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RAD 107 Exam 1
| Question | Answer |
|---|---|
| What comprises the operating console? | kVp, mA and exposure time, located on the low-voltage side and regulates quality (penetrability) and quantity (intensity) of the x-ray beam, also contains exposure switches |
| What is the line voltage compensator? | measures the incoming voltage from the building and adjusts it to a precise, consistent level, usually 220V, before it enters the rest of the x-ray circuit |
| What is a high-voltage generator? | it converts low-voltage AC power into high-voltage DC for x-ray production |
| What components are in the high-voltage generator? | Step-up transformer, rectifiers, and control unit |
| What is the step-up transformer? | It increases voltage from the primary circuit to kV |
| What do rectifiers do? | Uses diodes to convert AC to DC to ensure electrons flow in one direction from cathode to anode; solid state semiconductors |
| What does the control unit do? | Adjusts the kVp and mA to control the intensity and energy of x-rays |
| What is a single-phase generator? | creates a high voltage ripple of about 100% (voltage drops to zero between peaks). This results in low-energy, lower efficiency, useless x-rays, and higher patient dose. |
| What is a three-phase six-pulse generator? | It has three alternating currents to produce 360 pulses per second. Voltage ripple is about 13-14% and voltage never falling below 87% of peak. Better beam quality, higher efficiency, reduced exposure time |
| What is a three-phase twelve-pulse generator? | Voltage ripple is reduced to about 3-4% and very stable voltage. It never falls below 96% of peak. Produces high-intensity, high-energy beam with low-energy photons and highly efficient |
| What is the formula for calculating high voltage generator power? | Power = max mA (@100 kVp and 100 ms) x 100 kVp |
| What is the primary circuit? | main power supply, circuit breaker, and autotransformer (selects the desired voltage and steps it up slightly before the main transformer |
| What is the secondary circuit? | contains the step-up transformer and rectifiers |
| What does the step-up transformer do? | It increases voltage from the primary circuit to kV, accelerates electrons from the cathode to anode |
| What does the rectifiers do? | converts AC to DC to ensure electrons flow in one direction from cathode to anode and are solid-state semiconductors |
| What does the filament circuit contain? | contains the rheostat, step-down transformer, and filament |
| What does the rheostat do? | controls the resistance to manage the mA sent to the filament |
| What does the step-down transformer do? | reduces the voltage down to 5-15V but increases current to 3-6A to heat the filament |
| What does the filaments do? | emits electrons/thermionic emission in the cathode/boiling off electrons |
| What is the formula for heat units? | HU = 1.35 x kVp x mAs |
| What technical factors determine quality and quantity of x-ray beam | Quality affects penetrability (kVp) and Quantity affects intensity (mAs) |
| Where is the autotransformer located? | In the primary circuit |
| Where is the step-up transformer located? | Between the primary and secondary circuits |
| Where is the rectifiers located? | In the secondary circuit |
| What is the glass envelope used for? | Creates a high-vacuum, heat-resistant enclosure that houses internal components: cathode and anode to prevent oxidation and ensure efficient flow of electrons |
| What is anode damage? | excessive heat during exposures causes the anode to pit or melt. Tungsten target evaporates and deposit on the inner glass walls, which leads to reduced x-ray output and arcing |
| What is burnout/filament failure? | Tungsten filament evaporates over time, breaking down from repeated heating and excessive mA |
| What is vacuum loss? | allows air to enter the tube which leads to arcing, failure, and instability. Cracks in seal failures or glass envelope |
| What is rotating anode bearing failure? | high heat causes the bearings in the rotating anode to wear out, causing rotor failure and noise |
| What is tube aging and improper operation caused from? | using high mAs, neglecting to follow maintenance, causing wear |
| What is arcing? | the vacuum is compromised or metallic deposits coat the interior of the tube, causing sudden failures and erratic operation |
| What is the line focus principle? | It balances high-quality imaging with anode heat capacity by angling the target anode. Using a larger actual focal spot makes the anode handle higher tube loads without melting. Smaller effective focal spot produces sharp images. |
| What is the heel effect? | smaller angles increase the heel effect resulting in lower x-ray intensity on the anode side of the IR |
| What is thermionic emission? | Process of boiling off electrons from tungsten filament in the x-ray tube’s cathode. When the filament reaches an appropriate high temperature, electrons gain enough energy to form a cloud and accelerate via high voltage toward the anode to produce x-rays |
| What is AEC? | Automatic Exposure Control that automatically terminates the radiation exposure once a sufficient amount of radiation reaches the detector |
| What are diodes? | They are in a bridge of 4 diodes for full-wave rectification. Allows the current to flow in one direction. |
| What does the high-voltage cables do? | connects the rectifier output to the x-ray tube |
| What is a bit? | Smallest unit of data in the computer, two values of either 0 or 1, and used for network/transmission speeds (Mbps) |
| What is a byte? | A group of 8 bits, standard unit for storage capacity (MB, GB, TB). One byte is one character |
| What is the binary number system? | A “Base-2” system used by computers and uses values of 0 and 1. Essentially “on” and “off” electronic signals |
| What does the software of the computer do? | collection of data, instructions, or programs that tells the hardware what to do/operate computers and execute specific tasks |
| What is computer language? | formal set of instructions used to write software. Theres “low-level” and “high-level.” FORTRAN is the oldest language for scientific, engineering, and mathematical problems. The U.S. Department of Defense uses ADA. Coding business data uses COBOL. |
| What are pixels? | numerical values that determines the shade of gray. Pixel size = field of view/matrix size |
| What is digital matrix? | grid of rows and column of pixels. Optimal digital matrix size is 1024 x 1024. Higher matrix size and lower pixel size = higher spatial resolution. |
| What is FORTRAN? | Formula Translation, created in the 1950s, and one of the oldest high-level languages in scientific, engineering, and mathematical problems |
| What is memory in regards to computers? | Primary storage where data is kept for immediate use |
| What is RAM? | The Random Access Memory. The volatile memory that stores data currently being used by the CPU. When the power is turned off, all data is lost. |
| What is a processor? | CPU (Central Processing Unit) is the brain of the computer. Carries out instructions from software by performing basic logic, arithmetic, and input/out operations |
| What is DICOM? | Digital Imaging and Communications in Medicine is the international standard for storing, transmitting, and sharing medical images |
| What is input hardware? | devices used to send data to the computer (keyboard, mouse, scanner, digital x-ray detector, and microphone) |
| What is output hardware? | Devices that translate processed data into forms that people can understand (Monitor/display, speakers, and printers) |
| What is photostimulation? | AKA PSL Signaling/Scanning. after the x-ray procedure, the phosphor layer traps the electrons, then the laser sweeps across the plate and this energy releases the electrons (photostimulation). |
| What happens after photostimulation? | The freed electrons recombine with Eu3+ ions (Europium), which is the activator, and emits a bluish-purple light called PSL to create a detectable image |
| What is barium fluorohalide? | Type of phosphor materials used in CR imaging plates to detect, store, and release energy such as iodide or bromide compounds |
| What is PSP? | Photostimulable phosphor uses barium fluorohalide crystals to trap electrons upon x-ray exposure which creates a latent image |
| What is scatter radiation? | Affects the latent image as photons are no longer aligned with the anatomy. It leads to a decrease in signal to noise ratio and low image quality. |
| What is contrast resolution? | the smallest exposure change that can be detected and displayed by the system |
| What is quantum noise? | mottled caused by insufficient number of photons striking the IR. Also called quantum mottle or photon starvation. Can be reduced by using adequate mAs and kVp |
| What is system noise? | random information caused by the electronic components in the imaging system/by the equipment. Can be reduced by proper equipment maintenance and replacing defective parts. |
| What is ambient noise? | random information created by the background radiation striking the IR. It cannot be reduced and is unavoidable. |
| What is scatter radiation? | Affects the latent image as photons are no longer aligned with the anatomy. It leads to a decrease in signal to noise ratio and low image quality. Can be reduced by using grids and careful selection of kVp |
| What is spatial resolution? | the ability of an imaging system to distinguish and define small structures and measured in line pairs per millimeter (lp/mm). It is generally lower in PSP systems compared to direct DR due to laser light spread within the phosphor layer |
| WHat is DQE? | Detective Quantum Efficiency. It is a score that describes the ability of the imaging system to convert the remnant x-ray beam into a high quality image/to detect and convert quantum/photons into an image |
| What is the formula for DQE? | the squared out signal to noise ratio / squared input signal to noise ratio: DQE = (SNR0)^2/(SNRI)^2 |
| What is dynamic range? | the range of exposures that can be captured by an IR (detector limit). It also determines the degree of contrast resolution in the image. |
| What are high frequency generators? | Modern compact systems that convert low-frequency power to higher frequencies to produce stable and efficient x-ray beams with minimum voltage ripple. Reduces radiation hazards, and exposure times, while improving reproducibility and high image quality |
| What is UNIVAC? | Universal Automatic Computer. It was one of the first commercially produced computers in the 1950s |
| What is computer hardware? | physical components of a computer system |
| What are computer programs? | sets of instructions that tell the hardware what to do |
| What is a CPU? | Central Processing Unit. The primary component of a computer that is the control center as it performs calculations and executes instructions |
| What are operating systems? | : fundamental software that manages hardware and other software (Windows) |
| What is COBOL? | One of the first high-level languages used for business and finance. Designed in 1959. |
| What is ADA computer language? | Developed for the U.S. Department of Defense and known for its reliability in critical system and safety such as healthcare and aviation |
| What is a microprocessor? | the brain on a single chip. Allowed big computers in the 1970s to shrink down to small modern day computers |
| What is teleradiology? | modern application that allows radiographic images to be transmitted online from one location to another. Radiologists are able to consult and diagnose remotely |
| What is main memory in regards to computers? | Aka RAM. It is a short-term storage that holds the data and programs the CPU is using. It “erases” when the power is turned off. |
| What are application programs? | Software designed to perform specific tasks like word processors, web browsers, or games for end-users |
| What does digital radiography use? | utilizes a flat-panel detector that directly or indirectly converts x-rays into a digital signal immediately |
| What does computed radiography use? | a PSP imaging plate, usually barium fluorohalide that can be reused |
| What is an imaging receptor? | device that detects x-ray photons after it passes through a patient, converting it into a visible image |
| What is a laser? | device that generates coherent, intense, and highly directional electromagnetic radiation in the x-ray spectrum |
| What are imaging plates? | detector that stores x-ray energy. Composed of PSP, usually barium fluorohalide cystals with europium. After scanning, the plate is erased by using an intense white light and allows for reuse. |
| What is spatial frequency? | the number of line pairs in a given length (lp/mm). The number of details that can fit into a given amount of space. Formula is: SF = 1 / 2 x Pixel Size |
| What is MTF (Modulation Transfer Function)? | score that measures the accuracy of the image compared to the actual object. Aka image fidelity and the systems ability to transfer object information into the image |
| What is the Bar Pattern Test? | uses a line-pair phantom and is a quality assurance tool designed to measure the sharpness of imaging systems (spatial resolution) |
| What is dynamic range? | the range of exposures that can be captured by an IR (detector limit). It also determines the degree of contrast resolution in the image |
| What are the 4 stages of production in CR? | Expose, Stimulate, Read, and Erase |
| What is the exposure phase in CR? | x-ray photons strike the PSP plate, exciting electrons become trapped forming the latent image |
| What is the stimulate phase in CR? | Aka scanning. The laser sweeps across the plate and this energy releases the electrons. The freed electrons combine with the activator Europium ion and emit bluish-purple light called PSL. |
| What is the read phase in CR? | Photomultiplier Tube (PMT) detects the light and converts analog to digital |
| What is the erase phase in CR? | Plate is exposed to intense white light and allows for it to be reused |
Created by:
naomi_taylorrr
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