China
Africa
Explore chapters and articles related to this topic
Clinical Considerations
Published in Stephen W. Carmichael, Susan L. Stoddard, The Adrenal Medulla 1986 - 1988, 2017
Stephen W. Carmichael, Susan L. Stoddard
Paling, Brookeman and Mugler (1987) evaluated the potential of phase-contrast imaging, also called “proton chemical shift imaging” or “proton spectroscopy,” in detecting and displaying tumors located outside of the liver. Specifically, they assessed the ability of this technique to render such tumors more conspicuous, both visually and quantitatively, than may be possible with standard MRI. In all cases, tumors were most conspicuous with the phase-contrast technique and even tumors that could not be visualized by standard MRI could be visualized with this technique. Among other tumors, they demonstrated that pheochromocytoma could be well visualized. They recommended phase-contrast imaging as an adjunct to standard MRI sequences when evaluating for either the presence or extent of a tumor.
Use of radiochromic film with synchrotron radiation
Published in Indra J. Das, Radiochromic Film, 2017
Tomas Kron, Elizabeth Kyriakou, Jeffrey C. Crosbie
Only a minority (less than 10) of synchrotron facilities have dedicated beamlines for medical applications; however, this number is growing quickly as many applications have been identified ranging from diagnostic imaging to radiotherapy applications. For diagnostic applications, k-edge subtraction imaging has been one of the first applications used on human subjects [4]. High contrast images are acquired using a contrast medium with high atomic number and delivering radiation just above and just below the k-edge. A subtraction of the two images demonstrates the location of the contrast agent with exquisite spatial and contrast resolution. Of particular, interest for diagnostic imaging is also phase contrast imaging that utilizes the special properties of coherence and monochromatism to generate images that would not be possible with other modalities [5]. Figure 19.3 shows an example for a phase contrast image of the lung of a rabbit pup acquired at the SPRING 8 synchrotron in Japan.
X-ray Vision: Diagnostic X-rays and CT Scans
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
To understand the physical meaning of the parameter δ, we can use the following relation between the wavelength of light in matter and the index of refraction, which is also valid for x-rays: where λ0 is the wavelength in vacuum. Since δ is positive, the wavelength of x-rays in tissues is larger than their wavelength in vacuum. This means that the distance between the neighboring wave crests and troughs increases as the wave travels through matter. (Recall that the crests and troughs in the electromagnetic wave correspond to the amplitude of the wave, and the intensity is proportional to the square of the amplitude.) As a result, the crests and troughs in the wave transmitted through a thin slice of tissue shift relative to the incident wave as illustrated in Figure 5.36. It turns out that this shift can be quantified by measuring the difference in phase or phase shift of the transmitted wave relative to the incident wave. The phase determines the timing of oscillations of different points in the wave. For example, two points separated by the distance of one wavelength reach the crests and troughs simultaneously. These two points oscillate in-step or in-phase – the phase difference is zero. On the other hand, the points separated by a half of a wavelength are out-of-phase – when one of the points is on the crest, the other is in the trough – and the phase difference is π (the phase is measured in radians). It turns out that the phase shift of the x-ray transmitted through a thin slice of tissue is: where d is thickness of the thin slice, and δ is the phase shift parameter describing the deviation from unity of the index of refraction (Equation 5.18). In the phase contrast imaging method, the goal is to detect the phase shift of the transmitted x-ray and create an image using the variation of the values of δ between different soft tissues.
Accuracy of radiological prediction of electrode position with otological planning software and implications of high-resolution imaging
Published in Cochlear Implants International, 2023
Franz-Tassilo Müller-Graff, Johannes Voelker, Anja Kurz, Rudolf Hagen, Tilmann Neun, Kristen Rak
In order to obtain the most precise measurements of the cochlear shape, adequate preoperative radiological diagnostics are necessary. In recent years, various imaging technologies and formulas have been developed to address this issue (Schurzig et al., 2021). In particular, multislice computed tomography (MSCT) (Escude et al., 2006; Vu et al., 2019) or cone-beam CT (CBCT) (Wurfel et al., 2014) were used most frequently to determine the cochlear anatomy. The technique of MSCT scanners is based on multislice-detectors, which have to focus multiple times on the region of interest, while moving forward continuously in the z-axis. From these measurements, anisotropic voxels are allocated. Due to its broad clinical and routine availability, this type of imaging has become established for temporal bone purposes. However, in comparison to more precise imaging, like micro-CT (Schurzig et al., 2018; van den Boogert et al., 2018) or synchrotron radiation phase-contrast imaging (Helpard et al., 2020; Helpard et al., 2021; Koch et al., 2017) as a reference method, several disadvantages for otological use have become obvious. For example, partial volume effects and strong imaging noises prevent more accurate measurements of the cochlea duct length (CDL) (Lexow et al., 2016).
Precise evaluation of the postoperative cochlear duct length by flat-panel volume computed tomography – Application of secondary reconstructions
Published in Cochlear Implants International, 2022
Philipp Schendzielorz, Lukas Ilgen, Franz-Tassilo Müller-Graff, Laurent Noyalet, Johannes Völker, Johannes Taeger, Rudolf Hagen, Tilmann Neun, Simon Zabler, Daniel Althoff, Kristen Rak
In one study, 3D-curved MPR was used in combination with preoperative cone beam computed tomography in a clinical setting and revealed a CDL of 37.6 mm (range: 32.0–43.5 mm, standard deviation [SD]: 1.9 mm, N = 436) (Würfel et al., 2014). In a similarly constructed study, a CDL of 35.8 mm (range: 30.7–42.2 mm, SD: 2.0 mm, N = 310) was determined by means of MSCT and 3D-curved MPR preoperatively (Meng et al., 2016). The latest experimental studies using high-resolution imaging like synchrotron radiation phase-contrast imaging (39.0 mm, range: 33.6–41.7 mm, SD: 2.1 mm, N = 16) (Koch, Elfarnawany, et al., 2017) or micro-CT (42.3 mm, range: 39.3–46.1 mm, SD: 2.4 mm, N = 9) (Wuerfel et al., 2015) postulate, that there is a potentially significant underestimation of the CDL in clinical used scanning techniques, probably due to their limited image resolution.
Impact of copper oxide particle dissolution on lung epithelial cell toxicity: response characterization using global transcriptional analysis
Published in Nanotoxicology, 2021
Andrey Boyadzhiev, Mary-Luyza Avramescu, Dongmei Wu, Andrew Williams, Pat Rasmussen, Sabina Halappanavar
The LDH enzymatic method of cytotoxicity assessment resulted in pronounced interference with CuO NPs (Supplementary Figure S3) at higher doses. Cytotoxicity was not observed for any doses at 2–24h post-exposure; however, a dose-dependent quenching of absorbance associated with the two highest doses (50 and 100µg/mL) was observed at all time points. At 48h, subtle dose-dependent cytotoxicity was observed at the lower doses of 5–10µg/mL CuO NPs. The two highest doses (50 and 100µg/mL CuO NPs) showed complete quenching of absorbance at 48h. Phase-contrast imaging showed no adherent cells at the two highest doses of 50 and 100µg/mL at 48h (data not shown). Thus, for the purposes of subsequent experiments, 1–25µg/mL concentrations of CuO NPs were used and the cytotoxicity assessment method was changed to cell viability assessment by Trypan Blue dye exclusion staining.