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Spectral Signature
Spectral Signature
Doppler Spectrum Arterial
Doppler Spectrum Arterial
Types of Flow Arterial
Types of Flow Arterial
Flow Patterns Arterial
Flow Patterns Arterial
Venous Spectrum Cardiac Phasicity
Venous Spectrum Cardiac Phasicity
Venous Specturm Respiratory Phasicity
Venous Specturm Respiratory Phasicity
Head and Neck Vessels
Head and Neck Vessels
Intracranial Vessels and Veins
Intracranial Vessels and Veins
Upper and Lower Limb and Chest Arteries
Upper and Lower Limb and Chest Arteries
Abdominal Aorta and Iliac Arteries Celiac Trunk and SMA
Abdominal Aorta and Iliac Arteries Celiac Trunk and SMA
IVC Iliac and Hepatic Veins
IVC Iliac and Hepatic Veins
Hepatic and Renal Vessels
Hepatic and Renal Vessels
Ovarian Testicular and Bowel Vascularity
Ovarian Testicular and Bowel Vascularity
Adult vs Pediatric and Abnormal Waveforms
Adult vs Pediatric and Abnormal Waveforms

Hi. My name is Govind Chavhan, and I'm going to talk on Doppler spectral waveforms, what is normal. In this talk, I will discuss the spectral waveform formation, its parameters, and the information it provides to us. This will be followed by region wise discussion on normal waveforms in all major arteries and veins in the body, with hemodynamics behind it. And in the end, I will discuss differences between adult and pediatric waveforms.

[BLANK_AUDIO] Blood flow in any vessel is determined by pressure differentials between ends of the vessels and resistance offered by the vessel. Ratio differential is in turn determined by cardiac function and the relative position of the vessel from the heart, while the resistance which is offered by the arteriolar bed is determined by the physiologic

need of the organ. Counseling the cardiac practice team for all the vessels in the body. Each vessel has a characteristic flow pattern, as seen on the Doppler waveform, that reflects its relative position and physiologic need of the organ it supplies. So to say, to a certain extent Doppler waveform reflects a spectral signature of that vessel. Doppler spectrum is nothing but a

time velocity waveform that represents variation in the velocity during

the cardiac cycle. The velocity is plotted along the y axis, while the time is plotted along the x axis. The line which changes with the velocity is called as a spectral line. The spectral line has certain intensity and width. So the spectral intensity is determined by number of red blood cells reflecting the ultrasound waves.

So for this point and this particular brightness, if I have 100 red blood cells reflecting the ultrasound waves, if I increase that number to 1000 then the brightness of this point will increase. The spectral width is determined by range of velocities. So for this particular width of the spectral line, if I have velocities

ranging from 40 to 60 centimeters per second, if I increase that range to 10 to 100 centimeters per second, then the width of this line will increase. The clear black space between the spectral line and the base line is called as a spectral window. So whenever there is increase in the range of velocities, there is spectral widening and filling of this window which is called as a spectral broadening.

From the spectral waveforms we also can get the velocities. The highest velocity in the cardiac cycle is called as a fixed systolic velocity. We just add the peak of this systolic peak, and we also get an end diastolic velocity which is at the end of the diastole. The end diastolic velocity may not necessarily be a lowest velocity in the cardiac cycle. Apart from these velocities, we also get the

indices which are called resistive indices and pulsatility indices. So the resistive index is derived as PSV minus EDV divided by PSV, while the pulsatility index is derived as PSV minus EDV divided

by mean velocity over a cardiac cycle. These indices help to compare the vessels because they null the effect of angle of insonation. [BLANK_AUDIO] Any tube guiding the fluid can show three types of flow, which include

plug flow, laminar flow and turbulent flow. This is to a large extent true for the human musculature. The first type of flow seen is a plug flow. So for Doppler purposes, the blood flow is nothing

but movement of the red blood cells because most of the ultrasound waves are reflected back by the red blood cells. So what we're tracking by Doppler is the movement of red blood cells. So in a plug flow all the red blood cells are moving at the same rate, so that if you join the all front red blood cells, there'll be a flat line. So that [UNKNOWN] will be a flat, and this is

called as a plug flow. The plug flow is seen as sharp spectral line and clear black window on the spectral waveforms. And the plug flow is typically seen in larger arteries like aorta. The second type of flow is laminar flow. So in laminar flow the red blood cells which are close to the vessel wall are moving at a slower speed, and that is because the friction offered/g by the vessel wall,

while the RBCs in the center are moving at a faster rate. So if you join a wave front it will be a parabolic curve. And this is nicely seen on these colored images where you can see the red and yellow colors in the center, which represent higher velocities, while in the periphery of the

vessel you have the blue color which represents the lower velocities. Now laminar flow is seen as spectral broadening on spectral waveform because there are a wide range of velocities. The third type of flow is turbulent flow, which is not only there are large range of velocities, but there is also disorganized flow with some components in the reverse direction. So on spectral waveform it is seen

as spectral broadening, as well as there'll be some component below the baseline because of the reversal of the flow. The turbulent flow can be seen on color images as aliasing. So aliasing means multiple color in that region that represent the turbulent flow. So this is a case of liver transplant with hepatic vein joining the IVC, and at the anastomosis you have multiple colors suggesting aliasing and

turbulence. And that indirectly indicates that there is some degree of narrowing at the anastomosis. Coming to the flow patterns, arteries in the body will show these two type of flow pattern. The first one

is a low resistance. So organs like brain and kidney will have low resistance in their vascular bed, so they allow more blood flow to come. And in this type of flow the spectral waveform is typically

a sharp systolic peak, followed by thorough/g diastolic flow throughout the cardiac cycle. And this is also called as a monophasic flow. This is as against the high resistance flow, which is typically seen in the extremities where the arterial bed of the muscle offers a lot of resistance to the blood flow. And because of that resistance, after the systolic peak

there is a early diastolic reversal and then there is a forward diastolic flow for a variable length. So the high resistance flow is also called as a triphasic flow because there are three phases in this spectrum. Coming to the venous spectrum. So this is a venous spectrum which is acquired with

free breathing.

And you can see that there are variations in the amplitude of the spectrum. This variation in the velocity is caused by two factors, one is the cardiac phasicity, another is the

respiratory phasicity. If you acquire the same venous spectrum with breath hold, then you see clear waveforms which are representative of pressure changes in the right atrium, that are reflected back in the major veins of the body. So typically in a venous spectrum

which is acquired with the free breathing, we see four types of waveforms. First is a, followed by S, then v and D. So the a-wave is caused by atrial systole which causes positive pressure in the right atrium. This is followed by the S-wave. Now this S is for the systole, but the systole is of the right ventricle rather than right atrium. So during the right ventricular systole the a

v group moves towards the cardiac apex/g creating sort of a negative pressure in the right atrium, causing this S-wave. With the mitral valve still closed, there is build-up of the blood in the right atrium, which causes slight positive pressure in the right atrium, causing the v-wave. And after the systole, there is opening of the mitral

valve which pours the blood into the right ventricle, and there is negative pressure in the right atrium causing the D-wave. Now with the mitral valve still open, there is gradual build-up of the blood because venous [UNKNOWN] Is continuously coming to the right atrium. And there is rise in the pressure in

the right atrium that ends in the atrial systole causing the a-wave. So this a, S, v and D wave should be clearly seen in all the major veins of the body, especially close to the heart, when you acquire the spectrum with the breath hold. Now coming to the respiratory phasicity, so veins in the neck and upper extremity,

they will have increased velocities during the inspiration. That

is because during the inspiration there is negative intrathoracic pressure which allows more venous return to come inside the chest. And opposite happens during the expiration, because expiration has a positive intrathoracic pressure that raises the venous return, and there'll be low amplitude or low velocities in the venous waveform. Now

if you move to the diaphragm, there are three openings in the diaphragm. The first one is at T12 level which allows aorta to enter into the abdomen. This opening remains unaffected during the diaphragmatic contraction during inspiration because it is behind the crura. The second opening is at T10 level which allows esophagus to go into the

abdomen. This opening gets narrow during the inspiration because of the diaphragmatic contraction, and it also pinches the gastroesophageal junction preventing the gastroesophageal reflux. The third opening is at T8 level which allows the IVC to enter into the right atrium. So this opening is in the fibrous tendon/g part of the diaphragm, so it remains widely open during the diaphragmatic contraction.

And because there is increased intra-abdominal pressure during the inspiration, there is increased venous return to the IVC during the inspiration. So in the IVC and hepatic vein there is increased amplitude or increased velocities during the inspiration, which is similar to the upper extremity and neck veins, and there is reduction in the velocity during expiration, which is again similar to the

upper extremity and neck veins. Now if you go down to the legs the story is slightly different because there is increased intra-abdominal pressure which raises the venous [INAUDIBLE] From the legs. So during inspiration in the leg veins there is actually reduction in the velocities, and there is increased velocities during

the expiration. So to say, the effect of respiration on the venous velocities is exactly opposite in upper and lower limbs. Now we'll go region wise in all the organs and see what are the normal

spectral waveforms in major arteries and veins, and we'll start with the external carotid artery. So external carotid artery supplies the high resistance vascular vein of the facial muscle. So as expected

it shows a triphasic waveform with early diastolic reversal, as against the internal carotid artery which supplies the low resistance waveform of the cerebrum. So there is continuous forward/g flow with the monophasic waveform, and there is no diastolic reversal. Also note that the flow is quite higher above the baseline compared to the external

carotid artery. The common carotid artery as expected will resemble the combination of ICA and ECA, but it resembles more to the ICA because 80% of the blood goes to the ICA, and external carotid artery receives only 20%. Vertebral artery also supplies the low resistance vascular bed of the brain, so it will show a monophasic low resistance waveform, but these vessels are usually smaller in

diameter, and any vessel less than five millimeter normally shows a laminar flow. So there is a spectral broadening in the vertebral artery spectrum. This is a normal waveform in the internal jugular vein,

which shows a, S, v and D waves. Intracranially all the vessels are supplying a low resistance vascular bed, so the waveform will be monophasic

low resistance, but there are differences depending on the age of the patient. So typically in neonates and premature

baby, there is less diastolic flow with a high resistance. So in a premature baby, resistive index up to 1 is considered normal, in the term baby the upper limit of resistivity index is 0.8. [BLANK_AUDIO] Intracranial veins, the most commonly sample intracranial vein is

superior sagittal sinus, which may show this flat waveform or it may show a wavy waveform which is result of the synchronous arterial/g position. The waveforms in the superior sagittal sinus varies a lot. It may change with the change in the head position, probe

pressure or even baby crying. The other way in which it's commonly sampled in children is transverse sinus, which also shows a wavy spectral waveform. Coming to the upper limb arteries. So upper limb arteries supply

high resistance vascular bed of the musculature. So it will show a typical triphasic pattern which consists of sharp systolic peak

followed by early diastolic reversal and then forward diastolic flow. There are also changes in the waveform in the extremity arteries with age. In a smaller child there is less diastolic flow as compared to the older child and adult, and in premature baby there may be complete reversal of the diastolic flow and that may be related to the patent ductus arteriosus. Upper limb veins will show changes

with the cardiac phasicity and respiratory phasicity, so there is increase in the velocity during the inspiration and reduction in the velocity during the expiration. [BLANK_AUDIO] Lower limb arteries will show similar waveform to the upper limb arteries, and as you go down from proximal to distal, the forward diastolic flow amount gradually reduces, and at the level of the ankle or wrist, you may

not see any forward diastolic flow above the baseline. And this is still normal. As long as we have a nice systolic peak it is still considered a normal waveform. The lower limb veins will show exactly opposite changes related to the respiration as compared to the upper limb veins. So there'll be reduction in the velocity during the inspiration and increase in the velocity during the expiration.

[BLANK_AUDIO] Coming to the chest, ascending aorta is a large vessel, and as we saw it shows a plug flow, so the spectral waveform will be a sharp spectral line with clear black window. The brachiocephalic artery is similar to the common carotid artery, and may or may not show diastolic reversal, or a triphasic pattern. The superior vena

cava and the brachiocephalic veins are very close to the right atrium, so even without breath hold they will show the a, S, v and D waves. The amplitude of these waves will change with the respiration but they're are very clearly seen because they are closest to the heart. Moving to the abdomen. So abdominal

aorta shows plug flow, as we noted earlier, with a clear spectral

window. As we move down from proximal to the aortic bifurcation, there are changes in the waveform. So the upper part of the aorta before the renal origin will typically show a low resistance waveform with increased diastolic forward flow. And below the renal artery origin there'll be less forward diastolic flow and increased resistance, and that

reflects the supply of the organs. So above renal arteries it supplies liver, spleen and kidneys, so it'll have a low resistance waveforms. While below the renal origin it supplies the extremities, so you'll have the high resistance waveform. Ciliac trunk at the origin may show a triphasic high resistance waveform, but it immediately branches into the splenic and hepatic arteries. So these arteries will

show a typical low resistance monophasic waveform. The superior mesenteric artery in a fasting state, typically shows a triphasic, high resistance waveform, but after the food when the digestion starts, it turns into the low resistance monophasic waveform. So IVC and iliac veins show increased velocity during the inspiration and reduction in the velocities during

the expiration. And this range should show a, S, v and D waves when they are patent. There may be change in the amplitude with the phase of the respiration. This is a waveform which is obtained with free breathing in the IVC. It shows a reflection in the amplitude, which is combination of respiratory as well as cardiac phasicity. But when you acquire with the free breathing, there are clearly a, S, v

and D waves seen in these major veins. Hepatic veins are probably the best to see these a, S, v and D waves because they are closest to the heart, but the exception is in neonatal hepatic veins. In the neonates you my not see this reflection because of the different

compliance of the [UNKNOWN] Parenchyma, and they may be a monophasic wave in the hepatic veins of the neonate, and it still concern normal. Hepatic artery shows a typical monophasic low resistance waveform. The resistive index in the hepatic artery increases with age and

after meal. The RI is less in the parenchyma as compared to the portal/g. There's normally a smooth or slight variation in the amplitude

of the portal vein, which the cause is precisely not known but it may be related to the cardiac changes or the respiratory phasicity. Kidneys are one of the organs which draw a large proportion of cardiac output. They typically show a low resistance monophasic waveform, and there are changes in the amount of diastolic flow with the age. In smaller children, especially the neonates and premature

baby, the amount of diastolic flow is quite less, resulting into increased resistive index. So for a preterm baby the resistive index upper limit is up to 0.9, for the infants it is 0.6 to 0.8, and for the older kids and adults the normal range is 0.5 to 0.7. When you sample the resistive index in the kidneys, you should sample either arcuate arteries

or interlobar arteries, then it truly represents the true parenchymal perfusion rather than the central vessels. Coming to the ovary and testicular vascularity. So ovary typically has dual blood supply. The major artery comes from the aorta as the ovarian artery, and ovary

also get some smaller branches from the uterine artery. You normally don't see the single ovarian artery, so what we sample is small

vessels in the parenchyma of the ovary. So the waveforms in the ovary change with the age. In a pre-pubertal girl, the waveform is typically high resistance with less diastolic flow that changes to the monophasic low resistance waveform up to the puberty, because ovaries become physiologically active. The same is true about the testes. So in a pre-pubertal boy, the testes will show high resistance

flow pattern with less diastolic flow. But after puberty that changes to the monophasic low resistance waveform. In a small child like neonate with a small testicular volume of less four to five CCs, you may not normally detect any flow and it's still considered normal. You should go with the [UNKNOWN] Scale findings for any abnormalities. [BLANK_AUDIO] Bowel vascularity also can be sampled with a Doppler. So this is

typically sample in neonates with necrotizing enterocolitis. Unless the bowel wall is thickened, you may not see the actual vessel in the bowel wall. What you sample is the vessels in between the bowel loops in the mesentery when the bowel loops are collapsed. So what are differences between adult and pediatric waveforms? The velocities

in general are higher in children as compared to the adults, and the resistive indices

are higher in children especially in neonates, in brain and kidneys, the resistive index is higher than the adult. So after looking at normal waveforms all over the body, just one slide on typical abnormal waveforms. So this a normal waveform. Triphasic high resistance

waveform in the extremities. This is a biphasic with absent diastolic flow waveform. The difference between this and the upper waveform is that there is significant reduction in the height of the systolic peak. So this waveform with reduction in the systolic peak and absent for our diastolic

flow is typically seen in the distal obstruction. This is a classic parvus tardus waveform which is slow to rise and less to rise. So these waveforms are typically seen in the proximal vessel obstruction. This is a monophasic, high velocity, turbulent, continuous flow. There are high velocities,

and there is a turbulent flow because the spectral window is filled. So this flow is seen when there is no resistance offered distally, and this is the typical waveform of the arteriovenous fistula. The last waveform is called as a forward systolic and reversed diastolic, or to-and-fro flow sample in the pseudoaneurysm. So there is equal amount of blood going into the pseudoaneurysm and same amount is

coming back. This is as against this waveform which looks similar to this one, but the amount below the baseline is quite less. So this is a diastolic reversal which is typically seen in patent ductus arteriosus. So to summarize, each vessel has a characteristic flow pattern seen on Doppler waveforms that reflects its relative position

and physiologic need of the organ. The venous waveform show changes

with the cardiac and respiratory phasicity. And in general, lower velocities and higher resistive indices are seen in children as compared to the adults. Thank you very much.

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