Varian _ Dynamic Targeting TM Image-Guided Radiation Therapy Scott Johnson, PhD Varian Medical...

Dynamic TargetingTM

Image-Guided Radiation Therapy

Scott Johnson, PhD

Varian Medical Systems

Palo Alto, California

VARIAN medical systems Page 2

Varian IGRT Statistics

As of the end of Dec, Varian had booked 80 orders for the On-Board Imager (OBI)

As to today, 35 installations have been completed

And another dozen installations currently are in progress

As of today, cone-beam CT software has been installed at 7 sites Aarau, Switzerland Karolinska, Sweden MSKCC, New York Emory, Atlanta Stanford, Palo Alto Duke, Durham Henry Ford, Detroit

With an additional installations scheduled in the very near future MD Anderson, Houston


What is IGRT?

IGRT means several things … Use of images for online setup correction, before treatment

begins Position patient on table. Align the patient to lasers. Acquire images

Images usually are kV Images may be an orthogonal pair of radiographs or a volumetric image

(e.g., cone-beam CT) Compare the acquire images to reference images

Analysis may be automated and/or manual Analysis may rely on radiopaque markers, bony anatomy or soft-tissue

anatomy Result of the analysis is data on how to correct the patient position

Move the treatment couch remotely to automatically correct the patient position

Optional: Acquire and analyze another set of images to verify the correction

Begin treatment delivery


Movie of the clinical process


What is IGRT?

Use of images for online setup correction, before treatment begins

What’s new here: Use of kV imaging in the treatment room New image analysis tools for the therapist

Fast, easy to use, integrated into the existing workflow Remote couch control, to speed the process

The result is: Significant improvement in target localization

Reduced likelihood of missing the target An opportunity to reduce CTV-to-PTV margins and thus the

volume of normal tissue irradiated to high dose May reduce the toxicity of RT


What is IGRT?

IGRT also may mean adaptive radiation therapy Tumors, hopefully, respond to treatment and shrink over the course of

therapy

As the surrounding tissues are pulled inward, the result may increase the dose to critical structures

With adaptive RT, goal is to use images to Perform online setup correction of patient position

Acquire a volumetric image (cone beam CT scan)

Automatically detect any changes in the target shape

Automatically adapt the treatment plan to reflect the new target shape

Provide the therapist with important information on how the plan has changed

Deliver the new plan

(It’s kind of like a boost plan, but done online with the patient on the table)

Above process should occur within 15-20 minutes, or less


What is IGRT?

With adaptive radiation therapy, images of the tumor size, shape and location are used to adapt the treatment plan before it is delivered

Critical structure

Critical structure

Target

Prescription isodose

Original treatment plan and anatomy


What is IGRT?


Critical structure

Critical structure

Target


Original treatment plan and new anatomywith tumor shrinkage due to radiation


What is IGRT?


Critical structure

Critical structure

Target


Adapted treatment plan


What is IGRT?


No one is doing this yet! Before it can be done, the following are needed

Ability to acquire CT scans on the treatment table. DONE! Automated image segmentation tools that automatically contour

the patient anatomy New treatment plan analysis tools for the therapist

Including tools that clear show what treatment plan adaptations are needed and what the effect of those changes is

Fast, easy to use software that is well integrated into the existing treatment delivery process

Guidelines on when adapted treatment plans should be reviewed by a physicist or physician

Guidelines on how to QA the adaptive radiation therapy process

Etc


What is IGRT?

IGRT also can be considered to include dose guided radiation therapy Acquire a CT scan of the patient on the treatment table in the

treatment position Deliver the treatment plan Use an EPID to capture transit dose images or capture linac and MLC

log files Use transit dose to back project delivered dose onto CT or use log

files to forward project delivered dose onto CT

The result is a realistic calculation of the dose delivered that day including the impact of bladder and rectal filling, bowel gas, etc

Dose actually emitted by the linacoverlayed onto CT scan of patienton treatment table


What is IGRT?

IGRT also can be considered to include dose guided radiation therapy Now, imagine repeating the above process at each treatment session

and having the ability to morph the results onto each other

Summing the results allows you to visualize the dose actually delivered to the target and critical structures over a series of treatment sessions

With advanced treatment planning tools, you then may choose to adapt the treatment plan mid-stream so that the final, cumulative dose satisfies the physician’s prescription


What is IGRT?

IGRT also can be considered to include dose guided radiation therapy Again, no one is doing this yet, but we are getting close… Before it can be done, the following are needed

Ability to acquire CT scans on the treatment table. DONE! Ability to capture linac and MLC log files or transit dose. DONE! Ability to project beams recorded in log files into CT scans.

DONE! Image and dose morphing tools that allow you to sum the dose to

a volume over several sessions, given that the volume is changing size, shape and location

Fast, easy to use software that is well integrated into the existing treatment delivery process

Guidelines on when to adapt a plan and when that adapted plan should be reviewed by a physicist or physician

Guidelines on how to QA the dose guided radiation therapy process

Etc


Will IGRT replace IMRT?

No, the two are complementary.

IMRT allows the dose to conform tightly to the PTV.

IGRT allows the PTV to shrink to the CTV.

IG-IMRT then allows simultaneously margin-reduction and dose conformation.

Conventional RT

IMRT

IG-IMRT

CTV

PTV

Organ at risk

High dose isodose


Varian IGRT Technology

On-Board Imager accessory

Available as an upgrade to any Clinac installed in 1997 and after


On-Board Imager Hardware

Two robotic arms

kV Xray source

Amorphous silicon imaging panel

OBI workstation

Three modes of operation Radiographic

Online setup correction Bony anatomy or markers

CBCT

Online setup correction Bony or soft tissue anatomy

Visualization of delivered dose

Adaptive radiation therapy

Fluoroscopic

Verification of gated radiation therapy

Fluoro-based tumor tracking (*Future option)

Trilogy and the On-Board Imager


Command Center

Clinac console, 4D Console, OBI workstation, RPM Gating workstation


Robotic arm motion


Robotic arm motion


Robotic arm motion


Robotic arm motion



Orthogonal radiographs for online patient setup correction


Acquisition of a lateral radiograph


Acquisition of an AP radiograph


Sample radiographs

Images courtesy of Karolinska Medial Center


Sample radiographs

Images courtesy of Karolinska Medial Center


On-Board Imager workstation


On-Board Imager workstation


Marker matching using the On-Board Imager


Marker matching using the On-Board Imager



Cone beam CT for online patient setup correction

(and adaptive radiation therapy and dose guided radiation therapy)


Acquisition of a cone beam CT scan














Sample CBCT image

Images courtesy of Duke University Hospital



Controlling for respiratory motion


Respiratory gating

RPM Gating System Infrared camera

External marker block

Gating workstation

Process Place block on patient’s abdomen

Camera monitors block motion

Respiratory waveform shows how the block moves up and down in time

User sets upper and lower thresholds on block motion

Whenever the block comes between the thresholds, the beam is on

Whenever the block moves outside the thresholds, the beam is off

Free-breathing and breath hold protocols are supported, as are gating at inhalation or exhalation or at any other point in the respiratory cycle


Fluoro-based verification of gating

With the On-Board Imager, gated kV radiographs are used to verify patient setup and kV fluoroscopy is used to verify the gated treatment port.







What’s next?


Where we are headed

New software tools for online adaptive radiation therapy and dose guided radiation therapy

Automated segmentation of acquired CBCT scans Treatment planning and plan review tools at the Command Center Fast, automated plan modification tools

New software tools for fluoro-based gating, in which the gating signal is based on the motion of internal anatomy (rather than an external marker block)


Where we are headed

New MLC control system to enable real-time tumor tracking



Why we think it is superior


Varian’s IGRT technology

Compared to Tomotherapy

We use kV photons rather than MV for superior image quality

We use cone-beam CT rather than helical slice-based CT because cone-beam CT images are superior and CBCT is the future

Radiology, in general, is moving toward CBCT

1 slice scanner > 2 slice > 4 slice > 8 slice > 16 slice > …

Because of the exquisite detail, CBCT already has been adopted by Cardiology

We can develop fluoro-based tools to monitor and control for respiratory motion

Tomotherapy will have a difficult time dealing effectively with respiratory motion



Compared to Novalis and CyberKnife

We use a gantry-based system, rather than a room-based system, to have the option of acquiring CBCT scans

Volumetic imaging is not possible with Novalis or CyberKnife



Compared to Synergy

We use robotic arms to position the kV source and kV imager to allow remote control and superior flexibility in imaging geometry

We use high-quality Varian imagers, which have a much higher image acquisition rate

Up to 30 frames per second, compared to 3-5 frames per second for Elekta

Most clinicians feel that a frame rate of at least 12-15 images/second is required for fluoro-based gating


Conclusion

Varian offers the most integrated and comprehensive solution available kV radiographs kV/MV radiographs Gated radiographs Marker-based setup corrections, 2D-2D and 2D-3D CBCT acquisition and analysis Pretreatment verification of gated treatment ports Robotic couch motion IGRT software integrated with the VARiS Vision Eclipse

database

Varian is well-positioned to quickly deliver the next generation of IGRT technology


Thank you

Date post:	18-Dec-2015
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Varian _ Dynamic Targeting TM Image-Guided Radiation Therapy Scott Johnson, PhD Varian Medical...

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