Recent technologies, such as nanotechnology, provide new opportunities for next generation scintillation devices and instruments. New nanophosphor-based materials seem to be promising for further improvements in optical diffusion studies. In medical imaging, detector technology has found widespread use, offering improved signal capabilities. However, in spite of many spectacular innovations and the significant research in chemical synthesis on the detective material, improvement in signal quality is still an issue requiring further progress. Here, a sophisticated analysis is shown within the framework of Mie scattering theory and Monte Carlo simulation which demonstrates the optimum structural and optical properties of nanophosphors that are significantly promising in manufacture for further signal modulation improvement. A variety of structural and optical properties were examined: (1) phosphors of grain size (1 to 1000 nm), (2) packing density (50% to 99%), (3) light wavelength (400 to 700 nm), and (4) refractive index of nanophosphor (real part: 1.4–2.0, imaginary part: $10−6$). Results showed that for a specific thickness of nanophosphor layer, the compromise between spatial resolution and sensitivity can be achieved by optimizing the structural ($200nm≤graindiameter≤800nm$) and optical properties of the nanophosphor ($1.7≤refractiveindex≤2.0$). Finally, high optical modulation was accomplished employing grains of high refractive index and size above 200 nm.

Medical imaging instrumentation is mostly based on the use of luminescent materials coupled to optical sensors. These materials are employed in the form of granular screens, structured crystals, single transparent crystals, ceramics, etc. Storage phosphors are also incorporated in particular X-ray imaging systems. The physical properties of these materials should match the criteria required by the detective systems employed in morphological and functional biomedical imaging. The systems are analyzed based on theoretical frameworks emanating from the linear cascaded systems theory as well as the signal detection theory. Optical diffusion has been studied by different methodological approaches, such as experimental measurements and analytical modeling, including geometrical optics and Monte Carlo simulation. Analysis of detector imaging performance is based on image quality metrics, such as the luminescence emission efficiency (LE), the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE). Scintillators and phosphors may present total energy conversion on the order of 0.001–0.013 with corresponding DQE in the range of 0.1–0.6. Thus, the signal-to-noise ratio, which is crucial for medical diagnosis, shows clearly higher values than those of the energy conversion.

Medical imaging instrumentation design and construction is based on radiation sources and radiation detectors/sensors. This review focuses on the detectors and sensors of medical imaging systems. These systems are subdivided into various categories depending on their structure, the type of radiation they capture, how the radiation is measured, how the images are formed, and the medical goals they serve. Related to medical goals, detectors fall into two major areas: (i) anatomical imaging, which mainly concerns the techniques of diagnostic radiology, and (ii) functional-molecular imaging, which mainly concerns nuclear medicine. An important parameter in the evaluation of the detectors is the combination of the quality of the diagnostic result they offer and the burden of the patient with radiation dose. The latter has to be minimized; thus, the input signal (radiation photon flux) must be kept at low levels. For this reason, the detective quantum efficiency (DQE), expressing signal-to-noise ratio transfer through an imaging system, is of primary importance. In diagnostic radiology, image quality is better than in nuclear medicine; however, in most cases, the dose is higher. On the other hand, nuclear medicine focuses on the detection of functional findings and not on the accurate spatial determination of anatomical data. Detectors are integrated into projection or tomographic imaging systems and are based on the use of scintillators with optical sensors, photoconductors, or semiconductors. Analysis and modeling of such systems can be performed employing theoretical models developed in the framework of cascaded linear systems analysis (LCSA), as well as within the signal detection theory (SDT) and information theory.