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Quizzes > Health & Medicine > Human Anatomy & Medicine

Ready to Ace Your Cat Scan Registry Review Quiz?

Boost Your Skills: CT Registry Practice Test & Computed Tomography Review

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration showing CT scan slices and quiz items on teal background for CT registry practice questions

This Free Cat Scan Registry Review Quiz helps you check your CT registry prep and find gaps before the exam. Work through realistic questions on core CT concepts to build speed and confidence. Start here, or try the full practice test if you want a longer run.

What does CT stand for?
Cross-sectional Tomography
Computed Tomography
Contrast Tomography
Computed Tachygraphy
CT stands for Computed Tomography, which uses computer processing of x-ray data to produce cross-sectional images. It is the standard term used worldwide in medical imaging. The name reflects the combination of data computation and tomographic slicing.
Which unit is used to express attenuation values in CT images?
Gray units
Sievert units
Hounsfield units
Tesla units
CT attenuation values are measured in Hounsfield units (HU), which normalize tissue density relative to water. Water is defined as 0 HU and air as -1000 HU. This scale allows consistent interpretation of tissue contrast.
What is the approximate Hounsfield unit value of water?
1000 HU
100 HU
0 HU
-1000 HU
Water is assigned a value of 0 HU on the Hounsfield scale and serves as the reference for CT attenuation. This standardization helps compare densities of other tissues. Accurate calibration ensures stability of measurements.
Which anatomical plane divides the body into anterior and posterior sections?
Sagittal
Axial
Oblique
Coronal
The coronal plane runs vertically, dividing the body into front (anterior) and back (posterior) portions. This orientation is often used in reformatted CT images. It complements axial and sagittal views for full anatomical assessment.
What artifact appears as dark streaks near dense metal objects in CT images?
Beam hardening
Motion artifact
Partial volume
Ring artifact
Beam hardening occurs when lower-energy photons are absorbed by dense objects like metal, causing streaks. It results in dark bands or cupping artifacts near metal. Correction algorithms or filters can reduce its impact.
Which phase of intravenous contrast enhancement is typically acquired around 60-70 seconds post-injection for abdominal imaging?
Arterial phase
Portal venous phase
Delayed phase
Noncontrast phase
The portal venous phase occurs about 60-70 seconds after contrast injection, optimizing liver parenchyma and portal vein enhancement. It is standard for abdominal CT to evaluate lesions. Proper timing ensures adequate opacification of target structures.
What is the typical slice thickness for a routine adult head CT scan?
1 mm
0.5 mm
10 mm
5 mm
A 5 mm slice thickness is commonly used for routine head CT protocols as a balance between spatial resolution and scan time. Thicker slices reduce noise but may miss small lesions. Many protocols allow for reconstructions at thinner slices if needed.
Which window width setting is most appropriate for evaluating lung parenchyma on CT?
80 - 120 HU
300 - 350 HU
4000 - 4500 HU
1500 - 2000 HU
A wide window width of around 1500 - 2000 HU is used for lung parenchyma to display both air-filled and soft-tissue structures. It allows visualization of subtle lung pathology. Narrower windows would obscure low-density details.
Which contrast agent type is most commonly used for CT imaging?
Gadolinium-based
Barium sulfate
Non-ionic, iodinated
Air
Non-ionic, iodinated contrast agents are widely used in CT for their favorable safety profile and high atomic number of iodine. They enhance vascular and soft tissue contrast. Barium is used for GI studies, not vascular CT.
What is the primary purpose of a CT scout (localizer) image?
To assess contrast distribution
To measure patient dose
To evaluate bone windows
To localize the scan range
A CT scout image is a quick survey radiograph used to plan the subsequent axial or helical scan range. It ensures the region of interest is correctly included. It also helps position the patient table accurately.
Which of the following best describes the axial plane in CT imaging?
Vertical slices dividing left and right
Vertical slices dividing front and back
Horizontal slices from head to toe
Diagonal oblique slices
The axial plane consists of horizontal slices parallel to the floor when the patient is supine, extending from head to toe. This is the primary acquisition plane in CT. It is sometimes called the transverse plane.
Which structure appears darkest on noncontrast CT of the chest?
Lungs
Heart
Liver
Bone
Air within the lungs has very low attenuation (~ -1000 HU), making the lung fields appear darkest. Soft tissues and bone attenuate more x-rays and appear brighter. Recognizing this contrast is crucial for chest imaging.
What parameter is described by the term 'pitch' in helical CT scanning?
Reconstruction interval divided by slice thickness
Table movement per rotation divided by slice thickness
Frame rate per second
Tube current times voltage
Pitch is calculated as table movement per gantry rotation divided by the total nominal slice thickness. It determines coverage speed and influences radiation dose and image resolution. A higher pitch yields faster scans at lower dose but may decrease image quality.
Which artifact is most commonly caused by patient movement during the scan?
Stair-step artifact
Motion artifact
Beam hardening
Ring artifact
Motion artifact appears as blurring or ghosting of structures when the patient moves during image acquisition. It degrades image quality and can obscure pathology. Techniques like faster scan times and patient instructions help minimize it.
Which term describes combining multiple detector rows to form images in MDCT?
Multidetector acquisition
Cone-beam CT
Dual-energy scanning
Tomosynthesis
Multidetector acquisition refers to using multiple rows of detectors in spiral CT to acquire volumetric data rapidly. This allows thinner slices and faster scanning. It has become standard in modern CT scanners.
Which reconstruction technique can reduce image noise and allow lower radiation dose compared to filtered back projection?
Analytic reconstruction
Iterative reconstruction
Fourier reconstruction
Filtered back projection
Iterative reconstruction algorithms model the data acquisition process and statistical noise to produce images with lower noise at reduced dose. Compared to filtered back projection, it can maintain image quality at lower mAs. Many vendors now include iterative methods.
What is the function of a bowtie filter in CT imaging?
It enhances contrast media distribution
It reconstructs images at different angles
It shapes the x-ray beam to reduce dose at the periphery
It rotates to move the patient table
A bowtie filter is placed between the x-ray source and patient to attenuate the beam more at the edges, matching body shape. This reduces the dose to the periphery and evens out detector exposure. It also decreases scatter and improves image uniformity.
Which parameter primarily affects spatial resolution in CT imaging?
Focal spot size
mAs
Pitch
kVp
The focal spot size determines the sharpness of the x-ray beam profile, directly influencing spatial resolution. A smaller focal spot yields higher resolution but can limit tube loading. Other factors like detector size also play a role.
What does DLP stand for in CT dose metrics?
Dynamic linear programming
Dose level protocol
Dose length product
Dose limit parameter
Dose length product (DLP) represents the CTDIvol multiplied by the scan length, providing an estimate of total radiation exposure. It is used to compare dose across protocols. Converting DLP to effective dose uses region-specific conversion factors.
Which technique modulates tube current in real time based on patient attenuation?
Dynamic kVp modulation
Fixed mAs protocol
Automatic exposure control
Constant current scanning
Automatic exposure control (AEC) adjusts tube current during scanning to maintain consistent image quality while reducing dose. It uses feedback from scout images or real-time detectors. AEC can modulate angularly and longitudinally.
At what delay time is the arterial phase typically acquired during a contrast-enhanced CT of the abdomen?
90 - 120 seconds
60 - 70 seconds
5 - 10 seconds
20 - 30 seconds
The arterial phase of abdominal CT is usually imaged around 20 - 30 seconds after IV contrast injection to visualize arterial anatomy. This timing highlights hypervascular lesions and vascular structures. Subsequent phases follow at later intervals.
Which reconstruction interval yields overlapping images for better multiplanar reformats?
Twice the slice thickness
Less than slice thickness
Ten times the slice thickness
Equal to slice thickness
Using a reconstruction interval smaller than the slice thickness creates overlapping images, improving the quality of multiplanar reformats. Overlapping reduces staircase artifacts in reformatted planes. It increases the number of images but enhances diagnostic detail.
Which artifact is caused by incorrect calibration of detector elements in CT scanners?
Beam hardening
Motion artifact
Streak artifact
Ring artifact
Ring artifacts appear as concentric circles on images when one or more detector channels are miscalibrated or defective. Calibration and corrections can minimize this issue. Regular quality control detects faulty detectors promptly.
What does isotropic voxel resolution mean in CT imaging?
Variable slice thickness
Non-overlapping slices
High contrast resolution
Equal dimensions in all three axes
Isotropic voxels have equal width, height, and depth, enabling high-quality multiplanar reformats without distortion. This is a benefit of thin-slice MDCT acquisitions. Non-isotropic voxels can cause stair-step artifacts.
Which CT technique is primarily used to evaluate coronary artery stenosis?
ECG-gated CT angiography
CT perfusion
Dual-energy CT
Noncontrast CT
ECG-gated CT angiography synchronizes image acquisition with the cardiac cycle to minimize motion and accurately assess coronary arteries. Prospective or retrospective gating options exist. It is standard for noninvasive coronary evaluation.
Which protocol modification can reduce radiation dose for pediatric CT exams?
Use thicker reconstruction slice only
Increase pitch beyond 3
Lower kVp and mAs
Omit scouting image
Lowering kVp and mAs for pediatric patients reduces radiation dose while maintaining diagnostic image quality, due to smaller body habitus. Automatic exposure control can further optimize technique. Pediatric protocols should always be tailored to size.
What is the advantage of using a thin slice thickness in CT imaging?
Improved spatial resolution and better MPRs
Reduced image data size
Lower noise levels
Shorter reconstruction time
Thin slices enhance spatial resolution and yield higher-quality multiplanar reformats by reducing partial volume effects. They allow detection of small lesions. However, they increase image noise and data storage needs.
Which CT metric indicates the average absorbed dose within the scan volume?
DLP
Effective dose
CTDIvol
Dose sum index
CTDIvol (CT dose index volume) represents the average dose within the scanned slice volume, accounting for pitch. It is displayed on CT consoles. It allows comparison of protocols for dose optimization.
What is dual-energy CT capable of differentiating based on material composition?
Photon energy levels only
Iodine vs calcium vs soft tissue
Magnetic susceptibility
Acoustic impedance
Dual-energy CT uses two distinct x-ray spectra to differentiate materials by their energy-dependent attenuation, enabling separation of iodine, calcium, and soft tissue. It can produce material-specific maps and virtual non-contrast images. This improves lesion characterization.
Which CT perfusion parameter measures blood flow through tissue per unit mass?
Blood volume (BV)
Mean transit time (MTT)
Time to peak (TTP)
Cerebral blood flow (CBF)
Cerebral blood flow (CBF) quantifies the volume of blood passing through 100 g of tissue per minute in CT perfusion studies. It is critical for assessing ischemic penumbra. Other parameters include MTT, BV, and TTP.
What artifact arises from nonlinear partial volume averaging at high-contrast edges?
Blooming artifact
Aliasing
Gibbs artifact
Stair-step artifact
Stair-step artifacts appear in curved structures when using thick slices and non-overlapping reconstructions, causing step-like edges. Overlapping thin slices can reduce this. It is related to partial volume effects.
In CT angiography, what is the purpose of bolus tracking?
To evaluate contrast toxicity
To monitor patient vital signs
To measure injection rate
To synchronize scan start with optimal vascular enhancement
Bolus tracking monitors contrast arrival in a target vessel or region by performing low-dose scans, triggering the diagnostic scan once a threshold HU is reached. This ensures optimal arterial opacification. It adapts to patient circulation variability.
Which CT detector type uses scintillators coupled to photodiodes?
Solid-state detectors
Charge-coupled devices
Gas ionization detectors
Photomultiplier tubes
Modern multi-detector CT scanners use solid-state detectors where a scintillator converts x-rays to light, which photodiodes then transduce into electrical signals. They offer high efficiency and speed. Gas detectors were used in early CT systems.
What is the effect of increasing pitch while keeping other parameters constant?
Better low-contrast resolution
No change in image noise
Increased dose and reduced table speed
Reduced dose and increased table speed
Increasing pitch moves the patient table faster relative to gantry rotation, reducing radiation dose but potentially increasing image noise and reducing resolution. It speeds scan time. Dose modulation must compensate if image quality is to be maintained.
Which advanced reconstruction method models x-ray physics for artifact reduction?
Fourier back projection
Model-based iterative reconstruction
Filtered back projection
Analytic reconstruction
Model-based iterative reconstruction (MBIR) incorporates detailed system and noise models to iteratively refine images, reducing artifacts and noise. It allows significant dose reduction. MBIR is computationally intensive but yields superior image quality.
In CT fluoroscopy, what is the main advantage over conventional fluoroscopy?
Better spatial resolution than CT
Lower radiation dose
Real-time cross-sectional imaging
No need for contrast
CT fluoroscopy provides continuous, near real-time cross-sectional images during interventions, improving needle guidance. It combines CT's spatial resolution with dynamic feedback. However, it often involves higher dose rates than standard CT.
What does k-edge imaging in dual-energy CT exploit?
Abrupt change in attenuation at specific photon energies
Patient respiration
Detector crystal size
Contrast injection rate
K-edge imaging uses energies just above and below the k-shell absorption edge of elements like iodine to enhance contrast conspicuity. Dual-energy CT acquisitions capture these differences for material decomposition. It improves detection of contrast agents.
Which technique can correct beam hardening artifacts in CT?
Pre-hardening filter and software correction
Using higher pitch
Increasing kVp only
Decreasing mAs
Beam hardening filters (like copper or aluminum) and software-based correction algorithms reduce low-energy photons before the patient and adjust for residual artifacts during reconstruction. Simply increasing kVp may lessen but not eliminate artifacts. Combined approaches yield the best results.
Which CT colonography technique helps reduce patient radiation dose?
High kVp, low mAs
Supine imaging only
Low-dose protocols with model-based reconstruction
Single-phase non-contrast only
Low-dose CT colonography protocols using reduced mAs combined with model-based iterative reconstruction maintain image quality while minimizing dose. Standard protocols include both supine and prone positions, but low-dose settings are key. Noncontrast is sufficient for polyp detection.
What parameter of CT detectors primarily affects noise performance?
Reconstruction kernel
Scan field of view
Detector pitch
Detector quantum efficiency
Detector quantum efficiency (DQE) measures how effectively detectors convert x-ray photons into signal. Higher DQE reduces noise and improves image quality at lower dose. It is a key performance metric for CT systems.
In photon-counting CT, what is the main advantage over energy-integrating detectors?
Improved energy discrimination and spatial resolution
Lower spatial resolution
Higher dose requirements
Simpler detector design
Photon-counting detectors count individual x-ray photons and record their energy, providing better spectral separation and higher spatial resolution compared to energy-integrating detectors. This leads to improved material characterization and lower noise. It also enables dose reduction.
What is Monte Carlo simulation used for in CT dosimetry?
Detector calibration
Contrast timing optimization
Real-time image reconstruction
Accurate modeling of x-ray transport and patient dose
Monte Carlo simulation uses probabilistic models to simulate photon interactions in tissue and CT scanners, providing highly accurate estimates of patient dose distribution. It accounts for complex geometries and spectra. It is considered the gold standard in dosimetry research.
Which deep learning application is emerging in CT reconstruction?
Manual segmentation only
AI-based iterative reconstruction for noise reduction
Contrast injection automation
Bowtie filter design
Deep learning-based reconstruction algorithms leverage neural networks trained on high-quality images to denoise and enhance CT scans at lower dose. These AI methods can outperform traditional iterative techniques in speed and image quality. They represent a major shift in CT technology.
What is the purpose of k-edge subtraction imaging in dual-energy CT?
To measure tissue perfusion only
To correct motion artifacts
To isolate and visualize contrast agent distribution
To assess electrical impedance
K-edge subtraction imaging exploits the sudden increase in attenuation at the k-edge energy of contrast materials (like iodine) to subtract background and highlight agent distribution. This technique enhances detection of contrast-enhanced tissues. It is useful in vascular and perfusion imaging.
In advanced dose management, what does organ-based tube current modulation do?
Reduces exposure to radiosensitive organs by modulating tube current
Increases overall scan speed
Switches kVp mid-scan
Enhances contrast resolution globally
Organ-based tube current modulation lowers tube current when the x-ray tube passes over radiosensitive organs (e.g., breast, eyes), reducing dose to those regions. It adapts tube output dynamically while maintaining diagnostic quality elsewhere. This is a key dose-reduction strategy.
Which material decomposition algorithm is used in dual-layer detector CT?
Photon flux estimation
Iterative beam hardening correction
Spectral-based material decomposition
Filtered back projection
Dual-layer detector CT captures low- and high-energy data simultaneously, enabling spectral-based material decomposition to distinguish materials based on energy-dependent attenuation. It generates virtual monoenergetic images and material-specific maps. This enhances tissue characterization.
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Study Outcomes

  1. Understand Core CT Principles -

    Grasp the essential concepts of computed tomography registry review, including scanner technology, image acquisition parameters, and radiation safety guidelines.

  2. Analyze Exam-Style Questions -

    Break down CT registry practice test items to identify key terms and apply test-taking strategies for improved accuracy on the cat scan registry review.

  3. Apply Image Interpretation Skills -

    Interpret cross-sectional CT images to distinguish normal anatomy from common pathologies in preparation for your ct registry exam practice tests.

  4. Differentiate Protocols and Techniques -

    Compare various scanning protocols, contrast administration methods, and patient positioning to optimize outcomes across computed tomography registry review scenarios.

  5. Identify Radiation Safety Measures -

    Recognize and implement best practices for minimizing radiation exposure while maintaining diagnostic image quality in practice CT registry questions.

  6. Enhance Confidence and Readiness -

    Build test-taking confidence by simulating real-world quiz conditions and tracking performance to focus on areas needing improvement in the cat scan registry review.

Cheat Sheet

  1. CT Physics and Hounsfield Units -

    Review the fundamentals of X-ray attenuation and image formation, including the Hounsfield Unit (HU) formula: HU = 1000·(μ_tissue − μ_water)/μ_water. Remember "Water = 0, Air = −1000, Bone = +1000" as a simple mnemonic for windowing. Understanding filtered back projection versus iterative reconstruction (AAPM guidelines) boosts image quality interpretation.

  2. Radiation Dose Management (ALARA) -

    Master dose indices like CTDIvol and DLP and apply the ALARA principle to minimize patient exposure (source: ACR Dose Index Registry). Use automatic tube current modulation, optimize kVp/mA settings, and implement iterative reconstruction techniques to reduce dose while preserving diagnostic quality. Tracking dose trends over time ensures compliance and patient safety.

  3. Contrast Media Protocols and Phases -

    Familiarize yourself with iodine-based contrast agents, injection rates (e.g., 4 - 5 mL/s), and timing for arterial, portal venous, and delayed phases. Use bolus tracking with a threshold of 150 HU in the aorta for optimal phase capture (RSNA recommendations). A clear protocol chart helps standardize timing and improves lesion conspicuity.

  4. Cross-Sectional Anatomy and Windowing -

    Know normal HU values for key tissues: fat (−100 HU), soft tissue (20 - 70 HU), and fluid (0 HU). Adjust window width/level - e.g., brain WW 80 WL 40, lung WW 1500 WL −600 - to highlight specific anatomy (source: Radiological Society of North America). Correlate axial slices with organ landmarks to sharpen pathology recognition.

  5. Quality Control and Artifact Reduction -

    Identify and mitigate common artifacts such as beam hardening, motion, and streak artifacts by ensuring proper calibration and patient positioning (ACR CT Quality Control manual). Implement breath-hold instructions and gantry tilt adjustments to reduce motion blur. Regular phantom testing and protocol reviews maintain image consistency and registry readiness.

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