Functional Treatment Planning
Using PET/CT Imaging
Yusuf Emre Erdi, DSc, DABR
Assistant Attending Physicist
Department of Medical Physics
Memorial Sloan Kettering Cancer Center
New York
Overview
●
Why we need PET in RT
●
The issues of PET in RT
●
Our experience at MSKCC
●
Near future for Biological Target Volume
●
PET/CT is here!! Lets use it – 4D PET/CT
● Now we need…………
PET and PET/CT Growth
700 M
0
0
0
0
0
0
0
0M
0
2001
Frost & Sullivan – www.frost.com
2002
2003 (estimate)
Role of PET in Radiation Therapy
1. Accurate Staging ->better management
High sensitivity of PET improves staging:
cancers of the lung, H&N, esophagus, colorectum,
breast and melanoma and lymphoma – especially
lymph nodes.
Combining all oncology applications surveyed:
84-87% sensitivity, 88-93% specificity, 87-90%
accuracy – management changes average 30%*
*JNM Supplement V42, 2001- Gambhir et al
Role of PET in Radiation Therapy
2. Target Definition
Paratracheal
Lymph Nodes
PTV CT+PET
PTV CT
Role of PET in Radiation Therapy
3. Monitoring Treatment
SUV x V
Gy
20
Vol (cc)
SUVmax
15
10
5
0
-10
0
10
20
30
40
50
60
70
Days
SUVmax
SUV max =
(Lesion Activity/cc)max
(ActivityInjected Mass Body)
70
60
50
40
30
20
10
0
-10
0
10
20
30
40
50
Days
Volume
60
70
Problems of PET in RT
● Image Registration
● Patient Positioning
● Cross-Departmental Issues
Problems of PET in RT
● Interpretation of Images
•Know chemo effects
•Choose proper gray-level for target definition
•Tumor vs normal uptake quantitatively (SUV)
FDG-PET/CT Experience at MSKCC
§ NSCLC –PTV ↑ (nodes), occasional ↓
(atelectasis or inflammatory vs tumor)
§ Anaplastic thyroid – PTV ↑ or ↓
(inflammatory vs tumor)
§ Lymphoma – Confirm CT-defined PTV
§ Nasopharynx –PET used to confirm, modify
CT/MR-based PTV
This is in addition to extensive staging use
NSCLC
•
11 patients. Increased PTV volume in 7 patients,
mostly for nodal disease
•
PTV outline changed for all patients
•
New regional lesion and a distant met detected in 2
patients
CT
PET
Lymphoma –
36 Gy
Sim CT
CT – PET/CT
iliac lymph
node
courtesy of Ellen Yorke, MSKCC
PET - PET/CT
Nasopharyngeal –
Sim CT
courtesy of Ellen Yorke, MSKCC
CT – PET/CT
70.2 Gy
PET-PET/CT
Biological Target Volume?
target volume
GTV
Hypoxia
• F-MISO
Tumor growth
Biological Eye View
• IUDR
courtesy of Cliff Ling, MSKCC
Tumor cell density
• FDG
Radiobiological
treatment plan
PET Isotopes/Tracers for RT
Isotope
C-11
(20 min)
N-13
Tracer
Physiology
acetate
methionine
choline
oxidative metabolism
protein synthesis
cell membrane turnover
(10 min)
ammonia
blood flow
O-15
(2 min)
water, CO2
O2
blood flow
necrosis
F-18
(110 min)
FFDG
FMiso
FDHT
FLT
bone
glucose metabolism
hypoxia
androgen receptor
tumor proliferation
Cu-60
I-124
(24 min)
(4.2 day)
ATSM
Iodine
IUDR
hypoxia
thyroid
DNA synthesis
Prostate Cancer
18FDG
courtesy of Homer Macapinlac, (MSKCC) MDACC
11C-Methionine
Prostate Cancer
FDG
courtesy of Steven Larson, MSKCC
FDHT
Thyroid Cancer
124I
- Iodine
Thyroid Cancer
203 cGy/mCi
229 cGy/mCi
125 cGy/mCi
courtesy of John Humm, MSKCC
18FDG
124I
Brain
124IUDR
courtesy of Ron Blasberg, MSKCC
18FDG
60Cu-ATSM in NSCLC
FDG-PET
Cu ATSM-PET
Pre-therapy CT
Post-therapy CT
FDG-PET
Pre-therapy CT
Cu ATSM-PET Post-therapy CT
T/M = 3.60
T/M = 1.26
Responder
Non-Responder
Dehdashti et al., Eur J Nucl Med Mol Imag 30:844-850, 2003.
Washington
WASHINGTON•
WASHINGTON•UNIVERSITY•
UNIVERSITY•IN•
IN•ST•
ST•LOUIS
Institute
of Radiology
MIR Mallinckrodt
Cu-ATSM-Directed Radiation Therapy
CT
60Cu-ATSM-PET
Gross Tumor
Volume
Chao et al., IJROBP 2001:49;1171-1182
Tumor
Hypoxic
Map
Washington
WASHINGTON•
WASHINGTON•UNIVERSITY•
UNIVERSITY•IN•
IN•ST•
ST•LOUIS
Institute
of Radiology
MIR Mallinckrodt
Innovation of PET/CT
CT
Trans
Emiss
PET/CT Systems on the Market
Siemens/CTI/CPS
Gantry Design
Biograph/Reveal
Tunnel Diameter (cm)
Scan Length (cm)
CT (Spiral)
# Slices
PET
Crystal
Acquisition
Atten Corr
70
145
Somatom Sensation
16
ECAT ACCEL
LSO
3D
CT
GE
DiscoveryLS DiscoveryST
Philips
Gemini
70 / 60
165
70
160
70 / 62
195
Light Speed
16
Light Speed
8
MX8000
16
Advance NXi
BGO
2D/3D
CT/Ge-68
(new design)
BGO
2D/3D
CT
Allegro
GSO
3D
CT/Cs-137
PET/CT Pros and Cons
Advantage: Image registration process is eliminated.
Disadvantage: Due to respiration (motion), the captured lesion image
in CT can be in any phase, then, PET data may not match the CT.
Attenuation correction (AC) becomes inaccurate.
CT- End-of-Inspiration
PET - Rod Source
AC with CT data
snapshot of the lesion (~ sec)
AC with rod source
time average (~min)
Acquisition
Lung Scan-Arms Up Protocol
● 4D (cine) CT Scan
- 140 kVp, 100 mA
GE Discovery LS PET/CT
BI BO
- 0.5 s/rot, 0.45 sec interval
- T+1 sec, 2.5 mm slices
- Step & Shoot
● Helical CT Scan
- 140 kVp, 80 mAs
- 0.8 s/rot, 5 mm slices
Varian RPM System
- 4.25 mm interval
● PET Scan
● Gated (4D) PET Scan
- 10-15 mCi, 3-4 min/bed
-1 bed position
- 2-4 beds
- 10 min/ 10 bins
Data
4D CT
Helical CT
PET
4D PET
4D-PET/CT Fusion
5 mm CT image set at phase ‘ i ‘
1
n
2
Couch Position
(PET + CTAC)|(phase)i
Fused PET/CT|(phase)i
1 2 3 4 …... n
courtesy of Sadek Nehmeh, MSKCC
Gated-PET Bin #
Advantages of 4D PET – Improved SUV
SUVmax = 3.3
4D PET with Clinical CT
courtesy of Sadek Nehmeh, MSKCC
34 %
SUVmax = 4.4
4D PET with 4D CT
Advantages of 4D PET-Reduced PTV
G
NG
LymanNTCP:
NTCP:25%
25%
Lyman
22%
22%
Are we ready for PET/CT Sim?
Not yet, but very close
Xeleris®
Advantage Workstation®
Discovery Workstation®
Now We Need
● Fully integrated/automated gating capabilities for respiration, EKG,
and motion correction for voluntary patient motion
● Patient positioning systems/rooms
● 100% compatible DICOM RTP object definitions between vendors
● Segmentation and visualization tools designed to handle combined data
● Tools to handle multiple images for BTV