Optimization of spiral MRI using a perceptual difference model.

We systematically evaluated a variety of MR spiral imaging acquisition and reconstruction schemes using a computational perceptual difference model (PDM) that models the ability of humans to perceive a visual difference between a degraded "fast" MRI image with subsampling of k-space and a "gold standard" image mimicking full acquisition. Human subject experiments performed using a modified double-stimulus continuous-quality scale (DSCQS) correlated well with PDM, over a variety of images. In a smaller set of conditions, PDM scores agreed very well with human detectability measurements of image quality.

Keyhole Dixon method for faster, perceptually equivalent fat suppression.

Purpose: To reduce the acquisition time associated with the two-point Dixon fat suppression technique by combining a keyhole in-phase (Water + Fat) k-space data set with a full out-of-phase (Water - Fat) k-space data set and optimizing the keyhole size with a perceptual difference model.

Materials And Methods: A set of keyhole Dixon images was created by varying the number of lines in the keyhole data set. Off-resonance correction was incorporated into the image reconstruction process to improve the homogeneity of the fat suppression.

X-ray computed tomography methods for in vivo evaluation of local drug release systems.

Recent advances in drug delivery techniques have necessitated the development of tools for in vivo monitoring of drug distributions. Gamma emission imaging and magnetic resonance imaging suffer from problems of resolution and sensitivity, respectively. We propose that the combination of X-ray CT imaging and image analysis techniques provides an excellent method for the evaluation of the transport of platinum-containing drugs from a localized, controlled release source.

Noninvasive monitoring of local drug release using X-ray computed tomography: optimization and in vitro/in vivo validation.

In vivo release profiles of drug-loaded biodegradable implants were noninvasively monitored and characterized using X-ray computed tomography (CT). The imaging method was adapted and optimized to quantitatively examine the release of an active agent from a model cylindrical PLGA device (the millirod) into rabbit livers over 48 h. Iohexol, a CT contrast agent, served as a model drug; optimization of CT acquisition parameters yielded a sensitivity of 0.

Noninvasive monitoring of local drug release in a rabbit radiofrequency (RF) ablation model using X-ray computed tomography.

In this study, X-ray computed tomography (CT) was utilized as a noninvasive method to directly examine local drug release kinetics in livers before and following radiofrequency thermal ablation. Iohexol, a CT contrast agent, was used as a drug-mimicking molecule. Release of iohexol in healthy and ablated rabbit livers over 48 h was quantified and correlated with the release profiles from phosphate-buffered saline (PBS) in vitro.