ONE DIMENSIONAL HAND HELD GAMMA RAY SCANNER -
DESCRIPTION (provided by applicant): 1-D Hand-held Gamma Ray Scanner Daghighian, PI Phase I SBIR Dec. 2008 During surgery anatomy and physiology are often altered. Thus, results of preoperative scans often do not fully reflect "present" state-a state that is a "moving target" during the surgical procedure. That is why x-ray C- arm, and ultrasound are being used in many surgeries. It is our hypothesis that with the advances in molecular imaging, an intra-operative gamma ray imager would improve the "real-time" knowledge of the surgeon. The utility of single-detector gamma probes is limited to cases where the background radioactivity is much lower compared to that of the lesion. It is easier to identify a "hot spot" in a gamma ray image than the audio guidance of a gamma probe. In a gamma camera image the eye can discern a 1.5 to 1 contrast. In the last 15 years we and others have built various intra-operative gamma cameras. These camera did not get market acceptance because they were expensive, heavy, and it was difficult to set them up and correlate images with anatomy by surgeons. In this project we will build a novel intra-operative scanner that would alleviate the above problems. The final product that we envision is a one-dimensional array of solid-state photomultipliers (SSPM) coupled to a scintillator slab and tungsten septa, forming a one-dimension gamma ray scanner. A wireless position tracker will be attached to this "scanner" enabling the acquisition of the scanner's position and orientation in real time. While the position-tracker is working, the surgeon would hold it in his/her hand and freely move it over suspicious areas while collecting 1-D gamma ray images. The software would stack these 1-D images next to each other in a 3-D presentation, based on the position and orientation readings of the position-tracker in various time increments. Optical cameras would take pictures and the software would superimpose the nuclear images with the pictures of the surgical field. The composite images will be displayed next to the surgical field. This scanner can open new possibilities in intra-operative nuclear medicine namely: a- Light weight and hand-maneuverable during surgery by the surgeon alone; b- Capability of scanning non-planar surfaces (such as the neck) c- Low cost; list price to customer ~ $20,000. d- Capable of linear scanning as well as angular scanning (such as rotating while inside an incision); e- Can enter the body, through a 15 mm diameter laparo-port, trans-rectally, or trans-vaginally. f- Possibility of building such a scanner for 511 keV without needing an excessively heavy collimator. In our design, we will use a novel photo-detector called the Solid State Photo-multiplier (SSPM). This compact detector has gains close to a million, at a low voltage ~ 70 V. We will couple a 1x8 array of SSPM to a 3x4x50 mm slab of novel and recently discovered scintillating crystal called Lanthanum Bromide (LaBr3:Cr). This crystal outputs 65% more light than NaI(Tl) at a spectral distribution that matches that of the SSPM. There are significant needs for such a scanner, such as: a- Sentinel node imaging in breast and melanoma prior to incision in order to determine how many sentinel nodes are present. Then after the incision, confirming and documenting that all the sentinel nodes are removed. b- Imaging of thyroid cancer, parathyroid adenomas, head-neck sentinel nodes in the operation room. c- Intraoperative imaging of FDG avid tumors for localization of foci of activity shown on the pre-operative PET scans, as well as possibly detecting foci missed by PET. d- Laparoscopic nuclear imaging for detection of sentinel nodes of prostate and GI cancers. e- Trans-rectal imaging of the prostate cancer recurrence using Tc-99m labeled tracers. In Phase I: a- build a gamma scanner utilizing a 1-D array of SSPM-LaBr3:Cr, and using a position- tracker to form a 2-D image. b- test it under realistic conditions to optimize lesion detection with Tc-99m. During the Phase II, we will fully incorporate the position tracking system, and the surface-rendering systems with the gamma ray scanners, fuse the resulting nuclear image with the computer generated 3D rendition of the scanned area, as well as with the visual pictures of the surgical field; explore various ways of real time representation to the surgeon; and with our collaborating surgeons evaluate the efficacy of both scanners. We have extensive experience in developing nuclear medicine instrumentation for surgery. We published the first paper on the medical application of SSPM and applied for patent protection. We have a patent issued for position-tracking of radiation detectors, and have published our preliminary results. We will collaborate with Dr. Magnus Dahlbom of UCLA (co-investigator) on this project. A group of surgeons (see attached letters of support), who see the unique value of such a system, will be evaluating it during the Phase II in melanoma, parathyroid adenomas, breast, thyroid, colorectal and prostate cancers. Innovations include: use of SSPM and lanthanum bromide scintillator, position tracking of a 1-D scanner to form a 2-D image, superposition of visual and nuclear images, and rotational gamma imaging. PUBLIC HEALTH RELEVANCE: This Application has a direct impact on the outcome of cancer surgery. If successful, the proposed method and instrument will result in reduction of the rate of reoccurrence of breast and prostate cancer among others. These two diseases alone afflict half a million of Americans every year. The reoccurrence of cancer causes major emotional trauma in American families and is responsible for rising healthcare costs.
