We suggest to enhance the performance of image acquisition systems based on large area amorphous silicon-based sensors by optimizing the readout parameters such as the intensity and cross-section of scanner beam, acquisition time and bias conditions. The sensor responsivity and signal-to-noise ratio is related to basic parameters such as image intensity, scanner intensity and sensor bias. The influence of bias voltage, scanner beam spot size and wavelength and scanning speed on the sensor output characteristics are evaluated. It was shown that the sensor resolution is related to the basic device parameters and, in practice, limited by the acquisition time and scanning beam properties. The scanning beam spot size limits the resolution due to the overlapping of dark and illuminated zones leading to a blurring effect on the final image and a consequent degradation in the resolution. The sensor response is limited by the external load, which for fast scanning speed should be kept small.