• Radiotherapy in an operating theatre
• The goal in direct irradiation of the target
• Simply move normal tissues out of the way
• How is this accomplished?
•
•
•
•
Special OR (vault) with traditional linac installed
Surface Brachytherapy Style (mobile HDR unit)
Mobile Orthovoltage or “Superficial” machines
Mobile Electron Linac’s (AAPM TG-72)
• 1905: Spanish doctors used IORT to attempt to treat residual
tumor after surgical resection
• 1915: German
• IORT treatment with "orthovoltage" x-rays gained advocates in
930s and 40's
• results were inconsistent.
• The x-rays penetrated beyond the tumor bed to the normal tissues
• poor dose distributions and
• took a relatively long time to administer.
• The technique was largely abandoned in the late 1950s
• advent of megavoltage radiation equipment enabled the delivery of
more penetrating external radiation.[5]
• 1965: Betatron IORT began in Japan (Kyoto University)
• patients treated with electron beam
• improved dose distributions,
• limited penetration beyond the tumor and
• delivered the required dose much more rapidly.
• Other Japanese hospitals initiated IORT using electron beams
• Generally generated from linear accelerators.
• At most institutions, patients were operated on in the OR and transported to
the radiation facility for treatment.
• Japanese IO“E”RT technique:
• relatively large single doses of radiation were administered during surgery
• most patients received no follow-up external radiation treatment
• the early Japanese results were impressive
• particularly for gastric cancer
• 1976: Howard University
• Howard built a standard radiation therapy facility with one room that could also be
used as an OR
• followed the Japanese protocol of large, single dose
• Because the radiation equipment was also used for conventional therapy, the
competition for the machine limited the number of patients that could be scheduled for
IORT.
• 1978: Massachusetts General Hospital started an IORT program
• MGH doctors opted not to remodel a radiation therapy room for surgery
• scheduled one of their conventional therapy rooms for IOERT one afternoon a week
• performed surgery in the OR and transported the patient to the radiation therapy
room during surgery.
• conventional fractionated external beam irradiation was added to the IOERT dose
(prior to or subsequent to the surgery)
• However, about 30-50% of the patients planned for IORT are found unsuitable at the
time of surgery
• The risks and complexities of moving a patient during surgery remain as well.
• Europe began adopting these methods in the1980’s
•
1979: the National Cancer Institute (NCI) started an IOERT program
• approach combined maximal surgical resection and IOERT alone
• IOERT fields were often very large, sometimes requiring two or three adjacent and overlapping fields to cover
the tumor site.
•
NCI results for these very large tumors were not encouraging…
• but showed the combination of aggressive surgery and large IOERT fields had acceptable toxicity.
• Also introduced several technical innovations
• television for simultaneous perioscopic viewing of the tumor by the surgical team.
•
1981: Mayo Clinic built an operating room (OR) adjacent to the radiation therapy department
• patients 1st surgery in regular OR, if found suitable a 2nd surgical procedure was scheduled in the OR adjacent to
radiation facility.
• more efficient use of their radiation therapy machine at the cost of subjecting patients to a second surgery.
•
Mayo Clinic remodeled an OR and installed a conventional radiation therapy machine
• clinic now routinely treats over 100 IORT patients per year.
•
1985: Siemens Medical Systems offered a specialized linac for IOERT designed to be used in the OR
• weighed more than 8 tons and required about 100 tons of shielding.
• 7 of these specialized units were sold.
•
Dedicating an OR to IORT…
• increases the number of patients that can be treated
• eliminates the risks of double surgeries and complex logistics involved in moving patients form OR to therapy
room and back to OR.
• Remodeling an OR and purchasing an accelerator is expensive.
• IORT is restricted to that one, specialized OR
• 1982: the Joint Center for Radiation Therapy (JCRT) at Harvard Medical School
attempted to reduce the cost of performing IORT in an OR by using orthovoltage
• similar the approach used in Germany in 1915.
• shielding costs and the cost and equipment weight are improved over conventional electron accelerators
• dose distributions are inferior, treatment times are longer, and bones receive a higher radiation dose.
• 1998: University College London develop TARGIT (TARGeted Intra-operative
radioTherapy)
• treatment of the tumour bed after lumpectomy of breast cancer
• uses a miniature and mobile X-ray source (max. 50 kV) in an isotropic distribution.
• In breast cancer is also used (IO)-Brachytherapy with MammoSite
• Despite the logistical and cost considerations, interest is growing
• Over 200 other centers in over 27 countries worldwide perform IORT
• 70 centers in Japan and the U.S.
• 1998: International Society of IORT (ISIORT) is formed to foster the scientific and clinical
development of IORT
• ISIORT has over 1000 members from more than 20 countries
• meets every two years.
• 2000: Boston Meeting of ISIORT established an IOERT Protocol Study Group.
• Linear Accelerators
• Dedicated
• Mobile
• HDR Brachytherapy
• Ir-192
• Low energy X-ray
• Intrabeam
• Xoft
• Simply a linac vault dedicated to IORT
• Needs OR conditions
• Falls under compliance needs of both OR and radiotherapy vault
• Sterile environment + shielding
• All standard Linac QA requirements apply
• Typically only accelerate electrons
• Use cones to control scattered electrons
• AAPM’s TG-72 governs these systems
• (a) The Mobetron unit being moved to the operating room.
• The gantry is in the “transport mode” configuration.
• (b) The unit in its full upright “treatment mode” position
• The Novac7 in its normal
mode for treatment.
• (a) Example of accessories
used by mobile IORT unit
• (1) the components of a
modified Bookwalter clamp
• (2) sterile gantry cap
• (3) mirror ring
• (4) electron applicators
• (5) lead shields
• (6) Lucite bolus
• (b) The sterile cap being
placed on the gantry for
treatment.
• (c) The electron applicator
• with a bolus attached to its
end with Steri-Strips
• (a) Unit in the
normal position at a
gantry angle of
zero.
• (b) Unit positioned
at an arbitrary
gantry angle
• Note alignment of the
beam stopper with
the gantry. The beam
stopper is marked
with red arrows.
• (a) The Novac7 mobile IORT unit in the normal position with the beam
stopper placed directly below the gantry.
• Note that an electron applicator is attached the gantry and is docked on top
of a phantom, illustrating a typical setup for quality assurance.
• (b) Close-up of the beam stopper in transit
• (a) The electron
applicator, in contact with
the tumor bed, is rigidly
clamped to the surgical
bed using a modified
Bookwalter clamp.
• (b) The gantry being
moved for soft docking to
the applicator.
• (c) The LED display and
electron applicator. The
green light in the center
of the display indicates
that proper alignment has
occurred and the gantry
is properly docked. Note
the air gap (4 cm ± 1
mm) between the end of
the gantry and the top
surface of the applicator.
• (a) The accelerator
beam collimation
system and electron
applicator before
docking.
• (b) The harddocking mechanism.
• (c) The docked unit,
with the electron
applicator in contact
with the tumor bed.
•
•
Typical procedures required for acceptance testing of a mobile IORT unit:
Radiation Survey
• Ensure no individual is exposed to radiation levels in violation of regulations, and verify the normal operation of
emergency off switches.
•
Mechanical Inspection
• Verify the movement range, speed, control, and accuracy of the gantry and beam stopper.
• Verify the physical sizes of all applicators.
•
Radiation Safety
• Verify dose attenuation through the beam stopper.
•
Beam Characteristics
• Verify beam energy, surface dose, dose rate, field flatness, symmetry, and X-ray contamination according to
specifications.
• Verify beam energy constancy for all gantry angles.
•
Dosimetry System
• Verify the precision of the backup MU chamber, the linearity and reproducibility of the MU chambers, and the
dosimetry interlocks.
•
Control Console
• Verify the normal function of each control on the control console.
•
Docking System
• Verify the normal function of the optical docking system.
•
Options and Accessories
• Verify normal function.
•
Safety Features
• Examine all safety features (emergency off, rad-on light, and audible warning sounds.)
• Typical arrangement used for quality
assurance for the Mobetron.
• (a) The mobile unit with the specialized
quality assurance electron applicator
attached to it.
• (b) Close-up of the specialized
applicator.
• A dedicated plastic phantom, shown
without inserts, is mounted at the bottom of
the applicator.
• (c) Attachment of the applicator to the
gantry.
• (d) Placement of energy and depthspecific inserts into the
• dedicated phantom.
• (e) The applicator, ready for
measurement.
• The quality assurance electron applicator,
phantom, and inserts are supplied with the
unit.
• J. R. Palta, P. J. Biggs, D. J. Hazle, M. S. Huq, R. A. Dahl, T. G.
Ochran, J. Soen, R. R. Dobelbower, and E. C. McCullough,
"Intraoperative electron beam radiation therapy, technique,
dosimetry, and dose specification, report of Task Group 48 of
the radiation therapy committee, American Association of
Physicists in Medicine," Int. J. Radiat. Oncol. Biol. Phys. 33, 725746 (1995).
• The treatment is performed at the time of surgery, when the
target area (the tumor bed) is exposed and the applicator can
be placed directly over the target
• Organs at risk may be retracted and shielded as necessary
• The applicator can be used in virtually any anatomic location
• e.g. treatment of colorectal malignancies where the tumor bed is often
inaccessible to the cones of a linac based system
• Avoids cold spots and hot spots
• often encountered when using the electron beam approach due to angle
of beam incidence and field matching
• Convenience and cost effectiveness
• Iridium (192) based afterloaders…
• GammaMed (Varian Medical Systems, Inc)
• VariSource (Varian Medical Systems, Inc)
• microSelectron (Nucletron/Elekta)
• The Harrison-Anderson-Mick applicator
• 130-cm source guides embedded at 1-cm spacing in 8-mm thick silastic
rubber
• 5 mm from the center of catheter to front, and 3 mm to back (to gain
flexibility)
• 2 to 24 catheters
• 22-cm long (can treat up to 20 cm x23 cm)
• Prescription point 1 cm away from source plane (0.5 cm from the surface)
• Physicist takes oral (rather than written prescription)
• Prescription details should be repeated by physicist and
confirmed by physician
• Prescription includes:
• number of channels (width)
• length (number of stopping positions)
• dose and prescription point(s)
• homogeneous dose is desired throughout the treatment
• dose ranges between 15 - 20 Gy @ 5 mm in tissue
• lower dose for pediatric cases
• 7.5 -12.5 Gy
• lower dose also used if IORT is combined w/ EBRT
• 10 -12.5 Gy
• Breast IORT: 20 Gy at 1 cm in tissue
• higher dose prescription has been reported in the literature
• 30 Gy for biliary / hepatic treatments
• occasionally, non-uniform dose and irregular treatment
geometry
• Usually, a set of plans are created ahead of time
• Library of “pre-plans” encompases majority of treatment scenarios
• Standard dosimetric systems for brachytherapy still apply
• Manchester
• TG-43
• Acuros BV
• Live planning is becoming an option
• Varian “Vitesse” for prostate
• Applicable to IORT ?
• Intrabeam
• Xoft
• Designed for mobile electronic brachytherapy.
• Perform IORT treatment in OR, with no special radiation
shielding requirements.
• Manufactured by “Carl Zeiss Surgical” (Germany)
• Acquired Intrabeam as the asset of Photoelectron Corp, USA
(bankrupted.) (bankrupted.)
• Received FDA approval for intraoperative treatment in 1999.
• Received approval in 2005 for “whole body use”
• skin, gynecological applications
• Operates at 50kVp (breast)/40kVp (brain)
• 40µA.
X-ray probe (XRS 4 unit)
Miniature X-ray source
10cm long 3.2mm diameter probe
Gold target
Gold target
Operates under 50kVp/40 μA or
40kVp/40 μA.
• Low energy X-rays emitted
isotropically
• Internal Radiation Monitor (IRM)
•
•
•
•
•
•
• Continuously monitor the treatment
delivery
• It measures of the radiation that reeneters the probe
4
3
1
2
• 1. Beryllium Probe tip allows x-ray to pass through
• Coated with a film of nickel and titanium nitride.
• 2. Made of Mu-metal. Shield the Earth’s magnetic field (0.5 G)
• Sensitivity (0.06mm/G)
• 3. No high voltage outside of tube housing
• 4. Internal radiation monitor
• The first HVL is 0.11 mm Al for
breast treatment (50kVp)
• 1.11 mm Al (23.5,keV) at 10 mm
depth in Solid Water.
• The first HVL is 0.10 mm Al for
brain treatment (40kVp)
• 0.71 mm Al (19.9keV)at 10 mm
depth in Solid water.
• Manufacturer provided full set of radiation
shielded QA instruments
• PDA(Photodiode Array) PDA(Photodiode Array)
• Contains five photodiodes at orthogonal Positions
• Isotropy check
• PIACH (Probe adjuster/ionization chamber
holder)
• Measures and adjusts the straightness of the probe
manually
• Inbuilt thermometer for temperature/pressure
correction
• Mount for ionchamber
• High precision water phantom (optional/send
back to factory to QA)
• To perform independent verification of the depth
dose and Dose distribution
• Radiation shielded with lead glass.
• Mechanical positioning accuracy of +/- 0.1mm
• A set of spherical applicators to
adapt to varying tumor size
• 1.5cm to 5.0cm
• 5mm increment
• Made of polyetherimide
• (C37H24O6N2)
• Reusable up to 100 sterilization
cycles,
• biocompatible and radiation
resistant
• can be steam sterilized
• Cerebral metastases
• Gastrointestinal cancer
• Endometrial cancer
• Spinal metastases
• Oral cancer
• Skin cancer
•
•
•
•
•
•
•
•
•
•
1) Applicators sterilized and kept in the OR Applicators sterilized and kept in the OR
2) QA procedure must be performed within 36hrs of each treatment.
3) Lumpectomy procedure
4) Assess the cavity size and select the proper applicator
5) XRS probe and the Intrabeam stand are covered in a sterile polyethylene bag
6) Secure the applicator to the XRS probe
7) Position the applicator in the lumpectomy cavity (Surgeon/RadiationOncologist)
8) If necessary, the chest wall and skin can be protected (95% shielding) by radio-opaque tungstenfilled polyurethane caps. (avoid significant skin doses that occur with distances of <1 cm
9) Place tungsten-filled drape for shielding
10) Treatment plan
• Entry of treatment parameters
• Does not require imaging
• Some centers use ultrasound to document the distance from the skin
•
11) Treatment parameter verification
• Applicator size
• Prescription dose
• Treatment depth
•
•
•
12) Treatment delivery time is about 20 to Treatment delivery time is about 20 to 55mins
13) Radiation survey
14) Evaluation and documentation of Treatment records
• Designed after Mammosite/Ir-192 HDR
• Similar Balloon placement / removal
• Same prescribed doses / PTV definitions
• Similar treatment time lengths (~10 min)
• Clinical Differences
• Imaging
• Treatment Planning
• Delivery
•
•
•
•
•
•
FDA Approved in 2002
Placed at time of lumpectomy
Single balloon catheter system
Uses After-loaded Ir-192 HDR Source
PTV defined as 1 cm margin about balloon
3.4 Gy/fr., 10 fractions, BID ( ~ 6 hr.)
• Post Lumpectomy, balloon catheter is inserted into cavity & filled
with saline under ultrasound guidance.
• Balloon is deflated and removed by Rad. Oncologist following
final fraction
• FDA Approved in 2007
• First commercially available, multi-fraction Electronic
Brachytherapy (EBT) System
• 2.3 mm diameter, 50 kVp x-ray source, max 300 µA
• Operator stays in room during treatment
• Shielded by Flexi-shield and Pb Vest or rolling shield
• Electronic Source is calibrated before each fraction.
• NIST Traceable Well chamber
• Disposable Source
• Water cooled and easily disposed of
• X-Ray Source Assembly
• Semi-flexible
• Water cooled
• 25 cm or 50 cm length
• 5.4 mm diameter
• Eavg ≈ 27kV
• Characteristic Xrays
• Tungsten
• Yttrium
• Silver
• Follows TG 43 Protocol
• Calibrated in terms air
kerma strength (Sk )
• Performed in well type
chamber
• Traceable to national
standards
• Sk up to 1400 Gy cm2h-1 @
50kVp and 300μA
• Steep dose gradient
• Beneficial for sparing tissues further away
• Problematic for tissue closer to the source
• Increased anisotropy
• Uniform dose distributions require multiple dwell positions
• Similar to HDR afterloader
• Source programmed to multiple dwell positions and times to deliver
conformal treatment.
• Planning
• Varian’s “BrachyVision” TPS used to generate treatment plans
• Plans converted to controller friendly formatting
• Plans are transferred to controller via USB flash drives
• Designed after Mammosite/Ir-192 HDR
• Addition Features of Xoft Balloon
Drainage Port Valve
Multiple Balloon
Shapes and Sizes
Multi-Lumen Extrusion
Balloon Inflation Valve
Radiation Probe
Lumen with
Inserted Stylet
Drainage Holes x 7
• Designed after Mammosite/Ir-192 HDR
Comparison of Dose Rate vs. Depth in Water for Various Sources
1.E+03
50 kV
1.E+02
50 kV MCNP5
Pd 103
I 125
Dose Rate (cGy/min)
1.E+01
Ir 192
1.E+00
1.E-01
1.E-02
1.E-03
1.E-04
0.0
1.0
2.0
3.0
4.0
Radius (cm)
5.0
6.0
7.0
8.0
• Similarities Between Axxent and Mammosite
• Both can use Varian’s BrachyVision & Nucletron’s Plato
• Both use CT Baised 3D treatment planning
• Differences
• Imaging
• Dosimetry Formulations
• Dose Distributions
• Differences: Imaging
• Mammosite filled with contrast vs. Axxent Balloon walls made with contrast
• Contrast CANNOT be used to image Axxent Balloon
• Soft X-Rays can be randomly attenuated by as much as 16%
• Axxent needs imaging catheter to translate from planning software to
Microsoft Excel.
• Patient positioning less critical for Mammosite
• EBT Technology currently limits flexibility
• Differences: Dose Formulations
• Line Source (Mammosite)
D(r,) = SK  gL(r) GL(r,)
F(r,)
GL(r0,0)
D(r,) : dose rate to water at point P(r,
SK
: air kerma strength

:dose rate constant
gL(r) : radial dose function
GL(r,) : geometry function (line source approximation)
F(r,) : 2-D anisotropy function
• Differences: Dose Formulations
• Point Source
D(r) = SK  gP(r) GP(r)
an( r)
GP(r0)
D(r,) : dose rate to water at point P(r
SK
: air kerma strength

:dose rate constant
gP(r) : radial dose function
GL(r,) : geometry function (point source approximation)
an(r) : 1-D anisotropy function
• Differences: Dose Formulations
• Axxent Source (Combination)
D(r,) = SK  gP(r) r2 F(r,)
r 02
D(r,) : dose rate to water at point P(r,
SK
: air kerma strength

:dose rate constant
gP(r) : radial dose function
F(r,) : 2-D anisotropy function
And simplified geometry function!
• Differences: Dose Distributions
• Axxent
40 kV Probe in
BrachyVision®
Film 40A01
D (Gy)
D (Gy)
X-Ray Source
Delivered X-Ray Distribution On Film
34
Red
34
Red
17
Orange
17
Orange
10.2
Yellow
10.2
Yellow
6.8
Green
6.8
Green
5.1
Blue
3.4
Dark Blue
5.1
Blue
1.7
Magenta
3.4
Dark Blue
1.7
Magenta
Predicted X-Ray Distribution From
Planning System
• Differences: Dose Distributions
• Mammosite
• Differences: Dose Distributions
• Differences: Dose Distributions
• Differences: Dose Distributions
• Differences: Dose Distributions
• Advantages
• Side-effects limited to area near treatment site as opposed to whole
breast
• Less invasive then multiple needle method
• Cosmetically Advantageous
• Fewer fractions then external beam therapy
• Advantages
• Side-effects limited to area near treatment site as opposed to whole
breast
• Less invasive then multiple needle method
• Cosmetically Advantageous
• Fewer fractions then external beam therapy
• Disadvantages
• Patient selection is extremely important
• Good communication between surgeon and radiation oncologist is critical.
• Patient Study Selection Criteria
• At least 45 yrs of age
• Cavity Size > 3 cm diameter
• At least 7 mm (5 mm for Mammosite) separating balloon from skin
surface.
• No serious medical illness or condition
• Not pregnant or breast-feeding
• No Collagen-vascular disease
• Non-extensive intraductal component
• No Lobular infiltration
• Tumor classified as Tis,T1, N0, M0 (AJCC Classification)
Dickler A (2007) Technology Insight: MammoSite®—a new device for delivering brachytherapy
following breast-conserving therapy
Nat Clin Pract Oncol 4: 190–196 doi:10.1038/ncponc0739
Pre-surgery
Post 30 days
Post 5 months
• Mammosite
• Advantages
• Uses Ir-192
• Mammosite
• Advantages
• Uses Ir-192
• Disadvantages
• Uses Ir-192
• Axxent
• Advantages
• Safer then Isotopes
• More Mobile
• Less Shielding (No “Vault” needed)
• No NRC
• More Patient Friendly
• Axxent
• Advantages
• Safer then Isotopes
• More Mobile
• Less Shielding (No “Vault” needed)
• No NRC
• More Patient Friendly
• Disadvantages
• Cost
• Less reliable then an isotope
• New
• EBx dose rate > Ir-192 Dose rate
• TG-43 fails to accurately predict bone’s absorbed dose for low energy photons
• Possibly 4-5 times greater then TPS predicted for eBx
• This increase may be limited to 1-2 mm of bone surface
• 2-4% Ir-192 cases show rib fracture
• None seen in eBx after 1 yr
• 5.5% of eBx cases have demonstrated fat necrosis
• A result common in increased %V150 and %V200 doses
• Skin doses for Ir-192 may be overestimated by 10-15%
• This may also be the case for eBx
• Tissue Heterogeneity considerations are needed for the advancement of
brachytherapy techniques and technology
• Treatment plans for 35 patients were analyzed
• Mostly Post-Menopausal Caucasians >50 yrs
• Resected T1 invasive ductal carcinoma < 2 cm dia
• BrachyVision and Plato TPS were utilized
• AAPM TG-43 Formalism w/o heterogeneity
• Prescription dose was 3.4 Gy at 1 cm beyond the balloon surface for all plans.
• DVH metrics were used to compare:
• PTV percentage volumes covered by 90% (V90), 100% (V100), 150% (V150) and 200%
(V200) of the prescription dose
• Volume of heart covered by 5% (V5) of prescribed dose
• Volume of lung covered by 30% (V30) of prescribed dose
• Volume of uninvolved ipsilateral breast covered by 50% (V50) of the prescription dose
• Maximum skin and rib doses were also determined.
• T-Tests were used to compare mean percentages between groups
• Comparison between the total nominal dwell times (TNDT) was also performed
• TNDT is the summation of dwell times at all planned dwell points
• PTV coverage very similar for all plans
• No statistical differences in mean PTV V100.
• Mean percentage of PTV in high dose regions (V150, V200, V300) is
considerably higher in eBx plans compared to Ir-192
• The mean maximum skin dose was generally
• ~10% less in eBx plans compared to Ir-192 plans.
• The mean maximum rib dose differences between plans was minimal
• Lung, heart and breast doses were dramatically lower in eBx plans
compared to Ir-192 plans (Table 1)
• TNDT trended linearly with PTV volume as well as balloon fill volume for a
3.4 Gy prescription
• 50% of data points fell within
• 7% of the linear regression fit for balloon volume
• 5% of the linear regression fit for PTV volume
• 90% of data points are within 13% of the linear fit for both volumes
68.26
19.52
5.15
1.1
24.85
18.72
3.38
3.65
3.09
2.78
24.32
16.68
9.38
1.12
7.21
6.5
1.75
2.73
1.09
1.54
Ir-192 %V300
0.47
0.64
eBx %V300
3.5
3.41
Ir-192 %V200
7.98
6.16
eBx %V200
22.98
7.23
Ir-192 %V150
35.1
8.59
eBx %V150
48.76
7.86
Ir-192 %V100
90.58
5.11
eBx %V100
89.8
4.46
Ir-192 %V90
97.28
3.05
eBx %V90
95.45
3.27
Mean
SD
Heart %V5 Left Side
Treatment (n=23)
Ipsilateral Lung
%V50
Ipsilateral Breast
%V50
Max Rib Dose
(cGy/Fraction)
Max Skin Dose
(cGy/Fraction)
Ir-192
eBx
Ir-192
eBx
Ir-192
eBx
Ir-192
eBx
Ir-192
eBx
p<0.0001
p=0.0107
p<0.0001
p=0.1663
p=0.1142
p<0.0001
p<0.0001
p<0.0001
p=0.2759
p=0.0003
T-Test
•
•
•
•
Uses pre-plans based on particular balloon and volume
Single fraction APBI
Prescription is 20 Gy to balloon surface
Done in OR during lumpectomy prodecure
Exposure Rate Measurements
@ 1 meter From Source
E
Controller
D
B
C
B
A
A Head
B
C
D
E Feet
3
35
100
36
240
45
45
67
45
132
* 0.5 mm Pb–equiv lap apron
Operator Shield
Hallway
Exposure Rate (mR/hr)
Gonads
Eyes
1m
A Head
B
C
D
E Feet
0.3
0.6
1.8
36
240
0.5
0.8
2.2
59
105
Ir-192 Source
Xoft Source
Ir-192
Xoft Source
Total Bladder Comparison
120
100
Volume (%)
80
60
Xoft Bladder
Ir192 Bladder
40
20
0
0
20
40
60
% Prescription Dose
80
100
120
Total Rectum Comparison
120
100
Volume (%)
80
60
Xoft Rectum
Ir192 Rectum
40
20
0
0
20
40
60
% Prescription Dose
80
100
120
Rectum
Bladder
Significantly higher maximum doses to bladder.
These hot spots could be an issue for serial type
Organs.
• Instantaneous dose rates were measured at operator locations
• Lower than those seen during other Xoft procedures
• Small sample yielded exposure rates on the order of 10-1 mR/h
behind rolling shield
• More measurements needed at common personnel positions and
patient sites
• Designed for skin/ surface treatment
• Xoft Axxent
• produces 50 kVp (~300 mA beam current) bremsstrahlung x-rays with
• A mean energy of 26.7 kV photons.
• Esteya Electronic Brachytherapy
• Miniature 69.5 kVp X-ray source
• PDD’s are comparable for both systems
• 7-7.5% drop-off per mm.
• The available applicator sizes
• Xoft are 10mm, 20mm, 35mm and 50mm
• Esteya 10, 15, 20, 25 & 30 mm diameter.
• The beam
• atness and symmetry over the central 80% of the eld width are within 5%
from the edge of the applicator for both Xoft and Esteya.
• Dose rate for a 35mm applicator
• Xoft and 1.3 Gy/Min
• Esteya are about 3.3 Gy/min
• It exists
• It’s a growing market
• Especially for skin
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Xoft
Mamosite ML
Contura
Savi
• Between 2005 - 2013, University of Florence (Italy).
• Women aged >40 years w/early BC (max tumor of 25 mm)
• Randomly assigned to receive either WBI or APBI via IMRT.
• APBI arm received a total dose of 30 Gy to the tumour bed in five daily fractions.
• The WBI arm received 50 Gy in 25 fxs + boost to tumour bed of 10 Gy in 5 fxs.
• 520 patients were randomised (260 to WBI and 260 to APBI w/IMRT)
• At a median follow-up of 5 years, IBTR rate was 1.5% (three cases) in each group
• The 5-year survival was 96.6% for the WBI group and 99.4% for the APBI group.
• The APBI group presented significantly better acute (p = 0.0001) and late (p =
0.004) toxicity, and cosmetic outcome (p = 0.045).
• No significant difference in terms of IBTR and overall survival was observed
between the two arms.
• APBI displayed a significantly better toxicity profile.
• Appropriate candidates
• 45 years or older, all invasive histologies and ductal carcinoma in situ,
tumors 3 cm or less, node negative, no lymphovascular space invasion, and
negative margins.
• Strongest evidence advocates interstitial brachytherapy and
intensity-modulated radiation therapy
• APBI with moderate evidence to support applicator
brachytherapy or 3DCRT based APBI.
• IORT and eBx should not be offered regardless of technique
outside of clinical trial.
• At this time, there are limited data evaluating eBx as APBI
• Epstein et al. Evaluated 702 patients treated with electronic brachy
• 21% of patients developed acute complications
• 13% chronic toxicities
• 4.6% of patients having significant complications.
• Same group evaluated 146 DCIS patients
• 18% of patients had acute toxicities
• 12% of patients had chronic toxicities
• 7.5% rate of significant complications
• So…no more Xoft IORT for breast
• (unless its’s a new clinical trial)
• What do we do now?
• Back to SAVI? (moderately recommended)
• Start IMRT? (strongly recommended)