Radiotherapy is very much a technology-driven treatment modality in the management of cancer. RT techniques have changed significantly over the past few decades, thanks to improvements in engineering and computing. We aim to highlight the recent developments in radiation oncology, focusing on the technological and biological advances. We will present state-of-the-art treatment techniques, employing photon beams, such as intensity-modulated RT, volumetric-modulated arc therapy, stereotactic body RT and adaptive RT, which make possible a highly tailored dose distribution with maximum normal tissue sparing.

1. Recent Advances in
Radiotherapy Techniques
Subrata Roy
Senior radiation Therapist

2. Flow of Presentation
Overview of Gamma Knife, Construction, Design Working
Principles Clinical Applications
Cyberknife Robotic Radiosurgery System Overview,
Clinical Advantages
X-Knife modification of Linear Accelerator, Energy
Specification
SRS,SRT,SBRT OR SABR,IGRT,IMRT

3. Gamma Knife
• The Gamma-knife delivers radiation
to a target lesion in the brain by
simultaneous irradiation with a large
number of isocentric gamma-ray
beams.
• In the g-knife, a large number of
cobalt-60 sources are housed in a
hemispherical orientation and the
beams are collimated to focus on a
single point.

4. Gamma Knife Unit

5. Continue…..
• In order to maintain permissible exposure levels, the
sources are contained in a very heavy (>20 tons) shielded
central body with a shielded entrance door which is
closed between treatments. A hydraulic system is used to
control the opening and closing of the shielded entrance
door, as well as to position the patient at the focal point of
the unit.
• Gamma-ray beams can be delivered by any number of 192
cobalt-60 sources, housed in a cylindrical configuration
,subdivided into eight movable sectors, each holding 24
sources.

6. Gamma Knife System Components
Radiation unit
Four collimator helmets
Patient treatment table
Hydraulic system
Control panel

7. Gamma Knife Components

9. Gamma Knife Construction
• Introduced by Lerksell in 1960’s
(Lerksell, L. Acta Chir. Scand.
134:585-595 (1968)
• 201 Co-60 sources, each 1 mm
diameter with initial activity of
30 Ci.
• Gold standard for geometric
accuracy, of the order 0.2-0.4
mm (1 mm for linacs)

10. Continue…
• 4 collimator helmets available with diameters of 4, 8, 14, and
18 mm.
• May require many (18 +) shots to cover large targets
• Individual sources may be blocked to prevent beam from
passing through eye or other sensitive structure

11. Continue….
Each beam channel consists of source
/bushing assembly : 65mm thick, 96%
tungsten alloy pre collimator and a 92mm
thick lead collimator .
201 beam channel are focused to a single
point at the center of the unit (focal distance
40.3cm)
Sources lie in an arc +/- 48 deg Central beam
along the long axis of the treatment table .
+/- 80 deg along the transverse axis of the
table.

12. Continue…
No primary radiation beam are directed out of the door .
The central axis of the 201 beam intersect at the focus with
a mechanical precision of +/- 0.3 mm
70° (chin up), 90° (chin horizontal), and 110° (chin down).
patient’s skull and by performing imaging studies, such as CT,
MRI or angiography.
g-knife allows efficient treatment of one or more tumors in
the brain in a single session. It has the potential to treat
lesions in the orbits, para nasal sinuses, and cervical spine.

13. Gamma Knife Frame Fixation Arrangement Beam Shaping Helmet

14. Gamma Knife Radiation Delivery
• Lerksell frame attached such that
target is as close to frame center as
possible
• Frame secured to helmet and
support assembly with target at
isocentre
• doors opened, helmet-patient-
couch advance so helmet docks
with central body
• Irradiation for predetermined time
Beam shaping helmets

15. Basic Comparison b/w Gamma
knife and Cyberknife
• Both Cyber Knife and Gamma Knife are dedicated
stereotactic radiosurgery (SRS) treatment technologies, but
Gamma Knife is limited to only treating cancer above the ear
and in the cervical spine. However, Cyber Knife is the only
dedicated SRS and stereotactic body radiotherapy (SBRT)
system capable of treating cancer throughout the entire
body. Cyber Knife and Gamma Knife are primary treatments
for cancerous and non-cancerous tumors.

16. • They are also effective treatments for vascular lesions and
functional disorders, such as Trigeminal Neuralgia and AVM. The
commonality between the two treatments lies in the fact that
both aim to eliminate tumors and to achieve an outcome similar to
surgery. However, while both are highly targeted therapies, the
principle difference between Gamma Knife and Cyber Knife is that
Gamma Knife requires a large metal frame be mounted onto the
patient’s head with screws before and during treatment. Cyber
Knife is a non-invasive and pain-free treatment that allows
patients to lie comfortably on a treatment couch while the system
moves quickly around them.

17. Prescription IDL of Gamma Knife
• Gamma Knife radiosurgery uses a focused dose of
radiation as an alternative for microvascular
decompression and results in significant pain relief.
• Gamma Knife radiosurgery using a dose range of 70 to 90
Gy to target the trigeminal nerve is a safe and effective
tool for managing trigeminal neuralgia pain in the short
and long term.

18. This work explores how the choice of prescription isodose line (IDL)
affects the dose gradient, target coverage, and treatment time for
Gamma Knife radiosurgery when a smaller shot is encompassed within
a larger shot at the same stereotactic coordinates.
• In terms of absolute dose, the penumbra is also affected by the
choice of prescription IDL where it is advantageous to prescribe to a
line that lies within the dose gradient.
• For GK based delivery, the 50% IDL is by far the most common
selection – largely based on historical precedent and the assumption
that prescribing to the 50% IDL provides the steepest dose fall-off
outside the target.

19. Clinical Applications of Gamma knife
. CRANIAL RADIOSURGERY
• SRS was originally developed for the treatment of benign
lesions of the brain such as arterio- venous malformations
(AVMs), meningioma's, and acoustic neuromas. Its use has
been extended to treat many malignant tumors such as
gliomas and brain metastases. More recently,
• SRS has also been used to treat functional disorders, for
example, trigeminal neuralgia and movement disorders.
Fractional SRT is now commonly being used to treat malignant
brain tumors, especially those in proximity to critical structures
such as brainstem and optic pathways.

20. Brain lesions
–Brain tumors(T≤4cm),Brain metastasis, Benign lesions
,Acoustic neuroma, Av malformations
•Uncontrolled epilepsy

21. • B. EXTRACRANIAL RADIOSURGERY
• SRS has also been applied to treat small localized tumors
outside the cranium. These techniques are frameless (i.e.,
they do not use rigid stereotactic frames to immobilize the
body). Instead, the tumor is localized through image
guidance systems such as Exactrac and Cyberknife.

22. • These systems utilize x-ray imaging of bony anatomy
and implanted fiducial markers to localize the target
and track its motion.
• Extra cranial radiosurgery and stereotactic body
radiation therapy have been applied to the tumors in
the spine, lung, liver, pancreas, kidney, and prostate

23. Gamma Knife Advantages
Bloodless, painless, incision-free stereotactic radiosurgery.
Fast, precise treatment of one or more sites within one
session
Can be used to re-treat areas of the brain in the future
Ideal for hard-to-treat tumors or for patients who cannot
undergo neurosurgery
Does not require anesthesia nor an overnight hospital
stay and a return to normal activities usually within 24
hours
192 beams of highly focused radiation, which converge to
target the tumor and spare healthy, surrounding normal
tissue.

24. X KNIFE (Linac Based Radiosurgery)
• The Linac-based SRS technique
consists of using multiple no coplanar
arcs of circular (or dynam- icily
shaped) beams converging on to the
machine isocentre, which is stereo
tactically placed at the center of
imaged target volume.

25. • A spherical dose distribution obtained in this case can be
shaped to t the lesion more closely by manipulating several
parameters: selectively blocking parts of the circular Field,
shaping the beam’s-eye aperture dynamically with a MLC,
changing arc angles and weights, using more than one
isocentre, and combining stationary beams with 455 arcing
beams. Optimization of some of these parameters is carried
out automatically by the treatment-planning software.

26. History of X-Knife
Early reports of Linac-based radiosurgery with
stereotactic frames in 1980’s
Winston and Lutz published their results from Joint
Center for Radiation Therapy in Boston in 1986
Early Linac treatments required attachment of circular
collimators to standard Linacs
Some relied on inherent precision of the Linac, others
used high precision floor mounts
Radionics, Lei binger and Fischer, Philips, others began
commercial distribution of add-on accessories in
1990s
Stereotactic Cone Assembly
SRS Fix Mask

27. Body Fix SBRT Immobilization
BodyFIX with Diaphragm
Control - By applying pressure
on the abdomen

28. • BodyFIX Diaphragm Control is used to minimize the
movements of targets affected by diaphragm motion
• BodyFIX Stereotactic System with Localizer - The stereotactic
localizer is used as a coordinate system for frame-based
localization during imaging.

29. Cyberknife Robotic System Overview
• The Accuray Cyberknife Robotic Radiosurgery System
consists of the following major functional sub-systems:
Treatment Delivery
 Imaging
 Target Tracking
 Data Management
 Treatment Planning
 Patient Support

30. Cyberknife System

31. Cyberknife System Specifications
Cyberknife Components
Manipulator
 KUKA robot with 6 axes of
rotation
 < 0.2 mm Mechanical precision
 Manual control with “Teach
pendant”
 Programmable robot positions
Linac
 6 MV
 No flattening filter
 Dose Rate = 1000 cGy/Min
 Sealed ion chambers (since 2010)
Collimation system
 12 Fixed cones or IRIS variable
collimator
 Collimator exchange table

32. • Robo couch
• 6 degrees of motion
• kV X-ray Target Location System
• Floor mounted flat panel imagers
• Perkin Elmer A Si panels
• 1024 x 1024 pixels
• 41 x 41 cm physical dimensions
•
Ceiling mounted X-ray tubes
Oil cooled
2.5 mm Al filtration
up to 125 kV, 320 mA, 500 ms
Synchrony Respiratory Tracking
System
Ceiling mounted LED camera array
Treatment Planning System
Multi-Plan V3.5

33. Stereotactic Radiosurgery
• Stereotactic radiosurgery is a nonsurgical form
of radiation therapy we use to treat cancers of
the brain, lung, as well as other types of cancer
that require a high degree of precision.
With regular radiation therapy treatment,
healthy tissue also receives radiation. With
stereotactic radiosurgery, doctors may better
focus the radiation on a tumor, so nearby healthy
tissue is protected. This is especially important
for areas like the lungs and brain.
•

34. • Using this technology, doctors may be
able to reach tumors deep inside the
body without the risks of surgery.
There is no incision, minimal
discomfort, and few of the risks
typically associated with surgery, such
as infection.
•

35. Stereotactic Radiosurgery
• Radiosurgery" refers to delivery of high dose of radiation in a
single fraction with an aim to eliminate lesion than treat.
• Present Methods of SRS
Gamma Knife
Proton beam or Bragg peak Radiosurgery
Cyberknife Radiosurgery

36. Gamma Knife Unit
Proton Therapy
Cyberknife VSI System

37. Stereotactic Radiotherapy
• Stereotactic radiotherapy (SRT) gives radiotherapy from many different angles
around the body. The beams meet at the tumor. This means the tumor receives a
high dose of radiation and the tissues around it receive a much lower dose. This
lowers the risk of side effects. Usually you have between 1 and 8 treatments.
• Stereotactic radiotherapy is frequently given in a single dose (sometimes called
radiosurgery) although certain situations may require more than one dose. In
addition to treating some cancers, radiosurgery can also be used to treat
malformations in the brain's blood vessels and certain noncancerous (benign)
neurologic conditions.

38. Stereotactic body Radiation Therapy
• Stereotactic body radiation therapy (SBRT) uses imaging techniques to
deliver a targeted radiation dose to a tumor. The radiation is focused on
the tumor with millimeter precision. The result may be that less healthy
tissue gets damaged by radiation. Preserving healthy tissue is important
for cancer patients whose tumors are near or in essential organs. Before
treatment, markers are placed around the tumor. SBRT uses a
coordinate system to precisely locate the tumor to ensure proper
placement of the tracking devices. During treatment, we deliver
concentrated, highly focused radiation. The custom mapping provided
by the coordinate system plans the radiation to account for a patient's
anatomy, breathing and organ motion.
•

39. • Throughout the treatment, the intensity and direction of the
beams are constantly modulated to target the tumor and
spare healthy tissue. The beams are also adjusted for any
movement from breathing or digestion.
•
• SBRT may be used to deliver a single high dose of radiation,
or several fractionated radiation doses (usually up to five
treatments over a period of days).

40. Image Guided Radiation Therapy
• Tumors can shift inside the body,
because of breathing and other
movement. Image guided
radiation therapy (IGRT) may
allow doctors to locate and track
tumors at the time of treatment
and deliver more precise
radiation treatment.
Linac Based IGRT

41. • This technology also allows our radiation oncologists to make
technical adjustments when a tumor moves outside of the
planned treatment range. As a result, the radiation
treatment is targeted to the tumor as much as possible,
helping to limit radiation exposure to healthy tissue and
reduce common radiation side effects.

42. Intensity Modulated Radiation Therapy
Intensity modulated radiation therapy (IMRT) uses advanced
software to plan a precise dose of radiation, based on tumor
size, shape and location. A computer- controlled device called
a linear accelerator delivers radiation in sculpted doses that
match the 3D geometrical shape of the tumor, including
concave and complex shapes. With IMRT, our radiation
oncologist can adjust the intensity of radiation beams across
the treatment area as needed with precision accuracy.

43. This means we can deliver higher radiation
doses than traditional radiation therapy
methods, while reducing exposure to healthy
tissues.
Because of its greater degree of accuracy, IMRT
may be a treatment option for patients who
have reached the maximum allowable dose of
conventional radiation therapy and have a
recurrent tumor in the treated area.

44. Key Points :::::
Intracranial SRS or SRT techniques involve a stereotactic
apparatus to immobilize the head and the delivery of
radiation through multiple no coplanar beams or arcs.
 An overall accuracy of ±1 mm in the coverage of the
intended target volume is a commonly accepted standard for
the SRS and SRT procedures.


45. Key Points :::::
SRS requires careful commissioning and rigorous QA
procedures.
 Extra cranial SRS or stereotactic body radiation therapy
procedures are frameless and rely on robotic image-guided
radiation therapy techniques such as Exactrac and
Cyberknife.

46. Key Points :::::
Stereotactic body radiation therapy (SBRT) is an external
beam radiation therapy method used to deliver an ultrahigh
dose of radiation to an extra cranial target.
 Early SBRT treatment deliveries used body frames with
independent stereotactic coordinate systems to immobilize
patients. These have largely been replaced with more
conventional immobilization combined with pretreatment
IGRT position verification.

47. Key Points ::::::
 Dose calculations for SBRT in the lung should be made on
treatment planning systems capable of determining doses
near the lung–tissue interface. Three-dimensional algorithms
such as convolution-superposition and Monte Carlo are
recommended.
 The biologic effects of SBRT doses fractionations are very
high—ranging to over twice that of conventional
fractionation schemes.
.

48. Key Points ::::::
Target motion may be physically reduced with abdominal
compression devices or breath-hold techniques.
Dosimetry of small Fields as used in SRS or SRT is complex
because of a possible lack of charged particle equilibrium.
The detector must be of a sufficiently small size so as not to
perturb the electron Fluence. Any energy dependence must
also be accounted for.


49. • Conclution