Abstract
In many biomedical imaging applications there is a strong demand for large area sensors. Nowadays the most common detectors in this field are Flat Panel imagers which offer a reasonably large area, typically greater than 20 cm×20 cm. Even so such detectors present severe drawbacks such as large pixels, high noise, low frame rate and excessive image artefacts. In the last two decades Active Pixel Sensors (APSs) have gained popularity because of a potential for overcoming such issues. Furthermore, in recent years, improvements in design and fabrication techniques have made available fabricative processes for wafer scale imagers, which can be now seamlessly scaled from a few centimetres square up to the whole wafer size. A suitable detector for biomedical imaging application needs to fulfil specific requirements: it should have a high spatial resolution, a low noise and a high dynamic range. These figures of merit are connected with the pixel size. Since the pixel size is normally fixed at the time of the design, spatial resolution, noise and dynamic range cannot be further optimized. The authors propose a novel edge-buttable wafer scale APS (12.8 cm×12.8 cm), named the Dynamic range Adjustable for Medical Imaging Technology or DynAMITe, developed by the Multidimensional Integrated Intelligent Imaging Plus (MI-3 Plus) consortium. This APS is based on the use of two different diode geometries in the same pixel array and with different size active pixels. As the effective pixel size is no longer fixed, but two different pixel sizes are used for the whole detector matrix, this detector can deliver two inherently different resolutions each with different noise and saturation performance in the same pixel array. The DynAMITe design has great potential for use in a variety of biomedical imaging applications. In its initial deployment the authors will be developing demonstrators in radiotherapy portal imaging, breast mammography and diffraction imaging and also in sequencing methods for the life sciences.