Use of pre treatment protocols

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Use of pre treatment protocols

  1. 1. USE OF PRE-TREATMENTIMAGING PROTOCOLS FORMOTION ESTIMATIONBartosz Bak MSc Greater Poland Cancer Center
  2. 2. Introduction With the introduction of IMRT and SBRT we have reached a point where the radiation dose can be shaped to the target volume with steep dose gradients to surrouding normal tissues. These new treatment techniques introduce an enormous inherent risk, to quote J. Rosenman:“We are at increased risk of missing very precisely” B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  3. 3. Introduction Increasing precision and accuracy in radiotherapy PLANNING and radiation DELIVERY will lead to reduced toxicity with the potential for dose escalation and improved tumour control B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  4. 4. Accuracy... for safe daily treatment is achieved by:  ensuring reliable and reproducible patientimmobilization, planning and treatment correlation, pre-treatment quality assurance using daily imaging(and possibly) a method of accounting for tumour motion duringtreatment B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  5. 5. B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.plTUMOUR LOCALISATION – DIFFERENT PROBLEMS USE OF PRE-TREATMENT IMAGING PROTOCOLS FOR MOTION ESTIMATION
  6. 6. Head and Neck  Small or negligible intra-treatment organ movement  Main problem are changes in location, form and size of disease and normal anatomy:   Tumour shrinkage, nodal regression   Oedema   Changes in the H&N posture, weight loss   Alterations in normal glands and mucosa  Leading to significant dose changes in the target and OARs   Tumor can shrink volumetrically by up to 90%!   Parotid glands can involute and shift medially (towards high-dose coverage in the oropharynx) by up to a centimeter during a treatment course! B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  7. 7. Chest  Main problem:   Breathing motion  Organ displacements during normal breathing may occur in all directions of about 5,5-20mm  Lung target motion can amount to 3cm when no movement reduction methods are used B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  8. 8. Chest  Movement reduction methods:   Active breath control (ABC) device   Cheung et al: the average (SD) displacement of GTV centres was 0.3 mm (1.8 mm), 1.2 mm (2.3 mm), and 1.1 mm (3.5 mm) in LR, AP and CC   Voluntary breath-hold methods using spirometer-based monitoring   Kimura et al: 1.3 1.3)mm, 1.4(1.8)mm, 2.1(1.6)mm and 3.3(2.2)mm in CC, LR and AP   DIBH (Deep Inspiratory Breath Hold) technique   Mah et al: the inferred displacement of the centroid GTV was 0.2(+/- 1.4mm) (mean and SD)   Abdominal compression B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  9. 9. Chest  Movement compensation:   Free breathing gating technique: Temporal tracking by detecting the breathing phase and gating the beam on and off Synchronously with the breathing cycle.   Tumour tracking:   By detecting tumour posision and shifting the alignment of the beam synchronously. B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  10. 10. Pelvis  Main problem:   Inter- and Intra-fraction prostate motion   Shimizu et al.: shifts < 3mm (81%), < 5mm (98%);   Nederveen et al.: greatest motion in CC and AP 2-3 mm; Fiducial makers   Madsen et al.: mean prostate motion < 2mm   Kron et al.: intrafraction prostate displacement - after a relatively short interval of 3 min, the vector displacement is likely to exceed 1.5 mm BUT Even in relatively short times there is a significant probability that the prostate has moved more than 3 mm. B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl Kron et al
  11. 11. Pelvis  Prostate motion is a result due to:   Different fillings of hollow organs (rectum and bladder)   Breathing   Pelvic muscle constriction and relaxation  Different protocols of rectal and bladder preparation intend to limit prostate motion   Ghilezan et al.: shifts >3mm in full rectum group, only small shifts after 20minutes in empty rectum group (cine MRI) B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  12. 12. B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.plTHE DIAGNOSTIC LEVEL - TO DEFINE TARGET BETTER USE OF PRE-TREATMENT IMAGING PROTOCOLS FOR MOTION ESTIMATION
  13. 13. To define target betterThe identification of the target volume is potentially the largest source of systematic errorMultimodality imaging and the ability to co-registerimages have the potential to improve tumour volume identification B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  14. 14. Imaging modalities   For all patient planning CT is a golden standard   CT can provide accurate information on size, position and density of the tumour and other anatomy in 3DMoreover, the HUs give informationon electron density distribution in the patient, readily useful forcalculation of the absorbed dose in the patient. B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl Korreman et al.;
  15. 15. Improvements of imaging modalities  Morphological:   Fast CT (every tumour site)   MRI (H&N, prostate)  Functional:   MRS – Magnetic Resonance Spectroscopy (H&N, prostate)   PET/CT (H&N, lung)  Reduction of respiratory motion   4D CT:   respiratory-gated CT (RGCT)   4D PET/CT: one of the most recent technological progresses for accurate imaging of tumors, particularly those located in the thorax and in the upper abdomen   respiratory-correlated dynamic PET (RCDPET) B.Bak MSc,respiratory-gated PET -(RGPET)   Greater Poland Cancer Center bartosz.bak@wco.pl
  16. 16. B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl THE DELIVERY LEVELUSE OF PRE-TREATMENT IMAGING PROTOCOLS FOR MOTION ESTIMATION
  17. 17. Image Guided Radiation Therapy  IGRT can be performed either statically or dynamically (in real time)  IGRT concept :   Allows for tighter margins around the tumour Minimizing the volume healthy tissue exposed to the treatment beam   reducing geometrical uncertainly by evaluating the patient geometry at treatment   Altering the patient position   Adapting the treatment plan with respect to anatomical changes that occur during the RT  Uncertainties:   Technical precision provided by IGRT also includes a potential danger as to reducing margins to levels that are inadequate B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  18. 18. What do we have?  Radiation therapy evolved from 2D to 3D in the treatment- planning process, in the same way a similar evolution can be observed in IGRT.  DRR and EPI for planning and verification have replaced radiographic films.  Volumetric imaging techniques nowadays provide the soft- tissues contrast required for daily pre-treatment positioning, providing online information concerning OAR as well as tumours and identifying anatomical changes during the course of RT B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  19. 19. What do we have? Siemens CT-on- Elekta kv CBCT Varian kv CBCT rails (Synergy) (OBI) Siemens MV TomoTherapy B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl CBCT MVCT
  20. 20. What do we have?  EPID  kV  CT on rails  CBCT  kV  MV  MVCT B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  21. 21. EPID - Electronic Portal Imaging Device  Established as a gold standard for on-line verification of patient’s set-up  Portal images from 2 or more directions aquired immediately before the radiation delivery and compared to reference images  Uses bony landmarks for the reference   Adequate for H&N   Requires gold markers implanted in or near the tumour for other sites B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  22. 22. EPID - Electronic Portal Imaging Device  Technique: MV treatment beam  Time: 10 min  Dose: 2 – 8 cGy  Advantages:   Management of interfractional geometric uncertainties (reduction of set-up margin)   Moderate cost, Electronic data, Real-time display, Cine mode  Limitations:   2D, Large dose, Low contrast   Requires surrogates for the target volume (bony landmarks or implanted radio-opaque fiducial markers) B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  23. 23. kV  In-room kV imaging replaces MV portal imaging for set-up  kV images have better resolution and contrast than MV (allowing for more accurate rigid registration to determine the patient’s pose correction)  Require independent x-ray sources and detectors (uncertainty between the imaging and beam isocenters) B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  24. 24. kV  Technique: kV x-rays  Time: <5 min  Dose: < 1 cGy  Advantages:   Management of interfractional geometric uncertainties (reduction of set-up margin)   Electronic data, real-time display, Excellent contrast, Remote couch shift, Fluoroscopic mode (motion assesment), Very quick, very low dose  Limitations:   Expensive, 2D, No treatment port, No soft tissue information B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  25. 25. 3D KV Imaging The Synergy system from Elekta Inc (Norcross, Varian Trilogy with On-Board Imager features Elekta Axesse™ unique capabilities include Ga) also features a kV imaging system retractable arms with which to image the true 3D imaging which gives target and deployed with retractable arms to image the patient using a cone beam of kV energy. critical structure visualization at the time of patient in the treatment position. treatment and enables 6D remote robotic automatic position corrections. BrainLab ExacTrack CyberKnife B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  26. 26. CT on rails  Technique: kV x-rays  Time: 10 – 15 min  Dose: 5 cGy  Advantages:   Electronic data, real-time display, Excellent contrast and image quality, Remote couch shift, 3D images, Volume information  Limitations:   Expensive, large couch motion between CT and treatment   cannot be used for the detection of intra-fractional patient or organ motion   This type of CT requires a lot of space in the treatment room B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  27. 27. CBCT Elekta Synergy Varian Trilogy B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  28. 28. KV CBCT  Technique: kV x-rays  Time: 10 – 15 min  Dose: 3 – 11 cGy  Advantages:   Management of interfractional geometric uncertainties (reduction of set-up margin)   Electronic data, Real-time display, Excellent contrast, Remote couch shift, 3D images, Volume information  Limitations:   Expensive, Longer aquisition, Collision clearance, No treatment port B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  29. 29. MV CBCT  Technique: MV x-rays   MV beam is used for treatment and imaging so Imaging dose is easily incorporated into the dose calculation algorithm  Time: 10 – 15 min  Dose: 2 cGy  Advantages:   Management of interfractional geometric uncertainties (reduction of set-up margin)   Electronic data, Real-time display, Remote couch shift, 3D images, Volume information   MV-based CT images can be used to complement or replace diagnostic KV CT images when high density objects introduce severe artifacts  Limitations: B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl   Expensive, Longer aquisition, No treatment port
  30. 30. MVCT - Tomotherapy B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  31. 31. MVCT  Fusion of a MV linac with a helical CT scanner  Allows DAILY patient set-up verification and repositioning  Provides less soft tissue contrast but suffers less from beam hardening and the artifacts induced by highly attenuating high-Z materials  Technique: MV treatment beam  Time: 5 – 10 min  Dose: 1 – 3 cGy, enables daily veryfication B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  32. 32.   Advantages:   Management of interfractional geometric uncertainties (reduction of set-up margin)   Estimation the tumour response and adaptation the treatment plan during the same course of radiotherapy (ART)   Automated target localization and positioning prior to the treatment   The set up correction can be implemented by moving the patient, or by modifying the IMRT delivery to account for the patient’s actual geometric offset   Electronic data, Real-time display, Excellent contrast – less scatter than CBCT, 3D images, Volume information, Dose verification  Limitations:   Expensive, Time consuming, not suitable for large respiratory motion (Chest) B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  33. 33. B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.plIMAGING PROTOCOLSUSE OF PRE-TREATMENT IMAGING PROTOCOLS FOR MOTION ESTIMATION
  34. 34. Imaging protocols NAL or NAL3 NAL5 WeeklyNO ACTION LEVEL eNAL FFFs ALT B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  35. 35. NAL/NAL3 (No Action Level) Protocol  Based on H.C. De Boer  Imaging is done on the first three treatment days  No positional correction is applied for the first three fractions when imaging data is being collected  The targets location and set-up optimization shifts are averaged over these 3 days, and all subsequent set-ups are adjusted for those shifts.  No additional image-guidance studies are obtained B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  36. 36. NAL5 Protocol  NAL5 is similar to the NAL (NAL3) protocol except the first five fractions are imaged instead of the first three  No positional correction is applied for the first 5 fractions B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  37. 37. Weekly  corresponds to once a week imaging (every 5th fx)  Shifts derived from each imaging instance are applied to the subsequent 4 fractions  Weekly set-ups are typically only corrected for subsequent fractions when a defined threshold (5mm) of set-up uncertainty is exceeded  This reflects typical clinical practice in which imaging is acquired on the first day of treatment, and then once weekly B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  38. 38. eNAL imaging protocol   eNAL is a combination of the NAL3 and Weekly protocol   With this protocol, imaging is done for the first three days, followed by weekly imaging   If the patient set-up during weekly imaging would be within 5 mm of the simulation set-up, no further correction would be made   Set-up corrections larger than 5 mm would be averaged with the shifts of the first 3 fractions, and constitute a new baseline correction for all subsequent fractions B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  39. 39. First Five Fractions (FFFs) - protocol   Pre-treatment MVCTs are acquired during the patient’s first five fractions allowing for patient set-up verification and correction on those particular days.   This protocol closely resembles the previously described NAL protocol with five imaged fractions described byDeBoer et al.,   Although MVCT imaging provides more anatomical information than electronic portal imaging B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  40. 40. Alternate week (ALT)- protocol   Pre-treatment MVCTs are acquired for fractions 1 to 5 allowing for patient setup correction.   deviations are then averaged and automatically corrected for during the subsequent 5 fractions (fraction 6–10).   MVCTs are re-performed during the third week of treatment (fractions 11–15), and averaged and corrected for during the subsequent five fractions (fractions 16–20).   The process is repeated until the end of the patient’s treatment course B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  41. 41. MVCTs protocol: FFFs vs. ALT  Conclussions:  The ALT protocol resulted in slightly smaller residual deviations, particularly in the a–p direction, compared to the FFF protocol. B.Bak MSc, Greater Poland Cancer Center - bartosz.bak@wco.pl
  42. 42. Thank YouUSE OF PRE-TREATMENT IMAGING PROTOCOLS FOR MOTION ESTIMATION

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