Image Guided Image Guided Radiation TherapyRadiation Therapy (IGRT) in prostate (IGRT) in prostate

cancercancer

MªCarmen PujadesHospital Universitario La Fe

Fundación Instituto Valenciano de Oncología (FIVO)

Treatment planification in Treatment planification in radiotherapyradiotherapy

Patient simulation: CT, RM…

Planning treatment -Determination of interest volumes:      GTV, CTV, PTV, OR

-Conformation-beams

Treatment

Differences in target position

Treatment planification in Treatment planification in radiotherapyradiotherapy

POSITION IN THE CT SCAN POSITION IN THE TREATMENT

In the treatment the prostate position changes with respect to the reference position.

Determines the reference position of the prostate throughout the treatment.

Why may the target be Why may the target be elsewhere?elsewhere?

■ Mispositioning (interfraction)Mispositioning (interfraction)

■ Organ motion (intrafraction)Organ motion (intrafraction)

■ Shape change (interfraction)Shape change (interfraction)

Sources of uncertainties

May result in absorbed dose in the volumes of interest and organs at risk that do not correspond to the theoretical dose planned.

Immobilization systemsImmobilization systems

In many cases it is not enough.

Personalized cushionsPersonalized cushions

Vacuum cushions

Image Guided RadiotherapyImage Guided Radiotherapy

■ How can we know the position of the target?

IGRT is the use of the image in the actual IGRT is the use of the image in the actual treatment room as a tool for tracing and treatment room as a tool for tracing and verification of the tumour volume immediately verification of the tumour volume immediately before or during treatment.before or during treatment.

■ What is IGRT?

IGRT

Image Guided RadiotherapyImage Guided Radiotherapy

■Portal Imaging

■Exac Trac X-Ray 6D

■CBCT

■CT Scanner

2D Images Data volumesPortal Imaging CBCT

Exac Trac X-Ray 6DCT Scanner

Ultrasounds (US)

■Ultrasounds

■ IGRT Systems:

What has been done until nowWhat has been done until now in radiotherapy by us? in radiotherapy by us?

Prostate

4 gold seeds implanted transrectally in the prostate guided by US

■ Treatment + verification

■ Oncor Siemens Expression:- aSi portal

imaging system Optivue RID AG9 1000

- MV-CBCT

What has been done until nowWhat has been done until now in radiotherapy by us? in radiotherapy by us?

■ The fusion of the CBCT with the planning CT provides the displacement of the bone estructure.

MV-CBCT Portal Imaging

■ EPID + seeds : provides the displacement of the prostate.

What has been done until nowWhat has been done until now in radiotherapy by us? in radiotherapy by us?

■ EPID with gold seed markersEPID with gold seed markersProstate

Determination of the spatial position of the seeds with a homemade program

1 pair of portal images(Not necessarily orthogonal, separated by more than 30 º)

What has been done until nowWhat has been done until now in radiotherapy by us? in radiotherapy by us?

LEVEL OF ACTION: 3mm

Prostate

OPTIMAL TRANSLATION CONNECT CENTERS OF MASS OF THE SEEDS IN PLANNING AND TREATMENT

Before correction After correction

What has been done until nowWhat has been done until now in radiotherapy by us? in radiotherapy by us?

Migration Prostate volume changes Prostate deformation

Distance between seeds

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

0 5 10 15 20 25 30 35

Fracción

d/d

TC

d12 d13 d14d23 d24 d34

Decrease in distance inter-seed due to organ shrinkage.

What has been done until nowWhat has been done until now in radiotherapy by us? in radiotherapy by us?

mm MAX

LAT 9.7 -0.7 3.3 3.5

CC 18.1 2.1 6.5 4.6

AP 12.4 1.1 3.7 4.7

LATERAL

0246810121416

(cm)

Nº

CRANEO-CAUDAL

0246810121416

(cm)

Nº

ANTERO-POSTERIOR

0

5

10

15

20

(cm)

Nº

■ Statistical analysis :– 9 patients with prostate cancer– 145 inter-fraction displacements

Systematic position error

Standard deviation of the systematic error

Random positioning error

Conclusion

■ Whatever modality you choose to treat the prostate:

The proper treatment requires a system of IGRT that allows very accurate localization.

Thanks!!

“No matter how good is the beam, if the target is not where we thought”.