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Image guided adaptive brachytherapy (in cervix cancer) – Physics aspects

Christian Kirisits

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D I A G N O S I S

25 Months Follow

up

High Risk CTV = HRCTV

Coronal view Sagittal view Axial view

A T I G A B T

63Gy

IRCTV

88Gy GTV

HRCTV

IGABT = Image Guided Adaptative Brachytherapy

Cervical Cancer FIGO IIIB

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In-room imaging?

3

Delivery device

Delivery device

Room

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Visualization of the “real” source positions in relation to the outer dimensions and holes of the Vienna ring applicator

r26

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Planned positions verified by QA (autoradiography)

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Applicator surface

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Source path

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Applicator + Source path

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Registration of dose delivery device with anatomy

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Treatment Planning directly on 3T MR

• Import vendor provided archived applicator into planning images

• Can use with 3D SPACE or T2 FSE

Courtesy B. Erickson, MCW

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Treatment planning

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Standard loading pattern

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Shifting and skipping dwell positions

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Standard loading pattern

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Optimized loading pattern

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Standard loading

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Inverse optimization Use with caution due to missing constraints for

spatial dose distribution!

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Dose Optimization

DVH parameters (D90, D98, D2cc, D0.1cc) Spatial dose distribution (Hot and Cold spots) Dwell time distribution to take into account not contoured structures parametrial tissue vagina nerves vessels ureter

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Manual optimization

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Manual plan

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IPSA

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Inverse optimization

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Application technique and patterns of tumor regression

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Vienna I and Vienna II applicators

Berger et al.

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COMMERCIAL PRODUCTS

based on

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Preplanning without applicator in situ

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3D printed applicators

preplan

3D print

Virtual design

Implant

Courtesy – J. Lindegaard, Aarhus & Lindegaad et al. Radiother Oncol 2016

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Dose Distribution at Ovoids with shields TG43 (no shields) TG186 (shields modeled)

200% 150% 100% 50%

Output of OncentraBrachy 4.5 with ACE - courtesy of F. Mourtada

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Review of clinical brachytherapy uncertainties: Analysis guidelines of GEC-ESTRO and the AAPM

Christian Kirisits, Mark J. Rivard, Dimos Baltas,

Facundo Ballester, Marisol De Brabandere, Rob van der Laarse,

Yury Niatsetski, Panagiotis Papagiannis, Taran Paulsen Hellebust,

Jose Perez-Calatayud, Kari Tanderup, Jack L. M. Venselaar,

Frank-André Siebert

Radiother Oncol 2014

BRAPHYQS

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Example for HDR intracavitary Cervix brachytherapy – per fraction Category Optimum level Assumptions Source strength 2% PSDL traceable calibrations Treatment planning 3% Reference data with the appropriate bin width is used Medium dosimetric Applicator without shielding and CTV corrections 1% inside pelvis (concerning for scatter) Dose delivery including Accurate QA concept for commissioning & registration of applicator constancy checks, especially for source geometry to anatomy 4% positioning and applicator/source path geometry, appropriate imaging, applicator libraries Interfraction/Intrafraction For one treatment plan per applicator changes 11% insertion but several subsequent fractions – check for major deviations in subsequent fractions Total dosimetric uncertainty 12% for one single fraction

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Example for HDR intracavitary Cervix brachytherapy – total dose 4 fractions Category Optimum level Assumptions Source strength 2% PSDL traceable calibrations Treatment planning 3% Reference data with the appropriate bin width is used Medium dosimetric Applicator without shielding and CTV corrections 1% inside pelvis (concerning for scatter) Dose delivery including Accurate QA concept for commissioning & registration of applicator constancy checks, especially for source geometry to anatomy 4% 2% positioning and applicator/source path geometry, appropriate imaging applicator libraries Interfraction/Intrafraction For one treatment plan per applicator changes 11% 6% insertion but several subsequent fractions – Total dosimetric uncertainty 7% for entire BT

1 / √N

1 / √N

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Expected interfraction variations for cervix BT

2cc1cc

0.1cc

Bladder

Rectum

ICRU 38 Ref. Points

GTV

Sigmoid

Target should remain fixed relative to applicator

Rectum: may slightly change in location and fill with gas

Bladder: use of bladder filling protocols

Sigmoid: change its location

Hellebust et al. R&O 60, 2002 Lang et al. R&O 107, 2013 Kirisits et al. R&O 2006 Nesvacil et al. R&O 107, 2013 Tanderup et al. R&O 107, 2013 (and references therein)

Radiother Oncol 107

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Random uncertainties (1SD) of physical dose per BT fraction can be

~ 10% for HR CTV D90 (contouring uncertainty (Petric, Hellebust R&O 2013)) ~ 20% for bladder, rectum D2cm³ ~ 30% for sigmoid D2cm³

No correlation with time between images was detected!

Multicenter Center study of inter-/intrafraction variations for target and OARs in cervix BT

total 2.7 1.5 20.3% 4.5 4.1 22.0% 1.6 -0.9 26.8% -1.1 -1.7 13.1% Intraaplication 1.3 1.5 17.7 3.8 2.3 20.5 -2.3 -3.7 23.5 -2.5 -4.3 10.8

interapplication 3.9 0.0 22.3 5.8 5.2 23.2 6.8 3.7 30.2 0.4 -0.8 15.1

∆ D2cm³ between 2 acquisitions [%] (fixed plan, variable anatomy)

∆ D90 [%] (fixed plan, variable

anatomy) bladder rectum sigmoid/bowel HR CTV

Mean median SD mean median SD mean median SD mean median SD

Nesvacil et al. 2013, Radiother Oncol 107

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Increasing OAR dose constraints by reducing uncertainties

10%

20% 30%

Response uncertainty range ~6% for SD 30% @ 70 Gy EQD2 SD 20% @ 75 Gy EQD2

Clinician could consider relaxing the OAR dose constraint for this case!

DD=5 Gy

Nesvacil et al. 2016

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1st application 2nd application MRI- based planning: 3D applicator reconstruction

target delineation OAR delineation Dose planning and optimization

CT- based planning: 3D applicator reconstruction Automatic target transfer from 1st MRI via applicator-based image registration OAR delineation Dose planning and optimization

Image guidance for each fraction? Combined MRI-/CT- guided BT for cervical cancer

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Applicator, target (HR CTV), OAR (rectum, bladder, sigmoid) Dose planning and optimization on target+organ contours

1st application: MRI

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3D applicator reconstruction

2nd application: CT

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3D applicator reconstruction Target transfer

Targets from first application MRI 2nd application: CT

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Automatic target transfer from MRI to CT with applicator as reference system

2nd application: CT

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Fig. 1

Brachytherapy 2015 14, 390-400DOI: (10.1016/j.brachy.2014.12.001)

Copyright © 2015 Terms and Conditions

Ultrasound use in gynecologic brachytherapy: Time to focus the beam Sylvia van Dyk, Michal Schneider, Srinivas Kondalsamy-Chennakesavan,

David Bernshaw, Kailash Narayan

Brachytherapy Volume 14, Issue 3, Pages 390-400 (May 2015) DOI: 10.1016/j.brachy.2014.12.001

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Modern high-tech external beam versus

Cheap and simple Brachytherapy

High-tech image-guided therapy versus low-tech, simple, cheap gynecologic brachytherapy. Kirisits C, Schmid MP, Beriwal S, Pötter R. Brachytherapy. 2015 IMRT, IGRT, and other high technology becomes standard in external beam radiotherapy: But is image-guided brachytherapy for cervical cancer too expensive? Swamidas JV, Kirisits C. J Med Phys. 2015

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TRUS?

Transrectal ultrasonography… …has „direct contact“ to the target volume …has a reasonable soft tissue contrast …allows dynamic real time imaging …is already implemented in prostate cancer brachytherapy …is a low cost imaging modality …is widely available

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Maximum target width

Blinded retrospective analysis of consecutive patients at same time points n=19

US

CT

Schmid et al. Radiother Oncol 2016

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Transrectal ultrasound for target definition in CT-based cervix cancer IGABT (no access to MRI @BT)

TRUS target delineation

pre-implant scan, TRUS guidance of implantation

volumetric post-implant scan

applicator tracking

TRUS-CT registration via applicator

Schmid et al. R&O 2016, Nesvacil et al. Brachytherapy 2016

(ACMIT, Elekta)

main uncertainty: tracking

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Depiction of Titanium needles on TRUS images

Schmid et al. R&O 2016, Nesvacil et al. Brachytherapy 2016

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Comparison of target structures delineated on TRUS, CT and MRI – all targets transferred to CT by applicator-based registration, OAR delineation on CT

CTVHR-CT CTVHR-US CTVHR-MRI volume (cm³) 59 30 30.9 width (mm) 71 53 49 thickness (mm) 52 34 33 height (mm) 37 31 35

Schmid et al. R&O 2016, Nesvacil et al. Brachytherapy 2016

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Beaulieu et al. Chapter 9

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Beaulieu et al. Chapter 9

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Dose delivery with in-vivo dosimetry verification

Courtesy of K. Tanderup

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Andersen et al. Med. Phys. 36 (2009) 5033–5043

Only time-resolved

TIME-RESOLVED IVD!

Slide by L. Beaulieu, AAPM summer school 2017

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Conclusion

• Infrastructure for imaging (equipment and staff)

• Reproducible and standardized concept for target and OAR delineation

• Applicator reconstruction

• Optimization (protocol including constraints for dose/volumes and dwell times)

• Dose and volume parameters for planning aim, prescription and reported (delivered) dose

• Lowering uncertainties with new technology