Post on 31-Aug-2018
QUALITY ASSURANCE PROCEDURE FOR
SRS AND SRT TREATMENTSMEIJERS A., PLAUDE S., UTEHINA O., POPOVS S.
RIGA EAST UNIVERSITY HOSPITAL
Thursday, October 13, 11
SRS / SRT TREATMENTS
INTRODUCED IN 2009 AT RIGA EAST UNIVERSITY HOSPITAL.
EQUIPMENT:
NOVALIS TX (VARIAN), EXACTRAC (BRAINLAB)
VARIOUS LOCALIZATIONS:
HEAD, LIVER ETC.
Thursday, October 13, 11
CHALLENGES
FRACTIONATED TREATMENT
MISTREATMENT OF A SINGLE FRACTION DOES NOT HAVE SIGNIFICANT IMPACT ON DELIVERED DOSE
Thursday, October 13, 11
CHALLENGES
RADIO-SURGERY
MISTREATMENT IN A SINGLE FRACTION HAS SIGNIFICANT IMPACT ON ALL THE TREATMENT
Thursday, October 13, 11
TREATMENT ACCURACY
SRSSRT
FRACTIONATEDTHERAPY
SRS / SRT REQUIRES HIGHER QUALITY IN TERMS OF TREATMENT DELIVERY
Thursday, October 13, 11
CAUSES OF INACCURACY
PATIENT POSITIONING
MISCONFIGURATION OF TPS
SOFTWARE BUGS
MECHANICAL FAULTS OF TREATMENT DELIVERY SYSTEM
MIS-CALIBRATION OF LINAC
IONIZATION CHAMBERS
MECHANICAL INDICATORS
Thursday, October 13, 11
PATIENT-RELATED QA FOR SRS/SRT
DOSE PLANE MEASUREMENT
ABSOLUTE POINT-DOSE MEASUREMENT
WINSTON-LUTZ TEST
Thursday, October 13, 11
DOSE PLANE MEASUREMENT
1. CALCULATION OF TREATMENT PLAN ON QA PHANTOM
2. MEASUREMENT WITH RADIOCHROMIC FILM
3. COMPARISON OF MEASURED DOSE VS CALCULATED
Thursday, October 13, 11
FILM DOSIMETRY
GAFCHROMIC EBT 2 (ISP) FILMS
DOSE RANGE UP TO 40 GY
CALIBRATION: TEST FILM WITH KNOWN DOSE
METHOD: COMPOSITE ANALYSIS
0
7.5
15.0
22.5
30.0
1 10 100 1000
Dose
, Gy
Tone Index
Thursday, October 13, 11
FILM DOSIMETRY
ANALYSIS:
GAMMA INDEX - 1MM / 5% / SUPPRESS < 5%
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ACCEPTABLE:GAMMA PASS > 90%
UNACCEPTABLE:GAMMA PASS <85%
MEAN 96.4 ± 2.6 %
Thursday, October 13, 11
PATIENT-RELATED QA FOR SRS/SRT
DOSE PLANE MEASUREMENT
ABSOLUTE POINT-DOSE MEASUREMENT
WINSTON-LUTZ TEST
Thursday, October 13, 11
POINT DOSE MEASUREMENT
1. CALCULATION OF TREATMENT PLAN ON QA PHANTOM
2. MEASUREMENT WITH IONIZATION CHAMBER
3. COMPARISON OF MEASURED DOSE VS CALCULATED
Thursday, October 13, 11
POINT DOSE MEASUREMENT
HAND-MADE PHANTOMPINPOINT CHAMBER (PTW)
0.016 CM3
ANALYSIS:LOCAL DIFFERENCE IN %
ACCEPTABLE < 3%UNACCEPTABLE > 5%
MEAN -1.2 ± 1.6 %
Thursday, October 13, 11
PATIENT-RELATED QA FOR SRS/SRT
DOSE PLANE MEASUREMENT
ABSOLUTE POINT-DOSE MEASUREMENT
WINSTON-LUTZ TEST
Thursday, October 13, 11
WINSTON-LUTZ TEST
1. ALIGN POINTER TO ISOCENTRE
2. TAKE PORTAL IMAGES FROM NECESSARY ANGLES
3. DETERMINE CENTRE OF FIELD
4. DETERMINE CENTRE OF POINTER SPHERE
5. DETERMINE THE DISTANCE BETWEEN CENTERS
Thursday, October 13, 11
WINSTON-LUTZ TEST
ACCEPTABLE < 1MMUNACCEPTABLE > 1MM
0.50
0.75
1.00
Sphe
re s
ize, m
m
Thursday, October 13, 11
PATIENT-RELATED QA FOR SRS/SRT
DOSE PLANE MEASUREMENT
ABSOLUTE POINT-DOSE MEASUREMENT
WINSTON-LUTZ TEST
Thursday, October 13, 11
CONCLUSIONS
THE DEVELOPED PATIENT RELATED QA PROCEDURE IS SUFFICIENT TO VERIFY ACCURACY OF TREATMENT PLANNING SYSTEM CALCULATIONS, PRECISION OF TREATMENT DELIVERY MECHANICS AND SYSTEM IN GENERAL.
ADDITIONAL MACHINE RELATED VERIFICATIONS ARE NECESSARY.
QA PROGRAM, BASED ON DESCRIBED PRINCIPLES, HAS BEEN IMPLEMENTED IN RIGA EAST UNIVERSITY HOSPITAL.
Thursday, October 13, 11
THANK YOU!
ARTURS.MEIJERS@ME.COM
Thursday, October 13, 11