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Adv. Vas. Son.
Test 4 TCD
| Question | Answer |
|---|---|
| Facts about the TCD "Free-hand" Method | No imaging, Relies on sample vol depth, flow direction, & vel to identify vessels, Can be performed bilaterally, Simultaneously w/ proper gear |
| Facts about the TCD "Free-hand" probe | Single crystal-2 MHz Doppler, multi-gated Doppler, Small footprint TD |
| What is used with TCD imaging? | Phased array, B-mode image, Color, Spectral, Unilateral method |
| What is TCD & TCI used to serial monitor? | MCA & other intracranial vessels for vasospasm |
| What is TCD & TCI used to evaluate? | Intracranial aneurysm & arteriovenous malformation, Basilar artery occlusion, Intracranial ICA stenosis, Monitoring vasospastic effects of sickle cell anemia, Confirmation of brain death |
| TCD & TCI is an adjunct to what? | Extracranial exam |
| Basilar artery forms from what? | The verterbrals in the back of the head |
| What are some exclusive applications of TCD? | Microemboli detection during carotid surgery, CABG & carotid PTA/stenting, Cerebral autoregulation-vasoreactivity to CO2, Detection of Rt-Lt cardiac shunts, Monitoring of real-time blood flow to brain during surgical procedures |
| What does PTA stand for? | Percutaneous transluminal angioplasty |
| Transcranial surveillance for micro-emboli using bilateral TCD TDs do what? | Monitor both hemispheres simultaneously, Record long periods of Spectral Doppler info, 2 MHz TDs are inserted into the lateral probe holders & adjusted to receive signal from the MCAs |
| Opthalmic artery facts: | Feeds the eye, is the first major branch of the internal carotid artery (ICA) |
| Petrous ICA facts: | Courses through the petrous portion of the temporal bone & is inaccessible to ultrasound |
| Cavernous ICA facts: | AKA the Carotid Siphon, Consists of: Parasellar portion, Genu portion (the bend), & Supraclinoid portion (distal segment) |
| What is the course of the Middle Cerebral Arteries (MCA)? | Laterally towards the temporal cone with a number of branches |
| MCA facts: | Carry 75-80% of ICA flow, Larger than the ACAs |
| M1 segment facts: | From the MCA origin to the first branch |
| M2 segment facts: | MCA distal to the first branch |
| What is the course of the Anterior Cerebral Arteries (ACA)? | Medially towards the midbrain (A1 segment) |
| ACA facts: | Gives rise to the anterior communicating artery (AcoA), this vessel courses between the 2 ACAs |
| What is the course of the A2 segment? | Anteriorly to supply the anterior segments of the brain |
| Patients with incomplete circles are more likely to experience what? | Stroke in the present of carotid artery stenosis/occlusion, Collateral pathways are significantly reduced, Posterior & anterior communicating arteries provide collateral pathways w/in the COW |
| In the presence of an ICA occlusion what will happen? | Flow from the contralateral ACA can "cross=fill" via the anterior communicating artery, Flow will course retrograde in the ipsilateral ACA to supple the MCA and the lateral hemisphere |
| Other collateral pathways that may develop with ICA occlusion include? | Retrograde flow in supraorbital & branches of the ophthalmic artery, This pathway reconstitues the supraclinoid segment of the ICA w/ blood flow being supplied by communicating ECA branches |
| Flow can reverse direction in the supraorbital arteries (supplied by the ECA branches) to provide what? | Blood flow to the distal ICA |
| Posterior Cerebral Arteries (PCA) facts: | Perfuse posterior hemisphere, Wrap around the cerebral peduncle, P1 segment courses from origin (Basilar a.) to posterior communicating artery(PCoA), P2 segment is distal to the PCoA |
| What are the 4 common approaches for Intracranial exam to look at the cerebral vasculature? | Trantemporal, Transorbital, Transoccipital, and Submandibular |
| Transtemporal TCD window facts: | Over temporal bone & superior to the zygomatic arch (cheek bone), 65-70% loss of US energy due to bone structure & size of acoustic "window", No access in 10% of population due to thickness of bone segment |
| What might affect the bone thickness for a transtemporal window? | As people age it gets thicker and post-menopausal women |
| What arteries are accessible with the transtemporal window? | MCA, ACA, MCA/ACA bifurcation, PCA, Terminus ICA, PCoA & ACoA maybe, if functioning as collateral pathways with lots of flow |
| What are the TCD windows for transoribital? | ICA siphon, Ophthalmic artery, Must use very low Doppler output power for this window!!!!! |
| Lower output power for what view? | Transorbital |
| What are the TCD windows for the Suboccipital- Foramen Magnum? | Basilar artery, and Vertebral arteries |
| Circle of Willis (COW) Anomalies: | 50% of the pop have an intact & functioning COW (estimated), Only 25% have the classic configuration, W/ a disrupted COW, the ability to perfuse from the contralateral side is impaired |
| TCD method MCA: | PT supine, tech @ head of bed, Apply gel to temporal region, Use a LARGE sample volume (5-10mm), Sample vol depth to 50mm!!!!! |
| What technique should you use for the MCA? | "Flashlight" technique moving TD to locate the MCA, MCA flow should be TOWARDS the Doppler beam |
| TCD method and Vessel identification: | Optimize Doppler signal & record WFs, Don't angle correct, leave angle cursor set to 0 (parallel with the Doppler line), Measre peak mean vel, Don't invert Doppler, Depth of vessel (by range gate), Flow direction, Mean vel value |
| What is the most important things with TCD method and vessel identification? | Depth of vessel and flow direction |
| Mean velocity for TCD means what? | Mean velocity peak- over time |
| TCD method Bifurcation facts: | Move the SV to a shallower MCA depth, then "Step" the SV towards the MCA/ACA bifurcation, |
| When you record bidirection flow at the bifurcation what should the depth be? | 5.5-6.5 cm depth |
| Bidirectional flow mean what? | You are in the bifurcation |
| TCD method ACA: | Angle the TD slightly anterior,↑ SV depth & identify the ACA, |
| ACA flow is what? | Away from the TD |
| What depth should you follow the ACA to? | Midline @ 7.5-8.0 cm |
| Record ACA WFs & measure mean velocity, the ACA velocity should be less than? | MCA |
| MCA goes ________ the TD and ACA goes ______ the TD? | MCA toward, ACA away |
| TCD method PCA: | Start w/ SV @ birfurcation depth & angle TD posteriorly & inferiorly |
| Once PCA signal is detected move SV depth to what? | 75 mm, Flow in P1 segment should be "towards" |
| Depth of SV, Flow direction and Mean velocity for MCA: Transtemporal: | Depth of SV=3.0-6.0 cm, Flow direction=Toward, Mean vel 55± 12 cm/sec |
| Depth of SV, Flow direction and Mean velocity for MCA/ACA bifurcation: Transtemporal: | Depth of SV=5.5-6.5 cm, Flow direction=Bidirectional, Mean vel=N/A |
| Depth of SV, Flow direction, and Mean velocity for ACA (A1): Transtemporal: | Depth of SV=6.0-8.0 cm, Flow direction= Away, Mean vel=50±11 cm/sec |
| Depth of SV, Flow direction, and Mean velocity for PCA (P1): Transtemporal: | Depth of SV=60-7.0cm, Flow direction= Towards, Mean vel=39±10 cm/sec |
| Suboccipital - Foramen Magnum: | Basilar, Vertebrals |
| TCD method- Vertebral Basilar: | PT lying on side, pillow under head w/ chin tucked towards chest, Place TD to one side of midline & 1 inch below base of skull |
| With TCD method- Vertebral Basilar where should you start with SV depth? | Start w/ SV depth @ 60 mm, aim @ bridge of nose to identify vertebral artery |
| How should the flow be for the Vertebral Basilar? | Flow should be Away |
| TCD method Follow the course of : | The VA, by stepping the SV, to the basilar artery (BA) |
| What should be the depth of the Basilar artery? | 80-90mm- Follow BA as far (deep) as possible |
| How should the flow be for the Basilar artery? | Flow should be Away |
| Depth of SV, Flow direction and Mean velocity of the Vertebral: Suboccpital: | Depth of SV=6.0-9.0 cm, Flow direction= Away, Mean vel= 38±10 cm/sec |
| Depth of SV, Flow direction and Mean velocity of the Basilar: Suboccipital: | Depth of SV=8.0-12 cm, Flow direction=Away, Mean vel=41±10 cm/sec |
| What should the system transmit power be reduced to for the transorbital approach to prevent damage to the eye? | 15% |
| For the transorbital approach what do you do with the TD? | Place TD over closed eyelid & aim in a slight posterior direction & slightly towards midline |
| What should the SV be set to for the OA? | 50 mm |
| With transorbital how should the flow be? | Flow should be Towards the TD |
| For transorbital step the SV along the length of the OA to the ICA at approx. what depth? | 55-70 mm depth |
| OA flow is what resistance? | HIGH resistance |
| ICA flow is what resistance? | LOW resistance |
| Depth of SV, Flow direction and Mean velocity of Occipital artery: Transorbital: | Depth of SV=4.0-60 cm, Flow direction Towards, Mean velocity=21±5 cm/s |
| Transcranial Color Doppler Imaging (TCI) facts: | B-mode imaging, Color Doppler, Pulsed Doppler, Much easier than TCD, Small footprint, Low freq phased array TD, 1-3 or 4 MHz |
| TCI method: | From transtemporal window, identify the temporal lobe of brain, or the boney structures near the lobe. Set field of view to 12-14 cm. Turn on color and optimize |
| MCA will course along what? | The Anterior side of the temporal lobe |
| TCI method cont: | The onscreen orientation is the sa,e for both the left and right sides, Follow the same methods as TCD, Verifty flow direction and obtain mean velocity measurements in all vessels |
| MCA Flow, SV Depth and Mean velocity: | Flow= Towards, Depth=3.0-6.0 cm, Mean vel=55±12 cm/s |
| What does TAP mean? | "Time average peak" or peak mean velocity |
| MCA/ACA bifurcation Flow and SV Depth: | Flow= Bidirectional, SV Depth= 5.6-6.5 cm |
| ACA Flow, SV Depth, and Mean velocity: | Flow=Away, Depth=6.0-8.0 cm, Mean velocity 50±11 cm/s |
| PCA Flow, SV Depth, Mean velocity: | P1- Flow= Towards, Depth= 6-7cm, P2-Flow=Away, Mean vel=39±10 cm/s |
| Cerebral Aneursym rupture rate? | Approx. 28,000 individual annually, Mortality rate exceeds 50%, Survivors face aneurysm clipping limitations, Aneurysm coiling-Technology w/ fewer MRI limitations |
| Cerebral Vasospasm facts: | Subarachnoid hemorrhage (SAH) may cause cerebral vessel vasospasm; if severe, can result in stroke Spasm is commonly delayed in onset (days later)(following SAH or surgical aneurysm repair) |
| Serial TCD or TCI monitoring can detect the onset, severity, & effects of treatment of what? | Cerebral Vasospasm |
| Treatment for Cerebral Vasospasm may include what? | Potent vasodilators &/or angioplasty (PTA) (Vasodilator applied just PROX to spasm via catheter) |
| Cerebral Vasospasm facts: | Range from mild to severe, May occur in any major cerebral vessel |
| Cerebral Vasospasm symptoms: | Confusion, Decreased level of consciousness, Stroke, Death |
| Vasospasm Method: | If necessary, have PT sedated, Move or remove temporal bandages, Use sterile acoustic gel on the side of the incision, Use transtemporal window, perform a bilateral baseline TCD/TCI exam |
| What is the most common vessel invloved with a vasospasm? | MCA |
| Vasospasm method: | Investigate the entore MCA w/ Color & Spectral Doppler, Look for regions of focal Velocity acceleration, Record the highest mean velocity, note the depth of SV for follow-up, Diagnosis of vasospasm is based on high mean velocity |
| TCD Vasospasm Mean velocity NORMAL: | 30-80 cm/s |
| TCD Vasospasm Mean velocity MILD: | 120-140 cm/s |
| TCD Vasospasm Mean velocity MODERATE: | 140-200 cm/s |
| TCD Vasospasm Mean velocity SEVERE: | >200 cm/s |
| Some labs include an MCA/ACA ratio (mean velocities) of ______ is consistent w/ severe vasospasm: | ≥ 6.0 ratio |
| Lindegaard Ratio means what? | Mean velocity in the MCA/ mean velocity in ipsilateral extracranial ICA |
| What can be injected into the MCA to reduce Vasospasm? | Papavarine |
| TCD for MCA vasospasm pitfalls: | Skull penetration, Brain swelling (displaces anatomy depth), Metal clips can block US signal, PT cooperation |
| The following can cause emboli to the cerebral vessels: | Cardiac surgery, Carotid endarterectomy, Carotid angioplasty & stenting |
| What can be used to detect emboli during the procedures? | TCD |
| Cerebral Emboli Detection facts: | High intensity transient signals (HITS) AKA, Micro-embolic Signals (MES) |
| What causes a chirping sound on Doppler? | Air-bubbles |
| What are some examples particulate matter? | Platelets, atheromatous, debris |
| Emboli detection: Intraoperative Monitoring: | Performed w/ head gear & 2 TCD TDs for Bilateral exam, Assess bilateral MCAs, Unilateral exams also possible |
| Emboli detection: Intraoperative Monitoring Facts Conti: | TCI is not used for this, Monitoring usually performed for @ least 20 mins |
| Why is Automatic emboli counter software is useful to count # of MES? | Problem: MES or artifact?? High-end TCD systems use multiple sample gates for each Doppler, MES can be "plotted" as they course through multiple MCA SVs, Color M-mode is also used to detect emboli |
| Microembolic signal: | Duration less than 300 msec, Signal is unidirectional w/in the Doppler spectrum (unless it's a shower), Snap or chirp sound on Doppler audio, Should appear in all unilateral Doppler SVs |
| Detection of Rt to Lt cardiac Shunt-PFO: | PFO= Patent Foramen Ovale, A connection between the Lt&Rt atria, Due to inadequate postnatal closure of the Foramen Ovale, Can allow emboli arising in the venous system to pass to the arterial circulation through PFO |
| What can an emboli arising in the venous system to pass to the arterial circulation through PFO result in? | Can result in cryptogenic stroke from paradoxical emboli |
| Prevalence of PFO: Young stroke PTs: | 40-50% |
| Prevalence of PFO: PTs w/ cryptogenic stroke: | 42-77% |
| Prevalence of PFO: Normal controls: | 10-30% |
| Test for PFO: | PT supine, Intravenous line is placed, Bilat TCD headgear is mounted & MCA Doppler signals obtained, Microbubbles created by mixing saline & air is injected into the IV line, PT then performs a valsalva maneuver |
| If there is no Rt to Lt shunt what happens? | Bubbles go to lungs and dissipate |
| Test for PFO Cardiac Shunt: | If shunt exists bubbles will go to the MCA & are detected w/ bilateral TCD monitoring, A micro bubble "shower" occurs, More HITS= More severe shunt |
| Application of Intracranial Exams- Sickle Cell Disease: | sickle cell PTs are prone to stroke involving MCA & ACA, Early detection of MCA vels by TCD w/ subsequent initiation of blood transfusion successfully reduces rate of 1st stroke |
| NORMAL MCA velocity regarding sickle cell: | <170 cm/s |
| BORDERLINE MCA velocity regarding sickle cell: | 170-200 cm/s |
| ABNORMAL MCA velocity regarding sickle cell: | >200 cm/s |
| Children with sickle cell disease undergo what? | Routine annual TCD screening |
| Application of Intracranial Exams- Brain Death: | Along w/ clinical criteria & EEG findings, TCD can be used to confirm brain death, Cerebral circulatory arrest produces classic to&fro TCD WFs (Short sys spike followed by either a small retrograde deflection in diastole or no flow in diastole) |
Created by:
EmilyGriffin
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