1. GHG meeting at ESTRO36 May, 2017
SBRT trial QA
GHG meeting at ESTRO36 May, 2017
I would like to talk about JCOG SBRT trial QA.
I am Mitsuhiro Nakamura from Kyoto University.
I am a medical physicist.

2. Current trial JCOG1408 (J-SBRT trial)
A randomized phase III trial of comparing two dose-fractionations SBRT for medically inoperable stage IA non-small cell lung cancer or small lung lesions clinically diagnosed as primary lung cancer
PTV D95: 42 Gy vs 55 Gy
Now, we are conducting JCOG1408.
This is a randomized phase III trial of comparing two dose-fractionations SBRT for medically inoperable stage IA non-small cell lung cancer or small lung lesions clinically diagnosed as primary lung cancer.
One dose-fractionations is that PTV D95 should be 42 Gy in 4 fractions.
The other is that PTV D95 should be 55 Gy in 4 fractions.

3. Trial QA activities Facility questionnaires Dummy run
Verification of small field dosimetry
IGRT verification by postal audit
Postal audit for IMRT credentialing
Respiratory motion management
Individual case review
Trial QA activities includes these seven.
At the beginning of this study, we do not allow IMRT because of interplay effect.
But, IMRT is now widely used in clinical practice.
So, we allow institutions to use IMRT.
We require #5 and #6 for IMRT institutions.

4. 1. Facility Questionnaires
Linac, RTPS (Heterogeneity Correction), Planning CT, IGRT, etc.
Q: Prescription in clinical practice
Prescription in JCOG1408
PTV D95=42 Gy or 55 Gy
PTV is covered by 80% isodose line
We distributed facility questionnaires to understand each situation.
The questionnaires includes XXX.
This is a representative answer of the questionnaires.
We asked how to prescribe the dose before starting this trial.
Numbers responded is 30.
Only 20% of institutions use peripheral dose prescription.
And 80% of institutions use others, such as isocenter prescription.
However, JCOG1408 requires peripheral dose prescription.
So, we recognized the necessity of dummy run.
Necessity of dummy run

5. 2. Dummy run
Planning instructions, CT image sets, and DICOM-RT structure of 2 cases were provided to each institution.
ROI names are harmonized based on the GHG publication.
Treatment plans were designed based on the protocol.
To conduct dummy run, we prepared for planning instructions.
And, DICOM CT file and structure files of 2 cases were provided to each institution.

6. No deviation Major deviation
This slide shows representative dose distributions and BEV.
Left shows no deviation case, and right major deviation case.
Compared with left figure, lung received more doses and conformity is not good.
Some institutions did not know how to design a plan with peripheral prescription.
For these institutions, we taught how to design plan.

7. 3. Verification of small field dosimetry
Calculation accuracy of small field down to 2 x 2 cm2 was verified by specified Excel sheet.
5cm cm depth is automatically calculated from the returned Excel sheets from each institution.
Typically, small fields are used for lung SBRT cases.
So, we check calculation accuracy of small field down to 2 x 2 cm2.
We provide specified format of Excel sheet to each institution.
And then, institutions calculate and 10 cm depth in water.
Tolerance: Mean among institutions for each type of linac ±3%

8. Scenario: Measurement is not required1
Data (cGy/MU) are collected from participating inst.
Inst. A
TrueBeam (6X)
Inst. B
TrueBeam (6X)
Inst. C
TrueBeam (6X)
Inst. D
TrueBeam (6X) 2
Averaged cGy/MU for TrueBeam (6X)
First, we collect calculated cGy/MU for small field from participating institutions.
In this slide, I will show you scenario that measurement is not required.
For example, institutions A to D have Varian trueBeam.
They will use 6MV photon beam for protocol cases.
We collect calculated cGy/MU for small field from these institutions, and then calculate averaged cGy/MU for TrueBeam 6X.
When new participating institution treat protocol cases with Truebeam 6MV, we collect cGy/MU from the new institution.
We compare averaged cGy/MU with calculated cGy/MU of the new institution.
If the deviation is within the tolerance of +/-3%, the new institution is credentialed for small field. 4 3
Comparison
New participating institution has TrueBeam (6X)
Calculation of output for small field

9. Scenario: Measurement is required
A new participating institution has Elekta (6XFFF).
Other participating institutions do not have Elekta (6XFFF).
We cannot compare institution-specific output with averaged output from other institutions for small field.
Institution-specific output is measured in water. Calculated output (TPS) is compared with measured one at the institution.
On the other hand, this slide shows the scenario that measurement is required.

10. 4. IGRT verification by postal audit
E2E verification
CT  Planning  IGRT  Dose Delivery
RTQA2 films
Dummy
Target
(x1, y1)
Translational Error (mm)
Next is IGRT verification by postal audit.
We mailed original IGRT phantom which contains a hidden target and RTQA2 films to institutions.
Institutions take CT scan, and make a treatment plan.
Based on the treatment plan, they deliver dose after target matching.
We analyzed irradiated films according to these equations.
From these equations, we can calculate translational and rotational errors.
Tolerance: Translational errors ±1mm, rotational errors ±1°
(a,b)
offset
7cm
14cm
Rotational Error (degree) θ
(x2, y2)
Tolerance: Translational errors ±1 mm, rotational errors ±1°

11. 5. Postal audit for IMRT credentialing
JCOG RTSG/MP WG
Participating institute
1. Development of IMRT phantom
2. Glass dosimetry: reliable, small size, high sensitivity.
3. Assessment of dose calculation accuracy in PTV and OAR.
CT scan and planning according to a dedicated protocol
Beam delivery
For institutions participating JCOG1408 with IMRT, we preform postal audit for IMRT credentialing.
We mail IMRT phantom which contains glass dosimeters and films.
They take CT scan and make a treatment plan, and then deliver dose.
After that, they return the phantom to us, and we analyze the glass dosimeter and films.
【Tolerance】
Glass dosimeter: 5%
EBT2: 3 mm
(γ: 3%/3mm)
1. Analysis and reporting.
2. Average 2 weeks until
submitting report.

12. 6. Respiratory motion management
Questionnaire
How to measure respiratory motion
How to determine ITV
Tips at treatment planning
How to verify IMRT dose under moving condition
Submit the verification results
We require a questionnaire on respiratory motion management.
In the questionnaires, we ask institutions XXX.
In addition, we require to submit the verification results under management of respiratory motion.
This figure is an example of dose distribution in phantom study.
Upper shows dose distributions under static condition, and lower under free breathing.
We judge whether the respiratory motion management used in the participating institutions is appropriate or not.

13. 7. Individual case review
All protocol patients undergo review retrospectively.
[Clinical review]
Total dose
Start date
OTT
Finally, we review all protocol patients retrospectively.
In clinical review, we check total dose, start date, overall treatment time, contouring, and so on.

14. 7. Individual case review
[Physics review]
In physics review, we check CT slice thickness, XXX.
CT slice thickness, energy, delivery technique, calculation algorithm, heterogeneity correction, grid size, etc.

15. 7. Individual case review
[Dosimetry review]
Of course, we check dose-volumetric parameters.