Localizing the Imaged-Object Position by a Stationary Position-Sensitive Scintillation Camera Using Tilted-Collimator Technique

A method to measure the detector-to-object distance from the images obtained with a stationary high-spatial-resolution gamma-ray camera for in-vivo small-object studies has been developed. It exploits the shift of the imaged object in the image plane, obtained for tilted positions of a parallel-hole collimator. In this way three-dimensional information about the object position can be obtained without moving either the camera or the object. The effectiveness of the method has already been tested for point-like gamma-ray emitting objects in our previous studies. In the present work we show the results of series of measurements conducted for three-dimensional small-size objects. Gamma-ray images from cavities filled with a solution of 99m Tc at different depth position in tissue equivalent phantoms have been analyzed. A linear dependence of the image displacement on the object distance has been measured, using a scintillation camera employing an yttrium-aluminum perovskite (YAP) scintillator. A prototype of a computer-guided manipulator, designed for on-line operations such as e.g. needle biopsy, is presented. The instrument design and the preliminary results are discussed.