Medical CT Registry Exam Review MCQ Test!

Narrower section thicknesses in medical imaging can lead to reduced partial volume averaging, which occurs when multiple tissues are averaged together in one voxel, resulting in loss of detail. This reduction in partial volume averaging improves the spatial resolution of the image, allowing for better visualization and differentiation of structures.

Pitch is the term that is defined as the table increment in distance per mm per 360 degrees gantry rotation divided by the section thickness in mm. In helical or spiral computed tomography, pitch refers to the distance the table moves per one complete rotation of the gantry. It is an important parameter that determines the speed at which the scanner acquires images and affects the image quality and radiation dose. A higher pitch value indicates a faster scan but lower image quality, while a lower pitch value provides better image quality but slower scan speed.

Statistical noise refers to random variations in pixel values that can occur in CT images. This noise appears as graininess on the image. It is caused by factors such as low radiation dose, low signal-to-noise ratio, or technical limitations of the CT scanner. The graininess can reduce image quality and make it more challenging to interpret the image accurately.

An average CT number water calibration test should be performed daily to ensure accurate and consistent results. This frequent testing helps to calibrate the CT scanner and maintain the accuracy of the CT number measurements. By performing the calibration test daily, any changes or drifts in the CT scanner's performance can be detected and corrected promptly, ensuring reliable and high-quality imaging.

The matrix size refers to the number of pixels used to display an image. A matrix is a grid of pixels, and the size of the matrix determines the resolution of the image. A larger matrix size means more pixels and higher resolution, resulting in a clearer and more detailed image. Therefore, the matrix size directly affects the quality and clarity of the displayed image.

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Decreasing the field of view will magnify the image because a smaller field of view allows for a closer and more detailed view of the object. When the field of view is decreased, the same amount of information is concentrated into a smaller area, resulting in a magnified image.

Hyperdense is the correct answer because it refers to the computed tomography appearance of an intracerebral hemorrhage where the hemorrhage appears brighter or denser on the CT scan compared to normal brain tissue. This is due to the higher CT number of the hemorrhage, indicating a higher density of blood in the area. Isodense refers to when the hemorrhage has a similar density to normal brain tissue, hypodense refers to when the hemorrhage appears darker or less dense than normal brain tissue, and mass effect refers to the displacement or compression of brain tissue by the hemorrhage.

Viscosity is the correct answer as it is the term used to describe the ability of a fluid to flow. Viscosity refers to the internal friction or resistance to flow within a fluid. It is a measure of how thick or sticky a fluid is, and it determines how easily the fluid can be poured or moved. Different fluids have different viscosities, with some being more viscous (thicker) and others less viscous (thinner).

A larger section width would cause a greater amount of partial volume averaging. This is because a wider section width would include more adjacent tissues and structures within the same voxel, leading to an averaging of their signal intensities. Therefore, a section width of 10mm would cause the greatest amount of partial volume averaging compared to section widths of 1mm, 3mm, and 5mm.

The filter selection that would provide the best detail for imaging of the internal auditory canals is "sharp." A sharp filter enhances the edges and fine details in an image, which is crucial for accurately visualizing the intricate structures of the internal auditory canals. Smooth, standard, and soft filters are not as effective in enhancing details and may result in a less clear and accurate image of the canals.

A severe vagal reaction to iodinated contrast material can cause bradycardia, which is a slow heart rate. Atropine is a medication that can be used to increase heart rate by blocking the action of the vagus nerve, which slows down the heart. Therefore, atropine would be an appropriate initial treatment for this patient to counteract the bradycardia caused by the vagal reaction. Diazepam is a sedative and would not directly address the bradycardia. Ranitidine hydrochloride is an antacid and would also not be effective for treating bradycardia. Albuterol sulfate is a bronchodilator and would not have a direct effect on heart rate.

Scans of the pituitary taken in the coronal plane have the advantage of reducing or eliminating streak artifacts. Streak artifacts are unwanted streaks or lines that can appear on an image due to various factors such as metal objects, dense tissues, or motion. By taking scans in the coronal plane, which is a vertical plane that divides the body into front and back halves, the likelihood of streak artifacts is minimized. This allows for clearer and more accurate visualization of the pituitary gland, leading to better diagnostic outcomes.

Filtered back projection is a mathematical technique used in computed tomography (CT) imaging to reconstruct an image from a series of x-ray projections. It involves convolving the projections with a filter function before back projecting them to form the final image. Convolution is a mathematical operation that combines two functions to produce a third function that represents how one function affects the other. In the case of filtered back projection, the convolution is performed between the projections and the filter function, making it the correct answer.

The pineal gland is a small pinecone-shaped structure located in the brain. It is often seen as calcified in CT images, which means that it can appear as a white, dense area on the scan. The pineal gland plays a role in regulating sleep patterns and producing melatonin, a hormone that helps control the sleep-wake cycle. Its calcification can sometimes be associated with certain disorders or conditions, such as pineal gland tumors or calcium deposits.

The correct answer is "edge gradient artifact." An edge gradient artifact is a streak artifact that occurs tangentially to a flat surface with a high spatial frequency. This artifact is caused by abrupt changes in pixel intensity along the edges of an object, resulting in streaks or lines appearing in the image. It is important to be aware of this artifact as it can affect the accuracy and interpretation of the image.

The Hounsfield Unit (HU) is a scale used in computed tomography (CT) to measure the density of a substance. A CT value of +45 HU for blood indicates that blood has a density higher than water, but lower than bone. This is expected since blood contains various components, such as red and white blood cells, plasma, and platelets, which contribute to its density. Therefore, +45 HU is a reasonable average CT value for blood.

During CT angiography, images may be reconstructed using only the greatest density encountered along each ray. This technique is known as Maximum Intensity Projection (MIP). In MIP images, the highest intensity values are displayed, which allows for better visualization of blood vessels and other structures with high contrast. MIP images are commonly used in angiography to highlight the vessels and provide a clearer representation of their anatomy.

Interpolation is the correct answer because it refers to the mathematical technique of estimating an unknown value based on known values on either side of it. It involves creating a function or curve that passes through the given data points and using this function to find the value at the desired point. Interpolation is commonly used in various fields such as mathematics, statistics, computer science, and engineering.

Filtered back-projection is the most commonly used reconstruction method in modern CT scanners. This method involves taking multiple X-ray projections of the patient from different angles and then applying a filtering process to remove noise and artifacts. The filtered projections are then back-projected to create a 2D image of the scanned area. This method is preferred because it produces high-quality images with minimal artifacts and is computationally efficient compared to other methods such as iterative methods or Fourier transform.

The maximum number of shades of gray that can be displayed on CT monitors is determined by the window width. Window width refers to the range of Hounsfield units that are displayed on the monitor. A wider window width allows for a larger range of shades of gray to be displayed, resulting in more detailed and nuanced images. On the other hand, a narrower window width will limit the number of shades of gray that can be displayed, resulting in a less detailed image.

Partial volume averaging is the term used to describe a voxel value that is the average of multiple tissue types contained within the voxel. This occurs when a voxel contains a mixture of different tissues, and the resulting voxel value represents an average of the different tissue densities. This phenomenon can lead to a loss of spatial resolution and can affect the accuracy of measurements and diagnoses in medical imaging.

The correct answer is Compton interaction. Compton interaction occurs when an x-ray photon interacts with an outer shell electron in an atom, causing the photon to scatter and lose energy. This scattered radiation can be absorbed by the patient and detectors. The other options, bremsstrahlung interaction, photoelectric effect, and characteristic interaction, are also interactions between x-rays and matter, but they do not specifically refer to the production of scatter radiation absorbed by the patient and detectors.

The central value in a range of gray shades used to display an image is referred to as the window level. This value determines the brightness or intensity of the image. By adjusting the window level, the user can control the overall brightness of the image, making it easier to visualize specific structures or abnormalities.

Third generation (rotate/rotate) scanners overcame the limitation of translation motion. Translation motion refers to the linear movement of the scanner, which can cause blurring and distortions in the scanned image. Third generation scanners, with their rotating mechanism, eliminated the need for translation motion, resulting in more accurate and high-quality scans.

Contrast resolution is the term used to describe the ability to display an image of a large object that is only slightly different in density from its surroundings. This means that the imaging technique has the capability to distinguish and visualize subtle differences in density or contrast between different tissues or structures in the body.

The tentorium cerebelli is an anatomical structure that forms a roof over the posterior cranial fossa. It is shaped like a tent, with a horizontal portion separating the cerebellum from the occipital lobes of the brain. This structure provides support and protection to the brain, preventing downward displacement of the cerebellum. It also helps to compartmentalize the different regions of the brain, separating the cerebellum from the cerebral hemispheres.

The Compton effect is the correct answer because it involves the scattering of X-ray photons by the electrons in matter. This scattering can cause the X-ray photons to lose energy and change direction, resulting in a larger amount of occupational exposure. The other options, such as the characteristic effect, Bremsstrahlung effect, and photoelectric effect, also involve interactions between X-rays and matter but do not result in as much occupational exposure as the Compton effect.

An analog-to-digital converter is necessary to convert the transmission signal produced by the detectors in a CT scan into numeric information. This is because the detectors measure the intensity of the X-ray beams that pass through the body, which is an analog signal. The analog-to-digital converter converts this analog signal into digital data that can be processed by the computer to reconstruct the CT image.

Scanning thinner sections can help to reduce partial volume artifacts because when the sections are thinner, there is less overlap of different tissues within each voxel. This reduces the mixing of signals from different tissues, resulting in a more accurate representation of each individual tissue type. Consequently, the image will have improved spatial resolution and less blurring, leading to a reduction in partial volume artifacts.

A bow-tie filter is used at the x-ray tube of a CT scanner. This filter is shaped like a bow-tie and is designed to reduce the amount of radiation that reaches the patient's body. It helps to shape the x-ray beam and ensures that the radiation is distributed evenly across the patient's body. This filter is important in CT scanning as it helps to reduce image artifacts and improve image quality.

The section thickness is determined by the incident beam collimation. Incident beam collimation refers to the process of narrowing down the size of the beam before it interacts with the sample. By controlling the collimation, the size of the beam can be adjusted, which in turn affects the section thickness. A narrower beam will result in a thinner section, while a wider beam will result in a thicker section. Therefore, incident beam collimation plays a crucial role in determining the section thickness.

Demerol is classified as an analgesic drug. Analgesics are medications that are used to relieve pain. They work by blocking or reducing the sensation of pain in the body. Demerol, also known as meperidine, is a synthetic opioid analgesic that is commonly used to treat moderate to severe pain. It acts on the central nervous system to alleviate pain by binding to opioid receptors in the brain and spinal cord. As an analgesic, Demerol does not have antipyretic (fever-reducing), antianxiety, or local anesthetic properties.

A photodiode is a solid-state device used to record the light flashes given off by a scintillation crystal. It is a type of semiconductor device that converts light into an electrical current. When light strikes the photodiode, it generates a current proportional to the intensity of the light. This current can be measured and recorded, making the photodiode an ideal choice for detecting and recording the light flashes produced by a scintillation crystal.

The recommended percentage of barium in a barium sulfate suspension utilized in abdominal computed tomography is 1-3%. This concentration range is commonly used because it provides sufficient contrast for imaging while minimizing the risk of adverse effects or complications. Higher concentrations may lead to a higher risk of side effects such as diarrhea or constipation, while lower concentrations may result in inadequate visualization of the gastrointestinal tract. Therefore, a concentration of 1-3% is considered optimal for abdominal CT scans.

The correct order for the stages of infection is as follows: incubation, prodomal, active, convalescence. During the incubation stage, the pathogen enters the body and starts to multiply. The prodomal stage is characterized by the onset of non-specific symptoms such as fever and fatigue. The active stage is when the infection is at its peak, with specific symptoms and the highest level of pathogen replication. Finally, the convalescence stage is the recovery period, where the symptoms gradually subside and the body returns to its normal state.

Silver halide is not commonly used as a CT scintillation detector material. CT scintillation detectors are typically made from materials that can efficiently convert X-ray photons into visible light, such as ceramic rare earth, bismuth germinate, and cadmium tungstate. Silver halide, on the other hand, is commonly used in photographic films but not as a scintillation detector material in CT scans.

Spatial resolution, contrast resolution, and noise all have an effect on image quality. Spatial resolution refers to the ability to distinguish between two objects that are close together, and a higher spatial resolution results in a clearer and more detailed image. Contrast resolution relates to the ability to differentiate between different shades of gray, and a higher contrast resolution leads to better visualization of subtle differences in tissue density. Noise refers to random variations in image intensity, and high levels of noise can reduce image clarity and make it difficult to identify structures. Therefore, all three factors play a crucial role in determining the quality of an image.

Low spatial frequencies in a CT image represent areas that contain minimal changes in tissue density. Spatial frequency refers to the number of changes in pixel intensity across an image. Low spatial frequencies indicate a smooth transition in tissue density, suggesting minimal changes or uniformity in the image. In contrast, high spatial frequencies represent areas with rapid changes in pixel intensity, indicating variations in tissue density. Therefore, low spatial frequencies are electronically represented by the given answer.

Contrast media is introduced into the subarachnoid space for a myelography exam of the spinal canal. This space is located between the arachnoid mater and the pia mater, which surround the spinal cord. By injecting contrast media into the subarachnoid space, it can flow around the spinal cord and help visualize any abnormalities or blockages in the spinal canal. The subdural space is located between the dura mater and the arachnoid mater, the epidural space is located outside the dura mater, and the spinal cord is the structure within the spinal canal.

When obtaining sagittal sections from right to left, the first anatomical structure that would be visualized is the gallbladder. Sagittal sections are taken in a vertical plane that divides the body into right and left halves. The gallbladder is located on the right side of the abdomen, close to the liver. Therefore, it would be the first structure encountered when moving from the right side to the left side of the body.

Ventricular fibrillation is a condition characterized by rapid, irregular, and ineffective twitches of the ventricles. During ventricular fibrillation, the heart's electrical signals become chaotic, causing the ventricles to quiver instead of contracting normally. This results in the heart being unable to pump blood effectively, leading to a lack of oxygen supply to the body. Ventricular fibrillation is a life-threatening condition that requires immediate medical intervention, such as defibrillation, to restore the heart's normal rhythm.

Beam hardening refers to the increase in the mean energy of a polychromatic beam as it passes through an object. This occurs because the lower energy photons are preferentially absorbed, resulting in a higher proportion of higher energy photons in the beam. This phenomenon can cause artifacts in computed tomography (CT) images, where the attenuation values of the object may be inaccurately represented due to the beam hardening effect.

If the section thickness is changed from 5 mm to 10 mm, the number of detected photons will increase by 100%. This is because the thicker section allows for more photons to interact with the detector, resulting in a higher number of photons being detected.

Compton scattering is the primary type of interaction that contributes to the subject contrast in CT images. Compton scattering occurs when an incoming X-ray photon interacts with an outer shell electron in the subject, causing the photon to change direction and lose some of its energy. This scattering process leads to variations in the intensity of X-rays detected by the CT scanner, which ultimately contributes to the contrast seen in the resulting images.

The primary interaction between x-ray photons and tissue during CT examinations is the Compton effect. This occurs when an x-ray photon interacts with an outer shell electron in the tissue, causing the photon to scatter in a different direction and lose some of its energy. This interaction is important in CT imaging as it contributes to the formation of the image by providing information about the density and composition of the tissue being examined.

Retrospective refers to the act of looking back or reflecting on past events or experiences. In the context of the question, when an image is reconstructed a second time with some change in technical factors, it can be considered a retrospective action as it involves revisiting and modifying the image after its initial creation. The term "retrospective" accurately describes this process and aligns with the given scenario.

Rotate-rotate scan geometry is responsible for producing ring artifacts. In this type of scan geometry, the X-ray tube and detector rotate continuously around the patient in the same direction. This results in incomplete data acquisition and uneven sampling, leading to ring artifacts in the reconstructed images. These artifacts appear as concentric rings or circular patterns, causing image distortion and reducing image quality.

The correct answer is L4. The abdominal aorta bifurcates at the level of L4 into the right and left common iliac arteries. This is an important anatomical landmark as it marks the transition from the abdominal aorta to the pelvis and lower extremities.

All three types of contrast material mentioned (diatrizoate meglumine, barium sulfate, and iopamidol) may be used during a CT examination of the chest. Diatrizoate meglumine is an iodine-based contrast agent that enhances the visibility of blood vessels and organs. Barium sulfate is a contrast agent used for gastrointestinal imaging. Iopamidol is another iodine-based contrast agent commonly used for CT scans. Therefore, all three options are correct and may be used during a CT examination of the chest.