4D CT scanning provides improved target delineation and treatment alignment for lung radiotherapy by accounting for tumor motion throughout the respiratory cycle. Analysis of 4D CT scans from 20 patients at NCCI found that accounting for tumor motion increased planning target volumes by an average of 9.1-42.5% depending on tumor size. Studies have also shown 4D CT can reduce needed planning margins from 2mm down when using bony anatomy for alignment by better visualizing tumor position. NCCI now uses 4D CT along with IMRT and daily CBCT to precisely target tumors and minimize dose to healthy tissues, with the goal of reducing radiation pneumonitis complications.

2. 4 Dimensional CT
Driving Improved Lung Radiotherapy Outcomes at NCCI
G Livingston, L Connors, A Fonseca, V Connors, P Dwyer and A Last

3. North Coast Cancer Institute
• 3 Departments
• 6 Linear Accelerators
• 7 Radiation Oncologists.
• 12 Physicists
• 55ish Radiation Therapists
(including specialty roles – Thoracic RT)
• ≈ 2000 Tx per annum

4. What’s the problem with Conventional CT?
• Tumour Distortions
= poor visualisation the tumour
• Poor information regarding motion
= cannot be sure where or if it moves
• Target Delineation errors
= less appropriate target size
• Less accurate treatment alignment.
= rely on bony surrogates.

5. Video of RSD phantom

8. 4DCT solution
• Low-pitched CT scan which images each slice
of the patient throughout each phase of the
respiratory cycle to produce a series of
respiratory phase correlated 3DCT scans.
• 4th dimension is respiratory phase.

10. CT Data

13. Amplitude
3D PTV
average
4D PTV
average Change (%)
Small (0-5mm)
n = 12
309cc 281cc 9.1%
Medium (5-10mm)
n = 7
194cc 213cc 9.8%
Large (>1cm)
n = 1
167cc 238cc 42.5%
PTV Size comparison (n=20)

14. Improved Treatment Alignment
JAN-JAKOB SONKE, PH.D., JOOS LEBESQUE, PH.D., M.D., AND MARCEL VAN HERK, PH.D. VARIABILITY OF FOUR-DIMENSIONAL COMPUTED TOMOGRAPHY
PATIENT MODELS Int. J. Radiation Oncology Biol. Phys., Vol. 70, No. 2, pp. 590–598, 2008

15. Improved Treatment Alignment
JAN-JAKOB SONKE, PH.D., JOOS LEBESQUE, PH.D., M.D., AND MARCEL VAN HERK, PH.D. VARIABILITY OF FOUR-DIMENSIONAL COMPUTED TOMOGRAPHY
PATIENT MODELS Int. J. Radiation Oncology Biol. Phys., Vol. 70, No. 2, pp. 590–598, 2008
Bony alignment: additional 2mm margin
surrounding the Target.
Neilson T, Hansen V, Westberg J, Hansen O, Brink C. A DUAL CENTRE STUDY OF SETUP ACCURACY FRO THORACIC PATIENTS
BASED ON CONE-BEAM CT DATA. Radiother Oncol Vol. 102, pp. 281–286, 2012

16. SABR (Stereotactic Ablative Body Radiotherapy)
- very high doses (>100Gy RBE)
- very few fractions (1-5#)
- very small margins (GTV/ITV + 5mm
- high precision (Planning and Treatment
- highly dependent on 4D imaging

17. Locally Advanced NSCLC
Grade 2+ Radiation Pneumonitis ~
30% (including 1-2% fatal). Palma et al 2013
(2012) NCCI implemented 4DCT +
IMRT + Daily CBCT as the standard.
- Maximising accuracy of RT
- Minimising dose to healthy
lung, oesophagus and heart

19. Thank You
thank you to Andrew Last, Pat Dwyer, Lisa Connors, Amara Fonseca, Vanessa
Connors and the NCCI Team