Browsing by Author "Samei, E"

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    Adaptability index: quantifying CT tube current modulation performance from dose and quality informatics
    (2017-03-17) Ria, F; Wilson, JM; Zhang, Y; Samei, E
    The balance between risk and benefit in modern CT scanners is governed by the automatic adaptation mechanisms that adjust x-ray flux for accommodating patient size to achieve certain image noise values. The effectiveness of this adaptation is an important aspect of CT performance and should ideally be characterized in the context of real patient cases. Objective of this study was to characterize CT performance with an index that includes image-noise and radiation dose across a clinical patient population. The study included 1526 examinations performed by three scanners, from two vendors, used for two clinical protocols (abdominopelvic and chest). The dose-patient size and noise-patient size dependencies were linearized, and a 3D-fit was performed for each protocol and each scanner with a planar function. In the fit residual plots the Root Mean Square Error (RMSE) values were estimated as a metric of CT adaptability across the patient population. The RMSE values were between 0.0344 HU1/2 and 0.0215 HU1/2: different scanners offer varying degrees of reproducibility of noise and dose across the population. This analysis could be performed with phantoms, but phantom data would only provide information concerning specific exposure parameters for a scan: instead, a general population comparison is a way to obtain new information related to the relevant clinical adaptability of scanner models. A theoretical relationship between image noise, CTDIvol and patient size was determined based on real patient data. This relationship may provide a new index related to the scanners' adaptability concerning image quality and radiation dose across a patient population. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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    Awareness of medical radiation exposure among patients: A patient survey as a first step for effective communication of ionizing radiation risks
    (Physica Medica, 2017-11) Ria, F; Bergantin, A; Vai, A; Bonfanti, P; Martinotti, AS; Redaelli, I; Invernizzi, M; Pedrinelli, G; Bernini, G; Papa, S; Samei, E
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    Cell and extracellular matrix growth theory and its implications for tumorigenesis.
    (Bio Systems, 2021-03) Sauer, TJ; Samei, E; Bejan, A
    Cells associated with an abnormal (cancerous) growth exchange flows, morph freely and grow hand-in-glove with their immediate environment, the extracellular matrix (ECM). The cell structure experiences two mass flows in counterflow. Flowing into the structure are nutrients and flowing out is refuse from the metabolically active biomass within. The physical effect of the evolution of the cell and extracellular structure is more flow and mixing in that space, that is, more mixing than in the absence of a biological growth in that space. The objective of the present theory is to predict the increase in the size of the cell cluster as a function of its structure, and also to predict the critical cluster sizes that mark the transitions from one distinct cluster configuration to the next. This amounts to predicting the timing and the main features of the transitions from single cell to clusters with two, four, eight and more cells, including larger clusters with cells organized on its outer surface. The predicted evolution of the size and configuration of the cell cluster is validated successfully by comparison with measurements from several independent studies of cancerous and non-cancerous growth patterns.
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    Comparing two different noise magnitude estimation methods in CT using virtual imaging trials
    (Medical Imaging 2022: Physics of Medical Imaging, 2022-04-04) Ria, F; Jadick, GL; Abadi, E; Solomon, JB; Samei, E