INFN-LNS
DOSIMETRY COMMISSIONING OF THE LNS-INFN
PROTON THERAPY FACILITY
THE DOSIMETRIC CHARACTERISTICS OF NARROW PROTON BEAMS USED IN EYE
THERAPY HAVE BEEN DEFINED BY USING DIFFERENT RADIATION DETECTORS

IONIZATION CHAMBERS (parallel-plate,minithimble chambers)
SILICON DIODES
RADIOCHROMIC AND RADIOGHRAPHIC FILMS
THERMOLUMINESCENCE DETECTORS

1) CENTRAL AXIS DEPTH-DOSE DISTRIBUTIONS
2) LATERAL (TRANSVERSE) PROFILES
3) OUTPUT FACTORS (FSDF)

TO PROVIDE INPUT TO THE TPS AND FOR M.U. CALCULATIONS.

QUALITY CONTROL PROCEDURES

DOSIMETRIC COMMISSIONING OF 60 MeV PROTON BEAMS
PRODUCED AT LNS FOR EYE THERAPY
SHAPED WITH 5 - 30 mm CIRCULAR BRASS COLLIMATORS.
INFN-LNS
PROTON DEPTH-DOSE DISTRIBUTIONS
THE PTW MARKUS PLANE-PARALLEL ION CHAMBER WAS USED IN THE
COMMISSIONING AS THE REFERENCE DETECTOR FOR DEPTH-DOSE
MEASUREMENT IN PROTON BEAMS (ICRU 59, IAEA 398)

THE DESIGN OF THE MARKUS CHAMBER

3
1) Active volume=0.05 cm , 2) Electrode separation=2 mm, 3) Collector diameter=5.4
mm
4) tentrance window=2.3 mg/cm2 5) Exact Location of peff.

PROVIDES DEPTH-DOSE DISTRIBUTIONS
WITH HIGH SPATIAL RESOLUTION AND HIGH PRECISION
•
) PMMA CUP IS PROVIDED TO SEAL THE CHAMBER FOR USE IN WATER
• ) A SPACER IS PROVIDED FOR USE IN A SOLID PHANTOM, WHICH ALSO
SERVES AS A HOLDER FOR A RADIOACTIVE SOURCE FOR STABILITY CHECKS.
INFN-LNS
PTW MARKUS PLANE-PARALLER ION CHAMBER
IN WATER PHANTOM
INFN-LNS
110
PTW- MARKUS ION CHAMBER
BRAGG PEAK
100
90
Relative dose (%)
80
70
60
50
40
30
PLATEAU REGION
20
10
INFN - LNS
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
Depth in water (mm)
CENTRE
MAXIMUM
RANGE
EQUIVALENT
ENERGY
(mm)
(MeV)
PEAK
PLATEAU
RATIO
F.W.H.M.
(mm)
Distal-dose
falloff
d90%-10%
(mm)
CATANA
30.60
60.2
4.68
3.29
0.81
CCO^
31.0
60.4
4.85
3.65
0.80
PSI^
30.0
60.0
4.47
^ taken from BJR Supplement 25 (1996)
1.10
INFN-LNS
THE NEW SCANDITRONIX Si-DIODE IN PROTON BEAMS
(Proton Field waterproof Detector-narrow beam no.DZA192 1001)
INFN-LNS
THE NEW SCANDITRONIX Si-DIODE IN PROTON BEAMS
(Proton Field waterproof Detector-narrow beam no.DZA192 1001)
100
Markus LNS
90
Scanditronix LNS Diode
Relative Dose (%)
80
70
60
50
40
30
20
10
0
0
5
10
15
20
25
30
35
Depth in water (mm)
CYLINDRICAL MINIDIODE SPECIFICATIONS
Detector Material: Hi-pSi, high doped p-type silicon (preirradiated for use in proton beams).
Detector diameter: 0.6 mm (t = 60 m)
Distal-dose
falloff (1)
Distal-dose
falloff (2)
d90%-10%
(mm)
d80%-20%
(mm
3.19
0.71
0.50
31.15
3.07
0.80
0.60
31.06
PEAK
DEPTH
(mm)
PEAKPLATEAU
RATIO
F.W.H.M
(mm)
MARKUS PTW
30.14
4.68
DIODE
SCANDITRON
IX
30.07
4.89
DETECTOR
PRACTICAL
RANGE
(d10%, ICRU 59)
INFN-LNS
MODULATED PROTON DEPTH DOSES FOR EYE THERAPY
110
100
20 mm SOBP
RS 1.8 mm
90
Relative Dose (%)
80
14.5 mm SOBP
RS 14 mm
70
60
50
11 mm SOBP
RS 10 mm
40
30
20
10
0
0
5
10
15
20
25
30
35
Depth in water (mm)
MODULATOR
RANGE
SHIFTER
MODULATION
(SOBP)
DISTAL-DOSE
FALLOFF (1)
DISTAL-DOSE
FALLOFF (2)
d90%-10%
d80%-20%
(mm eye-tissue)
(mm eye tissue)
(mm eye tissue)
MAXIMUM
DOSE
IN SOBP
%
BEAM RANGE
(90% DISTAL)
(mm eye-tissue)
MOD: 000/00
RS: 14 mm
14.5
0.91
0.65
101.6
14.38
MOD: 010/02
RS: 10 mm
10.5
0.90
0.60
104
18.27
MOD: 009/02
RS: 1.8 mm
20.30
0.80
0.55
103.9
27.04
CCO
 17
0.90
0.75
< 102
INFN-LNS
MODULATED PROTON DEPTH DOSES FOR EYE THERAPY
15 MM SOBP vs RANGE SHIFTER
110
100
Relative Dose (%)
90
RS = 10 mm
80
RS = 2 mm
RS = 14 mm
70
60
50
40
30
20
10
0
0
5
10
15
20
Depth in water (mm)
25
30
35
INFN-LNS
BEFORE EACH TREATMENT PERIOD
TREATMENT DEPTH DOSE PROFILES HAVE TO BE VERIFIED.

TO VERIFY RANGE MODULATION AND MAXIMUM RANGE OF THE BEAM

DEPTH-DOSE MEASUREMENT WHEEL (CCO DIODE SCANNER)

WHEEL IS COMPUTER CONTROLLED, AND RELATIVE DOSE MEASURED
AS RATIO BETWEEN WHEEL’S DETECTOR AND REFERENCE DETECTOR
TOLERANCES
1)  [(MEASURED RANGE) / (REQUIRED RANGE)]:   0.2 mm
2)  [(MEASURED MODULATION) / (REQUIRED MODULATION)]: [ -0.1 mm
// +0.9 mm ]
INFN-LNS
LATERAL OFF-AXIS BEAM PROFILES
1) LATERAL PENUMBRA:
H 
2) Field ratio:
d80%-20%
90% fieldsize
50% fieldsize
3) L95%
4) SIMMETRY (AREA RATIO):
5) FLATNESS:
RT % 
Sr 
ABS (a  .b)  200%
ab
Pmax  Pmin
 100%
Pmax  Pmin
110
100
90
80
N.O.D.%
70
60
50
40
30
20
10
-20
1.3 -10
mm
0
0
10
20
X (mm)
MD-55-2 RADIOCHROMIC FILMS WERE USED IN COMMISSIONING
tissue equivalence – dose rate indipendence
Linear dose response – high spatial resolution

ONLY ONE CALIBRATION FILE IS NEEDED TO EVALUATE
FILMS EXPOSED AT DIFFERENT DEPTHS
Energy indipendence
PMMA Phantom
He-Ne Scanning Laser Densitomiter
INFN - LNS
PROFILE MEASUREMENTS
MD - 55 RADIOCHROMIC FILM
120
100
 = 25mm
Relative dose
80
60
40
20
0
-20
-15
-10
-5
0
5
10
15
20
Distance from central axis (m m )
EXPERIMENTAL
SET-UP
(=25 mm)
SOBP
(WIDTH)
H
L95%
(mm)
Sr%
(simmetry)
Rt%
(flatness)
Lateral
penumbra (mm)
d80%-20%
MOD: 000/00
RS: 14 mm
14 mm
zirr.=7 mm
0.92
23
 3%
 3%
1.40
MOD: 010/02
RS: 10 mm
10 mm
zirr.= 12 mm
0.92
23
 2%
 3%
1.30
MOD: 009/02
RS:1.8 mm
20 mm
zirr.= 14 mm
0.93
23
 3%
 3%
1.15
18
zirr.= ½ SOBP
 3%
1.10
CCO
CAL
18
zirr.= ½ SOBP
1.50
INFN-LNS
KODAK XV FILMS AND SCANDITRONIX DIODE WERE USED IN COMMISSIONING

IF CALIBRATION FILES PRODUCED FOR KODAK XV FILMS
AT DEPTH OF SOBP ARE USED FOR TRANSVERSE BEAM MEASUREMENTS

GAF MD55-2 = KODAK XV FILM
MOD 010/02
RS:10 MM
Lateral penumbra
(mm)
H
L95%
(mm)
Sr%
(simmetry)
zirr.=12 mm
d80%-20%
KODAK XV
1.30
0.92
22.8
0.50
MD-55-2
1.27
0.92
22.7
0.90
120
Diodo
MD55
100
X-OMAT V
N.O.D. %
80
60
40
20
0
-25
-20
-15
-10
-5
0
5
X Axis (Water mm)
10
15
20
25
INFN-LNS
BEFORE EACH TREATMENT

PROTON BEAM PROFILES AT ISOCENTRE ARE TO BE CHECKED

IN AIR X-Y DIODE SCANNING COMPUTER CONTROLLED DEVICE

PLANNED TOLERANCES

1)
LATERAL PENUMBRA (d80%-20%)  1.50 mm
2) BEAM SIMMETRY (Sr )  3%
3)
BEAM FLATNESS: Rt%3%
4) FIELD RATIO: H0.90
EXPERIMENTAL AND INTERPOLATED TRASVERSAL DOSE DISTRIBUTIONS (X Axis)
160
Collimator diameter [mm]:
25
Penombra sinistra [mm]:
1.2
Interpolation step [mm]:
0.1
Penombra destra [mm]:
1.3
R90/50:
0.89922
Omogeneità95% [mm]:
21.7
Simmetria [%]:
0.54297
Rt [%]:
2.7259
140
120
Path:
Z:\Misure\Trattamenti Marzo2002\20mar2002\preliminari\profilo11.prf
Dose [a.u.]
100
80
60
40
20
Experimental data
Interpolated data
0
-30
-20
-10
0
Distance from axes [mm]
10
20
30
INFN-LNS
DOSE MONITORING SYSTEM (IN-BEAM DOSE MONITORS)
 THE PROTON DOSE
IS MONITORED BY TWO INDEPENDENT TRANSMISSION
UNSEALED ION CHAMBERS, PLACED IMMEDIATELY UPSTREAM OF THE PROTON
NOZZLE.
 TRANSMISSION CHAMBERS HAVE SEPARATE CABLING, BIAS SUPPLIES (800 V) AND
CURRENT INTEGRATORS AND ARE ARRANGED AS A REDUNDANT COMBINATION TO
TERMINATE THE BEAM.
 TRANSMISSION ION CHAMBERS ARE CALIBRATED DAILY AGAINST A REFERENCE
PARALLEL-PLATE MARKUS ION CHAMBER, LOCATED AT THE ISOCENTRE.
COMMISSIONING TESTS
1) PRECISION
1a) SHORT TERM PRECISION: (CV) OF THE RATIO R OF DOSE MONITOR UNITS TO
DOSIMETER SCALE READING FOR n=5 CONSECUTIVE IRRADIATIONS OF 15 Gy.
 MEASURED CV = 0.1%
1b) LONG TERM PRECISION (WEEKLY STABILITY):
 MEASURED [(cGy/U.M.)WEEK] : 1.5%.
2) LINEARITY
THE RATIO V BETWEEN THE MEASURED PROTON DOSE AND DOSE MONITOR UNITS
SHALL BE WITHIN  1% AT ALL MONITOR SCALE READINGS, i.e. IN THE CLINICAL
RANGE UP TO 15–20 Gy.
 MEASURED RATIO
Vmax
 1.005
Vmin
INFN - LNS
MEASURED DOSE, cGy
( Markus chamber)
MONITOR CHAMBER LINEARITY
DOSE MONITORING SISTEM
TRANSMISSION ION CHAMBER
2400
2200
2000
1800
1600
1400
1200
1000
800
600
400
200
0
R2 = 1
(Dose rate = 51.10 Gy/min.)
0
50000
100000
150000
U.M. SENT
200000
250000
STABILITY OF CALIBRATION (long term )
103
cGy/U.M.
102
DOSE MONITORING SISTEM
TRANSMISSION ION CHAMBER
101
100
99
98
97
0
1
2
3
tim e (days)
4
5
6
INFN-LNS
DOSE RATE MONITORING (BEAM INTENSITY MONITOR)
 THE PROTON BEAM RATE IS MONITORED BY THE VOLTAGE SIGNAL (VSF) PROVIDED BY
THE FIRST SCATTERING FOIL, LOCATED IN VACUUM IMMEDIATELY UPSTREAM OF THE EXIT
WINDOW.
IBEAM (nA) = 0.0412 + 6.0835  VSF
(R2=0.9999)
 (VSF) IS USED BY THE C.S. TO STOP THE BEAM IF THE RATE XCEEDS A PRESET LIMIT.

 NORMAL TREATMENT BEAM CURRENT  4 nA  CLINICAL DOSE RATE =1220 Gy/min.
COLLECTED CHARGE (Markus, nC)
1.05
1.04
U.M. =K
1.03
1.02
Alarm current
1.01
1
Zmarkus = 1 mm
Full energy
beam
0.99
Normal
current
0.98
0.97
0
1
2
3
4
5
6
PROTON BEAM CURRENT (nA)
7
8
9
10
INFN-LNS
ABSOLUTE DOSIMETRY (BEAM CALIBRATION, cGy/U.M.)
FOR REFERENCE DOSIMETRY, AT LNS, A PLANE-PARALLEL MARKUS ION CHAMBER IS
USED IN A WATER PHANTOM, BY EXTENDING TO PROTON BEAMS THE FORMALISM OF THE
IAEA 381 CODE OF PRACTICE ON THE USE OF PLANE-PARALLEL ION CHAMBERS IN HIGH
ENERGY ELECTRON DOSIMETRY.


DwQ ( Peff )  M Q  N Dpp,air,Q0  Wair Q Wair Q 0  S w,air Q  pQ
MQ  M ( C )  kT ,P  k pol  ks
(sw,air)q
(nC)
( TAB. 7.1 ICRU 59)
N
pp
D , air,Q0
M

ref
cGy
ref
 N Dref,air  Pcav
 Pcelref 
cGy/nC
M pp
(Wair/e)cp = 1.031 (ICRU 59)
pQ = 1.00 (ICRU 59, IAEA TRS-398, MED.PHYS. 1995 :22)
FOR DOSE CALIBRATIONS OF INDIVIDUAL PATIENTS, THE CALIBRATION IS MADE IN A
UNIFORM DOSE REGION AT THE MIDDLE OF SOBP, AT ISOCENTRE, WITH THE 25 mm
DIAMETER REFERENCE COLLIMATOR ON BEAM DELIVERY NOZZLE.
FOR DAILY DOSE CHECKS, A PMMA PHANTOM BLOCK IS USED:
z PMMA  zwater  0.87
A RADIOACTIVE CHECK DEVICE (90Sr) IS USED FOR OPERATIONAL AND CONSTANCY
CHECKS OF DOSIMETRY SYSTEM (1%, NCRP).
INFN-LNS
AN EXRADIN T1 THIMBLE ION CHAMBER [A-150 TE, 0.05 cm3, NK(60Co)]
CAN BE USED AT LNS IN THE WATER PHANTOM, ACCORDING TO ICRU 59

Dw , p Gy  M Q nC   kT ,P  k pol  ks  0.6311 Gy   0.9534  1.031  S /  water ,air 
 nC 

BECAUSE OF THE Cavity length AND Outer diameter of the chamber,
USE IS LIMITED TO (  )  15 mm AND (SOBP WIDTH)  12 mm.
WORK IN PROGRESS

NOW AVAILABLE BY PTW ND,w,60Co FOR T1 EXRADIN AND MARKUS LNS CHAMBERS

ADOPTION OF IAEA TRS-398 CODE OF PRACTICE

Dw,Q = MQ ND,w,Q0 kQ,Q0

ESTIMATED UNCERTAINTY OF Dw,Q UNDER REFERENCE CONDITIONS (1 S.D.)
ICRU 59
(Nk=1%)
IAEA TRS-398 (ND,w,Q0 =1%)
EXRADIN T1
2.6%
2.1%
PTW MARKUS
3.1%
2.5%
INFN-LNS
PROTON DOSIMETRY INTERCOMPARISON (ECHED, ICRU 59)

BEFORE STARTING LNS PROTON THERAPY FACILITY
) INTERCOMPARISON (1) AT CCO (PHYSICA MEDICA, VOL.XV, N.3)

LNS (PTW MARKUS, T1-EXRADIN)  CCO (A-150 FW-IC18, REFERENCE DOSE)

(Dw) [(PTW MARKUS) / (FW-IC18)]: 1%
(Dw) [(T1-exradin) / (FW-IC18)]: 1.4%
) INTERCOMPARISON (2) AT PSI (PHYSICA MEDICA VOL.XVII, S.3, PTCOG XXX 1999)

1) CCO (FW-IC18, MARKUS)
2) LNS (MARKUS, EXRADIN-T1, PTW PMMA FARMER)
3) PSI (PTW GRAPHITE FARMER, MARKUS)
4) TERA ( MARKUS, EXRADIN-T1)

% = 1.2%

max (%) = 3.5%
INFN-LNS
DOSIMETRY INTERCOMPARISON AT PSI
(FULLY MODULATED BEAM)
6
Deviation from the mean (%)
4
2
0
-2
Standard deviation of the mean = 1.13%
Difference between maximum and minimum dose =
3.3%
-4
-6
-8
MARKUS EXRADIN FARMER MARKUS FWT 683
LNS
T1 LNS
LNS
CCO
CCO
FWT 725 MARKUS EXRADIN MARKUS FARMER
CCO
TERA
T1 TERA
PSI
PSI
INFN-LNS
OUTPUT FACTORS (FSDF)
) AT THE INITIAL CALIBRATION OF CYCLOTRON THE OUTPUT DOSE RATE HAS BEEN
MEASURED FOR ALL COLLIMATORS AREA ENCOUNTERD IN THE CLINICAL PRACTICE.

) TO EVALUATE IF THERE ARE SIGNIFICANT DROPS OF DOSE PER MONITOR UNIT
WHEN COLLIMATOR DIAMETER DECREASES TO A FEW MILLIMETERS.

) THE MOST RELIABLE RELATIVE OUTPUT VALUES
ARE PROVIDED FROM
RADIOCHROMIC DETECTORS, ESPECIALLY FOR NARROWEST BEAMS (VATNITSKY).

NO SIGNIFICANT DECREASE OF BEAM OUTPUT (cGy/U.M.)
FOR COLLIMATOR DIAMETER UP TO 5 mm
110
100
90
Relative output
80
GAF
Markus
Diode1
Diode2
TLD2
TLD1
70
60
50
40
30
MODULATED BEAM
Z = 21 mm WED
PMMA PHANTOM
20
10
0
0
2
4
6
8
10
12
14
16
Collimator diameter (mm)
18
20
22
24
26
28
INFN-LNS
OUTPUT FACTORS (FSDF)
) FROM EXPERIMENTAL RESULTS WE CAN STATE THE LOWER BOUND OF COLLIMATOR
DIAMETER FOR WHICH FRELATIVE OUTPUT IS MEASURED ACCURATELY WITH EACH
DETECTOR
110
100
90
Relative output
80
GAF
Markus
Diode1
Diode2
TLD2
TLD1
70
60
50
40
30
MODULATED BEAM
Z = 21 mm WED
PMMA PHANTOM
20
10
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
Collimator diameter (mm)

1) MARKUS CHAMBER CAN BE USED IN PROTON BEAMS WITH 12 mm
2) TLDs AND SCANDITRONIX DIODE CAN BE USED UP TO =8 mm
IN CLINICAL PRACTICE AT LNS

GAF-DETECTOR IS USED FOR EVALUATION OF OUTPUT FACTOR

FOR SHAPED NARROWEST BEAMS
28
INFN-LNS
PATIENT DOSES (STRAY RADIATION)
(PERSONAL MONITORING, TWO PATIENTS TESTED)
A) TWO PERSONAL BADGE-DOSIMETERS WERE PLACED ON THE
CHEST OF PATIENTS DURING THE WHOLE PROTON TREATMENT.
1) ENEA FILM BADGE PERSONAL DOSIMETER (, , x)   0.05 mSv
2) NRPB PADC NEUTRON PERSONAL DOSEMETER
PATIENTS COMPLETING TREATMENT 

0.20 mSv
INDUCED DOSE RATE

 15 Sv/h
 (10’)
 1.5 Sv/h