POI MOD 1 2ND SEM

• High-quality images are required for accurate diagnosis by radiologists
• Quality of a radiographic image faithfully reproduces structure and tissues
• A high-quality radiograph has all factors at optimum
• Quality identifies the amount of information available for reviewing the radiograph
• Radiographers evaluate the quality of a radiograph by visual inspection
• Spatial resolution is the ability to image two separate objects and visually distinguish one from the other
• Spatial resolution refers to the ability to image small objects with high subject contrast
• Screen-film radiography has excellent spatial resolution
• Contrast resolution is the ability to distinguish anatomical structures of similar subject contrast
• Differences in Optical Density (OD) in a radiograph indicate radiographic contrast
• If OD differences are small and not distinct, the radiograph is of low contrast
• Noise in radiography is the random fluctuation in the OD of the image
• Principal source of radiographic noise is scatter radiation
• Technique is the systematic procedure used to produce a high-quality radiograph
• Radiographers select and manipulate significant factors: kilovolt-age, milliamperes, exposure time, and distance
• Knowledge of how these factors combine to produce a diagnostic radiograph is the science of radiography
• kVp (Kilovoltage peak) accelerates electrons from the cathode to the anode in radiography
• kVp controls the quality of photons in the x-ray beam and radiographic density
• Milliamperes (mA) increase the number of x-ray photons in the primary beam
• mA controls the amount of blackening on the film
• Exposure time (S) sets the length of exposure and determines the exposure rate when combined with mA
• Source-to-image-receptor distance affects the intensity of radiation due to the divergence of the x-ray beam
• Intensity of an x-ray beam is inversely proportional to the square of the distance from the source (inverse square law)
• Differential absorption is the process of image formation due to varying absorption of the x-ray beam by anatomic tissue
• Differential absorption creates an image that structurally represents the anatomic area of interest
• Beam attenuation occurs due to absorption and scattering of the x-ray beam in tissues
• Absorption results in complete absorption of x-ray photons within tissue atoms
• Scattering occurs when incoming photons lose energy during interactions with tissue atoms
• Transmission happens when x-ray photons pass through the anatomic part without interaction
• Exit radiation, composed of transmitted and scattered radiation, creates an image that represents the anatomic area of interest