Dilon Technologies (United States)

Objective: The ultimate goal was to develop a low-power, light-weight, singleuse/recyclable handheld radioisotope detecting probe that would be used in surgery to assist with cancer resection

The ultimate goal was to develop a position tracked hand held gamma camera that would be used in surgery to assist with cancer

Washburn Astronomical Laboratories of the University of Wisconsin-Madison Astronomy Department is developing a near infrared (NIR) integral field spectrograph for the 11-meter Southern African Large Telescope (SALT). This instrument will extend SALT’s capabilities into the NIR, providing medium resolution spectroscopy over the wavelength range of 0.8 to 1.7 microns. The integral field unit (IFU) is optimized for sampling nearby galaxies with an on-sky hexagonal extent of 24 x 28 arcsec containing 217 fibers of 1.33 arcsec diameter (median SALT seeing is 1.5 arcsec). Two separate blocks of 15 sky fibers are adjustable to distances ranging 54 to 165 arcsec from the IFU. This spectrograph, formerly known as RSS-NIR, was originally designed to mount at prime focus coupled to an optical spectrograph through a dichroic beam-splitter. The need to simplify telescope operations at prime focus prompted its reconfiguration into a fiber-fed, cooled, bench spectrograph, resulting in lower instrumental thermal background with a separate cooled collimator, stabilization of the pupil illumination in the spectrograph due to the azimuthal scrambling properties of fibers, and higher throughput at short wavelengths. Field-flattening and sky subtraction with the existing slit spectrograph has been challenging due to SALT’s varying pupil as the instrument payload tracks across the fixed primary mirror during observations. Simulations show that fiber scrambling of the pupil will improve the achievable sky subtraction residuals by 1-2 orders of magnitude. In this paper we present an overview of the reconfigured spectrograph design, its improved expected performance, and the new science drivers for NIR integral field spectroscopy.

This study investigated a novel gamma camera for molecular breast tomosynthesis (MBT), which is a nuclear breast imaging method that uses limited angle tomography. The camera is equipped with a variable angle, slant-hole (VASH) collimator that allows the camera to remain close to the breast throughout the acquisition. The goal of this study was to evaluate the spatial resolution and count sensitivity of this camera and to compare contrast and contrast-to-noise ratio (CNR) with conventional planar imaging using an experimental breast phantom. The VASH collimator mounts to a commercial gamma camera for breast imaging that uses a pixelated (3.2 mm), 15 × 20 cm NaI crystal. Spatial resolution was measured in planar images over a range of distances from the collimator (30-100 mm) and a range of slant angles (-25° to 25°) using 99m Tc line sources. Spatial resolution was also measured in reconstructed MBT images including in the depth dimension. The images were reconstructed from data acquired over the -25° to 25° angular range using an iterative algorithm adapted to the slant-hole geometry. Sensitivity was measured over the range of slant angles using a disk source. Measured spatial resolution and sensitivity were compared to theoretical values. Contrast and CNR were measured using a breast phantom containing spherical lesions (6.2 mm and 7.8 mm diameter) and positioned over a range of depths in the phantom. The MBT and planar methods had equal scan time, and the count density in the breast phantom data was similar to that in clinical nuclear breast imaging. The MBT method used an iterative reconstruction algorithm combined with a postreconstruction Metz filter. The measured spatial resolution in planar images agreed well with theoretical calculations over the range of distances and slant angles. The measured FWHM was 9.7 mm at 50 mm distance. In reconstructed MBT images, the spatial resolution in the depth dimension was approximately 2.2 mm greater than the other two dimensions due to the limited angle data. The measured count sensitivity agreed closely with theory over all slant angles when using a wide energy window. At 0° slant angle, measured sensitivity was 19.7 counts sec-1 μCi-1 with the open energy window and 11.2 counts sec-1 μCi-1 with a 20% wide photopeak window (126 to 154 keV). The measured CNR in the MBT images was significantly greater than in the planar images for all but the lowest CNR cases where the lesion detectability was extremely low for both MBT and planar. The 7.8 mm lesion at 37 mm depth was marginally detectable in the planar image but easily visible in the MBT image. The improved CNR with MBT was due to a large improvement in contrast, which out-weighed the increase in image noise. The spatial resolution and count sensitivity measurements with the prototype MBT system matched theoretical calculations, and the measured CNR in breast phantom images was generally greater with the MBT system compared to conventional planar imaging. These results demonstrate the potential of the proposed MBT system to improve lesion detection in nuclear breast imaging.

Results of the validation of the performance of a gamma-guided localization system using realistic breast phantoms is presented. The system is intended for use in localizing suspected breast cancer lesions not visible with other imaging modalities. The system consists of a pair of slant-hole collimators, a grid localization system and a set of sources that can be seen with the gamma camera. These components are used in three steps: 1) localization of the lesion, 2) correlation of the location with the breast, and 3) verification of the location. Tests with realistic breast phantoms have been conducted to validate the operation of the system in a clinical setting. Phantoms with various lesion sizes and specific activities were used in the validation. A vacuum-assisted core needle biopsy system was used to collect samples from the indicated location, and the fraction of the lesion that was collected by the biopsy system was estimated, in an effort to quantify the operation of the system. The results of these phantom tests will be presented.