In our experience, intrafraction motion for intracranial targets treated with fiducial free, frameless cranial SRS / SRT on CyberKnife with 6-D skull tracking, is within the acceptable range, and can be reliably detected and corrected. A PTV margin of 1 mm appears adequate to account for most of the intrafraction motion in this situation. However, significant intrafraction motion occurs during treatment delivery when mask based immobilization is used, and hence the same should be accounted for, in situations where intrafraction imaging is not being practiced. Owing to the highest level of precision, excellent automation, ease of treatment planning and delivery and avoidance of anaesthesia, CyberKnife Stereotactic Radiosurgery / Radiotherapy is highly recommended as an alternative to complex cranial neurosurgical procedures.

1. Assessment of Intrafraction Motion during real-time
tracking in the treatment of
Trigeminal Neuralgia using Cyberknife.
Subrata Roy
Senior Radiation Therapist

2. Table of Presentation
Introduction
Classifications of Trigeminal Neuralgia (TGN)
Treatment strategies of TGN
Stereotactic Radiosurgery Overview
Cyberknife Treatment Preparation & Delivery
Efficiency of Cyberknife Treating Small Field Target
Goal of the Study
Materials & Methods of the Study
Results and outcome Analysis
Conclusions

3. Trigeminal neuralgia is a chronic pain condition affecting
the fifth cranial nerve, trigeminal that is primarily
responsible for transmitting sensations from the face to
the brain.
Trigeminal neuralgia or tic douloureux is a neuropathic
disorder of trigeminal nerve that causes episodes of
intense pain in eyes, lips, scalp, forehead and jaws.
It has been labeled as Suicide disease due to
insignificant number of people taking their own life
because they are unable to have their pain controlled by
medication or surgery.

4.  TGN is 5th Cranial Nerve (CNV)
 It is largest of the cranial nerves
 Trigeminal (tri- three , geminus-twinned)
 Responsible for sensation in the face and motor functions.
 The patients typically presents with severe episodic
lancinating, shock like pain sensation in face
 TGN is most chronic pain condition of the trigeminal nerve
 Incidence - 4-5/1 lac population

5. Classification of Trigeminal Neuralgia (TGN)
 Typical idiopathic TN include sudden or sporadic episodes of intense
facial pain .Attacks last from few seconds to few minutes and may occur
in rapid succession with pain free intervals generally.
 Atypical TN – constant pain with stabbing, burning or aching sensations
that are less intense but more widespread.
 Primary TN most cases the pressure is caused by an artery or vein
compressing the trigeminal nerve.
 Secondary TN relies on the demonstration of a major neurologic disease
that causes the neuralgia. A tumor at the cerebellopontine angle or MS
causes TN in 15% of patients
TGN
Typical
Atypical
Primary
Secondary

6. First line treatment option: Medical management (Pharmacotherapy)
Treatment options for medically refractory TGN:
• Surgical: microsurgical vascular decompression (MVD) or ablative procedures like rhizotomy
• Minimal-invasive percutaneous retro gasserian rhizotomies (PRR)
• Nerve block
• Gycerol injection
• Stereotactic Radiosurgery

7. Stereotactic Radiosurgery Overview
High Precision
high degree of reproducible spatial correlation of the target and the radiation source
High Accuracy (<1mm)
delivering the intended dose within 1 mm of the planned position
Rapid fall off of radiation dose at the periphery of the target
Minimizes dose to normal tissues in proximity to the target
High dose conformity
Minimizes dose to normal tissues
Multiple Pencil Beam Intersecting at the Target Point

8. Cyberknife Treatment Preparation & Delivery
Stereotactic Radiosurgery Options

9. Cyberknife Components

10. Synchrony Camera Collimator Exchanger

11. Thanks to modern technology, Now Patients can have some surgeries without being cut open!
There is a Treatment Option that can be done without going under the knife that called Cyberknife

12. Cyber Knife is fully integrated Stereotactic radiosurgery system with real time tracking.
It continually acquires orthogonal kV images during treatment, tracks motion and
automatically adapts treatment delivery to synchronize the treatment beams position with
detected changes in the targets position.
6-axis robotic arm aims each beam of radiation taking into account any translational and
rotational changes.
All measured displacements are automatically corrected, regardless of how small,
maintaining sub-milli meter accuracy, preserving conformal dose distribution, and minimizing
dose to the surrounding critical structures and normal tissues.
SKULLTRACKING, TOTAL SYSTEM ERROR:
 0.95 mm (Accuray Specification)

13.  Cyberknife is a compact linear accelerator mounted with a robotic arm.
 Cyberknife is capable to treat tumors anywhere in the body.
 There is no need for patient to be still or head frames to hold them in place
because the Cyberknife automatically adjusts to the movement of the patient or
tumor.
 The Cyberknife is Pain-free, no anesthesia is required
Treatment Preparation in Cyberknife Usually Completed in Following Steps
 U frame Thermoplastic Mould Preparation
 Acquiring CT Scan with Predefined Standard Cyberknife 6D Skull TGN Protocol
 Obtaining MRI Series
 Treatment Planning Using Cyberknife Treatment Planning System

14. Radiation Therapists Play an immense role In the Treatment Preparation &
Treatment delivery of Trigeminal Neuralgia.
Following Steps to made this Delivery Successfully:-
 U Frame Thermoplastic Mould Preparation (Immobilization Part)
 Acquiring CT Scan with Predefined Standard Cyberknife 6D Skull TGN Protocol.
U Frame Thermoplastic Mould Preparation (Immobilisation Part)
U Frame Thermoplastic Mask is having a thickness of 1.25 mm & giving high quality
rigidness which is very essential while we are delivering high dose of radiation to
the pinpoint Target 0.01 cc
While making the U frame mask needs to be very confirmative on the selection of
proper Head Rest Which will directly reflating on the Patient Comfort and as well as
the reproducibility and minimizing the setup error in sub mm range.

15. Acquiring CT Scan with Predefined Standard Cyberknife 6d Skull TGN Protocol
 All patient immobilization devices that will be used during patient treatment must
be used during CT scanning. Include the CT table top, U Frame Base Plate,
Head Rest, index bar.
 Field of View (FOV): Include the entire circumference of the skull.
 Use the smallest FOV that encompasses the anatomy for the best pixel
resolution.
 Include part of the head rest and extend 1 cm anterior past the tip of the nose &
as much anatomy as possible.
 The CT scan is used to create Digitally Reconstructed Radiographs (DRR)
images. DRR images must have a 1 cm gap anterior and superior to the patient
skull.
 AP and lateral scout images help ensure there are approximately 1 cm gaps
anterior and superior to the skull.

16. • All TGN Patients Head Mask, Proper Nasal Impression Should be given by therapist
which will create impact on the Setup accuracy as per the Standard.
• In Case Of Female Patients Long Hair will always gives a bigger challenge to the
therapists to reproduce the setup .
• Immobilization with Hair Out Or Hair In Should be mentioned on the Patient Setup
Information page and same protocol needs to be fixed on institutional basis to improve the
Bench mark of Good Patient setup

17. Treatment Planning Using Cyberknife Treatment Planning System
• RT planning CT and MRI (T1 ,T2) images fused with
deformable image registration software
• Trigeminal nerve is delineated till it enters in meckel’s cave
• Choice of target – Anterior (Cisternal) OR Posterior (Dosral
root entry zone - REZ) decided depending neurovascular
conflict location
• OARs Contouring - Brainstem, Temporal Lobe, Blood vessel,
Cochlea, VII-VIII nerve complex
Target Delineation Fusion & Contouring

18. Treatment Plan Preparation Dose Volume Histogram

19. TGN Dose Prescription & Treatment Planning
A dose of 80-85Gy max dose prescribed to
the Dorsal root entry zone and 20% IDL
touching the brainstem.
Marginal Dose : 55-60 Gy at 70% ISL
Plan Approval Criteria's:
• Target Coverage
• Sharp Dose Fall Off
• 95%, 50%,30% Dose
• Dose Heterogeneity
• Brain Stem and Other OAR Dose Limits
Sharp fall off of Dose around the small Field Target

20. Dose Distribution & Target Coverage ( CT Plane ) Dose Distribution & Target Coverage on 3D FIESTA seq MRI
Screen Shot Source : Accuray Precision Treatment Planning System

21. The Treatment Delivery Interphase for 6D Skull Tracking mode
Treatment Delivery Console
The treatment delivery computer is the
main computer used for delivering and
monitoring patient treatment. It includes a
flat panel monitor. The monitor, keyboard,
and mouse are located in the Control
Room.
6D Skull Tracking System
The 6D Skull Tracking system
enables tracking of intracranial
targets without the need for
stereotactic frames.
Tracking the target relies on the fixed
relationship between the target
volume and these skeletal features.

22.  6D Skull tracking system used for intra-cranial lesions up to C2,Bony anatomy of the skull is
used as reference for tracking
 This tracking feature allows direct and non-invasive tracking of Intracranial lesions
 Target tracking and motion compensation are accomplished by identifying and tracking rigid Skull
anatomy image intensity and brightness gradients between the DRR and LIVE images
 The naming of this method as 6D because the corrections are made for the 3 translational
motions and 3 rotational motions
 All the Offset Correction values should be Constantly below 0.3mm during the entire course of
Treatment in all direction including the rotational Correction

23. Efficiency of Cyberknife Treating Small Field Target
Image-guided
frameless
robotic system
Sub-mili-
meter
precision
frameless
nature

24. Goal of the Study
Cyberknife Robotic Radiosurgery system is one of the widely used frameless
image-guided radiosurgery system for treating Trigeminal Neuralgia (TGN).
To achieve high accuracy in Frameless Radiosurgery, good immobilization with anatomical
impression is essential.
TGN target is very small (0.01cc) making positional accuracy critically challenging.
In this study we aimed a quantitative assessment of patient intrafraction 6D skull motion
during the treatment with Thermoplastic mask with nasal and eye impression

25. Materials & Methods of the Study
10 patients were included in this study
For all patients, various movements were monitored during the treatment using 6D skull tracking technique.
All six degrees of motion - translational and rotational were assessed using 2D orthogonal X-ray imaging.
Treatment time varied from 30-40 minutes and imaging interval was kept at 15-30
seconds. A total of 1200 images were taken in account in this study.
These offsets were used to calculate intrafraction shifts, and their statistical distribution.

26. The mean intra-fraction translational movements were ± 0.25 mm in antero-
posterior, left-right ± 0.24 mm and ± 0.24 mm in supero-inferior direction, and rotations were
± 0.23 degrees roll, ± 0.23 degrees pitch and ± 0.24 degrees yaw.
Most intrafraction shifts
were ≤ 0.3 mm (Translational) and ≤ 0.3 degree (Rotational)

27. Screen Shots of Treatment Delivery console

28. 10 Patients Characteristics taken for the study
Sl No Age/Sex Diagnosis Radiation dose schedule
1 71/M TGN 85 Gy in 1 Fractions
2 40/F TGN 80 Gy in 1 Fractions
3 55/F TGN 82 Gy in 1 Fractions
4 61/M TGN 80 Gy in 1Fractions
5 76/F TGN 80 Gy in 1 Fraction
6 64/M TGN 80 Gy in 1 Fractions
7 22/M TGN 80 Gy in 1 Fraction
8 71/M TGN 80 Gy in 1 Fractions
9 28/F TGN 80 Gy in 1fractions
10 68/F TGN 80 Gy in 1 fraction

30. Graphical representation of the 6 Degrees of movement during the entire treatment Session
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
A/p shift mm
L/R shift mm
S/I shifts mm
Roll degree
Pitch Degree
Yaw degree

31. Graphical representation of the 6 Degrees of movement during the entire treatment Session
0.22
0.24
0.26
MEAN SHIFT OF 10 PATIENTS
Movement
Time

32. Conclusions
Cyberknife 6D-skull tracking with U-frame thermoplastic mask with nasal & eye
impression compensates for intrafraction motion significantly.
In our experience, 6-D skull tracking with Cyberknife is an effective modality
for highly precise treatment of small targets especially for functional disorders
like trigeminal neuralgia with sub millimetric precision and accuracy.

33. Thank You