![]() ![]() For instance, if the DPI of a cephalograph is 96, there will be 96×96 pixels in each square inch of the paper-printed cephalograph or on the digital cephalograph, at 100% zoom, seen on the screen, or while being measured using virtual rulers of image-editor programs. ![]() It is measured by the units DPI (dots per inch) or PPI (pixels per inch) that depicts the number of dots on a square-inch span of the image. Interaction with machine-human interfaces (i.e., input/output devices such as scanners, cameras, monitor screen, or printers) introduces a form of spatial resolution called “DPI resolution”, or “pixel density”. The unit megapixel is simply calculated by dividing that size by one million. The names “pixel size”, “pixel dimension” or “pixel resolution” of a digital image equally refers to its size or the number of pixels in the picture, defined as X × Y, where X and Y represent the number of pixel-columns (image width) and pixel-rows (image height), respectively. Although megapixel points to some sort of resolution (like the pixel resolution), this kind of resolution actually means the size of an image and not necessarily its quality. A megapixel is a notion currently overused by companies to advertise the resolution and incorrectly the quality of digital images taken with their products. Pixel resolution (or pixel size) denotes the number of pixels in an image (referring to its image size) while spatial resolution identifies the graphical quality of the image. Pixel or voxel resolution is determined by various elements in the imaging chain, including but not restricted to the detector elements, plus the line spread of data due to some issues such as scintillator usage and detector configuration. DPI is an analog reflection of the way an image is broken down for printing physically or displayed virtually. The following letter tries to cover this issue as well as some other items which were overlooked in the field of dental imaging.Ī computer program only works when properly instructed by the user. Therefore, in the computer era, a simple introduction on this matter to dentists is lacking and thus can be helpful. Nevertheless, the notion of DPI resolution acts like Achilles’ heel when it comes to digital radiography in dentistry.ĭPI resolution is challenging for many dental practitioners, and even some academic radiologists. ![]() Actually, neither pixel size nor DPI tells much about spatial resolution, as the latter refers to the frequencies in an image that can be perceived and was measured in line pairs/mm in earlier days. Line pairs per mm might also be acceptable. In digital radiography, the MTF at either 50% or 10% modulation is the internationally accepted measure for spatial resolution since they produce the highest resolutions. It describes how well an imaging system performs in depiction of fine structures with minimal blur. MTF is calculated from the line-spread function (LSF), and is the method of characterizing the spatial response of an imaging system. Spatial resolution is best described by the modulation transfer function (MTF), since this clearly relates perceptible contrast to spatial frequency in an image. This is because images may need to be digitized, edited, and printed, all of which can produce some artifacts that should be avoided. This, however, can introduce some difficulties to these fields regarding the machine-human interfaces. Hence, practice and research in dentistry are relying progressively on the new format. Moreover, digital radiographs and photographs might provide better accuracy and reproducibility, as dentists can use features of image editor programs (such as digital zoom and color/brightness editing tools) to make the image reading more comfortable ,though with a similar or even better accuracy. Compared to conventional film-based radiographs, their digital alternatives need less X-ray exposure and preparation time, and are much more convenient to handle, store, copy, and share by dentists, radiologists, and patients. Digital imaging has been extremely beneficial to dental practice. ![]()
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