Imaging techniques for the radioimmunodetection of cancer.

ABSTRACT

Problems in the radioimmunodetection of cancer typically involve small lesions having low object contrast. As such, the imaging device utilized must have a high spatial resolution as well as high detection efficiency. In addition, the imaging device must be interfaced to a computer system to allow data manipulation to include background substraction, contrast enhancement, and organ subtraction techniques to be used. While the conventional scintillation camera is the most widely used imaging device in conventional nuclear medicine imaging procedures, this system does not provide adequate imaging performance for radioimmunodetection of cancer. This is true since these devices typically do not provide adequate object contrast when detecting small lesions in the presence of moderately high background activity. The Pho/Con (Searle Radiographics) is a tomographic imaging device which, when interfaced to a computer system, is capable of providing adequate lesion detection for this specialized procedure. The newest version of this tomographic imaging system has a spatial resolution and a detector efficiency which are comparable to those of the conventional scintillation camera. The system has the added advantage of relatively constant high-spatial-resolution performance as well as high sensitivity over a wide range of depths. In addition, the imaging process involves a rectilinear scanning motion which results in inherently uniform response in each plane of interest. These combined properties result in high detection of small lesions in cases where the object contrast is extremely low. These inherent imaging properties when combined with the improved contrast provided with computer manipulation of data make this system ideal for radioimmunodetection problems. In this paper, the importance of spatial resolution, count density, lesion size, and object contrast are discussed in relation to the detectability of lesions in radioimmunodetection of cancer. In addition, the characteristics of the Pho/Con and its advantages in lesion detection are described.