Greta S. P. Mok

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OBJECTIVE In this retrospective non-randomized cohort study, the image quality and radiation dose were compared between prospectively electrocardiogram (ECG)-gated axial (PGA) and retrospectively ECG-gated helical (RGH) techniques for the assessment of coronary artery bypass grafts using 256-slice CT. METHODS We studied 124 grafts with 577 segments in 64(More)
We aim to study the effects of activity distribution for multiplexing multi-pinhole (MPH) SPECT. Three digital phantoms, including a hot rod, a cold rod and a cold sphere phantom, were used. Different degrees of multiplexing were obtained by (i) adjusting the MPH pattern for the same 4-pinhole collimator (scheme 1) and (ii) increasing the number of pinholes(More)
BACKGROUND Digital subtraction angiography (DSA) provides detailed hemodynamic information. However, the imaging interpretation is mainly based on the physician's experience and observation. We aimed to quantitatively study the peritherapeutic blood flow changes of a cerebral arteriovenous malformation (AVM) treated by embolization using optical flow(More)
Our goal was to evaluate a multi-pinhole (MPH) collimator which allows changing configurations for mouse imaging and rat imaging. The collimator length can be adjusted from 5 cm for rat imaging to a maximum of 8 cm for mouse imaging. Projections of mouse- and rat-size phantoms were simulated with collimator length of 8 cm, and the rat-size phantom was(More)
Previously, we proposed using an interpolated average CT (IACT) method for attenuation correction (AC) in positron emission tomography (PET), which is a good, low-dose approximation of cine average CT (CACT) to reduce misalignments and improve quantification in PET/CT. This study aims to evaluate the performance of IACT for different motion amplitudes. We(More)
OBJECTIVE To report our clinical experience with a 256-slice multidetector computed tomography (MDCT) with a 270-ms gantry rotation system in performing CT coronary angiograms (CTCA) using both prospectively gated step and shoot (PGSS) and retrospectively gated helical (RGH) techniques. MATERIALS AND METHODS We studied 252 patients who received CTCA; 126(More)
BACKGROUND The aims of this study were to investigate the image quality and radiation exposure of pediatric protocols for cardiac CT angiography (CTA) in infants under one year of age. METHODOLOGY/PRINCIPAL FINDINGS Cardiac CTA examinations were performed using an anthropomorphic phantom representing a 1-year-old child scanned with(More)
The aim of this study was to explore the feasibility and repeatability of amide proton transfer-weighted (APTw) MRI for the head and neck on clinical MRI scanners. Six healthy volunteers and four patients with head and neck tumors underwent APTw MRI scanning at 3 T. The APTw signal was quantified by the asymmetric magnetization transfer ratio (MTRasym) at(More)
The aim of this study was to evaluate whether technetium 99m hydrazinonicotinamide (99mTc-HYNIC)-annexin V single-photon emission computed tomography (SPECT) would detect dose-dependent doxorubicin (DOX)-mediated cell death in the heart compared with functional echocardiography. Adult female Sprague-Dawley rats were treated with DOX (cumulative dose of 15(More)
Our goal is to study the trade-off between image degradation and improved detection efficiency and resolution from allowing multiplexing in multi-pinhole (MPH) SPECT, and to determine the optimal pinhole number for MPH design. We used an analytical 3D MPH projector and two digitized phantoms: the mouse whole body (MOBY) phantom and a hot sphere phantom to(More)