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ch26 Dig Fluoro
Equipment. Chapter 26. Digital Fluoroscopy
| Question | Answer |
|---|---|
| Pixel size = | image intensifier size/ matrix |
| The difference between conventional and DF is the | nature of the image and the manner in which it is digitized |
| a 1024x1024 image matrix is sometimes described as a ____ line system | 1000. |
| spatial resolution is limited by | pixel size |
| In DF the spatial resolution is determined both by | image matrix size, size of image intensifier. (limited by pixel size) |
| Tube current is measured in ______________ instead of less than 5 mA, as in ii fluoro. | hundreds of mA |
| Images from DF are obtained by pulsing the x-ray beam in a manner called | pulse progressive fluoro. |
| During DF, the x-ray tube operates in the ______ mode | radiographic |
| The time required for the tube to be switched on and reach selected levels of kVp and mA is called the | interrogation time. |
| The time required for the tube to be switched off is the | extinction time |
| The fraction of time that the tube is energized is called the | duty cycle |
| For DF, what two types of image receptors are there? | CCD, Flat panel |
| CCD in Digital is used instead of _______ in conventional. | a TV camera tube |
| What is an image intensifier? | Electronic vacuum tube that amplifies a fluoroscopic image to reduce patient dose |
| When the CCD is directly coupled to the image intensifier, the entire CCD signal is sampled and drives the _____ system | ABC |
| ______ has greater sensitivity to light (DQE), and a lower level of noise than a television camera. The results are a higher ____ and better ________. | CCD. Higher SNR, better contrast res. (results in lower pt dose) |
| Advantages of CCD? | High spatial res, high SNR, high DQE, no warm up required, no lag or blooming, no distortion, no maintenance, unlimited life, linear response, lower pt dose. |
| Perhaps the single most important feature of CCD? | linear response to light |
| Advantages of Flat panel image receptors over CCD image intensifiers? | Distortion free images, improved contrast resolution, High DQE, rectangular image area coupled to similar image monitor, unaffected by external mag fields. (also smaller, lighter, manipulated easier) |
| Image intensifiers are limited by nonuniform spatial res and contrast res from the center to the periphery of the circular image. _____ and ______ increase with age. FPIR is uniform and doesnt degrade. | Veiling glare and pin cushion |
| The DF IR has two alternatives, ________ and _________. So does the display.... _____ and ______. | CCD and Flat panel. Video and flat panel |
| In DF the TV camera tube reads in ___________ mode. | progressive |
| Important characteristics of a DF system that are computer controlled include image _________ ________, the system ______ _______, and the image _______ ______. | matrix size, dynamic range, acquisition rate |
| The principle advantages of DF examinations are the image ____ ____ that are possible, and the enhanced visualization of vasculature that results from venous contrast. | subtraction techniques |
| ________ subtraction techniques are used most frequently because of high voltage generator limitations associated with the ______ subtraction mode. | temporal, energy |
| ________ subtraction refers to an image obtained at one time is subtracted from an image obtained at a later time. If during the intervening period, contrast was introduced, what would the subtracted image look like? | temporal. Subtracted image would contain only the vessels filled with contrast. |
| Two methods commonly used of temporal subtracting? | mask mode and time interval difference (TID) mode. |
| method of temporal subtraction that results in successive subtraction images of contrast filled vessels? | mask mode |
| Technique that produces subtracted images from progressive masks and the frames that follow? | Time interval difference mode (TID) (method of temporal subtraction..) {{Each subtracted image is made from a difference mask and follow up frame}} |
| If patient motion occurs between the mask image and a subsequent image, the subtracted image will contain ___________ artifacts. | misregistration |
| A single kVp setting is used? Rapid kVp switching is required? | temporal, energy |
| filter switching is preferred? Normal beam filtration is ok? | energy, temporal |
| Higher x-ray intensity is required for comparable contrast resolution? Contrast Res is 1mm at 1%. | energy, temporal |
| Imply image subtraction? Complex image subtraction? | temporal, energy |
| Motion artifacts are a problem? Motion artifacts are greatly reduced? | temporal, energy |
| Total subtraction of common structures is achieved? Some residual bone may survive subtraction? | temporal, energy |
| Many more types of subtraction images are possible? Subtraction possibilities are limited by the # of images? | energy, temporal. |
| What is hybrid subtraction? | combing temporal and energy subtraction techniques |
| What is subtraction? | removing or masking all unnecessary anatomy from an image and enhancing only the anatomy of interest |
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