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Radioactive Stents. Production and History. Comparison of IVUS data Average data of 157 radioactive und 140 non radioactive stents. Stent. Stent. remodeling. neointima. Plaque [mm 2 ]. „Edge Effekt“. In early days. 1991Fischell: US-Patent: Radioactive Stent - PowerPoint PPT Presentation
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Klaus Schloesser, Forschungszentrum Karlsruhe, Technik und Umwelt /HZY
Radioactive Stents
Production and History
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Stent Stent
remodeling
neointima
Plaque [mm2]
Comparison of IVUS data Average data of 157 radioactive und 140 non radioactive stents
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
„Edge Effekt“
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
In early days
• 1991 Fischell: US-Patent: Radioactive Stent
• 1992 Hehrlein, Heidelbergwanted radioactive Stents -> animal trials
• 1994 Liermann, Frankfurt
Treatment of peripheral arteries (legs) 192Ir – Afterloader
• 1995 Connado, Venezuela192Ir – Afterloader (manuel)
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Radioactive Stent in Rabbits
• 55Co... left
• 32Pright
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Methods of Activation
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Radioisotope• 1 day < halflife < 3 Weeks
• Suitable radiation for Brachytherapy with stents
Range about 2-5 mm -radiation of low energy - radiation of high energy
– no -radiation(does not reach target volume, too much damage in the vicinity)
– No deeply penetration -radiation (health physics problems)
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Phosphorous -32
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Heavy Ion Implantation
Depth distribution of implanted P-32
0%
5%
10%
15%
20%
25%
0 20 40 60 80 100 120
Depth [nm]
conc
entr
atio
n [a
rbitr
ary
units
]
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Ion Source
Acceleration
Mass separation
Target
M=31 M=32
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
ECRIS – magnetic bottle
mc
eBmr
m
PLTTT cyccyclincyc
;;
22
22
)sin(0 tEeE x
x
yz
2.45GHz)( 87,5mTGHz][0357,0]T[ ffB
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
ECRIS-radial Confinement by Hexapole
N
S
S
NS
N
N
S N
S
S
Nx
yz
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Precursor of Plasma is Gas• Red Phosphorous sublimates at about 440°C (ugh !)
gaseous compound: PH3 (Phosphine)
• Phosphine is very poisonous– MAK = 0,1 ml/m³ = 1/10 threshold for smelling (Garlik)
• Radio toxicity – Inhalation von 1 m³ Air (32P/31P) = 1/1000 results in effective
dose > 5 Sv which corresponds to LD50 (ugh , really!)
– So, let’s make only that much Phosphine at a time, so that the ion source is just filled. (0,5l at 10-4mbar)
• H• + P PH• or. H+ + P PH+ etc. up to PH3
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
ECRIS – with two stage extraction and plasma chamber made of glass
100
M
30 kV
60 kV
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Overview of ion implanter
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Mass Spectrum
16O231PH
28SID214N2D212C16O
D232P
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Ion source
acceleration
separation
target
M=31 M=32
Irradiation chamber
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Irradiation
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Irradiation platform
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Discharge behaviour
ca. 3 h
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Performance of the ion source for 32PEfficiency Ca. 20% in main beam
Time for discharge 3 hours, almost no mixture of fresh with old Phosphorous
Emittance (beam spot size)
beam < 2 mm at a vertical deflection > 20 mm
Maintenances After 1 year Extraction was exchanged due to HV-problems
Stability Unattended operation over night is no problem
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Quality control: Measurement of activity distribution
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Special activity distributions
Lot # M.5023-000502R SN-1, pass,
-2000
-1500
-1000
-500
0
500
1000
1500
2000
0 20 40 60 80 100 120 140
channel w idth = .301 mm
Coun
ts/c
hann
el
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
Quality control: encapsulation of activity
• Test method: washing of stents in isotonic sodiumchlorid (0,9% NaCl) in an ultrasonic bath
cumulative washout
0
0,2
0,4
0,6
0,8
1
1,2
1,4
0 200 400
time [minutes]
w [
% o
f to
tal a
ctiv
ity]
15 min used in routine quality control
washout constant after two hours < 0.1%/ hour
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
How much activity (how many ions) fits on a stent?
Wash off versus implanted ion dose for perpendicular and oblique incidence of beam
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
2
1,E+13 1,E+14 1,E+15 1,E+16 1,E+17 1,E+18
ions / sqcm
wash
out
[% o
f tot
al a
ctiv
ity]
90°
30°
> 30°
< 30°
Klaus Schloesser, Forschungszentrum Karlsruhe / HZY
If „drug – eluting“ works, prevention of restenosis with
radioactive stents is not the first choice
• perspectives– e.g. oncology
dose application within 2mm distancebut restricted to target volume