Unit 1 - Injection Techniques Flashcards
What is the need for contrast?
- to differentiate adjacent structures
- improves observation
What are the other name/s of Contrast studies?
- ## Enhanced studies
Nonionic, Dimer, watersoluble
The most expensive BUT least harmful
Routes of Contrast: for the gastrointestinal tract enhancement
Orally
Routes of Contrast: for vascular and systemic enhancement
Intravenously (IV)
Routes of Contrast: for the LOWER gastrointestinal tract enhancement
Rectally
Routes of Contrast: for the spinal cord enhancement
Intrathecally
Routes of Contrast: for the joints enhancement
Intra-articularly
Routes of Contrast: for the bladder enhancement
Intravesical
Types of Oral contrast
- Positive
- Neutral
- Negative
Examples of Positive Types of Oral Contrast
- Barium Sulfate (BaSO4)
- Iodine Based:
- Omnipaque
- Gastrografin
Examples of Neutral Types of Oral Contrast
Water (H2O)
Examples of Negative Types of Oral Contrast
- Carbondioxide (CO2)
- Air
Opacification of vasculature and distributes to the extravascular space/parenchyma
Intravenous
Cons of Contrast
- High attenuation of IV contrast = increased beam attenuation (Streaky Image)
Other names of unenhanced Image
- Pre-contrast image
- non-contrast image
- non-enhanced image
- baseline image
Properties of IV Contrast
- Osmolality
- Viscosity
- Ionicity
Characteristics of a stable IV access site
- Well located
- Recently established
- No medication running
- No signs of complications
How to test IV site?
Inject saline prior, 2-5 ml PREFERABLY 10 ml
Alternate vascular access options
- Central Venous Access Device
- Peripherally Inserted Central Catheter
Methods of Contrast Media Injection
- Drip infusion
- Bolus Techniques:
- Hand injection
- Mechanical Injection System
Fluid sent directly into SVC, IVC or Right Atrium
Central Venous Access Device (CVAD)
Its tip is located in the lower third of SVC and usually uses hand bolus method of injection.
Peripherally Inserted Central Catheter (PICC)
Specially designed PICC - can be uses for injections with rates of 5 ml/s has a different colored lines to be distinguished from the normal PICC Line
Power PICC
The two types of CVADs
Longer term solutions for IV therapy
1. Tunneled - under the skin
2. Non-tunneled
The same CVAD intended for dialysis should or should not be used for CM administration?
should NOT
Documentation of CM Administration
- Name of CM
- Dose (Volume and concentration)
- Flow rate/s
- Injection site
- any adverse events and associated interventions
Planning of contrast exam are based on what factors?
- Pharmacokinetic
- Patient (Anatomy and pathology of interest)
- Equipment-related factors
Phases of Tissue Enhancement
- Arterial Phase (Bolus)
- Venous Phase (Non-equilibrium)
- Equilibrium Phase (Delayed)
Characteristics of General Phases/ determined by these factors:
- rate of the contrast material
- time elapsed from the start of injection to scan (scan delay time)
What is AVID?
Arteriovenous Iodine Difference (AVID) is used to compare and differentiate the three phases in CT images.
Compares Abdominal artery to IVC
AVID: 30 or more HU
Arterial Phase (Bolus)
Scan delay time: first minute/60 secs. SDT < 60
Arterial Phase (Bolus)
Contrast in the arterial structures.
Arterial Phase (Bolus)
Scan delay time: after the first minute. 60 < SDT
Venous Phase (Non-equilibrium)
AVID: 10 to 30 HU
Venous Phase (Non-equilibrium)
Contrast in the parenchyma.
Venous Phase (Non-equilibrium)
AVID: less than 10 HU.
Equilibrium Phase (Delayed)
Contrast in everywhere, diluted in the veins and soaked the organ parenchyma.
Equilibrium Phase (Delayed)
Scan delay time: After 2 minutes. 120 < SDT
Equilibrium Phase (Delayed)
CM drips during a period of several minutes, and the patient is scanned after most/all of the CM is administered.
Drip infusion
Method that uses gravity, the flow rate is a variable and could be affecter by many factors: bottle height, CM volume and viscosity, IV catheter length and size.
Taken images usually in the equilibrium phase
Drip infusion
It is not advised to use this method for the neck, chest, abdomen or pelvis
Drip infusion
It could be used in the brain, because its extended period of time can cross the Blood Brain Barrier.
Drip infusion
Rapid injection of contrast followed by image acquisition.
Volume: 50 - 200 ml
Rate: 1-6 mL/s
Bolus technique
Characteristics of hand injection
- Variable flow rate
- inconsistent images thus less reproducibility.
- requires two operators
+ INEXPENSIVE and extravasation events are rare
Most common method for CM delivery
Mechanical injection
Characteristics of Mechanical
+ consistent reproduceable
+ Accurate flow rates and volumes
- More chances of extravasation and air embolism
- expensive
More chances for extravasation and air embolism to occur
Mechanical Injection
Maximum pressure value in the mechanical injector
300 psi
Flow rates: Slow
1 - 2 mL/s
- used for suboptimal IV Access
- for routine contrast-enhanced brain study
Flow rates: Standard
3 mL/s
- for MOST contrast-enhanced studies
Flow rates: Fast
4 - 5 mL/s
- for angiographic studies
Determines the amount of contrast enhancement in a patient’s vessels and tissues.
Factors affecting contrast enhancement
Demonstrates the effect of any of the factors on the enhancement peak (Amplitude, width, and shape)
Time-density curves
Pharmacokinetics Factors include:
- concentration, osmolality, and viscosity
- volume, flow rate, and injection duration
- Scan delay time
- total scan time
A fast injection with low concentration of CM will produce the same concentration with
slow injection with high concentration
High flowrate = time to peak enhancement?
Decreases - reduces the scan delay time
High flowrate = injection duration?
Decreases
High flowrate = peak height?
High and narrow
To capture the same level of contrast enhancement of slow scanners, faster scanners require less volumes but must be given a longer scan delay.
True or False?
True
Automated Injection triggering methods
- Test Bolus
- Bolus triggering/tracking
Administer a small initial amount of contrast (10-20 mL)
Test bolus
8 to 15 seconds after injection a number of low-dose serial scans are performed every 2 seconds at a specific anatomical level (Aortic arch, pulmonary trunk)
Test bolus and Bolus triggering/tracking
how to decide at what time to scan the patient with the method of test bolus
The image with the max enhancement is selected, its used to determine the time to peak enhancement and its scan delay for the actual diagnostic scan
What is the formula for test bolus?
Trial scan delay + (2 x img #) + 3 seconds
Alternate method to determine the scan delay for each pt
Bolus triggering/tracking
Administering the full contrast dose, once near peak enhancement of the target structure is reached the table moves back to the starting position and actual diagnostic scan begins.
Bolus triggering/tracking
