1. Spectral Doppler ultrasound parameters like wall filters, inversion, angle correction, spectral gain, gate size, and gate position must be optimized to accurately depict blood flow velocity and direction.
2. Wall filters eliminate low frequency noise but can obscure slow flow if set too high. Inversion can falsely suggest reversed flow if not adjusted properly.
3. Angle correction calibrates the velocity scale based on the angle between the ultrasound beam and flow, and inaccurate correction will underestimate or overestimate true velocity.
4. Spectral gain, gate size, and position must be set to clearly outline flow without including erroneous signals.
Electromagnetic Flow meters
Blood flow helps to understand basic physiological processes and e.g. the dissolution of a medicine into the body.
Blood flow and changes in blood volume, are usually correlated with concentration of nutrients and other substance in the blood.
Also, Blood Flow measurement reflects the concentration of O2.
IT CONTAINs all the subtopics related to it. it has BloAck diagram, internal working and much more.
Subject; Measurement & Instrumentation
Teacher; ma'am Falak Naz Pathan
MEHRAN UET SZAB CAMPUS KHAIRPUR MIR'S
This presentation is focused on basic understanding of video signal generation and its electronic interpretation. Contents are taken from bible of television!
This presentation is dedicated to R R Gulati.
Singular value decomposition filtering in high-frame-rate cardiac vector flow...journalBEEI
Dysfunction of the left ventricle (LV) weakens the cardiac function and affects the physical activity. Echocardiagraphy has been used to visualize the blood flow dynamics and to evaluate the cardiac function. However, the signal processing to suppress the clutter signals should be employed. In this study, we employed the singular value decomposition (SVD) clutter filtering to obtain the cardiac blood speckle images. We also employed the adaptive thresholding metric to determine the proper cutoff values at each phase during the cardiac cycle. Moreover, we employed a depth-dependent SVD clutter filter for more accurate estimation of the cardiac blood echo signals. The 2D blood flow velocity vectors were estimated by applying the block matching method to obtained blood speckle images. The obtained results show that the proposed filter suppressed the clutter signals from left ventricular wall significantly, and the contrast-to-noise ratio (CNR) was improved from -0.5 dB to 13.8 dB by the proposed SVD clutter filtering.
5. An analog filer has system fnction Ha(s)--a (a) (10 pts,) Comvert .pdfinfo324235
5. An analog filer has system fnction Ha(s)--a (a) (10 pts,) Comvert this analog filter into a
digital iker by means of the bilineasr filter by means of the bilinear trasformation method with T,
= 0.1. (b) (5 pts.) Is this filter FIR or IIR? (c) (5 pts.) Find the poles of this digital filher
Solution
Hundreds if not thousands of different kinds of filters have been developed to meet the needs of
various applications. Despite this variety, many filters can be described by a few common
characteristics. The first of these is the frequency range of their pass band. A filter\'s pass band is
the range of frequencies over which it will pass an incoming signal. Signal frequencies lying
outside the pass band are attenuated. Many filters fall into one of the following response
categories, based on the overall shape of their pass band.
Low-pass filters pass low-frequency signals while blocking high-frequency signals. The pass
band ranges from DC (0 Hz) to a corner frequency FC.
High-pass filters pass high-frequency signals while blocking DC and low-frequency signals. The
pass band ranges from a corner frequency (FC) to infinity.
Band-pass filters pass only signals between two given frequencies, blocking lower and higher
signals. The pass band lies between two frequencies, FL and FH. Signals between DC and FL are
blocked, as are signals from FH to infinity. The pass band of these filters is often characterized
as having a bandwidth that is symmetric around a center frequency.
Band-stop filters block signals occurring between two given frequencies, FL and FH. The pass
band is split into a low side (DC to FL) and a high side (FH to infinity). For this reason, it\'s
often simpler to specify a band-stop filter by the width and center frequency of its stop band.
Band-stop filters are also called notch filters, especially when the stop band is narrow.
Figure 1 shows how each of these filters operates on a swept-frequency input signal.
Figure 1. Filters are usually characterized by their frequency-domain performance. The effects
of a few common filter types on a swept-frequency input signal are shown here.
In the examples, the signal increases continuously in frequency, from a low frequency to a high
frequency. When the signal frequency is within the filter\'s pass band, the filter passes the signal.
As the signal moves out of the pass band, the filter begins to attenuate the signal.
Note that the transition from the pass band to the stop band is a gradual process, where the
filter\'s response decreases continuously. Although you can make this transition arbitrarily sharp
(at the cost of filter complexity), it can never be instantaneous, at least not in filters physically
realizable with today\'s technology.
The Bode and Phase Plots
Bode plots describe the behavior of a filter by relating the magnitude of the filter\'s response
(gain) to its frequency. An example of this type of plot is shown in Figure 2.
Figure 2. Filter responses are plotted on Bode plots, wh.
Electromagnetic Flow meters
Blood flow helps to understand basic physiological processes and e.g. the dissolution of a medicine into the body.
Blood flow and changes in blood volume, are usually correlated with concentration of nutrients and other substance in the blood.
Also, Blood Flow measurement reflects the concentration of O2.
IT CONTAINs all the subtopics related to it. it has BloAck diagram, internal working and much more.
Subject; Measurement & Instrumentation
Teacher; ma'am Falak Naz Pathan
MEHRAN UET SZAB CAMPUS KHAIRPUR MIR'S
This presentation is focused on basic understanding of video signal generation and its electronic interpretation. Contents are taken from bible of television!
This presentation is dedicated to R R Gulati.
Singular value decomposition filtering in high-frame-rate cardiac vector flow...journalBEEI
Dysfunction of the left ventricle (LV) weakens the cardiac function and affects the physical activity. Echocardiagraphy has been used to visualize the blood flow dynamics and to evaluate the cardiac function. However, the signal processing to suppress the clutter signals should be employed. In this study, we employed the singular value decomposition (SVD) clutter filtering to obtain the cardiac blood speckle images. We also employed the adaptive thresholding metric to determine the proper cutoff values at each phase during the cardiac cycle. Moreover, we employed a depth-dependent SVD clutter filter for more accurate estimation of the cardiac blood echo signals. The 2D blood flow velocity vectors were estimated by applying the block matching method to obtained blood speckle images. The obtained results show that the proposed filter suppressed the clutter signals from left ventricular wall significantly, and the contrast-to-noise ratio (CNR) was improved from -0.5 dB to 13.8 dB by the proposed SVD clutter filtering.
5. An analog filer has system fnction Ha(s)--a (a) (10 pts,) Comvert .pdfinfo324235
5. An analog filer has system fnction Ha(s)--a (a) (10 pts,) Comvert this analog filter into a
digital iker by means of the bilineasr filter by means of the bilinear trasformation method with T,
= 0.1. (b) (5 pts.) Is this filter FIR or IIR? (c) (5 pts.) Find the poles of this digital filher
Solution
Hundreds if not thousands of different kinds of filters have been developed to meet the needs of
various applications. Despite this variety, many filters can be described by a few common
characteristics. The first of these is the frequency range of their pass band. A filter\'s pass band is
the range of frequencies over which it will pass an incoming signal. Signal frequencies lying
outside the pass band are attenuated. Many filters fall into one of the following response
categories, based on the overall shape of their pass band.
Low-pass filters pass low-frequency signals while blocking high-frequency signals. The pass
band ranges from DC (0 Hz) to a corner frequency FC.
High-pass filters pass high-frequency signals while blocking DC and low-frequency signals. The
pass band ranges from a corner frequency (FC) to infinity.
Band-pass filters pass only signals between two given frequencies, blocking lower and higher
signals. The pass band lies between two frequencies, FL and FH. Signals between DC and FL are
blocked, as are signals from FH to infinity. The pass band of these filters is often characterized
as having a bandwidth that is symmetric around a center frequency.
Band-stop filters block signals occurring between two given frequencies, FL and FH. The pass
band is split into a low side (DC to FL) and a high side (FH to infinity). For this reason, it\'s
often simpler to specify a band-stop filter by the width and center frequency of its stop band.
Band-stop filters are also called notch filters, especially when the stop band is narrow.
Figure 1 shows how each of these filters operates on a swept-frequency input signal.
Figure 1. Filters are usually characterized by their frequency-domain performance. The effects
of a few common filter types on a swept-frequency input signal are shown here.
In the examples, the signal increases continuously in frequency, from a low frequency to a high
frequency. When the signal frequency is within the filter\'s pass band, the filter passes the signal.
As the signal moves out of the pass band, the filter begins to attenuate the signal.
Note that the transition from the pass band to the stop band is a gradual process, where the
filter\'s response decreases continuously. Although you can make this transition arbitrarily sharp
(at the cost of filter complexity), it can never be instantaneous, at least not in filters physically
realizable with today\'s technology.
The Bode and Phase Plots
Bode plots describe the behavior of a filter by relating the magnitude of the filter\'s response
(gain) to its frequency. An example of this type of plot is shown in Figure 2.
Figure 2. Filter responses are plotted on Bode plots, wh.
Rasamanikya is a excellent preparation in the field of Rasashastra, it is used in various Kushtha Roga, Shwasa, Vicharchika, Bhagandara, Vatarakta, and Phiranga Roga. In this article Preparation& Comparative analytical profile for both Formulationon i.e Rasamanikya prepared by Kushmanda swarasa & Churnodhaka Shodita Haratala. The study aims to provide insights into the comparative efficacy and analytical aspects of these formulations for enhanced therapeutic outcomes.
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Integrating Ayurveda into Parkinson’s Management: A Holistic ApproachAyurveda ForAll
Explore the benefits of combining Ayurveda with conventional Parkinson's treatments. Learn how a holistic approach can manage symptoms, enhance well-being, and balance body energies. Discover the steps to safely integrate Ayurvedic practices into your Parkinson’s care plan, including expert guidance on diet, herbal remedies, and lifestyle modifications.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
Muktapishti is a traditional Ayurvedic preparation made from Shoditha Mukta (Purified Pearl), is believed to help regulate thyroid function and reduce symptoms of hyperthyroidism due to its cooling and balancing properties. Clinical evidence on its efficacy remains limited, necessitating further research to validate its therapeutic benefits.
Recomendações da OMS sobre cuidados maternos e neonatais para uma experiência pós-natal positiva.
Em consonância com os ODS – Objetivos do Desenvolvimento Sustentável e a Estratégia Global para a Saúde das Mulheres, Crianças e Adolescentes, e aplicando uma abordagem baseada nos direitos humanos, os esforços de cuidados pós-natais devem expandir-se para além da cobertura e da simples sobrevivência, de modo a incluir cuidados de qualidade.
Estas diretrizes visam melhorar a qualidade dos cuidados pós-natais essenciais e de rotina prestados às mulheres e aos recém-nascidos, com o objetivo final de melhorar a saúde e o bem-estar materno e neonatal.
Uma “experiência pós-natal positiva” é um resultado importante para todas as mulheres que dão à luz e para os seus recém-nascidos, estabelecendo as bases para a melhoria da saúde e do bem-estar a curto e longo prazo. Uma experiência pós-natal positiva é definida como aquela em que as mulheres, pessoas que gestam, os recém-nascidos, os casais, os pais, os cuidadores e as famílias recebem informação consistente, garantia e apoio de profissionais de saúde motivados; e onde um sistema de saúde flexível e com recursos reconheça as necessidades das mulheres e dos bebês e respeite o seu contexto cultural.
Estas diretrizes consolidadas apresentam algumas recomendações novas e já bem fundamentadas sobre cuidados pós-natais de rotina para mulheres e neonatos que recebem cuidados no pós-parto em unidades de saúde ou na comunidade, independentemente dos recursos disponíveis.
É fornecido um conjunto abrangente de recomendações para cuidados durante o período puerperal, com ênfase nos cuidados essenciais que todas as mulheres e recém-nascidos devem receber, e com a devida atenção à qualidade dos cuidados; isto é, a entrega e a experiência do cuidado recebido. Estas diretrizes atualizam e ampliam as recomendações da OMS de 2014 sobre cuidados pós-natais da mãe e do recém-nascido e complementam as atuais diretrizes da OMS sobre a gestão de complicações pós-natais.
O estabelecimento da amamentação e o manejo das principais intercorrências é contemplada.
Recomendamos muito.
Vamos discutir essas recomendações no nosso curso de pós-graduação em Aleitamento no Instituto Ciclos.
Esta publicação só está disponível em inglês até o momento.
Prof. Marcus Renato de Carvalho
www.agostodourado.com
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...Oleg Kshivets
Overall life span (LS) was 1671.7±1721.6 days and cumulative 5YS reached 62.4%, 10 years – 50.4%, 20 years – 44.6%. 94 LCP lived more than 5 years without cancer (LS=2958.6±1723.6 days), 22 – more than 10 years (LS=5571±1841.8 days). 67 LCP died because of LC (LS=471.9±344 days). AT significantly improved 5YS (68% vs. 53.7%) (P=0.028 by log-rank test). Cox modeling displayed that 5YS of LCP significantly depended on: N0-N12, T3-4, blood cell circuit, cell ratio factors (ratio between cancer cells-CC and blood cells subpopulations), LC cell dynamics, recalcification time, heparin tolerance, prothrombin index, protein, AT, procedure type (P=0.000-0.031). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and N0-12 (rank=1), thrombocytes/CC (rank=2), segmented neutrophils/CC (3), eosinophils/CC (4), erythrocytes/CC (5), healthy cells/CC (6), lymphocytes/CC (7), stick neutrophils/CC (8), leucocytes/CC (9), monocytes/CC (10). Correct prediction of 5YS was 100% by neural networks computing (error=0.000; area under ROC curve=1.0).
ABDOMINAL TRAUMA in pediatrics part one.drhasanrajab
Abdominal trauma in pediatrics refers to injuries or damage to the abdominal organs in children. It can occur due to various causes such as falls, motor vehicle accidents, sports-related injuries, and physical abuse. Children are more vulnerable to abdominal trauma due to their unique anatomical and physiological characteristics. Signs and symptoms include abdominal pain, tenderness, distension, vomiting, and signs of shock. Diagnosis involves physical examination, imaging studies, and laboratory tests. Management depends on the severity and may involve conservative treatment or surgical intervention. Prevention is crucial in reducing the incidence of abdominal trauma in children.
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
2. Color AND spectral parameters [contd..]
[3] Wall Filters
•
Wall filters @ selectively filter out all acquired information
below an operator-defined frequency threshold.
•
@ Filters eliminate the typically low-frequency–high-intensity
noise that may arise from vessel wall motion.
@ Filters operate at variable frequencies to eliminate signal from
low-velocity blood flow.
@ Filter settings are usually preset by the manufacturer, and a
high, medium, or low filter setting may be applied separately
to spectral, color, and power imaging.
3. •
“High” refers to the higher range of frequency shifts that are
filtered out and thus are not depicted on the color image or
spectral waveform.
•
In patients with very slow portal venous flow, a high filter
setting may cause this flow to be inadvertently
[unintentionally] obscured or missed.
•
To avoid the loss of signal that characterizes slow flow, filter
settings should be kept at the lowest possible setting
(typically in the 50–100-Hz range).
•
.
4. •
The cutoff frequencies vary with the velocity scale; the
lowest filter cutoff frequencies cannot be used with the
highest velocity ranges and vice versa.
•
On the color bar, the filter setting is indicated by black areas
on both sides of the baseline.
•
•
5. # Expansion of the filter shows up as a widening of the black
band (,,,Fig 10) slide [7]
# On the spectral waveform, a high wall filter setting will
•
result in loss of depicted spectral information immediately
above the baseline. Reducing the wall filter setting results in
filling in of spectral data toward the baseline.
•
6. •
Figure 9. Changing the wall filter.
•
(a) Color duplex US image [slide [7] obtained with a high wall
filter setting shows @ loss of the low-velocity-flow
component of the spectral waveform immediately above the
baseline. @ Higher-velocity flow is well depicted, and
@accurate flow quantification can still occur.
•
(b) Color duplex US image slide [8] demonstrates how the
spectral waveform progressively fills in toward the baseline
as the wall filter is sequentially reduced from high (left arrow)
to medium (middle arrow) to low (right arrow).
8. Figure 9 [b] Changing the spectral wall filter [reduced filter from high to med
to low = arrows]
9. •
Figure 10. Changing the color Doppler wall filter.
•
(a) CFD image slide [10] obtained with the highest possible
wall filter setting shows how color signal arising from low-
velocity flow may be filtered out.
•
## The change in the filter setting appears as a change in the
width of the horizontal black line in the center of the color
bar. Slide [10]
•
(b) CFD image slide [11] obtained with a low filter setting
demonstrates filling in of flow in the hepatic veins (blue),
which indicates minimal filtering of color signal.
•
10. Figure 10 [b] (high filter = filters out signals from low flow velocities)
The change in the filter setting appears as a change in the width of the
horizontal black line in the center of the color bar.
11. Figure 10 [b] filling in of flow in hepatic veins [blue] Changing the color
Doppler wall filter from high to low.
•
12. •
[4] Inversion of Flow figure 11
•
Inversion refers to the ability to electronically invert the
direction of flow as depicted on both the color flow and
spectral waveforms.
•
a) As such, color inversion will result in a blue-red reversal
and may lead to misinterpretation of the direction of flow in
the vessel being evaluated (Fig 11 a/slide 13).
•
b) On a color Doppler flow US image obtained with reversal of
this inversion, appropriate directional flow is noted.
•
[Figure 11 b/slide 14]
13. Figure 11a. Inversion of color flow. Image [color Doppler active mode] on
inversion of the color bar, portal venous flow appears blue, which falsely
suggests reversal of flow (ie, away from the transducer).
14. Figure 11b. Inversion of color flow. On a color Doppler flow US image
obtained with reversal of this inversion, appropriate directional flow is
noted.
15. •
Similarly, inversion of the spectral waveform will switch the
depicted flow curve from above to below (or below to above)
the baseline (,,,Fig 12).
•
Adjustment of the inversion button will alter either the color
or the spectral scale, depending on which is active at the time
of adjustment.
•
Flow toward the TXR typically appears red (at CFD) OR above
the baseline (positive flow) on the spectral waveform and can
be changed simply by adjusting the inversion button.
16. •
Figure 12. Inversion of spectral and color flow falsely suggesting
reversal of portal venous flow.
•
(a) On a color duplex image slide [17] obtained with spectral
Doppler as the active mode, @ the spectral waveform is
below the baseline, @ with appropriate color flow.
•
(b) Color duplex image slide [18] obtained after the inversion
button was reversed demonstrates @ appropriate directional
flow, with the spectral @ waveform now appearing above the
baseline.
•
Note that the color bar does not change when the Doppler
spectrum is inverted.
17. Figure 12 a. Inversion of spectral AND color flow : spectral [active mode], the spectral waveform
is below the baseline, with appropriate color flow.
18. Figure 12 b. Color duplex obtained after the inversion button was reversed
demonstrates appropriate directional flow, with the spectral waveform now appearing
above the baseline.
19. •
(B) Spectral-Specific Parameters
•
[angle correction/ spectral gain/ gate size/ gate position]
•
The spectral waveform contains a host of hemodynamic
information describing the velocity and character of the
blood flow in the specific vessel being insonated.
•
The waveform depicts the spectrum of frequency shifts of all
blood traversing the sampled volume during the period of
data acquisition . With use of the computer to apply an angle
correction, a range of time-dependent velocities are
displayed on the vertical axis (spectral display).
20. •
[1] angle correction
•
Angle correction refers to adjustment of the Doppler angle
and is used to calibrate the velocity scale for the angle
between the US beam and the blood flow being measured.
•
Spectral Doppler US provides both qualitative and
quantitative data about flow velocity.
•
Flow velocity is calculated from the Doppler frequency shift
according to the Doppler equation :
•
V = ΔfC/2focosθ
21. •
Flow velocity is calculated from the Doppler frequency shift
according to the Doppler equation :
•
V = ΔfC/2focosθ
•
where
•
V = velocity.
•
Δf = Doppler frequency shift.
•
C = speed of sound in soft tissue.
•
fo = original transmitted frequency.
•
θ = the angle between the transducer and blood flow.
22. •
Ideally, the direction of flow should be at an approximately
45°–60° angle relative to the transducer.
•
Within this range, a linear relation exists b/w velocity and the
Doppler shifts.
•
Outside this range, the unreliable signal produces inaccurate
estimates of flow (,,,Figs 13, ,,,14).
•
The calculated velocity is inversely related to : the cosine of
the angle b/w the TXR and flowing blood.
•
Because the cosine of 90° is 0, the calculated velocity
approaches 0 as the angle approaches 90°
23. •
Figure 13. Angle correction.
•
(a) Color duplex US image [slide 24] obtained with no angle
correction [angle 0^] shows how no meaningful velocity data
can be obtained from the portal venous waveform because
the computer automatically assigns an angle of 0° (cos 0° = 1).
•
(b) Color duplex US image slide [25] obtained with correct
definition of the angle between the TXR and the direction of
portal venous flow [angle 52^] demonstrates a flow velocity
of 29.3 cm/sec.
24. Figure 13 a : Without angle correction [anle 0^], the measured flow velocity is 18.0
cm/sec.
no meaningful velocity data can be obtained [computer automatically assigned
anangle of 0^ [cosine 0 = 1]
25. Figure 13 b : after angle correction [52^], the measured flow velocity is
29.3 cm/sec.
26. •
Figure 14. Angle correction.
•
(a) Color duplex image slide [27] obtained with a 30°
corrected angle, which is too low, demonstrates a flow
velocity of 21.3 cm/sec [underestimation of true portal vein
flow velocity].
•
(b) Color duplex image slide [28] obtained with a 70°
corrected angle, which is too high, demonstrates a flow
velocity of 52.8 cm/sec in the portal vein, which represents an
overestimation of flow velocity.
•
Note that the measured flow velocity increases as the
corrected angle increases.
27. Fig 14 a : with 30^ corrected angle [too low] = duplex image demonsrated
overestimated flow velocity of 21.3 cm/s
28. Fig 14 b : with 70^ corrected angle [toohigh] = duplex image demonsrated
low velocity of 52.8 cm/s
29. •
The differences between angle correction and angle of
insonation are important to understand.
•
Angle correction specifies the true Doppler angle [b/w beam
& blood flow] by placing the cursor parallel to the direction of
blood flow (,,,Fig 13).
•
Manually applying this correction allows the computer to
solve the Doppler equation.
•
The angle of insonation is the angle b/w theTXR and the
vessel being studied (,,,,Fig 15). The angle of insonation
should also be between 45° and 60°.
30. •
Figure 15. Angle of insonation.
•
(a, b) Color duplex image [slide 31] of the anterior branch of
the right portal vein obtained with the TXR positioned in an
intercostal (a) and subcostal (b) location depict flow as
moving toward [a] and away [b] from the TXR, respectively.
•
(c) On a color duplex image obtained with theTXR positioned
perpendicular to flow (arrow), no color is assigned, yielding a
false finding of absent flow.
•
The angle of insonation of the vein depends entirely on the
position of the transducer.
34. •
UNdercorrection applied to the Doppler angle, will result in a
falsely low flow estimate.
•
This result comes directly from the Doppler equation, in
which the smaller the angle between flow direction and
transducer position, the greater the denominator of the
equation.
•
Flow may appear to be reversed when the beam-flow angle
changes about 90°.
•
Complete loss of flow may be evident when the beam-flow
angle is 90°.
35. •
[2] Spectral Gain
•
The spectral gain setting enhances the intensity of depicted
flow in the spectral display.
•
Gain should be adjusted to outline the contour of the
depicted waveform (,,,,,Fig 16/).
•
Too low a setting falsely suggests absent flow.
•
Too high a setting artificially fills in the spectral waveform,
resulting in falsely increased flow with little meaningful
quantitative flow data.
36. •
gain settings function independently of other parameters,
•
so that changing the percentage of gain applied to an
acquired signal will not alter any other parameter.
•
A change in the color gain does not alter the spectral gain and
vice versa, with the PRF remaining unchanged.
•
Figure 16. Optimization of gain settings.
•
(a) Duplex image [slide [38] obtained with spectral Doppler as
the active mode and too low a gain setting (0%) falsely
suggests absent flow.
37. •
(b-d) Duplex images slides [39/40/41] obtained with a gain
setting of 38% (b), 77% (c), and 100% (d) demonstrate gradual
artificial filling in of the spectral waveform, yielding a false
finding of increased flow with little meaningful quantitative
flow data. changing the gain setting will not alter any other
parameter.
•
Changing the color gain does not alter the spectral gain (and
vice versa), and the PRF remains unchanged. Whether the
color or spectral component is active, the gain setting should
be adjusted to outline the contour of the depicted waveform
or color flow depiction.
•
38. Figure 16 a : spectral Doppler, active mode, too low a gain setting (0%) =
falsely suggests absent flow
42. •
[3] Gate Size
•
The operator-adjusted gate defines the size and location of
the area from which Doppler information is obtained. The
gate is delineated as a pair of cross-hairs within the 2D image
and should be as small as possible to exclude erroneous signal
arising from adjacent vessels or marginal flow.
•
Too large a gate may @ admit erroneous signal from adjacent
vessels (,Fig 17) @ or may lead to acquisition of data from
extraneous parenchyma.
43. •
Too small a gate may @ give the false impression of reduced
•
or even absent flow. @ A smaller gate also reduces
computation time @ and increases the frame rate, thereby
@allowing more accurate depiction of flow.
44. •
Figure 17. Optimizing gate size and position.
•
Color duplex US image slide [45] obtained with @ a wide gate
placed in @ a suboptimal location : shows sampling of flow in
both the portal (above the baseline) and hepatic (below the
baseline) veins.
•
Too large a gate size may result in sampling from too large an
anatomic region.
•
By reducing the gate size and improving the position for
sampling, a normal spectral waveform is obtained.
46. •
[4] Gate Position
•
To maximize depiction of flow, the gate should be positioned
over the central part of the vessel being studied. In central
portions of the liver, where portal and hepatic veins course in
proximity to one another, a small gate should be carefully
placed on the desired vessel to avoid obtaining flow patterns
from adjacent vessels (,Fig 17/slide 45). When helical flow
occurs in the portal vein, as is often seen following liver
transplantation, gate placement over the central part of the
vein will demonstrate expected flow above and below the
spectral baseline.