Triple-Modal Imaging of Magnetically-Targeted Nanocapsules in Solid Tumours In Vivo

Triple-modal imaging magnetic nanocapsules, encapsulating hydrophobic superparamagnetic iron oxide nanoparticles, are formulated and used to magnetically target solid tumours after intravenous administration in tumour-bearing mice. The engineered magnetic polymeric nanocapsules m-NCs are ~200 nm in size with negative Zeta potential and shown to be spherical in shape. The loading efficiency of superparamagnetic iron oxide nanoparticles in the m-NC was ~100%. Up to ~3- and ~2.2-fold increase in tumour uptake at 1 and 24 h was achieved, when a static magnetic field was applied to the tumour for 1 hour. m-NCs, with multiple imaging probes (e.g. indocyanine green, superparamagnetic iron oxide nanoparticles and indium-111), were capable of triple-modal imaging (fluorescence/magnetic resonance/nuclear imaging) in vivo. Using triple-modal imaging is to overcome the intrinsic limitations of single modality imaging and provides complementary information on the spatial distribution of the nanocarrier within the tumour. The significant findings of this study could open up new research perspectives in using novel magnetically-responsive nanomaterials in magnetic-drug targeting combined with multi-modal imaging

Flow and pressure measurement using phase-contrast MRI : experiments in stenotic phantom models.

Peripheral Arterial Disease (PAD) is a progressive atherosclerotic disorder which is defined as any pathologic process obstructing the blood flow of the arteries supplying the lower extremities. Moderate stenoses mayor may not be hemodynamically significant, and intravascular pressure measurements have been recommended to evaluate whether these lesions are clinically significant. Phase-contrast MRI (PC-MRI) provides a powerful and non-invasive method to acquire spatially registered blood velocity. The velocity field, then, can be used to derive other clinically useful hemodynamic parameters, such as blood flow and blood pressure gradients. Herein, a series of detailed experiments are reported for the validation of MR measurements of steady and pulsatile flows with stereoscopic particle image velocimetry (SPIV). Agreement between PC-MRI and SPIV was demonstrated for both steady and pulsatile flow measurements at the inlet by evaluating the linear regression between the two methods, which showed a correlation coefficient of\u3e 0.99 and\u3e 0.96 for steady and pulsatile flows, respectively. Experiments revealed that the most accurate measures of flow by PC-MRI are found at the throat of the stenosis (error \u3c 5% for both steady and pulsatile mean flows). The flow rate error distal to the stenosis was shown to be a function of narrowing severity. Furthermore, pressure differences across an axisymmetric stenotic phantom model were estimated by solving the pressure-Poisson equation (iterative method) and a non-iterative method based on harmonics-based orthogonal projection using PC-MRI velocity data. Results were compared with the values obtained from other techniques including SPIV, computational fluid dynamic (CFD) simulations, and direct pressure measurements. Using the pressure obtained from CFD as the ground truth and PC-MRI velocity data as the input, the relative error in pressure drop for iterative and non-iterative techniques were 13.1 % and 12.5% for steady flow, 4.0% and 22.1 % for pulsatile flow at peak-systole, and 194.5% and 155.2% at end-diastole, respectively. It was concluded that pressure drop calculation using PC-MRI is more promising for steady cases and pulsatile cases at peak-systole compared to pulsatile flow cases at end-diastole

The Cape Town Stereotactic pointer clinical development and Applications

This dissertation describes the development and clinical use of a novel stereotactic neurosurgical system, the Cape Town Stereotactic Pointer (CTSP). This system has four main components; a halo containing three fiducials also serves as the platform for a tripod pointing device which is set with the aid of a 3D phantom or a printed setting diagram, and software which enables transformation of imaging space into patient space. Laboratory tests indicated an application accuracy of 1.9 +/- 0.6mm using the 3D phantom to set the tripod. From the first clinical application, the system underwent a series of iterations which could broadly be divided into four successive phases of refinement. This took place over a six year period, encompassing one hundred patients who underwent 115 stereotactic procedures. Indications for surgery included biopsy (62.6%), aspiration (15.7%) and cannulation (21.7%) and the surgical objective was realized in 101/109 cases (92.7%). Given the fact that six of the eight failures represented errors of surgical judgment that could not be ascribed to the device, and each of two system errors resulted in a significant modification to the system, the CTSP demonstrated a satisfactory level of accuracy in the clinical setting. This was accomplished at an acceptable complication rate, with one death five days after surgery attributable to a stereotactic procedure (mortality 0.9%) and major morbidity in two cases (1.7%); thirteen patients experienced minor complications, all of which proved to be transient (11.3%). A simple protocol for use of the CTSP evolved over the course of this study, making it easier for neurosurgeons from varying backgrounds to introduce stereotaxis into their practice with the help of this system. In addition to satisfactory levels of clinical reliability and safety, the system was versatile and also well tolerated by patients. It is hoped that the CTSP provides a costeffective alternative for neurosurgeons working in under-resourced settings. Sixty units of the production version of the CTSP have been sold and the system is now in use in ten countries