ESWL

Question 1

components lithotriptor

Answer 1

energy source
focusing system - concentrate energy on stone
coupling mechanism - gel or water filled cushion transmit energy
imaging

Question 2

types of energy courses

Answer 2

EHL
PE
EM

Question 3

focusing mechnaisms

Answer 3

EM   = cylindrical reflector
EHL = elliptical
PE = hemi spherical

Question 4

how EM ESWL works

Answer 4

coil of wire in close contact with metal membrane
current through coil which repulses metal membrane generates a pressure in water
focused by an aoustic lens

Question 5

PE ESWLworks

Answer 5

PE elements produce electrical discharge under stress or tension
energy transimission via movemet of the source when electricity is passed through it
placed on a concave surface which focuses the waves onto stone

Question 6

electrohydraulic ESWL works

Answer 6

spark between two electrodes under water
results in rapid expansion and collapse gas bubble
subsequent energy transmission
requires aqueous irrigations, not saline or glycine

Question 7

ultrasonic lithotripsy

Answer 7

us waves prodcued by a generator transmitted down hollow probe
resulting in vibration probe tip
contact with stone causes drilling and breakage
not for use in ureter as tip vibration causes heat production

Question 7

ultrasonic lithotripsy

Answer 7

us waves prodcued by a generator transmitted down hollow probe
resulting in vibration probe tip
contact with stone causes drilling and breakage
not for use in ureter as tip vibration causes heat production

Question 8

ballistic lithotripsy

Answer 8

forward momentum of a metal rod placed in contact with stone surface

Question 9

ballistic lithotripsy

Answer 9

forward momentum of a metal rod placed in contact with stone surface

Question 10

swiss lithoclast action

Answer 10

controlled burst of compressed air to move a projectile
tends to move stones forward
mast combines ballistic and suction
often used in pcnl

Question 11

shockwave phases

Answer 11

2 main phases
short positive phase causing erosion and entry and exit points of stone
internal shattering due to compressive effects of wave
second longer negative pressure phase = tensile phase which results in formation of microbubbles which collapse and form microjets which further erode stone

Question 12

EH spark gap

Answer 12

Spark created between 2 electrodes 1mm apart under water
Water around electrode forms gas bubble
Rapid expansion & release of bubble generates shock wave
Focused by a metal reflector (hemi-ellipsoid)

Question 13

PE generator

Answer 13

Spherical dish covered with 3000 small polycrystalline ceramic elements
Each expands rapidly when high voltage applied across them
Rapid expansion generates a shock wave
Spherical dish allows convergence of shock wave. Focus is centre

Question 14

direct 3 and indirect 2 effects eswl on stone

Answer 14

direct
fragmentation
shearing
spallation

indirect
cavitation
dynamic squeezing

Question 15

where different stone fracture mechanisms act

Answer 15

incident SW hits stone
cavitation occurs at site of entry i.e. proximal
squeezing occurs at the equators of the stone
spall is dstial
superfocusing internal caustic

Question 16

spallation

Answer 16

reflected tensile wave at distal surface of stone with maximum tension there, breaking the stone form the inside similar to freezing water in brittle materal

Question 17

cavitation mechanism

Answer 17

negative pressure waves induce a collapsoing cavitation bubble at stones front surface, micro explosive erosion mainly at proximal end of stone

Question 18

super focusing or tear and shear forces

Answer 18

pressure gradients resulting from impedance changes at the front of the stone and the distal surface with pressure inversion,
hammer like action, resulting in crater like fragmentation at both ends of stone

Question 19

dynamic squeezing

Answer 19

pressure gradient between circumferential and long waves resultsin squeezing of stone, nut cracker like action which splits the stone

Question 20

dorneir HM3 EHL

Answer 20

spark plug located a tthe focus of the brass ellipsoidal reflector
energy from spark plug reflected and focused to second focus of the reflector

Question 21

EM lithotriptor two types
acousitc lengs
cynlindrical membrane

Answer 21

Siemens or Dornier
membrane driven by a coil to produce a plane wave focused by acoustic lens

Storz, coil excites a cylindrical membrane which generates a wave that is focused by a parabolic reflector

Question 22

wolf PE 3000

Answer 22

PE elements on a semi spherical backing

Question 23

point of power ramping

Answer 23

renal vasoconstriction

A ramping protocol has also been shown to improve stone
comminution and decrease renal injury
The protective mechanism of ramping is thought to be vasoconstrictive
Initial studies recommended that a 3- to 4-minute pause was key to the protective effects of the ramping protocol
However, as long as the kidney
is allowed to acclimate to the lower power setting for 3 to 4
minutes, the ramping protocol can omit the pause.

Question 24

shocks used

Answer 24

3500 shocks

Question 25

frequency

Answer 25

0.5-1Hz
Oxford 1Hz for total of 2000 shocks starting at 1J and increase slowly to energy level 6, aim energy 6 in kidney and 8 in ureter

Question 26

contraindications ESWL

Answer 26

pregnancy
bleeding
unctonrolled hypertension
infection
distal obstruction
arterial aneurysm in vicinity

relative
hard stones
morbid obesity
abdominal pacemaker

Question 27

consent for lithotripsy

Answer 27

10-50%
need more than one treatment
need other treatment
pain
blood in urine
recurrence stone 

2-10% infection
bruisiing
surgical removal fragments

<1%
perirenal haematoma
severe infection
damage to lung or pancreas