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RSC 2104
Test1 prep
| Question | Answer |
|---|---|
| 1st generation CT scanners used to take __-__ minutes per slice. | 3-5 |
| 2nd generation CT scanners took __seconds for a single slice. | 20 seconds |
| 3rd generation scanners have approximately __ detectors. | >750 |
| Most current CT scanners are ___ generation configurations. | 3rd |
| 3rd gen configurations: I. Helical CT, single slice CT II. Multi slice detectors III. (Fake answer) IV. Volume CT (VCT) V. Flat Panel CT (FP-CT) | I, II, IV, V |
| 4th gen scanners yield a ___ pt dose per scan than previous generations. | higher |
| 5th gen scanners have improved ___ resolution. | temporal |
| 6th gen scanners have improved ___ resolution for ___ structures such as the heart. | I. temporal II. moving |
| Slice thickness adds volume dimension called the ___. | voxel |
| Defined as a relative comparison of XR attenuation of a voxel of tissue with an equal volume of water. | CT number (hounsfield unit) |
| The hounsfield unit for water: | zero |
| The EfD of a CXR is __ mSv, while the EfD of a Chest CT is __ mSv. | I. 0.08 mSv II. 8.0 mSv |
| positive CT numbers represent tissues that are ___ than water. | denser |
| CT number scale ranges from __ to __. | I. -1000 II. +1000 |
| ___ determines the number of shades of gray that can be assigned to that pixel. | bit depth |
| 3 major System components of CT: | I. Computer console II. Operator console III. Gantry and Table |
| 4 CT computer functions: 1. acquisition 2. reconstruction 3. storage 4. display 5. contrast administration | 1, 2, 3, 4 |
| The CT Gantry contains: 1. XR tube 2. Data acquisition system 3. 4. detector array | 1,2 , 4 |
| ___ scanners also house continuous slip ring and a high voltage generator. | helical |
| the gantry collects ___ measurements for image reconstruction. | attenuation |
| the detectors in the gantry function similarly to ___ in standard x ray. | image receptors |
| The opening within the center of the gantry: | aperture |
| the ___ is an accessory device used for head CT exams. | cradle |
| Area in which the technologist controls the scanner | operators console |
| 4 parameters controlled at the operators console: | 1. technique factors 2. slice thickness 3. table index 4. recon program |
| the brightness values of gray scale image correspond to pixels and ___ they represent: | CT numbers |
| The number that is related to the linear attenuation coefficient of the tissue within each voxel is: | CT number |
| All of the following affect the rad dose delivered during a CT scan except: 1. beam energy (kVp) 2. tube current (mA) 3. Section or slice thickness (collimation) 4. 3D recon | 4. 3D recon |
| All of the following may cause streak artifacts in a CT image except: 1. dental fillings 2. scar 3. pacemaker 4. artificial joints | 2. scars |
| The midpoint of the range of gray levels to be displayed on the monitor: | window level |
| Range of CT numbers used to map signals into shades of gray. controls contrast resolution of an image. | window width |
| Which of the following affect spatial resolution of a CT image? 1. focal spot size 2. slice thickness 3. FOV | 1, 2 |
| Describes the recon of the brightest pixels from 2D or 3D image data: 1. volume CT 2. maximum intensity projection 3. shaded surface display 4. volume rendering | |
| An image with a narrow window width has ___ shades of gray or high/short-scale contrast. | fewer |
| Ability to reformat image data into coronal, sagittal, or oblique body planes without additional rad to the pt: | multiplanar recon (MPR) |
| 4 Most common CT procedures: | 1. head 2. chest 3. abdomen 4. pelvis |
| CT is useful for head trauma and diagnosing ___ disorders | CNS |
| Interventional procedures common in CT: 1. Abscess drainage 2. tissue biopsy 3. embolism removal 4. Cyst aspiration 5. radiofrequency and cryoablations of tumors | 1, 2, 4, 5 |
| 5 CT image quality factors: | 1. spatial resolution 2. contrast resolution 3. temporal resolution 4. noise 5. artifacts |
| Which image quality factor is determined by the degree of blur on an image? | spatial resolution |
| Most significant geometric factor for spatial resolution: | detector aperture width |
| Scanning section thickness, display FOV, matrix, and recon algorithm all affect what CT image quality factor? | spatial resolution |
| What CT image quality factor is the ability to differentiate btw smal density differences in an image? | contrast resolution |
| CT contrast resolution can distinguish density differences of less than __%. | 0.5% |
| Slice thickness, recon algorithm, image display, and XRB energy all affect which image quality factor? | Contrast resolution |
| Ability of the CT system to freeze any motion of a scanned object: | Temporal resolution |
| What type of study best utilizes temporal resolution? | Cardiac studies |
| Factors that improve temporal resolution: 1. fewer detectors 2. gantry rotation time 3. dual source CT | 2, 3 |
| Random variation in photon detection: | quantum noise |
| Noise primarily affects what image quality factor? | spatial resolution |
| CT scan parameters that influence noise: 1. patient size 2. matrix size 3. XRB energy 4. scattered radiation 5. slice thickness 6. recon proram | 2, 3, 5,6 |
| streak artifacts are caused by ___. | metallic objects |
| Streak or shadow artifacts caused by Large tissue density differences in skull and brain interfaces: | beam hardening |
| IQ factors that the technologist can control: 1. patient factors 2. scan times 3. scan diameter (FOV) | 2, 3 |
| Special feature based on the principle that structures enhance at different rates after contrast administration: | dynamic scanning |
| Special feature where the gantry rotates continuously while the table moves through the aperture at the same time: | Spiral/Helical CT |
| Special feature useful for scanning uncooperative, combative, trauma, or peds pts: | Spiral/Helical CT |
| Isotropic viewing, greater anatomic coverage, multiphase studies, faster exam times, and improved spatial resolution are advantages to which special CT feature? | Multislice Spiral/Helical CT |
| Which special CT has 64 rows of elements in detector arrays and is used for cardiac imaging? | Volume CT (VCT) |
| Application of spiral CT that uses 3D imaging techniques: | CT Angiography (CTA) |
| postprocessing technique that creates realistic images of surface anatomy: | 3D imaging |
| Reconstructs brightest pixels from 2D or 3D image data, commonly used for CTA: | Maximum Intensity Projeciton |
| Provides 3D image of the surface of a structure, sets a threshold value for a particular CT number, and provides depth perception to the reconstructed image: | Shaded surface display |
| a 3D imaging technique that depicts the anatomic relationships between the vasculature and viscera; requires more powerful computers too recon the entire image at a reasonable speed: | volume rendering |
| The use of spiral CT with MPR to aid radiation dosimetrist in maximizing dose to the target and minimizing dose to normal tissues: | Radiation treatment planning |
| Scanner typically used in nuclear medicine: | PET Scanners |
| CTTs routinely perform daily test scans on ___ phantoms to measure the consistency of CT numbers. | water |
| The most common dose reporting method is the: | Dose Length Product (DLP) |
| 6 Factors that affect dose: | 1. beam energy 2. tube current 3. exposure time 4. slice thickness 5. object thickness 6. attenuation 7. pitch/ section spacing 8. mA modulation 9. pt centering 10. distance from tube to isocenter |
| CT demonstrates ___ better than MRI | bone |
Created by:
lipscombsomi