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Mr contrast agents radiology5/29/2023 ![]() In the simulations, the amount of separation was observed to be proportional to the concentration of the contrast agents however, this was not observed in the physical experiments due to limitations of the real detector system. Results: In both the simulations and the physical experiments, the contrast agents were easily separable from other soft-tissue-like and bone-like materials, thanks to the availability of the attenuation coefficient measurements at more than two energies provided by the energy resolved photon-counting detector. In this case, the linear attenuation coefficients at the lower kVp were plotted against those at the higher kVp. For comparison, a dual-kVp CT was also simulated using the same phantom materials. The linear attenuation coefficients were reconstructed for each material in each energy window and were visualized as scatter plots between pairs of energy windows. We imaged mouse-sized cylindrical phantoms filled with several soft-tissue-like and bone-like materials and with iodine-based and gadolinium-based contrast agents. Methods: To demonstrate this capability, we performed simulations and physical experiments using a six-threshold energy resolved photon-counting detector. This separation is enabled via the use of recently developed energy resolved photon-counting detectors with multiple thresholds, which allow simultaneous measurements of the x-ray attenuation at multiple energies. Specifically, this applies to the case when contrast agents that contain K-absorption edges in the energy range of interest are present in the object. ![]() ![]() Purpose: The objective of the study was to demonstrate that, in x-ray computed tomography (CT), more than two types of materials can be effectively separated with the use of an energy resolved photon-counting detector and classification methodology. This work, we feel, represents an important step toward the fabrication of a working MRSMM system. Simultaneous MR and SMM images of a breast phantom were also acquired using the integrated MRSMM system. The electromagnetic field, specific absorption ratio and RF coil parameters with cadmium-zinc-telluride detectors encapsulated in specialized RF and gamma-ray shielding mounted within the RF coil were investigated through simulation and experimental measurements. In this study, we developed and tested a unilateral breast array coil specialized for MRSMM imaging. Development of such a dual-modality system requires the integration of a radio frequency (RF) coil and radiation detector in a strong magnetic field without significant mutual interference. The synergistic combination of MRI and SMM (MRSMM) could result in both high sensitivity from MRI and high specificity from SMM. Scintimammography (SMM) could potentially supplement MRI to improve the diagnostic specificity. Despite its high sensitivity, the variable specificity of magnetic resonance imaging (MRI) in breast cancer diagnosis can lead to unnecessary biopsies and over-treatment. Overall, our results demonstrate that accurate, simultaneous SPECT and MRI data acquisition is feasible, justifying the further development of MRSPECT for either small-animal imaging or whole-body human systems by using appropriate components. Various techniques were proposed to compensate for these adverse effects. The presence of a magnetic field generated a position shift and resolution loss in the nuclear projection data. The metallic components of the SPECT hardware altered the B 0 field and generated a non-uniform reduction in the signal-to-noise ratio (SNR) of the MR images. Various phantom experiments characterized the interaction between the SPECT and MRI hardware components. For our MRSPECT system, a cadmium-zinc-telluride (CZT) nuclear radiation detector was interfaced with a specialized radiofrequency (RF) coil and placed within a whole-body 4 T MRI system. ![]() In this study, we developed a miniaturized dual-modality SPECT/MRI (MRSPECT) system and demonstrated the feasibility of simultaneous SPECT and MRI data acquisition, with the possibility of whole-body MRSPECT systems through suitable scaling of components. In medical imaging, single-photon emission computed tomography (SPECT) can provide specific functional information while magnetic resonance imaging (MRI) can provide high spatial resolution anatomical information as well as complementary functional information. ![]()
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