MRI Guided, Conformal
Brachytherapy for Cervical Cancer
Yusung Kim1, Ph.D.
Manickam Muruganandham1, Ph.D, Ryan Flynn1, Ph.D. Joseph Modrick1, Ph.D.,
Geraldine Jacobson2, M.D.
1Radiation
Oncology Department, Carver College of Medicine, University of Iowa
Oncology Department, School of Medicine, West Virginia University
2Radiation
UNIVERSITY of IOWA Carver College of Medicine
v  Disclosure
• "This work was partly supported by a research grant from
Varian Medical Systems, Inc (Palo Alto)”: Research Collaboration
Grant Jan 2011 – July 2012
UNIVERSITY of IOWA Carver College of Medicine
Learning Objectives
A.  Understand the limitations of Point-A based
brachytherapy
B.  Understand the benefits of MRI-guided,
conformal brachytherapy
C.  Understand the current challenges of MRIguided, conformal brachytherapy
UNIVERSITY of IOWA Carver College of Medicine
1
1. Which of the following statements is correct for a
conventional intracavitary brachytherapy implant
utilizing the Manchester system for cervical cancer?
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2.
In 1953, a revision to Point A was introduced due
to the considerable variation of the original Point A
definition.
Point A right and left represent clinical target
points, so overdose, instead underdose, would be
preferable.
Conformal planning does not require a CT dataset
for dose calculations, and is limited when CT
datasets are used.
In 2000, the ABS introduced a new dose point,
Point H that is conceptually different from Point A
with the aim of accounting for different cervix
sizes.
ICRU Report 38 recommends that the rectum and
bladder point doses must not more than 80% of
brachytherapy prescription dose for each fraction.
Po
1.
UNIVERSITY of IOWA Carver College of Medicine
2. Conformal brachytherapy plans require 3-D imaging datasets
and are evaluated by DVH parameters and not by point
doses. GEC ESTRO Working Group I and II have provided
all of the following recommendations EXCEPT:
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CT
V
2.
A 3-5 mm CTV to PTV margin is recommended to
account for intra-/inter-scanning motion during
CT or MR.
The prescribed dose to the target volume should
be consistent with the institution’s standard Point
A dose without changing the fractionation
scheme.
The D90 values for the target volumes should be
used for plan optimization and evaluation instead
of D100.
D2cc values for OARs should be used to evaluate
OAR sparing.
Point A doses and ICRU-defined rectal and
bladder doses should continue to be reported.
m
m
1.
UNIVERSITY of IOWA Carver College of Medicine
3. There are a number of challenges related to introducing
MRI-guided, conformal brachytherapy into the clinic. All
of the following statements are true EXCEPT:
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2.
The MR distortions have been reported to be
minimal, but each institution still needs to
assess the distortions before implementing
MRI-guided brachytherapy.
To improve source-reconstruction accuracy,
clinical CT-MRI registration for each plan is
recommended.
Applicator positions can be displaced by more
than 3mm due to MR imaging artifacts.
Titanium and plastic applicators can be used
for MRI-guided brachytherapy, but imaging
artifacts need to be validated by each
institution.
Reconstructing the brachytherapy source path
is easier with 2D image guidance than with 3-D
CT / MRI guidance.
Th
1.
UNIVERSITY of IOWA Carver College of Medicine
2
4. Early clinical outcomes of MRI-guided, conformal
brachytherapy have been promising. The following
statements are true EXCEPT:
20%
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3.
The improvements of rectal, bladder and sigmoid sparing
are dependent on the size of the high-risk CTV.
The dose volume parameters of conformal brachytherapy
should be reported using the radiobiologically equivalent
dose in 2 Gy fraction in order to account for the EBRT
dose contribution.
When using current intracavitary applicators for cervical
cancer patients who are eligible for curative
brachytherapy, clinicians can generally achieve 100%
coverage of the HR-CTV with the prescription dose..
A conventional Point A plan is recommended as the initial
dwell time condition when doing volume-based treatment
plan optimization for cervical cancer brachytherapy.
The recommended dose limits for rectum and sigmoid
(D2cc < 70-75Gy) are lower than that of bladder (D2cc <
90Gy) while the dose limits recommended by ICRU 38 for
the rectum and bladder points are the same.
W
2.
do
1.
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v  Standard Treatment for locally advanced cervical cancer
• Combined EBRT and BT with concomitant cisplatin
EBRT
PLUS
Brachytherapy
• A patterns-of-care study confirmed BT remains the cornerstone of RT for
cervical cancer [Hanks et al. Cancer 1983]
• ABS recommends the use of BT as a component of the definitive treatment
of locally advanced cervical cancer [ABS consensus guidelines2012]
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v  GYN Intracavitary BT
• Manchester System: one of the oldest and the most
extensively used systems in the world
•  It is characterized by doses to four points: Point A (H),
point B, rectum and bladder points.
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3
v  GYN Intracavitary BT
• Manchester System: one of the oldest and the
most extensively used systems in the world
•  It is characterized by doses to four points: Point
A (H), point B, rectum and bladder points.
• ICRU Report #38 defined Rectum &
Bladder points ≤ 80 % Rx
UNIVERSITY of IOWA Carver College of Medicine
•
Manchester System
•
Planning: Utilizing reference lines
•
The original point A concept (1938): never changed
where the uterine vessels cross the ureter: dose limiting
q
Mucous membrane of the lateral fornix
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•
Manchester System
•
Planning: Utilizing reference lines
•
Revised Point A(1953): a cervical flange was proposed due to the
difficulties of recognizing the ovoids’ surface on radiograph
*Wider variations of point A
ABS Recommended Point A(H) (2000, 2012)
q *The use of Point A(H) causes minimal dose variations from Rx
q
•
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4
• Manchester System
•  Source-pathway Reconstruction: 2D orthogonal radiograph
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v  GYN Intracavitary BT
• Planning is Simple and
Fast since it is System
based not patientanatomy specific
o
o
Thus, dose prescription at Point A could risk under dosage of large
cervical cancers or overdosage of small ones.
ABS (2012) recommends the use of 3-D images (CT / MRI)
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MRI-Guided Conformal
Brachytherapy
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5
v  MRI-Guided, Conformal Brachytherapy
• Definition:
•  Use MRI: as a plan image modality
•  Perform Tx plan ‘Conformal’ to tumor and OAR
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v  MRI-Guided, Conformal Brachytherapy
• Current Status (ABS survey IJROBP 2010,p104):
•  MRI as a plan image modality
• Only 2%
•  Rx on target-volume
• Only 14%
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•  CT as a plan image modality
• 55% institutions of ABS
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6
• Why is not CT enough?
“Visualization of the tumor is very difficult with CT
which makes MRI necessary” (EMBRACE Protocol p8)
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• Why is not CT enough?
Kim Y., et al., AAPM 2010
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v  MRI-Guided, Conformal Brachytherapy
• Clinical Challenges:
•  Lack of logistics and experience
• Contouring
• Plan goal: DVH
• Current clinical data: linked with Points
(Point A, rectum & bladder points)
• Rx: where? How much?
• OAR constraint: tolerance?
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7
• Physics-Oriented \ Technical Challenges:
•  Source-pathway reconstruction
•  Localization of an Applicator
• Patient’s movement: HDR room <-> MR room
•  Volume-based planning logistics
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v  Clinical Challenges
• GEC-ESTRO Working Group Recommendation (I):
•  ABS (2012) guideline adopts GEC-ESTRO recommendations for
contouring, image-based treatment planning, and dose reporting
•  Concept: HR-CTV and IR-CTV (No PTV)
Haie-Meder et al. R&O 74 (2005) p235-45
Lindegaard and Tanderup. Varian
symposium ABS 2008
Cf. GEC-ESTRO (Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology )
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• No PTV in 3-D imaging guided BT
•  Uniform dose distributions in PTV: impossible in BT
•  PTV margins cannot be directly applied in BT
•  8% overall dose escalation per mm PTV margin
Tanderup et al. ‘PTV margins should not be used to compensate for uncertainties in 3D image guided intracavitary
brachytherapy, R&O 97(2010), p495-500
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8
v  Clinical Challenges
• Learning-Curve: Contouring on 3T MRI
•  Retrospective contouring: 53 T&O implant cases
per GEC-ESTRO Guidelines
•  Performed inter-observer (MD) variations:
Sun W., Bhatia SK, Jacobson GM, Kim Y Practical Radiation Oncology 2012 (under review)
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v  Clinical Challenges
• GEC-ESTRO Recommendation (II) & EMBRACE Protocol:
•  DVH parameters: as a treatment plan guidelines
•  Rx: D90 of HR-CTV (Not D100)
•  75 – 96 Gy10 in EQD2: EBRT + BT
•  For institutions previously using Point A, it is recommended
to use the point-A dose as the dose (D90) used for
prescription to the HR-CTV
•  OAR constraint (D2cc):
•  Rectum: 70-75 Gy3 in EQD2
•  Bladder: 90 Gy3 in EQD2
•  Sigmoid: 75 Gy3 in EQD2
•  Point A, ICRU rectum and bladder doses should continue to be
reported
Potter et al. R&O 78 (2006) p66-77
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v  Clinical Challenges
• GEC-ESTRO Recommendation (II) & EMBRACE Protocol:
•  DVH parameters: as a treatment plan guidelines
• Rx: D90 of HR-CTV
•  75 – 96 Gy10 in EQD2: EBRT + BT
• OAR constraint:
•  Rectum: 70-75 Gy3 in EQD2
•  Bladder: 90 Gy3 in EQD2
•  Sigmoid: 75 Gy3 in EQD2
• 3-D Imaging guided, Conformal Planning is not Possible without total EQD2
(EBRT+BT) Calculations
Potter et al. R&O 78 (2006) p66-77
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9
v  EQD2
• EQD2 Calculations: EBRT + BT
EQD2 =
BED
⎛
⎞
⎜
2 ⎟
⎜1 + α ⎟
⎜
β ⎟⎠
⎝
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v  EQD2
• EQD2 Calculations: EBRT + BT
⎛
⎞
⎜
d ⎟
Nd ⎜1 + g
α ⎟⎟
⎜
β ⎠
⎝
EQD2 =
where α = 10(tumor ),α = 3(OAR )
β
β
⎛
⎞
⎜
2 ⎟
⎜1 + α ⎟
⎜
g ( HDR & EBRT ) = 1
β ⎟⎠
⎝
e − µt ⎤
2 ⎡
g ( LDR ) =
ln 2
1−
whereµ =
andT 1 = 1.5hr
2
µt ⎢⎣
µt ⎥⎦
T1
2
2 ⎡
NY − SY 2 ⎤
− µt
− µt
1−
⎥ whereY = 1 − e , K = e and
µt ⎢⎣
Nµt
⎦
2 − µt
N +1 − µNt
NK − K − NK e
+K
e
g ( PDR ) =
S =
2
(1 − Ke µ )
− t
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v  DVH→EQD2 Calculator.xls
The University of Iowa Hospitals and Clinics
Department of Radiation Oncology
HDR Brachytherapy for Cervical Cancer
Patient Name :
1. EBRT Rx
ID:
MR, IGBT
Sch 1
Boost
2. HDR BT Prescription to HR-CTV
HR-CTV
PTV
Rx Dose
[Gy]
45
0
Fx Size
[Gy]
1.8
Fx #
25
EBRT Total
30
6
5
Overall Target VOL
3. Currently Delivered Dose to HR-CTV
HR-CTV
Fx 1
Fx 2
Fx 3
D90
[Gy]
[Gy]
[Gy]
Dose[Gy]
5.9
6.1
6.0
EQD2
7.9
8.1
8.0
Point H
Left
5.8
5.9
5.8
EQD2
7.7
7.9
7.7
Right
6.0
6.2
6.1
EQD2
8.0
8.3
8.1
Fx 4
[Gy]
6.2
8.3
Fx 5
[Gy]
5.9
7.9
5.9
7.9
6.3
8.4
5.8
7.7
6.3
8.4
EQD2
[Gy10]
44
0
44
40
84
Fx 6
[Gy]
0.0
0.0
0.0
EQD2 [Gy10]
Total
Diff [Gy]
Dose
Delivered-Rx
0.1
30.1
40.1
Tot D[Gy] Mean D[Gy]
29.2
5.8
38.9
6.5
30.9
6.2
41.2
6.9
4. Currently Delivered Dose to OAR
Rectum
Bladder Sigmoid
GEC-ESTRO Guidline
D2cc
D2cc
D2cc
< [EQD2 [Gy3]]
6.4
9.4
6.4
ABS Guidline
ICRU
ICRU
< 80% Rx[Gy]
4.8
4.8
*Allowable Dose per Fx
Fx 1
Fx 2
Fx 3
Fx 4
Fx 5
Fx 6
Rectum
24.8
25
27
26
24
D [Gy]
3.5
3.7
3.6
3.7
3.5
ICRU Pt
%-Dose
58.3%
61.7%
60.0%
61.7%
58.3%
0.0%
D [Gy]
3.4
3.6
3.8
3.4
3.4
D2cc
EQD2
6.1
6.5
6.8
6.1
6.1
0.0
Diff
-0.2
0.1
0.5
-0.2
-0.2
0.0
Bladder
ICRU Pt
D2cc
D [Gy]
%-Dose
D [Gy]
EQD2[G
Diff
Sigmoid
D2cc
D [Gy]
EQD2
Diff
Tot D[Gy]
18.0
#REF!
31.7
Tot D[Gy]
23.9
200
5.1
85.0%
5.1
9.2
-0.2
210.3
4.5
75.0%
4.9
8.8
-0.5
180
4.6
76.7%
5.4
9.7
0.4
170
4.9
81.7%
160
4.8
80.0%
0.0%
0.0
0.0
0.0
0.0
0.0
0.0
38.6
3.1
5.6
-0.8
35
3.8
6.8
0.5
36
2.5
4.5
-1.9
37
3.9
7.0
0.7
38
4.1
7.4
1.0
0.0
0.0
Have to fill out
5302009
EQD2
[Gy3]
43
0
43
15.4
27.7
Tot D[Gy]
17.4
31.3
EQD2
[Gy10]
0.1
%-Dose
60.0%
Diff
EQD2
-0.1
%-Dose
79.7%
Diff
EQD2
-0.4
Diff
EQD2
-0.5
UNIVERSITY of IOWA Carver College of Medicine
10
v  Clinical Challenges
• Worksheets per ABS: available
•
•
•
•
EQD2 Worksheets#1 per ABS
http://www.americanbrachytherapy.org/guidelines/LQ_spreadsheet.xls
EQD2 Worksheets#2 per ABS
http://www.americanbrachytherapy.org/guidelines/
gyn_HDR_BT_docu_sheets.xls
•  Brachytherapy Guidelines per ABS
•  http://www.americanbrachytherapy.org/guidelines/index.cfm
UNIVERSITY of IOWA Carver College of Medicine
• Clinical Challenges:
•  Current clinical data: linked with Points (Point A,
rectum & bladder points)
•  Evaluate conv T&O Plans: using 3T MRI
• Retrospective studies
• 40 HDR plans of six patients with FIGO stage
Ib1-IV cervical cancer
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• Evaluate conv T&O plans:
•  OAR (D2cc)
%Dose over Recommended Limits
Rectum (D2cc)
Bladder (D2cc)
Sigmoid (2cc)
100%
90%
80%
70%
60%
50%
Non-Bulky
Low-Bulky
Bulky
ALL
•  D2cc was recorded up to 190% (Rectum: 80 ± 35%) of the tolerance,
170% (Bladder: 82 ± 33%), and 170% (Sigmoid: 72 ± 32%)
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11
v  Clinical Challenges
• ICRU Rectum & Bladder Points’ Dose over D2cc
•  ICRU rectum and bladder points: No strong correlation w/ Max dose
(D2cc)
•  Could underestimate Max dose (D2cc): down to 23%
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v  Clinical Challenges
• High-Risk CTV (D90) vs Point A
%Dose over Prescription Dose
120%
110%
100%
90%
80%
70%
60%
HR-CTV (D90)
Point A Dose
50%
Non-Bulky
Low-Bulky
Bulky
ALL
•  D90 of HR-CTV: Non-Bulky 109% (± 21%) of Rx, Low-Bulky 100% (±
5%), and Bulky 72% (± 17%).
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v  Physics / Tech Challenges
1.  Source-pathway reconstruction
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12
v  Physics / Tech Challenges
1.  Source-pathway reconstruction
•
•
Depending on the Mat’l of Applicator
•
Plastic
•
Titanium
Due to considerable uncertainties of registration and inter-scan
motions: CT-MRI fusion is not recommended for cervical cancer
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1.  Source-pathway reconstruction
•
T&Ring Plastic applicators
•
T&Ring Dummy catheter: CuSO4 (MRI-Marker Agent for T1weighted MRI)
•
Reconstruction should be performed on T1-weighted MRI
Haack, S. et al, R&O 2009, p187-193
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•  Plastic applicators: T&Ring
Lindegaard and Tanderup. Varian symposium ABS 2008
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13
1.  Source-pathway reconstruction
•  Plastic applicators: T&O
•
•
Dummy catheter: saline water plus iodine compound
Note: Saline is MRI-Marker agent for T2-weighted MRI
Perez-Calatayud, J. et al. R&O 2009, p181-186
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v  Physics / Tech Challenges
•  Titanium T&O
•
•
First patient safety-related tests: e.g Heat
Artifacts and distortion evaluations
Titanium Applicator
(1.5T compatible: Varian)
Kim, Y. et. al. IJROBP 2011
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1.  Titanium T&O: with 3.0Tesla MRI
•  Artifacts and distortions at T1-weighted-MRI
•
•
Artifacts: less than 1.5±0.5mm (phantom) & 2.6±1.3mm (invivo)
However, 6.9±3.4mm (in-vivo) at T2-weighted MRI (3mm slice
•
Distortions: no more than 1.2±0.6mm
thickness)
Kim, Y. et. al. IJROBP 2011
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14
1.  Titanium T&O: with 3.0Tesla MRI
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v  Titanium Artifacts & Distortion
• Dependent on
•  MR Scanner
•  Institution’s MR Sequence Protocol: Women’s Pelvic
•  Type of titanium applicators
• Titanium applicator is feasible for MRI-guided
Brachytherapy
• Every department has to characterize their titanium
applicators for their specific MR sequence
•  Recommended to find optimal sequence in terms of
minimal artifacts and distortions
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•  MRI Marker-Flange
•  Conventional cervical flange + MRI marker
Saline: used as a marker agent
T1-weighted MRI
T2-weighted MRI
T1 & T2 fused images
Kim, Y. et. al. World Congress of Brachytherapy (ABS+GEC ESTRO) 2012 (accepted) / Patent-process
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15
•  MRI Marker-Flange
Kim, Y. et. al. World Congress of Brachytherapy (ABS+GEC ESTRO) 2012 (accepted) / Patent-process
UNIVERSITY of IOWA Carver College of Medicine
v  MRI Verification of T&O implant
• Early learning-curve periods
• 18 T&O implant cases were verified by using MRI
• Two cases: found as non-deliverable implants
• Two cases: adjusted Rx (i.e. changed the active length
of tandem)
US has many advantages and has
been very useful.
However it limited to clearly
show whether Tandem is
implanted within uterus
MRI clearly answers whether
tandem is implanted with uterus
Thanks Jill Jespersen, RT(R)(T)(MR) and
Alyssa Plathe, RT(R)(T)(MR)
Thanks Amy Oldham, RT(R)(T)
UNIVERSITY of IOWA Carver College of Medicine
v  Source-Pathway Reconstruction
• Geometry of Titanium FSD T&O
3.5mm
1mm
(Ir-192 (5mm) source)
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16
v  Physics / Tech Challenges: II
• Localization of T&O
•  Patient’s movement between HDR room and MR room
• Developed T&O Localization system
•  Potable T&O support
• 3D BT-White board: dedicated for 3D imaging guided BT
• Minimal T&O movements: HDR room ↔ CT/MRI room
Old way
3D BT-White Board
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v  Localization of T&O and Patient
• T&O displacement: evaluations
• Compared pre-X rays and post-X rays (i.e. before / after MRscan)
Kim, Y. and Huang Y. Radiotherapy and Oncology 99, S257-8, 2011
UNIVERSITY of IOWA Carver College of Medicine
v  Physics / Tech Challenges: III
3.  Volume-based plan logistics
•
•
Solely inverse-optimization (e.g. IMRT): not recommended
•
May results in hot or cold spots in TV and in noncontoured OAR
(the vagina, connective tissue, nerves, vessels, or the ureters)
Volume optimization from standard point-A plan: recommended
ABS guidelines. Part II. HDR. Viswanathan, et. al. Brachytherapy 2012;11:47-52
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17
v  Physics / Tech Challenges: III
3.  Volume-based plan logistics
•
•
•
Solely inverse-optimization (e.g. IMRT): not recommended
Volume optimization from standard point-A plan: recommended
3 Logistics: tested
•
Graphical Opt
•
Pure Inv-Opt
•
Hybrid Inv-Opt: Standard Point-A plan -> Inv Opt -> graphical
opt.
Standard Opt: ABS recom
Graphical Opt
Inverse Opt
Hybrid Inverse Opt
UNIVERSITY of IOWA Carver College of Medicine
v  Physics / Tech Challenges
Standard Opt:
ABS recom
Graphical Opt
Inverse Opt
Hybrid Inverse Opt
Kim, Y., et. al. Brachytherapy 2009;8(2):121-122
UNIVERSITY of IOWA Carver College of Medicine
2.  Volume-Optimization Logistics
Graphical Opt
Inverse Opt
Hybrid Inverse Opt
Standard T&O plan
(Conv)
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18
2.  Dosimetric Benefits: Volume-Optimization
•
Retrospectively re-planning: 40 T&O plans
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2.  Dosimetric Benefits: Volume-Optimization
•  Bulky tumor: D90 improved 9±11%, but only
from 72% to 81%
UNIVERSITY of IOWA Carver College of Medicine
2.  Dosimetric Benefits: Volume-Optimization
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19
v  Limitations: even MRI-guided-conformal BT
UNIVERSITY of IOWA Carver College of Medicine
v  Limitations: even MRI-guided-conformal BT
•
Current two approaches
1.  Interstitial BT
•
ABS (2012) recommends to considering interstitial BT for bulky
cervical tumor whose disease cannot be adequately encompassed by
intracavitary application
Interstitial
UNIVERSITY of IOWA Carver College of Medicine
v  Limitations: even MRI-guided-conformal BT
•
Current two approaches
2. Intracavitary + Interstitial
a.  T&Ring + Needles: Vienna applicators
T&R + Needles
Kirisits, C., et. al. IJROBP 2006;65(2):624-630
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v  Limitations: even MRI-guided-conformal BT
•
Current two approaches
2. Intracavitary + Interstitial
a.  T&O + Needles
T&O + Needles
Jurgenliemk-Schulz, I., et. al. R&O 2009;93:322-330
UNIVERSITY of IOWA Carver College of Medicine
v  Limitations: even MRI-guided-conformal BT
•
Another approach: Univ of Iowa
1.  Intensity-modulated BT: early-stage of research
Electronic BT (<50keV)
R. Flynn, Y.Kim, Radiotherapy and Oncology 99, 2011, S60-S61 & Patent (On-process)
UNIVERSITY of IOWA Carver College of Medicine
•
Intensity-Modulated BT: IMBT
•
•
•
Current TG 43 protocol: needs to be modified
No commercial Tx planning system available
No commercial Applicators available
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v  Conclusions
• The tumor coverage of conventional Point-A based
brachytherapy is significantly affected by tumor size
• MRI guided, conformal BT has shown strong potential in
improving current clinical outcomes from 2D-Point-A based
techniques
• Clinical logistics and experience has progressed, including
recent international-multi-institution based protocol (EMBRACE)
UNIVERSITY of IOWA Carver College of Medicine
1. Which of the following statements is correct for a
conventional intracavitary brachytherapy implant
utilizing the Manchester system for cervical cancer?
C
...
re
c
g
...
in
t..
.
S
ni
n
ep
o
rt
3
8
AB
he
,t
R
00
20
U
In
on
IC
R
...
is
i
an
d
fo
rm
al
re
v
rig
ht
A
,a
In
Po
19
in
t
53
5.
10%
8%
on
4.
19%
14%
to
3.
49%
le
ft
...
2.
In 1953, a revision to Point A was introduced due to
the considerable variation of the original Point A
definition.
Point A right and left represent clinical target points,
so overdose, instead underdose, would be
preferable.
Conformal planning does not require a CT dataset
for dose calculations, and is limited when CT
datasets are used.
In 2000, the ABS introduced a new dose point, Point
H that is conceptually different from Point A with
the aim of accounting for different cervix sizes.
ICRU Report 38 recommends that the rectum and
bladder point doses must not more than 80% of
brachytherapy prescription dose for each fraction.
pl
an
1.
UNIVERSITY of IOWA Carver College of Medicine
2. Conformal brachytherapy plans require 3-D imaging datasets
and are evaluated by DVH parameters and not by point
doses. GEC ESTRO Working Group I and II have provided
all of the following recommendations EXCEPT:
73%
17%
c
I..
d
an
s
do
se
A
in
t
Po
2c
.
R
...
th
...
fo
r
s
lu
e
s
va
lu
e
va
D
2% 0%
fo
rO
A
t..
.
se
do
90
e
Th
e
D
cr
ib
ed
to
PT
...
8%
pr
es
CT
V
m
m
5.
5
4.
3-
3.
A
2.
A 3-5 mm CTV to PTV margin is recommended to
account for intra-/inter-scanning motion during CT or
MR.
The prescribed dose to the target volume should be
consistent with the institution’s standard Point A dose
without changing the fractionation scheme.
The D90 values for the target volumes should be
used for plan optimization and evaluation instead of
D100.
D2cc values for OARs should be used to evaluate
OAR sparing.
Point A doses and ICRU-defined rectal and bladder
doses should continue to be reported.
Th
1.
UNIVERSITY of IOWA Carver College of Medicine
22
3. There are a number of challenges related to introducing
MRI-guided, conformal brachytherapy into the clinic. All
of the following statements are true EXCEPT:
2.
3.
4.
18%
8%
2%
2%
Th
To
e
5.
70%
The MR distortions have been reported to be
minimal, but each institution still needs to assess the
distortions before implementing MRI-guided
brachytherapy.
To improve source-reconstruction accuracy, clinical
CT-MRI registration for each plan is recommended.
Applicator positions can be displaced by more than
3mm due to MR imaging artifacts.
Titanium and plastic applicators can be used for
MRI-guided brachytherapy, but imaging artifacts
need to be validated by each institution.
Reconstructing the brachytherapy source path is
easier with 2D image guidance than with 3-D CT /
MRI guidance.
M
R
di
st
or
tio
im
ns
pr
ov
ha
e
Ap
..
so
pl
ur
ic
ce
at
-r.
or
..
Ti
po
ta
si
ni
tio
um
ns
an
...
Re
d
pl
co
as
ns
tic
tr u
...
ct
in
g
th
e
b.
..
1.
UNIVERSITY of IOWA Carver College of Medicine
4. Early clinical outcomes of MRI-guided, conformal
brachytherapy have been promising. The following
statements are true EXCEPT:
...
do
..
i..
.
ed
oi
nt
en
d
m
m
e
re
co
...
rr
en
t
cu
na
lP
en
tio
nv
co
Th
of
...
pa
lu
m
e
in
g
vo
se
8% 7%
2%
us
he
n
W
e
Th
Th
e
im
pr
ov
5.
7%
A
4.
76%
en
ts
3.
The improvements of rectal, bladder and sigmoid sparing
are dependent on the size of the high risk CTV.
The dose volume parameters of conformal brachytherapy
should be reported using the radiobiologically equivalent
dose in 2 Gy fraction in order to account for the EBRT dose
contribution.
When using current intracavitary applicators for cervical
cancer patients who are eligible for curative brachytherapy,
clinicians can generally achieve 100% coverage of the HRCTV with the prescription dose..
A conventional Point A plan is recommended as the initial
dwell time condition when doing volume-based treatment
plan optimization for cervical cancer brachytherapy.
The recommended dose limits for rectum and sigmoid (D2cc
< 70-75Gy) are lower than that of bladder (D2cc < 90Gy)
while the dose limits recommended by ICRU 38 for the
rectum and bladder points are the same.
do
2.
em
1.
UNIVERSITY of IOWA Carver College of Medicine
v  References
1.
Nag S, et al. The ABS recommendations for HDR brachytherapy for carcinoma of the cervix. Int J Radiat Oncol Biol
Phys 2000;48:201-211
2.
Haie-Meder C et al. Recommendations from GYN GEC-ESTRO Working Group (I): concepts and terms in 3D image
based 3D treatment planning in cervix cancer brachytherapy with emphasis on MRI assessment of GTV and CTV.
3.
Potter R et al. Recommendations from GYN GEC-ESTRO Working Group (II): concepts and terms in 3D image-
4.
Hellebust TP et al. Recommendations from GYN GEC-ESTRO Working Group: considerations and pitfalls in
commissioning and applicator reconstruction in 3D image-based treatment planning of cervix cancer
5.
Tanderup K et al. Consequences of random and systematic reconstruction uncertainties in 3D image based
6.
Kim Y et al., Evaluation of Artifacts and Distortions of Titanium Applicators on 3.0-Tesla MRI: Feasibility of
Radiother Oncol 2005;74:235-245
based treatment planning in cervix cancer brachytherapy-3D dose volume parameters and aspects of 3D imagebased anatomy, radiation physics, radiobiology. Radiother Oncol 2006;78:67-77
brachytherapy. Radiother Oncol 2010;96:153-160
brachytherapy in cervical cancer. Radiother Oncol 2008;89:156-163
Titanium Applicators in MRI-Guided Brachytherapy for Gynecological Cancer. Int J Radiat Oncol Biol Phys
2011;80:947-955
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