Transcript 放射治療設備品質保證原理 Comprehensive QA for radiation onlology

放射治療設備品質保證原理
Comprehensive QA for radiation onlology
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Class date/time: Thursdays, 8:20-10:05 AM,
2002/2/28~6/27
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References:
Quality Assurance in Radiotherapy Physics.
 Comprehensive QA for radiation oncology:
Report of AAPM Radiation Therapy Committee
Task Group 40. Med. Phys. 21 (4), April 1994.
Grading:
 Roll call and reports: 50%, Examinations: 50%
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PREFACE
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QA activities cover a very broad range, and the work of
medical physicists in this regard extends into a number of
areas in which the actions of radiation oncologists, radiation
therapist, dosimetrists, accelerator engineers, and medical
physicists are important.
If quality of care is to be improved, enlightened leadership
by hospital management and clinical leaders is required.
Within radiation oncology itself, coordination is critical
among radiation oncology physicists, dosimetrists, accelerator
engineers, radiation oncologists, radiation therapists, and
administrators. The various groups are brought into
coordinated efforts through well-documented QA
procedures administrated by a multidisciplinary QA
committee.
CONTENTS
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Information for radiation oncology administrators
Code of practice
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Comprehensive QA program
QA of external beam radiation therapy equipment
Treatment planning computer system
External beam treatment planning
Brachytherapy
QA of clinical aspects
Information for radiation oncology
administrators
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In treating patients with radiation, the radiation
oncologist prescribes a treatment regimen ( including the
radiation dose ) whose goal is to cure or control the
disease while minimizing complications to normal tissue.
The response of tumors and normal tissue t radiation is
highly variable.
The radiation dose must be delivered accurately and
consistently.
Radiation therapy process is a complex interweaving of a
number of related tasks.
Information for radiation oncology
administrators
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Radiation therapy process :
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Initial consultation
Determination of patient-specific parameters. ( Acquired from
a number of diagnostic imaging sources )
Treatment planning ( determine the size, extent, and location
of the tumor in relation to the normal organs. Distribution of
radiation dose to patient )
Simulating the planned treatment ( Simulator )
To treat the patient as planned
Verifying the correct delivery of treatment ( portal and
verification radiographs, in vivo dosimetry, and record-andverify systems.
Information for radiation oncology
administrators
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ICRU has recommended that the dose be delivered to within 5%
of the prescribed dose. Each step of radiation therapy process
must be performed with an accuracy much better than 5%.
To meet such standards required the availability of the necessary
facilities and equipment including treatment and imaging units,
radiation measuring devices, computer planning systems and the
appropriate staffing levels of qualified radiation oncologists,
radiation oncology physicists, dosimetrists, and radiation
therapists.
Furthermore, the complexity of treatment modalities is increasing.
Information for radiation oncology
administrators
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For Example :
 Linacs contain computer control system.
 High and low dose-rate remote afterloaders have sophisticated
control systems.
 Treatment planning systems become larger and more complex.
Several sophisticated options have become standard on
commercial and locally developed systems. ( 3-D BEV
planning, DRR, 3-D dose computation and display, DVH …)
 The commissioning and quality assurance of such complex
systems requires increasing personnel training and time.
Increasing expectations on the quality of treatment which lead to
greater and more complex.
Information for radiation oncology
administrators
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These expectations have arisen from a growing appreciation of
the importance of QA, and from the regulations of national, state,
and local authorities and accreditation bodies.
QA processes and procedures emanate from a QA committee.
QA committee should include nurses, the department
administrator, and
 Radiation oncologist may be responsible for
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Consultation
Dose prescription
On-treatment supervision
Treatment summary reports
Information for radiation oncology
administrators
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Radiation oncology physicist is responsible for
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Calibration of the therapy equipment.
Directs the determination of radiation dose distributions in
patients undergoing treatment.
Weekly review of the dose delivered to the patient.
Certifies that the treatment machine is performing according to
specifications after it is installed.
Generate the beam data.
Outlines written QA procedures, tolerances, and frequency of
the tests.
Understands and appropriately responses to machine
malfunctions and related safety issues.
Information for radiation oncology
administrators
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Radiation therapist
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Be responsible for Accurately delivering a planned course of
radiation therapy as prescribed by a radiation oncologist.
Be expected to recognized any change in the patient’s condition
and determine when treatment should be withheld until a
physician is consulted.
Be able to detect any equipment deviations or malfunctions,
understand the safe operating limit of the equipment.
Be able to judge when, due to equipment problems , to withhold
or terminate treatment until the problem has been resolved.
Information for radiation oncology
administrators
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Medical radiation dosimetrist
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Be responsible for accurate patient data acquisition
Radiation treatment design. ( In consultation with the physicist
and oncologist )
Manual/computer-assisted calculations of radiation dose
distribution.
Assist with machine calibrations and ongoing QA under the
supervision of the physicist.
Information for radiation oncology
administrators
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It is also important to provide the appropriate dosimetry
instrumentation for commissioning and QA of these devices.
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Daily QA device
Ion chamber
Electrometer/dosimeter
Barometer
Thermometer
Level
Ruler
Film scanner/ densitometer
Information for radiation oncology
administrators
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Water phantom scanning system
Solid phantom
Survey meter
A comprehensive QA program should not focus just on the
analysis of a narrow set of treatment variables, but rather
should attempt to understand the cumulative effects of
uncertainties.
Medical linear accelerator
QA of external beam radiation therapy equipment
A. General
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QA of radiation therapy equipment is primarily an
ongoing evaluation of functional performance
characteristics.
The function performance of radiotherapy equipment
can change suddenly due to
 Electronic malfunction
 Component failure
 Mechanical breakdown
Or can change slowly due to deterioration and aging of
the component.
QA of external beam radiation therapy equipment
A. General
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Therefore, two essential requirement emerge:
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QA measurements should be performed periodically on all
therapy equipments, including the dosimetry and other QA
measurement devices.
There should be regular preventive maintenance monitoring
and correction of the performance of therapy machines and
measurement equipment.
The overall responsibility for a machine QA program be
assigned to one individual : the radiation oncology
physicist.
QA of external beam radiation therapy equipment
A. General
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The QA program should be based on a thorough
investigation for baseline standards at the time of the
acceptance an commissioning of the equipment for
clinical use.
Acceptance procedures should be followed to verify the
manufacture’s specifications and to establish baseline
performance values for new or refurbished equipment,
or for equipment following major repair.
Once a baseline standard has be established, a protocol
for periodic QA tests should be developed.
QA of external beam radiation therapy equipment
A. General
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Tests for a typical QA program.
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Frequency of tests ( daily, weekly, and so on )
Tolerance values.
Ensuring that the equipment is suitable for high quality
and safe radiation treatment.
Machine QA test procedures should be able to
distinguish parameter changes smaller than tolerance or
action levels.
Within these limits, the tests should also be developed
to minimize the test time.
QA of external beam radiation therapy equipment
B. Test Frequency
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Daily tests include those could seriously affect patient
positioning and therefore the registration of the
radiation field and target volume (lasers, ODI ); patient
dose ( output constancy ) and safety ( door interlock and
audiovisual contact )
Monthly include those either have a smaller impact on
the patient ( e.g., treatment couch indicators ) or have
lower likelihood of changing over a month ( e.g., light
and radiation field or beam flatness ).
QA of external beam radiation therapy equipment
B. Test Frequency
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AAPM recommend adherence to the program outlined
in the tables unless there is demonstrable reason to
modify them.
At this stage there is no accepted method of
systematically defining the type and frequency of QA
tests that should be performed.
The best guidance that can be given at present is that the
QA program should be flexible enough to take into
account quality, costs, equipment condition, and
institutional needs.
QA of external beam radiation therapy equipment
C. Guideline for Tolerance Values
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The tolerance values are intended to make it possible to
achieve an overall dosimetric uncertainty of ±5% and an
overall spatial uncertainty of ±5mm.
The tolerances listed in the tables mean that if a
parameter either exceeds the tabulated value ( e.g., the
measured isocenter under gantry rotation exceeds 2 mm
diameter ) or that the change in the parameter exceeds
the tabulated value ( e.g., the output changes by more
than 2% ), then an action is required.
QA of external beam radiation therapy equipment
C. Guideline for Tolerance Values
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It is important to realize that the tolerance levels
presented in this document reflects standards of practice
which have evolved in the practice of radiation
oncology physics over the past decades, or even longer.
These standards may, and probably will to be modified
as newer techniques are introduced.
QA of external beam radiation therapy equipment
Daily QA of medical accelerator
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Dosimetry
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3%
3%
Mechanical
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X-ray output constancy
Electron output constancy
Localizing lasers
Distance indicator ( ODI )
2 mm
2 mm
Safety
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Door interlock
Audiovisual monitor
Functional
Functional
QA of external beam radiation therapy equipment
Monthly QA of medical accelerator
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Dosimetry
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X-ray output constancy
2%
Electron output constancy
2%
X-ray central axis dosimetry parameter ( TPR) constancy
2%
Electron central axis dosimetry parameter ( PDD) constancy
2mm
X-ray beam flatness constancy
2%
Electron beam flatness constancy
3%
X-ray and electron symmetry
3%
QA of external beam radiation therapy equipment
Monthly QA of medical accelerator
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The beam uniformity and dose stability should be check
at different angular positions of the gantry, since recent
reports indicate that accelerator beam characteristics can
vary with gantry position.
Beam scanners which mount directly on the treatment
head of the machine are useful in measuring beam
output and symmetry as a function of gantry angle.
Instruments for daily “spot checks” use arrays of
ionization chambers or solid state detectors which can
be perform multiple tests with one radiation exposure.
QA of external beam radiation therapy equipment
Monthly QA of medical accelerator
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Monthly output checks are performed by a physicist
with an ionometric dosimetry system that is acceptable
for calibration by an Accredited Dosimetry Calibration
Laboratory.
For daily output checks, clinical action level = 5%. If
exceeded, no further Tx. should be given. If the output
difference is within 3% and 5%, then Tx. may continue
and the radiation oncology physicist is notified.
It is essential that the physicist review these daily
measurements and keep the output under surveillance.
QA of external beam radiation therapy equipment
Monthly QA of medical accelerator
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Field symmetry and flatness may be affected by both
mechanical and electronic parameters. Small changes in
beam energy, beam alignment, bending magnet function,
target position, flattening filter selection and position, as
well as other machine parameters, may result in
unacceptable beam profile.
Field symmetry and flatness are both characteristics of a
beam profile measures either in air or at some given
depth in water.
QA of external beam radiation therapy equipment
Monthly QA of medical accelerator
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Flatness
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Defined as the max. difference from the dose on the central
axis over 80% of the field dimension ( length or width ).
80% of Field Width
Ymax
100%
Y0
50%
Field Width
Ymin
( Ymax-Y0 ) / Y0  100 %
Flatness = ±
( Ymin-Y0 ) / Y0  100 %
QA of external beam radiation therapy equipment
Monthly QA of medical accelerator
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Symmetry
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Defined as the difference in dose rate between any two
symmetric points within 80% of the field size ( length or
width ).
80% of Field Width
Y1
100%
Y0
50%
Field Width
Y2
Symmetry = ( Y1-Y2 ) / Y0  100 %
QA of external beam radiation therapy equipment
Monthly QA of medical accelerator
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Safety Interlocks
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Emergency off switches
Wedge, Electron cone interlocks
Functional
Functional
Mechanical Checks
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Light/Radiation field coincidence
Gantry/Collimator angle indicator
Wedge position
Tray position
Applicator position
2mm or 1% on a side
1 deg
2 mm ( or 2% change in
transmission factor )
2 mm
2 mm
Light/Radiation field coincidence
Light and radiation
fields coincident
Light and radiation
fields not coincident
QA of external beam radiation therapy equipment
Monthly QA of medical accelerator
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Mechanical Checks
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Field size indicators
Cross-hair centering
Treatment couch position indicators
Latching of Wedges, Blocking tray
Jaw symmetry
Field light intensity
2mm
2 mm diameter
2 mm / 1 deg
Functional
2 mm
Function
QA of external beam radiation therapy equipment
Monthly QA of medical accelerator
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Cross-hair centering
A
B
Mid-point of line AB is a point
on the collimator axis of
rotation. A and B correspond to
collimator angular positions
180 degrees apart.
QA of external beam radiation therapy equipment
Monthly QA of medical accelerator
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Jaw symmetry
QA of external beam radiation therapy equipment
Annual QA of medical accelerator
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Dosimetry
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X-ray/electron output calibration constancy
Field size dependence of x-ray output constancy
Output factor constancy for electron applicators
Central axis parameter constancy ( PDD, TPR)
Off-axis factor constancy
Transmission factor constancy for all Tx.accessories
Wedge transmission factor constancy
Monitor chamber linearity
X-ray output constancy vs gantry angle
2%
2%
2%
2%
2%
2%
2%
1%
2%
QA of external beam radiation therapy equipment
Annual QA of medical accelerator
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Dosimetry
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Safety Interlock
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Electron output constancy vs gantry angle
2%
Off-axis factor constancy vs gantry angle
2%
Arc mode
Functional
Follow manufacturers test procedures
Functional
Mechanical Checks
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Collimator rotation isocenter
Gantry rotation isocenter
Couch rotation isocenter
Coincidence of collimator, gantry,
couch axes with isicenter
2 mm dia.
2 mm dia.
2 mm dia.
2 mm dia.
QA of external beam radiation therapy equipment
Annual QA of medical accelerator
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Mechanical Checks
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Coincidence of radiation and mechanical isocenter
Table top sag
Vertical travel of table
2 mm
2 mm
2 mm
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QA of Newer Innovation on Medical
Accelerators
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Computer controlled and monitored operation ;
motorized autowedge; dynamic wedge; multileaf
collimators; record and verified systems; portal
imaging devices; stereotactic radiosurgery; and
intraoperative radiotherapy.
The guidelines of these systems that established by
the manufacturers for safe operation should be
strictly followed.
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QA of Simulators
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Subjected to the same mechanical checks as
accelerators.
In addition, the simulator should be checked for
image quality.
QA of CT Scanners
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A flat top insert on the CT table to reproduce the
radiation therapy treatment couch top.
A laser system mimicking that used in the
simulation and treatment units should be
mounted in the CT suite and the alignment of the
lasers should be checked daily.
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QA of CT Scanners
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The correlation of CT numbers with electron
densities and the variation of CT numbers with
position and phantom size should be determined.
This correlation should be checked yearly.
Image quality and other parameters described in
the QA protocol provided by the manufacturer
should be checked.
QA of Measurement Equipment
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As important as that of the radiation treatment
equipment and should be part of a QA program.
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QA of Measurement Equipment
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Redundancy in dose calibration equipment is
recommended to assure that instruments are
holding their calibration.
By comparing the response of the measurements
equipment with an appropriate long-lived
radioactive source ( Sr-90 ).
A two-system redundancy method provides
better accuracy than one system with check
source.
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Documentation and Records of QA
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This is very important that test procedures are
well documented for all units under the QA
program.
The results of initial baseline testing
( commissioning ) and future periodic testing be
recorded and dated.
QA records must be kept on file for a minimum
specified time ( typically 5 years, although
sometimes longer ).
Calibration Record Sheet for Daily, Weekly and Monthly Checks
Week I
T =
P =
Week II
Date:
fTP =
Rg(avg) Dose/MU
T =
P =
Vari.
Machine :
fTP =
Rg(avg) Dose/MU
Year :
Week III
Date:
T =
Vari.
P =
Week IV
Date:
fTP =
Rg(avg) Dose/MU
T =
Vari.
P =
Date:
fTP =
Rg(avg) Dose/MU
6X
6X
6X
6X
10X
10X
10X
10X
6E
6E
6E
6E
8E
8E
8E
8E
10E
10E
10E
10E
12E
12E
12E
12E
15E
15E
15E
15E
18E
18E
18E
18E
Daily
Daily
Daily
Daily
Check
Check
Check
Check
RAL Source Position
RAL Source Position
RAL Source Position
RAL Source Position
Ci RAL Source Activity
Ci RAL Source Activity
RAL Source Activity
RAL Timer Check
Note
Constancy Check
Date :
Uniformity Check
Mode
6X
10X
Date :
6E
8E
10E
12E
15E 18E
Ci RAL Source Activity
Date :
Energy Check
Keithley 617
6X
Flat.G-C
Victoreen500
10X
L-R
+PTW 30-351
Level
L-R
Mode
L-R
6X 10X
L
Agre. R
Simu.
Mode
Linac
Simu.
RgA
Check
8E
P. Check
10E
Cross-hair
Survey Meter
12E
Isocenter
Check
15E
Note
RgB
6E
Temp. Check
Note
18E
Note
Physicist:
Physicist:
Physicist:
Ci
Date :
Rg(5) Rg.(d) Rgd/Rg5 Var.
+ NE 2571
Symm.G-C
Vari.
Physicist:
RgB/RgA Var.
Constancy Check Report
Date :
2002/4/29
Temp.=
19.2
Pres. =
766
(mmHg)
3405.0
(day)
Decay Time=
Calibration date:
(℃)
f(T,P)=[760/P]*[(273.15+T)/295.15]
0.798273956
D.F.=
1993/1/1
=
0.9828
D.F.= 0.5^[Decay Time/(28.7*365)]
Keithley 35617 + NE 2571
Victoreen 500 + 30-351
Charge(nC)
Current(pA)
Charge(nC)
0.000
Current(pA)
Bg.
-0.001
-0.006
Bg.
Rg1
-6.72
-37.750
Rg1
-6.23
-0.035
Rg2
-6.80
Rg2
-6.21
Rg3
-6.74
Rg3
-6.23
Rg(avg.)
-6.75
-37.750
Rg(avg.)
-6.22
-34.700
Rg(cor.)
-8.31
-46.467
Rg(cor.)
-7.66
-42.676
Var.(%)
-0.588
-0.472
Var.(%)
-0.396
-0.719
-34.700
Tolerence : (+/-) 1%
Victoreen Battery :
Note :
300
(2001/4/27 change new bettary)
Keithley 35617 + NE 2571 for annual verification.
Rg.(Avg.)=Avg.(Rg.1+Rg.2+Rg.3+...)
Rg.(Cor.)=[Rg.(Avg.)-Bg.] * f(T/P) / D.F.
Standard Data :
(average, 1/94-12/94)
Keithley Sys.
Charge=
Current=
-8.362 (nC, for 3 min.)
-46.687 (pA)
Victoreen Sys.
Charge=
Current=
-7.692 (nC, for 3 min.)
-42.985 (pA)
Physicist:
蕭安成
Skin Kong Memorial Hospital Radiation Therapy and Oncology
Treatment Planning Worksheet
Name :
Chart number :
Diagnosis :
Doctor :
Localization date : _____________
Note :
Physicist :
Modality :□ CT
Image acquistition date : _____________
Note :
Recheck I date : _______________
Pre-planning center : (
,
,
)
□ MRI
Post-planning center : (
Physicist :
,
Physicist :
,
)
,
Physicist :
,
)
,
Physicist :
,
)
Shift (mm) □
: H □ F _____, □ R □ L _____, □ A □ P _____
Setup depth (cm) :□ AP □ LAT _____
Setup error (mm) :□ H □ F _____, □ R □ L _____, □ A □ P _____
Note :
Recheck II date : _______________
Pre-planning center : (
,
,
)
Post-planning center : (
Shift (mm) □
: H □ F _____, □ R □ L _____, □ A □ P _____
Setup depth (cm) :□ AP □ LAT _____
Setup error (mm) :□ H □ F _____, □ R □ L _____, □ A □ P _____
Note :
Recheck III date : _______________
Pre-planning center : (
,
,
)
Post-planning center : (
Shift (mm) □
: H □ F _____, □ R □ L _____, □ A □ P _____
Setup depth (cm) :□ AP □ LAT _____
Setup error (mm) :□ H □ F _____, □ R □ L _____, □ A □ P _____
Note :
Verification film
Date : ___________
Date : ___________
Date : ___________
Date : ___________
Date : ___________
Error (mm) :□ H
Error (mm) :□ H
Error (mm) :□ H
Error (mm) :□ H
Error (mm) :□ H
□F
□F
□F
□F
□F
_____,
_____,
_____,
_____,
_____,
□R
□R
□R
□R
□R
□L
□L
□L
□L
□L
** H : head, F : feet, A : anterior, P : posterior, R : right, L : left
_____,
_____,
_____,
_____,
_____,
□A
□A
□A
□A
□A
□P
□P
□P
□P
□P
_____
_____
_____
_____
_____
RAL NEW SOURCE ACTIVITY
2001/11/16
No.
Date
Factory Date
Today Act
23
2001/11/16
2001/11/8
10.3432
temperature
22.2
Time(hour)
Time(hour)
Decay(hr)204
pressure 774
1
2
1.446
1.458
5.741
5.793
Rg(60sec)CH1
CH2
Rg(240sec)CH1
CH2
exposure
23.4031
activity
Var.(%)
16
4.5
Activity 11.2
CTP 0.9826
3
1.446
1.459
5.743
5.793
Ci
1.446
1.458
5.744
5.793
1.4460
1.4583
5.7427
5.7930
average
1.4522
5.7678
10.1974
-1.4
(measurement/factory-1)*100
Ir-192 exposure-rate constant =
0.459 R m^2 / Ci h
Ir-192 half-life =
73.83 day
Keith.+2571
(Nx)xray= 4.6178
(Nx)cs= 4.7709
reading(3min)
(Nx)Ir
Aion
Pion
Pgrad
CTP
4.3157
5.4480
1
1
1.004
0.9826
Exposure = Rg * Nx * Aion * Pion * Pgrad * Ctp * Prs * Ccap
(Nx)Ir = ( 1+x ) * [ (Nx)x-ray + ( Nx) Cs ] /2
x = 0.0037 * ( t /9.3*10 ^22 )
t = wall thickness ( electrons / cm^2 ), wall + buildup cap
Keithley Dosimetry System, Keithley electrometer + NE 2571 0.6 cc ion chamber
wall thickness=
0.0650
g/cm^2
wall material =
3.008E+23
graphite electron density ( electrons / g)
cap thickness=
0.5510
g/cm^2
cap material=
3.211E+23
Delrin electron density ( electrons / g)
t=
1.965E+23
electrons / cm^2
x=
0.007817
( Nx ) Ir =
4.7310
Note: Measurements were performed with Victoreen 500 electronmeter and
Victoreen 30-351 ion chamber, Nx was estimated about 1% higher than
the Co-60 calibration factor, and Pion , Aion = 1. ( Nx = 5.394 *1.01 = 5.448 )
Physicist : 蕭安成
Prs
Ccap
0.999 1.01
Treatment Planning Computer System
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Commissioning and QA for external beam :
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The calculation of relative dose distributions for relative
machine, energy, and modality.
The summation of relative doses from different beams
The calculation of monitor units for a given prescribed
dose.
Production of clear and accurate output data, including
graphical isodose distributions.
Independent computer “MU” programs.
Treatment Planning Computer System
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Concerns for Brachytherapy :
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The dose distribution is correct for the source type in use.
The spatial reproduction of the implant is appropriate
Dose summations are calculated correctly.
A treatment planning system should be tested over
a range of parameters which would be typical of
those used in the clinic, and should be tested on a
periodic basis.
Treatment Planning Computer System
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Program Documentation
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Beam Data Library
 The manufacturer should provide clear
documentation on the procedures for acquiring and
transferring beam and other necessary data to the
treatment planning system’s data library.
 Users should acquire their own basic beam data sets
Dose Calculation Models
 The documentation should describe the required
dosimetric input data set and the expected accuracy of
the dosimetric calculations for various conditions.
Treatment Planning Computer System
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Program Documentation
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Dose Calculation Models
 Discuss the limitations of the dose calculation models.
Operating Instructions and Data I/O
Test Procedures
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Initial Manufacturer’s Tests
Initial User Test Procedures
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Commissioned for each treatment machine. Energy. Modality
and for each isotope at the time of purchase of the software,
annually, and every time a software upgrade is installed.
Treatment Planning Computer System

Test Procedures

Initial User Test Procedures
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Calculated dose distributions for a select set of
treatment conditions in standard phantoms be
compared to measured dose distributions for the same
phantoms.
A reference set of treatment planning test cases
should be established. This set should be used for
yearly recommissioning of the treatment planning
system.
Treatment Planning Computer System

Test Procedures
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Tests After Program Modification
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QA tests always be performed on the treatment
planning system after program modification. The
results should be compared to the initial acceptance
test results.
External Beam Treatment Planning
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Nongraphical planning
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Single or parallel opposed fields.
Traditional graphical planning
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Target volume is defined from CT or orthogonal
simulation films.
The field arrangements are designed and dose
distributions calculated on one or a limited number of
axial cross sections using a computerized planning
system.
External Beam Treatment Planning
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3D treatment planning
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Target volume, normal tissue volumes, and surface
contours are obtained directly from CT.
Field design, the field apertures are defined using BEV
Prescribed dose to a point, isodose curve, isodose surface,
or dose volume histogram( DVH ).
Treatment Planning QA for individual Patients

Treatment Plan Review
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All graphical treatment plans should be signed and dated by
individual who formulated the plan, and by the radiation
oncologist.
External Beam Treatment Planning
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Treatment Planning QA for individual Patients
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Treatment Plan Review
 Assure that the monitor units are correct, that all
machine parameters used for patient setup are correct.
 The quality of the plan meets department standards
 All signatures, prescriptions, etc. are recorded.
 Independent calculation of the dose at one point in
the plan. If the independent calculation differs by
more than 5% from the treatment plan, the disparity
should be resolved before commencing.
External Beam Treatment Planning
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Treatment Planning QA for individual Patients
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Monitor Unit Calculation Review
 Initial calculation be signed and dated by the
individual who performed it and reviewed by
physicist.
Plan Implementation
 All parameters in the treatment plan should be
verified during first setup.
 Port films
 Radiation oncologist be present at the treatment
machine for first setup and for major changes.
External Beam Treatment Planning
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Treatment Planning QA for individual Patients
A check of the setup by the physicist will minimize
errors.
In Vivo Dosimetry
 In vivo dosimerty can be used to identify major
deviations in the delivery of treatment and to verify
and document the dose to critical structures.
 TLD or other in vivo systems.
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Brachytherapy
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Brachytherapy is the use of encapsulated
radioactive sources to deliver radiation dose within
a distance of a few centimeters by surface,
intracavitary, interstitial or intraluminal
applications.
One goal of QA is to achieve a desired level of
accuracy and precision in the delivery of dose.
For external beam therapy dose delivery < 5%
For intracavitary brachytherapy, an uncertainty of
15% in the delivery of prescribed dose is a more
realistic level.
Sealed Sources

Description of Sources
The radiation characteristics of an encapsulated
source are strongly dependent upon the distribution
of the activity within the source and the details of
the source encapsulation.
 Physical and chemical form
The chemical composition of the radionuclide and
inert filler material should be provided by the
manufacturer.
Sealed Sources

Source encapsulation
Source encapsulation can influence the source
calibration, the dose distribution, and the physical
integrity of the source. This information should be
available by the manufacturer.

Source identification
It is essential to be able to distinguish between
sources that have the same radionuclide and capsule
design but different activities.
Sealed Sources

Calibration of sources
Although commercial suppliers of brachytherapy
sources provide a measure of source strength, it is
unwise to rely solely on this value for patient dose
calculations.
Each institution should have the ability to
independently verify the source strength provided by
the manufacturer.
Sealed Sources

Calibration of sources
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Specification of Source Strength
AAPM recommend that the quantity of radiation
emanating from a source be expressed as “ airkerma strength”.
Traceability of Source Calibration
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Direct traceability
Secondary traceability
Sealed Sources

Brachytherapy Source Calibrators
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Well ionization or reentrant chambers are
preferred for conventional strength
brachytherapy sources.
Thimble chambers are preferred for high dose
rate sources.
The radiation oncology physicist should identify
a single dosimetry system that will be used for
brachytherapy calibration.
Remote Afterloading
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Accuracy of source selection
Spatial positioning.
Control of treatment time.
QA of Clinical Aspects
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New Patient Planning Conference
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Should be attended by radiation oncologists, radiation
therapists, dosimetrists, and medical physicists.
The pertinent medical history, physical and diagnostic
findings, tumor staging, and treatment strategy
( including the prescription and considerations of normal
organ dose limits ) should be presented by the attending
radiation oncologists and residents.
For each patient, the prescribed dose, critical organ doses,
possible patient positioning, possible field arrangements,
and special instructions should also be discussed.
QA of Clinical Aspects
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Chart Review --- Basic Component of a Chart
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Patient identification
Initial physical evaluation of patient and pertinent
clinical information
Treatment planning
Signed and witness consent form
Treatment execution
Clinical assessment during treatment
Treatment summary and follow-up
QA check lists
QA of Clinical Aspects
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Chart Review --- Overview of Chart Checking
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The items recording in the radiation chart are reviewing
by a number of individuals at different times during the
patient’s treatment.
Charts be reviewed
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At least weekly
Before the third fraction following the start of each new
treatment field or field modification
At the completion of treatment
The review be signed and dated by the reviewer.
All errors be reviewed and discussed by the QA
committee.
QA of Clinical Aspects

Chart Check Protocol --- Review of New or
Modified Treatment Field
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
The first task of the chart reviewer is to identify any
changes in the treatment (e.g., changes in field size, dose
per fraction, etc.) or new treatment fields since the
previous weekly chart review.
Chart Check Protocol --- Weekly Chart Review

As part of the weekly chart review, the reviewer should
determine for each patient whether any new fields have
been created or any previously treated fields modified.
QA of Clinical Aspects

Film Review --- Types of Film
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Portal-localization images.
Verification-localization images
On-line imaging devices ( electronic portal imaging )
Initial portal imaging
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To verify that the radiation field isocenter is correctly
registered with respect to the patient’s anatomy.
The aperture ( blocks or MLC ) has been properly
produced and registered with respect to the isocenter.
QA of Clinical Aspects

Initial portal imaging
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Portal films be obtained for all treatment fields prior to
first treatment.
Where oblique or noncoplanar fields are used,
orthogonal films imaging isocenter should be obtained.
If first day setup modification are not made, positioning
errors may persist as systematic deviation throughout the
course of treatment.
QA of Clinical Aspects

Ongoing Portal and Verification Images
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Day-to-day variations in patient setup are likely to be
random and smaller in magnitude than first-day
variations.
Patient position observed on one day may be simply a
random error which cannot be controlled. Such potential
setup errors should be monitored for a few consecutive
days and the patient’s position should be modified only if
they persist.
The relative frequency of localization errors diminishes
as the frequency of portal and localization films
increases.