1. CYBERKNIFE
SRS & SBRT
P.Mahadev MD DNB
Apollo Speciality Cancer Hospital
Chennai

2. MANAGEMENT AND DELIVERY OF IMAGE
GUIDED HIGH DOSE RADIATION THERAPY WITH
TUMOR ABLATIVE INTENT WITHIN A COURSE OF
TREATMENT THAT DOES NOT EXCEED 5 DAYS

3.  Higher confidence in tumor targeting
 Reliable mechanisms for generating focused, sharply
delineated dose distributions with a rapid dose fall off
 Reliable accurate patient positioning accounting for target
motion related to time dependent organ movement
 IMAGE GUIDANCE AND EFFICIENT TRACKING
MECHANISM
 Longer times than conventional RT, hence patient comfort
is an issue

4. SRS
SBRT
IMRT FOR PROSTATE
SRT

6. 3
4
5 6
2
1

7. Pitch
Yaw Roll

8. Robot is capable of delivering radiation from
different 100 nodes, with each node is capable of
giving a maximum 12 different beams.
Usage of these nodes depends on the treatment room
constraints

10. The table consists of 12 fixed cones and housings of
Fixed and Iris Collimator
Laser Sensor
Collimator sizes(mm): 5, 7.5, 10, 12.5, 15, 20, 25, 30,
35, 40, 50, 60

13.  There are two essential features of the
CyberKnife system that sets it apart from other
stereotactic radiosurgery methods.

14.  radiation source is mounted on a precisely
controlled industrial robot.
 The image guidance system(continuous tracking
system)
 Eliminates the need of gating techniques and
restrictive head frames

15. The Cyberknife treatment delivery is based on the
following tracking systems
 6D_ Skull tracking system
 Fiducials tracking system
 Synchrony tracking system
 X_sight Spine tracking system
 X_sight Lung tracking system

16.  6D_ Skull tracking system:
used for intra-cranial lesions up to C2
Bony anatomy of the skull is used as reference for
tracking

18.  Fiducial tracking system:
used for soft tissues, where gold fiducials
can be implanted.
Minimum of 3 nos. to be implanted

19.  close proximity to the lesion to be treated
 well-separated (by about 1 cm)
 non-overlapping on projections from the in-room x-
ray imagers
Three markers are sufficient for unique spatial
localization, but in practice 4-5 are often placed in
case of loss or suboptimal placement of markers

21. • 790 fiducials
• 85% successfully placed
• 2 Patients developed pneumothorax
• 6 fiducials migrated- 3 in lung, 2 in
liver& 1 in prostate

32. Respiratory-induced
motion of tumors causes
significant targeting
uncertainty
 Lung, liver, pancreas,
Prostate,kidney
Traditional radiation
therapy margins are not
optimized for high-dose
radiosurgery

34. Imaging and Tumor Targeting
 Traditional IGRT daily set-up imaging maybe
inadequate for
sub-millimeter accuracy
Immobilization
Breath Holding

35. Imaging and Tumor Targeting
 Traditional IGRT daily set-up imaging maybe
inadequate for
sub-millimeter accuracy
Immobilization
Breath Holding
Gating

36. option for dynamic tracking without the use of
implanted fiducials.
Tumor localization is accomplished using auto-
mated real-time image segmentation of the in-room
x-ray images based on the contrast of the tumor itself.

37. best used for lesions with sufficient contrast in
density from the surrounding anatomy to be clearly
visualized on both of the in-room x-ray imagers, i.e.,
those located in the lung periphery at least 1.5 cm in
size, and that do not overlap other dense anatomical
structures, such as the spine, diaphragm, and heart in
the projection views

38. Two features to form the basis for accuracy
Fiducials, implanted prior to Optical markers on a special
treatment patient vest

39.  Prior to treatment start: creation of dynamic correlation model
Imaging system takes positions of fiducials at Markers are monitored in
discrete points of time real time by a camera system

40.  Prior to treatment start: creation of dynamic correlation model
Imaging system takes positions of fiducials at Markers are monitored in real time by a camera
discrete points of time system
displacement
displacement
time time

41.  This process repeats throughout the treatment, updating and correcting beam delivery based upon
the patient’s current breathing pattern
displacement
displacement
time time

47.  X-sight Spine tracking system:used to track spine
lesions which are close to spine from C1 to L5&sacrum
 Uses the bony anatomy of spine to track the tumors
in close relation to spine eliminating the need for
fiducials
 X-sight spine is now possible in prone position as well

49.  The appropriate tracking method has to be chosen
during planning itself
 No treatment is possible without planning and proper
tracking method

50.  Treatment planning is done on the CT images of slice
thickness 1mm acquired at 125 kV and 400 mAs with a
pixel size of 512 x 512
 MRI, PET and 3D-Angio images can be used to fuse
with the primary CT images for target and OAR
delineation

51. Planning System (MultiPlan) uses inverse
planning algorithm with following options
1. Conformal Planning
2. Sequential optimization
The system provides the user the option of
using either ray tracing method or Monte Carlo

52.  The mechanical accuracy of the system is 0.12
mm , according to Accuray
 The system maintains sub-millimeter tracking
accuracy, if the patient positions are within the
following limits
Left / Right (Lat) 10 mm
Ant/ Post (Ver) 10 mm
Sup/ Inf ( Long) 10 mm
Roll (Left / Right) 10
Pitch (Head Up / Down) 10
Yaw ( C.W / C.C.W) 30

53.  The Robot will correct its position if the off set values
are with in the specified limits
 The robot will trigger an Emergency Stop outside of
these tolerances

58. Gamma knife, X-knife are probably as good.
May have an advantage for larger lesions requiring
multiple fractions- meningioma, acoustic
schwanomma etc
More patient friendly(frame)
Continuous image guidance

59. T1&T2 NSCLC – inoperable or medical
contraindication or patient refuses surgery, ideal
lesion <3cm & peripheral location
oligometastasis

65. in a uniform population of medically inoperable
patients with peripherally located early lung cancer,
the RTOG 0236 study dem- onstrated 98% local
control (within the primary tumor) and 87% local-
regional control (within the ipsilateral lobe, hilum,
and mediastinum) at 3 years with an intensive
regimen of 60 Gy in 3 fractions

67. RADIOBIOLOGICAL RATIONALE: LOW
APLHA/BETA RATIO
GOOD RESULTS OBTAINED WITH HDR
brachytherapy
LESS INVASIVE THAN BRACHYTHERAPY

71. Ju AW et al :Radiat oncol jan2013
41 pts intermediate risk
Median fu 21 mo
99% biochemical PFS
No gr3/4 bladder or bowel morbidity
No significant change in sexual QOL

75. BRACHYTHERAPY: 10/10.5 Gy x3 over 24 hours, each
fraction 8 hours apart
BED : 130/142 Gy
SBRT : 7.25 Gy x5 over 5 days
BED: 123 Gy

76. T1 T2 PSA<10 PSA>10 GS<7 GS>7 TOTAL
HDR 30 22 35 17 40 12 52
CK 34 32 40 16 35 31 66
IMRT/I 94 186 94 186 126 154 280
GRT

77. MEDIAN FU 2 YR MEDIAN
BIOCHEMI PSA
CAL NADIR
PFS
HDR 22 MONTHS 94% 0.8
CK 16 MONTHS 96% 1.0
IMRT/IGRT 48 MONTHS 89% 0.9

80. Fiducials placed at surgery
One planning CT with oral and IV contrast
1000cGy to +ve margins 3-4 weeks post OP
5040cGy 5-6 field IMRT6-8 weeks postOP
Concurrent Xeloda
Adjuvant Gemcitabine

88.  Intramedullary spinal cord AVM’s only
 Not amenable to microsurgical excision/embolisatio
 symptomatic

89.  Neurologic examination
 MRI
 Conventional 2D spinal angio

90. Spine tracking
1.25 mm contrast enhanced axial CT
Target volume traced on CT in cojunction with:MRI
2D/3D spinal angio

91.  24 patients
 15 males 9 females
 Time from diagnosis to SRS:7.8 yrs
 Mean age at SRS 34 Yrs
 Presentation :12 hemorrhages
12 had progressive pain or myelopathy
secondary to steal or venous congestion

92.  13 cervical
 8 thoracic
 3 conus medullaris

93.  Target volume :2.8cc(0.26-15 cc)
 Marginal nidus dose :2050cGy(1600-2100)
 Prescription isodose line:79%(68-90%)
 Dmax:2580cGy
 Fractions:1 to 4

94. Angiographic outcome:significant AVM reduction in
all patients >1yr post SRS
6 of 19 patients obliterate
No angio done in 5 patients
Clinical outcome:no further hemorrhages

97. 3 PATIENTS
28 YRS OLD LADY EMBOLISATION DONE TWICE
PRESENTED WITH SEVERE PAIN IN THE
POPLITEAL FOSSA AND CALF REGION
56 YEARS OLD LADY WITH SUDDEN ONSET OF
MYELOPATHY
BOTH THE PATIENTS RESPONDED WELL
25 yr old young man, repeated embolisations
done,had no improvement

100. Current prescription dose to nidus is 2000 cGy
in 2 sessions to larger lesions & 16-18 Gy for
small (<0.7 cc) AVM
radiosurgery is a reasonable option in most
type II spinal cord AVMs

101. Gerszten et al., Radiosurgery for spinal metastases: clinical
experience in 500 cases from a single institution Volume 32,
Number 2, pp 193–199, 2007
 500 cases of spinal metastases treated by CyberKnife ® Radiosurgery at
the University of Pittsburgh
 73 cervical, 212 thoracic, 112 lumbar, and 103 sacral lesions
 Long-term pain improvement occurred in 290 of 336 cases (86%)
 Long-term tumor control in 90% of lesions treated with radiosurgery as a
primary treatment modality
 Long-term tumor control in 88% of lesions that failed other therapies

102. Stereotactic radiosurgery is not a substitute to
surgery but an alternative when indicated
SBRT is becoming a component in the
multidisciplinary treatment of Cancer
In selected cases, SBRT may prove to be a curative
modality of treatment in early cancers