PET CT Scan guided target contouring

1. Approaching towards PET-CT
guided target delineation
Dr Kanhu Charan Patro
M.D,D.N.B[RADIOTHERAPY],FAROI[USA],PGDHM,PDCR,CEPC
RADIATIATION ONCOLOGIST
3/3/2024 1

2. Where is the Target?

3. Functional imaging
• Functional imaging is a method in medical
imaging of detecting or measuring changes
in metabolism, blood flow, regional chemical
composition, and absorption.

4. Modalities
• Positron emission tomography (PET)
– Fludeoxyglucose for Glucose metabolism
– O-15 as a flow tracer
• Single photon emission computed tomography (SPECT)
• Computed tomography (CT) perfusion imaging
• Functional magnetic resonance imaging (fMRI)
– BOLD
– Diffusion MRI
– Perfusion (blood flow)
– Arterial spin labeling MRI
– Blood volume
• Functional photoacoustic microscopy (fPAM)
• Magnetic particle imaging (MPI)
• Optical imaging
– Near-infrared spectroscopy (NIRS)

5. Tumor biology characterization
Radiotracer Characterization
18F-FDG Glucose metabolism
18F-FLT DNA synthesis
11C-MET Protein synthesis
60Cu-ATSM, 18F-FMISO Hypoxia
Radiolabeled Annexin V Apoptosis
Radiolabeled aVb3 integrin
antagonists
Angiogenesis
Apisarnthanarax and Chao 2005

6. Biological imaging for RT
• Improvement of diagnostic and staging
accuracy
• Guidance of target volume definition and dose
prescription
• Evaluation of therapeutic response

7. GTV-CTV-PTV

8. Target volume definition
• Gross tumor volume
(GTV)
• Clinical target volume
(CTV)
• Planning target volume
(PTV)

9. Concept of BTV

10. Biological target volume (BTV)
Ling et al. 2000

11. Conventional“ Planning in Radiotherapy
 Diagnostic Tools: CT, PET, MRI…
 Dedicated Planning CT-scan
 Definition of Target Volumes => Radiotherapy Plan
 Simulation
 Radiotherapy

12. IMAGE GUIDED RADIATION THERAPY
EQUIPMENT REQUIRED
CT-SCAN MRI PET-CT

13. Modified Planning in Radiotherapy
 Diagnostic Tools: CT, PET/CT, MRI…
 Dedicated Planning CT scan + 3D-Fusion with PET/CT scan
 Definition of Target Volumes on Fused Scans =>
Radiotherapy Plan
 Simulation
 Radiotherapy

14. PET-CT: Technical Changes
 New Detector Technology
Improved spatial resolution
Reduced time for acquisition of PET scans
 Implication of CT
Improved correction for attenuation and scatter
Correlation of morphology and metabolism
Reduced time of acquisition

15. Technical Requirements I
 Dedicated Radiotherapy Table and Supports @ PET/CT
Unit
 Intrinsic Laser for Patient Positioning @ PET/CT
 DICOM Data Transfer to Radiation Oncology

16.  Image-Fusion-Tool in RT Planning-Software
 Transfer of Table Position Data to Planning-Software
 If dedicated 3D RT-Laser @ PET/CT:
PET/CT Scan and Dedicated Planning CT as „One-Stop-
Shop“
Virtual Simulation on PET/CT Data feasible
Technical Requirements II

19. Standardized uptake value
mCi/ml (decay corrected) in tissue
mCi of tracer injected/body weight (grams)
SUV

20. Impact of PET/CT on Target Volume Definition
 Avoidance of ‚Geographic Miss‘
Enlargement of Target Volume
Requirement: High Sensitivity and Specificity
 Protection of non involved Tissue
Decrease of Target Volumes
Requirement: High Sensitivity

24. A. van Baardwijk et al.; Cancer treatment reviews 2006
Metaanalysis

25.  Studies until August 2005
 Only one Study (Daines et al. 2004) providing Correlation
with Histologic Findings
 Variable Impact of PET/CT on Target Volume Definition
A. van Baardwijk et al.; Cancer treatment reviews 2006
Metaanalysis

26.  Improved Target Volume Definition
Avoidance of Organs at Risk (OAR)
Potential Dose Escalation in Target Volume
 PET/CT During Radiotherapy:
Therapy Monitoring
Predictor for Outcome
A. van Baardwijk et al.; Cancer treatment reviews 2006
Metaanalysis

27.  Van Baardwijk et al. 2006:
6 Studies 2004-2005 (n=139; 4-40/Study)
Comparison of GTVCT and GTVPET/CT
2 Studies: No relevant Difference in Target Volumes
4 Studies: GTVPET/CT < GTVCT
Head and Neck Cancer

28. G.P., m, 46y; LN-Metastasis of Hypopharynxcarcinoma
Head and Neck Cancer: Example

29.  Van Baardwijk et al. 2006:
4 Studies 2000-2005 (n=51; 6-25/Study)
Comparison GTVCT and GTVPET/CT
1 Study: No Difference in Target Volume Definition
2 Studies: GTVPET/CT < GTVCT
1 Study: Average Change of Target Volume 26%
 Messa et al. 2005: Improved Detection and Delineation of
Atelectases
Lung Cancer

30. Senan et al. (2005), Crit Rev Oncol Hematol
NSCLC: Avoidance of Geographic
Miss

31. C. Messa et al.; Q J Nucl Med Mol Imaging 2006
NSCLC: PET/CT During Radiotherapy

32. Moureau et al. IJROBP 2005
Increased Target Volume in Oesophageal
Carcinoma

33.  Van Baardwijk et al. 2006:
 2 Studies (n=41)
 Lee et al. 2004: In 6/10 Cases Decrease of Target Volume
 Dizendorf et al. 2003: in 8% additional Lymphnodes, Change of
Target Volume in 4%
PET/CT in Lymphoma

34. VN.C., f, 34y; Cancer of Cervix Uteri; Additional Retroperitoneal Metastases
Example: Increased Target Volume

35. W.L., f, 61y; NSCLC; No Contralateral Involvement
Example: Decreased Target Volume

36.  Van Baardwijk et al. 2006:
2 Studies (n=46)
Ciernik et al. 2003: In 3/6 (!) Cases Increased Target
Volume (Additional Lymph Node Metastases)
Lammering et al. 2004:
Good Correlation between CT- and PET/CT-based Target
Volumes
Significant Increase of Target Volume in 6/40 Patients
Colorectal Carcinoma

37.  PubMed: 1200 Entries for „PET Radiotherapy“
 PET/CT: Impact on Target Volume Definition since early
2000‘s
 Large number of studies but small collectives
 Up to now no relevant prospective stuedies and long term
outcomes
Current Evidence

38.  Need for Provision of Technical Requirements
 Feasibility Proven Using FDG-PET/CT
 Currently available Data insufficient
Conclusions I

39.  Need for Prospective Studies
 New Horizons in Nuclear Medicine and Radiation
Oncology
 Interdisciplinary Team Work Indispensable
Conclusions II

40. Note down please.
• PET can improve the accuracy of gross tumor volume
delineation
• For radiation therapy planning. Next, PET using 18FDG
or more specific tracers may facilitate dose escalation
to radio-resistant tumor sub-volumes.
• Finally, PET can provide tumor characterization prior to
and during radiotherapy, facilitating adaptive
radiotherapy and other tailored treatment strategies.
• Although these are promising prospects, unresolved
issues remain and these applications are not yet ready
for introduction into routine clinical practice.

41. How far are we?
Probably not too far …
But don’t jump to quickly into routine practice…
Wait for validation!

42.  Dedicated 3D-RT Lasers @ PET/CT Unit
 Virtual Simulation
 4D-PET/CT:
Respiratory Gating
Heart Gating
 Use of SPECT/CT?
New Horizons: Nuclear Medicine

43. All that does not glitter
• PET Signal
– Does the lesion take up
glucose?
– Size?
• Bronchoalveolar
• Mucoepidermoid
• Mucinous
• Well Differentiated
– Thyroid
– HCC
– NET
– Prostate

44. Markers of Hypoxia and Proliferation
=> „Dose-Painting“ in IMRT
Acetate / Choline;
Aminoacids: e.g. Brain Tumours
Prostate Cancer:
68Ga-DOTA-BOM
Neuroendocrine Tumours: 68Ga-Peptides
New Horizons: Nuclear Medicine