| Question | Answer |
| Creatinine | A waste product of metabolism found in the bloodstream & measured as an indicator of renal function. Normal range: .5-1.5 mg/dL |
| What does the peritoneal cavity contain? | Stomach, liver, gallbladder, spleen, ovaries, transverse colon, & most of the small bowel. |
| Analog signal | Continuous display of energy intensity, or radiation, as opposed to the discrete display of a digital signal. |
| Patient Dose | The dose is the amount of ionizing radiation absorbed by the patient per unit mass. |
| Name general signs & symptoms that a patient is going into shock. | 1. rapid breathing 2. tachycardia 3. hypotension 4. weak pulse 5. pallor 6. cyanosis 7. cold clammy skin |
| CT Colonography | Specialized CT evaluation of the large intestine used primarily for colon cancer screening.The large intestine is extended & scanned with thin-section CT. 2D & 3D models are constructed, including virtual endoscopic fly-through views. |
| What components are normally located in the gantry of a modern CT systems. | 1. x-ray tube 2. detectors 3. collimators (pre-patient & post-patient) |
| What system component is responsible for converting the digital signal into analog form? | D to A converter |
| Anode | Positive side of x-ray tube, containing the target. |
| ALARA | Acronym for as low as reasonably achievable, the cardinal principle of radiation dose reduction for all radiological procedures, including CT. |
| Display field of view (DFOV) | The diameter of the acquired attenuation data displayed across the image matrix. May also be referred to as the zoom factor or target view. |
| Aliasing Effect | Artifacts that appear on the CT image as fine lines. They occur when too few samples are acquired. Also called sampling artifacts. |
| What is effective dose? | The quantity of absorbed radiation dose based on the radiosensitivity of a particular tissue type. |
| What does DAC stand for? | Digital-to-Analog Convertor |
| Sample & hold (S/H) | Signal is sampled here 1st. |
| CT Dose index
(CTDI) | An approximate measure of the radiation dose received in a single CT section or slice. |
| CT Urogram | A comprehensive, multi-phasic CT evaluation of the urinary tract. Consists primarily of pre-contrast, post-contrast & delayed CT acquisitions through the kidneys, ureters, and bladder. It may also be commonly referred to as a CT-IVP. |
| CT scan of the pelvis should include what? | From the iliac crests to the pubic symphysis. |
| CT Simulation | The process of obtaining anatomic information with CT imaging that is used to calculate the beam arrangement for radiotherapy. |
| Multirow detector scanners employ what type of technology? | 3rd generation |
| Fourier transformation (FT) | a mathematical transformation to convert distance into spatial frequency. |
| What is SOLU-CORTEF? | A brand name for hydrocortisone, which is a type of corticosteroid. May be used during the treatment of anaphylactoid reacations to iodinated contrast materials. |
| CT Cystography | Specialized CT examination of the bladder whereby iodinated contrast material is administered directly under gravity into the bladder via
Foley catheter. |
| Uniform matrix array | Type of algorithm used for MSCT image reconstruction in which two sets of projection data acquired 360 degrees apart are used to form an image at a precise z-axis location. |
| Adaptive array | The type of MSCT detector array configured with the thinnest detectors at the center, surrounded by detectors of incrementally increasing widths along the a-axis. |
| Radiation exposure & its potentially harmful effects have a relationship that is termed __________. | Stochastic |
| Tungsten is used as the target material on the tube's anode because it has a ________ atomic # & a _______melting point. | high, high |
| What is the ACMP | Professional society of medical physicists. |
| What are 3 functions of PACS? | 1. Long term data storage 2. Digital distribution of images 3. Image display for the radiologist |
| ACMP | American College of Medical Physicists |
| Scatter radiation is caused by what? | Deflections from the original trajectory of an x-ray photon through the patient. |
| Scan field of view (SFOV) | A parameter that controls the diameter of the circular data acquisition field within the CT gantry as determined by the # of activated detectors along the x-y axis. May be referred to as calibration field. |
| Name 3 things the operator's console may include. | 1. monitor 2. keyboard 3. graphic input device |
| What device is used to measure the patient dose from a CT exam? | Ionization chamber |
| State 4 items that are true regarding the collection of CT data. | 1. Short scan times are more desirable. 2. The reconstruction process used to create the image occurs in the array processor. 3. To collect the complete set of CT data, x-rays must be passed through the body at many different angles. |
| Beam Width | The dimension of the primary beam in the longitudinal or z-axis as controlled by the pre-patient collimator. |
| Lipoma | A benign mass consisting of fat cells. |
| The reduction in intensity of an x-ray beam as it interacts with matter is termed what? | Attenuation |
| Contiguous images | CT images acquired with equal section thickness and reconstruction intervals. |
| Absorbed dose | The amount of x-ray energy absorbed in a unit of mass. It is measured in grays (Gy). |
| What technical factors has a direct effect on patient dose? | With no consideration of image quality, reductions in mA and/or scan time(seconds). |
| What type of information can be entered @ the CT console? | 1. Imaging parameters 2. Post processing techniques 3. Filming & archiving instructions |
| Algorithm | Mathematical filter applied to raw data during CT image reconstruction to remove blurring artifact inherent to back projection. May also be referred to as a kernel. |
| Attenuation coefficient | The value assigned to an object quantifying its ability to attenuate an x-ray beam. |
| What are 2 rights of the patient? | 1. Pt has the right to considerate & respectful care. 2. Pt has the right to refuse medical treatment. |
| What is the easiest way to increase the # of photons? | Increase the tube current or the scan time. |
| Moderate reactions to iodinated contrast agents include: | 1. mild bronchospasm 2. moderate to severe urticaria (hives) 3. vasovagal response 4. tachycardia from hypotension |
| Increased ___ will increase the likelihood that a given x-ray will penetrate a material. | kV |
| Beam Hardening | The phenomenon whereby low-energy phontons are absorbed as the x-ray beam passes through an object, resultin in an increase in the average photon energy of the beam. |
| Most of the commands from the technologist are received by the: | Operator's console |
| The primary goal of CT image reconstruction is to spatially distribute the attenuation data recorded by the _______ _______. | Detector Array |
| Multi-row detector CT scanners: | 1. The size of the detector arrays along the z-direction may be different. 2. The attenuation information from adjacent detector arrays may be added together to generate thicker slices. 3. All of the detector arrays may or may not be used. |
| How are spiral/helical CT exams obtained? | With the scanner continuously acquiring data as the patient travels thru the gantry. The data acquired are volumetric, containing all of the attenuation info. for a given area of anatomy. |
| The patient table may move _________ during the scan. | continuously |
| What is diastolic pressure? | The measurement of blood pressure at its lowest point, in between contractions of the heart. |
| Anthropomorphic | Human Characteristics. |
| Simple cysts of the kidney have average attenuation values in the range of what? | 0 to +20 Hounsfield units |
| Which CT scanner designs use an x-ray tube? | 1st - 4th generation CT PET/CT MDCT |
| Ray Sum | The measurement of transmitted radiation made by an individual detector. |
| Overbeaming | Expansion of the primary beam in an MSCT system to ensure that all detectors of the array are exposed to x-rays of equal intensity. |
| Cardiac cycle | The series of blood flow-related events that occur from the beginning of one heartbeat to that of the next. |
| What does mA determine? | Quantity of x-ray photons. |
| What is the recommended scan field of view (SFOV) for a CT exam of the CSP? | 50.0 cm |
| When compared with conventional radiography, CT produces dianostic images with improved what? | Low contrast resolution. |
| What intravenous contrast agent administration method provides the greatest overall plasma iodine concentration? | Bolus technique |
| Complete cardiac diastole correspond to which portion of the cardiac cycle on a electrocardiogram (ECG)? | T wave |
| Analog-to-digital converter (ADC) | Component of the data acquisition system (DAS) responsible for converting the electronic signal emitted by the CT detectors into digital form. |
| What factors may affect a patient's calculated glomerular rate (GFR)? | 1. age 2. sex 3. race |
| What is the primary goal of multiphasic CT evaluation of a pancreatic mass is what? | The determination of tumor respectively. |
| High-osmolar contrast media (HOCM) | Are ionic agents that dissociate into charged particles (ions) in solution. |
| Acute | Beginning suddenly & running a short but rather severe course. |
| Scout Image | Digital survey radiograph acquired by the CT system for the purpose of prescribing the cross-sectional acquisition. Similar to a conventional radiograph. |
| The peritoneal cavity is formed by the membranous sac called the ___________. | Peritoneum |
| What is the section thickness for paranasal sinuses? | 3 mm |
| The abdominal aorta bifurcates at the level of _______. | L4 |
| The gantry contains some of the most important components of the scanner including what? | 1. CT x-ray tube. 2. Detectors |
| Analog to digital converter (ADC) | Signal is digitized by ADC. Then stored temporarily in a raw data file. |
| Name 3 common sites for IV injection of iodinated contrast. | 1. Cephalic vein 2. Antecubital vein 3. Basilic vein |
| Image Uniformity | refers to constant CT # of an object |
| Algorithm | Computer adapted mathematical calculation applied to raw data during the process of image reconstruction. Computer compatible equation. |
| Name the benefits of multi-row detector CT. | *faster scans *increased anatomical coverage *scanning with thinner slices to improve resolution along the slice direction. |
| What is the AAPM | Scientific society of medical physicists. |
| CT Runoff | The CT angiographic assessment of the peripheral arterial tree from the renal arteries through the lower extremities. |
| The average photon energy of the CT x-ray beam can be increased by increasing what? | Filtration |
| Artifact | A form of noise on the CT image resulting from errors during the measurement of transmitted radiationby the detectors. |
| How is spatial resolution for CT usually expressed? | By the value of the spatial frequency at a 10% modulation transfer function (MTF). |
| Automatic tube current modulation (ATCM) | Software used in current MDCT systems to control patient radiation dose. |
| Why are x-rays produced whenever fast moving electrons collide with any form of matter? | The electron loses kinetic energy which is converted into the emission of an x-ray photon. |
| The type of MSCT detector array that utilizes multiple detectors in the longitudinal direction, each of the same length. |
| __________ is a parenteral route of meication administration. | Intramuscular |
| 1st Generation scanners | - pencil beam - single detector - the tube/detector assembly moved across the patient, then rotated by 1 degree - total scan time about 5 min per image - used for head study - translate-rotate motion |
| Absorption | Transfer of energy from radiation to matter. Removal of x-rays from a beam via the photoelectric effect. |
| Archival | The storage of CT data in either hard(film) or soft (digital) form. |
| ________ scanner design was the 1st to acquire 4 slices in a single rotation. | Multi-row Detector |
| Cupping artifact | An error occurring in the superior portion of the skull, where dense bone averages with the low-attenuating brain tissue. This partial volume artifact may result in abnormally dense-appearing brain parenchyma. |
| CT Bronchography | Specialized MSCT examination of the tracheobronchial tree consisting of MPR and volume rendered 3D images reconstructed from thin, overlapping MDCT axial images through the airways. |
| American Society of Radiologic Technologists (ASRT) | Scientific & professional society of radiographers. |
| Agatston score | Quantification of the volume & density of calcium within the coronary arteries. As calculated during a CT coronary artery calcification (CAG) examination, the Agatson score is used to indicate a patients risk of suffering a cardiac event. |
| Amplifier | Amplify's signal strength sent in analog form. |
| Retrospective ECG gating | Maneuver that may be used to remove unwanted pulsation artifacts from cardiac motion during a CTA of the chest for pulmonary embolism. |
| Surgical Asepsis | Infection control techniques required at the site of IV injection of iodinated contrast media. |
| What are some of the parameters that we directly control that affect spatial resolution? | * slice thickness * display FOV * image matrix * the reconstruction filter |
| Ampere (A) | The SI unit of electric charge. 1A=1 c/s |
| Absorber | Any material that absorbs or reduces the intensity of radiation. |
| Aluminum equivalent | Thickness of a material resulting in the same attenuation as aluminum. |
| Why are the techniques called analytic? | Because they utilize precise formulas for image reconstruction. |
| ALARA | The principle that radiation exposure should be kept as low as resonably achievable, economic & social factors being taken into account. |
| During CT arthrography, iodinated contrast media is injected directly into what? | Joint space |
| Attenuation | The progressive reduction of the intensity of the x-ray beam, as it passes through the patient's tissues. |
| What factors affect the dimensions of a voxel? | 1. slice thickness 2. matrix size 3. DFOV |
| What does the Kv control? | 1. the voltage potential between the tube cathode & anode while mA ultimately controls the filament current & thus the temp. of the cathode filament. 2. the energy level of the x-ray photons & mA controls the # of x-ray photons emitted from the tube. |
| Linearity | is a property of a system, characterized by output that is directly proportional to the input. In CT, linearity describes the amount to which the CT # of a material is exactly proportional to the density of this material (in hounsfield units) |
| Cerebral perfusion | The level of blood flow throughout brain tissue. |
| Mild reactions to iodinated contrast media include: | 1. nausea/vomitting 2. mild urticaria (hives) 3. pronounced sensation of warmth and/or flushing 4. altered taste 5. sweat/chills 5. nasal stuffiness/sneezing 6. anxiety |
| Absorption Efficiency | The ability of an individual CT detector to absorb & measure the transmitted x-ray intensity incident upon it. Primarily controlled by the characteristics & physical makeup of the detector material. |
| Array Processor | Data calculated into an image. Image is then transferred to host computer. |
| The following are true regarding CT systems: | 1. The gantry can tilt to an angle of approx. 30 degree 2. The patient table, gantry tilt mechanism & rotating gantry assembly all incorporate moving parts. 3. They can generate a straight coronal or sagittal image. |
| Automatic tube current modulation (ATCM) | CT system software used to adjust the mA throughout an acquisition to reduce patient radation dose to a minimum. |
| Blood urea nitrogen (BUN) | A measurement of renal function, determined as the amount of nitrogen in the blood in the form of the waste product urea.
The normal range is 7-25 mg/dL |
| Which CT scanner design does not use an x-ray tube? | Electron beam CT |
| Fusion imaging | Is the comparison of 2 imaging modalities yielding co-registered images. |
| Cerebral blood flow
(CBF) | A common measurement during CT perfusion studies of the brain. CBF is the quantity of blood (ML) that moves through 100g of brain tissue each minute.
Normal range in gray matter is 50-60 ML/100g/min |
| Contrast-induced nephrotoxity
(CIN) | A substantial decline in renal function that can occur after a patient receives IV contrast material. It is usually signified by a marked increase in serum creatinine over a baseline measurement obtained prior to contrast agent administration. |
| A patient in shock may exhibit what symptoms? | 1. tachycardia 2. rapid, shallow breathing 3. cyanosis |
| An intrathecal injection prior to a CT exam of the LSP places iodinated contrast material directly into the ________ ______. | Subarachnoid space |
| Image reconstruction is handled in the _______ ________. | Array Processor |
| Adaptive array | the type of MSCT detector array configured with the thinnest detectors at the center, surrounded by detectors of incrementally increasing widths along the z-axis. |
| Data acquisition system (DAS) | The electronic components of a CT system responsible for measuring the transmitted x-radiation absorbed by the detectors. |
| What does tube interscan delay time refer to? | The time between the end of one scan and the start of the next scan during which the tube will cool. |
| CT spatial resolution can be improved by what 4 things? | 1. using a smaller pixel 2. thinner slice imaging 3. narrowing the predetector collimation 4. increasing the source to isocenter distance. |
| Severe reactions to iodinated contrast include: | 1. profound hypotention 2. laryngeal edema 3. severe bronchospasm 4. pulmonary edema 5. cardiac arrhythmia 6. seizure 7. cardio- pulmanary arrest 8. death |
| High resolution computed tomography (HRCT) is most commonly used for what? | Lungs |
| What is implied consent? | Describes the situation in which an assumption is made that an unconscious or otherwise physically unable patient consents to medical treatment. |
| 3rd Generation scanners | - fan beam - several hundred detectors- curvilinear detector array - 360 degree rotate-rotate motion. Both the x-ray source & the detector array rotate about the same axis. |
| There is great value in overlaying the PET image on the high-resolution CT image in order to what? | Associate la metabolism change with a specific structure. |
| 360-degree linear interpolation (360LI) | 4. The detectors measure x-rays which completely penetrate the patient. |
| Binning | The process of electronically combining signal from adjacent detector elements to produce a reconstructed CT image that is thicker than the individual width. |
| In comparison w/ the surrounding soft tissues, the thyroid gland is ___________. | Hyperdense on the CT. Because it naturally contains iodine. This density increases further w/ administration of an iodinated contrast agent. |
| The spatial resolution of a CT imager can be improved by reducing what? | pixel size |
| What are 2 analytic methods of CT image reconstruction? | 1. filtered back-projection 2. fourier transform method |
| Automatic tube current modulation (ATCM) is employed by an MDCT system for what purpose? | Reducing patient radiation dose. |
| Absorption efficiency | The ability of an individual CT detector to absorb & measure the transmitted x-ray intensity incident upon it. Primarily controlled by the characteristics & physical makeup of the detector material. |
| Added Filtration | Aluminum (or its equivalent) of appropriate thickness positioned outside an x-ray tube & in the primary beam. |
| Convolution | Mathematical filtration used by the CT system to remove blurring artifact during the back-projection method of image reconstruction. |
| 2nd Generation scanners | - fan beam - multiple detectors in a straight line - the tube/detector assembly moved across the patient, then rotated by 5 degrees - total scan time about 20 secs per image - translate-rotate motion |
| Noise | When a CT image looks grainy or speckled. |
| Diastole | Refers to the relaxation of heart muscle. |
| CT console | Where instructional commands are entered by technologist. |
| Ionic contrast media | Are salts consisting of sodium and/or meglumine. |
| Name 4 types of contrast media. | 1. Intravascular Radiopaque 2. External Radiopaque 3. Negative contrast agents 4. Neutral contrast agent |
| A CT image is formed in part by projecting back all of the attenuation values recorded during data acquistion onto what? | Matrix |
| Back-projection | The mathematical process of CT image reconstruction whereby ray sum data are projected back onto a matrix. |
| Name 3 methods that may be employed to reduce radiation dose to pediatric CT patient's. | 1. reduce mA 2. limit phases of acquisition 3. increase pitch |
| High resolution CT | Is a specialized technique using narrow section widths & a high resolution algorithm for image reconstruction. It is used to maximize detail of high spatial frequency tissue, such as the lungs & bony structures. |
| American College of Radiology (ACR) | Professional society of radiologist & medical physicists. |
| Absorbed Dose | Energy transferred from ionizing radiation per unit mass of irradiated material. Expressed in rad (100 erg/g) or gray (1J/kg). |
| Segmenting the data acquisition process into seperate components of smaller rotation angles may improve _______ ________. | Temporal resolution |
| Array Processor (AP) | Component of the CT computer system responsible for receiving raw scan data, performing all of the major processing of the CT image & returning the reconstructed image to the storage memory of the host computer. |
| How is collimation accomplished? | By physically blocking x-rays. |
| Bit Depth | The number of information bits contained within each pixel. |
| CT Fluoroscopy | Continuous real-time CT imaging used predominantly for CT-guided interventional procedures. |
| Contrast enhancement of vasulature greatly aids in the diagnosis of many disorders including.... | 1. aneurysm 2. thrombus 3. stenosis |
| Interpolation | The mathematical technique allowing the reconstruction of motion free images from helically acquired CT data. |
| Spatial resolution | The ability of a CT imaging system to display fine details separately. Given in units of line pairs per centimeter. |
| What made helical imaging possible? | Continuous rotation scanners. |
| Data channel | Pathaway of data transmission from the detectors to the computerized components of the system's data acquisition system. The number of data channels of a CT system determines the maximum number of sections that may be acquired with each gantry rotation. |
| Linearity is particularly important for what? | bone mineral measurement. |
| What are the instructions given to the patient before starting any CT exam? | 1. Describe the exam to be performed: area of body, ect. 2. Explain the process of contrast administration. 3. Give any necessary breathing instructions clearly & precisely. |
| Contrast resolution | The ability of a CT system to detect an object with a small difference in linear attenuation coefficient from the surrounding tissue. May also be referred to as low-contrast detectability or sensitivity. |
| _______ _______ artifacts are unique to MSCT systems. | Cone beam |
| Which technology do multirow detector scanners employ? | 3rd Generation |
| What type of isolation technique protects against infection transmitted through fecal material? | Enteric precautions |
| The adult spinal cord ends at what level of the lumbar vertebra? | L1-L2 At this level it tapers to a point known as the conus medullaris. |
| What is scatter radiation caused by? | Deflections from the original trajectory of an x-ray photon through the patient. |
| The operator's console may include what 3 things? | 1. monitor 2. keyboard 3. graphic input device |
| The scan controller is responsible for the timing & operation of what? | 1. Patient table 2. Gantry 3. High voltage generator |
| Leiomyoma | A benign mass of smooth muscle. It commonly occurs in the uterus & is readily identified on CT exam as a bulky, nonspecific uterine enlargement. |
| CT Enterography | Specialized CT evaluation of the small bowel after the oral administration of low density (0.1%) barium. |
| What is an electron beam CT (EBCT) scanner. | It is an alternative design that has no x-ray tube. It offers very fast scan times making it suited for cardiac & coronary artery imaging. |
| Increasing the ____ or exposure time will increase the total number of photons, but will not increase the likelihood that each of those photons will penetrate the material. | mA |
| The ________ _________ is the key point of interaction between the technologist & the imaging system. | Operator's console |
| What wave of an ECG corresponds to cardiac diastole? | T wave |
| Orthogonal | Imaging planes that are perpendicular to each other. |
| CT Number | Relative value assigned to each pixel to quantify the attenuation occurring in each voxel in comparison with the attenuation of water. The calculated CT number for a given pixel is given in Hounsfield unit (HU). May also be referred to as pixel value. |
| Bow-tie filter | A type of filter added to the CT x-ray tube to compensate for the cylindrical shape of most body parts. The filter is thicker at the ends & helps shape the beam to reduce patient radiation exposure. |
| Transverse slices are always acquired, but studies of the internal auditory canals, pituitary, orbits, sinuses & facial bones also require what? | Coronal slices |
| What does the slip ring transfer? | *electrical power *scanning instructions *detected signals between stationary components & rotating gantry components. |
| What is dyspnea? | Used to define the condition of difficult breathing. |
| What is the average CT value range for fat? | -50 to -100 Hounsfield units |
| Most of the commands from the technologist are received by the what? | Operator's console |
| Bremsstrahlung radiation includes which type of electron activity? | 1. collision between an incoming electron & the nucleus of the target atom. 2. slowing down of an incoming electron due to the effect of passing close to the positive charge of the nucleus of the target atom. |
| CT Myelography | CT evaluation of the spinal cord and nerve roots after the intrathecal administration of iodinated contrast material. |
| Vacuum Phenomenon | The accumulation of gas within a degenerating intervertebral disk. |
| CT Arthrography | CT evaluation of a joint after the intra-articular injection of iodinated contrast material. |
| Aliasing | A form of streak artifact caused by an insufficient # of views (data samples) obtained during data acquisition. |
| Acute effects | See early effects. |
| High voltage generator | Produces high voltage potential that exists between cathode & anode. |
| The information included during the 3D reconstruction of a CT scan is controlled by the _________ __________. | Threshold setting |
| What is the normal rate for diastolic blood pressure in adults? | 60-90 mm Hg |
| The full width at half maximum (FWHM) of a CT scanner is used to describe what? | spatial resolution |
| 4th Generation scanners | *fan beam *multiple detectors encircle the patient and do not rotate around the patient * Only the tube rotates around the patient * Total scan time of 1 second per image or faster |
| Fourier transformation (FT)is a method to: | 1. transform object size to spatial frequency. 2. change distance into inverse distance. |
| Constant mAs | The product of milliamperage (mA) and scan time (seconds) utilized for a CT acquisition. |
| Arterial phase | Period of peak arterial enhancement following the bolus IV administration of iodinated contrast material. For ex, the hepatic arterial phase occurs approx. 25-35 seconds after the initiation of contrast agent administration. |
| The section thickness of a CT scan directly affects what? | The detail & spatial resolution of the image. Narrow section widths result in greater detail for imaging of small anatomic parts such as the sinuses. |
| Interpolation | Is the mathematical process whereby data from tube rotations just above & just below a given slice position are used for image reconstruction. |
| What does the EBCT produce? | An electron beam that streams from its electron gun & which is electro-magnetically directed toward an array of tungsten anodes. An x-ray beam is generatred when the elctron beam strikes the anodes. |
| Afterglow | The tendency of a scintillation type CT detector to continue to glow in response to x-radiation after the exposure source has been terminated. |
| The International Normalized Ratio (INR) is calculated to standardize which laboratory value? | Prothrombin time (PT) |
| The ______ ______ is the primary link between the tech & the other components of the imaging system. | Host computer |
| Advanced single slice rebinning (ASSR) algorithm | Cone beam correction algorithm utilized to overcome potential attenuation calculation errors from the divergent beam of MSCT systems. |
| Where does the analog signal go to after it leaves the amplifier component? | The sample-and-hold component. (S/H) |
| AAPM | American Association of Physicists in Medicine. |
| Noise on a CT image principally influences what? | contrast resolution |
| CT host computer | Translate each command as it is entered into the systems machine language. |
| CT scan controller | Responsible for the timing & operation of the table, gantry & high voltage generator. |
| Array Processor | A specialized component of the CT computer system. It is capable of performing the massive calculations req'd for CT image reconstruction. |
| 180-degree linear interpolation (180LI) | Type of algorithm used for MSCT image reconstruction in which data acquired from a shorter distance (180 degrees) away from the reconstructed slice location are interpolated. |
| What is complete cardiac diastole? | The period of atrial & venticular relaxation after heart contraction. |
| There is a tradeoff between _______ the image quality & ________ the patient dose. | Maximizing Minimizing |
| A Modulation Transfer function (MTF) can be used to estimate what? | spatial resolution at all spatial frequencies. |
| What are the factors that determine the potential for surgical removal of a pancreatic tumor? | 1. vascular involvement of the mass 2. local tumor spread 3. metastases |
| What are the indications for CT exmas of the head? | Evaluation of trauma, stroke, headache, tumors, endocrine disease, inflammatory disease & congenital problems. |
| Name the non-ionic contrast media. | 1. iopamidol (ISOVUE) 2. iohexol (omnipaque) 3. iopromide (ultravist) |
| Photodiode | Solid state device used to record the light flashes given off by a scintillation crystal. |
| What are the 4 influences on parameter selection? | 1. contrast resolution 2. spacial resolution 3. image noise 4. patient dose |
| CT Enteroclysis | Specialized CT evaluation of the small bowel whereby enteral contrast material is administered directly into the duodenum through a nasogastric catheter placed under fluoroscopic guidance. |
| DAC | Responsible for converting the digital signal into an analog form. |
| On an ECG of the complete cardiac cycle, at which portion of the R-R interval is the heart muscle in diastole? | 55% - 75% |
| Angiomyolipoma | A common benign mass found in the kidneys, consists of muscle cells, blood vessels & fat. |
| What does the tube interscan delay time refer to? | The time between the end of one scan and the start of the next scan during which the tube will cool. |
| What mathematical technique is used exclusively for image reconstruction with spiral CT scanners? | Interpolation |
| What is the main purpose of the detector? | Capture x-ray photons & convert them to a measurable signal. |
| Aluminum (Al) | Metal most frequently selected as x-ray beam filter material because it effectively removes low-energy x-rays. |
| In order for an x-ray photon to be measured it must what? | 1. enter the detector chamber 2. be absorbed by the detector material 3. be converted to a measurable event. |
| How are 3D studies best performed? | With the use of narrow sections acquired with no spacing or preferably an overlap. A detail (bone) algorithm is used for optimal demonstration of bony structures. |
| Beam Pitch | The ratio of table feed per gantry rotation to the total collimation used during acquisition with a multislice CT (MSCT) system. |
| Corticomedullary phase | A late arterial phase of renal enhancement beginning 30-40 seconds after the initiation of contrast agent administration. Optimal enhancement of the renal cortex & renal veins occurs during this period. |
| When should increasing the dose to the patient be considered? | Only when the result of not doing so would otherwise be a non-diagnostic study. |
