CT Registry Review Hh

A blood urea nitrogen (BUN) level of 32 mg/dl is considered outside the normal range. BUN is a measure of the amount of nitrogen in the blood that comes from the waste product urea. Higher BUN levels can indicate kidney dysfunction or dehydration, while lower levels can be a sign of liver disease or malnutrition. The normal range for BUN levels is typically between 7 and 20 mg/dl, so a level of 32 mg/dl would be considered elevated and may require further investigation or medical attention.

Barium sulfate is a better oral contrast agent for opacifying the distal small intestine because it is not absorbed by the body and provides excellent visualization of the gastrointestinal tract. Ionic iodinated contrast agents and non-ionic iodinated contrast agents are primarily used for imaging blood vessels and organs, and they are not as effective in opacifying the small intestine.

An array processor is not normally located in the gantry of a modern CT system. The gantry of a CT system typically houses components such as the x-ray tube, detectors, and collimators. The array processor, on the other hand, is a separate component that processes the data collected by the detectors to generate the final CT images. It is usually located outside of the gantry, in the main computer system of the CT scanner.

Two faulty detector elements may cause two parallel lines to appear on a localizer image. The localizer image is created by detecting the X-rays that pass through the patient's body using a detector array. If two detector elements are faulty and not functioning properly, they may produce a consistent error in the detected X-ray data. This error can manifest as two parallel lines on the localizer image, indicating a problem with the detector elements.

The smallest object that can be resolved in this scenario can be calculated using the formula: resolution = FOV / matrix size. In this case, the resolution would be 24 cm / 512 = 0.047 cm. Since the answer choices are in millimeters, we need to convert 0.047 cm to mm, which gives us 0.47 mm. Therefore, the correct answer is 0.47.

A larger value for pitch would stretch the x-ray helix more. In this case, the value of 1.5 is the largest among the given options, so it would stretch the x-ray helix the most.

Barium sulfate solutions used in CT scans are less concentrated than those used in conventional radiography. This is because CT scans require a lower concentration of barium sulfate to achieve the desired contrast in the images. CT scans use a combination of X-rays and computer technology to create detailed cross-sectional images of the body, whereas conventional radiography uses X-rays alone. Therefore, the concentration of barium sulfate needed for CT scans is lower compared to conventional radiography.

If there is no overlap or gap between adjacent slices of a CT scan, the CTDI (Computed Tomography Dose Index) value will be equal to the MSAD (Mean Slice Aggregated Dose). This means that the average radiation dose delivered to each slice will be the same as the overall dose delivered to the patient.

pixel size is equal to reconstruction FOV divided by matrix 320mm divide by 512

To calculate the number of slices necessary, we need to convert the coverage of 2.4 cm to millimeters, which equals 24 mm. Then, we divide the coverage by the thickness of each slice (2 mm) to get the number of slices needed. In this case, 24 mm divided by 2 mm equals 12 slices. Therefore, 12 slices are necessary to meet the radiologist's requirements.

Barium sulfate oral contrast media is selected instead of iodinated oral contrast media because it stays more dense in the distal GI tract. This is important for imaging purposes as it allows for better visualization and assessment of the lower gastrointestinal structures. Additionally, barium sulfate passes through the GI tract more quickly, which can be advantageous in certain situations. However, the fact that the trauma patient may have a perforated bowel is not a determining factor in the selection of the contrast media.

On a multi-row detector scanner, radiation penumbra may be found only on the first and last slices of the slice volume. This is because the penumbra refers to the blurred edges of an image or slice, and in this case, it is caused by the divergence of the radiation beam. As the radiation passes through the patient's body, it spreads out slightly, leading to a slight blurring at the edges of the image. This effect is most prominent at the first and last slices of the slice volume, where the radiation beam enters and exits the patient's body, respectively.

Increasing the scan field-of-view may reduce the out-of-field artifact. Out-of-field artifacts occur when the imaged object extends beyond the field-of-view of the scanner. By increasing the scan field-of-view, a larger area of the object can be captured, reducing the likelihood of artifacts occurring outside the field-of-view. This allows for a more comprehensive and accurate representation of the imaged object.

The normal blood pressure values for adult systolic range from 90 to 140. This means that a healthy adult should have a systolic blood pressure reading between these two numbers. Systolic blood pressure is the top number in a blood pressure reading and represents the pressure in the arteries when the heart beats and pumps blood. A reading within this range indicates that the heart is functioning properly and is able to pump blood effectively throughout the body.

An edge gradient artifact is a streak artifact that arises from a high spatial frequency interface between tissues with a great difference in density. This means that when there is a sharp transition or edge between two tissues that have a significant difference in density, it can cause streaks to appear on the image. This artifact is often seen in medical imaging, such as CT scans, where the density difference between tissues is more pronounced.

If the slice thickness is changed from 5mm to 7mm, the volume of the slice will increase. Since all other parameters are held constant, the number of photons used to make the slice needs to increase in order to maintain the same level of image quality. The increase in slice thickness requires more photons to penetrate through the thicker slice, resulting in a 40% increase in the number of photons used.

Reducing the reconstruction FOV refers to decreasing the area of the image that is reconstructed. This means that less anatomical structures will be included in the final image, resulting in them appearing smaller. Therefore, the correct answer is that anatomical structures appear smaller.

The normal blood pressure values for adults diastolic range from 60 to 90. Diastolic blood pressure represents the pressure in the arteries when the heart is at rest between beats. This range is considered normal and indicates a healthy blood pressure level. Values below 60 may indicate low blood pressure, while values above 90 may indicate high blood pressure.

The 10mm slice from a 20 slice study would display the greatest amount of partial volume artifact. This is because a thicker slice (10mm) is more likely to contain multiple tissue types within its volume, leading to partial volume averaging and blurring of the boundaries between these tissues. In contrast, a thinner slice (5mm) would have less partial volume artifact as it would capture a more precise representation of the individual tissues. The number of slices in the study (20 or 40) does not directly affect the amount of partial volume artifact.

The reconstruction field-of-view determines the spatial resolution. The field-of-view refers to the area of the object being imaged that is included in the reconstructed image. A larger field-of-view will result in a lower spatial resolution, as more information from a larger area is being spread out over the image. Conversely, a smaller field-of-view will result in a higher spatial resolution, as more detail is captured in a smaller area. Therefore, the reconstruction field-of-view directly affects the spatial resolution of the reconstructed image.

Beam hardening is a phenomenon that occurs in computed tomography (CT) imaging when the X-ray beam passes through different types and thicknesses of tissues. As the X-ray beam passes through different tissues, it gets attenuated differently, causing a change in the energy spectrum of the photons in the beam. This change in energy spectrum leads to beam hardening artifacts in the resulting CT image. Therefore, both the types of tissues and the thickness of the tissues traversed by the beam, as well as the energies of the photons in the beam, can affect beam hardening.

The statement that the photon is converted completely into an electron is false. When an x-ray photon penetrates the detector aperture, it may pass through the detector unmeasured or interact with the detector material. In the case of interaction, the photon transfers only a portion of its energy to an electron in the detector material through a process called photoelectric effect or Compton scattering. The electron is then detected and contributes to the measured signal. However, the photon itself is not converted completely into an electron.

The reconstruction interval parameter determines the spacing between consecutive slices during the reconstruction process. If the reconstruction interval is smaller than the collimation (width of the X-ray beam), it causes helical slices to be reconstructed so they overlap. This means that there will be some overlap between adjacent slices, resulting in a smoother and more continuous representation of the scanned object.

A delay of about 35 seconds after the start of the IV contrast injection should be used for helical scan of the neck. This delay allows for optimal distribution of the contrast agent throughout the blood vessels in the neck, ensuring clear and accurate imaging of the area. A shorter delay may result in inadequate contrast enhancement, while a longer delay may lead to excessive contrast dispersion and reduced image quality. Therefore, a delay of 35 seconds strikes a balance between these factors and is considered optimal for this procedure.

Decreasing the slice thickness while covering the same anatomical region does not decrease the patient dose. This is because decreasing the slice thickness allows for more detailed imaging of the anatomical region, but it does not affect the amount of radiation exposure the patient receives. The dose of radiation is determined by factors such as the mA setting and the scan time, which are not changed in this scenario. Therefore, decreasing the slice thickness does not decrease the patient dose.

When a detector element is faulty, it may cause a line artifact on the localizer image that is parallel to the long axis of the patient table. This means that the line will run in the same direction as the table, indicating a problem with the detector element. The other options are incorrect because they do not describe the specific appearance of a faulty detector element artifact on a localizer image.

MAS stands for milliampere-seconds, which refers to the product of the tube current (measured in milliamperes) and the exposure time (measured in seconds). Increasing the MAS will increase the radiation dose delivered to the patient, but it will also increase the number of X-ray photons reaching the image receptor, resulting in a higher signal-to-noise ratio. Therefore, increasing the MAS will reduce patient dose at the expense of increasing the apparent noise in the image.

Bremsstrahlung radiation refers to the electromagnetic radiation emitted when an incoming electron is deflected or slowed down by the electric field of a nucleus. This deflection or slowing down can occur due to the electron colliding with the nucleus of the target atom or due to the electron passing close to the positive charge of the nucleus. However, it does not involve a collision between the incoming electron and an electron in an inner shell of the target atom.

Rescanning and decreasing pitch without changing slice thickness would not help differentiate possible pathology from a partial volume artifact. Changing the pitch would only affect the spacing between slices, not the actual thickness of each slice. Therefore, this strategy would not provide any additional information about the pathology or help in distinguishing it from a partial volume artifact.

The correct answer is "multi-row detector" because this type of scanner design was the first to acquire four slices in a single rotation. This means that the multi-row detector technology allowed for faster and more efficient scanning of the body, as it could capture multiple slices of images simultaneously. This advancement in scanner design greatly improved the speed and accuracy of medical imaging, making it a significant development in the field.

The hepatic arterial phase occurs approximately 20 to 40 seconds after the start of the IV contrast injection. During this phase, the contrast agent reaches the liver through the hepatic artery, allowing for visualization of the arterial blood supply to the liver. This phase is important in detecting and evaluating liver tumors, as they typically receive their blood supply from the hepatic artery. Timing the scan appropriately ensures optimal visualization of the arterial phase and accurate assessment of liver pathology.

The hypoglossal nerve is responsible for controlling the movement of the tongue. It innervates the muscles of the tongue, allowing it to move and function properly. Soft tissues refer to the muscles, connective tissues, and other structures in the body that are not bone or cartilage. Therefore, the hypoglossal nerve is most likely to be found in soft tissues.

Cone beam artifacts can appear as stars coming from structures around the edge of the image. This is because cone beam artifacts occur when the X-ray beam is not aligned with the center of rotation, causing distortion in the image. As a result, structures located near the edge of the image may appear as star-like shapes due to the cone-shaped nature of the beam.

A circle or ring artifact is usually caused by a faulty detector element. This means that there is a problem with one or more of the detectors in the imaging system, which leads to an inaccurate representation of the scanned object. This can result in a circular or ring-shaped pattern appearing in the image, affecting its quality and diagnostic value.

A difference in density of 25 HU between the aorta and the inferior vena cava would indicate the non-equilibrium phase of enhancement. This means that there is a difference in the amount of contrast agent present in these two blood vessels, suggesting that the contrast agent is still being distributed and not yet fully equilibrated.

During the non-equilibrium phase, there is substantial enhancement of the liver compared to tumors. This means that the liver tissue will appear brighter or more enhanced compared to the tumors. However, during the equilibrium phase, there is a possibility of tumor enhancement, which may make the hepatic tumors isodense with liver tissue. This means that the tumors and the liver tissue may have similar levels of enhancement, making it difficult to distinguish between them.

The portal venous phase occurs approximately 60 to 90 seconds after the start of the IV contrast injection. During this phase, the contrast material has reached the portal vein and is circulating through the liver, allowing for optimal visualization of the liver and its vasculature. This phase is important for detecting abnormalities in the liver, such as tumors or vascular lesions.

If an algorithm to correct for the cupping artifact is applied too aggressively to the data for a head image, the center of the image would be too bright. The cupping artifact refers to the darkening of the periphery of an image due to the shape of the imaging equipment. Applying an aggressive correction algorithm would result in the center of the image being excessively brightened, causing an imbalance in brightness distribution.

Metal objects in a localizer image are expected to be represented by high CT numbers and there will be no streaks. This is because metal has a high density and therefore appears bright on the image. Additionally, metal objects can cause streak artifacts due to their high density, but in this case, it is stated that there will be no streaks.

A cupping artifact refers to a distortion in the shape of an image caused by the shape of the imaging device. In the case of a CT scan of the brain, the cupping artifact would appear brighter at the periphery of the brain. This is because the cupping artifact typically causes a darkening effect towards the center of the image, making the periphery appear brighter in comparison.

A typical scan delay following the start of the injection for helical CT examinations of the pancreas is 50 to 60 seconds. This delay allows for the contrast material to reach the pancreas and enhance the visualization of the organ during the scan.

The cranial nerves are a set of 12 pairs of nerves that emerge directly from the brain and are responsible for various functions related to sensory and motor control of the head and neck. They are not seen in the region of the supratentorium, which refers to the area of the brain located above the tentorium cerebelli. The cranial nerves are primarily located within the cranial cavity and do not extend into the supratentorial region. Therefore, the supratentorium is the correct answer as it is not a location where cranial nerves are found.

Beam hardening is a phenomenon that occurs in computed tomography (CT) imaging where the X-ray beam passing through an object becomes harder or more energetic as it passes through denser materials. This can result in CT number inaccuracies, where the measured Hounsfield units do not accurately represent the true tissue density. Streaks in the image can also occur due to beam hardening, as the hardening of the X-ray beam can cause streak artifacts to appear in the reconstructed image. Cupping artifact is another possible manifestation of beam hardening, where there is a darkening or cup-shaped distortion around dense objects in the image.

A scanner with a low data sampling rate would increase the severity of the edge gradient effect because a low data sampling rate means that fewer data points are being collected and recorded during the scanning process. This would result in a lower resolution image and a less accurate representation of the edges and gradients in the scanned object. Therefore, the edge gradient effect would be more pronounced and severe with a scanner that has a low data sampling rate.

When the anatomy being scanned extends outside the scan field of view (FOV), it can cause shading and inaccurate CT numbers. This means that the area outside the FOV is not captured properly, leading to incomplete or distorted images. The shading occurs because the CT scanner cannot accurately measure the attenuation of the tissues beyond the FOV. Additionally, the inaccurate CT numbers result from the incomplete data acquisition, leading to incorrect calculations of tissue densities.

Diluting the contrast solution can minimize beam hardening artifact by reducing the concentration of dense contrast media, which can cause beam hardening. Performing the scan with a slight delay allows the contrast solution to disperse more evenly, reducing the artifact. Performing the scan in the opposite direction can also help minimize beam hardening artifact by reducing the amount of dense contrast media that the beam passes through. These strategies help to reduce the effects of beam hardening artifact and improve the quality of the scan.

The Valsalva maneuver is a technique where the patient blows air out forcefully while keeping their mouth and nose closed. This increases the pressure in the chest and abdomen, causing the pyriform sinuses to distend. The pyriform sinuses are located in the throat and are important for swallowing. The other options, such as epiglottis and vocal cords, are not directly related to the action of blowing the cheeks out to distend the pyriform sinuses.

Beam hardening refers to the increase in the average energy of the photons that reach the detectors. This phenomenon occurs when a beam of X-rays passes through an object and the higher energy photons are less attenuated than the lower energy ones. As a result, the average energy of the photons that reach the detectors increases, leading to beam hardening. This can cause artifacts and inaccuracies in computed tomography (CT) imaging, as the attenuation values of the object may be misrepresented.

The correct answer is 100-180. This range is considered the average pulse rate for an infant. It is normal for an infant's pulse rate to fall within this range. A pulse rate below 100 or above 180 may indicate a potential health issue and should be monitored or evaluated by a healthcare professional.

When the reconstruction FOV (Field of View) is decreased, it means that a smaller area of the image is being reconstructed. This has an impact on the size of the pixels in the image. When the FOV is decreased, the pixel size is reduced, resulting in smaller pixels. Therefore, the correct answer is that the pixel size is increased when the reconstruction FOV is decreased.