RTBC SECTION 7. Digital Radiography (Bit depth & Quantization, The Histogram) Questions and Answers Accurate

RTBC SECTION 7. Digital Radiography (Bit depth & Quantization, The Histogram) Questions and Answers Accurate Define Bit Depth shades of gray (grayscale) and shades of gray a pixel can produce When does Quantization take place? Signals that arrive at IR are sampled Define the Quantization process The energy that arrives at the image receptor is converted into an electrical signal Signals are sampled and assigned a number based on the strength of the signal (QUANTIZATION) Increasing Bit depth will have an affect on which factors? Contrast, contrast resolution, Quantization ability to assign value to each pixel corresponding to the gray shade determined by its pixel depth Define Histogram: graph representing range of Exposure values recorded by IR Histogram - “graphical representation” Data collected within collimated border is termed...? A histogram What is displayed on the X- axis of a histogram? amount of exposure What is displayed on the Y-axis of a histogram? the number of pixels for each exposure Describe Histogram Analysis: Determines values of interest (VOI) and exposure index Compares it to a histogram reference stored in computer for each body part What represents patient anatomy on a histogram? VOI VOI SPECIFFICALLY RELATES TO THE STORED HISTOGRAM MODELS ON THE COMPUTER SOFTWARE THAT USES PREESTABLISHED HISTOGRAMS OF THE ANATOMIC PART BEING RADIOGRAPHED IE- The stored histogram models (that are used to fix the preprocessed histogram) contain VOI's which determine the range of the histogram data set (still speaking in terms of the stored histogram models on the software) that should be included on the displayed image What describes the highest spatial frequency that can be recorded by a digital detector? Nyquist frequency the range of histogram data set that should be included in the displayed image VOI VOI SPECIFFICALLY RELATES TO THE STORED HISTOGRAM MODELS ON THE COMPUTER SOFTWARE THAT USES PREESTABLISHED HISTOGRAMS OF THE ANATOMIC PART BEING RADIOGRAPHED IE- The stored histogram models (that are used to fix the preprocessed histogram) contain VOI's which determine the range of the histogram data set (still speaking in terms of the stored histogram models on the software) that should be included on the displayed image Brightness values that represent the anatomic structures of interest is termed what? VOI VOI SPECIFFICALLY RELATES TO THE STORED HISTOGRAM MODELS ON THE COMPUTER SOFTWARE THAT USES PREESTABLISHED HISTOGRAMS OF THE ANATOMIC PART BEING RADIOGRAPHED IE- The stored histogram models (that are used to fix the preprocessed histogram) contain VOI's which determine the range of the histogram data set (still speaking in terms of the stored histogram models on the software) that should be included on the displayed image Define Rescaling digital processing technique that is used to modify and under or overexposed image. Corrects the appearance of an image when small exposure errors are present. Software ability to produce images consistent with brightness and contrast The ideal expression of digital detector image resolution or The expression of image quality provided by a detector is known as? MTF is the MTF The ability of a system to record/represent available spatial frequencies MTF 0-1 is the range the closer to 1 u are the better Does correct collimation have any affect on Histogram analysis? Yes Histogram of luminescent values, increase values on LUT so they can increase contrast and density on image Look-up Table (LUT) Is it important to process the image under the correct anatomy selection on the control panel? Ex. Should you process a chest under a foot setting? It is important because wrong body part selected will use the wrong Histogram