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ESWL Revolution

History of the Shockwave Lithotripters

Ever since the first human application was performed on a Dornier prototype lithotripter (Human Model 1 = HM1) in 1980 and the first definitive kidney lithotripter (HM2) was installed in Munich in 1982, the extracorporeal shock wave lithotripsy has been rapidly propagated throughout the world revolutionizing urinary stone treatment. The Dornier HM3, the archetype of a first generation lithotripter, featured a large water bath for optimal shock wave coupling, fluoroscopic imaging, an ellipsoid reflector with a small aperture and a shockwave generator, necessitating general or spinal anesthesia.

More lithotripter manufacturers started their research and development activities after the introduction of HM3. About 20 or so lithotripters were developed between1985 and 1989 using either X-ray or ultrasound (but not both) for stone localization. The integration of a water-cushion-coupled shock wave generator in an X-ray table allowed multifunctional use of the stone machine and is considered as the key feature of a second generation lithotripter.

After 1990, most of the leading lithotripter companies developed new machines or modified their systems to comply with the following specifications (as the basic requirements for a third generation lithotripter):

  1. A combined localization system of ultrasound and fluoroscopy (only manual localization is required). 
  2. A wide range of energy output of the shock wave source (i.e. peak pressure) aiming at an efficacy.
  3. A larger aperture of the focusing system enabling treatment under minimal anesthesia.
  4. Integration of the shock wave source, the fluoroscopic unit and the ultrasound device.

Due to technology advancement in the past decade, several leading lithotripter developers have devoted additional development efforts in patient safety and treatment efficiency than what’s required for the third generation machine. Lite-Med Inc., as one of them, had come up with what may be called a “fourth generation lithotripter”.

Potential Damage to the Human Body from ESWL

  1. ESWL requires anesthesia
    Higher energy is used by ESWL in order to have shockwaves effectively break stones. The patient moves due to pain during the treatment which results in not correctly hitting the stones. Therefore, anesthesia is normally necessary for the ESWL procedure.
  2. Overdose of X-ray radiation exposure
    Traditional lithotripters only utilize X-ray to locate the stones. The X-ray is first turned on for stone localization before the treatment and then turned off as soon as the shockwave treatment starts. After applying about 300 shockwaves to the patient the X-ray is turned on again to locate the stone and adjust the target position in order to make sure the shockwave focus is correctly positioned at the stone during the treatment. About 3000 or more shockwaves are normally required in the ESWL procedure and, therefore, at least 10 X-ray exposures are given to the patient during the treatment. This may result in overdose of radiation to the patient and create other side-effects later.
  3. Damage to tissue adjacent to the stones
    The shockwave focus of traditional lithotripters is fixed at the target position after the initial localization and between adjacent re-localizations. The stones move following patient’s breath movements and, therefore, relocate away from the shockwave target position after each (re-)localization. In this condition, the target hit-rate reduces to one half or less from the original 100%. In other words, only  one half of the shockwave energy is transferred to the stones and the rest is absorbed by the neighboring tissues, Thus more damage to the kidney and other surrounding organs as shown in the next chart.

     

kidney1                     kidney2
Temporary Injuries
  • Local Bruise Under Skin
  • Pain Around Target Area
  • Hematuria
  • Perirenal Hematoma
  • Surrounding Organ Damages
Permanent Pathologic Changes
  • Fibrosis In the Damaged Area
  • Hypertension
  • Reduced Renal Function

 

New Technological Advancement of the 4th Generation ESWL

Lite-Med has developed a 4th generation ESWL machine with following advanced techniques to overcome drawbacks of traditional lithotripters:

  1. High Performance Shockwave Generation System
    With improved shockwave energy density the Lite-Med lithotripter can achieve high stone breaking efficiency at lower shockwave pressure. A kidney stone patient going through Lite-Med’s ESWL procedure can normally get effective shockwave treatment without any anesthesia or pain killers.

  2. Dual X-ray and Ultrasound Auto-Localization System
    With Lite-Med’s lithotripter, we only need to expose the stone patient with X-ray once at 0 degree and again at 30 degrees at the beginning of ESWL treatment. The computer will position the patient and the stone at the shockwave focus automatically. With the X-ray turned off and the ultrasound detector moved in to monitor stone movements continuously, the computer controlled lithotripter keeps on making corrections to the stone position according to ultrasound images of the stone without using X-ray. Thus, the entire ESWL procedure only requires X-ray localization to be done once and, therefore, very little radiation dose is given to the stone patient.
    1
  3. Ultrasound Stone Image Tracking and Locking System
    Utilizing the non-ionization characteristics of the ultrasound we can monitor  the stone fragmentation in progress during the entire ESWL procedure. Based on a method similar to the principle of target missile tracking, we can track stone movements during the treatment process. By guiding the shockwaves to the right stone location at the right time we can easily increase the stone hit-rate to 85%.
Comparison between Lite-Med’s Localization with Tracking and without Tracking
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No Tracking:
Stone movement due to breathing may result in damage to kidney & adjacent organs during shockwave treatment ( Perirenal Hematoma, Severe Hematuria)

With Tracking:
Shockwave focus moves with the movement of the stone which results in high hit-rate and better fragmentation efficiency  (45%→86%)

During the ESWL treatment the stone normally moves in and out of a certain target window following the patient’s breath rhythm. Stone image locking is based on the rule of firing – that is to fire the shockwaves when the stone moves inside the target window and to stop firing the shockwaves when the stone moves outside the target window. With stone image locking, the stone hit-rate is, therefore, near 100%.

Advantages of Lite-Med Lithotripter’s Innovative Technologies

  • No anesthesia or analgesic is needed due to Lite-Med Lithotripter’s high efficiency shockwave creation. This means less cost in drugs and related material and less risk to the patient due to drug’s side effects.
  • Outpatient surgery can be carried out, without hospitalization.
  • Lite-Med’s patented stone tracking and locking systems produce better stone fragmentation and less tissue damage.
  • Ultrasound localization results in very low radiation dose and reduces the treatment risks through real-time monitoring.

Awards and Certifications

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