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Total Marrow Irradiation with Helical Tomotherapy along the entire Patient ’s Axis : a Planning Technique to Merge Helical Dose Distributions producing Uniform Dose in the Junction Region. M. Zeverino, S. Agostinelli, G. Taccini, F. Cavagnetto, S. Garelli, M. Gusinu, - PowerPoint PPT Presentation
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TOTAL MARROW IRRADIATION WITH HELICAL TOMOTHERAPY ALONG THE ENTIRE PATIENT’S AXIS: A PLANNING TECHNIQUE TO MERGE HELICAL DOSE DISTRIBUTIONS PRODUCING UNIFORM DOSE IN THE JUNCTION REGION
M. Zeverino, S. Agostinelli, G. Taccini,
F. Cavagnetto, S. Garelli, M. Gusinu,
S. Vagge, S. Barra , R. Corvò
National Institute for Cancer Research
Genova- ITALY
OUTLINES TMI rationale and its potential over TBI
treatments TMI treatment technical issues Patient selection and treatment approach The strategy to overcome limits and delivery
a “Full TOMO” treatment Dose junction manipulation Treatment delivery QA
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OUTLINES TMI rationale and its potential over TBI
treatments TMI treatment technical issues Patient selection and treatment approach The strategy to overcome limits and delivery
a “Full TOMO” treatment Dose junction manipulation Treatment delivery QA
M. Z
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TMI RATIONALE
Leukemia relapse (LR) cause of failure after allogeneic stem cell trasplantation
LR first cause of death for patient with advanced hematologic diseases
Total Body Irradiation (TBI) dose escalation may reduce LR ratio but is associated with higher toxicity
TMI has the potential to fulfill a dose escalation protocol and reduce the dose delivered to the organs at risks
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DOSE VOLUME HISTOGRAMS TBI VS TMI
Typical TBI Dose Volume Histogram
vs.
TBITMI
TMI –
H&
N
TMI –
Tru
nk
Entire target STILL receives full doseCritical Organ receives LESS dose
9 entries in PubMed for TMI with HT:•Hui SK et al. Feasibility study of helical tomotherapy for total body or total marrow irradiation. Med Phys. 2005•Wong JY et al. Image-guided total-marrow irradiation using helical tomotherapy in patients with multiple myeloma and acute leukemia undergoing hematopoietic cell transplantation. IJROBP 2009
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OUTLINES TMI rationale and its potential over TBI
treatments TMI treatment technical issues Patient selection and treatment approach The strategy to overcome limits and delivery
a “Full TOMO” treatment Dose junction manipulation Treatment delivery QA
M. Z
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HOW TO DEAL WITH THE COUCH Y LIMIT?
Maximum couch travel ability of about 160 cm
• Treatment has to be split in two segments: Upper body TMI (UTMI) Lower body TMI (LTMI)
• Two different treatment approaches: To treat lower limbs with LINAC
Extended SSD AP/PA technique 4 fixed fields (minimum) with at least 2 junctions in
addition To treat lower limbs with TOMO
FFS oriented Single junction
• A method for matching fields should be used
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OUTLINES TMI rationale and its potential over TBI
treatments TMI treatment technical issues Patient selection and treatment approach The strategy to overcome limits and delivery
a “Full TOMO” treatment Dose junction manipulation Treatment delivery QA
M. Z
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PATIENT SELECTION
15 patients (10 M, 5 F) from 07/2009 to 06/2010
Median age 35 y (range 18 y – 55 y) 10 patients with acute myeloid leukemia
(AML) 5 in relapse status 5 in second remission
5 patients with acute lymphoid leukemia (ALL) 3 in relapse status 1 in second remission 1 in third remission
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TREATMENT APPROACH @ IST TBI + TMI
Day 1 Day 2
TBI 2 Gy (x2)
Day 3 Day 4
TBI 2 Gy (x2)
TBI 2 Gy (x2)+ + +
TMI 2 Gy (x1) =
TBI + TMI 14 Gy
time
OUTLINES TMI rationale and its potential over TBI
treatments TMI treatment technical issues Patient selection and treatment approach The strategy to overcome limits and delivery
a “Full TOMO” treatment Dose junction manipulation Treatment delivery QA
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MATCHING UTMI AND LTMI CT DATA SETS
Upper body HFS oriented (from vertex to knees)
Lower body FFS oriented (lower limbs including knees)
Two CT scans
– Whole body CT = lower body images are mirrored and properly matched with upper body images
– Lower limbs CT = original images of lower body
Two CT data sets
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LTMI planned on the lower limbs CT data set
2
Generation of a “twin” LTMI plan on the whole body CT data set
3
UTMI planned on the whole body CT data set with PTV going from vertex to knees
1
MATCHING UTMI AND LTMITREATMENT PLANNING
H&N
Trunk
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LTMI easy to plan (rounded PTV, no OARs)
LTMI plan features: Fixed number (50) of
iterations allowed No changes of dose
constraint during optimization
Plan saved as protocol LTMI protocol was loaded on
the whole body CT data set providing identity between structures
tLTMI dose distribution was then calculated with the same fixed number of iterations
DVH comparison to assess dose identity
• “Modified” γ index (1 % dose/ 1% volume)
• Plans are defined twins only if for >99% of points γ<1
Metho
d
EvaluationTWIN LTMI PLAN GENERATION
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FULL HELICAL TMI DOSE DISTRIBUTION
Finally UTMI and tLTMI plans can be summed on the same CT data set
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OUTLINES TMI rationale and its potential over TBI
treatments TMI treatment technical issues Patient selection and treatment approach The strategy to overcome limits and delivery
a “Full TOMO” treatment Dose junction manipulation Treatment delivery QA
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PRODUCING UNIFORM DOSE IN THE JUNCTION REGION A couple of transition volumes were used to improve dose uniformity in the abutment
region for UTMI, LTMI and tLTMI plans by replacing the PTV segments PTV Stop replaced the last two segments for UTMI and the first two segments for LTMI PTV Trans replaced the two PTV segments preceding and following PTV Stop for UTMI
and LTMI, respectively
Optimization tips:• PTVStop is a RAR (zero dose requested)• PTVTrans is a PTV (acting as a dose modulator)
UTMI LTMI
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JUNCTION DOSE EVALUATION
Overall 3D dose distribution allows to evaluate calculated dose in the abutment region by means of:
DVH
Dose profile
Our policy allows maximum dose inhomogeneity of ± 10% of prescribed dose. Otherwise LTMI is replanned acting on the
dose constraints of both PTVStop and PTVTrans
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JUNCTION DOSE EVALUATION:TOMO VS LINAC
TOMO LINAC
Static fields dose junction
region
TMI dose junction region
Regions of < 50 % of prescribed
dose
“Full TOMO” TMI features:• Easy to deliver (quick setup, no patient shifts)• More conformal (sparing of lower limbs vessels)
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JUNCTION DOSE EVALUATION:TOMO VS LINAC
TOMO LINAC
Static fields dose junction
region
TMI dose junction region
Regions of < 50 % of prescribed
dose
“Full TOMO” TMI features:• Easy to deliver (quick setup, no patient shifts)• More conformal (sparing of lower limbs vessels)
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JUNCTION DOSE HOMOGENEITY:TOMO VS LINAC
“Full TOMO” junction- 2% Dmin+8% Dmax
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JUNCTION DOSE HOMOGENEITY:TOMO VS LINAC
TOMO – Linac junction (NO GAP)- 14% Dmin+10% Dmax
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JUNCTION DOSE HOMOGENEITY:TOMO VS LINAC
TOMO – Linac junction (5 mm GAP)- 28% Dmin+3% Dmax
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JUNCTION DOSE HOMOGENEITY:TOMO VS LINAC
TOMO – Linac junction (5 mm OVERLAP)- 10% Dmin+34% Dmax
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JUNCTION DOSE HOMOGENEITY:TOMO VS LINAC
JunctionDmin
(% of target dose)
Dmax (% of target
dose)
Dose Inhomogeneity
Full TOMO -2 % +8% 10%
TOMO – Linac (NO GAP)
-14% +10% 24%
TOMO – Linac (5 mm GAP)
-28% +3% 31%
TOMO – Linac (5 mm OVERLAP)
-10% +34% 44%
1. Inverse planning allows to obtain a more uniform dose distribution in the overlapping area
2. Target over- or under-dosage can be easily avoided
3. These are calculated values!4. MV/kVCT registration process will affect dose
uniformity in the overlapping area
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JUNCTION DOSE HOMOGENEITYRESULTS
StructureMean D5
(cGy)Mean D95
(cGy)Dmean (cGy)
HI
PTV STOP211
(201 – 218)194
(189 – 201)203
(196 – 210)
0.08(0.05 – 0.13)
PTV TRANS212
(203 – 218)187
(182 – 191)200
(195 – 209)
0.13(0.07 – 0.18)
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OUTLINES TMI rationale and its potential over TBI
treatments TMI treatment technical issues Patient selection and treatment approach The strategy to overcome limits and delivery
a “Full TOMO” treatment Dose junction manipulation Treatment delivery QA
M. Z
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PLAN VERIFICATION
Dose point verification A1SL ion chamber &
Cheese Phantom Target sites (i.e. bone
marrow) 3% ∆D
2D dose verification GafChromic EBT/EBT2 Anthropomorphic
phantom (head and chest)
Lung equivalent tissue slabs
γ (3%/3mm)
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MV-KV REGISTRATION Results from the first 8 treated patients:
Treatment setup (TS) = Observed Shift – Averaged Shift < 4 mm If 4 mm < TS < 6 mm, physician review and evaluation If TS > 6 mm, patient repositioning
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IN VIVO DOSIMETRYIn vivo dosimetry = assessing the accuracy of dose delivered in the
field junction
Gafchromic EBT2• Two stripes of approximately 10 cm long and 2 cm wide• Placed on the skin according to the tattoo individuating the junction
MOSFET5 detectors placed on the skin 1 cm apart in the long direction according to the tattoo individuating the junction
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SOME NUMBERS…
Organ Median Dose reduction
Standard Deviation
Brain 45,5% 4,6%Left Parotid 30,3% 11,5%
Right Parotid 29,6% 10,3%Oral Mucosa 35,8% 9,2%
Larynx 56,4% 4,9%Thyroid 43,3% 9,6%
Left Lung 44,3% 2,7%Right Lung 47,5% 4,3%
Heart 45,1% 2,1%Liver 47,0% 4,1%
Left Kidney 56,8% 5,2%Right Kidney 60,5% 2,1%
Bowel 52,2% 3,4%Male Gonads 80,7% 12,3%
PTVValue Mean (%) Range (%)D95 93,3 91,9 - 94,2D90 95,7 94,1 - 96,7D5 102,9 101,7 - 103,8
MF Time (min)UTMI (FW 5 & pitch 0.287)
mean 1,49 20,5range 1,33- 1,83 17,5 - 23,5
LTMI (FW 5 & pitch 0.287)mean 1,8 9,0range 1,73 - 2,00 6,1 - 12,6
Legenda:• D95 = dose received by 95 % of PTV volume• D90 = dose received by 90 % of PTV volume• D5 = dose received by 5 % of PTV volume
Considerations:• Organ sparing is achievable in terms of median dose reduction (i.e. dose delivered to 50% of organ volume)• Small organs are penalized because of technical parameters of treatment• Optimal PTV coverage and homogeneity• Mean overall beam-on time < 30 min
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REMARKS AND CONCLUSIONS
Full helical dose distribution is true as long as dose identity between LTMI and tLTMI exists
Different solutions can be adopted for producing uniform dose in the junction through inverse planning
In vivo dosimetry is mandatory to assess the dosimetric impact of the patient shifts on the junction
Patient alignment process may cause over- or under-dosage to PTV. Split the treatment at the knees (= lack of bone marrow)
On a total of 17 patients underwent TMI with HT (first patient July 2009), 11 were treated using the presented technique
Treatments well tolerated (1 severe nausea episode) Short median FU (7 months) . 12/17 patients are
currently alive in CR
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