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Principles behind Magnetic Resonance Imaging (MRI)
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
The inherent motion sensitivity of the MRI signal has been known for a long time, and the disadvantages in terms of motion artefacts were described above. However, the extra phase shift caused by a displacement of the spins, in the presence of a magnetic field gradient, can also be used in a constructive way for quantitative measurements of flow – for example, in large blood vessels. In so-called phase maps, each pixel shows the phase angle, which is proportional to the velocity of the spins.
Dietetics and Nutrition in Oncology Patients: Evaluation of Nutritional Status, Weight Control, and Nutrigenomics
Published in Paloma Tejero, Hernán Pinto, Aesthetic Treatments for the Oncology Patient, 2020
Bioelectrical impedance (BIA) is an indirect method for measuring BC, based on the human body's ability to transmit electrical power. It obtains data on the body compartments and provides electrical values: impedance, resistance, reactance, and the phase angle (PA). The vectorial representation of PA has demonstrated its usefulness in identifying short-term body changes and serving as a specific marker of nutritional status. Absolute PA values are directly related to cell membrane health status and are an indicator of morbidity and mortality prognosis [34]. As weaknesses of this technique, we point out that PA is modified by the state of hydration (both dehydration and the presence of ascites and edema). In addition, it varies according to gender, age, BMI, and race, and we lack reference values for cancer population. The high interpatient variability requires careful interpretation of results, but it is a promising technique [35].
Methods of Rhythm Measurement
Published in Sue Binkley, Biological Clocks, 2020
A particular time point of a rhythm is a phase. The time difference between two phases is called the phase angle. When a rhythm is altered so that its peaks occur later in time, the phase of a rhythm is delayed; when a rhythm is altered so that its peaks occur early in time, the rhythm is advanced, a phase advance. The application of these ideas is clear in people. When we travel east across time zones (as when an American flies to Europe), we encounter earlier sunrises with respect to our time back home. Our internal rhythms must advance in order to synchronize with the new external time zone at our destination. When we journey westward (as when a European flied to America), a delay is required for our rhythms to synchronize, a phase delay. Advances and delays are called phase shifts.
A Low Body Fat Mass Ratio Predicts Poor Prognosis in Patients with Advanced Non-Small Cell Lung Cancer
Published in Nutrition and Cancer, 2022
Zeynep Oruc, Ahmet Akbay, M. Ali Kaplan, İdris Oruç, Zuhat Urakçı, Mehmet Küçüköner, Abdurrahman Işıkdoğan
BIA-derived formulas, such as the phase angle, were developed to identify body components rather than fat-free mass and related fat mass ratio; however, no ideal clinical biomarker has been defined yet (9,10). The phase angle (PA) is a ratio between the reactance and resistance obtained by BIA and has been interpreted as an indicator of altered tissue’s electrical properties and a predictor of total body cell mass (19). The BIA-derived PA was used in previous studies, which showed that the PA is a strong predictor of survival in many cancers, including lung, breast, colorectal and pancreatic cancer (20–23), and several other clinical conditions, such as HIV infection, liver cirrhosis, chronic obstructive pulmonary disease, hemodialysis and sepsis (15, 23). In many trials, a low phase angle has been shown to be associated with poor prognosis (9, 19, 24).
Effects of High-Dose Vitamin D Supplementation on Phase Angle and Physical Function in Patients with Prostate Cancer on ADT
Published in Nutrition and Cancer, 2021
Julia E. Inglis, Isabel D. Fernandez, Edwin van Wijngaarden, Eva Culakova, Jennifer E. Reschke, Amber S. Kleckner, Po-Ju Lin, Karen M. Mustian, Luke J. Peppone
In addition to physical function, preliminary impairments in cellular membrane function and fluid imbalance that eventually lead to functional decline can be detected before changes in body composition by bioelectrical impedance analysis (BIA) (24). Phase angle is a noninvasive technique measured from BIA to assess functionality and frailty (25–27). Phase angle may indicate nutrition and hydration status in various populations including diseases of aging, sarcopenia and cancer, and lower phase angle values signal the onset of functional decline (24, 27, 28). In patients with cancer, nutrition and hydration, as measured by phase angle, are indicators for overall well-being and are used in the decision process for treatment (27). Phase angle in patients with cancer serves as a predictor of poor health status and lower survival (27).
The decrease in phase angle measured by bioelectrical impedance analysis reflects the increased locomotive syndrome risk in community-dwelling people: The Yakumo study
Published in Modern Rheumatology, 2019
Satoshi Tanaka, Kei Ando, Kazuyoshi Kobayashi, Tetsuro Hida, Taisuke Seki, Takashi Hamada, Kenyu Ito, Mikito Tsushima, Masayoshi Morozumi, Masaaki Machino, Kyotaro Ota, Naoki Ishiguro, Yukiharu Hasegawa, Shiro Imagama
Phase angle measured by BIA expresses both the amount and quality of soft tissue. Thus, it has been suggested as an indicator of cellular health [26,27], with high values reflecting high cellularity and cell membrane integrity and better cell function. In healthy individuals, phase angle usually falls in the range 5–7°. A previous study reported that age and sex were involved in the determination of phase angle [28]. In brief, phase angle decreases with age due to a reduction in reactance, which is consistent with the loss of muscle mass and increase in resistance caused by a decline in the proportion of body water at the expense of an increase in fat mass in older age. Phase angle is higher in men than in women because of the higher body muscle mass of men. In fact, phase angle is correlated with various functional indicators [29], nutritional status, muscle weakness, sarcopenia [16,30], and osteoporosis [15]. Phase angle is frequently lower than normal in patients with certain diseases because infection, inflammation, or disease-specific parameters might reduce phase angle. A low phase angle is predictive of a more negative prognosis in pancreatic, colorectal, breast, and lung cancer patients and surgical patients [14].