4dct with optical tracking systems

2.10.2009 La TC - 4D con sistemi di tracking ottico di superficie - G.Guidi, L.Binotti, et.al. 1

LA TC - 4D CON SISTEMIDI TRACKING OTTICO DI

SUPERFICIE

G.Guidi, L.Binotti, L.Morini, E.Cenacchi, T.CostiMedical Physics Dpt.

M.Amadori, P.Antognoni, M.Parmiggiani, P.Giacobazzi, G.Tolento, F.Bertoni

U.O. Radiation Oncology

Azienda Ospedaliero - Universitaria di Modena - Policlinico

Gabriele GuidiMedical Physics Dpt.Az.Ospedaliero-Universitaria di ModenaEmail: [email protected]: +39 059 422 5699 – ext. 4270

mailto:[email protected]


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4DCT AND GATING/TRACKING DEVICES(TOSHIBA + VISION RT)

Advantages:4DCT Exams (10 CT Dataset – 0-100% Breathing Phases): Very Fast (few minutes) – Retrospective ModeRange Slice thickness for our RT: 0.5 - 3 mm (5mm used for Cranio Spinal Irradiation and TBI)VisionRT detect capability: 1mm of the couch movement (VisionRT can appreciate the ramp up of the couch during the CT scan)Issues:4DCT Images Reconstruction (>1000 Images – 10 CT Datasets – 5/6 Hours of reconstruction)Thickness 0.5mm could be useful for Radiosurgery but few dose problem must be considered during the planning calculationTroubles and investigation:Mismatch image reconstruction due to the couch ramp-up and the breathing signal (Sinogramma Editing in develop by Toshiba)


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HELICAL PITCH AND COUCH VELOCITY (RAMP EFFECT)

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Ram

p (m

m)

Ramp vs. Scan Dimension(Breathing 15_4)

Ramp Scan Dimension

CT

Ramp (Couch Acceleration)

Scan Dimension(Constant Velocity)

May be in some other CT the ramp is inside the scan packet and you could not be able to see the effect of the ramp up during the image reconstruction or have “invisible” effect on the

images...Why do I have a different velocity between VisionRT and Toshiba?

VisionRT Couch Velocity (mm/sec) vs. Breathing

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11_5,45 12_5 13_4,61 14_4,28 15_4

Breathing

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Pitc

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Thikness 0.5mm Thikness 1mm Thikness 2mm

Helical Pitch vs. Breathing

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11_5,45 12_5 13_4,61 14_4,28 15_4

Breathing

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ical

Pitc

h (H

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Thikness 0.5mm Thikness 1mm Thikness 2mm


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PROCESS FOR BREATHING ACQUISITION AND MONITORING

Shift Point of Monitoring vs. Breathing

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11_5,45 12_5 13_4,61 14_4,28 15_4Breathing

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ng

Shift

(m

m)

Thickness 0,5mm Thickness 1,0mm Thickness 2,0mm

Ramp-up vs. Helical Pitch

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1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9

HP

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p (

mm

)

Thickness 0.5mm Thickness 1mm Thickness 2mm

Common Helical Pitch(Tracking Area)

Patient BreathingAcquisition by VisionRT

Detect the optimalHelical Pitch by Toshiba

Define the Monitoring & Respiratory

Point using VisionRT

Send the signalto Toshiba

Run thescan acquisition

Follow the movementof the Monitoring point

during the scanby VisionRT

Monitoring

Respiratory

Critical Issues• 0.5 mm thickness -> Impossible to acquire long volume• 1 mm thickness -> Step into the typical area of the breathing

acquisition• 2 mm thickness -> deformation artifact of the small structures

durin the reconstruction• HP with 1 decimal ->Bad calculation of the monitoring shift by

VisionRT


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RESPIRATORY SIGNAL REPEATABLE (PHANTOM TESTS)

Respiratory signal seems to be perfect and repeatable


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TOSHIBA HELICAL PITCH BIAS .... VISIONRT MONITORING BIAS (PATIENTS)

Exams Setup Parameters: one decimals Internal Machine Parameters: two decimals

Shift Point of Monitoring vs. Breathing

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Breathing

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ift

(mm

)

Thickness 0,5mm Thickness 1,0mm Thickness 2,0mmMonitoring Point CalculationVisionRT Couch Velocity= Thickness*HP/Rot Time

One decimal or two decimal could have a big effect on the monitoring point determination


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VISIONRT VS. TOSHIBA BREATHING SIGNAL RAW DATA

Breathing Raw Data(VisionRT vs. Toshiba)

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Vision RT Toshiba Inferior Threshold (2500ms) Superior Threshold (6500ms)

Breathing Raw Data(VisionRT vs. Toshiba)

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Vision RT Toshiba Inferior Threshold (2500ms) Superior Threshold (6500ms)

Cough: rejected by the reconstruction

Mean respiration time

Which is the impact of the respiration time on the image reconstructions?

...I don’t know at the moment....


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TOSHIBA EDIT DATA TOOLS ... THRESHOLD EFFECTS

Raw data Post Process data

Resample with different breathing Threshold

Spike adjustmentsPerfect Breathing (post-processing)Resample of the breathing

3 different results – Same Images?????? (I do not believe...)

Game: Try to find the differences


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FREE BREATHING VS. THERMOPLASTIC MASK (PATIENTS)

Period Peak(Free Breathing vs. Termoplastic Mask)

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10001500200025003000350040004500500055006000

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Tim

e (m

s)

Free Breathing Termoplastic Mask

Phases Peak(Free Breathing vs. Termoplastic Mask)

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Immagini CT con e senza mascheraVideo immagine assiale lesione

Free Breathing vs. Termoplastic Mask

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Time (ms)

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Very similar but the thermoplastic mask seams to help the patients to breathing correctly


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PHASE AND PERIOD DIFFERENCES

Free Breathing vs. Termoplastic Mask

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Time (ms)

Phase


% Difference(Free Breathing vs. Termoplastic Mask)

-0.9%

0.5%

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.4%

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9.0%

7.0% 3.5%

-8.8%

-5.4%

-33.0%

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5%

Tim

e (m

s)

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0%

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Phase Period

With thermoplastic mask:1. The amplitude phases seams

very similar during a long period of time

2. The period seams to be a limitation dependent by the patients


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Coordinate Variation ... Which phases?

CORDINATA Z (Th. 2,0mm)

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Spigolo 1 Spigolo 2 Spigolo 3 Spigolo 4Spigolo 5 Spigolo 6 Spigolo 7 Spigolo 8

CORDINATA Z (Th. 0,5mm)

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CORDINATA X (Th. 0,5mm)

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CORDINATA Y (Th. 0,5mm)

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The best reconstruction....

Phases 20% - 60% seams the most

repeatable


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Phases vs. HU Variation

HU Variation - Thikness 1mm(Superion Lobe Lung Sx)

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Phases

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Termoplastic Mask

HU Variation - Thikness 3mm(Inferior Lobe Lung Dx)

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HU Variation - Thikness 3mm(Inferior Lobe Lung Dx)

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HU Variation - Thikness 3mm(Medial Lung Sx Nodule)

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Phantom HU Variation

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Phases

HU

Thikness 3mm Thikness 1mm

• Thickness variation means HU variation• Phases variation means HU variation • Position of the lesion means HU variation

• Which dose calculation do I have to do?• Which HU do I have to consider?

• May be a average MIP could be a good compromise

• ....do not believe absolutely to your calculation


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PATIENTS AT MODENA ....(4 PATIENTS DONE!! BUT MANY QUESTIONS TO SHARE....)


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4D DOSE RECONSTRUCTION OF THE RESPIRATORY PHASES(Possible!!! But I will be crazy, if it will be a clinical routine (3 days of work)) ... Some open issue about the deformation

4D TOMOTHERAPY DOSE RECONSTRUCTION

Dose Matrix (Phase 20%) +Dose Matrix (Phase 30%) +Dose Matrix (Phase 40%) +Dose Matrix (Phase 50%) +Dose Matrix (Phase 60%) +------------------------------------4D Dose Reconstruction


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Proton-Therapy.....

Few questions in my mind.....may be I need to change my mind!!!...are we sure about the dose calculation?...we will try to investigate the problems with the mesothelioma group (BRMOTRFI)


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... Someone better than us...


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Conclusion.....

1. Enthusiastic time and results about 4D exams2. Toshiba and VisionRT easy way to work with it3. Pulmonary and abdominal tracking can create different results4. Tracking signal must be investigated before to consider a perfect surrogate of the

target and OARs movements and the reconstruction usable for clinical dose calculation

5. Long time for post process and contouring can distort the patient objectives6. Many open issues about the ramp, thickness, HU, reconstructions, etc...

Which protocols?Purpose by Modena.... (Work in Progress)1. 1° Scan : 2mm Thickness (Scan set include minimum the total lungs)2. 2° Scan : 0.5mm Thickness (Scan set to include only the details or tumors)3. Reconstruction of the multiple phases (0% - 90%)4. Threshold respiration between 2500ms and 6500ms (9-25 BPM)5. Use of the 20% -60% phases to evaluate the average CT Dataset for dose

calculation purpose6. Evaluate and contouring the target volume on the best CT Data Set (0.5mm)7. Contouring all the phases and define an envelope target of the multiple phase

(ITV)8. DO NOT REDUCE THE MARGIN EXPANSION LESS THAN DOSE VOXEL DIMENSION

2-3mm9. .......MANY OTHER ISSUES MUST BE INVESTIGATED!!!!!

Can change the results of our treatment the 4D? The word must be passed to the doctors... But if someone want to work with us, it will be

a pleasure!!


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Acknowledges

“… under the “Ghirlandina” Tower….…..new opportunities and ideas are growing …

…and many people are working on it”

4D

Physicist Doctors

Medical Physics Dpt.Director: T.CostiPhysicist:• E.Cenacchi• B.Franzoni• A.E.Francia• G.Gottardi• G.GuidiDosimetrist• L.Boni• L.MoriniStudent• L.Binotti• P.Ceroni

Doctor:• M.Amadori• P.Antognoni• G.De Marco• P.Giacobazzi• M.Parmiggiani• S.Pratissoli• S.Scicolone• G.Tolento• All thereapist

U.O. Radiation Oncology

Director: F.Bertoni

Special Thanks to Luca, Elisa & Luciano

Will I see a 4D Tomotherapy Treatment?

4dct with optical tracking systems

Documents

d dose reconstruction

breathing phases

couch ramp

dose problem

couch movement visionrt

deformation dose matrix

free breathing

reconstruction usable