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- 摘要
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PET Counting Response Variability Depending on Tumor Location, Activity, and Patient Obesity: A Feasibility Study of Solitary Pulmonary Nodule Using Monte Carlo
摘要： We aim to investigate the counting response variations of Positron Emission Tomography (PET) scanners with different detector configurations in the presence of Solitary Pulmonary Nodule (SPN). Using experimentally validated Monte Carlo simulations, the counting performance of four different scanner models with varying tumor activity, location, and patient obesity is represented using NECR (Noise Equivalent Count Rate). NECR is a well-established quantitative metric which has positive correlation with clinically perceived image quality. The combined effect of tumor displacement and increased activity shows a linear ascending trend for NECR with slope ranges of (12.5–18.2)*10-3 (kBq/cm3)-1 for three-ring (3R) scanners and (15.3–21.5)*10-3 (kBq/cm3)-1 for four-ring (4R). The trend for the combined effect of tumor displacement and patient obesity is exponential decay with 3R configurations weakly dependent on the patient obesity if the tumor is located at the center of the field-of-view with exponent’s range of (6.6-33.8)*10-2 cm-1. The dependency is stronger for 4R scanners (9.6–38.5)*10 -2 cm-1. The analysis indicates that quantitative PET data from the same SPN patient possibly examined in different time points (e.g. during staging or for the evaluation of treatment response) are affected by the different detector configurations and need to be normalized with patient weight, activity, and tumor location to reduce unwanted bias of the diagnosis. Our work provides also with a proof of concept for the ability of properly tuned simulations to provide additional insights into the counting response variability especially in tumor types where often borderline decisions have to be made regarding their characterization.
关键词： image quality assessment,nuclear imaging,lung
更新于2025-09-23 15:22:29
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Radiology, Lasers, Nanoparticles and Prosthetics || 6. Scintigraphy
摘要： In x-ray radiography and tomography the source of radiation (x-ray tube) is outside the body. Contrast on x-ray films or flat panel detectors is achieved by attenuation of the penetrating radiation in tissues of different density and thickness. In scintigraphy the source of radiation is inside the body. It is administered to the body by injecting radioactive isotopes into the blood circulation. The radioactive isotopes emit γ-radiation, which again is detected by x-ray films or by scintillation detectors. The difference between these two imaging modalities is highlighted in Fig. 6.1. Scintigraphy is not as general an imaging technique as x-ray radiography, the latter being used for inspection of healthy and diseased body parts alike. In contrast, scintigraphy is used for a number of specialized tests. Those include scans for tumor recognition, investigations of the metabolism of bones, of thyroid disorders, kidney clearance, lung ventilation, and of cardiac stress tests. These different scintigraphic applications will be presented in the following.
关键词： nuclear imaging,scintigraphy,radioisotopes,metabolism,γ-radiation
更新于2025-09-19 17:13:59
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Radiology, Lasers, Nanoparticles and Prosthetics || 7. Positron emission tomography
摘要： Positron emission tomography (PET) is a nuclear imaging modality used in clinics for cardiologic, neurologic, and oncologic studies. The PET method is based on the annihilation of positrons and electrons via converting their rest mass into two γ-photons flying in opposite directions. These two γ-photons are detected in a fashion similar to SPE or SPECT. Positron annihilation spectroscopy (PAS) is also used in condensed matter physics for determining the density and diffusivity of defects in solids. PAS is the opposite effect to pair production, which occurs when photons interact with nuclei at photon energies beyond 1 MeV. Pair production is important for cancer treatment with very hard x-rays, discussed in Chapter 9. However in this chapter we consider PET as an analytic tool.
关键词： nuclear imaging,PET,positron annihilation spectroscopy,γ-photons,Positron emission tomography,PAS
更新于2025-09-16 10:30:52
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Neutron Activated <sup>153</sup> Sm Sealed in Carbon Nanocapsules for <i>In Vivo</i> Imaging and Tumor Radiotherapy
摘要： Radiation therapy along with chemotherapy and surgery remain the main cancer treatments. Radiotherapy can be applied to patients externally (external beam radiotherapy) or internally (brachytherapy and radioisotope therapy). Previously, nanoencapsulation of radioactive crystals within carbon nanotubes, followed by end-closing, resulted in the formation of nanocapsules that allowed ultrasensitive imaging in healthy mice. Herein we report on the preparation of nanocapsules initially sealing ‘cold’ isotopically enriched samarium (152Sm), which can then be activated on demand to their ‘hot’ radioactive form (153Sm) by neutron irradiation. The use of ‘cold’ isotopes avoids the need for radioactive facilities during the preparation of the nanocapsules, reduces radiation exposure to personnel, prevents the generation of nuclear waste and evades the time constraints imposed by the decay of radionuclides. A very high specific radioactivity is achieved by neutron irradiation (up to 11.37 GBq/mg), making the ‘hot’ nanocapsules useful not only for in vivo imaging but also therapeutically effective against lung cancer metastases after intravenous injection. The high in vivo stability of the radioactive payload, selective toxicity to cancerous tissues and the elegant preparation method offer a paradigm for application of nanomaterials in radiotherapy.
关键词： nuclear imaging,filled carbon nanotubes,nanoencapsulation,nanooncology,radiooncology,cancer therapy
更新于2025-09-11 14:15:04
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An Advanced 100-Channel Readout System for Nuclear Imaging
摘要： Reading out from large-scale silicon photomultiplier (SiPM) arrays is a fundamental technical obstacle blocking the application of revolutionary SiPM technologies in nuclear imaging systems. Typically, it requires using dedicated application-specific integrated circuits (ASICs) that need a long iterative process, special expertise, and tools to develop. The pico-positron emission tomography (Pico-PET) electronics system is an advanced 100-channel readout system based on 1-bit sigma–delta modulation and a field-programmable gate array (FPGA). It is compact (6 × 6 × 0.8 cm3 in size), consumes little power (less than 3W), and is constructed with off-the-shelf low-cost components. In experimental studies, the Pico-PET system demonstrates excellent and consistent performance. In addition, it has some unique features that are essential for nuclear imaging systems, such as its ability to measure V–I curves, breakdown voltages, and the dark currents of 100 SiPMs accurately, simultaneously, and in real time. The flexibility afforded by FPGAs allows multiple-channel clustering and intelligent triggering for different detector designs. These highly sought-after features are not offered by any other ASICs and electronics systems developed for nuclear imaging. We conclude that the Pico-PET electronics system provides a practical solution to the long-standing bottleneck problem that has limited the development of potentially advanced nuclear imaging technology using SiPMs.
关键词： silicon photomultiplier (SiPM),readout electronics,Field-programmable gate array (FPGA),nuclear imaging,sigma–delta modulation
更新于2025-09-10 09:29:36
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A Higher-Order Polynomial Method for SPECT Reconstruction
摘要： Existing single-photon emission computed tomography (SPECT) reconstruction methods are mostly based on discrete models that may be viewed as piecewise constant approximations of a continuous data acquisition process. Due to low accuracy order of piecewise constant approximations, a traditional discrete model introduces irreducible model errors which are a bottleneck of the quality improvement of reconstructed images in clinical applications. To overcome this drawback, we develop a higher-order polynomial method for SPECT reconstruction. Specifically, we represent the data acquisition of SPECT imaging by using an integral equation model, approximate the solution of the underlying integral equation by higher-order piecewise polynomials leading to a new discrete system and introduce two novel regularizers for the system, by exploring the a priori knowledge of the radiotracer distribution, suitable for the approximation. The proposed higher-order polynomial method outperforms significantly the cutting edge reconstruction method based on a traditional discrete model in terms of model error reduction, noise suppression and artifact reduction. In particular, the coefficient of variation of images reconstructed by the piecewise linear polynomial method is reduced by a factor of 10 in comparison to that of a traditional discrete model-based method.
关键词： Image reconstruction,Nuclear imaging,Noise and artifact reduction
更新于2025-09-10 09:29:36