Radiographic Image Quality PDF

RADIOGRAPHIC IMAGE  refers to the fidelity with which the anatomical structure that is being examined RADIOGRAPHIC is rendered on the IMAGE QUALITY radiograph. "High quality radiograph" The most...

RADIOGRAPHIC IMAGE  refers to the fidelity with which the anatomical structure that is being examined RADIOGRAPHIC is rendered on the IMAGE QUALITY radiograph. "High quality radiograph" The most important characteristics of radiographic image quality: Contras Spatial t resoluti Noise Resoluti on on  Resolution the ability to image two separate objects and visually distinguish one from the other. Resolution is the ability to accurately image an object expressed as line pairs per millimeter (lp/mm)  Spatial Resolution refers to the ability to image small objects that have high subject contrast, such as a bone–soft tissue interface, a breast microcalcification, or a calcified lung nodule. Detail or recorded detail  Visibility of detail refers to the ability to visualize recorded detail when image contrast and optical density (OD) are optimized.  Contrast Resolution the ability to distinguish anatomical structures of similar subject contrast. Degree of density difference between two areas on a radiograph Noise  Radiographic noise has four components: film graininess structure mottle quantum mottle scatter radiation - principal source of radiographic noise Film graininess refers to the distribution in size and space of silver halide grains in the emulsion.  Structure Mottle similar to film graininess but refers to the phosphor of the radiog raphic intensifying screen.  Quantum mottle is somewhat under the control of the radiologic technologist and is a principal contributor to radiographic noise in many radiographic imaging procedures. Quantum mottle refers to the random nature by which x-rays interact with the image receptor. Speed FILM FACTORS  SENSITOMETRY The study of the relationship between the intensity of exposure of the film and the blackness after processing (OD). Sensitometers (and densitometers) - calibrated annually.  CHARACTERISTIC CURVE H & D curve - Hurter and Driffield, who first described this relationship (1890) D log E curve – Density log exposure Sensitometric curve used to describe the relationship between OD and radiation exposure.  Base plus fog Toe Straight-line portion Shoulder maximum density (Dmax)  The base plus fog (b+f) is the density at no exposure, or the density that is inherent in the Radiographic film base Base film. density ranges around OD plus 0.05–0.10. fog Processing the film usually adds about OD (b+f) 0.05–0.10 in fog density. The total base plus fog is seldom below OD 0.10 but should not exceed OD  The straight-line portion of the curve is that straigh portion between t-line the toe and portion The range of shoulder diagnostic densities varies from a low of OD 0.25–0.50 to a  Dmax is the maximum density the film Dmax is capable of It is the highest recording. point on the D log E curve.  OPTICAL DENSITY (OD) degree of blackening of a radiograph