___ must sign the informed consent form for a minor.
A parent or legal guardian
_____occurs when a patient is in need of immediate medical services but is unconscious or is physically unable to consent to treatment. In this case, services are rendered with the assumption that the patient would consent if able.
Implied consent
Communication is the key to any successful patient interaction It should begin during the _______ to identify concerns regarding exam tolerance, potential contrast agent contraindications, and so on
scheduling/screening process
Particularly during contrast studies, the patient should
be instructed to empty the bladder before the start of the exam to reduce the possibility of discomfort or interruption.
Before contrast agent administration, discuss potential physical effects, such as ______ so that the patient is not surprised and upset during data acquisition.
warm sensation and metallic taste
CT scan manufacturers routinely include a variety of cushions, straps, and other safety devices that may be carefully used to help the patient hold still during data acquisition. These items are typically _______ and can be utilized in place of medical ta
nonabrasive
The breath-hold is another form of patient _____ required during many CT examinations.
immobilization
General practices necessary to obtain a good patient history include the following:
a. Non-leading or open-ended questions that allow the patient to provide the history in his or her own words. b. Keen listening and encouragement to maximize the information given. c. Focused questioning for additional information. d. Repeating and summar
_______ is the measurement of basic body functions to monitor critical information regarding the patient's physical condition.
Vital sign assessment
Vital signs are
temperature, pulse, blood pressure, and respirations:
Normal body temperature is
97.7 to 99.5 F or 36.5 to 37.5 C
b. Pulse rate for adults ranges from
60 to 100 beats per minute.
Pulse rate for children ranges from
70 to 120 beats per minute.
Systolic blood pressure indicates the
pressure within arteries during cardiac contraction
Systolic blood pressure should be less than
120 mm Hg.
Diastolic pressure should be
less than 80 mm Hg
Diastolic pressure is measured during
relaxation of the heart
Normal respiration rate for an adult is
12 to 20 breaths per minute
Normal respiration rate for a child is
20 to 30 breaths per minute
A pulse oximeter is an electronic device used to measure pulse and respiratory status.
Placed on a patient's finger, toe, or ear lobe, the _______ measures blood oxygen levels, which are normally between 95% and 100%.
pulse oximeter
pulse oximeter measures blood oxygen levels, which are normally between
95% and 100%
The _______ refers to the series of blood flow- related events that occur from the beginning of one heartbeat to that of the next
cardiac cycle
It is the frequency of the cardiac cycle that determines the patient's
heart rate.
______is a graphic representation of the electrical activity of the heart.
electrocardiogram ECG or EKG
It is used particularly during cardiac CT procedures to evaluate the heart rhythm and cycle
electrocardiogram ECG or EKG
The cardiac cycle can be divided into the following three distinct stages:
a. Atrial systole: � Contraction of the left and right atria. � Corresponds to the onset of the P wave of the ECG. b. Ventricular systole: � Contraction of the left and right ventricles. � Beginning of the QRS complex on the ECG c. Complete cardiac diasto
Cardiac CT images are typically reconstructed from data acquired during the
diastolic phase.
Patients with slower heart rates exhibit
longer diastolic phases,
Patients with slower heart rates exhibit longer diastolic phases, which yield
higher-quality cardiac CT exams.
b-Adrenergic receptor blocking agents b-blockers may be used to
reduce a patient's heart rate
_____ is the preferred rate for optimal imaging on most multislice CT (MSCT) systems.
Sixty-five beats per minute 65 bpm
Newer systems at the _______ are capable of acquiring adequate cardiac CT images at higher heart rates. This capability may preclude the need for pharmaceutical intervention as clinically indicated.
64-slice level and beyond
If not contraindicated, _______ may be administered just before the cardiac MSCT study to cause dilation of the coronary vessels, improving their visualization.
sublingual nitroglycerine
sublingual nitroglycerine
causes dilation of the coronary vessels thus improving their visualization.
Blood urea nitrogen (BUN) and creatinine level are
laboratory values used to indicate renal function
Blood urea nitrogen (BUN) and creatinine level values may be examined
individually or in ratio form,
as follows: a. Normal BUN values in adults range from
7 to 25 mg/dL.
By itself, ______ is not a sufficient indicator of renal insufficiency.
BUN Blood urea nitrogen
Normal creatinine levels range from _______ mg/dL. Range may also vary with lab reference.
0.5 to 1.5
An elevated creatinine value >1.5 mg/dL may not always indicate renal function compromise, because
this value can vary widely with different populations
The BUN/creatinine ratio may also be used to evaluate renal function. TRUE OR FALSE
TRUE
Normal BUN/creatinine ratio is approximately
6:1 to 22:1
______ is a more accurate measure of renal function.
Glomerular filtration rate (GFR)
______ is an approximation of creatinine clearance or the rate by which creatinine is filtered from the blood stream
GFR
______ is calculated using the patient's measured serum creatinine level and takes into account the patient's age, sex, and race
GFR
The normal range of GFR is
70 +/-14 mL/min/m2 for men and 60+/- 10 mL/min/m2 for women.
Prothrombin time (PT) is a
measure of blood coagulation.
The normal range for PT is approximately
12 to 15 seconds
Prothrombin time (PT) is measured in the lab after the addition of a protein called
tissue factor to a patient's blood sample.
Owing to the inherent differences in manufactured batches of tissue factor, the ______ is calculated to standardize PT results
International Normalized Ratio (INR)
The _____ compares a patient's PT with a control sample for a more accurate result
INR
The normal range for INR is
0.8 to 1.2
Normal range for clotting time is generally
25 to 35 seconds
Platelet count is also used to assess the patient's
clotting ability.
Normal platelet count is
140,000 to 440,000 per mm3 (or mL) of blood.
D-dimer testing is utilized for the diagnosis of
deep vein thrombosis (DVT) and pulmonary embolism.
Although nonspecific, the presence of elevated amounts of D-dimer in the bloodstream may indicate recently
degraded blood clots.
If the D-dimer value is elevated, additional testing such as _____ may be indicated.
CT angiography of the pulmonary arteries
Coumadin is a proprietary name for the generic drug
Coumadin AKA warfarin, an anticoagulant.
This drug is used to prevent the formation of blood clots in veins and arteries and may reduce the incidence of heart attack and stroke.
Coumadin AKA warfarin, an anticoagulant.
Patients undergoing therapy with warfarin or any other anticoagulant are prone to __________
Excessive bleeding due to trauma, including intravenous (IV) access for contrast agent administration.
The CT professional must take special precautions when providing care to the patient undergoing anticoagulant therapy. TRUE OR FALSE
TRUE
Adequate pressure must be applied to the site after IV removal to avoid excessive bleeding and bruising when providing care to the patient undergoing anticoagulant therapy. TRUE OR FALSE
TRUE
Metformin, also commonly referred to by the brand name Glucophage, is a drug used to treat
type 2 diabetes.
Patients are typically instructed not to take a metformin product for up to _____ following a contrast-enhanced CT examination.
2 days
There is a small risk of renal impairment from iodinated contrast agents, and reduced renal function can cause the potentially harmful retention of metformin within the body. TRUE OR FALSE
TRUE
The patient should consult the referring physician for instructions before resuming metformin treatment. A blood test to check renal function may be required. TRUE OR FALSE
TRUE
The injection of a medication or contrast agent directly into the bloodstream is a type of
parenteral administration.
Iodinated contrast agents are typically administered ______ during CT examinations.
intravenously
Sites commonly used for IV administration of radiopaque contrast agents include
The anterior recess of the elbow, or antecubital space. b. The radial aspect of the wrist. c. The anterior surface of the forearm. d. The posterior portion of the hand.
IV administration requires strict adherence to
standard precautions and aseptic technique.
Components of _______ include: a. Thorough hand washing between patients. b. Wearing of disposable gloves. c. Cleaning of the site of venipuncture in a circular motion with an alcohol swab, moving from the center to the outside d. Application of gentle pr
aseptic technique
Sterile technique refers to the practices and procedures used to maintain
a sterile, microorganism-free environment during invasive CT procedures such as biopsy, aspiration, and CT arthrogram.
_____ involves establishing a field around the area of interest that is free of all microorganisms.
Sterile technique
The procedure is performed within this sterile field with the use of sterile equipment and supplies.
Sterile technique
There are generally two approaches to IV administration of iodinated contrast agents, as follows:
a. Drip infusion
B. Bolus injection
the volume of contrast agent is administered at a slow rate over a long period. Because this method results in a slow rise in blood iodine concentration, it is no longer typically used in most CT procedures.
a. Drip infusion
whereby the iodinated contrast agent is "pushed" into the bloodstream at a rapid rate over a short period. This results in a sharp peak of iodine concentration in the blood, yielding a more pronounced pattern of contrast enhancement.
Bolus injection,
Bolus administration may be accomplished by ______ meaning that the volume of contrast agent is manually injected into the bloodstream
hand
Flow rates for injections through central venous catheters such as PICC lines are typically reduced to
well below 2 mL/sec
are commonly used for IV administration of contrast agents during CT examinations.
Automatic power injectors
are capable of consistently injecting large volumes of contrast agent at flow rates up to 5 to 6 mL/sec.
Power injectors
Power injectors are capable of consistently injecting large volumes of contrast agent at flow rates up to
5 to 6 mL/sec.
is determined by several factors, including clinical area of interest, contrast volume, venous access, patient condition, and pressure capacity of the IV materials utilized.
Flow rate
IV administration of contrast agent by power injector should be performed through
flexible plastic angiocatheters rather than standard metal needles
20-gauge or larger angiocatheters should be utilized whenever flow rates exceed
3 mL/sec.
should be utilized whenever flow rates exceed 3 mL/sec.
20-gauge or larger angiocatheters
Proper "bleeding" of the tubing eliminates air, and the injector syringe should remain in a _____ before administration of the contrast agent
downward position
During _______, CT image acquisition occurs at a single specific time during or after the injection of the contrast agent. Images are acquired in this fashion during a single period of contrast enhancement.
single-phase imaging
involves the acquisition of multiple series of CT images over timed intervals
Multiphase imaging
Automatic power injectors offer several advantages over manual injection of iodinated contrast during CT examination, including:
a. Consistent, reproducible flow rates. b. Precise volume/dosage control. c. Higher injection rates for optimal contrast enhancement. d. Automatic delays for proper enhancement patterns and multiphase imaging.
Flushing the tubing with a volume of saline _________ allows for a reduction of contrast agent dose and helps eliminate the streaking artifact that often results from a high concentration of iodine in the mediastinal vasculature
30-50 mL immediately after the contrast agent bolus
Flushing the tubing with a volume of saline 30-50 mL immediately after the contrast agent bolus helps eliminate the ______ that often results from a high concentration of iodine in the mediastinal vasculature
streaking artifact
The major disadvantage of the use of a CT power injector is the increased risk of _______ of the contrast agent outside the blood vessel.
extravasation, or infiltration
of contrast agent into the surrounding tissue is extremely painful and a potentially serious consequence.
Extravasation
Before the injection is initialized, the technologist should check venous backflow by drawing back manually on the injector and observing blood flow into the connective tubing. TRUE OR FALSE
TRUE
If venous backflow is not obtained, the catheter may need _______ and should be checked with a test injection of saline before contrast administration
repositioning
In the event of extravasation, the needle/catheter should be
removed, and pressure applied with a warm, moist compress
Intravascular RCM are generally administered in doses ranging from
50 to 150 mL
The positive contrast agents belong to a class of substances known as
radiopaque contrast media RCM.
The RCM typically used as for CT examinations are
iodine and barium
The degree of radiopacity exhibited by an iodinated contrast agent is ______ to the agent's concentration of iodine.
directly proportional
The degree of radiopacity exhibited by a barium contrast agent is ______ to the agent's concentration of barium.
directly proportional
Iodinated RCM are
water-soluble compounds that may be administered a. Generally into the bloodstream intravenously. b. Directly into a targeted vein or artery for localized enhancement. c. Directly into the intrathecal space during CT myelography. d. Into the joint space d
RCM is a Ionic contrast media which are salts consisting of
sodium and/or meglumine
Each molecule of ionic contrast agent consists of ______
three iodine atoms.
When injected into the bloodstream, each molecule dissociates into
two charged particles, or ions.
The production of osmotic ions is indicative of
high-osmolar contrast media (HOCM).
Examples of HOCM are
iothalamate meglumine aka Conray and diatrizoate sodium aka Hypaque
iothalamate meglumine aka Conray
diatrizoate sodium aka Hypaque
______ are non-salt chemical compounds that also contain three atoms of iodine per molecule.
Non-ionic contrast media
They do not dissociate in solution.
Non-ionic contrast media
The use of non-ionic or low-osmolar contrast media
LOCM significantly reduces the incidence of
adverse reaction in comparison with the of ionic
or high-osmolar contrast media HOCM
TRUE OR FALSE
TRUE
Although the likelihood of severe adverse reaction to ______, the exact incidence is not known.
LOCM is low
Non-ionic contrast media substances are commonly referred to as
low-osmolar contrast media (LOCM).
Examples of LOCM are
iohexol aka Omnipaque and iopamidol aka Isovue and ioversol aka Optiray
The majority of adverse reactions to iodinated contrast agents can be characterized as
mild and non-life-threatening.
Mild reactions to iodinated contrast media include:
a. Nausea/vomiting.
b. Mild urticaria (hives).
c. Pronounced sensation of warmth and/or
flushing.
d. Altered taste.
e. Sweats/chills.
f. Nasal stuffiness/sneezing.
g. Anxiety.
Mild reactions to iodinated contrast agents typically
require _____.The patient should be positively
reassured and closely observed until the symptoms
dissipate.
no treatment.
Moderate reactions are also usually _______
However, they may progress rapidly, so treatment
may be necessary.
non-life-threatening.
Moderate reactions to iodinated contrast include:
a. Mild bronchospasm.
b. Moderate to severe urticaria.
c. Vasovagal response.
d. Tachycardia from hypotension.
Treatment for moderate adverse reactions to iodinated contrast include:
a. Bronchodilator inhaler and/or oxygen therapy
for bronchospasm (wheezing).
b. Diphenhydramine (Benadryl) for urticaria.
c. Elevation of legs and IV fluids for hypotension.
Bronchodilator inhaler
Diphenhydramine
Elevation of legs
______ to iodinated contrast agents are
those that are potentially life-threatening and require
immediate treatment.
Severe reactions
______ reactions are rare.
Severe adverse reactions
They may begin with mild symptoms, such as anxiety
and respiratory distress, and then progress rapidly.
Severe reactions to iodinated contrast include:
a. Profound hypotension.
b. Laryngeal edema.
c. Severe bronchospasm.
d. Pulmonary edema.
e. Cardiac arrhythmia.
f. Seizure.
g. Cardiopulmonary arrest.
h. Death.
Newer low-osmolar contrasts such as ______ may also be used as oral/rectal contrast media for CT.
Iohexol is a contrast agent, sold under the trade names Omnipaque and Exypaque;
The osmolality of an iodinated radiopaque contrast medium greatly affects its potential for adverse effects in the patient. TRUE OR FALSE
TRUE
Non-ionic low-osmolar contrast agents are less likely to produce adverse side effects and/or reactions than ionic high-osmolar RCM. TRUE OR FALSE
TRUE
have the same osmolality as blood and therefore may offer improved patient comfort and a reduced potential for untoward side effects.
Iso-osmolar contrast media (IOCM)
Iodixanol AKA Visipaque is an example of a _____
non-ionic iso-osmolar contrast agent.
_______ are administered orally and/or rectally to opacify the GI tract.
Enteral RCM
Generally an enteral agent is either a
water-soluble iodinated solution or a suspension of barium sulfate
is an inert compound with excellent attenuation properties.
Barium sulfate
Routine transit time for barium sulfate through the GI tract is typically between
30 and 90 minutes.
may be used as an oral contrast agent to fill the GI tract.
Water
Advantages include of using Water is
Increased palatability and improved patient comfort
Water-soluble oral contrast media can also be either
high-osmolar or low-osmolar iodinated solutions.
Routine transit time for water-soluble iodinated contrast agents through the GI tract is typically between
30 and 90 minutes.
particularly of the low-osmolar type, are usually more palatable and result in less GI distress
Water-soluble oral contrast agents
Water-soluble oral contrast agents may be contraindicated in patients with known
iodine allergy.
Water-soluble iodinated solutions may be mixed with carbonated beverages to add negative contrast to the GI tract, improving the demonstration of
subtle disease.
The contrast agent used for rectal CT may be administered via enema to
opacify the distal large colon and rectum.
If complete distention of the stomach is clinically
necessary, the last dose of oral contrast agent may
be accompanied by a dose of
effervescent granules.
used to treat gas and acid indigestion
Effervescent granules
Effervescent granules used to treat gas and acid indigestion may also be administered as
negative oral contrast agents.
When swallowed, these Effervescent granules add negative contrast in the form of _______ allowing for better visualization of these structures.
gas to the stomach and proximal small bowel,
Air may also be administered via enema to insufflate the _______ to improve image quality during CT colonography
large bowel
Distention of the large intestine with room air or CO2 is necessary for optimal visualization of the
bowel wall
CT colonography may also involve insufflation of the large intestine with
CO2.
acts as a contrast agent during CT imaging of the chest much like it does on a chest radiograph.
Air
Negative Contrast Agents_____ may be used as negative contrast agents during CT examination
Air, gases, and water
______ may not be utilized in cases of suspected perforation because it may be toxic to the peritoneum.
Barium sulfate
is contraindicated in patients who are to undergo surgery or other invasive procedures of the abdomen and/or pelvis
Barium sulfate
can be potentially harmful if aspirated
Barium sulfate
Suspensions of barium sulfate are commonly employed as
positive contrast agents for opacification of the GI tract.
Contrast enhancement of vasculature greatly aids in the diagnosis of many disorders, including
aneurysm, thrombus, and stenosis
As the kidneys excrete the contrast agent, opacification of the renal collecting system occurs. This process improves visualization of the
renal pelvis, ureters, and bladder -KUB
______ is an important characteristic of an iodinated radiopaque contrast agent. It describes the agent's propensity to cause fluid from outside the blood vessel extravascular space to move into the bloodstream intravascular space
Osmolality
may be administered to opacify the small bowel during procedures such as CT enteroclysis and CT enterography
Neutral oral contrast agents
distend the GI tract while still allowing for clear visualization of the bowel wall
Neutral contrast media
such as VoLumen may be administered for detailed CT examination of the small bowel
Very low-density (0.1%) barium sulfate solutions
The IV administration of a contrast agent typically consists of an intravenous bolus injection through an
18- to 23-gauge angiocatheter or butterfly needle
is an IV catheter placed within a vein and used to administer fluids, medication, and/or contrast media.
angiocatheter
It consists of a small plastic catheter surrounding a solid needle that acts as a stylet to allow the catheter to be placed within a vein.
angiocatheter
Once the angiocatheter is inside the vessel, the needle is retracted and the catheter is advanced into the vein. TRUE OR FALSE
TRUE
The angiocatheter may be connected to a
contrast agent syringe or an automated contrast agent delivery system.
Connective tubing may be attached to facilitate the administration of fluids and/or medications with an
angiocatheter
Most current angiocatheters contain a _____ that guards against accidental sharps exposure
built-in safety shield or retraction mechanism
feature a reusable port device that allows the blunt plastic cannulas of syringes and connective tubing to be attached without needles
Needleless IV access systems
consists of a hollow needle surrounded by plastic flaps or "wings." The wings are grasped and lightly pinched together to facilitate insertion of the needle into a vein
A butterfly needle
The _____ is a measure of the amount of iodine within the bloodstream
serum iodine concentration
The range of serum iodine concentration for adequate opacification during CT examination is
2 to 8 mg/mL.
Common types of central venous catheters are
subclavian lines, implanted access ports, and peripherally inserted central catheters (PICC lines).
subclavian lines
implanted access ports
peripherally inserted central catheters (PICC lines).
should be tested for venous backflow and may require a test injection of saline for complete assurance.
Patency of central venous catheters
An example of oral contrast agent protocol for CT examinations limited to the abdomen is as follows:
a. 300 mL of oral contrast agent 30 minutes before scan. b. 150 mL of oral contrast agent immediately before scan
For CT examinations of the entire abdomen and pelvis, substantial opacification of the
stomach, small bowel, and proximal large bowel is typically required.
For CT examinations of the entire abdomen and
pelvis, substantial opacification of the stomach,
small bowel, and proximal large bowel is typically
required. An example protocol is:
a. 450 mL of oral contrast agent 60-90 minutes
before scan.
b. 300 mL of oral contrast agent 30 minutes before
scan.
c. 150 mL of oral contrast agent immediately
before scan.
For studies of the distal large bowel, including the
sigmoid colon and/or rectum, an oral contrast agent
may need to be administered
4 to 6 hours before
scan time to ensure sufficient opacification.
When this delay is not clinically appropriate, which is studies of the distal large bowel, including the
sigmoid colon and/or rectum an
oral contrast agent may be administered rectally, through an enema
A _______ enema is usually
sufficient to adequately opacify the rectum,
sigmoid, and distal large bowel.
150- to 300-mL CT contrast agent
A small amount of air aka negative contrast may also be administered rectally to improve
bowel distention when clinically indicated.
of an iodinated contrast agent is the injection of the agent directly into the
space surrounding the spinal cord.
Intrathecal administration
Intrathecal injections are performed during CT myelography for evaluation of the
spinal cord and nerve roots.
of a contrast agent is the injection of the agent directly into a joint space.
Intra-articular administration
Intra-articular injections are performed during CT arthrography of joints, including the
shoulder, wrist, and knee
four H's as outlined by the American
College of Radiology (ACR):
a. History:
b. Hydration:
c. Have equipment and expertise ready:
d. Heads up!
four Hs as outlined by the American
College of Radiology (ACR): History:
The CT professional should obtain a
thorough patient history. Details regarding the
patient's allergic and contrast agent history must
be reviewed.
four Hs as outlined by the American
College of Radiology (ACR): Hydration:
particularly with patients who may be
renally compromised, adequate hydration must be
ensured before, during, and after the examination.
four Hs as outlined by the American
College of Radiology (ACR):
Have equipment and expertise ready: A detailed
plan to treat contrast agent reactions should be
in place and should be practiced regularly.
four Hs as outlined by the American
College of Radiology (ACR): Heads up!
Constant assessment of the patient's
condition is vital for early identification and
proper treatment of an adverse reaction.
Patients with increased risk of adverse reaction to
iodinated contrast agents may be required to undergo
a
premedication regimen
The regimen typically consists of a combination of
an ______
antihistamine such as diphenhydramine HCL
Benadryl and a corticosteroid,
The regimen typically consists of a combination of
an antihistamine such as diphenhydramine HCL
(Benadryl) and a corticosteroid, taken at timed intervals
beginning as early as
24 hours before contrast
agent injection.
Physiologic and pathologic processes that may
increase the risk of adverse reaction from iodinated
contrast include:
a. Asthma.
b. Environmental and/or food allergies.
c. Renal disease.
d. Multiple myeloma.
e. Diabetes mellitus.
f. Pheochromocytoma is a rare, catecholamine-secreting tumor that may precipitate life-threatening hypertension
g. Sickle cell disease.
h. Hype
Contraindications to IV iodinated contrast agents include:
a. Allergy to iodine.
b. Prior severe allergic reaction to an iodinated
contrast agent.
c. Renal insufficiency/failure
Although iodinated contrast media are _______, pregnancy is not a direct
contraindication to their administration.
known to
cross the placental barrier
However, caution must be used in determining the potential
benefit of contrast agent administration in the pregnant
patient because
the risk of adverse reaction in
the fetus is unknown.
Nursing mothers may be injected with iodinated contrast
agents as clinically warranted. Caution again
must be exercised because many such agents are
excreted in
breast milk.
Nursing mothers are typically
instructed to pump and discard breast milk for
______ after administration of a contrast agent to
effectively eliminate risk to the infant.
24 hours
Delayed reactions to contrast agent administration can occur in a
small percentage of patients.
Common delayed reactions include:
a. Urticaria (hives).
b. Pruritus (itchiness).
c. Nausea/vomiting.
d. Drowsiness.
e. Headache.
Cutaneous reactions are the most common and can occur within
3 hours to 7 days after administration
of a contrast agent.
_______ is a potentially serious delayed effect of contrast agent administration.
Contrast-induced nephrotoxicity (CIN)
It is a considerable decline in renal function that can
occur after a patient receives an IV contrast agent
Contrast-induced nephrotoxicity (CIN)
CIN has varied definitions but is usually signified by a marked increase in _________ level over a
baseline measurement obtained before contrast
agent administration.
serum creatinine
The causative relationship between contrast agent administration and CIN is not completely understood but may be related to
renal vasoconstriction and/or the toxicity of the contrast medium itself
The overall risk of CIN is directly related to the patient's
preexisting renal function and hydration level.
Other risk factors for contrast-induced nephrotoxicity include:
a. Diabetes.
b. Myeloma.
c. Advanced age.
d. Cardiovascular disease.
Documentation within the patient's medical record must be
clear, concise, and recorded in a timely
manner
______ of the patient is the best
method of CIN prevention.
Adequate hydration
In the patient with normal renal function, the risk for development of CIN is
extremely low
A baseline serum creatinine measurement should be
obtained in all patients who are determined to be at risk for CIN.
TRUE OR FALSE
TRUE
Patients with non-insulin-dependent diabetes who are taking an _________ may also have a higher risk of CIN-related effects.
oral biguanide AKA metformin drug
Patients receiving metformin drug therapy are at
increased risk for _________, a condition that
may be exacerbated by renal insufficiency.
lactic acidosis
Patients who have associated risk factors for renal insufficiency and are currently taking a metformin drug are typically instructed
not to take the metformin following the contrast study.
______ may be necessary before the patient resumes metformin therapy.
A lab test of renal function
All information regarding patient care, including
the procedure(s) performed, contrast/medication
administered, untoward event(s), and final outcomes
must be documented by the
practitioner.
The factors affecting CT patient radiation dose can be divided into the following categories:
a. System configuration.
b. User settings.
The individual technical configuration of a CT system determines several characteristics that may affect patient dose:
.
a. Source-detector distance:
b. Filtration
c. Detector efficiency
d. In order to expose the widened detector array
equally, MSCT utilizes a cone-shaped beam,
instead of the fan-shaped beam traditionally used
by single-slice CT (SSCT) systems.
e. Overrangi
________: As the distance from
the x-ray tube to the detectors decreases, dose
increases
Source-detector distance
Filtration within the CT x-ray tube varies
between approximately _______
(Al) or equivalent material.
6 and 9 mm aluminum
Filtration acts to remove the
unwanted, "low-quality" portion of the x-ray beam that adds to the patient radiation dose while failing to yield useful acquisition data.
_______ are also added to the x-ray tube to compensate for the noncylindrical nature of most body shapes.
beam-shaping or bow-tie filters
Additional filtration material along the ______ thereby reducing the overall
patient dose.
periphery
of the x-ray beam absorbs radiation where it is
not necessary,
Detector efficiency plays an important role in
patient radiation dose and can be described in
several ways:
� The inherent absorption efficiency of each
detector element
� The geometric efficiency of a detector array
_______ describes the ability of the
detector to capture transmitted x-ray quanta
and produce the appropriate response.
The inherent absorption efficiency of each
detector element
Inefficiency with The inherent absorption efficiency of each detector element
here can result in
the loss of data and a
subsequent compensatory increase in patient
dose.
The ________
describes the spatial arrangement of detector
elements, including the amount of interspace
material required between adjacent elements.
geometric efficiency of a detector array
The interspace material absorbs transmitted
radiation but yields no response. This results
in a loss of acquisition data (signal) and
requires an _______ to compensate.
increase in radiation dose
geometric efficiency of a detector array is of particular importance in
________, in which the complex arrangement
of multiple rows of detectors requires
increased interspace material, resulting in a
reduction in geometric efficiency.
MSCT
In order to expose the widened detector array
equally, _________
instead of the fan-shaped beam traditionally used by single-slice CT (SSCT) systems.
MSCT utilizes a cone-shaped beam,
fan-shaped beam are traditionally used by
single-slice CT SSCT systems.
Some CT manufacturers
employ ________ to finely control the position of the x-ray beam on the detectors, reducing overbeaming and subsequent
radiation exposure.
focal spot tracking systems
All detectors
of the array must be exposed to x-radiation of
equal intensity. TRUE OR FALSE
TRUE
The beam must be expanded
even further to avoid exposing the detectors to
undesirable "penumbra." This process is referred
to as
overbeaming.
CT image data acquired
from only a portion of the exposed detector
array results in a radiation dose to the
patient that
does not contribute to the formation
of the CT image.
_____ occurs when radiation dose is
applied before and after the acquisition volume to ensure sufficient data collection for the interpolation
algorithms inherent in spiral CT.
Overranging
During Overranging Up to a half rotation
both before and after the spiral scan are
common and
add to the patient radiation dose.
________
are employed during the reconstruction process
to reduce displayed noise within the CT image.
Noise reduction algorithms, or adaptive filters,
Reduction of displayed noise allows for ____________ during data
acquisition.
lower mAs milliampere-seconds settings
Use of an MSCT rather than an SSCT system is
associated with several technical pitfalls with the
potential to
increase the patient radiation dose.
Dose can be considerably higher with MSCT
because of:
a. Decrease in the focal spot-detector distance.
b. Use of a cone beam instead of a more z-axis-
collimated fan beam.
c. Increases in the number of phases of acquisition
enabled by decreased scan times.
d. Use of thinner section widths for improvement of
Scanning parameters should be routinely adjusted
in an effort to minimize patient radiation dose.
Adjustments should consider the
exam indication, region(s) of interest, and patient's age and body habitus.
________ is the process of adjusting
parameters such as mA/kVp, slice thickness, and
pitch for the purpose of reducing patient radiation
dose while maintaining adequate image quality.
Protocol optimization
In certain applications, such as _________ reduced kVp settings may be used without a loss in image quality, resulting in a dose reduction.
pediatric scanning and CT angiography,
There is a ___________
between the milliampere (mA) setting, scan time,
and patient radiation dose. For example, if the
mAs value is doubled, the patient radiation dose is
doubled
directly proportional relationship
During CT data acquisition, the section of the
patient exposed to radiation may be referred to as
the
dose profile.
As measured at the isocenter of
the gantry, the longitudinal AKA z-axis dimension of the
dose profile is directly controlled by
collimation of the x-ray beam.
When only a single slice is scanned, an increase in
collimation thinner section width will result in a
decrease in patient radiation dose. However, CT examinations rarely consist of a single slice.
Increases in collimation (i.e., thinner slices)
yield images with
more noise
Within the context of the standard CT examination,
collimation may ______ affect patient radiation
dose.
indirectly
Although usually unnecessary, it is common practice for the user and/or system to compensate for the resultant noise generated by thin sections with an
increase in mA, thereby increasing patient dose.
During multidetector CT AKA MDCT wider collimation
results in
improved dose efficiency because less overbeaming occurs.
During multidetector CT AKA MDCT Narrow beam widths, i.e., thin slices,
increase overbeaming and reduce dose
efficiency.
Although reconstruction algorithm AKA kernel and
window width and level settings are ______ primary
controllers of patient radiation dose, they can play
an indirect role.
not primary controllers of patient radiation dose,
Noise levels in the CT image are a
function of
dose
Decreased dose typically yields
an
increase in image noise.
Displayed noise can be
reduced with the utilization of an appropriate
reconstruction algorithm, or kernel.
Also, displaying
the reconstructed image with the correct window
settings can help___________Both of these solutions are
alternatives to increasing the patient dose.
reduce the low image qualities inherent with noise.
Image noise is directly related to
patient size
As a patient size decreases,
noise decreases
_______ should include size-based dose mAs adjustments. For example, optimal scans in children
can be acquired with a substantially lower radiation
dose than scans in larger patients.
Protocol optimization
For example, during renal stone survey
scans of the abdomen and pelvis, more noise can
be tolerated because of the
high inherent contrast of the pathology in question.
During SSCT, pitch values ________ allow for
the acquisition of a given scan volume in a shorter
time, resulting in a reduction in patient radiation
dose.
greater than 1
However, an increase in pitch during MSCT results
in a marked __________ It is typically
compensated for by an _________, yielding
little net improvement in patient radiation dose.
increase in image noise/increase in mA
Automatic tube current modulation
aka ATCM can occur as either:
a. Angular (x- and y-axis) tube current modulation,
b. Longitudinal (z-axis) tube current modulation,
___________
whereby the mA setting is adjusted according to
the difference in thickness of the part as the tube
rotates.
Angular aka x- and y-axis tube current modulation,
For example, during imaging of the oval
torso, mA can be reduced as the beam passes
from anterior to posterior. Less attenuation
occurs in the AP path than in the lateral path
through the patient.
Angular aka x- and y-axis tube current modulation,
_______
which allows for the adjustment of the mA setting as the scan proceeds along the z-axis of
the patient.
Longitudinal aka z-axis tube current modulation,
Radiation dose reduction is maximized in CT scanners that employ both the
angular and longitudinal
current modulation techniques.
The potential radiation dose savings gained with
ECG-triggered tube current modulation depend on
the
patient's heart rate. As heart rate increases, the radiation dose savings decrease.
_________ is reduced during the cardiac phase
not utilized for image reconstruction.
Tube current
_________ allows for
pulses of x-ray energy rather than continuous
exposure to be used.
ECG-triggered tube current modulation
_________, prospective gating
can be used to reduce the patient radiation dose.
During MSCT cardiac studies
________
whereby the mA setting is adjusted according to
the difference in thickness of the part as the tube
rotates.
Angular (x- and y-axis) tube current modulation,
The modern CT scanner comes equipped with a
form of ________ to manage
patient radiation dose on the basis of the size,
density, and overall attenuation of the part being
examined it is called
Automatic tube current modulation aka ATCM
Radiation protection in CT should follow the
ALARA as low as reasonably achievable concept.
Radiation protection of the CT patient should also encompass three general principles:
a. Strict clinical indication.
b. Protocol optimization.
c. Shielding.
Limiting CT examination to_______ is the
best way to reduce radiation exposure.
strict indications
_________ should be held at a
minimum
Multiple phase acquisitions
An __________ is one that acquires CT
images with acceptable levels of noise at the lowest
possible dose.
optimized protocol
Shielding of radiosensitive tissues, such as the
eye lenses, breasts, and gonads, is critical.
_________must be applied both above and below the
patient, to account for the rotational nature of the
exposure in CT.
Shielding
____________ of particularly radiosensitive
areas, such as the orbits, thyroid, and
breast tissue, can substantially reduce the effective
radiation dose.
In-plane bismuth shielding
Room shielding requirements must be evaluated by
a
qualified radiologic health physicist.
Consideration for shielding requirements should account for
exam workload, scanner position, and
construction of doors, windows, and so on.
_______ may be used to
describe the reconstructed CT section.
Slice sensitivity profile AKA SSP
However, the section of tissue exposed to ionizing radiation, or _______, is greater in width than the SSP.
dose profile
______ is the term used to describe the ability of x-rays to ionize a volume of air.
Exposure
It is measured in
roentgens (R).
Exposure
________ describes the amount of x-ray energy
absorbed in a unit of mass. It is measured in grays (Gy).
Absorbed dose
Kerma may also be used to describe
absorbed dose
_______ describes the amount of radiation
absorbed in a quantity of air.
Air kerma
________ accounts for the type of tissue that the radiation is deposited in.
Effective dose
Different tissues are assigned weighting factors based on their individual
radiosensitivity
Effective dose approximates the
relative risk from exposure to ionizing radiation. It is measured in
sieverts (Sv)
The__________ is an approximate measure
of the dose received in a single CT section or slice.
CT dose index (CTDI)
CTDI is calculated for the central slice in a series that is surrounded by _________
seven slices on each side.
_________ is measured by performing scans of both
head- and body-sized CT phantoms using specific
technical parameters.
CTDI
______ is placed within each phantom during
the scans.
A thermoluminescence dosimeter
(TLD)
Because of absorption, dose varies within the CT image across the acquired field of view. CTDIw is an internationally accepted, weighted dose index. It is calculated by ______
summing two-thirds of the exposure
The exposure measured by the TLD is used to calculate the
CTDI for each acquisition.
Exposure from the scan is measured by the TLD, and the
CTDI is calculated from those measurements.
________ is a fixed measurement taken with a 100-
mm-long pencil ionization chamber and makes no
reference to a specific number of slices.
CTDI100
________ is an internationally accepted, weighted dose index.
CTDIw
CTDIw calculated by summing ________
two-thirds of the exposure recorded at the periphery of the field with one third of the centrally recorded dose.
This weighting yields a more accurate dose approximation.
CTDIw
________ is placed within each phantom during
the scans.
tld thermoluminescent dosimeter
CTDIw is calculated from measurements made with
TLDs positioned at the
center and periphery of the phantom to account for the variance in dose distribution.
The CTDIw is measured utilizing a ________ and does
not account for the affects of helical scanning on
patient radiation dose.
conventional step-and-shoot mode of axial CT scanning
CTDIvol is used to approximate the radiation dose for each section obtained during a
helical scan.
CTDIvol = CTDIw/pitch
It corresponds to the axially acquired CTDIw
divided by the helical pitch, as follows:
As the pitch increases, the ______
dose per section AKA CTDIvol decreases
helical pitch AND CTDIvol Have what type of relationship
indirect relationship
CTDIw approximates dose along the ______
x- and y-axes of the acquired CT image.
______ also includes the dose along the z-axis of the scan acquisition; it is given in units of milligrays (mGy).
CTDIvol
CTDIvol is similar in principle to an older term used
for conventional step-and-shoot scanning, ______
multiple scan average dose AKA MSAD
______ is a calculation of the average cumulative
dose to each slice within the center of a scan consisting
of multiple slices.
multiple scan average dose AKA MSAD
The ______ is higher than the dose from an acquisition
of a single slice, because of the contribution of
scatter radiation.
multiple scan average dose AKA MSAD
The doses at the beginning and end slices in a series
are slightly less, owing to the lack of dose from their
outer sides using what principle ______
multiple scan average dose AKA MSAD
multiple scan average dose AKA MSAD may be calculated for axial scanning as follows:
MSAD=T/I X CTDI
where T is slice thickness and I is increment or
image spacing.
______ accounts for the affects of image spacing or
bed index on the patient dose during axial scanning.
multiple scan average dose AKA MSAD
During axial scanning, ______ increase
the patient radiation dose, whereas gaps between
slices decrease it.
overlapping scans
multiple scan average dose AKA MSAD increases when slice thickness is greater than
image spacing� ______
overlapping scans.
multiple scan average dose AKA MSAD decreases when slice thickness is less than
the bed index�______
noncontiguous scans.
When slice thickness equals the bed index, ______
multiple scan average dose AKA MSAD is equal to CTDI.
During spiral or helical scanning, multiple scan average dose AKA MSAD is controlled
by pitch, as follows:
MSAD= CTDI/pitch
where pitch is the amount of table travel per tube
rotation divided by the collimation.
______ is most accurate at the center of a scan
series.
multiple scan average dose AKA MSAD
At either end of an acquisition, multiple scan average dose AKA MSAD tends
to ______
overestimate patient radiation dose.
Both CTDIvol and multiple scan average dose AKA MSAD are used to approximate
average radiation dose within a scan volume. ______ is not considered.
Total scan length along the z-axis
Therefore, neither provides an estimate of the total
dose along a given scan volume
CTDIvol and multiple scan average dose AKA MSAD
Dose length product (DLP) is an internationally
accepted measure of CT patient dose defined as:
DLP = MSAD X slice width (cm) X No: of slices in scan volume
Dose length product (DLP) slice again equals ______ and not the reconstructed slice thickness.
pre-patient collimator setting
The DLP can also be illustrated as the product of
CTDIvol and scan length and is given in units of
milligray-centimeters mGy-cm
as follows:
DLP x CTDIvol scan length
When evaluating patient radiation dose from a
multiple scan average dose AKA MSAD study, one must bear in mind that CTDIvol
is still controlled by the ______ regardless of the number of reconstructed slices.
pre-patient collimator setting,
Because direct measurement of effective dose from
CT is not possible, estimations must be made on
the basis of exposure to a ______ .
phantom
Once the air kerma or absorbed dose in a phantom is measured, an ______ .
estimate of effective dose can be calculated.
It is important to remember that ______
do not account for patient size and so overestimate
the radiation dose to the larger patient and underestimate
the dose to the smaller patient.
CTDIvol and DLP
CTDIvol and DLP may also be expressed by the
newer terms
computed tomography air kerma
index (Ca) and air kerma length product (Pkl),
respectively.
A dose gradient exists across the ______
field of view FOV of the CT image.
______ can be markedly greater than
that at the center of the image, along the x- and
y-axes.
Dose at the periphery
The magnitude of this gradient is size dependent.
The difference in absorbed dose is ______
greater in larger patients
Smaller adults and pediatric patients exhibit______
little to no radial dose gradient
For smaller patients, the entrance radiation and exit
radiation are ______
equal in intensity, resulting in a more
uniform distribution of dose.
Recommendations for the reduction of pediatric
dose include: ______
a. Eliminate CT scans for inappropriate indication.
b. Reduce multiphase scanning (pre-contrast,
delays, and so on).
c. Reduce mA.
d. Increase pitch.
9. Regardless of age, the CT protocol should be optimized
on the basis of the individual patient's size
This difference in dose distribution illustrates the
importance of ______
dose reduction for the smaller, i.e., pediatric, patient.
When all other technical factors remain constant,
absorbed dose ______
is greater in the smaller patient.
______ was developed by the
Alliance for Radiation Safety in Pediatric Imaging
and sponsored by the Society for Pediatric Radiology
(SPR).
The Image Gently campaign
The widely recognized campaign offers
guidelines to help reduce pediatric radiation exposure
from CT imaging. Like the dose reduction techniques
listed here, the Image Gently guidelines
suggest that:
a. mA and kVp should be "child-sized."
b. One single-acquisition phase is often enough.
c. Only the indicated area should be scanned.
and/or weight.
CHAPTER 2 MOSBY COMPLETED
CHAPTER 2 MOSBY COMPLETED
BEGINING CHAPTER 3
Review of Imaging Procedures
in Computed Tomography
BEGINING CHAPTER 3
Review of Imaging Procedures
in Computed Tomography
Axial plane computed tomography (CT) images are
acquired ______ to the infraorbital-meatal line
IOML on the sagittal localizer scout, topogram
image.
parallel
Acquisition may be performed at an angle ______
, parallel to the skull base, to reduce orbital dose and minimize ______ artifact (Figs. 3-1 to 3-5).
15 degrees above the IOML/beamhardening
The axial aka sequential mode of data acquisition is
used for improved ______
z-axis resolution.
Thin sections aka ______ are acquired from the skull base through the posterior fossa, then ______ through the vertex
2-5 mm/5- to 10-mm sections
Thinner sections through the posterior fossa reduce ______ caused by the petrous pyramids
beam-hardening artifact
Thinner sections through the posterior fossa reduce beam-hardening artifact caused by the ______
petrous pyramids
The excellent z-axis resolution of thin-section volumetric
multidetector CT MDCT studies allows for high-quality helical examinations of the ______
brain
______ may also be preferred whenever multiplanar reformation MPR or three-dimensional 3D imaging is anticipated or when exam speed is a critical issue.
Helical volumetric acquisition
A standard or soft tissue reconstruction algorithm ______
is used.
filter, kernel
Additional image reconstruction with a ______ may be used to maximize bony detail for suspected fractures or other
skeletal anomalies.
high spatial frequency bone algorithm
an inadequate blood supply to an organ or part of the body, especially the heart muscles.
Acute ischemia
Sample window level WL and width WW settings
for optimal image display of various structures
or irregularities of the Brain are as follows:
Acute ischemia: variable, high contrast
windowing improves the CT visualization
of acute stroke
WL 35, WW 25
Sample window level WL and width WW settings
for optimal image display of various structures
or irregularities of the Brain are as follows:
Gray/white matter:
WL 35, WW 100
Sample window level WL and width WW settings
for optimal image display of various structures
or irregularities of the Brain are as follows:
Hemorrhage/hematoma:
WL 75, WW 150.
Non-contrast CT examinations of the brain are routinely
indicated for trauma to diagnose ______
intracranial hemorrhage or hematoma.
Administration of contrast media in the trauma patient is initially contraindicated because contrast enhancement may mask subtle signs of ______
hemorrhage
Unenhanced CT of the brain is also typically the
first component of a comprehensive protocol for
the evaluation of ______
acute stroke.
Hemorrhage must be first excluded on the non-contrast images obtained before ______
thrombolytic therapy.
Sample window level WL and width WW settings
for optimal image display of various structures
or irregularities of the Brain are as follows:
Bone:
WL 400, WW 3000.
Unless contraindicated, IV administration of an
iodinated contrast agent is essential in cases of
arteriovenous malformation, suspected neoplasm, or
attention to the pituitary gland.
arteriovenous malformation
suspected neoplasm
pituitary gland
______ may be performed through the pituitary gland.
Coronal plane, thin-section 1-3 mm helical imaging
CT studies of the temporal bones and internal auditory
canal require a high-resolution imaging technique,
which consists of the following:
a. Thin slices.
b. Small targeted display field of view aka DFOV
c. High-resolution reconstruction algorithm.
Thin sections 1-2 mm are obtained in both the ______ for temporal bone
axial and coronal planes
Multislice CT MSCT axial acquisitions allow for isotropic MPR, which can eliminate the ______
added patient radiation dose from direct coronal acquisition.
Targeted thin-section ______ should be performed ______ utilizing a small DFOV or increased zoom factor to maximize resolution of the small bony components of the inner ear.
1-2 mm reconstructions /bilaterally
CT images of the temporal bones are reconstructed
with a ______
high spatial frequency bone algorithm.
CT images of the temporal bones requires patient must be instructed to ______ because even the slightest motion may cause severe image degradation.
hold completely still,
CT examinations of the temporal bones are typically
performed * ______ , although IV
contrast media may be indicated in cases of suspected
soft tissue neoplasm, vascular anomalies, and so on.
without contrast enhancement
For imaging of the orbits, axial plane, thin-section
1-3 mm images are acquired ______
parallel to the IOML
For imaging of the orbits Direct thin-section 1-3 mm coronal images may be acquired ______ to the axial plane
perpendicular
For imaging of the orbits The acquisition angle may be adjusted slightly to avoid ______
streaking from metal dental apparatus.
For imaging of the orbits MSCT axial acquisitions allow for ______ , which can eliminate the added patient radiation dose from direct coronal acquisition.
isotropic MPR
For imaging of the orbits ______ is used.
A standard or soft tissue reconstruction algorithm
For imaging of the orbits Additional image reconstruction with a high spatial frequency bone algorithm may be used for ______
trauma indications.
For imaging of the orbits, Sample WL and WW settings for optimal image display are: Soft tissue:
WL 40, WW 400.
For imaging of the orbits, Sample WL and WW settings for optimal image display are Bone:
WL 400, WW 3000
CT examinations of the sinuses should include ______
axial images parallel to the hard palate
CT examinations of the sinuses Acquisition should extend inferiorly and anteriorly to include the ______
maxillary and ethmoid sinuses,
CT examinations of the sinuses Acquisition should extend superiorly to include the ______
frontal sinus, and posteriorly to
include the sphenoid sinus
CT examinations of the sinuses Direct coronal imaging ______ to the axial plane may be obtained with the patient in the ______
perpendicular/prone position.
CT examinations of the sinuses The ______ with the head dropped back may also be used.
supine position
CT examinations of the sinuses MSCT axial acquisitions allow for ______ , which can eliminate the added patient radiation dose from direct ______
isotropic MPR /coronal acquisition.
CT examinations of the sinuses However, the additional ______ may be valuable in demonstrating ______
coronal position/changing air-fluid levels and other sinus-related disease.
CT examinations of the sinuses:Coronal plane imaging best visualizes the ______ , a common site for sinus inflammation.
osteomeatal complex
CT examinations of the sinuses : Sagittal MPR images are also useful for demonstrating the ______
osteomeatal complex
CT examinations of the sinuses : Sample WL and WW settings for optimal image display
are:Soft tissue: ______
WL 40, WW 400.
CT examinations of the sinuses : Sample WL and WW settings for optimal image display
are: Bone:
WL 400, WW 3000.
CT examinations of the temporomandibular joints
TMJ also include axial and coronal thin sections
1-3 mm
CT examinations of the temporomandibular joints Images may be acquired in both the ______ , as clinically indicated.
open-mouth and closed-mouth positions,
Examinations of the sinuses and facial bones are
usually performed ______ , except in cases of suspected neoplasm.
without IV contrast media,
The administration of IV iodinated contrast media
during CT examinations of the head has multiple
indications, including:
a. Neoplasm.
b. Inflammatory processes.
c. Vascular abnormalities.
Administration of an iodinated contrast agent ______,
thereby increasing contrast and CT visualization.
raises the attenuation values of normal brain gray matter
A contrast agent enhances an ______
that has disrupted the normal blood-brain barrier.
intracranial neoplasm
Total volumes of non-ionic contrast agents typically
range between ______, according to study
type, patient weight, renal function, and so on.
75 and 150 mL
Injection rates vary from less than ______ during
general examinations of the brain to upwards of
______ during angiographic or perfusion studies.
1 mL/sec TO 4 mL/sec
Scan timing for general contrast-enhanced studies of
the brain is not as critical as in other applications. In
fact, delays of up to ______ may be utilized to maximize sensitivity of the CT scan to detect neoplasm.
5 minutes
Although they do not form part of the circle of
Willis, the ______ are also of importance during CTA imaging of the brain and its blood supply.
basilar artery and middle cerebral
arteries
The vascular components of the circle of Willis are
as follows:
a. Right and left anterior cerebral arteries.
b. Anterior communicating artery.
c. Right and left internal carotid arteries.
d. Right and left posterior cerebral arteries.
e. Right and left posterior communicating arteries.
CTA of the brain is used to identify and evaluate
cerebral aneurysm, intracranial thrombosis, traumatic
cerebrovascular injury, arteriovenous malformation,
and stenosis.
Thin-section 0.5-1.5 mm helical acquisition is
performed in the ______ direction from the
level of the second cervical vertebra C2 to at
least 1 cm above the dorsum sella.
caudocranial
CT systems with sufficient technical capabilities 16-slice or greater may extend the acquisition through the vertex.
TRUE OR FALSE
TRUE
The CTA spiral acquisition is then made during a
rapid bolus infusion of iodinated contrast agent at
a rate of ______
3 to 4 mL/sec.
Brain CT angiography CTA
a. Use of an empiric delay of ______
12 to 20 seconds.
Brain CT angiography CTA
b. Performing a bolus-timing sequence, whereby
multiple scans through the ______ are
acquired during a test bolus. The proper delay
can be determined by visually identifying the
time at which peak vessel enhancement occurs.
cranial vessels
Brain CT angiography CTA
c. Use of ______that monitors vessel opacification during
contrast agent administration. The scan automatically
begins once a predetermined Hounsfield
unit (HU) value of attenuation within the target
vessel(s) is reached.
automated triggering, or bolus-tracking
software
Brain CT angiography CTA Thin sections are reconstructed with a ______
minimum 50% overlap to maximize the quality of MPR and 3D images
Brain CT angiography CTA 3D techniques such as ______
maximum intensity projection MIP, surface rendering, and volume rendering are employed
Protocols for brain CTA depend strictly on the technical
capabilities of the CT system employed. Example
technical parameters for a CTA of the brain
circle of Willis using a 64-slice system are:
a. Performance of a standard non-contrast axial
brain sequence first.
b. 50 to 75 mL of a non-ionic contrast agent at
4 mL/sec 15- to 20-second scan delay
c. Helical CT acquisition with 0.625-mm collimation.
d. 120 kVp/300 mA/0.4 sec.
e. Overlapping 0.75-
Protocols for brain CTA: For evaluation of acute stroke, both the intracranial and extracranial vessels are included in the CTA acquisition, which extends from the ______
aortic arch through the circle of Willis.
CT angiography source images CTA SIs can be
utilized to produce ______, which may
provide valuable information about acute brain
infarct. The maps are obtained by subtracting the
unenhanced CT brain images from the contrast enhanced
CTA source images.
subtraction maps
CT Perfusion of the Brain
1. The comprehensive MSCT management of acute
stroke consists of:
a. Pre-contrast head CT.
b. CTA of the brain and carotid arteries.
c. CT perfusion CTP imaging.
Cerebral perfusion refers to the ______
level of blood flow
throughout brain tissue.
CT perfusion evaluates cerebral perfusion by monitoring
the ______
initial passing of iodinated contrast media
through the vasculature of the brain.
The factors used to describe cerebral perfusion are
as follows:
a. Cerebral blood volume CBV: The quantity of
blood (in mL) contained within a 100-g volume
of brain tissue ______
Normal range is 4 to 5 mL/100 g.
The factors used to describe cerebral perfusion are
as follows:
b. Cerebral blood flow CBF: The quantity of
blood (mL) that moves through 100 g of brain
tissue each minute ______
Normal range in gray matter is 50 to 60 mL/100 g/min.
The factors used to describe cerebral perfusion are
as follows:
c. ______ : The average transit
time, in seconds, for blood to pass through a
given region of brain tissue. MTT varies according
to the distance traveled between arterial
inflow and venous ou
Mean transit time MTT
The central volume principle illustrates the relationship
between these factors as follows:
CBF = CBV/MTT
The primary indication for CTP is for the evaluation
of ______
acute stroke.
The primary goal of CTP is to identify and differentiate
the ______
infarct core and the penumbra.
Brain tissue within the infarct core is beyond repair
by ______
thrombolytic therapy.
The ______ is the ischemic yet still viable tissue
immediately surrounding the infarct core.
penumbra
The ______ can be described as the region of
ischemic brain parenchyma where CBV is still contain a major intracranial artery for accurate CTP map reconstruction.
penumbra
Ischemic tissue demonstrates a ______ in comparison with normal brain tissue.
greater than 34% decrease in blood flow
______ are placed over a well-opacified artery and an area of venous outflow, for example, the anterior cerebral artery and superior sagittal sinus, respectively.
Region of interest ROI measurements
Computer software utilizes the ROI information to
generate ______
color-coded CBF, CBV, and MTT maps.
The mathematical technique utilized for generation
of perfusion maps is referred to as ______
deconvolution.
______ is performed with the inhalation administration of a nonradioactive isotope of xenon Xe gas.
Xenon CT perfusion Xe-CT
The xenon enters the bloodstream and can be used to ______
calculate a brain perfusion map on the basis of cerebral blood flow.
Helical axial plane images of the soft tissue of the
neck are acquired from the ______
superior orbital rim inferiorly through the lung apex
The gantry should be angled to avoid streak artifact
from dental hardware, as follows:
greater than ______
2.5 mL/100 g.
Brain parenchyma with a CBV ______ is identified as the infarct core.
less than 2.5 mL/100 g
CTP imaging of the brain generates quantitative
maps of ______. These maps can help
distinguish regions of ischemic penumbra from an
infarct core.
CBF, CBV, and MTT
Technical Considerations for Soft Tissue of the Neck:
The technical procedure for CTP brain acquisition
and quantitative display includes:
a. Bolus administration of ______
50 mL of a contrast agent at a rate of 4 to 7 mL/sec.
Technical Considerations for Soft Tissue of the Neck:
b. Cine acquisition of at least ______
to allow for complete tracking of the first pass
of the contrast agent through the intracranial
vasculature.
at least 2 cm of applicable
brain region over a period of 45 to 60 seconds
Technical Considerations for Soft Tissue of the Neck:
c. The acquisition may be broken down into multiple
slabs for greater coverage. Each slab must
a. From the superior orbital rim to the hard palate,
the gantry may be angled superiorly, parallel to
the hard palate.
superior orbital rim
Technical Considerations for Soft Tissue of the Neck:
The remainder of the acquisition is acquired with
the gantry angled ______
parallel to the mandibular body.
Technical Considerations for Soft Tissue of the Neck:
The two scan groups should overlap slightly to
ensure complete coverage of the ______
posterior skull base and neck.
Technical Considerations for Soft Tissue of the Neck:
The patient is supine with the arms relaxed ______
caudally to
reduce artifact from the thicker area of the shoulders.
Technical Considerations for Soft Tissue of the Neck:
An increase in mAs may be required to adequately
demonstrate the ______
lower neck and thoracic inlet as the patient dimension increases through the shoulders.
Technical Considerations for Soft Tissue of the Neck:
Slice thickness of ______ is adequate for most
CT studies of the soft tissue neck.
3 to 5 mm
Technical Considerations for Soft Tissue of the Neck:
Thinner sections ______ may be employed for detailed examinations of the larynx or CT angiographic studies of the neck vasculature.
0.5-2 mm
Technical Considerations for Soft Tissue of the Neck:
A medium to large scan field of view SFOV is
required to accommodate the variation in part size
as the scan progresses from the ______
skull base through the thoracic inlet.
thoracic inlet.
Technical Considerations for Soft Tissue of the Neck:
The DFOV typically ranges between ______
and should be tailored to individual patient size.
18 and 25 cm
Technical Considerations for Soft Tissue of the Neck:
Sample WL and WW settings for optimal image display
are:
a. Soft tissue: WL 50, WW 400.
Technical Considerations for Soft Tissue of the Neck:
Sample WL and WW settings for optimal image display
are:
b. Bone: WL 300, WW 2000.
Technical Considerations for Soft Tissue of the Neck:
The patient should be instructed to
breathe quietly and to suspend swallowing during data acquisition.
Technical Considerations for Soft Tissue of the Neck:
Clinical indications for CT examination of the soft
tissues of the neck include:
a. Inflammation or swollen glands.
b. Infection or abscess.
c. Malignant neoplasms, such as carcinoma, sarcoma,
and parotid gland tumor.
d. Benign masses such as cysts and lipomas.
e. Lymphadenopathy.
f. Trauma.
g. Endocrine pathology involving the thyroi
Larynx: The patient is positioned supine with the head
extended to place the plane of the larynx ______
perpendicular to the CT image
The MDCT carotid angiogram typically includes
from the ______.
aortic arch to the skull base
If the intracranial vessels circle of Willis are to be evaluated, the acquisition proceeds to at least ______. The scan extent may be limited as
required by the clinical indication and the CT system
capabilities.
1 cm above the dorsum sella
The mA value is system dependent but should be
kept at the minimal allowed to reduce patient radiation
dose. The typical range is
300 to 400 mA for sub-second scan rotation.
The MDCT carotid angiogram: Utilizing a reduced kVp setting of ______ can improve the visualization of vessel opacification by an IV contrast agent.
120 rather than 140
The MDCT carotid angiogram: When possible, the gantry should be ______ to avoid artifact from dental hardware
angled
The MDCT carotid angiogram: The CTA spiral acquisition occurs during a rapid bolus infusion of iodinated contrast agent at a rate of ______
3 to 4 mL/sec.
The CTA spiral acquisition:Proper timing of the acquisition with regard to the contrast agent bolus is critical and may be accomplished by:
a. Use of an empiric delay of 15 to 18 seconds.
b. Performing a bolus-timing sequence,
c. Use of automated triggering, or bolus-tracking
software
Performing a bolus-timing sequence
whereby multiple scans through a level of the carotid
arteries are acquired during a test bolus. The
proper delay can be determined by visually identifying
the time at which peak vessel enhancement
occurs.
Use of automated triggering, or bolus-tracking
software
that monitors vessel opacification during
contrast agent administration. The scan automatically
begins once a predetermined HU value
of attenuation within the target vessel(s) is
reached.
The MDCT carotid angiogram:Thin sections are reconstructed with a
minimum 50% overlap to maximize the quality of MPR and 3D images.
The MDCT carotid angiogram: The axial "source" images are reformatted into various
coronal, sagittal and oblique planes
CHEST Technical Considerations
1. MDCT of the chest encompasses a variety of clinical
areas, including:
a. Interstitial lung disease.
b. Evaluation of the mediastinum.
c. Detection and differentiation of pulmonary nodules/
masses.
d. Oncologic staging
e. CT angiography of the major vessels.
f. Cardiac CT.
g. Assessment of the airways.
Protocols for CTA of the neck depend on the technical
capabilities of the CT system employed. Example
technical parameters for a CTA of the neck carotid arteries using a 64-slice system are:
a. Non-contrast helical axial neck images may first
be acquired.
b. Administration of 50 to 75 mL of a non-ionic
contrast agent at 4 mL/sec (12- to 15-second
scan delay).
c. Helical CTA acquisition with 0.625-mm
collimation.
d. 120 kVp/350 mA/0.8 sec.
e.
Speed is one of the key attributes of ______
The acquisition of volumetric data for the entire
lungs within a single breath-hold is now routine.
helical MDCT
Some MDCT systems possess sufficient scanning
speeds to allow for motion-free image acquisition
without the need for suspended respiration by the
patient.
TRUE OR FALSE
TRUE
Reduction of respiratory motion has all but eliminated
the misregistration artifacts historically encountered
during ______. This development has dramatically improved the quality of CT chest imaging.
single-slice CT (SSCT) of the chest
The ability to retrospectively reconstruct thin-section
images is another distinct advantage of ______. Better
visualization and differentiation of small pulmonary
nodules, high-quality MPR and 3D techniques,
and simultaneous high-resolution CT (HRCT) ima
MDCT
Lungs and Mediastinum: The patient is positioned supine with the arms brought ______
above the head to reduce artifact from the shoulder area.
Lungs and Mediastinum: Axial plane helical images are acquired from ______
above the lung apices through at least the costophrenic angles.
Lungs and Mediastinum: Oncologic CT surveys of the chest to evaluate for disease progression should extend through the ______
adrenal glands, which are a common site for metastatic deposit.
Lungs and Mediastinum: Data acquisition is typically performed at the ______
end of a patient's full inspiration
Lungs and Mediastinum: Scanners with detector configurations of 64 rows or more typically acquire CT data through the chest with very narrow detector width, on the order of ______. These data are then reconstructed into thicker sections (3-5 mm) for easy
0.5 to 2 mm
Lungs and Mediastinum: These data are then reconstructed into thicker sections ______ for easy review, with the potential for thin sections to be used in MPR or 3D applications.
3-5 mm
Lungs and Mediastinum:
Settings are 120 kVp with automatically modulated
exposure in the range of ______
range of 40 to 300 mA at rotational
scan times of 0.33 to 1.0 seconds
Lungs and Mediastinum: Low-dose CT of the chest should be considered for all patients when clinically possible, particularly in the pediatric or potentially-pregnant patient. Reduced kVp settings and very low mA down to ______may still produce images of s
1/4 of the routine setting
Lungs and Mediastinum: Pitch varies greatly according to the configuration of the SSCT or MDCT helical system. Overall pitch selection should strike a balance between ______
the requirement for high-quality images and the lowest
patient radiation dose possible.
Lungs and Mediastinum: Pitch must also be
set in accordance with the patient's ability to ______
hold the breath for the length of the scan.
Lungs and Mediastinum: A standard reconstruction algorithm kernel is used for evaluation of the ______
mediastinum and soft tissues.
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COMPLETED AND STOPPED AT CHAPTER 3 Review of Imaging Procedures in Computed Tomography 33