1.
Quality Assurance (QA) for
Prostate Brachytherapy
Bashar Al-Qaisieh

2.
Overview
• TG 43 and TG43-U1
• Seed & Needle Check
• Template Calibration
• Ultrasound Machine Check
• Commissioning Planning System
• Treatment Plan Check
• Post Implant QA

3.
TG 43 and TG 43-U1
Report of American Association of Physicists in Medicine
Radiation Therapy Committee Task Group 43
Medical Physics, 22(2), 209-235, Feb 1995
Update of AAPM Task Group No. 43 Report: A revised
AAPM protocol for brachytherapy dose calculations
Medical Physics, 31 (3), 633-674 Mar 2004

4.
TG43-U1
• Clear definitions of physical quantities, and all the
equations required for the calculation of dose.
• Treatment planning systems.
• Source calibration.
• Planning systems commissioning.
• Universal standards.
• Theoretical and experimental recommendations.
• And more…….
.

5.
TG-43 : General Dose
Calculation Algorithm
D(r,θ)=SkΛ[GL(r,θ)/GL(r0,θ0)]gL(r)F(r,θ)
The dose rate, D(r,θ) is defined as

6.
Cylindrically symmetrical source
y
z
r0=1cm
P(r,θ)
β
θ
L
P(r0,θ0)
Reference point is chosen to lie on the
transverse bisector of the source at a
distance of 1cm from its centre i.e.
r0=1cm and θ0=π/2

7.
D(r,θ)=SkΛ[G(r,θ)/G(r0,θ0)]g(r)F(r,θ)
Sk= air kerma strength of the source
Λ= dose rate constant
G(r,θ)=geometry factor
g(r)=radial dose function
F(r,θ)=anisotropy function

8.
TG 43-U1, Why bother?
HL241.44AL
ALθ)(r,DD(r) .
××=
×=

9.
TG43 TG43-U1

10.
TG43-U1

11.
Seed Calibration-Well chamber
• Calibration every two
years. Med. Phys. 18,
1991.
• Consistency check.
Cs-137, Co-60

12.
Guidelines
“The activity of all sources should be
measured, and compared with the
calibration certificate supplied by the
supplier, before being administered to
a patient”…..Medical and Dental Guidance Notes, IPEM

13.
Seed Calibration
•Sterile sources located in
MICK magazine
- a minimum of 10% of the total or
two magazine cartridges of 15
seeds, whichever is greater.
• Sterile stranded sources.
- a minimum of 10% of the total or
two strands of 10 seeds, whichever
is greater.
• Loose seeds
- a minimum of 10% of the total or
20 seeds, whichever is greater.

14.
Needles Check
• Verification of loaded brachytherapy
needles.
• Place a film on top of the needles.
The radiation from the loaded
needles exposes an image in the film.
• The film will verify correct loading
of seeds and spacers within each
needle, or indicate any discrepancies
or missing seeds.

15.
Needles Check

16.
Template Calibration
Ultrasound Template
Planning TemplateGuidance Template
Level of tolerance is ± 1mm

17.
Template Calibration

18.
Ultrasound Machine Check
• Assurance of Mechanical and Electrical Safety
• Distance Accuracy (vertical and horizontal)
• Contrast and Brightness (Gray bar
visualization)
• Image Uniformity
• Penetration
• Lateral Resolution
-IPEM report 71: Price R et al. 1995/2002
-TG –1: Goodsitt et al. Med Physics 25(8) 1998.

19.
Clinical Commissioning of
Planning System
(VariSeed™ System & 6711 seed)
– Test 1: Dose Point Calculation-TG 43-U1
– Test 2: Isodose Level-TG 43-U1
– Test 3: Volume and Dose Volume-TG 43-U1
– Test 4: Anisotropy Function/Line Source Calculation-
TG43-U1
– Test 5: Data transfer and handling
– Test 6: Stepper Depth and Angle Tracking and
Accuracy Tests

20.
Dose Point Calculation Test
• This dose calculation
verification test uses a
dose point(s) to verify
the calculations of the
planning system.
Discrepancy should be
within 1%.
0.5cm
P1 P2
1cm 2cm
S2 S1
Dose rates (cGy h-1 U-1) as a function of distance

21.
Isodose Level Test
• This test is to verify
the display of isodose
levels
• The distance
discrepancy of
contours and template
should be within ± 2
mm

22.
Isodose Level Test
0 click back 1 click back
2 clicks back 3 clicks back

23.
Dose Volume Test
• This test uses DVH values to verify
the dose volume calculation of the
planning system.
• Discrepancy should not exceed 5%.

24.
Dose Volume Test-Example
75.831 U
3.0cm
100Gy Isodose
ccrV 1.113
3
4 3
== π

25.
Dose Volume Test

26.
Anisotropy Function/L-Source
Calculation Test
• This test is to verify the line source
approximation calculation which uses
anisotropy function data.
• Discrepancy should not exceed 1%.

27.
Anisotropy Function/L-Source
Dose @ 0 degree
Source Isodose

28.
Anisotropy Function/L-Source
Dose @ Arbitrary r and θ
Example of
Dose calculation for
different point
positions

29.
Image transfer check
(Ultrasound phantom)
1.4cm
1cm

30.
Volume Test
• Check volume captured
from US is similar to
the volume contoured
on planning system.
• Discrepancy should be
within ± 1cc.

31.
Stepper Depth and Angle
Tracking Tests
Longitudinal movement-Retraction
Rotational movement- US Probe Angle

32.
Stepper Depth and Angle
Tracking Tests
• Longitudinal Position Tracking. Accuracy
should be within 0.5mm.
• Rotational Tracking Test. Accuracy should
be within 0.5 degrees.

33.
Stepper Depth Tracking Test
e.g: 3 clicks back = 1.5cm

34.
Stepper Angle Tracking Test
A
B
== )tan(
A
B
arcθ
θ

35.
Treatment Plan Check
• Physics check
• template grid not calibrated correctly
• planning grid not aligned with template grid
correctly
• wrong prescribed dose (beware boosts!)
• wrong dosimetry data in computer
• wrong activity seeds
• incorrect manual transfer of information
• Oncology check

36.
Post implant CT-MR Image
Fusion QA
MRI
CT
+
Fused Image

37.
Image Fusion Protocol Phantom
Study
CT MRI Fused Image
+ =
RMS Error < 1.0mm

38.
QA for HDR Brachytherapy
Besides the typical QA procedures
established for common HDR
Treatments, we need to implement
additional ones

39.
•Better visibility
•Improved treatment
planning
•Reproducibility
3D ultrasound

40.
Mechanical & US Image Geometry

41.
Catheter Reconstruction
 





42.
Pre-Calculation Quality Assurance
Checks
• Objective:
Test the integrity of the treatment planning system and
check the current source data file and equipment setup.
• Procedure
US probe mark, verify stepper encoder, AKS, point
dose calculation, isodose plot..etc

43.
Isodose/DVH check
This test uses DVH values to verify the dose volume
calculation of the planning system.
e.g.
Oncentra Prostate valueParameter Value
D90 5.9740 Gy
V100 235.9343 cm3
V150 151.8108 cm3
V200 108.0353 cm3
Performed by:

44.
Data transfer check
e.g.

45.
Data transfer check
e.g.

46.
Image transfer check
(Ultrasound phantom)
Correct value? (Tick)Parameter Ideal value Tolerance
Vertical spacing 1.0 cm 0.1 cm
Diagonal spacing 1.4 cm 0.1 cm
Small volume 3.6 cm3
1.0 cm3
Medium volume 8.8 cm3
1.0 cm3
Large volume 20.4 cm3
1.0 cm3
Performed by:
e.g.

47.
3D ultrasound
0
2
4
6
8
10
12
14
16
18
20
-6 -5 -4 -3 -2 -1 0 1
Slice position (cm)
Slice area (cm2
)
1st fraction
2nd fraction

48.
External Catheter Length
QA Measurements
P.J. Hoskin et al. / Radiotherapy and Oncology 286 68 (2003) 285–288

49.
Possible Sources of Catheter
Movement
P.J. Hoskin et al. / Radiotherapy and Oncology 286 68 (2003) 285–288

50.
Possible Sources of Catheter
Movement
P.J. Hoskin et al. / Radiotherapy and Oncology 286 68 (2003) 285–288

51.
Summary
• Seed Calibration (Constancy check)
• Template Calibration
• Ultrasound Machine Check
• Commissioning Planning System
– Test 1: Dose Point Calculation Test
– Test 2: Isodose Level Test
– Test 3: Volume and Dose Volume Test
– Test 4: Anisotropy Function/Line Source Calculation
– Test 5: Data transfer
– Test 6: Stepper Depth and Angle Tracking Tests
• Treatment Plan Check
– Check list
• Post Implant QA