CT Imaging Procedures Test: Quiz!

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CT Imaging Procedures Test: Quiz! - Quiz

Doctors use a computed tomography(CT) scan to view your body's inner organs, like bones and tissues, to diagnose diseases and evaluate injuries. Through CT scans, doctors can see and observe your body's various parts like bones of the shoulders, spine, abdomen, etc. This quiz will evaluate your knowledge about CT imaging procedures.


Questions and Answers
  • 1. 

    High resolution CT is most commonly used for the evaluation of the:

    • A.

      Pancreas

    • B.

      Brain

    • C.

      Lung

    • D.

      Mediastinum

    Correct Answer
    C. Lung
    Explanation
    High resolution CT is most commonly used for the evaluation of the lung. This imaging technique provides detailed images of the lung structures, allowing for the detection and evaluation of various lung conditions such as lung cancer, pulmonary fibrosis, and pneumonia. High resolution CT can help identify abnormalities in the lung parenchyma, airways, and blood vessels, providing valuable information for diagnosis and treatment planning. It is a non-invasive and effective tool for assessing lung health and detecting any potential abnormalities or diseases in this vital organ.

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  • 2. 

    During a CT guided needle biopsy, the needle insertion site is usually anaesthetized with:

    • A.

      Diazepam

    • B.

      Lidocaine

    • C.

      Lithium

    • D.

      Oxycodone HCI

    Correct Answer
    B. Lidocaine
    Explanation
    During a CT guided needle biopsy, the needle insertion site is usually anaesthetized with lidocaine. Lidocaine is a local anesthetic that is commonly used to numb the skin and surrounding tissues. It works by blocking the nerve signals in the area, preventing the transmission of pain signals to the brain. This helps to minimize any discomfort or pain during the procedure, allowing the biopsy to be performed more easily and safely. Diazepam, lithium, and oxycodone HCI are not typically used for local anesthesia during this type of procedure.

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  • 3. 

    Which of the following abnormal findings reduces the density of the liver?

    • A.

      Hyperdense cyst

    • B.

      Contrast enhancing tumor

    • C.

      Fatty liver

    • D.

      All the above

    Correct Answer
    C. Fatty liver
    Explanation
    A fatty liver is an abnormal finding that reduces the density of the liver. It occurs when there is an excessive accumulation of fat in the liver cells, leading to a decrease in the liver's density. This can be caused by various factors such as obesity, alcohol abuse, diabetes, and certain medications. A hyperdense cyst and contrast enhancing tumor, on the other hand, would increase the density of the liver. Therefore, the correct answer is fatty liver.

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  • 4. 

    Which of the following sets of section widths and spacing is the most suitable for a general survey CT of the neck?

    • A.

      1.5 mm thick every 1.5

    • B.

      3mm thick every 5mm

    • C.

      5mm thick every 5mm

    • D.

      10mm thick every 10mm

    Correct Answer
    C. 5mm thick every 5mm
    Explanation
    The most suitable set of section widths and spacing for a general survey CT of the neck is 5mm thick every 5mm. This means that each section will be 5mm thick and there will be a spacing of 5mm between each section. This set allows for a good balance between image resolution and data acquisition time. It provides enough detail to visualize structures in the neck while also reducing the amount of time needed to acquire the images.

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  • 5. 

    The _________ gland is located in the AP portion of the mediastinum and is often identified with CT when scanning younger PT's.

    • A.

      Thyroid

    • B.

      Luschka

    • C.

      Thymus

    • D.

      Parathyroid

    Correct Answer
    C. Thymus
    Explanation
    The thymus gland is located in the anterior-posterior (AP) portion of the mediastinum and is often identified with CT when scanning younger patients.

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  • 6. 

    Which of the following CT Studies of the head may be performed W/O contrast?

    • A.

      CT angiogram for the Circle of Willis

    • B.

      Coronal CT scan to rule out pituitary tumor

    • C.

      CT of the brain to r/o hematoma

    • D.

      CT of the brain to r/o metastatic disease

    Correct Answer
    C. CT of the brain to r/o hematoma
    Explanation
    CT of the brain to rule out hematoma may be performed without contrast because a hematoma can usually be visualized without the need for contrast enhancement. Contrast agents are typically used to enhance the visualization of blood vessels or to identify specific abnormalities, such as tumors or metastatic disease. However, in the case of a hematoma, the blood collection is usually easily distinguishable on a non-contrast CT scan.

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  • 7. 

    CT scanning of the liver for tumor evaluation should not be performed during which of the following phases of contrast enhancement.

    • A.

      Non equilibrium phase

    • B.

      Equilibrium phase

    • C.

      Dynamic phase

    • D.

      Bolus phase

    Correct Answer
    B. Equilibrium phase
    Explanation
    During the equilibrium phase of contrast enhancement, the contrast agent has distributed evenly throughout the liver and surrounding tissues. This phase is not ideal for tumor evaluation because it does not provide optimal visualization of the tumor due to the homogeneous distribution of the contrast agent. In contrast, the dynamic phase and bolus phase provide better visualization of tumors as they capture the initial uptake and washout of the contrast agent, respectively. The non-equilibrium phase is not a recognized phase of contrast enhancement, so it is not relevant to the question.

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  • 8. 

    The Kidneys are located anatomically between which vertebrae.

    • A.

      T6 and L2

    • B.

      T12 and L3

    • C.

      L2 and L4

    • D.

      L3 and S1

    Correct Answer
    B. T12 and L3
    Explanation
    The kidneys are located anatomically between the twelfth thoracic vertebra (T12) and the third lumbar vertebra (L3).

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  • 9. 

    Axial CT images of the knee may be acquired in five separate series with knee flexions of 0, 15, 30, and 45 degrees in order to demonstrate the:

    • A.

      Tibial plateau

    • B.

      Patellofemoral joint

    • C.

      Medial and lateral menisci

    • D.

      Anterior cruciate ligament

    Correct Answer
    B. Patellofemoral joint
    Explanation
    Axial CT images of the knee may be acquired in five separate series with knee flexions of 0, 15, 30, and 45 degrees in order to demonstrate the patellofemoral joint. This is because the patellofemoral joint is best visualized when the knee is flexed. By acquiring images at different degrees of flexion, it allows for a comprehensive evaluation of the patellofemoral joint and helps to assess any abnormalities or pathology in that region.

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  • 10. 

    CT images acquired of the foot in a plane perpendicular to the long axis of the scout image shown are considered __________ images.

    • A.

      Axial

    • B.

      Sagittal

    • C.

      Coronal

    • D.

      Transaxial

    Correct Answer
    C. Coronal
    Explanation
    CT images acquired of the foot in a plane perpendicular to the long axis of the scout image shown are considered coronal images. Coronal images are obtained by taking slices perpendicular to the sagittal plane, dividing the body into front and back sections. In this case, the foot is being imaged from a side view, allowing for a clear visualization of the structures in the coronal plane. Axial images are obtained by taking slices parallel to the ground, sagittal images are obtained by taking slices perpendicular to the ground and parallel to the body's midline, and transaxial is not a commonly used term in medical imaging.

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  • 11. 

    Which of the following is used to describe a set of rules for solving a mathematical problem?

    • A.

      Reconstruction

    • B.

      Algorithm

    • C.

      Function

    • D.

      Array

    Correct Answer
    B. Algorithm
    Explanation
    An algorithm is a set of rules or instructions that are used to solve a mathematical problem. It is a step-by-step procedure that outlines the specific actions or operations to be performed in order to reach a solution. Algorithms are commonly used in mathematics and computer science to solve complex problems efficiently and accurately. They provide a systematic approach to problem-solving and are essential in various fields, including data analysis, programming, and optimization.

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  • 12. 

    A 15 second spiral CT scan of the pelvis is performed using 1.0cm aperture size. If a pitch of 1:1 was used for the total length of coverage for this scan would be:

    • A.

      50cm

    • B.

      100cm

    • C.

      150cm

    • D.

      250cm

    Correct Answer
    C. 150cm
    Explanation
    A pitch of 1:1 means that for every centimeter the CT scanner moves, it also covers a centimeter of the patient's body. In this case, the CT scan is performed using a 1.0cm aperture size, which means that the scanner covers 1 centimeter of the patient's body with each rotation. If the total length of coverage is calculated by multiplying the aperture size by the number of rotations, the total length of coverage for this scan would be 150cm (1.0cm x 150 rotations = 150cm).

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  • 13. 

    A CT image should be viewed on the monitor in which of the following orientations.

    • A.

      From the feet toward the head with PT's left on the viewers left

    • B.

      From the feet toward the head with the PT's left on the viewers right

    • C.

      From the head toward the feet with the PT's right on the viewers right

    • D.

      From the head toward the feet with the PT's right on the viewers left

    Correct Answer
    B. From the feet toward the head with the PT's left on the viewers right
    Explanation
    The correct answer is "from the feet toward the head with the PT's left on the viewers right." This orientation is commonly used in radiology to view CT images. It allows for consistent and standardized interpretation of the images. By viewing the images in this orientation, the radiologist can easily identify anatomical structures and abnormalities based on their location and orientation.

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  • 14. 

    In which of the following cranial nerves would an acoustic neuroma be found?

    • A.

      Third

    • B.

      Eighth

    • C.

      Tenth

    • D.

      Twelfth

    Correct Answer
    B. Eighth
    Explanation
    An acoustic neuroma is a noncancerous tumor that develops on the eighth cranial nerve, also known as the vestibulocochlear nerve. This nerve is responsible for transmitting sound and balance information from the inner ear to the brain. Therefore, it is logical that an acoustic neuroma would be found on the eighth cranial nerve.

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  • 15. 

    Which of the following interscan delays would be used for a dynamic CT study of the chest?

    • A.

      4 sec

    • B.

      8 sec

    • C.

      12 sec

    • D.

      15 sec

    Correct Answer
    A. 4 sec
    Explanation
    For a dynamic CT study of the chest, a shorter interscan delay is preferred in order to capture rapid changes in the chest area. A delay of 4 seconds allows for more frequent scans, providing a higher temporal resolution to capture the desired dynamic information. Longer delays such as 8, 12, or 15 seconds would result in fewer scans and potentially miss important changes occurring within the chest during the study.

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  • 16. 

    Which of the following types of pathologic conditions cannot be easily diagnosed from a CT Scan of the brain?

    • A.

      Astrocytoma

    • B.

      Traumatic herorrhage

    • C.

      Cerebral infarct

    • D.

      Alzheimers disease

    Correct Answer
    D. Alzheimers disease
    Explanation
    Alzheimer's disease cannot be easily diagnosed from a CT scan of the brain because it is a neurodegenerative disorder that primarily affects the brain's structure and function over time. CT scans primarily provide detailed images of the brain's structure, but they may not show specific changes or abnormalities associated with Alzheimer's disease. Diagnosis of Alzheimer's disease typically requires a combination of clinical evaluation, cognitive tests, and sometimes advanced imaging techniques like MRI or PET scans to assess brain function and detect characteristic changes in the brain associated with the disease.

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  • 17. 

    Most pancreatic tumors occur in the pancreatic.

    • A.

      Head

    • B.

      Body

    • C.

      Tail

    • D.

      Uncinate process

    Correct Answer
    A. Head
    Explanation
    Pancreatic tumors are most commonly found in the head of the pancreas. The head of the pancreas is located on the right side of the abdomen, near the duodenum. This is where the majority of pancreatic tumors, including pancreatic adenocarcinoma, arise. Tumors in the head of the pancreas can cause symptoms such as jaundice, abdominal pain, and weight loss. Treatment options for pancreatic tumors in the head of the pancreas may include surgery, radiation therapy, and chemotherapy.

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  • 18. 

    Before scanning the liver after a bolus injection of contrast, a delay of ___ should be applied.

    • A.

      0 sec

    • B.

      20 sec

    • C.

      45 sec

    • D.

      120 sec

    Correct Answer
    C. 45 sec
    Explanation
    A delay of 45 seconds should be applied before scanning the liver after a bolus injection of contrast. This delay allows the contrast to circulate through the bloodstream and reach the liver, ensuring optimal visualization of the liver during the scan. Waiting too short of a time may result in inadequate contrast enhancement, while waiting too long may lead to excessive contrast washout and suboptimal image quality. Therefore, a delay of 45 seconds strikes a balance between allowing sufficient time for contrast distribution and minimizing unnecessary waiting time.

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  • 19. 

    Which of the following technical changes may increase the partial volume effect present on a spiral CT scan?

    • A.

      Decrease in pitch

    • B.

      Decrease in aperture size

    • C.

      Increase in matrix size

    • D.

      Increase in pitch

    Correct Answer
    D. Increase in pitch
    Explanation
    An increase in pitch on a spiral CT scan refers to the distance between each consecutive scan. When the pitch is increased, the scanner covers a larger distance in a shorter amount of time, resulting in a decrease in the number of scans taken. This can lead to an increase in the partial volume effect, where structures with varying densities can appear blurred or misrepresented due to the limited resolution of the scanner. Therefore, an increase in pitch can increase the partial volume effect on a spiral CT scan.

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  • 20. 

    During which of the following CT exams is misregistration artefact most likely to occur:

    • A.

      Brain

    • B.

      Pelvis

    • C.

      Neck

    • D.

      Abdomen

    Correct Answer
    D. Abdomen
    Explanation
    Misregistration artifact is most likely to occur during CT exams of the abdomen. Misregistration artifact refers to a type of image distortion where there is misalignment or mismatch of different image slices. This can happen due to various factors such as patient movement, breathing, or inadequate breath-hold technique. Since the abdomen area is more prone to motion artifacts, especially due to the presence of organs like the liver and bowel, it increases the likelihood of misregistration artifact occurring during CT exams of the abdomen.

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  • 21. 

    Which of the following mathematical functions may be used to quantify the spatial resolution of a CT scanner? 1 PSF 2 MTF 3 LSF

    • A.

      2 only

    • B.

      1 and 2

    • C.

      2 and 3

    • D.

      1, 2, and 3

    Correct Answer
    D. 1, 2, and 3
    Explanation
    PSF point spread function, MTF Modulation transfer function, and LSF line spread function all are used to quantify the spatial resolution of a CT scanner

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  • 22. 

    The matrix size describes which of the following:

    • A.

      Aperture size used during data acquistion

    • B.

      Number of pixels used to display an image

    • C.

      Relationship between the FOV and algorithm

    • D.

      None of the above

    Correct Answer
    B. Number of pixels used to display an image
    Explanation
    The matrix size refers to the number of pixels used to display an image. In digital imaging, an image is divided into a grid of pixels, and the matrix size determines the resolution and level of detail in the displayed image. A larger matrix size means more pixels are used, resulting in a higher resolution image with finer details. Conversely, a smaller matrix size would result in a lower resolution image with less detail. Therefore, the matrix size directly affects the quality and clarity of the displayed image.

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  • 23. 

    Which of the following is not an iterative method of CT image reconstruction

    • A.

      Point by point correction

    • B.

      Fourier transform

    • C.

      Simultaneous reconstruction

    • D.

      Ray by ray correction

    Correct Answer
    B. Fourier transform
    Explanation
    Fourier is a analytical method

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  • 24. 

    In the following formula used to calculate the linear attenuation coefficient, I=Ioe -ux, the symbol Io identifies

    • A.

      Eulers constant

    • B.

      Incident intensity

    • C.

      Absorber thickness

    • D.

      Transmitted intensity

    Correct Answer
    B. Incident intensity
    Explanation
    The symbol Io in the given formula represents the incident intensity. In physics, incident intensity refers to the initial intensity of a beam or wave before it interacts with any medium or object. In this formula, Io is used to calculate the linear attenuation coefficient, which represents the reduction in intensity as the beam or wave passes through an absorber. Therefore, Io is the initial intensity that is being attenuated.

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  • 25. 

    Which of the following would increase the noise of a CT image?

    • A.

      Increased MAS

    • B.

      Decreased aperture size

    • C.

      Decreased filtration

    • D.

      Decreased matrix size

    Correct Answer
    B. Decreased aperture size
    Explanation
    Decreasing the aperture size would increase the noise of a CT image. The aperture size refers to the size of the collimator, which controls the amount of radiation that reaches the detector. By decreasing the aperture size, less radiation is allowed to pass through, resulting in a lower signal-to-noise ratio. This leads to an increase in noise, making the image less clear and more grainy.

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  • 26. 

    The types of detectors used in CT include 1 gas 2 stimulable phosphor 3 scintillation crystal

    • A.

      1 only

    • B.

      3 only

    • C.

      1 and 3

    • D.

      2 and 3

    Correct Answer
    C. 1 and 3
    Explanation
    The correct answer is 1 and 3 because gas detectors and scintillation crystals are both types of detectors used in CT scans. Gas detectors are used to measure the ionizing radiation produced by the patient, while scintillation crystals are used to detect the radiation and convert it into light, which is then converted into an electrical signal for image formation. Stimulable phosphor is not a type of detector used in CT scans.

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  • 27. 

    Which of the following is used to archive CT images?

    • A.

      3.5 floppy disc

    • B.

      Magnetic tape

    • C.

      VHS tape

    • D.

      Magnetic optical disk

    Correct Answer
    D. Magnetic optical disk
    Explanation
    A magnetic optical disk is used to archive CT images. This type of disk combines magnetic and optical technologies to store and retrieve data. It provides a high storage capacity and allows for easy access and retrieval of the archived images. The magnetic component allows for fast writing and reading of data, while the optical component ensures long-term stability and durability of the stored information.

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  • 28. 

    Which of the following manipulations involve the use of image data?

    • A.

      Adjusting the width and level of the window setting

    • B.

      Decreasing the DFOV

    • C.

      Changing the algorithm selection

    • D.

      Increasing the matrix size

    Correct Answer
    A. Adjusting the width and level of the window setting
    Explanation
    Adjusting the width and level of the window setting involves the use of image data. The width and level of the window setting refer to the range of pixel values displayed on the image. By adjusting these settings, the contrast and brightness of the image can be modified, which directly involves manipulating the image data.

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  • 29. 

    Collimation of the CT X-ray beam occurs 1 At the x-ray tube regulating the thickness 2 Just prior to the PT controlling the volume of tissue irradiated 3 Prior to the detectors limiting the amount of scatter radiation absorbed

    • A.

      1 only

    • B.

      1 and 2

    • C.

      1 and 3

    • D.

      1, 2, and 3

    Correct Answer
    C. 1 and 3
    Explanation
    Collimation of the CT X-ray beam occurs at the x-ray tube, regulating the thickness, and also prior to the detectors, limiting the amount of scatter radiation absorbed. This means that the beam is controlled both at the source and at the detectors to ensure that the desired thickness and amount of scatter radiation are achieved. Controlling the thickness at the x-ray tube helps to focus the beam and reduce unnecessary exposure to surrounding tissues, while limiting scatter radiation at the detectors helps to improve image quality and reduce noise.

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  • 30. 

    An average CT number value for bone is?

    • A.

      + 100 HU

    • B.

      + 500 HU

    • C.

      +1000 HU

    • D.

      +3000 HU

    Correct Answer
    C. +1000 HU
    Explanation
    The average CT number value for bone is +1000 HU. CT numbers, also known as Hounsfield units (HU), are used to measure the density of tissues in a CT scan. Bone has a high density due to its mineral composition, which results in a CT number of +1000 HU. This high CT number allows for clear visualization and differentiation of bone from other tissues in a CT image.

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  • 31. 

    The major disadvantage of the back projection method of image reconstruction is the appearance of the

    • A.

      Partial volume effect

    • B.

      Ring artifact

    • C.

      Gibbs phenomenon

    • D.

      Star artifact

    Correct Answer
    D. Star artifact
    Explanation
    The major disadvantage of the back projection method of image reconstruction is the appearance of star artifacts. Star artifacts are unwanted bright lines or streaks that radiate from high-contrast objects in the image. They are caused by the back projection algorithm incorrectly assigning high values to certain pixels, resulting in exaggerated brightness and streaking. This can lead to a distorted and less accurate representation of the original image.

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  • 32. 

    Which of the following is used in gas ionization CT detectors?

    • A.

      Neon

    • B.

      Xenon

    • C.

      Helium

    • D.

      Nitrogen

    Correct Answer
    B. Xenon
    Explanation
    Xenon is used in gas ionization CT detectors because it is a noble gas that is easily ionized by radiation. When radiation passes through the gas-filled detector, it ionizes the xenon atoms, creating an electrical signal that can be detected and used to create an image. Xenon is preferred over other gases like neon, helium, and nitrogen because it has a higher atomic number, which results in better image quality and higher sensitivity to radiation.

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  • 33. 

    The most effective method of reducing involuntary motion on a CT image is through:

    • A.

      Immobilization

    • B.

      Thorough explanation of the exam

    • C.

      Reduce scan times

    • D.

      Physical restraints

    Correct Answer
    C. Reduce scan times
    Explanation
    Reducing the scan times is the most effective method of reducing involuntary motion on a CT image. When the scan time is reduced, there is less chance for the patient to move during the scan, resulting in clearer and more accurate images. Immobilization techniques and physical restraints may also help, but they can be uncomfortable for the patient and may not completely eliminate motion. Thorough explanation of the exam can help the patient understand the importance of staying still, but it may not always prevent involuntary motion. Therefore, reducing the scan times is the best approach to minimize motion artifacts on CT images.

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  • 34. 

    Which of the following CT film formats is the largest image for the viewer on the 14x17 film?

    • A.

      4:1

    • B.

      6:1

    • C.

      12:1

    • D.

      20:1

    Correct Answer
    A. 4:1
    Explanation
    The 4:1 CT film format is the largest image for the viewer on the 14x17 film. This means that the image on the film is four times larger than the actual size. This format allows for a more detailed and magnified view of the scanned area, making it easier for the viewer to analyze and interpret the images.

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  • 35. 

    Which of the following matrices provides the greatest spatial resolution?

    • A.

      256x256

    • B.

      320x320

    • C.

      512x512

    • D.

      1024x1024

    Correct Answer
    D. 1024x1024
    Explanation
    The matrix with the greatest spatial resolution is the one with the highest number of pixels, which in this case is 1024x1024. A higher number of pixels allows for more detail to be captured and displayed in the image, resulting in a higher spatial resolution.

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  • 36. 

    The data acquisition system of a CT scanner 1 Measures transmitted intensity 2 Converts transmission data into a digital signal 3 Sends the digital information to the central processing unit

    • A.

      1 only

    • B.

      2 only

    • C.

      1 and 3

    • D.

      1, 2, and 3

    Correct Answer
    D. 1, 2, and 3
    Explanation
    The data acquisition system of a CT scanner measures the transmitted intensity of the X-ray beam as it passes through the patient's body (1). It then converts this transmission data into a digital signal (2) and sends the digital information to the central processing unit (3). This allows for the creation of detailed cross-sectional images of the patient's anatomy.

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  • 37. 

    Which of the following terms is used to describe a set of rules for solving a mathematical problem?

    • A.

      Reconstruction

    • B.

      Algorithm

    • C.

      Function

    • D.

      Array

    Correct Answer
    B. Algorithm
    Explanation
    An algorithm is a term used to describe a set of rules for solving a mathematical problem. It is a step-by-step procedure or a set of instructions that outlines the exact sequence of operations to be followed in order to solve a problem or perform a task. Algorithms are commonly used in mathematics and computer science to solve complex problems efficiently and accurately.

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  • 38. 

    The contrast resolution of a CT scanner is not related to which of the following:

    • A.

      Focal spot size

    • B.

      Section width

    • C.

      Reconstruction algorithm

    • D.

      Signal to noise ratio

    Correct Answer
    A. Focal spot size
    Explanation
    The contrast resolution of a CT scanner refers to its ability to distinguish between different shades of gray in an image. It is determined by factors such as section width, reconstruction algorithm, and signal to noise ratio. However, the focal spot size of a CT scanner does not directly affect the contrast resolution. The focal spot size refers to the size of the X-ray beam that is emitted by the scanner, and while it may have an impact on image sharpness, it does not play a role in determining the ability to differentiate between different shades of gray.

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  • 39. 

    The spatial resolution of a CT scanner is usually expressed as:

    • A.

      HU

    • B.

      Lp/cm

    • C.

      U

    • D.

      Hz

    Correct Answer
    B. Lp/cm
    Explanation
    The spatial resolution of a CT scanner is usually expressed as lp/cm, which stands for line pairs per centimeter. This measurement indicates the ability of the scanner to distinguish between closely spaced lines or structures in an image. A higher lp/cm value indicates a higher spatial resolution, meaning that the scanner can capture more detailed images with better clarity and accuracy.

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  • 40. 

    When a SFOV is chosen, the CT technologist is controlling:

    • A.

      The diameter of acquisition/reconstruction for the anatomic section

    • B.

      The number of activated detectors within the array

    • C.

      The correction factors for the specific area of anatomic interest

    • D.

      All of the above

    Correct Answer
    D. All of the above
    Explanation
    When a SFOV (Single Field of View) is chosen, the CT technologist has control over the diameter of acquisition/reconstruction for the anatomic section. This means they can adjust the size of the area being scanned and reconstructed. They also have control over the number of activated detectors within the array, which determines the level of detail and resolution of the images obtained. Additionally, the technologist can apply correction factors specific to the area of anatomic interest, such as adjusting for patient size or metal artifacts. Therefore, the correct answer is "all of the above."

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  • 41. 

    A CT image is displayed in a window with a level of +200 and a width of 1000. Which of the following statements is correct?

    • A.

      Pixels with values between +200 and -1000 HU appear white

    • B.

      Pixels with values greater than +200 HU appear black

    • C.

      Pixels with values -300 and + 700 HU units are assigned shades of gray

    • D.

      Pixels with values between -1200 and +1200 HU units are assigned shades of gray

    Correct Answer
    C. Pixels with values -300 and + 700 HU units are assigned shades of gray
    Explanation
    In a CT image, the window level determines the midpoint of the gray scale, while the window width determines the range of values that will be displayed. In this case, the window level is +200, meaning that any pixel with a value equal to or greater than +200 will be displayed as a shade of gray. Similarly, the window width is 1000, so any pixel with a value between -300 and +700 will also be displayed as a shade of gray. Therefore, the correct statement is that pixels with values -300 and +700 HU units are assigned shades of gray.

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  • 42. 

    The dimension of a voxel may be decreased by which of the following?

    • A.

      Decreasing the section width

    • B.

      Decreasing the matrix size

    • C.

      Increasing the section width

    • D.

      Increasing the DFOV

    Correct Answer
    A. Decreasing the section width
    Explanation
    Decreasing the section width can decrease the dimension of a voxel. The section width refers to the thickness of each image slice in a three-dimensional volume. By decreasing the section width, the thickness of each slice is reduced, resulting in smaller voxels. Voxels are the three-dimensional pixels that make up the image volume, and their size is directly influenced by the section width. Therefore, decreasing the section width will decrease the dimension of a voxel.

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  • 43. 

    A CT image of a homogeneous material contains variations in CT number from pixel to pixel. This image has:

    • A.

      High contrast

    • B.

      Sensitivity

    • C.

      Definition

    • D.

      Noise

    Correct Answer
    D. Noise
    Explanation
    A CT image of a homogeneous material contains variations in CT number from pixel to pixel, indicating the presence of noise. Noise refers to random variations in pixel values that can degrade image quality and make it difficult to distinguish fine details. In this case, the variations in CT numbers suggest that the image has noise present.

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  • 44. 

    Which of the following are correct statements concerning the translate rotate mode of CT Data acquisition? 1 Circular detector arrays of 360 are used 2 Data are collected only during translation 3 The method was used in first and second-generation Scanners

    • A.

      2 only

    • B.

      3 only

    • C.

      1 and 2

    • D.

      2 and 3

    Correct Answer
    D. 2 and 3
    Explanation
    In the translate rotate mode of CT Data acquisition, data are collected only during translation (statement 2) and the method was used in first and second-generation Scanners (statement 3). This means that statement 1, which states that circular detector arrays of 360 are used, is incorrect. Therefore, the correct statements are 2 and 3.

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  • 45. 

    As the attenuation of a volume of tissue decreases, the transmitted intensity of a CT beam.

    • A.

      Increases

    • B.

      Remains unchanged

    • C.

      Decreases

    • D.

      Increases to a peak value and then rapidly decreases

    Correct Answer
    A. Increases
    Explanation
    As the attenuation of a volume of tissue decreases, it means that the tissue is becoming less dense or less opaque to the CT beam. This allows more of the beam to pass through the tissue, resulting in an increase in the transmitted intensity. Therefore, the correct answer is increases.

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  • 46. 

    Which of the following statements comparing the efficiency of scintillation and gas ionization detectors is correct?

    • A.

      Both have approximately the same capture efficiency

    • B.

      The scintillation detector has a higher capture efficiency

    • C.

      Unlike the scintillation detector, the gas ionization detector has a problem with after glow

    • D.

      Gas ionization detectors have a higher conversion efficiency

    Correct Answer
    B. The scintillation detector has a higher capture efficiency
    Explanation
    The correct answer states that the scintillation detector has a higher capture efficiency. This means that the scintillation detector is more effective at capturing and detecting radiation compared to gas ionization detectors.

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  • 47. 

    Which of the following terms accurately describes the type of x-ray beam used in a third-generation CT scanner?

    • A.

      Pencil beam

    • B.

      Fan beam

    • C.

      Nutating beam

    • D.

      Electron beam

    Correct Answer
    B. Fan beam
    Explanation
    A fan beam accurately describes the type of x-ray beam used in a third-generation CT scanner. In this type of scanner, the x-ray beam is shaped like a fan and is emitted from a rotating source. This beam is then detected by a stationary array of detectors, allowing for the generation of detailed cross-sectional images of the body. The fan beam is able to cover a wider area compared to a pencil beam, nutating beam, or electron beam, making it suitable for CT scanning.

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  • 48. 

    The phantom image is used to test which of the following image quality factors of a CT scanner.

    • A.

      Spatial resolution

    • B.

      Noise

    • C.

      Linearity

    • D.

      Contrast resolution

    Correct Answer
    A. Spatial resolution
    Explanation
    The phantom image is used to test spatial resolution of a CT scanner. Spatial resolution refers to the ability of the scanner to distinguish between small objects or details in an image. By using a phantom image, which contains small structures or objects with known dimensions, the spatial resolution of the CT scanner can be evaluated. This helps in determining how well the scanner can capture and display fine details in the images it produces.

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  • 49. 

    The adjacent pixels are measured to have a difference of 1 HU unit. This amounts to a tissue density difference of approximately.

    • A.

      0.1%

    • B.

      1.0%

    • C.

      10%

    • D.

      25%

    Correct Answer
    A. 0.1%
    Explanation
    The adjacent pixels having a difference of 1 HU unit indicates a very small difference in tissue density. Therefore, the tissue density difference is approximately 0.1%.

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  • 50. 

    The intensity of the CT x-ray beam can be increased by:

    • A.

      Increasing filtration

    • B.

      Decreasing collimation

    • C.

      Decreasing applied tube voltage

    • D.

      Increasing collimation

    Correct Answer
    B. Decreasing collimation
    Explanation
    Decreasing collimation refers to narrowing the x-ray beam, which results in a higher intensity of the beam. This is because when the collimation is decreased, the x-ray beam becomes more focused and concentrated, leading to a higher concentration of x-ray photons. As a result, the intensity of the CT x-ray beam increases, allowing for better image quality and more accurate diagnosis.

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Quiz Review Timeline +

Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.

  • Current Version
  • Mar 22, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Oct 06, 2008
    Quiz Created by
    Leclark
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