Beta Camera and Laparoscopic Probe for Surgical Cancer Removal.

DESCRIPTION (provided by applicant): The only certain cure of cancer is the complete removal of the malignant tissue by surgery. A complete removal would prevent the re-growth of the tumor and eliminate the need for a second operation. One of the difficult ies during the operation is to determine if all of the cancerous tissue has been removed from the tumor margin. Currently surgeons rely on visual inspection of the surgical cavity and random tissue sampling of the margins, or pathology results on the excis ed tissue that is often ready after the surgery is concluded. Radiolabeled tumor markers have preferentially high uptake in cancerous cells and offer a unique opportunity for detection of occult tumors at the margin. Background: Beta rays have a range of a few millimeters in tissue. Beta ray detectors, in conjunction with beta emitting isotopes are ideal for detection of occult tumors on the margin since background radiation would not interfere with identification of margins. Previously we have developed a beta probe and beta camera detector and demonstrated that they are selectively sensitive to beta rays. An instrument with imaging capability would further aid the surgeon to quickly and accurately localize any positive tumor margins. Beta cameras have been proposed in the past, but have never been used clinically, because of problems designing a camera that is sensitive and at the same time electrically safe to use during surgeries. Novelty: In this submission, we are proposing a novel beta-camera design ba sed on the use of Solid State Photomultipliers (SSPMs). SSPMs is a relatively new class of photo-sensors that have been shown to have a performance close to that of conventional PMTs, but only requiring operating at tens of volts instead of kV needed for P MTs. Thus, the use of SSPM would significantly alleviate the electrical safety aspect of using the beta-camera intra-operatively. Multiple detector modules will also be tested to increase sensitivity to beta and decrease sensitivity for gamma rays. Prelimi nary Studies: Recently we performed a pilot study that involved 7 patients that underwent lumpectomy. During the procedure, the surgical cavity and excised tissues were surveyed with a beta-probe. We found that the background in the surgical cavity detecte d by the beta-probe was only a 12 18 cps, while a 5 mg generated 3518 cps, showing that the gamma background is low enough to allow detection of uptake in small volumes of tissues. Another conclusion from this study was that an imaging device is needed to allow a more rapid and accurate survey of the surgical cavity. We have built a prototype of the SSPM-based beta camera in an small scale and demonstrated its feasibility. Research Plan (Phase I): We will build the camera with a sheet of plastic scintillato r and a 5x5 array of new ceramic-mounted SSPMs. We will experiment with Peltier coolers to lower the temperature of the SSPM array. We will optimize the sensitivity of the camera, and perform characterization, and limit of detection tests with phantoms. We will test the novel concept of coincidence discrimination to reduce the electronic noise of SSPMs and increase the sensitivity of the camera to low energy beta rays. We will test a dual detector module design to reduce the background gamma sensitivity. We will test a module for the camera with one layer of SSPMs and 2 layers of different scintillators that are differentiated by decay-time constants and phoswitch circuitry. RandD and Clinical Trials Plan (Phase II): The best detector module concept will be selected for building a beta camera for clinical trial. The electronics, mechanical housing, and software for the camera, as well as a Laparoscopic version of the camera will be built and tested during the first part of the Phase II. The prototypes of thes e cameras will be designed to pass electrical and environmental standards of surgical instruments, and will be sent to CSA in order to obtain UL safety certif