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RAD 107 Exam 2
| What is the relationship between the x-ray quantity and mAs? | It is directly proportional to x-ray quantity and receptor exposure. As mAs increases, more x-ray photons are emitted and hit the IR, which prevents quantum mottle. |
| What is the relationship between the x-ray quantity and kVp? | X-ray intensity increases proportionally to the square of the change in kVp. Increasing kVp by 15% will double the overall x-ray/receptor exposure to the IR. |
| Define filtration | It removes low-energy non-penetrating x-ray photons from the beam before they reach the patient, so receptor exposure and contrast decreases. Since low-energy photons are being removed, the quality of the beam increases. |
| What types of voltage ripples are there? | Single-phase, 3-phase 6-pulse, 3-phase 12-pulse, and High Frequency. Determines the stability and energy consistence of the x-ray beam. It measures the percentage drop in voltage from its peak value during x-ray production. |
| What does lower voltage ripple do? | it results in a highly efficient high-energy x-ray beam, is safer, keeps the voltage near its maximum peak value, and creates higher average photon energy and shorter exposure times which decreases motion blur. |
| What does higher voltage ripple do? | Produces a weak inefficient beam, causes the voltage to drop repeatedly, and creates low-energy photons that only increase patient skin dose without helping the image. |
| What is the single-phase voltage ripple? | It has 100% ripple. Voltage drops to zero 120 times per second. Highly insufficient and rarely used. |
| What is the 3-phase 6-pulse voltage ripple? | It has 14% ripple. Voltage never drops below 86% of its peak, significantly increasing beam quality. |
| What is the 3-phase 12-pulse voltage ripple? | It has 4% ripple. Voltage never drop below 96% of its peak, yields more x0ray photons than the 6-Pulse, and highly efficient. |
| What is the High-Frequency voltage ripple? | It has <1% ripple. Modern standard, delivers almost perfectly flat, constant voltage wave, maximizing both image quality and patient safety. |
| What is the effect of voltage ripple on beam quality? | As voltage ripple decreases, the x-ray beam quality increases. Lower voltage ripple are ideal. |
| What is beam penetrability? | the energy and quality of the x-ray beam (ability of x-ray photons to pass through dense tissue) and describes the wavelength and frequency of the x-ray photons. This dictates how easily they can travel through a patient without being absorbed. |
| What is the primary controller in beam penetrability? | Primary controller is kVp, secondary controllers are filtration and generator type for voltage ripple. It controls the subject contrast and gray-scale. |
| What is high penetrability (hard x-rays)? | It's created from increasing kVp as high-energy photons easily pass through dense structures to reach the IR, producing long-scale low-contrast images with many shades of gray. |
| What is low penetrability (soft x-rays)? | It's created from decreasing kVp as low-energy photons are easily absorbed by tissues, resulting in a short-scale high-contrast image with sharp black and white differences |
| What is beam intensity? | The total quantity of number of photons in the beam and the concentration of x-ray photons directed at a specific area over a specific timeframe. |
| What is the primary controller in beam intensity? | Primary controller is mAs, secondary controllers are kVp, distance (Inverse Square Law), and filtration. Controls receptor exposure and image noise. |
| If you increase kVp, what will happen? | Increasing kVp also boosts intensity because higher voltage accelerates electrons faster and more photons are successfully created at a target. |
| How does the beam intensity change? | Intensity changes inversely with the square of the distance from the x-ray source (Inverse Square Law), while penetrability remains unaffected by distance |
| What does high kVp and low mAs do? | High kVp and low mAs as you increase beam penetrability but maintain proper receptor exposure |
| What is the 15% rule? | Increase kVp by 15% and reduce mAs by ½ and if you decrease kVp by 15% you need to double the mAs, to maintain image exposure but reduces the patient’s entrance skin dose (ESD) |
| What is anatomical programming? | Pre-set patient body habitus on controller to prevent manual over-exposure errors |
| What does collimation do? | Limits the x-ray beam to the anatomy of interest to reduce the volume of tissue irradiated. This directly lowers the patient’s effective dose and minimizes scatter radiation, which improves image contrast |
| What type of filtration is required? | Required filtration such as 2.5mm aluminum for systems operating above 70kVp to remove low-energy unnecessary photons |
| What does high-frequency generators do? | Lower ripple and ensures a highly efficient beam with a higher average energy, allowing for shorter exposure times and lower overall dose |
| What does AEC do? | Terminates the exposure once the detector receives enough radiation. This prevents over-exposure and eliminates the need for repeat exposures due to manual timing errors |
| Why should you avoid repeat exposures? | Repeats double the patient’s dose. Poor positioning and patient motion are the common causes and can be prevented by utilizing clear and concise communication, proper breathing instructions, correct positioning, and immobilization devices |
| Why is grid selection important? | Anti-scatter grids improve image contrast but require an increase in mAs to compensate for absorbed photons. Grids should be removed for pediatric patients or thin body parts where scatter is naturally low |
| How should you reduce patient dose by maintaining exposure and lower contrast? | While keeping the image exposure identical, increase kVp by 15% and lower mAs by ½. The IR wil receive the exam same amount of signal, but the patient’s entrance skin dose is significantly reduced because the x-ray beam is more penetrating. |
| What happens when you increase contrast (maintain exposure and higher contrast)? | (Fewer shades of gray, sharper black and white differences), decrease kVp by 15% and double the mAs. Lower kVp results in less penetration and more differential absorption, which increases image contrast while keeping receptor exposure steady |
| If your original technique is 80 kVp @ 20 mAs and your desired change is to lower patient dose, what will your new kVp and mAs be? | New kVp: 92 kVp (80 divided by 12). New mAs: 10 mAs (20 divided by 2) |
| If your original technique is 80 kVp @ 20 mAs and your desired changed is to increase contrast, what will your new kVp and mAs be? | New kVp: 68 kVp (80-12). New mAs: 40 mAs (20 times x) |
| How can you quickly find 15% of a kVp value? | Multiple the original KVp by 0.15 |
| True or False: Foreshortening and Elongation are both shape distortions | True |
| What is foreshortening? | It's caused by the misalignment of the body part itself (body part is angled or improperly positioned). The body part is not parallel to the IR |
| What is elongation? | It's caused by misalignment/angle of the x-ray tube or the IR. The Central Ray is not perpendicular to the body part or IR |
| How do you avoid foreshortening and elongation? | Place the anatomy of interest parallel to the IR, aim the central ray perpendicular to both the body part and the IR, and center the central ray over the midpoint of the body part |
| What is magnification factor? | It measures size distortion, showing how much larger an object appears on an x-ray image compared to its actual size. 1.0 is ideal to capture a true representation of anatomy. |
| What are the formulas for MF? | MF = SID/SOD, Object Size = Image Size/MF |
| Minimizing magnification with SID and OID, what is it used for? | Used to reduce magnification and achieve maximum image sharpness (spatial resolution) |
| Why do you need to minimize OID? | To prevent diverging x-ray photons from spreading out too wide after exiting the patient, keeping the projected shadow true to size |
| Why do you need to maximize SID? | To ensures that only the straightest most parallel central photons pierce the anatomy, minimizing the peripheral, diverging photons that cause magnification |
| What is the effect of patient thickness and body habitus on technique? | Directly dictates the selection of exposure factors because they alter how much radiation is absorbed and scattered. |
| For average sized adults, what radiographic technique will you select? | Every 4cm increase in tissue thickness requires doubling the mAs to maintain identical exposure to the IR. Alternatively, for every 4cm increase in thickness, increase kVp by 15% |
| How should you adjust for hypersthenic patients? | Use a high-ratio anti-scatter grid, high kVp for adequate penetration, and increase mAs |
| How should you adjust for asthenic patients? | Less tissue to attenuate the beam, exposure factors must be significantly reduced to avoid over-penetration and unnecessary radiation dose |
| How should you adjust your technique for pathology? | Conditions pertaining to fluid (ascites) have an increase in tissue density and require higher techniques, while conditions pertaining to air (emphysema) decrease density and require lower techniques |
| What is subject contrast pertaining to the patient and the beam? | The look of the anatomy resulting from how different tissues absorb the x-ray beam and controlled by kVp, tissue atomic number, and tissue density and thickness |
| What is the primary controller of subject contrast? | It is kVp. Low kVp creates high short scale contrast with sharp black and white. High kVp creates a low long scale contrast with many shades of gray from uniform tissue penetration |
| How does the tissue atomic number affect subject contrast? | Tissues with high atomic numbers absorb more x-ray via photoelectric effect than soft tissues, creating high natural contrast. Example: Bone contains calcium and is why they appear white on x-rays. |
| How does tissue density and thickness affect subject contrast? | Thicker tissues attenuate more photons than thin air-filled structures like lungs |
| What is IR contrast? | The raw contrast captured by the detector is heavily altered by software processing before it is viewed |
| What is the Look-up Tables (LUT)? | Mathematical histogram to automatically apply a specific contrast scale based on the anatomy selected, making digital contrast mostly independent of kVp |
| What is Window Width? | Widening the window width increases the scale of grays (lower contrast), while narrowing window width shortens the scale (increasing contrast) |
| What is the formula for focal spot blur? | FSB = FSS x (OID/SOD) |
| What is focal spot size? | Small focal spot decreases penumbra and increases sharper edges (spatial resolution), making it ideal for small bones and extremities |
| How does SID affect spatial resolution? | Increasing SID decreases penumbra and increases spatial resolution |
| How does OID affect spatial resolution? | Decreasing OID decreases penumbra and increases spatial resolution |
| What utilizes a cassette containing a PSP plate? | CR (Computed Radiography) |
| What utilizes flat-panel detectors hardwired or wirelessly connected directly to the computer workspace and doesn't need a separate reader unit? | DR (Digital Radiography) |
| What is indirect conversion? | X-ray photons strike the scintillator (cesium iodide) to create visible light. This light is then converted into an electrical charge by an amorphous silicon photodiode array |
| What is direct conversion? | X-ray photons strike a photoconductor (amorphous selenium) which converts the x-ray photons directly into an electrical charge. This results in the highest spatial resolution because no light is spread to blur the image. |
| What is dynamic range? | The total range of exposure intensities that the detector can accurately respond to and convert into distinct electronic values. CR and DR both have a wide linear dynamic range spanning over 10,000 distinct gray levels |
| What is exposure latitude? | Margin of error allowed for the radiologic technologist. Represents the range of under or over-exposure techniques that can be applied to a patient while still yielding a diagnostic image. |
| What is image acquisition? | Generate digital image data and instantly convert it into compliant network packets |
| What is the network? | Communication highway of PACS. Utilizes local area networks (LAN) within a hospital or clinic or wide area networks (WAN) for remote transfer, requiring high bandwidth to handle massive imaging files |
| What is the storage/archive? | Hardware repository for files. Consists of short-term storage (fast solid-state or hard drive arrays for immediate access) and long-term storage (cloud storage or deep digital archives for multi-year retention) |
| What are the displays/workstations? | Viewing interfaces. Range from high-luminance, calibrated multi-megapixel monitors for radiologist interpretation to standard office screens for hospital providers |
| What is the integration with RIS and EMR? | Integrates seamlessly with hospital information networks via HL7 (Health Level Seven) communication protocols to sync medical data |
| What is RIS (Radiology Information System)? | Operational brain of the radiology department. RIS handles patient scheduling, exam ordering, track logs, and radiologist reports. When a patient arrives, RIS pushes a “Modality Worklist” to the x-ray machine via DICOM, eliminating manual data entry typos |
| What is EMR (Electronic Medical Record)? | Hospital-wide patient file. Once a radiologist signs off on an image in PACS, the written report and direct hyperlink to view the images are automatically funneled into the patient’s EMR profile for the attending physicians to review |
| What is DICOM? | Digital Imaging and Communications in Medicine: universal international standard protocol used across all medical imaging systems |
| What is the short-term image storage? | Images are kept on fast redundant hard drive arrays (RAID). This ensures that any scan from the last 60-90 days, or a patient’s historical comparison scans, can be loaded onto a workstation in under 2 seconds |
| What is the long-term archive? | As images age, PACS software automatically moves them to lower-cost storage, such as cloud storage arrays or deep network-attached storage |
| What is retrieval? | When a patient returns years later, a database query triggers a background fetch, pulling the file back from the long-term archive to the short-term |
| What are the remote devices and teleradiology? | Connect to the hospital network using secure Virtual Private Networks (VPN), utilize lossless compression algorithms, and radiologists and attending physicians can use enterprise-grade mobile apps on tablets or smartphones to view x-rays on the go |
| What is a thick client workstation? | Heavy-duty dedicated computers installed locally within the radiology department. Downloads the full uncompressed DICOM image files from the central PACS servers directly onto its local hard drive for processing. |
| What is a thin client workstation? | Lightweight software applications or secure web browsers used by referring providers, floor nurses, and emergency room providers. |
| What are the common file sizes? | CR/DR (10-30 MB per image), CT (50-1,000 MB per study), mammography (40-200 MB per study) |
| What is compression? | PACS networks compress imaging data to prevent network slowdowns and save archive space |
| What is lossy? | Achieves high compression ratios by permanently discarding redundant or imperceptible image details. It’s used for streaming quick image previews to thin client workstations or mobile devices |
| What is lossless? | Compresses file sizes without losing a single pixel of raw data. The mandatory standard for primary diagnostic reading and legal medial archives, as it ensures zero loss of clinical information |
| What is flatfielding? | Calibration technique that ensures uniform pixel brightness across the entire image. If there are any pixel variations on the x-ray detector, flatfielding uses software to smooth out these inconsistencies, preventing splotchy background |
| What are offset images? | Dark noise images when no x-rays are striking the detector to measure background electronic hiss. The system subtracts this noise from the clinical image |
| What are gain images? | Calibrations taken with a uniform x-ray exposure to adjust each individual pixel’s response scale, ensuring a linear and uniform output |
| What is pixel shift? | Corrects for physical patient motion between sequential image acquisitions. |
| What is DICOM calibration/DICOM Grayscale Standard Display Function? | Universal mathematical standard maps digital image values (pixel values) to specific measurable light outputs (luminance). Without it, we wouldn’t be able to visualize small bone fractures |
| What is perceptual linearization? | Calibrates the monitor’s display curve so that equal changes in an image’s digital value result in equal changes in human visual perception |
| What is SMPTE? | Society of Motion Picture and Television Engineers pattern |
| What is the SMPTE and TG18 test patterns used for? | To check monitor health. These patterns feature distinct grid lines, contrast steps, and 5% and 95% contrast patches to confirm the screen can display extreme highlights and deep shadows without crushing detail. |
| What is photometer use? | Calibrated light-measuring device used during quality control. |
| What is luminance response? | Primary diagnostic displays must maintain a minimum peak luminance of 350-420 cd/m^2 (candelas per square meter or “nits”) |
| What is ambient light? | Diagnostic reading room must be kept dim, ideally between 20-25 lux since high room lighting causes the viewer’s pupils to constrict, reducing their ability to see subtle gray contrasts in dark regions of an x-ray |
| What is specular reflection? | Occurs when light from an overhead bulb or an unshaded window hits the glass monitor screen and reflects directly back like a mirror. This creates distinct geometric reflections that overlay the anatomy, masking tiny findings like pulmonary nodules |
| What is diffuse reflection? | Cccurs when ambient room light blankets the screen uniformly, lifting the overall baseline black levels of the monitor. This washes out the image contrast and narrows the monitor’s effective dynamic range |
| What is visual acuity? | The ability of the human eye to distinguish fine structural details and separate small, closely spaced objects |
| What are rods? | Spread out across the periphery of the retina. Highly sensitive to dim light but provide poor visual acuity and cannot perceive color. |
| What are cones? | Concentrated in the central part of the retina (fovea centralis). They require bright light to function, provide high visual acuity, and perceive color. |
| What is contrast perception? | Human eye can only perceive about 30-40 distinct shades of gray under fixed lighting conditions. |
| What is signal? | The useful diagnostic x-ray photons that pass cleanly through the patient and hit the IR, forming a clear picture of the anatomy |
| What is noise? | Unwanted random variations in pixel brightness that degrade image clarity. Most common type is quantum mottle. |
| What is the Receiver Operating Characteristic (ROC) curves? | A graphical plot used to measure a reader’s diagnostic accuracy or evaluate the performance of AI tools. It plots the relationship between diagnostic true positives and false positives |
| What is sensitivity (true positive rate)? | Probability that the reader will correctly identify a disease when it is present |
| What is sensitivity (true negative rate)? | Probability that the reader will correctly clear a patient when no disease is present |
| What affects spatial resolution? | Pixel size (smaller pixel sizes yield higher spatial resolution), pixel pitch (smaller pixel pitch leads to higher spatial resolution), motion, focal spot blur |
| What affects contrast resolution? | Collimation, compression, kVp selection |
| What is monochrome? | Monochrome (black and white) monitors are the standard for primary radiographic diagnosis. These panels lack filters, delivering high luminance, crisper transitions, and wider dynamic range. |
| What is Color LCD? | Color LCD monitors use sub-pixel color filters (red, green, blue) that absorb light, which reduces peak brightness and narrows the sharp grayscale contrast range. |
| What are megapixels? | Monitor resolution is measured in total megapixels. Standard clinical review stations use 1-2MP scrrens. Primary diagnostic workflows require 3MP monitors for general radiography and 5MP monitors for mammography |
| What is ghosting? | Aka Image Lag, occurs primarily in DR when the IR undergoes a high-exposure exam, residual electrical charge can remain trapped in the amorphous selenium or silicon layer. It shows a faint “ghost” outline of the previous image |
| What is backscatter? | Occurs when high-energy x-ray photons pass completely through the IR, strikes structures behind it such as the table or floor, and scatter backward into the IR. This creates a hazy low-contrast artifact |
| What is incomplete erasure? | A CR-specific artifact. The bright white erasing bulb inside the reader unit may fail to discharge all trapped electrons. |
| How to minimize ghosting? | Increase the amount of time between high-dose exposures to give the trapped charges enough time to naturally decay, acquire the highest-exposure image last, and ensure updated software. |
| How to minimize backscatter? | Utilize strict collimation, lead backing behind the portable DR detector or cassette, use correct technique based on patient’s body habitus to avoid overexposure, and use grids |
| How to minimize incomplete erasure? | Daily morning erasure cycle for CR cassettes at the beginning of every shift, routinely inspect, clean, and calibrate the CR reader’s high-intensity discharge lamps. |
| What are examples of collimators? | Aka Variable-Aperature Collimators, most common and versatile restriction devices that use two sets of adjustable lead shutters. |
| What is PBL? | Aka Positive Beam Limitation, automatic collimator systems equipped with electronic sensors in the Bucky tray. PBL motors automatically actuate the collimator shutters to restrict the exposure field to the exact size of the IR. |
| What are cones and cylinders? | Circular metal tubes that attach to the tube housing to limit the beam to a fixed circle. Cylinders provide better beam restriction than cones because their straight sides reduce penumbra |
| What is the aperature diaphragm? | Fixed lead sheets with a central hole that slide directly below the x-ray tube window. They offer zero adjustments, produce penumbra on images, and are rarely used except in dental or trauma suites |
| What is the collimator and light field adjustment? | Alignment between visible light field and actual x-ray exposure field must be accurate to +/-2% of the SID |
| What is the central ray alignment? | The crosshairs of the light field must align with the true center of the x-ray beam. The central ray must be perpendicular to the IR and center-aligned to within 1% of the SID |
| What is PBL override? | Federal standards allow technologists to manually collimate the field smaller than the cassette/IR size to shield sensitive tissues, but the system must prevent making the field larger than the cassette |
| What is SID dependence? | Beam restriction accuracy is highly dependent on the SID due to the geometric divergence of the x-ray beam |
| What is proportional field scaling? | Any collimator misalignment at the tube housing amplifies linearly as the distance increases. |
| What is penumbra variance? | Penumbra around the edges of the collimated field increases at shorter SIDs and decreases at longer SIDs. Greater SID sharpens the visible borders of the collimated field |
| What is the photoelectric effect? | Total absorption interaction between incoming x-ray photons and an inner-shell electron |
| What is Compton scatter? | Partial absorption interaction between a high-energy incoming x-ray photon and a loosely bound outer-shell electron |
| What is Transmission? | Occurs when x-ray photons pass completely through the patient without interacting with any atomic structures |
| How does Photoelectric contribute to image formation? | It forms bright white/radiopaque structures and high contrast needed to see bone or contrast media |
| How does Photoelectric contribute to patient dose? | The primary source of patient diagnostic dose, energy is completely absorbed in tissue, increasing biological risk |
| How does Compton scatter contribute to image formation? | Scatter photons strike the IR at random angle, creating a uniformity of gray fog which degrades image contrast |
| How does Compton scatter contribute to patient dose? | Scatter photons exit the patient in all directions and the primary source of radiation dose to the radiographer |
| How does Transmission contribute to image formation? | Forms dark radiolucent areas of the image, essential or outlining anatomy |
| How does Transmission contribute to patient dose? | Radiation passes completely through the patient without depositing energy |
| What is radiolucent? | Structures that allow x-ray to pass through easily due to a low effective atomic number and low physical density. Absorb few photons, causing high transmission and dark gray to black shades on the image |
| What is radiopaque? | Structures that readily absorb x-rays due to a high atomic number, high physical density, or both. High atomic number triggers widespread photoelectric absorption, preventing photons from reaching the IR. This leaves these areas bright white. |
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