Comparison of computed tomography shielding design methods using RadShield.

PURPOSE: To comprehensively compare four computed tomography (CT) scanner shielding design methods using RadShield, a Java-based graphical user interface (GUI). METHODS: RadShield, a floor plan based GUI, was extended to calculate air kerma and barrier thickness using accepted methods from the National Council on Radiation Protection and Measurements (NCRP), the British Institute of Radiology, and a method using isodose maps, for spatially distributed points beyond user defined barriers. For a stationary CT scanner, the overall shielding recommendations found using RadShield were also compared to those found by American Board of Radiology certified diagnostic medical physicists using the conventional NCRP dose length product method and the isodose map method. RESULTS: The results between methods differed significantly for calculation point locations beyond the gantry and to the rear of the gantry. Overall shielding design recommendations across the four methods yielded similar average air kerma and thickness values for the barriers. CONCLUSIONS: RadShield was extended to perform CT shielding design and proved reliable using four methods.

RadShield: semiautomated shielding design using a floor plan driven graphical user interface.

The purpose of this study was to introduce and describe the development of RadShield, a Java-based graphical user interface (GUI), which provides a base design that uniquely performs thorough, spatially distributed calculations at many points and reports the maximum air-kerma rate and barrier thickness for each barrier pursuant to NCRP Report 147 methodology. Semiautomated shielding design calculations are validated by two approaches: a geometry-based approach and a manual approach. A series of geometry-based equations were derived giv-ing the maximum air-kerma rate magnitude and location through a first derivative root finding approach. The second approach consisted of comparing RadShield results with those found by manual shielding design by an American Board of Radiology (ABR)-certified medical physicist for two clinical room situations: two adjacent catheterization labs, and a radiographic and fluoroscopic (R&F) exam room. RadShield's efficacy in finding the maximum air-kerma rate was compared against the geometry-based approach and the overall shielding recommendations by RadShield were compared against the medical physicist's shielding results. Percentage errors between the geometry-based approach and RadShield's approach in finding the magnitude and location of the maximum air-kerma rate was within 0.00124% and 14 mm. RadShield's barrier thickness calculations were found to be within 0.156 mm lead (Pb) and 0.150 mm lead (Pb) for the adjacent catheteriza-tion labs and R&F room examples, respectively. However, within the R&F room example, differences in locating the most sensitive calculation point on the floor plan for one of the barriers was not considered in the medical physicist's calculation and was revealed by the RadShield calculations. RadShield is shown to accurately find the maximum values of air-kerma rate and barrier thickness using NCRP Report 147 methodology. Visual inspection alone of the 2D X-ray exam distribution by a medical physicist may not be sufficient to accurately select the point of maximum air-kerma rate or barrier thickness.

Orientation of the round window membrane: A normative study of inner ear anatomical orientation using 2D projections of 3D volumes.

INTRODUCTION: Orientation of the Round Window Membrane (RWM) is an important metric to establish if utilized as a potential access for targeted delivery of magnetically guided nanomedicines to the inner ear. Orientation with respect to an internal reference frame (such as the planes defined by the semicircular-canals [SCC]) may provide an internally consistent basis if the basis is orthogonal and consistent (from patient to patient). MATERIALS AND METHODS: Utilizing a micro computed tomography (CT), 20 temporal bones are scanned for anatomical information. The scanned data sets are loaded into an imaging program to provide volumetric reconstruction and segmentation. Volumetric models of the anatomical relationships between the inner ear SCC and the RWM are utilized to get normative projection angle information and are statistically analyzed. RESULTS: Micro-CT shows low to moderate reliability for reproducibility, intraobserver, and interobserver measurements; in addition, it provides mean values (±SD) for the various measured angles. The combined mean angular values for surface orientation of the RWM, with respect to the SCC basis (quasi-orthogonal spherical coordinate system), was 57.0° ± 20.9°as measured from the line defining the posterior SCC plane in the direction of the line defining the superior SCC plane. An angle of 65.2° ± 19.1° was measured for an angle away from the line defining the horizontal SCC plane.

A Two-Magnet System to Push Therapeutic Nanoparticles.

Magnetic fields can be used to direct magnetically susceptible nanoparticles to disease locations: to infections, blood clots, or tumors. Any single magnet always attracts (pulls) ferro- or para-magnetic particles towards it. External magnets have been used to pull therapeutics into tumors near the skin in animals and human clinical trials. Implanting magnetic materials into patients (a feasible approach in some cases) has been envisioned as a means of reaching deeper targets. Yet there are a number of clinical needs, ranging from treatments of the inner ear, to antibiotic-resistant skin infections and cardiac arrhythmias, which would benefit from an ability to magnetically "inject", or push in, nanomedicines. We develop, analyze, and experimentally demonstrate a novel, simple, and effective arrangement of just two permanent magnets that can magnetically push particles. Such a system might treat diseases of the inner ear; diseases which intravenously injected or orally administered treatments cannot reach due to the blood-brain barrier.