Image Guided Radiation Therapy IGRT in prostate cancer

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 Differences in target position Treatment

Treatment planification in radiotherapy POSITION IN THE CT SCAN Determines the reference position of the prostate throughout the treatment. POSITION IN THE TREATMENT In the treatment the prostate position changes with respect to the reference position.

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 theoretical dose planned.

Immobilization systems In many cases it is not enough. Vacuum cushions Personalized cushions

Image Guided Radiotherapy ■ How can we know the position of the target? IGRT ■ What is IGRT? 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.

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

What has been done until now in radiotherapy by us? Prostate ■ Treatment + verification ■ Oncor Siemens Expression: - a. Si portal imaging system Optivue RID AG 9 1000 - MV-CBCT 4 gold seeds implanted transrectally in the prostate guided by US

What has been done until now in radiotherapy by us? MV-CBCT ■ The fusion of the CBCT with the planning CT provides the displacement of the bone estructure. Portal Imaging ■ EPID + seeds : provides the displacement of the prostate.

What has been done until now in radiotherapy by us? Prostate ■ EPID with gold seed markers 1 pair of portal images (Not necessarily orthogonal, separated by more than 30 º) Determination of the spatial position of the seeds with a homemade program

What has been done until now in radiotherapy by us? Prostate Before correction After correction OPTIMAL TRANSLATION CONNECT CENTERS OF MASS OF THE SEEDS IN PLANNING AND TREATMENT LEVEL OF ACTION: 3 mm

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

What has been done until now in radiotherapy by us? ■ Statistical analysis : – 9 patients with prostate cancer – 145 inter-fraction displacements Systematic position error 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 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”.