Variable field of view for spatial resolution improvement in continuously moving table magnetic resonance imaging

Improving spatial resolution in skin-contact thermography: Comparison between a spline based and linear interpolation

A wearable device for skin-contact thermography [Giansanti D, Maccioni G. Development and testing of a wearable integrated thermometer sensor for skin contact thermography. Med Eng Phys 2006 [ahead of print]] using a 2-D array of 4x4 integrated silicon sensors has been designed and constructed. The thermal resolution was equal to 0.03 degrees C and the spatial resolution equal to 1.6x10(-5) m2 in the range 25-41 degrees C. The improvement of spatial resolution is strongly needed in several medical correlated applications of skin-contact thermography such as the breast cancer monitoring and the feature recognition. A cubic-spline interpolation procedure has been designed to improve the spatial resolution. The performances have been investigated in a significant medical application. Results were compared to those ones obtained by means of an infrared digital video camera and a linear based interpolation procedure. The comparison showed that: (1) the spline based interpolation procedure permitted to improve the spatial resolution of the device to 1.5x10(-8) m2 with an interpolating number of pixels equal to 128x. (2) The accuracy of the thermal reconstruction obtained by means of the spline interpolation in each one of the pixels was better than the one obtained by a pure linear interpolation; in particular the maximal error was equal to, 81x10(-3) degrees C.

Exposure assessment of a mercury spill in a Nevada school -- 2004

BACKGROUND

Although mercury is toxic, few studies have measured exposure in children who handled elemental mercury briefly. In 2004, a student spilled approximately 60 milliliters of mercury at a Nevada school. Within 12 hours, all students were removed from the source of exposure. We conducted an exposure assessment at the school.

METHODS

We administered questionnaires and obtained urine samples from students. Using two-sample t-tests, we compared urine mercury levels from students who self-reported exposure to mercury levels of other students.

RESULTS

Two-hundred students participated, including 55/62 (89%) who were decontaminated. The students' geometric mean urine mercury level was 0.36 microg/L (95% confidence interval 0.32-0.40 microg/L). The student who brought the mercury to school was the only one to have an elevated urine mercury level (11.4 microg/L).

CONCLUSION

Despite environmental contamination, mercury exposure may have been minimized because of rapid identification of the elemental mercury spill and decontamination.

High-resolution continuously acquired peripheral MR angiography featuring partial parallel imaging GRAPPA

Continuously-moving-table MRI, in contrast to traditional multistation techniques, potentially can improve the scan time efficiency of whole-body applications and provide seamless images of an extended field of view (FOV). Contrast-enhanced MR angiography (CE-MRA) in particular requires high spatial resolution and at the same time has rigid scan time constraints due to the limited arterial contrast window. In this study a reconstruction method for continuously acquired 3D data sets during table movement was combined with a self-calibrated partial parallel imaging algorithm (generalized autocalibrating partially parallel acquisitions (GRAPPA)). The method was applied to peripheral CE-MRA and compared with a standard continuously-moving-table MRA protocol. The gain in scan time was used to increase the data acquisition matrix and decrease the slice thickness. The method was evaluated in five healthy volunteers and applied to one patient with peripheral arterial occlusive disease (PAOD). The protocols were intraindividually compared with respect to the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in selected vessel segments, as well as overall vessel depiction. The combination of the continuously-moving-table technique with parallel imaging enabled the acquisition of seamless peripheral 3D MRA with increased resolution and an overall crisper appearance.

Interactive continuously moving table (iCMT) large field-of-view real-time MRI

Continuously moving table (CMT) MRI is a new method that is capable of generating 3D, seamless, large field-of-view (FOV) images by acquiring readouts along the patient superior-inferior axis as the subject is translated through the scanner. For applications that require artifact-free images, such as arterial-phase contrast-enhanced (CE) angiography of the legs, a major challenge is to match the MR data acquisition and patient table motion with the dynamics of blood flow in the region of interest (ROI). Instead of restricting the CMT to predetermined constant table speeds, we adopted a more general approach in which the table motion is decoupled from the phase-encoding order. In our approach the table moves adaptively and in response to operator-provided feedback obtained from viewing real-time preview (or fluoroscopic) images. This interactivity is accomplished by integrating high temporal-spatial resolution encoding of the table position with real-time hybrid-space filling and image reconstruction. Experimental results obtained using our prototype interactive CMT (iCMT) system on a peripheral vascular phantom and five healthy volunteers demonstrate the feasibility of this robust and rapid imaging method for acquiring 3D large-FOV continuous images with patient-specific adaptive table motion profiles.