Heather T. Ma

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Blood pressure is one important risk factor for stroke prognosis. Therefore, continuous monitoring of blood pressure is crucial for preventing and predicting stroke. However, current blood pressure devices are mainly air-cuff based, which only can provide measurements intermittently. This study proposed a new blood pressure estimation method based on the(More)
The precision of parameter estimation for Intravoxel Incoherent Motion Diffusion Weighted Imaging (IVIM-DWI) was investigated by examining their Cramér-Rao bounds (CRBs) under the presence of Rician noise. Monte Carlo (MC) simulation was also conducted to validate the CRB results. The estimation uncertainties of true diffusion coefficient (D) and perfusion(More)
PURPOSE To study the relationship between hip bone mineral density (BMD), lumbar disc degeneration, and lumbar disc space narrowing in elderly subjects. MATERIALS AND METHODS The study cohort comprised 196 females and 163 males (age range, 67-89 years) with no age difference between the two groups. Anteroposterior total hip areal BMD was measured with DXA(More)
Bone marrow was assumed to be negligible on the aspect of bone mechanical behavior, where bone mass and bone mineral density were most studied. As a result, if the bone marrow, especially the marrow fat, plays a role in the bone mechanical properties is unknown yet. Marrow fat content was found increased in osteoporotic bone. However, the relationship(More)
A reduced bone perfusion has been found for osteoporotic subjects in previous studies. However, the physiological changes underlying the varied perfusion function is not well known yet. Tofts model is one of the most frequently used pharmacokinetic models in analyzing perfusion process. This study modified the Tofts model by replacing the arterial input(More)
PURPOSE To investigate whether compressed air during air-cuff inflation in vascular reactivity studies could induce aberrant blood oxygenation level-dependent (BOLD) signal change. MATERIALS AND METHODS Magnetic resonance imaging (MRI) experiments were performed on a whole-body 3 T scanner. The pattern of T2* signal change measured from a phantom(More)
PURPOSE To investigate the differences in proximal femoral bone marrow blood perfusion indices between hypertensive and normotensive rats using perfusion magnetic resonance imaging (MRI). MATERIALS AND METHODS Six-month-old male spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) were used (12 of each). Dynamic contrast-enhanced MRI of the(More)
This study investigated bone marrow perfusion at proximal femur varying with bone mineral density (BMD) and aging over 4 years. Dynamic contrast enhanced MRI data was extracted pixel-by-pixel and classified into 3 patterns to indicate the perfusion function. Eighty-seven elderly females were involved. A notable reduced perfusion as a whole was observed in(More)
QRS complex detecting algorithm is core of ECG auto-diagnosis method and deeply influences cardiac cycle division for signal compression. However, ECG signals collected by noninvasive surface electrodes areusually mixed with several kinds of interference, and its waveform variation is the main reason for the hard realization of ECG processing. This paper(More)
The objective of this study is to characterize perfusion and bone mineral density (BMD) in the lumbar spine as a function of level and anatomic location. Fourteen male subjects with healthy vertebral endplates were selected to avoid gender and endplate disease influence. The bone perfusion and BMD of different vertebral level (L1-L4) were measured by the(More)