prostate igrt with setup intelligence 4sharing

Implementing an IGRT correction

strategy using IMPAC Setup

Assist/Intelligence IMPAC Mid-Atlantic Regional Users Meeting

May 30, 2008

Carnell J Hampton, Ph.D.

Clinical Physics SectionDepartment of Radiation Oncology

W A K E F O R E S T U N I V E R S I T Y S C H O O L O F M E D I C I N E CJ Hampton

Learning Objectives

� After completing this activity, the learner will be able to:

� Describe the elements of an IGRT on-line correction strategy and discuss how members of the radiation oncology team play a role in the successful implementation of such a strategy

� Understand and use tools available within MOSAIQ to establish an IGRT correction strategy

� Discuss challenges and potential pitfalls of the WFUBMC experience implementing a clinical implanted-marker prostate IGRT correction strategy including quality assurance, chart documentation and associated IGRT billing issues


Conformal Radiotherapy Planning

� Goal: Optimize the therapeutic ratio by shaping delivery of high-dose radiation to the target volume while sparing surrounding normal structures


Geometric Uncertainty/Errors

� Knowledge of geometric uncertainties and their effect on accurate RT are well documented

� Patient specific geometric uncertainty has implications for insufficient coverage of target or overdosage of normal tissues

� Uncertainty can be classified into groups defined by the relative relationship between the uncertainty and the patient and treatment coordinate systems

� Setup error� Separation/table sag� Voluntary movement during Tx� Respiration� Rectum/bladder filling� Peristalsis � Cardiac motion� Swallowing


Relative Uncertainty in RT

� Advanced imaging, especially temporal imaging, has aided the quantification of uncertainty for specific disease sites.

� Both simulations and clinical patient studies have begun to document the extent to which geometric uncertainty impacts therapy.

0-40 mm4-6 mmUp to 50 mmLung

3-4 mm3-4 mm3-4 mmProstate

6 mm4-6 mm6-42 mmBreast

Organ MotionSetupDelineationSite

Langen 2006


Geometric UncertaintiesICRU 62 Terminology

CTV=>PTV Includes:

� IM – Internal Margin variation in shape and position of CTV within patient

� SM – Setup Margin uncertainty in patient position and beam alignment

No explicit margin for target delineation, which is a function of inter-observer variability and imaging modality

PTV

CTV

GTV

IM

SM


What is IGRT?

� “Real-time” imaging consisting of:1. 3D volumetrics of soft tissues

2. Efficient acquisition and comparison of the 3D volumetrics, and

3. An efficacious process for clinically meaningful intervention

Ling et al, Radiotherapy and Oncology (2006)


� IGRT is useful when:� conformality is critical,

� dose escalation has been shown to provide a benefit,

� uncertainty due to tumor motion is a concern,

� changes in tumor or normal structures during the course of therapy require adaptation of the original treatment plan.

� “IGRT is a quality assurance tool for highly conformal treatment”


IGRT Process: On-line Correction

Initial Setup Analysis Action

TreatmentImaging Imaging

Modified from Yin et al, Med. Phys. Pub.

Imaging


Stereoscopic IGRT for On-line

Localization/Correction� Derived 3D localization through stereoscopicimaging

� Automated or semi-automated methods for comparing reference/treatment-time images

� Image registration or matching based on soft tissue, bony anatomy, implanted markers (IM)and clips, user-generated contours


Gold markers are placed prior to CT treatment simulation

A treatment plan is created based on the simulation CT scan. The tumor is precisely targeted for radiation therapy.

Immobilization is created for each patient. A CT scan is acquired for treatment planning and measurements recorded for later setup.

A computer program is used to calculate where the target is on x-ray images and guides the setup of the patient back to the parameters of the treatment plan.

Once the patient is in the correct position, radiation is delivered.

1.1.

2.2.

3.3.

4.4.

5.5.


IGRT Workflow: Therapists’/Dosimetrists’ Role

Pre-Therapy

� Identification of matching target (i.e. IM, contour) used for on-line correction on planning CT or MR

Daily Therapy

� Performing patient setup, image registration, and daily on-line correction

� Quality assurance monitoring of image registration


IGRT Workflow: Physicians’ role

� Patient selection for IGRT

� Implantation of fiducial markers

� Review of image registration results, daily imaging

� Approval of daily images, recommendations to improve patient localization

� Trend analysis of patients translations over the course of therapy


IGRT Workflow: Physicists’ Role

� Acceptance testing and commissioning of image registration software� Determination of residual error

� Investigating patterns of failure

� Creating guidance documentation

� Collaborating with M.D. to determine shift action levels

� Trend analysis of IGRT data

� Clinical workflow analysis

� Periodic QA


Why Prostate IGRT?

�� Known and unknown Known and unknown knownsknownseffect prostate RTeffect prostate RT

�� IGRT helps address some IGRT helps address some known known knownsknowns

� Elimination of systematic errors in dose delivery to the prostate will probably have a positive impact on improving the outcome of therapy (Crevosier, IJROBP, 2005).

�� Conformal dose delivery to Conformal dose delivery to the target makes dose the target makes dose escalation feasibleescalation feasible

Wu et al, IJROBP, 2006


Prostate IGRT Comparison: Setup Accuracy

Figure 1 Comparison of residual errors for different image-guidedcorrection techniques in prostate, in the left-right (LR), anteriorposterior, and superior-inferior directions.

GS Mageras et al, Seminars in Rad. Onc., 2007

~2 mm


Implanted Marker IGRT (IM-IGRT):

Required Resources

Implantable Markers…

MV/kV Source & Digital Image Receptor

Localization Software

…& personnel skilled at implantation


MD Workroom

/Office

IM-IGRT: Optional Resources

Treatment Console

Remote review tools

Trending/Data analysis tools


IM-IGRT

� Direct or indirect imaging of the prostate alone with human detection of setup errors is insufficient to achieve high precision

� Fiducial markers implanted via transrectal ultrasound create a permanent implanted coordinate system.


IM-IGRT

� 3-5 markers typically implanted within prostate

� Apex, mid-gland lateral, base

� Markers can be localized with treatment beam (MV) using orthogonal portal images or kV X-ray source/detector

3 mm

0.8 mm


Implanted Marker (IM) IGRT

� 3D localization provided by the imaging of markers on orthogonal portal images and the reconstruction of their position within the treatment coordinate system

� Least-squares minimization technique used to reconstruct marker position in 3D

� The reference frame defined by CT in treatment planning can be transformed in 3D to the treatment coordinate system and registered with the location of the markers determined from the orthogonal portal images

� The registration gives the translations needed to align the isocenter determined from the orthogonal images to the isocenter defined in treatment planning


Limitations of IM-IGRT (Known Unknowns)

� IM-IGRT uses fiducials as surrogates for tumor position

� IM-IGRT methods generally account for uncertainties resulting from interfraction rigid organ motion and setup error

� Margins needed to account for unaccounted for uncertainties such as:

� Deformation and rotation of the prostate caused by intrafraction organ motion (eg. Rectal and bladder filling, migration of intestinal gas)

� Uncertainty in target/normal structure delineation


Sources of Uncertainty (Known Knowns)

� Patient Localization (1-2mm)� Inaccuracies in the imaging and patient-support systems

� Marker Localization (1.5mm) 1

� Finite marker size

� Calculated fit of rigid body transformation

� Image quality limitations

� Marker Migration (1-2mm) 1,2

1Pouliot, IJROBP 20032Poggi, IJROBP 2003

PTV

CTV

GTV

IM

SM


Establishing Action Levels

� Using purely geometric evaluations, action levels can be established considering the local planning margins and estimates of the known uncertainties.

� An action level can be considered reflecting the tradeoff between effort to correct a patient’s position and the desired precision level for treatment.


Establishing Action Levels

� Planning margins* + uncertainty

� Ex:

� If the shift is <= 3mm, no couch move necessary

� If the shift is >3mm but <=8mm, move couch as directed. No verification image needed.

� If the shift is > 8mm but <=15 mm, move couch as directed. Acquire verification films. Repeat localization as above.

� If the shift is >15mm. Notify physics/physician.

* CTV-to-PTV = prostate + 7mm/5mm posterior; IMRT t reatment planning


IM-IGRT using MOSAIQ

� Setup Intelligence

� Modules for image registration and fusion

� Point registration

� Curve registration

� Manual registration

� Method for implementing couch offsets for on-line correction

� Online and offline quantitative analysis tools

� Support for third-party positioning software


Image Registration Definitions and “Rules”

� 2D image registration – registration of a portal/verification image and reference image (DRR) pair resulting in the calculation of a 2D isocenter shift

� Available only at cardinal angles (0, 90, 180, 270)

� No verification images with couch rotations

� The common dimension can be derived (i.e. the sup/inf dimension for independent AP and Lat image reconstruction)


R. Lat


AP


Image Registration Definitions and “Rules”

� Stereoscopic image registration –registration of 2 sets of portal/verification image and reference image (DRR) pairs resulting in the calculation of a 3D isocenter shift� the image must be a portal image associated with the same site� the angle between incident beams must be greater than 30 and less than 150 degrees to that of the review image

� the study date and time must be within 10 minutes of the review image

� the image must be taken on the same treatment machine as the review image

� the image must have square pixels� the image cannot be approved, rejected, or voided.


Preparing for IM-IGRT Treatment

� Departmental setup� Patient or Isocenter Orientation

� Site Setup� How to get there: from the Diagnoses and Interventions window, click Site Setup or from the Treatment Field Definition dialog box Options menu, click Site Setup.

� Patient orientation must be set


Registration Editor

� Set isocenter, scale

� Identify markers, curves, landmarks for future registration

� Landmarks locked after recording a registration


Point Registration

Image registration can be initiated from the treatment delivery table window.


Point Registration

Select the daily Images


Point Registration

Initiate image registration by clicking the Register button.


The other image of the stereoscopic pair is selected and the image registration window opens.


#1

#2

#3

For each verification image, markers are identified corresponding to the reference images


Graphically review the accuracy of the automatic image registration.


The calculated offsets are displayed in the image review window. Image registration is complete!


Localization Trend Review


Offset References

� Session (Localization) Offsets

� Setup error data collected during the treatment session

� Third Party Offsets

� Setup error data calculated using other software can be manually added to a patient’s treatment record

� Prescribed Offsets

� The systematic setup error can be determined from session offsets


On-line Correction

� Offset Couch Calculator

� Calculates new couch targets relative to the current couch location


Shifting the Patient

Setup Intelligence calculates and displays the new couch coordinates based on the image registration offsets.


Initial Setup Imaging Analysis Action

TreatmentImaging Imaging

Modified from Yin et al, Med. Phys. Pub.


IM-IGRT: WFU Experience

� WFUBMC IM-IGRT program initiated in 2006

� 50 patients treated with IM-IGRT (2006-present)

� Hardware/Software Configuration

� 4 Varian EX Linacs with EPIDs

� ADAC Pinnacle TPS

� PortalVision

� ACCULOC markers/ISOLOC localization software (2 licenses)

� Multi-Access/MOSAIQ upgrade to Setup Assist/Intelligence in April 2008.


Setup Intelligence: Advantages over Acculoc

� Accessibility of image registration to multiple linacs without the need for multiple software licenses

� Fewer steps needed to perform registration and on-line correction

� No manual export of portal images

� No manual entry of current table coordinates

� No need to print shift information to take into the treatment room

� Consolidation of daily shift information within the EMR for better documentation


Setup Intelligence: Advantages over Acculoc

� Visualization of the reference image alongside the portal image aids in the identification of fiducial markers

� The capacity to perform and review image registrations remotely

� The ability to use fewer than 3 markers for image registration� Useful when a “bad” marker placement of migrated marker makes the use of 3 markers impossible


Stereoscopic Localization Challenges

Marker Migration

� ~10% patients impacted by marker migration since 2006

� Measures of registration error (FRE, mean error) should be monitored frequently

Isocenter

#1

#2

#3

???

#2

#1

#3



Obeying the “rules”

� The verification images must have been acquired within 10 minutes of each other.

� 10 minute time interval for image registration starting from acquisition of 1st image

� Beware of incorrect time-stamped images!



Marker Imaging

� Imaging with the graticule in place can obscure implanted markers

� MOSAIQ can perform portal image scaling manually or automatically using field edge matching


Quality Assurance

� Acceptance of image registration software:

� End-to-end test of � CT image acquisition

� TPS handling

� Portal image acquisition,

� Import/export handling,

� Marker localization and shift calculation,

� Couch translation


IGRT Implementation and QA

� Advanced technologies require new paradigms, training, QA procedures

� Therapist procedures

� Patient shift action levels

� Physician approval protocol/documentation

� Physics QA procedure

� Longer patient treatment slots (?)


Patient Shift Action Levels

� If the shift is <= 3mm, no couch move necessary

� If the shift is >3mm but <=8mm, move couch as directed. No verification image needed.

� If the shift is > 8mm but <=15 mm, move couch as directed. Acquire verification films. Repeat localization as above.

� If the shift is >15mm. Notify physics/physician.

* CTV-to-PTV = prostate + 7mm/5mm posterior; IMRT t reatment planning


IM-IGRT Imaging Dose: Modality Comparison

� Ex. Pelvic RT

Dose estimated for 30 fraction w/at least once daily imaging

0.7 Gy*0.75 cGy2.1 Gy

kV CBCT (full rotation, 120 kVp,

660mAs)

kV portal imaging (orthogonal ports, 120 kVp, 2 mAs/field)

MV portal imaging (orthogonal ports,

4MU per)

* Twice a day imaging would result in accumulated d ose > 1Gy

Med. Phys. 33, (6), June 2006


IGRT Billing

� Stereoscopic X-ray Guidance: CPT 77421� Images fused and registered

� Customized software used to calculate shifts

� Shifts made

� Professional and technical component

� MD work has to be documented

� Documentation and Billing of IGRT� David Beyer – ASTRO IGRT Symposium 2008

� http://www.astro.org/meetings/UpcomingMeetings/IGRTSymposium/ScientificProgram/documents/BeyerD.pdf


Localization Trend Review

Documentation of On-line Correction


Image Review/Approval

Daily Patient Offsets

Image Review/Approval

“OK to treat after shift as calculated by localizat ion software.”



E-chart Notes

“OK to treat after shift as calculated by localizat ion software.”



Documenting Third-Party Offsets

ACCULOC Localization Third-Party Offset


Summary

� IM-IGRT helps reduce interfraction and setup errors to ~2 mm, providing the quality assurance needed for IMRT and dose escalation

� An IM-IGRT protocol in combination with appropriate margins provides improved dosimetric accuracy in prostate RT over uncorrected protocols

� Setup Assist/Intelligence provides a practical and accurate means of performing on-line setup correction


SupportPlus Resources

� Documentation/Videos

� Image Registration I

� Image Registration II

� Setup Intelligence

� Top 10 Radoc Support Questions


Special Special Special Special

ThanksThanksThanksThanks

Robin McCaw – Elekta/IMPAC

NCBH Therapists & Dosimetrists

Phillip Smith

prostate igrt with setup intelligence 4sharing

Documents

e f o r e s t u n

v e r s i t y s c h

patient setup

d localization

patient position

d volumetrics of soft

treatment planning

radiation therapy