Questions Flashcards
Frequency is defined as:
Number of times particles vibrate each second in the direction of wave propagation
- Inverse of period
- Unit = Hz or 1/sec
Normal range of ultrasound used in imaging
1-30 MHz
1 MHz
= 1 million Hz or 10^6 Hz
As an ultrasound wave travels through the human body, the type of tissue that results in the fastest loss of its strength is?
Lung
Due to numerous air interfaces
A positive Doppler shift indicates that the reflector is moving?
So that the angle between the transmitted beam and the direction of motion is >90 degrees.
If <90 degrees, then direction of motion is away from the beam
What is harmonic imaging?
- Uses ultrasound reflections that have twice the frequency of the transmitted waves.
- Transmitted wave = fundamental ultrasound signal and the return ultrasound = harmonic signal.
- Harmonic generated in the tissue from within the body, beyond the body wall, which leads to a reduction in distortion and scattering
- Harmonic only crosses through body wall once
- Side lobes produced by original fundamental ultrasound do not produce harmonics, so side lobe artifacts and reverberations are less likely with harmonic imaging
- Improves resolution
Laminar flow:
smooth flow where highest velocity is along the central axis of the vessel and gradually decreases toward the walls
When are ascending aorta linear artifacts most likely to occur?
When the ascending aorta diameter exceeds that of the left atrium
Range ambiguity
Occurs when echoes from deep structures created by a first pulse arrive at the transducer after the second pulse has been emitted
Can cause echoes from distant structures to appear closer to the transducer
Resolve by changing depth
A mirror-image artifact in two-dimensional echocardiography develops when:
A structure is located in front of a highly reflective surface, which produces near total reflection of the ultrasound beam.
Ring-down artifact vs Comet Tail
- Ring down caused when a central fluid collection is trapped by a ring of air bubbles
- Region of a bright reflector created, behind which a solid streak or a series of parallel bands radiates away
- Comet tail is due to reverberations off of a bright reflector
Refraction
Results in side-by-side double imaging
Shielding v Shadowing v Ghosting
Shielding: presence of a bright beam of ultrasound artifact that obscures the visualization of tissue beyond this point.
Shadowing: attenuation of ultrasound beyond a bright reflector that obscures the visualization of ultrasound
Ghosting: color Doppler that is distorted beyond anatomic borders because of multiple reflections.
Tricuspid leaflets visualized by plane
4 chamber: Anterior and Septal
RV Inflow-Outflow: Posterior and Septal
LV Volume calculations assume LV is an:
Ellipse
What LV parameter is not affected by preload?
End systolic diameter
A soft first heart sound is caused by:
AV block
With a long PR interval the mitral and tricuspid leaflets float into a semi-closed position because of the long period between atrial contraction and ventricular activation.
The degree to which the mitral valve leaflets are separated when ventricular activation closes the mitral valve is an important determinant of the loudness of the mitral component of the S1.
A loud first heart sound is caused by:
Mitral stenosis
- Leaflets can’t float closer together so they can slam shut
LV calculations yield a smaller LV volume than contrast angio because:
1) LV calculations underestimate the true length of the LV
2) Contrast fills the trabeculations of the LV, yielding a larger volume
Normal longitudinal and radial strain values
Longitudinal (apex to base): 20%
Radial (wall thickening in short axis): 40%
ASE endorsed method for calculating LV EF
modified Simpson’s method (biplane method of disks)
Pulmonary systolic primary variables
S1: Atrial relaxation
S2: LA pressure
C Sept
3 = decreased risk of SAM post MV repair
PISA Area
2 pi r^2
Large Ar wave in pulmonary vein tracing due to:
Mitral stenosis
Obstruction to flow through MV during atrial contraction results in large backward wave
Pericardial Tamponade
- Systolic inversion of RA
- Late diastolic collapse of RV
- RESTRICTIVE mitral pattern
Normal Mitral Flow Variable
E wave: 60
A wave: 60
DT: <100
Hodgkins on TEE appears as:
Anterior mediastinal mass
- Causes decreased LV filling
ASE 16 segment models
Basal Level: 1-6
Midpap: 7-12
Apex: 13-16
Numbers start at anteroseptal in basal and mid pap. Start anterior in apex. Counted counter clockwise
Carpentier Mitral Valve Dysfunction Classification
Type 1: Normal
Type 2: Excessive (a: prolaspse, b: flail)
Type 3: Restrictive
Persistent left SVC associated with:
Coronary sinus ASD
Focal depth of ultrasound
= Diameter^2/ (4 x wavelength)
A more shallow focal depth will produce a wide beam in the far field
Beam diameter at focal point in an unfocused beam:
= 1/2 diameter of the transducer
Most common congenital heart defect observed in adult patients?
Bicuspid AV
ASDs and associated findings
Ostium Secundum: MR and MV prolapse
Ostium Primum: MR and MV cleft
Coronary Sinus ASD: Persistent left SVC
Sinus Venosus ASD: Anomalous pulmonary vein drainage
Dextroversion
Situs Inversus
Dextrocardia
Dextroversion: rightward shift in the cardiac apex without mirror image inversion
Situs Inversus: right to left reversal of thoracic and abdominal viscera
Dextrocardia: mirror image inversion of the heart to the right
Sensitivity in detecting dissection of the aorta
CT > TEE = MRI > Aortography
Aortic dissection True v False Lumen
TL:
round
expands in systole
laminar flow
FL:
typically larger
smoke
Restrictive Mitral filling pattern
- Cardiac tamponade
- Constrictive pericarditis
MR Values
EROA
Mild: 0.4
RF%
Mild: 50%
VC
Mild: 0.7
TR Values
VC
Severe: >0.7
TRarea/RAarea
Mild: 16-30%
Mod: 30-60%
Severe: >60%
Unit Conversion
1 second = 1,000,000 musec
1 second = 1,000 msec
1 meter = 100 cm
1 meter = 1,000 mm
Propagation Velocity
= stiffness/density
Propagation velocity will increase with stiffness of item. However, if given a list, in general more dense items have a higher propagation velocity since they also have much higher stiffness (which outweighs the increase in density)
Pulmonic Valve Leaflets
Right, Left, Anterior
Third Order Chordae
Attach to ventricular wall (not papillary muscle) and attach to base of posterior leaflet only
Which view of mitral valve passes through the highest or most basal portion of the mitral annulus?
Midesophageal long-axis
- Also good to assess leaflet prolapse
Pulse Repetition period vs PRF
PRP
- Inverse of pulse repetition frequency
- Time from start of one pulse to start of next
PRP = 13 x depth
PRF
- number of pulses that occur in one second
PRF = 77,000/depth
Pressure, intensity, amplitude and power equations
Pressure: dB = 20 log (P2/P1)
Intensity: dB = 10 log (I2/I1)
Amplitude: dB = 20 log (A2/A1)
Power: dB = 10 log (P2/P1)
Attenuation coefficient = 1/2 frequency
Total attenuation = AC x depth
20MHz probe with amplitude 1mm, what is amplitude at 8cm depth?
AC = 20/2 = 10
Total Attenuation = 8x10 = -80
* negative because lost amplitude
dB = 20 log (A2/A1) = -80 log (A2/A1) = -4 A2 = A1 x 10^-4 if Amplitude initial (A1) = 1, then A2 = 1 x 10^-4
Angle of refraction
Refraction REQUIRES:
1) Oblique angle of incidence
2) Difference in velocity of sound in medium
Snells Law:
(Sin angle transmission)/(Single angle incidence) = V2/V1
If velocity of first medium greater than second medium, then the angle of refraction will be less than angle of incidence
If velocity of first medium lower than second medium, then angle of refraction will be greater than angle of incidence
Order of vessels on aorta
Celiac
SMA
Renal arteries
IMA
Myocardial Performance Index
(IVRT+IVCT)/Ejection Time
Deceleration Time
Normal aging: DT increases with impaired relax
Pseudonormal: DT will decrease as E wave rises and reverts back to normal
Restrictive: DT increases further as E becomes tall and sharp
DT normal = 150-220
LV Wall Tension
LV Wall Stress
Tension = Pressure x Radius
Stress = Tension/ (2xThickness)
= (Pressure x Radius) / (2 x Thickness)
Fractional Shortening
= (LVEDd-LVESd)/LVEDd
Mitral Flow Changes with Acute Heart Rejection
RESTRICTIVE PICTURE
- Decreased IVRT
- Increased E wave velocity
- Shortened E wave DT
- Decreased E wave PHT
- Decreased tissue doppler
RV Pressure v Volume Overload and Septum
RV Pressure Overload:
- Paradoxical septal motion during systole (septum flattens)
RV Volume Overload
- Paradoxical septal motion during late diastole (period of highest RV volume)
Constrictive Pericarditis
- Normal systolic function
- Restrictive mitral inflow profile
- Normal LV wall thickness
- Normal LV diameter
- DILATED left atrium due to chronic pressure overload
Chiari network association
- PFO
- Interatrial septal aneurism
Nyquist Limit
Maximal DOPPLER SHIFT that can be measured and determines max velocity that can be measured
IT IS NOT the max velocity that can be measured
NL = 1/2 PRF
Stunned v Hibernating Myocardium
Stunned: Newly reperfused myocardium that has impaired wall motiion that reverses following resolution of reperfusion injury
Hibernating: viable mycardium that appears dysfunctional and has little reserve (improves with low dose dobutamine but deteriorates with high dose dobutamine)
Myocardial Contrast Echo
- Injection of contrast into aorta root and watching perfusion of myocardium
Can distinguish:
- Acutely ischemic myocardium (RWMA with no perfusion) from stunned myocardium (RWMA with perfusion)
Myocardial PET imaging
- The gold standard for determining myocardial viability
- NH3 = marker of perfusion
18F-fluorodeoxyglucose = marker of metabolism
Normal: Normal perfusion and metabolism
Scar: Decreased perfusion and metabolism
Hibernating: Decreased perfusion, normal metabolism
LVH, values
Normal: 0.6 - 1.1 cm
Mild: 1.2 - 1.4 cm
Moderate: 1.2 - 2 cm
Severe: >2 cm
Restrictive Cardiomyopathy
- Thick RV and LV walls
- Normal EF
- Dilated IVC
Chronic HTN
- Concentric LVH
- AV sclerosis
- MV annular calcification
- Aortic root dilation
- LA enlargement
- Impaired relaxation
What type of transducer can create multiple focal zones per scan line?
Phased array transducers
- Will increase lateral resolution
Which valve is least likely to be effected by endocarditis?
Pulmonic Valve
Complications of Mitral Repair
- LV rupture (most common, but rare)
- Circumflex damage
- Left or Non-coronary AV cusp damage
- SAM of the Anterior mitral leaflet
- Conduction delay
What method of determining MS valve area is not affected by AI or MR?
PISA
Continuity equation for use in MS will be affected by MR or AI since there is are then different volumes of flow through MV and AV and continuity equation is assuming identical flow through both of these valves
What methods of determining AS are not affected by decreased EF or MR?
Continuity Equation
- compares LVOT and AV stroke volumes which would remain the same in decreased EF or with MR
AND
VTI lvot / VTI av
- Should be similar so = 1
Mild AS: >0.5
Mod AS: 0.25-0.5
Severe AS: 0.25
As AS worsens, VTI of AV grows, but VTI of LVOT remains the same
TAPSE, values
Normal: 20-25
Decreased RV function <16
AI Slope
Moderate AI: 200-300cm/sec
Severe: >300
Maximum spatial peak temporal average intensity for ultrasound beams
100 mW/cm^2
Calculating axial resolution from frequency
If frequency of probe 5MHz and pulse contains two cycles, then
axial res = 1/2 x SPL
SPL = (cycles)x(1540m/s)/(frequency)
= 1/2 x (2 x 1540)/5x10^6 cycles/s
Endocardial Wall Thickening, Grading
Normal: >30%
Mild HK: 10-30%
Severe: <10%
Q factor
Describes quality of ultrasound
= Resonant Frequency/Bandwidth
Which scallop of mitral valve is most likely to develop myxomatous degeneration, annular dilation and regurgitation?
P2
TR Jet/RA area
Trace: 60%
Half layer thickness
Thickness of tissue required to reduce intensity by half
What are piezoelectric crystal made of?
Lead zirconate
Axial resolute and SPL
Axial resolution = 1/2 x SPL
Resonant frequency of crystal, equations
Frequency = Velocity/Thickness
Velocity = Stiffness/Density
Cos 60
0.5
Bandwidth
Shorter pulse = wider bandwidth
Imaging transducers have wider bandwidth than therapeutics
Q factor (quality)
Q = Resonant freq/Bandwidth
AVA by Aortic valve side
AVA = (aortic valve side ^2) x 0.433
Pericardial Effusion
Mild 2cm
If ultrasound probe interrogates vessel at a 60 degree angle,
freq emitted = 10MHz
Returning freq = 10.5MHz
What is velocity of flow?
Velocity = (Change in freq/Cos Angle) x (1540/(2xFreq transmitted))
Thebesian Valve
Fibrous band at the opening of the coronary sinus
- Can make coronary sinus catheter placement difficult
Basal posterior wall
Region 4
- NEVER hypertrophied in cardiomyopathy
Dobutamine stress, sens and spec?
Sens: 85%
Spec: 88%
Most load INDEPENDENT measure of systolic function?
Dp/Dt
Velocity of circumferential shortening
= (LVEDd-LVESd)/(LVEDdxET)
ET = ejection time
** Corrects for HR, so it is a HR INDEPENDENT measure
Epiarotic scan
Aorta most closely located to probe
Azygous vein seen below aorta (triangular in shape)
Intensity reflection coefficient
= reflected intensity/incident intensity x 100%
= (incident-transmitted)/incident intens x 100%
Dampening material (aka backing)
- Decreases the transducer sensitivity to reflected echo
- Decreases SPL and improves axial resolution
- Lowers Q factor (better image) by decreasing resonant frequency and increasing bandwidth
Determining factors for: Wavelength Frequency CW Frequency PW Resonant frequency
Wavelength: thickness of piezoelectric crystal
Frequency CW: electrical frequency of the excitation voltage applied to crystal
Frequency PW: thickness of crystal and propagation speed of sound through crystal
Resonant frequency: Velocity/Thickness
Focal length
= near field length
= (radius transducer^2)/wavelength
Refraction artifact v Mirror image
Refraction: artifact to the side and slightly lower than original
Mirror Image: artifact below and slightly to side of original
Remnant of sinus venosus
Chiari network
- Assoc with aneurismal septum and PFO
E-point Septal Separation (EPSS)
- Mmode through septum and anterior mitral leaflet to measure maximal distance between two in end diastole
- Decreased EPSS correlates with decreased EF
Rayleigh Scattering
- Scattering that occurs when the wavelength is much larger than the reflector it strikes
- Responsible for Doppler determination of blood flow velocities
Subarterial VSD synonyms
= supracristal = conal
Blalock-Taussig Shunt
Glenn Shunt
B-T Shunt: Right subclavian to PA
Glen: SVC to PA
ABSOLUTE TEE Contraindications
- Pt refusal
- Esophageal perforation
- Esophageal web, rings, strictures
- Cervical instability
- Obstructing esophageal neoplasm
Wall Tension
Wall Stress
WT = radius x pressure
WS = WT/Wall thicknessx2
MVA and PHT, imperfections
Decrease PHT and Overestimate MVA
- Impaired LV compliance
- Severe AI
- Severe MR
Increase PHT and Underestimate MVA
- Impaired relaxation
Mitral Valve Dilation
End systole anterior posterior mid esophageal long axis measurement greater than 3.6cm
Intensity and power
= amplitude squared
Intensity= watts/cm^2
Spatial peak temporal average intensity
- correlates with the heating of tissues
- same as spatial peak temporal peak when using CW ultrasound
Crystal focal length
Length = (radius^2)/wavelength
Radius= radius of crystal
Hypereosinophilic Syndrome
- Systemic disease affecting brain, heart, bone, lungs
- restrictive dysfunction with normal systolic function AND LV thrombus (normally in apex, but occasionally under posterior mitral leaflet causing MR)
Percent of patients who develop SAM after mitral repair?
2-16%
AI grading, Jet/LVOT diameter
65% - severe
