, dosimetry and tumor uptake of the GRPr antagonist 64Cu-CB-TE2A-AR06 [(64Cu-4,11-bis(carboxymethyl)-1,4,8,11-tetraazabicyclo(6.6.2)hexadecane)-PEG4-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-LeuNH2] were studied by PET/CT in four patients with newly diagnosed prostate cancer (T1c-T2b, Gleason 6-7). Results: No adverse events were observed after injection of 64Cu-CB-TE2A-AR06. Three of four tumors were visualized with high contrast [tumor-to-prostate ratio > 4 at 4 hours (h) post injection (p.i.)], one small tumor (T1c, < 5% tumor on biopsy specimens) showed moderate contrast (tumor-to-prostate ratio at 4 h: 1.9). Radioactivity was cleared by the kidneys and only the pancreas demonstrated significant accumulation of radioactivity, which rapidly decreased over time. Conclusion: 64Cu-CB-TE2A-AR06 shows very favorable characteristics for imaging prostate cancer. Future studies evaluating 64Cu-CB-TE2A-AR06 PET/CT for prostate cancer detection, staging, active surveillance, and radiation treatment planning are necessary.
关键词： Gastrin releasing peptide receptor,bombesin,prostate cancer,PET/CT
更新于2025-09-04 15:30:14
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Novel luminescent paper based calix[4]arene chelation enhanced fluorescence- photoinduced electron transfer probe for Mn2+, Cr3+ and F-
摘要： A novel structurally simple calix[4]arene attached 1-aminoanthraquinone associated lower rim calix[4]arene conjugate was synthesized and has been used as turn on/off/on fluorescence probe for Mn2+, Cr3+ and F-. This chelation enhanced fluorescence - photoinduced electron transfer (CHEF-PET) based TAAC probe has been applied for its analytical application in real samples such as Mn2+ from blood serum, Cr3+ and F- from industrial effluent with 94 - 99 % recovery. The limit of detection of this sensor is found to be 11 nM for Mn2+, 4 nM for Cr3+ and 19 nM for F- with the concentration range of 0-120 nM. Further, we report an easy-to-use, low cost and disposable paper-based sensing device for rapid chemical screening of Mn2+, Cr3+ and F-. The device comprises fluorescent sensing probes embedded into a nitrocellulose matrix where the resonance energy transfer phenomenon seems to be the sensing mechanism. It opens up new opportunities for simple and fast screening in remote settings where sophisticated instrumentation is not always available. The MOPAC-2016 software package has been used to optimize the TAAC using PM7 well established method and calculates the HOMO-LUMO energy band gap for structure TAAC and TAAC with Mn2+, Cr3+ and F- ion based structures.
关键词： paper based analytical device,computational study,CHEF,PET,calix[4]arene
更新于2025-09-04 15:30:14
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The challenges and opportunities in functional imaging HER2 positive breast cancers
摘要： Breast cancer is the most common malignancy in women and 20‐30% of these cancers overexpress the HER2 protein making them candidates for HER2‐directed therapies. Trastuzumab (Herceptin?), the first HER2‐directed therapy, is a humanized monoclonal antibody that binds to the extracellular domain of HER2 preventing downstream signaling and cell proliferation. Trastuzumab is also an immunologic agent stimulating antibody‐dependent cytotoxicity. Investigators have developed radiolabeled trastuzumab as a PET imaging agent for use in HER2‐positive breast cancer patients. However, its clinical role has yet to be established. In the Journal, Dr. Woo and his colleagues report the use of NOTA as a chelator for 64Cu labeling of trastuzumab and claim more favorable pharmacokinetics than 64Cu DOTA trastuzumab [1]. But is NOTA a better chelator for 64Cu than DOTA? They base their comparison on a report by Paudyal et al. (Cancer Sci 2010; 101: 1045‐1050) in which the uptake of 64Cu‐DOTA‐trastuzumab in the liver was 26.9 ±7.4% ID/g at 24 hours[12], while in contrast, the uptake of 64Cu‐NOTA‐trastuzumab was 5.44 ±1.84%D/g in the liver at 24 hours (Figure 4)[1]. They conclude the difference in liver uptake between the two studies was due to release of 64Cu from the DOTA but not from the NOTA chelate. However, the two studies cannot be compared since they were not performed using the same tumor models. Paudyal et al. (Cancer Sci 2010; 101: 1045‐1050) performed PET imaging on Her2+ non‐small cell xenografts, while Woo et al. performed PET imaging on Her2+ breast cancer xenografts. The difference in liver uptake may simply reflect differential shedding of Her2 antigen to the liver between the two types of tumors. To make their point, Woo et al. should have compared DOTA vs NOTA conjugated trastuzumab in the same tumor model. This is a clear example of confusing the chemical stability of metal chelates with their metabolic clearance in different tumor models.
关键词： PET imaging,breast cancer,HER2,DOTA,trastuzumab,NOTA
更新于2025-09-04 15:30:14