The Future of Brachytherapy - IFMP · Image guided brachytherapy •Slow introduction of new...

The Future of Brachytherapy

Alex Rijnders Europe Hospitals Brussels, Belgium

a.rijnders@europehospitals.be Sarajevo, May 21, 2014

Brachytherapy = application of sealed sources inside or in close proximity of tissue

Important milestones

Early 1900s: use of Radium for BT

1930s: Manchester System

End 1950s: artificial isotopes (60Co – 137Cs)

1960s: 192Ir wire sources – Manual afterloading techniques – Paris System

1970s-1990s: Remote Afterloading Devices

2000s: Imaging Assisted Brachytherapy

2010s: Improved dose calculation algorithms

Temporary Implants LDR

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours

Dose

Rate

PDR

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Dose

Rate

Low Dose Rate: v  Continuous

irradiation v  0.40 – 2 Gy/h

Pulsed Dose Rate: v  mimic low dose rate v  short pulses, same

average dose rate

High Dose Rate: v  >0.2 Gy/min v  One/a few fractions

LDR

PDR

HDR

HDR

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Dose

Rate

Current/Future Developments

n  Sources - Isotopes n  Afterloaders / applications n  Use of modern imaging techniques/tools n  Dose calculation (TPS) n  Recommendations for registration and reporting n  Uniformity and accessibility of basic dosimetrical

data (ESTRO-Braphyqs / AAPM) n  …

•  Long Half Life

=> Economical use (! Radioactive waste !)

•  High Specific activity: activity per unit of mass

=> physical size of source (2mm catheters)

•  Low mean energy of radiation

=> less penetration in tissue

•  Small half value layer in lead or concrete

=> radiation protection

Ideal source/isotope

Physical properties of nuclides

λ=ln2 / T½

Isotope Average photon energy* Half-life T½ Half value

layer in lead Treatment room wall

Cobalt-60 Co-60 1,25 MeV 5,26 years 12 mm (Concrete) typical values

Caesium-137 Cs-137 662 KeV 30,1 years 6,5 mm

Iridium-192 Ir-192 380 KeV 73,8 days 3,0 mm (40 cm)

Ytterbium-169 Yb-169 93 KeV 32,0 days 0,23 mm

Thulium-170 Tu-170 66 KeV 128.6 days 0,17 mm (12 cm)

Iodine-125 I-125 28 KeV 59,4 days 0,025 mm (4.5 cm)

Palladium-103 Pd-103 21 KeV 17,0 days 0,01 mm (1 cm)

Caesium-131 Cs-131 30 KeV 9,7 days - * Approximate values, depending on the source make and filtration

⇒  Radioprotection:

Ø  Reduced Mean Energy (<= 100 KeV)

Ø  Yb-169, Tu-170, I-125, Pd-103

⇒  Increased half-life (source exchange)

Ø  Co-60

« New » Isotopes

Electronic BT sources

Cost differences ? Clinical results ?

Bx Source

Advantages

Disadvantages

radionuclide Well established therapeutic use

Well established calibration procedures Fixed photon spectrum and half-life High specific activity, small size

Fixed dosimetry properties Radioactive waste concerns Regular source shipments due to decay

electronic User-adjustable dose rate (on/off) User-adjustable dosimetric properties Lessened radiological exposure to staff

Unproven clinical application Output variability amongst sources Typically larger in size

X-ray source tip detail

Miniature x-ray source inserted into a flexible cooling catheter §  High vacuum x-ray tube technology §  50 kV max. operating potential §  Water cooled §  Fully disposable device

X-Ray Tube HV Cable Cooling connections

HV connection

miniature x-ray source

Example: Xoft Inc.

Might be interesting in the field of the Mammosite technique, accelerated partial breast irradiation….

Permanent Implants

Radioactive sources remain in the patient and decay v  Relative short half life v  Low energy (radiation

protection)

Permanent Implant 125I

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 30 60 90 120 150 180

Days

Dos

e R

ate

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

1.000

Tota

l Dos

e

Permanent Implants

e.g., for prostate, brain

these sources should combine a short half life with low energy:

=> patient should be able to continue life as usual

Examples:

I-125 (60 days; 28 keV)

Pd-103 (17 days; 21 keV)

Sources for Permanent Implants:

Requirements for design of seed products

• Visibility

• isotropic dose distribution

• stability in production

• reliability of source delivery, short delivery time

• smaller packaging, customized, take back procedure of remainder of radionuclide material, metal tubes, etc

Visibility of seeds

• X-Ray: the seed needs a marker

• US: hollow, air cavity; surface reflection(?)

• CT: small scattering effects

• MR: -

Cross-Sectional drawings of sources with a Rod, Wire, or Cylinder internal core design; (a) Amersham 6711 OncoSeed, (b) Syncor PharmaSeed, (c) UroMed Symmetra, (d)SourceTech Medical 125Implant, (e) Med-Tec I-Plant, (f) International Brachytherapy, Inc. InterSource125, (g) Best Medical Model 2301 (h) Amersham 6702, (i) UroCor ProstaSeed, (j)Imagyn IsoSTAR, (k) Mentor's IoGold, (l) DraxImage BrachySeed.

Heintz BH, Wallace RE, Hevezi JM. Comparison of I-125 sources used for permanent interstitial implants. Med Phys 2001 Apr;28(4):671-82

Seeds:

Special presentations of seeds

“Rapidstrand®” seed ribbon technique with

the 125I sources connected in a suture

“Isocord®”: comparable technique with the 125I sources connected in a bio-absorbable suture

And there are many more …

New presentation: SourceLink (Bard)

New isotope: Cs-131 (IsoRay)

- Short half-life (9.7 days) may provide radiobiological advantage for some prostate cancers - γ-ray emitter with highest peaks from 29 to 34 keV - Clinical protocol developed in Texas Cancer Center by Prestidge et al. - A Phase II Study on the use of Cs-131 for localized prostatic carcinoma at the New York Prostate Institute

E. Lief, AAPM Brachytherapy School, 2005

New Seeds: Optiseed (IBt)

Courtesy of M. Gaelens, IBt

New Seeds: Optiseed (IBt)

Courtesy of M. Gaelens, IBt

HDR and PDR afterloaders

192Ir stepping source, HDR or PDR

Example of tip of a high dose rate (HDR) source, Ir-192,welded to the end of a drive cable

Ir-192 source HDR afterloader

Advantage of HDR technology

n  One single source (costs) n  Half life 74 days => usable for 3-4

months (costs) n  Afterloader system => radiation

protection n  Stepping source technology allows dose

optimisation => optimisation algorithms n  Short irradiation time (10-15 minutes)

Degrees of freedom in HDR BT

{ t }

{ r }

Dose shaping with HDR and PDR machines

Advanced Optimisation Technology (example :SWIFTTM)

Advanced Optimisation Technology (example :SWIFTTM)

Cartridges and Drive Wire

Compose element

Shielding

seedSelectron®

Activity measurement and

check on seed spacer composition

Developments in seed delivery

No seed manipulation: no human mistakes in preparation and delivery

Calibration of drive wire at start of seed delivery

Check on activity of individual seeds

Check on seed spacer combinations just before insertion

Image guided brachytherapy

• Slow introduction of new imaging modalities into this field:

X-ray, CT (spiral, multislice), MR (open, 0.5T), US (PET)

• It seems to follow external beam technology, at a slower pace

• Guided brachytherapy, why not? Robotic techniques?

MOTIVATION

Apply also to modern

brachytherapy

Apply also to (modern)

brachytherapy

•  ‘Modern Radiotherapy’ seems to be driven by significant developments in EBT

–  3D Conformal Radiotherapy –  Stereotactic Radiotherapy: High Precision –  Intensity Modulated Radiotherapy: Dose Shaping –  Imaging for GTV/PTV, OAR (structure segmentation) –  Computerized treatment plan optimization –  Image guided RT

From Poetter et al

=> Evaluate potential of Brachytherapy based on modern technology

3D Treatment Planning Prostate BT

D 90 V 100 V 150

CTV, Urethra, Rectum

-  CT -  MRI -  US -  PET -  Functional… => the role of ‘imaging’

in RT increases rapidly ➨ Better understanding of anatomy

➨ Better understanding of pathology

➨ More appropriate contouring

Multi modality Imaging

MRI guided single needle implant method

University Medical Center Utrecht, M. Moerland, M. van den Bosch, M. Moman, M. van Vulpen, J. Lagendijk.

University Medical Center Utrecht, M. Moerland, M. van den Bosch, M. Moman, M. van Vulpen, J. Lagendijk.

UROBotics, USA

MRI-Guided Robotic Brachytherapy of the Prostate

BT Dose Calculation: TG43

),()()(

),(),(

.

0,0

θθ

θθ rr

r

rkr Fg

GGSD •••Λ•=

TG-43 Concept •  Calculate (Monte-Carlo) and measure the

dose distribution around a source •  Parameterize TG-43 parameters to fit to the

measurements

TG-43 parameters

(TG-43 Algorithm)-1

Experimental setup

TG-43 Concept •  Calculate (Monte-Carlo) and measure the dose

distribution around a source => GUIDELINES •  Parameterize TG-43 parameters to fit to the

measurements => CONSENSUS DATASETS

TG-43 parameters

TG-43 Algorithm

experimental

patient

Limitations of TG43 algorithm

n  Line source ó cylindrical source n  Homogeneous “water” patient (energy-tissues) n  Full scatter patient (skin dose 15-20% overestimated) n  Transit dose (for afterloaders) n  Intersource effect (6% effect on peripheral dose) n  Applicators n  Shielding

New algorithms

n  Monte Carlo –… n  Varian: BrachyVision Acuros n  Nucletron/Elekta : Collapsed Cone

n  AAPM TG-186: “Model-based Dose Calculation in BT: status and clinical requirements for implementation beyond TG-43”

Training in Brachytherapy

n  As treatment techniques and delivery systems become more complex

n  Need for better formed/trained staff n  ! Few centres specialised in “ high end

BT “ (certainly in Western Europe)

Brachytherapie ó Teletherapie

Investments

€ 300.000 € 2.400.000

(+ € 13.000 / source) (+ maintenance) Workload ++ Workload +++

CONCLUSIONS

Continuous Development in BT

Collaboration at international level eg AAPM / GEC-ESTRO

Brachytherapy continues to merit its place along external beam radiotherapy

Credits: Jack Venselaar, Rien Moerland, Dimos Baltas