To visualize this, imagine a stamp with one letter on it - the point size would be not the size of the letter, but the physical height of the stamp. Historically this is the physical height of the lead block used for printing with the printing press - it has a single letter on it. The actual size in inches or millimeters refers to the value called body size, under number 6 in the illustration. The value of one point is equal to 1/12 of a pica. For example, much of the academic writing and business correspondence is done in sizes between point 10 and point 12. Points (pt) are the units conventionally used to determine the size of the font. The height of the stamp is an example of body size The size of the letters is measured using the following dimensions (pictured): There are several conventions for calculating pica. However, often instead of pica, the units derived from it, such as points, are used. Sometimes pica is used directly, for example, to measure margins and column sizes. In typography, the size of letters and characters is measured with the help of a basic standardized unit, pica (pc). Each pixel represents a dot (or a square) that makes up an image on the screen. While centimeters or inches can be employed, units called pixels are also used. Despite these inconsistencies, size does help designers to know how much space a given text takes up on a page, and as such is a useful measure in desktop publishing.ĭigital images are also measured in desktop publishing, to ensure that they fit well in the allotted space. For some of these conventions, the same size of letters in two different fonts may not mean that they have the same linear dimensions, as described below. There are several conventions for specifying the size of letters. Typography is concerned with manipulating size and font types to make pages with a pleasing and easy-to-read appearance. Other classifications also exist.Ī screenshot of Adobe InDesign - a desktop publishing application produced by Adobe Systems. Each group of fonts differs in several design elements such as in their thickness, contrast between thick and thin lines, and the shape of the serifs. There are also other groups in this classification. Other classifications divide fonts based on their historic origins: the old style or old face includes the oldest fonts transitional types are the ones that historically followed the oldest ones modern types are fonts that were designed after the transitional types and until about the 1820s and modern types or modernized old-style types include modern fonts that imitate the true old style but are designed in the modern times. The other letter in yellow is in a sans-serif font, Futura. Here one of the four serifs is marked in red. In the illustration, the first letter in blue is in a serif font, Bodoni. Bad typography, on the other hand, can make the text difficult to read.įonts are classified into different types, such as serifs (fonts with decorative elements named serifs) and sans serifs (fonts without serifs). Arranging letters on the page well and following the principles of good typography can impact the reader and strengthen the message that the designer is trying to convey. It emerged around the invention of the printing press in the mid-fifteenth century. If the AP and lateral dimensions of the patient are available, then the SSDE can be used to estimate the absorbed dose.Typography, the study of type, is concerned with the appearance of letters, including their shape, size, and color. They should be taken as an index of radiation output by the system for comparison purposes. It is important to remember that the CTDI vol or its derivative the DLP, as seen on consoles and outputted on the DICOM images, do not represent the actual absorbed or effective dose for the patient. CTDI vol (mGy) is obtained by dividing CTDI w by pitch factor.Īnother commonly used index is the dose-length product (DLP) which factors in the length of the scan to show overall dose output. ![]() CTDI w (mGy) is closer to the human dose profile as compared with the CTDI 100.CTDI 100 (mGy) is a linear measure of dose distribution over a pencil ionization chamber and hence does not take into consideration the topographical variation of a human body and is therefore not in clinical use.In the past CTDI 100 (measured over a 100 mm long ionization chamber) and CTDI w (weighted average of dose across a single slice) were used for helical scanners in current use, the parameter CTDI vol is the more commonly used index. CT dose index (CTDI) (measured in mGy) is a standardized measure of radiation dose output of a CT scanner which allows the user to compare radiation output of different CT scanners.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |