Shock waves are not sound waves. If you look at a sound wave, and I'll give you a picture of it ¾ sound waves are sinusoidal, they go up and they go down, a shock wave goes up and then it decays. And so what happens when that happens is, if you have a burst of waves coming from one place, that one wave, the decay slows down and the others catch up with it, so what happens is there's a wave front that gets created, so that's what you see when a bomb goes off, actually, there's this shock wave. When patients ask me, what is it that's breaking up the stones, I use the bomb analogy. If a bomb goes off across the street, the building on that side of the street gets knocked over. There's this wave of compression that travels through the air and, in our case water when we're using antibiologic systems, that is absorbed when it reaches a different acoustical interface, the building, or in our case the stone.
There are multiple frequencies; as opposed to a sound wave which is all one frequency, shock waves have multiple frequencies, and this has something to do with what the force of the wave is and its destructive capacity. So on the left is the diagram of what a sound wave looks like, and on the right a shock wave. Again, there's a sudden impulse and decay of the wave.

Chapter Two - EFFECTS ON CALCULI

What happens when that wave travels, and it travels through water and the body, since the body is about 85% water, so there's very little attenuation unless it reaches an acoustic interface where the transmission of the wave is different. So when it reaches a place, say, a water-air interface or a water-stone interface, the transmission different, so some of that energy is absorbed, some of it is reflected. The energy that's absorbed actually goes through the stone and then when it tries to come out the stone at the end, again, it reaches, again, an acoustic interface and there's actually some distraction of the stone at the far end and some people have theorized that that actually has a major effect on the stone; it's not that you're actually crushing it by snapping it into itself, although there is certainly that aspect of it when the wave hits the front side of it but, actually, you're pulling it apart from the backside. This all occurs in microseconds and it results in fissures in the stones, multiple cracks, and the thing starts breaking up into little pieces. And it gets to the diagram of that at "A" is where there's the compressor force, "C" the wave has been absorbed into the stone, and "B" there's this tensile force that distracts the pieces from the stone.

Chapter Three - FOUR COMPONENTS OF LITHOTRIPTERS

How do you put that together to make a lithotripter? There are four components of all lithotripters. One thing you've got to do is you've got to create the shock wave, the second thing you have to do is focus it on the stone, couple the shock wave from where it's being made into the patient, and then you have to have some means of localizing the stone, so those are the components of all shock wave lithotripters.

Chapter Four - SHOCK WAVE GENERATION

One that is used on the Medstone machine and on the majority of machines is the spark gap. Just like the Eurolith machine uses an electric spark, we use a spark plug. If you look at what's generated, it looks very much like an automobile spark plug, it's about 5-times the size of it, a little bigger, it's a spark plug, and a spark is discharged over that gap and there's an explosion, basically, underwater that's caused by that and it's the shock wave that comes from that explosion that we're using to break up the stone. You want to make sure that from wherever the shock wave was generated that there's no difference in acoustical interface between where the shock wave was generated and where it's going, and so you can use water. The original shock wave lithotripter was in a big tub of water. We had this big power lift hydraulic chair. We put the patient in and drop them down into this huge tank of water, and so that was probably the best coupling because there was no possible loss of power across any interfaces. It's been found that if you just use acoustic gel, and in our case with the Medstone machine, mineral oil, there's very little loss of the power and of the shock wave, and so you really don't need to be dumping patients in tubs of water, and so we now have what we call dry lithotripters or the tabletop models that we use today.

Chapter Five - FOCUSING

You can see there's a little wave line under the patient's axilla there, but basically there's your parts of the machine: the generator, the coupling and the localization on this machine was by x-ray, you would get the stone in two planes. This is the ellipsoid deflector. If you remember back to your high school geometry, if you think of a perfect ellipse, and you take at any F1 point and go to any point on the ellipse and draw the angle that comes off that, they all have to meet at an F2 point, and that's the theory behind an elliptical deflector. If you put the spark at an F1 point, no matter where it goes, it has to come back out to that F2 point.

Chapter Six - LOCALIZATION

It's going to focus at that F2 point. And so the spark is discharged at the F1 point and then using your localization mechanism you put the stone at the F2 point. For your purposes, for gallstone lithotripsy you localize it with an ultrasound machine, which is #5 here. It's actually a very ingenious method of doing it. Ultrasound has attached to it a light sensing system. It has 6 red lights on it along an array on top of the ultrasound probe. It's like a little shield that goes over your hand when you're holding the ultrasound and in the ceiling are sensors that sense the angle and where exactly those 6 lights are and that can tell the machine then where the stone is. It's very ingenious.

Chapter Seven - PHYSICAL EFFECTS

There is some slight attenuation of transmission through tissue. The pressure that's generated is about 14,000 pounds per square inch, but you do lose energy when there's a different acoustical interface, and the place where that really occurs in the body is air. In our patients, I tell them to take some Mylicon to try to decrease the amount of bowel air as possible. We're going through the retroperitoneum so there's rarely air between where I'm generating the shock wave and where the shock wave is going to be developed. Again, you'll be close to the abdominal wall, there's not going to be much air between the abdominal wall and the gallbladder, so I don't think it's going to be much trouble. I'll tell you where it can become a problem, though, is in children. I doubt there's many children with gallstones that you'll be treating, but we treat a number of children with stones, and their lungs when they take a deep breath, the diaphragm is just above the kidney and you can actually shock wave the lung and when there's that acoustical interface we have seen some hemoptysis ¾ haven't had anybody get in any trouble with it, but they can create some damage there.
We've also had the opportunity to operate one time, very early in our experience, and of note was that there were petechiae around the bowel when we did do that surgery and I'm sure that's because there was an air-water interface at that point. There was no problem with the patient, just notice that there were these small petechiae along the bowel.

Chapter Eight - BIOLOGICAL EFFECTS

So there are some biological effects. If blood is not moving and you've just shock waved into a tank of blood, you would get hemolysis. Since the blood is constantly moving, very little of it is hemolyzed. There are surface skin hematomas and retroperitoneal hematomas that you'll see. We have rarely had a problem. In the now 15 years that I've been doing lithotripsy I have had to hospitalize one patient for bleeding and that was a patient who happened to be on aspirin and didn't let us know. Other than that I have not seen in my own personal experience anybody have any severe bleeding from this.
All of the patients will have some hematuria. Those patients will have cranberry-colored urine for 24 hours or so, so there is some bruising of the organ in and around where the shock waves are delivered. It's been studied in multiple studies. There does not seem to be any long lasting ill-effect on renal function, and I mentioned the hemoptysis in children because the lung is so close.
On the right you'll see a small hematoma here in the kidney ¾ these are animal kidneys, obviously, and this is a juvenile animal kidney and you can see the extent of damage is quite a bit more for the same energy application.

Chapter Nine - MEDICAL USES

So the medical uses of shock waves to date, and it's growing seemingly weekly, urinary stones, obviously, has been the most popularized now biliary stones, which Dr. Ertan will introduce you to. It's been used in the carotid gland for carotid stones, and coming onboard are many orthopedic applications for calcified tendonitis in the heels, specifically, using it for fracture non union, to make micro fractures so it'll heel better, and those patients who are having artificial joints, two reasons, to try to loosen it up to get it out of there and, secondly, to try to fix a loose joint but again creating micro fractures that re-heal.

Chapter Ten - UROLOGIC CASE

This is just a urologic case. This actually is kind of a show-off case for me because this is a stone that we normally would not recommend shock wave lithotripsy. That stone is too big for shock wave lithotripsy, but this young lady happened to be a beauty pageant contestant, refused to have any incision on her body whatsoever, even the 1-inch incision it would take to do a percutaneous nephrolithotomy. She said, you need to do this without having any scars. So, I said, okay, it's probably going to take 4 or 5 treatments to do this, and we were just lucky enough that this stone was so soft that this was her result after one treatment: stone gone, normal kidney. So it really does work, and it works well.

Chapter Eleven - LESSONS LEARNED

The lessons that I've learned over the years. You need to very cautious that the patients are not on any kind of anticoagulant, aspirin, Advil, any other of the nonsteroidals including. These patients will bleed if you give them reason to so you need to make sure that their clotting studies are normal and that they're not on any type of anticoagulants. In our business we need to make sure there's no distal obstruction, and in the biliary business I assume the same is true. We do routine follow-up imaging. Just because a patient feels better, we don't assume that everything is better. It is possible to induce PVC's and V-tach with shock waves. If you shock wave right on the heart you definitely will do that and especially the right upper pole of the kidney and the gallbladder is in the neighborhood. We generally administer the shock waves not gated, meaning that with no relationship to the EKG. As soon as we see one PVC, however, we tell the anesthesiologist to stop and we gate the machine. The machine is then gated to the QRS complex so that the shock wave is never delivered on the T-wave and in that way no further arrhythmia will be induced. It slows you down a little bit because with the non-gated you're going at 110 shocks per minute, with the gated shock wave lithotripsy it's whatever the patient's rate is and invariably it'll happen when the patient's on beta blockers and so you're going at about 50 a minute and you're standing there twice and three times as long as you normally would, but you need to do that for the patient's safety.
You do not need to put these patients under general anesthesia. Sedation is sufficient. We've worked this out very well and the patients get Versed and Fentanyl or Alfentanil, and you'll see when we do the patient today that she'll be very comfortable through the whole thing.