CT review Flashcards
main advantage of CT
the ability to differentiate small differences in density of anatomic structures and abnormalities and the superior quality of the images
spatial resolution
describes the ability of a system to define small objects distinctly
low-contrast resolution
refers the to ability of a system to differentiate on the image objects with similar densities
temporal resolution
refers to the speed at which the data can be acquired
z axis
refers to the thickness of the plane
determines the thickness of the slice
x=width
y=height
what is the most common matrix size in CT
512
attenuation meaning
the degree at which a beam is reduced
density
defined as the mass of a substance per unit volume
common CT number or HU
dense bone 3,000
muscle 50
white matter 45
gray matter 40
blood 20
cerebrospinal fluid 15
water 0
fat -100
lungs -200
air -1,000
* HU less than water are given a negative
positive contrats agents
material of higher density
barium sulfate and iodine
negative contrast agents
low density
water
artifacts
-objects seen on the image but not present on the object scanned
beam hardening artifact
result from preferential absorption of low energy photons which leaves higher intensity photons to strike the detector array
-commonly present at base of skull
-appear as dark streaks
volume averaging
process by which different tissue attenuation values are averaged to produce one less accurate pixel reading
aka partial volume effect
-small pixel size reduces the chances of volume averaging
step and shoot
in 1980s scanning system was a step and shoot.
-the tube rotated 360 around the patient acquiring a single slice. then the motion of the xray tube was stopped while the patient was advanced. this was repeated until desired areas was covered
helical(spiral) scanning
1990s
developed a system that eliminated the cables so there is continuous rotation of the gantry
-allows for uninterrupted data that traces a helical path around the patient
multidetector scanning
in 1992 scanners where introduced that contained two rows of detectors
data acquisition
data are acquired when xrays pass through a patient to strike a detector and are recorded
gantry
gantries vary in size as well as in diameter of the aperture with typical ranges being 70-90cm
-the gantry can be tilted
-slpi rings allow the gantry too rotate continuously making helical scan possible
generator
-high frequency generators are used and are located within the gantry
-the power capacity of the generator is listed in kilowatts(kW)
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xray source
-CT tubes often contain more than one size focal spot
-smaller focal spot improve spatial resolution but concentrate heat into smaller portion can not tolerate as much heat
-anode heat capacity is measured in million heat units(MHU)
-anode that dissipation’s measure in thousand heat units(KHU)
filtration
-filters are used to shape the xray beam
-help reduce radiation dose to patient and help reduce image artifact
-bowtie filters: often used for the body, reduce beam intensity at the periphery of the beam corresponding to the thinner areas of the body
-collimators: restrict the beam and reduce scatter radiation, which improves contrast resolution and decrease patient dose
-source collimators: aka prepatinet collimator, affect slice thickness of the beam
-predetector collimators: act on the xray after it has emerged from the patient and before it strikes the detector
detectors
-collect information regarding the degree to which each anatomic structure attenuates the xray beam
-optimal characteristics of a detector:
-high detector frequency: ability of the detector to capture transmitted photons and change them to electronic signals
-low or no afterglow: brief, persistent flash of scintillation that must be taken into account and subtracted before image reconstruction
-high scatter suppression
-high stability
-made from solid state crystal or xenon gas filled chambers
-xenon gas are much less efficient but are less expensive, easier to calibrate and are highly stable
-solid state also called scintillation use crystal that fluoresces when struck by an xray photon, very efficient absorb almost 100% of the photons that reach them
detector
geometric efficiency of a detector
refers to the amount of space occupied by the detector collimator plates relative to the surface area of the detector
detector
capture efficiency
refers the to ability with which the detector obtains xray beams that have passed through the patient
detector
absorption efficiency
refers to the number of photons absorbed by the detector
detector
response time
time required for the signal from the detector to return to zero
detector
dynamic range
the ratio of the maximum signal measured to the minimum signal the detectors can measure
scanner generation
6 generations
1st generation: thin xray beam passed linearly over the patient and a single detector followed on opposite side of the patient.the tube and detector where then rotated slightly and process was repeated until 180 degrees was covered. NO LONGER USED
2nd generation: xray beam passed linearly across the patient before rotating, but with a fan shaped xray beam.NO LONGER USED
3rd generation: consist of an xray tube that produces a fan shaped bema that covers the entire field of view and a detector array.tube is focused on the detector array so collimation is available reducing scatter, disadvantage is frequent ring artifacts
4th generation: use a detector array that is fixed in a 360 circle within the gantry, the tube rotates within the detector array and produces a fan shaped beam. motion artifacts are an issue, will produce higher dose with same technique as 3rd generation
5th generation: aka electron beam CT(EBCT) or ultra fast CT, xray beam or detector moves
6th generation: aka dual source use two side by side tube detector arrays which can be energized using same or different kVp
detector electronics
-DAS data acquisition system measures the number of photons that strike the detector and converts the information to a digital signal and send the signal to the computer
-DAS is position in the gantry near the detectors
-ADC analog to digital converter converts the analog signals from the detector to digital format
image reconstruction terminology
image reconstruction: the process of manipulating data
-algorithm: is a precise set of steps to be performed in a specific order to save a problem
-reconstruction algorithms: used to convert information obtained from the detector array into information suitable fro image display
-fast Fourier transfrom(FTF) efficient algorithm that is used in image analysis
-interpolation: mathematical method of estimating the value of an unknown value using the known values on either side of the unknown
equipment components used for image reconstruction
-hardware is the portion of the computer that can be physically touched
-software is instructions that tell the computer what to do and when tot do it
-archiving: saving data on axillary devices for possible future viewing
-principle components of a computer are:
-input device
-output device
-central processing unit
-memory
- input device: feed data into the computer(keyboard, mouse, touch screen, CT mechanisms)
-output device: accept processed data from the computer(monitor, laser camera, printer)
-CPU central processing unit interprets computer program instructions and sequences tasks.
-CPU is made up of microprocessor, control unit, primary memory
-Types of memory
-ROM(read only memory)
-RAM(random access memory)
-WORM(write once read many)-saved memory cannot be rewritten, erased, reformatted or
data types
-raw data: includes all measurements obtained from the detector array, aka scan data
-prospective reconstruction: image reconstruction automatically produced during scanning
-retrospective reconstruction: the same raw data is used later to generate a new image
-image data: those that result once the computer has processed the raw data and displayed an image
terminology
-ray: the path the xray beam takes from the tube to the detector
-ray sum: measurement of how much the beam is attenuated
-view: complete set of ray sums
-attenuation profile:eh system accounts for the attenuation properties of each ray and correlates them with the position of the ray
- back projection: process of converting the data from the attenuation profile to a matrix
-convolution: process of applying a filter function to an attenuation profile
-Scan Field of View(SFOV)determines the area within the gantry from the raw data are acquired
-DFOV(display field of view) determines how much of the raw data is used to create an image
display monitors
-output device allows the information stored to be displayed
-the output device is usually a cathode ray tube(CRT) or some form of flat panel like a TFT LCD, or LED
-DAC convert the anaolg signal to digital signal
cameras
-multiformat cameras transfer the image displayed on the monitor to film
-laser cameras bypass the image on the display monitor and transfer the data directly form the computer which improves image quality
gray scale
-there is 2000 different Hounsfield Units but monitor can only display about 1024 shades
-the human eye can only differentiate typically fewer than 40 shades of gray
-window width determines the number of hounsfield units assigned to each level of gray
-0 hounsfield units=water
- -1000 hounsfield units=air
-1000 hounsfield units=dens material like bone
-lower values are darker shades
-higher values are lighter shades
window width
-determines the HU represented on a specific image
-selects the quantity of HU to be displayed as shoes of gray
-values high than selected range appear white
-values lower than selected range appear black
-increasing window width=more numbers assigned to each shade of gray
-wide window widths are best for imaging tissue types that vary
-narrow window width is used for tissue with similar densities
-manipulation of window width and window levels referred to as windowing
window level
-selects the center CT value of the window width
-slects which HU are displayed on the image
how to determine the range
if the window width is 300
window level is 200
divide window within half: 300/2=150
subtract that from the window level: 200-150=50 which is the lower limit
to calculate ether upper limit
150+200=350
therefore the gray scale range is 50 to 350
ROI
-region of interest
-defining an area of interest
-place a circle over a area of concern/interest to get the average HU of that area
-if a ROI is placed over an area the reading is the average for al the pixels within that ROI
standard deviation
-factors that produce high standard deviation include
1.mixed attenuation tissue within the ROI(calcium within the organ)
2.ROI includes a streak artifact
3.ROI that is not inside the margins of an object being measured (kidney cyst measured with adjacent renal calyx)
reference image
-displays the slice ;Ines on corresponding locations on the scout image
-helps localize slices according to anatomic landmarks
image magnification
-uses only image data and does not improve resolution
-simply makes the existing image bigger
-often used when acquiring distance measurements or placing a ROI
histogram
graphical display showing how frequently a range of CT number occurs within a ROI
common window settings
head
posterior fossa: ww:150,WL:40
brain:ww;100,WL30
temporal bone;WW;2,800,WL:600
neck:WW:250,WL30
chest
mediastinum:WW;350,WL:50
lung WW:1500,WL:-600
abdomen
soft tissue:WW:350,WL:50
bone:WW;1800,WL:400
spine
soft tissue:WW:250,WL:50
bone:WW:1800,WL:400
localizer scans
-aka: scout,surview,topogram,scanogram,preview, pilot
-created while the tube is stationary and the table moves through the scan field
-structures appear superimposed like conventional radiography
-the position of the tube determines the orientation of the image: if the tube is above the patient the localizer scan will be AP
-miscentering the patient in either direction can result in out of field artifact
-some protocols it is impossible to use the scout image for landmarks and in that case there are 2 things that can be done
1.one cross sectional slice is taken and checked for accuracy
2.additional cross sectional slices are included superiorly and inferiorly of the estimated location
step and shoot scanning
-the CT table moves to the desired location and remains stationary while the xray tube rotates within the gantry collecting data
-aka axial scanning, conventional scanning, serial scanning, or sequence scanning
-clustering: grouping more than one axial scan in a single breath hold
-disadvantage: cumulative effect of the inter scan delay adds to total exam time. also axial data has more limitations regarding reconstruction options than do data acquired with helical methods
-slice misregistration occurs when a patient breathes differently with each data acquisition
single detector row systems
-SDCT the largest allowable slice thickness is less than the detector width typically 10mm
-the radiation emitted from the xray source is referred to as a fan beam
-each gantry rotation produces data for a single slice
multi detector row systems
-in MDCT a single rotation can produce multiple slices
-MDCT have increased the sped of gantry rotation which further increases volume coverage per unit time
-MDCT can be used for either axial or helical data acquisition
-some MDCT systems the detectors in the center are thinner than those at the periphery. this is called adaptive arrays, nonuniform arrays, hybrid arrays
-binning a process in which data from multiple parallel rows of detector elements can be combined
-EX: 16 detector rows, 1.25mm wide can be combined in the following:
-4 slices each 1.25mm
-4 slices, each 1.25mm(grouping 2 detector rows for each slice)
-4 slices, each 3.75mm(grouping 3 detector rows for each slice)
-4 slices each 5mm(using all the available detectors groups of 4)
dual source CT
-uses two sets of xray tubes and two corresponding detector arrays in a single CT gantry
-goal is to increase scan speed
-the two xray tubes can be programmed to use different kVp settings while working simultaneously
dual energy CT
-aka spectral imaging refers to any acquisition of CT data at two different kVp settings
helical scanning
-3 basic ingredients define a helical scan process;1.continualy rotating xray tube, 2. constant xray output,3.uninterupped table movement
-aka spiral, volumetric,continous acquisition scanning
-advantage: ability to optimize iodinated contrast agent administration, reduction of respiratory misregistration, and reduction of motion artifacts from organs such as the heart
-major improvements that led to the development of helical scan methods are:
-gantries with slip ring design
-more efficient tube cooling
-higher xray output
-smoother table movement
-software that adjusts for table motion
-improved raw data management
-more efficient detectors
-in helical scanning the beginning point of the slice is not win the same plane as the end point(think of it like a spring)
-helical interpolation methods create images that closely resemble those acquired in a traditional axial mode “unslant” the slice
pitch
-used to describe the table movement during a helical scan
-defined as travel distance of the table per 360 rotation divided by xray beam collimation width
-when pitch is less than 1 scan overlap occurs
-as pitch increases fewer data is acquired for each table position
-increasing pitch results in a scan covering more anatomy lengthwise for a given total acquisition time, while reducing dose.
scanning parameters
-factors that affect the quality of the image. can be controlled by the operator
-include mA, scan time, slice thickness, filed of view, scan algorithm, kVp, pitch for helical scan
mAs
-mA and scan time together define the quality of the xray energy
-mA and scan time is mAs
-increasing mA increases the number of electrons that will produce xray photons
-scan time is the time it takes for the gantry to make a complete 360 rotation
-mAS is the quantity of xrays produced
-higher mAs allow shorter scan times to be used
-reducing mAs while keeping kVp constant reduces the dose to the patient
kVp
-tube voltage
-the quality of the beam
-more limited choices usually fixed at 120
-increasing kVp increases the intensity of the beam and its ability to penetrate a thick dense part
-adult body scan usually done at 120kVp, paediatric body scan done at 20 kVp
uncoupling effect
-the image quality is uncoiled form the dose so when a high mAs or kVp is used a good image still results
Field of View
-SFOV determines the area within the gantry for which raw data are acquired
-DFOV determines how much of what section of the collected raw data are used to create an image
slice thickness
-impacts image quality
-thinner slices produce sharper images
reconstruction algorithm
-determine how data are filtered in the reconstruction process
-some algorithms help reduce the appearance of artifacts by reducing the difference between adjacent pixels but as a result sacrifice spatial resolution-often called smoothing algorithms
-some filters accentuate the difference between neighbouring pixels to optimize spatial resolution-often called bone or detail filters
iterative reconstruction
-IR refers to image reconstruction algorithms that begin with an assumption and then improve the image by continually analyzing scan data and making adjustments
-valuable for its ability to enhance image quality for lower dose scans
scan geometry
-a partial scan is when images are created from less than 360 degree rotation, typically 180 plus degree of arc of the fan angle-aka half scans
-overscan uses information from more than 360 rotation
image quality
-comparison of the image to the actual object
-in CT is directly related to its usefulness in providing an accurate diagnosis
-image accuracy aka image fidelity
-the two main features of image quality that can be measured are
1.detail(high contrast) resolution; the ability to separate objects
2.contrast resolution; the ability to differentiate between objects with very similar densities as their background
spatial resolution
-aka detail resolution
-systems ability to resolve as separate forms, small objects placed very close together
-can be measured directly using line pair phantom
-can be calculated from analyzing the spread of information within the system
-line pair phantom is lead strips placed in acrylic
-number of line pairs visible per length is also called spatial frequency(the frequency an object will fit into given space)
-MTF is most commonly used method of describing spatial resolution ability
-MTF is the ratio of the accuracy of the image compared with the actual object scanned
-CT ha significantly worse spatial resolution
factors affecting spatial resolution
matrix,DFOV,pixel size, slice thickness
-matrix size and DFOV section determine pixel size
-the greater the total number of pixels the smaller each individual pixel is
-DFOV determines how much raw data will be used to reconstruct the image
-increasing the DFOV increases the size of each pixel
-thin slices result in near isotropic voxels(cube shape-measure same all around)
reconstruction algorithms
-some will smooth the data more heavily by reducing the difference between adjacent pixels
-some accentuate the difference between neighbouring pixels to optimize spatial resolution-often called bone or detail filters
focal spot size
larger focal spot size cars more unsharpness and reduce spatial resolution
contrast resolution
-aka low contrast resolution
-is the ability to differentiate a structure that varies only slightly in density from its surrounding
-CT is superior in all modalities for contrast resolution
noise
-grainy appearance on under exposed images
-major cause of noise is quantum mottle-occurs when there is insufficient number of photons detected
-SNR-the number of xray photons detected per pixel
factors affecting contrast resolution
-mAs
-doubling mAs increase SNR by 40%
-mAs will improve contrast resolution but will also increase dose
-thicker slices allow more photons to reach the detector and therefore have a better SNR and appear less noisy
-bone algorithms produce lower contrast resolution
-soft tissue produce higher contrast resolution
temporal resolution
-how rapidly data are acquired
-controlled by gantry rotation speed, number of detector channels in the system, speed which the system can record changing signals -important in imaging moving structure and dynamic flow of contrast
quality assurance
-design to ensure that the CT system is producing the best possible quality image
-technologist typically perform and record routine quality control tests
-medical physicist obtains dosimetric data
-three basic concepts the program is designed by
1.the tests that make up the program must be performed on a regular basis
2.the results from all the tests must be recorded using consistent format
3.documentation should indicate whether the tested parameter is within specified guidelines
quality control phantoms
-line pair phantom: used to measure spatial resolution directly. Usually done MONTHLY
-phantom with objects of varying sizes that have a small density difference between their background is used for contrast resolution: usually done MONTHLY
-slice thickness: phantom contains includes a ramp, spiral and wedge.done SEMIANNUALLY
-laser light accuracy: done SEMIANNUALLY
-image noise: water phantom is used” done WEEKLY
-cross field uniformity: the ability of the CT scanner to yield the same CT number in a homogeneous object. several ROIS are placed around the phantom and are expected to have the same measurement. done WEEKLY
-linearity refers to the relationship between CT numbers and their liner attenuation values of the scanned object at a designated kVp value.daily calibrations help reduce fluctuations
-linearity a phantom with objects of known densities is scanned and the objects are measured. done SEMIANNUALLY
image artifacts
-can be classified as:
-physics based-physical process associated with data acquisition
-patient based
-equipment induced
-beam hardening artifacts: result when lower energy photons are absorbed leaving the higher energy photons to strike the detector
-occurs more with dense objects
-cupping or streak artifact
- to avoid beam hardening best thing is to select to correct SFOV
-partial volume artifact: dense object lines to the edge of the FOV. causes shading, can be reduced by using thinner slices
-undersampling: occurs when there is not enough information collected during acquisition- results in aliasing artifact which is stripes come form a dense object
-can be reduced by increasing scan time or by reducing helical pitch
-edge gradient: streak artifact arising from irregular shaped object that have a different density then surroundings
-patient motion artifact: shading, streaking, blurring or ghosting
-out of field artifacts: caused by anatomy that extends outside the selected SFOV
-ring artifacts: mostly with third generation scanners, appear as a ring or multiple rings, caused by faulty or miscalibrated detector elements
-tube arcing: caused by an electrical current surge, slight streaks that are barley noticeable or opposite that the image is useless
-windmill artifacts: appear on MDCT helical system the beam becomes more coned shaped, streaks or brightness and dark shading near large density difference areas
retrospective reconstruction
-reconstructing raw data to create images only done from he operators console
-DFOV,image center and reconstruction algorithm can be changed retrospectively
image reformation
-aka image rendering
-in order to reformat all the source images must have identical DFOV, image center, gantry tilt, and must be contiguous
-only uses image data
-the thinner the original slice step better the reformatted image
multiplanar reformation(MPR)
-reformations done to show anatomy in various panes
-2D
-can be created in coronal, sagittal or oblique planes
-scanner created MPRs are programmed into the system to be generated automatically
-manual MPR require the operator to input the criteria
-if MPRs are to be created form PACS the thinnest possible slices must be used
3D reformation
-attempts to represent the scan volume in a single image
-can be done on independent consoles
-draw an imaginary line from the viewer through the data volume
surface rendering
-aka shaded surface display(SSD)
-creates the outline or shell of a structure
-useful for examining tubular structures like airways, colon and blood vessels
Maximum intensity projection(MIP)
-selects only the highest value voxel from the data set for display
Minimum intensity projection(MinIP)
-selects the minimum value voxels for display
volume rendering
-3D transparent representation of the imaged structure
-all voxels contribute to the image
end-liminal imaging
-form of VR that is specifically designed to look inside the lumen os a structure
-aka virtual endoscopy
Region of interest Editing
-process of selectively removing or isolating information from the data set
-aka segmentation
-purpose is to better demonstrate the area of interest by removing obscuring structures
HIE
Health Information Exchange
-allows healthcare providers and patients to appropriately access and securely share a patients vital medical information
Informatics
-the collection, classification, retrieval and dissemination of recorded information
-HIS hospital information system: focus on administrative issues such as patient demographic data, financial data, patient location within the hospital
-CIS clinical information system: keep track of clinical data
-CPOE:computerized physician order entry: systems electronically transmit clinician orders to radiology and other departments
-EHR: digital record electronic health record
-EMR:electronic medical records
-RIS: used for scheduling patients, string reports, patient tracking, protocoling exams, and billing
-PACS: rings of technologies necessary for the storage, retrieval, distribution and display of images
-
two key components form the information infrastructure in the radiology department
1.RIS:radiology Information System
2.PACS:picture archive communication system
what form must images be in to be included in PACS
digital format
digital format also known as soft copy
networking
-networking is a group of two or more computers linked together
-LAN: local area network, computer networks that are close together(in the same building)
-WAN:wide are networks, farther apart and connected by telephone lines, cables or radio waves
-“wired”-are those linked by physical connection
-“wireless”-use radio waves to transmit data between computers
-servers essential to the functioning of PACS are called core servers
-bandwidth: is the capacity of the network connection
-lossless: compressing image data with no image data lost during the process
-lossy: compressing image data but artifacts are introduced
DICOM
-Digital Imaging Communication in Medicine
workstation monitors
-in 19990 all monitors were CRT(cathode ray tube)
-recently LCD(liquid crystal display) is used
-LCD cost 2-3 times more than CRT, but they have a longer life span and consume less energy
-quality assurance is simpler with LCD
how many patient identifiers are required
at least 2
Data storage
-classified as online:when images are instantly accessible
-classified as near line: when images are automatically retrieved from a storage system
-offline: when image devices must be located and manually loaded into the system
-optical jukebox; robotic storage systems that automatically load and unload the optical discs
pre exam questions
-questions about renal function, allergies or hyperthyroidism should be asked by the technologist prior to the exam to ensure the patient is safe to receive contrast
lab values for CT
-eGFR(glomerular filtration function)
-serum creatinine
-blood urea nitrogen(BUN
-provide information about a patients kidney function
-normal eGFR is greater than 60mL/min/1.73m^2
-normal range for BUN is 7-25mg/dL
-normal range for serum creatinine is 0.6 to 1.7mg/dL
lab values for biopsies
-prothrombin time(PT)
-partial thromboplastin time(PTT)
-platelet count
-normal PT is 11-14 seconds
-normal PTTis 25-35 seconds
-normal platelet count is 150,000 to 400,000
patient education and consent
-at a minimum the technologist should describe:
-how the procedure is carried out
-the approximate time the procedure will take
-if there is contrast given
-what is expected of the patients
-if there is any necessary follow up
consent
-basic consent is explaining to the patient what you are going to do and asking if they agree
-many times a consent form is signed by the patient especially when contrast is given
-consent form must be signed by the patient before any pain medications or sedatives are given that can alter there state of mind
-paediatric patients a parent or legal guardian can sign the consent form
immobilization devices
-used for patient safety and to improve image quality
-when possible basic consent should be given to use the devices
-when restraining devices are used must adhere to:
-patient must be Allowed as much mobility as is safe
-the areas of which the body are immobilized must be padded to prevent injury
-normal anatomic position must be maintained
-knots that become tighter when moved are prohibited
-immobilzer must be easy to remove quickly
-circulation or respiration cannot be impaired
-if leg immobilizers are used wrist ones must be used al well to prevent them removing them
vital signs
-body temperature
-pulse
-respirations
-blood pressure
body temperature
-can be taken by placing thermometer in mouth, ear(tympanic), axilla or rectum
-oral, rectal and tympanic are higher than axilla
-temporal artery sweep a small scanner across the forehead then behind the patient ear
normal oral:96.8-100.4F, average 98.7F
normal rectal: 97.2-100.8F, average 99.1F
normal axillary: 95.8-99.4F, average97.7F
temporla artery: 97.2-100.8F, average 99.1F
pulse locations
common places to feel pulse
-temporal pulse:just anterior to ear: superficial temporal artery
-facial pulse:lower margin of mandible, about 1/3 anterior to angle (facial artery)
-carotid pulse: along anterior aspect of neck(carotid artery)
-radial pulse: at the thumb side of wrist)radial artery)
-brachial pulse: on medial side of elbow cavity between the biceps and triceps muscle(brachial artery)
-femoral pulse:in the groin(femoral artery)
-popliteal pulse: behind the knee(popliteal artery)
-pedal pulse:posterior ankle, behind medial malleolus(tibias posterior artery)
-pedal pulse; top of foot(dorsals pedis artery)
average pulse
-adult 60-100 beats pe rminute
-athletic adults 45-60 beats per minute
-child 95-110 beats per minute
-infants 100-160 beats per minute
respirations
-number of breaths a person takes per minute
-adults:14-20
-adolescent youth:18-22
-children: 22-28
-infants: 30 or more
blood pressure
-measured by a sphygmomanometer in mmHg
-systolic is peak pressure top number
-diastolic is lowest pressure bottom number
-healthy adult: 120/80
-hypertension: blood pressure that is abnormally high
-hypotension: blood pressure that is abnormally low
-normal range for adults: 90-140/60-90
-normal range for children: 65-130/45/85
Sinuses CT
-intended as an inexpensive accurate and low radiation dose method for confirming the presence of inflammatory synodal disease
-can be done with IV or without
-reoccurring sinuits is done without
Head CT
Brain
begin at the base of the skull and continue superiorly
temporal bones
-organs of hearing and balance are located in the petrous ridges of the temporal bones
-thin slices are used as these organs are tiny
-coronal and axial planes
neck CT
-usually done with IV contrast unless contraindicated
-often times artifacts caused by dental work obscure the surrounding structures
Spine CT
-usually done without Iv contrast
chest CT
-routine chest protocol includes both soft tissue and lung windows
-apices to under the diaphragm
abdomen pelvis CT
-include the entire liver and other organs
wrist
-the orientation when doing, elbows, wrist, forearms and hands can become confusing so often times a marker is used to help
knee
most Ct of the knee extend from the distal femur to beyond tibial plateau
-both knees are included in the scan field of view only the targeted knee is included in the display field of view
