Image Guided Radiation Therapy (IGRT) in prostate cancer MªCarmen Pujades Hospital Universitario La Fe Fundación Instituto Valenciano de Oncología (FIVO)

Treatment planification in radiotherapy Patient simulation: CT, RM… Planning treatment -Determination of interest volumes: GTV, CTV, PTV, OR -Conformation-beams Treatment Differences in target position

Treatment planification in radiotherapy 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 elsewhere? ■Mispositioning (interfraction) ■Organ motion (intrafraction) ■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 systems In many cases it is not enough. Personalized cushions Vacuum cushions

Image Guided Radiotherapy ■How can we know the position of the target? IGRT is the use of the image in the actual treatment room as a tool for tracing and verification of the tumour volume immediately before or during treatment. ■What is IGRT? IGRT

Image Guided Radiotherapy ■Portal Imaging ■Exac Trac X-Ray 6D ■CBCT ■CT Scanner 2D ImagesData volumes Portal ImagingCBCT Exac Trac X-Ray 6D CT Scanner Ultrasounds (US) ■Ultrasounds ■IGRT Systems:

What has been done until now 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 AG MV-CBCT

What has been done until now 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 now in radiotherapy by us? ■EPID with gold seed markers Prostate 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 now in radiotherapy by us? LEVEL OF ACTION: 3mm Prostate OPTIMAL TRANSLATION CONNECT CENTERS OF MASS OF THE SEEDS IN PLANNING AND TREATMENT Before correctionAfter correction

What has been done until now in radiotherapy by us?  Migration  Prostate volume changes  Prostate deformation Distance between seeds Decrease in distance inter-seed due to organ shrinkage.

What has been done until now in radiotherapy by us? mmMAX  LAT CC AP ■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”.