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Introduction Disclosures and Objectives | Introduction to MR Guided Focused Ultrasound
Introduction Disclosures and Objectives | Introduction to MR Guided Focused Ultrasound
2017AVIRfibroidfocusfocusedguidedinterventionalmichiganprocedureultrasound
Background of MR Guided Ultrasound and Current Uses | Introduction to MR Guided Focused Ultrasound
Background of MR Guided Ultrasound and Current Uses | Introduction to MR Guided Focused Ultrasound
2017ablationAVIRchapterenergyfibroidsfocusfull videohospitalizationmetastaticmicrowavepatientprobesultrasound
Physics - Thermal and Mechanical | Introduction to MR Guided Focused Ultrasound
Physics - Thermal and Mechanical | Introduction to MR Guided Focused Ultrasound
2017ablationablativeacousticarteriolesAVIRbiggerbubblebubblescavitationcentimeterchaptercoagulativecoagulumcoolingdepositionembolizationenergyfibroidsfluidsforceforcesformationfull videoheatlensmechanicalmicronecrosisproximalradiationsonicationsoundstabletargettissuetissuestumorultrasoundwavewaveszone
Equipment MRI - Advantages and Disadvantages  | Introduction to MR Guided Focused Ultrasound
Equipment MRI - Advantages and Disadvantages | Introduction to MR Guided Focused Ultrasound
2017AVIRchapterfull videoimprovedmethodmonitoringMRIresolutiontechniquesultrasound
Transducer Basics - Single Element and Array Transducer | Introduction to MR Guided Focused Ultrasound
Transducer Basics - Single Element and Array Transducer | Introduction to MR Guided Focused Ultrasound
2017ablationAVIRchapterfocalfull videomultiplesonicationtransducertumorultrasoundzone
Procedure - Uterine Fibroids | Introduction to MR Guided Focused Ultrasound
Procedure - Uterine Fibroids | Introduction to MR Guided Focused Ultrasound
2017ablateablationablativeAVIRchapterfavorablefibroidfibroidsfull videointenseMRImultipleperfusedprocedurerectalsonicationstructurestransducertreatmenttypicallyultrasounduterinezone
Limitations and Future Treatment Directions | Introduction to MR Guided Focused Ultrasound
Limitations and Future Treatment Directions | Introduction to MR Guided Focused Ultrasound
2017ablationAVIRbonecentimeterchapterfibroidsfull videoimpedancemalformationosteoidosteomapatientskinstructuressurfacetumortumorsultrasoundvessel
Transcript

speaker dr. Nicholas Romano received his doctor of medicine from wright state university he then completed a diagnostic radiology residency at the Medical College of Wisconsin where he also served as chief resident he's currently a vascular and interventional

fellow with the University of Michigan and today he will share his expertise on Mr guided focused ultrasound with our group please welcome to the podium thank you today we're talking about my guided focused ultrasound just kind of off the

bat it's this kind of a yes or no type of procedure either places do quite a bit of it and have their own protocols firmly entranced or it's something that's kind of you know unique and not seen very often so I want to just give

an overall kind of basic idea of what the procedure is and kind of some examples no disclosures so again background up as far as high intensity focused ultrasound which mr guy to focus our son is a subset current uses some

basic physics involved that the procedure the equipment evolved the procedure and for this i'll use uterine fibroid treatment kind of as the prototypical procedure just because it's the most commonly performed and you can

derive a lot of other procedures from that procedure limitations of the mr gotta focus letter center than future directions so similar to other

techniques we have such as radio frequency of microwave my guy to focus

on Santa's in a blade of therapy where we are depositing energy within a target again similar to our ephraim microwave it's primarily heat but those also some mechanical energy involved as well what sets it apart is that it's entirely

non-invasive we're not putting probes or needles or anything into the patient all the energy sources which are the ultrasound probes are outside the patient either along the skin surface or in body cavities the nice thing users no

not ionizing radiation and it does have the another benefit that potentially having quicker recovery where most patients are discharged same day and you can decrease hospitalization costs so just some time line again this is really

high-tech focus alter Center hi foo been around since the 40s the first you know experiments were in animal models that we moved into the 40s and 50s where we can't have the godfathers of high foo

being the fryed brothers at university of illinois did trials with animals followed by humans the first human usage was in a neurosurgery patient required to Train craniotomy before it can be performed they moved on as you can see

to cancer treatments bph and the first mr gotta focus autosound was in the early 90s so today the fda has approved mi gotta focus on for three uses that's uterine fibroids bone pain from metastatic disease and then most

recently essential tremor the ultrasound guided version ultrasound hi foo is also you can be used for prostate ablation but there's not an mr approved at least the united states for mi gotta focus on sound so some basic physics as i said

before the major mechanism of action is thermal ablation or the deposition of heat within a target and this is caused by friction more or less from the sound waves the ultrasound waves as they pass through a target there's also some

mechanical forces involves being and you can divide us in different ways but cavitation or bubble formation and then acoustic streaming i'll talk about both of these cavitation you can have stable or inertial and then with acoustic

streaming there's micro streaming and radiation force doesn't really fit into this category but it's the closest i could find a how to categorize these things and i get i'll talk about that in a second here so stepping back as we're

depositing heat how much heat are we giving so just kind of as a reference for diagnostic ultrasound that we use every day for image guidance the typical deposition of energy that the government lets us use is about seven tenths of a

watt per centimeter squared usually though it's much less than that it's very fun frequent to go above about point one but in high food we're talking about which again I marketa focused ultrasound is a subset we're talking

orders of magnitude higher so one hundred to a thousand watts per centimeter squared and then as you give this you alternating at periods of giving energy or the sonication and then cooling so the great

example of fibroids about 10 to 30 seconds of sonication followed by about 45 seconds 120 seconds of cooling and why this is is that if you can imagine like a magnifying lens trying to use the sunlight tonight if I on a spot even

though that one spot gets the hottest you still have sunlight going through the other tissues beforehand just the same way with ultrasound so if you left that on for long enough even though you're not targeting those near field or

tissues proximal to your ablation zone they're still going to heat up and then our temperature targets are the same as in other ablative methods so typically it's either 56 41 seconds but usually it's much more than that we're 65

degrees Celsius the usual target for coagulative necrosis and as part of this kind of a side effect of the coagulum necrosis you also get some embolization of arterioles or arteries that also act to the to kill the tumor or the

treatment area so the moving out of those mechanical forces so cavitation so again we're forming bubbles as the sound waves move through tissue and and fluids you have to type stable cavitation which just means as that sound wave goes back

and forth you have a bubble that stays relatively stable and kind of grows and shrinks as the sound wave moves through it and this can act like a little tiny lens inside the tumor or inside what you want to treat to kind of focus those

ultrasound beams then you have inertial cavitation which is as your sound waves go through the tissue these bubbles just keep getting bigger and bigger and bigger and so they pop when they pop they release a whole lot of energy and

you can see local heating is pretty impressive now you would think this would be an excellent method or an adjunct to it's very difficult to control and if you have any that's happening around your treatment zone it

can lead to non-target ablation so kind of a graphic representation of that above the the a there is kind of stable cavitation so as that sound wave moves to and fro and your tissues expand and contract you have this bubble that

expands and contracts with it and stays relatively stable whereas with that inertial cavitation the bubble just gradually increases in size until the inertia of it's shrinking and getting bigger overcomes the stability of the

bubble and it just pops violently and energy and there's acoustic streaming which is basically just these bubbles or other forces cause flow of fluids in a type of high-velocity flu fluid movement which can cause poor formation or

disruption of cell membranes so micro streaming is just the motion the bubble getting bigger and smaller itself Ghazis fluids the move and then radiation force is kind of almost like you're writing on a you know a surfer riding on a wave

where these waves constantly are pushing bubbles in one direction and can cause mechanical force against the cell membrane or tissues so moving on to

equipment so obviously we're using MRI for mr gotta focus alter sound and this

is really kind of comparison to the I don't say older method but the other method of using ultrasound a guide focused ultrasound so the event is there MRI is that we can use it kind of one-stop shopping you can use it for

treatment planning it's improved targeting because of improved spatial resolution and resolution between different tissues you can monitor temperature in real time which is important to make sure you're not uh

plating things around the target that you don't want to be and then you can do techniques immediately afterwards to see how well you did disadvantages would be obviously need all the MRI study protocols in place you can't have that

real-time monitoring that you would with the ultrasound although there are some techniques that are somewhat real-time monitoring and there's increased costs

involved so that I'm moving up to the ultrasound part the older methods use a

single element transducer and Cecilia's basic I just means there's one ultrasound element making all the energy and you have to move the transducer between us on occasions in order to get an incomplete volume each sonication or

focal zone usually is only about a couple millimeters about a couple millimeters so you're talking an oval-shaped ablation zone it may be one to three millimeters by five to eight millimeters so you can imagine if you

have a huge tumor you're gonna have to do that quite a bit and it's going to be quite lengthy never too late the whole thing and then we have the more newer and more frequently used or rage transducer so you have multiple extra

sound elements and each of those can be steered electronically and also you could have a bigger ablation zone so looking at that multiple array you can see you can either use it to make multiple focal

points or multiple ablation zones or you can have one and you can electronically steer between targets instead of having to physically move it so moving on to

the procedure and again I'll use uterine fibroids as kind of the example you have

several phases which starts off with plating you have to determine what the volume what you want to ablate is if you have a large uterine fibroid that's going to take greater than 180 minutes you already know you're going to have to

do multiple sessions except the amount of times the FDA will allow for one session you can also determine composition and one thing that's nice at least with uterine fibroids is depending on how it's that enhances but how

intense how t to HiPo intense those lesions are on MRI you can Sherman have favorable response you're going to get and then location so this is probably the big thing besides time that could be a limitation of this whole thing is you

can't have structures either in the ultrasound path or around the ablative zone that you don't want to have not target the ablation of so then you move to pre procedure and this is plus or minus that typically you have and this

is for uterine fibroids again all that hair is shade from the front of the the person is going to be laying on their stomach nice to prevent air trapping so whenever you have two different structures with different impedances

you're going to have reflection of the sound waves so if you get air trapped between the skin surface and the transducer gel or pad you can have heating of the skin there collect on the transducer which has different acoustic

coupling agents will see a picture here in a second plus or minus as far as the rectal on bladder feel that can be used for two reasons wants to prevent air for being in the way and second of all can be used to displace structures such as

bow away from your ablation zone and any performing immediate treatment mr immediately prior procedure again assessing for intervening structures and also to put targets on of where you want to ablate and its abilities are done

with moderate sedation so yours to tick is an example so this is just a on the left just an idea what the patient's going to look like you can see laying prone on the MRI table with the focus ultrasound beneath them and then I'm

going to write you have an example of that targeting process where you target in three different dimensions there are three different projections and those little circles you see are the ablation zone so each one is a separate

ablation you start off with a testing phase just to make sure that your ultrasound on your mr are synced so to speak so you give a little bit of ultrasound make sure it's heating up the right place and then you move on to the

treatment phase so you have these high-energy sonication followed by cooling and then in real time you can follow to see how well you're doing as far as raising temperatures and here's an example of that I Phillip so that top

left box there you have these little dots that show you how hot the areas are getting and you can see outside of the treatment area how those areas are getting and then you have a graph that shows how long they've been at that

temperature so post procedure as I was talking about before you can do it immediately afterwards we do an enhanced Mr sequence to show you how much of that tissue is no longer perfused or no longer getting blood flow to it and it

ranges it varies but kind of a number you can shoot for is if you have greater than eighty percent then about eighty percent of people after six months will have significant improvement in their pain scores after this treatment they're

typically discharged the same day on incense and here's an example of that the non perfused volume so before and after and this is about at eighty percent you gotta remember looking at multiple slices when we're calculating

that I said of just this one image so

limitations is was playing about before depending on the volume of your tumor and how much energy you're giving it a time these can be long treatment time so we're talking three to four hours of

everything positioning patient and whatnot for fibroids it can be longer another you know so it's like a bone tumors can be even longer requiring general sedation to keep the patient still you had to have an amenable window

for these ultrasound waves that go through so you have structures even scars in the in the path of the beam you can have issues and as we talked about things like airbone have large impedance differences and reflect these ways away

from your target if the patient moves it's a problem usually when there or when they are for fibroids they have a little buttons that they have to move it through and pain and they push that button to stop it and there's a heat

sink effect so if it's next to a vessel that vessel remove heat from the area and then as far as some specific risks you have non-target ablation such again in thyroid there structures ovaries and whatnot and then

the risk of skin burn so besides just that problem with you know coupling at the skin surface if the ablation zones with the one about a centimeter of the skin surface you have real risk of skin burns there are some devices that have a

built-in cooling mechanism on the ultra the ultrasound portion that can help prevent that at least to a degree and there's many future directions as far as treatment goes prostate would be probably the one of the big ones breast

cancer bone tumors benign malignant such as osteoid osteoma and then solid organ tumors as well and then I think just today at I say our later on they're going to be giving a talk about that's their more malformation and being

treated with mr medical shelter soon and that's all our next

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