GRID THERAPY.Best paper award ARTICON-2011

1. SHIJO VARGHESE
RADIOTHERAPY TECHNOLOGIST
ACRO
Dr.BALABHAI NANAVATI HOSPITAL
MUMBAI.

2.  With the advent of megavoltage radiation, the concept
of spatially fractionated radiation(SFR) has been
abandoned for the last several decades; yet,
historically, it has been proven to be safe and effective
in delivering large cumulative doses of radiation in the
treatment of cancer.SFR has been adapted to
megavoltage beams using a specially constructed grid
 This treatment modality is used for the palliative
treatment of large deeply seated tumors

3.  Kohler (1909)- described radiation through a
“perforated screen" creating an effect similar to
treatment with multiple small pencil beams.
 Liberson (1933)- used this technique for the
successful treatment of deep seated cancers.

4.  Deliveryof high dose of radiation in clusters of small
areas without producing prohibitive normal tissue
damage to the skin and subcutaneous tissue.
 Small volume of skin could safely tolerate high doses
of radiation.
 Radio biologically several logs of tumor are likely to
be killed thereby allowing for re-oxygenation.
 Production of cytokines could lead to Bystander
effect.

5.  GRID :50/50(open to closed
areas)
 Maximum field size :20 x 20 cm
 Energy : 6- 20 MV
 SSD :100 cm
 Dose :12-20 Gy (median 15 Gy)
 Field placement :single unopposed field
 Dose prescription :D max in the open area of
the Grid.

6.  MLC can provide the spatial fractionation for
grid therapy.It has many advantages in
comparison with cerrobend grid collimators
notably the ease of creating a grid of any
opening size and pattern by simply
programming the leaf positions(limited only by
the positional precision of the MLC leaves).
 Though the longer delivery time is a
disadvantage.

7. Grid is an 8 cm thick lead block
containing cylindrical holes
The central axis of each hole
was drilled to match the diver-
gence of the radiation from
its central axis
Holes were arranged in a hexago-
nal array. At the isocentre, they pro-
jected 1.3 cm diameter Circles
separated by 1.8 cm

8. Targeted Effects
direct indirect
Non Targeted Effects
Induced genomic Bystander Effects
instability

9. INDUCED GENOMIC
BYSTANDER EFFECT
INSTABILITY
 Effects observed in cells
 observed in the progeny that were not irradiated
of an irradiated cell that but were “bystanders” at
may / may not have been the time of irradiation.
subject to energy  Killing or damage of un
deposition events. irradiated cells due to
irradiation of adjacent
cells.

10.  Bystander effect refers to a theory that,
many of the types of radiation induced
damage seen in irradiated cells can
also be seen in adjacent non irradiated
cells.
 Such damages include DNA
damage,DNA mutations, chromosomal
imbalance and genomic
instability,apoptosis,micronuclei
formation,oncogenic transformation.
 The untargeted cells show responses
which are characteristics of irradiated
cells.

12.  Cytokines are signalling molecules or protein
molecules which are secreated by glial cells of
nervous system.
 A variety of cytokines especially TNF –alpha
and TGF –beta are known to be released in
response to high dose radiation.
 Cytokines can be tumoricidal,tumoristatic or
promote neoplastic transformation and growth.

13. Presence of TNF alpha in serum. Presence of TGF beta in serum.

15. Neck nodes from primary squamouscell cancer of
oropharynx after 1500 cGy SFR

16.  The grid therapy was found to be
advantageous for treating the acutely
responding tumors, but not for late responding
tumors.
 Mobile tumors such as those in the thorax and
abdomen respond worse to grid treatments
than stationary such as those in head and
neck.
 Not advicable to treat critical organs such as
eye lens, spinal cord etc.

17.  Large and bulky sarcomas have an
unfavourable prognosis and are difficult to treat
with conventional radiation alone
 However with SFR high dose radiation can
be used in conjunction with conventional RT to
provide rapid relief of pain and other symptoms
as well as providing select patients an
opportunity for surgical resection of disease.

18. THANK
YOU
shijortt@gmail.com