Two advantages are obtained with improved energy resolution. First, the photopeak becomes narrower, resulting in more efficient detection of unscattered photons within the chosen energy window. This increases the number of valid events recorded and improves the statistical quality of the image. Second, γ rays scattered through large angles are rejected more efficiently, because their energy spread within the pulse-height spectrum is also smaller. Thus image contrast is improved. It also is true that γ rays scattered through smaller angles are detected somewhat more efficiently, because of the narrowing of their distribution as well. However,the increased efficiency for recording photopeak events more than offsets this effect, in terms of contrast-to-noise ratio (Chapter 15, Section D.2). Alternatively, one can take advantage of the improved energy resolution to use a narrower PHA window, trading back some of the increased efficiency for recording photopeak events for improved rejection of small-angle scatter.Either way, improved energy resolution results in better image quality.