SYDNEY MEDICAL SCHOOL

SYDNEY MEDICAL SCHOOL

J. Kipritidis, H. C. Woodruff & P. J. Keall

Radiation Physics Laboratory

UNIVERSITY OF SYDNEY

Introducing VESPIRA new open-source effort to investigate CTVI in lung cancer radiotherapy

Innovations in Cancer Treatment and Care ConferenceOctober 15th 2015

› Radiation pneumonitis is a major dose-limiting toxicity for lung cancer radiotherapy, symptomatic in up to 30% of patients* and fatal in up to 2%.

D.A. Palma et al. 2013. IJROBP 85 pp. 444-50

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What is the clinical driver for CT ventilation imaging (CTVI)?

Galligas PET

› New clinical trials are testing whether functionally-adaptive treatments can improve outcomes by sparing ventilated / perfused lung.

D. A. Hoover et al. 2014. BMC Cancer 14:934

Technegas SPECT

› Unfortunately, “gold standard” ventilation imaging is only performed for a few % of patients.

› CTVI visualizes air volume changes in 4DCT by quantifying breathing-induced lung motion using deformable image registration (DIR).

T. Guerrero et al. 2006. PMB 51 pp. 777-791

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high

low

Ventilation

Compared to nuclear medicine imaging: 4DCT has high accessibility No added scan time/dose for lung cancer patientsx No freeware tools for CTVI; difficult to implement from scratch!

① Import 4DCT ② Perform DIR ③ Quantify volume or density changes

What is the clinical driver for CT ventilation imaging (CTVI)?

Data from Nepean Hospital(Penrith, NSW Australia)

› Ventilation via Scripted Pulmonary Image Registration (VESPIR)

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① vp = VESPIR_2();

VESPIR: The first open-source toolkit for CTVI

② vp.convertDCMAll();③ vp.loadVolumesAll();④ vp.segmentLungs();

⑥ vp.performDIR();⑦ vp.Jdet2Vmap();⑧ vp.Vmap2Dicom();

⑤ vp.getLungVolumes();

› We can evaluate the inhale exhale DIR in a freeware viewer (e.g. 3D Slicer):

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Before registration (Anatomic mismatch!)

After registration (Good match in lungs)

VESPIR: The first open-source toolkit for CTVI

› We can compare CTVI’s based on different published analysis methods:

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Lung volume change (“Jacobian-based”)

Lung density change (“HU-based”)

VESPIR: The first open-source toolkit for CTVI

› And understand the impact of different computational parameters

Similarity metric?

DIR engine?

B-spline grid spacing?

DIR regularization?

Gaussian filtering?

Apply DIR lung mask?

Apply temporal filtering to 4D motion?

λ = 0.001 λ = 0.1 λ = 1

λ = 5 λ = 10

high

low

4D-CBCT

J. Kipritidis et al. 2015. Med Phys 42 (3) pp. 1255-67

VESPIR enables cross-modality validation of CTVI across different clinical settings.

VESPIR: The first open-source toolkit for CTVI

Ventilation

Import 68Ga 4D-PET/CT

Compute CTVI

For each of 25 patients imaged at up to three timepoints:

VESPIR “Ground truth”

3D Galligas PET

HYPOTHESIS: CTVI should compare well against Galligas PET in terms of voxel-wise Spearman correlations.

High

LowVentilation

Post-processing1.Smoothing2.Normalization

Emphysema (Bullae)

Tumor obstruction

Clipped artery

Galligas PETQuantitative (voxel-wise correlation):

r = 0.50 ± 0.17 Range: (0.11 – 0.80)

Galligas PET

CTVI

CTV

I

30

20

10

0

# Lung voxels

Using VESPIR to validate CTVI

Qualitative (visual comparison):

› VESPIR has produced the highest voxel-wise correlations with nuclear medicine so far.

Quantitative (lobar-based correlation):

Using VESPIR to validate CTVI

Qualitative (visual comparison):

› VESPIR has also been used to compare CTVI and 68Ga-PET for surgical applications

r = 0.96 (p<0.01)

(11 patients, ~50 lobes)

E. Eslick et al.Eur. J. of Cardio-Thorac. (2015)

Modalities 4D-CT 4D-CBCT 99mTc SPECT 68Ga PET

4D-CT VCUPMCC VCU NCCC

PMCC

RNSH

BH-CT RNSH RNSH

4D-CBCT VCU NCCC

• NCCC = Nepean Cancer Care Centre (Prospective)• RNSH = Royal North Shore Hospital (Prospective)• PMCC = Peter MacCallum Cancer Centre (Retrospective)• VCU = Virginia Commonwealth University (Retrospective)

We are using VESPIR to validate CTVI across multiple modalities:

LEGEND Published Under-way

Where is VESPIR being used?

› You can explore CT ventilation imaging at your clinic! All you need is:- All you need is a Windows laptop running MATLAB 2014 or newer*

- An installation of Plastimatch, the freeware DIR software from: http://plastimatch.org

› To obtain a copy of VESPIR, send me an email (or say hello!)

john.kipritidis@sydney.edu.au

› You can find out more about CT ventilation imaging here:http://sydney.edu.au/medicine/radiation-physics/research-projects/CT-ventilation-imaging.php

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What do I need to run VESPIR? (and how can I get it?)

*A standalone is version coming soon!

Acknowledgements

DisclosureThis work was supported by a Cancer Institute NSW Early Career Fellowship, Cancer Australia Priority-driven Collaborative Cancer Research Grant APP1060919 and an NHMRC Australia Fellowship.