[Telah dilakukan penelitian dalam mengevaluasi pengaruh material homogen dan inhomogen pada teknik IMRT (Intensity Modulated Radiotherapy) menggunakan modalitas Fan Beam CT (FBCT) dan Cone Beam CT (CBCT) terhadap Gamma Index (GI). Perencanaan ulang dilakukan untuk 5 pasien kanker paru kanan pada modalitas FBCT dan CBCT menggunakan TPS Phillips Pinnacle energi foton 6 MV. Menggunakan Teknik IMRT 30 segmen, 50 segmen, dan 70 segmen untuk perencanan terapi. Calculation Grid Resolution (CGR) 0.2 cm dan 0.4 cm digunakan sebagai resolusi dalam perhitungan dosis. Serta kalibrasi bilangan CT (KBC) FBCT, CBCT, dan linear dipergunakan sebagai koreksi CT density number. Pengukuran plannar dose untuk evaluasi Gamma Index (DD 2% / DTA 2 mm, passing rate 90%) dilakukan pada SAD 100 cm dengan material homogen dan inhomogen pada kedalaman 1.5 cm, 5 cm, dan 10 cm. Didapatkan deviasi nilai rata-­‐rata GI antara CGR 0.2 cm dengan 0.4 cm material homogen modalitas FBCT dan CBCT berturut-­‐tutut ≤1.46% dan ≤ 1.13%. Serta deviasi pada material inhomogen sebesar ≤ 2.54% (FBCT) dan ≤ 1.74% (CBCT). Deviasi Nilai rata-­rata GI antara FBCT dengan CBCT dengan CGR 0.2 cm berturut-­turut ≤ 1.95% (homogen) dan ≤ 2.36% (inhomogen). Dan deviasi Nilai rata-­‐rata GI antara material homogen dan material ekuivalen homogen sebesar ≤ 0.80%. Dari hasil penelitian yang didapat, bahwa evaluasi Gamma Index dapat dipengaruhi oleh jumlah segmen, modalitas CT, kalibrasi bilangan CT, Calculation Grid Resolution, dan kedalaman material.

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These Studies have been carried out to evaluate the effect of a homogeneous and inhomogeneous material on IMRT Technique (Intensity Modulated Radiotherapy) using Fan Beam CT (FBCT) and Cone Beam CT (CBCT) for the Gamma Index (GI). The Phillips Pinnacle treatment plan was used to replan 5 patients on right side of lung cancer. Photon 6 MV was applied to this technique with 30 segments, 50 segments, and 70 segments, repectively. Using Calculation Grid Resolution (CGR) 0.2 cm and 0.4 cm for resolution in the calculation of the dose. As well as the calibration of CT numbers (CCN) FBCT, CBCT, and the linear density are used as a correction CT number. The planar measurement for the evaluation of Gamma Index (DD 2% / DTA 2 mm, the passing rate of 90%) carried out at 100 cm SAD with the homogeneous and inhomogeneous material at a depth of 1.5 cm, 5 cm, and 10 cm, respectively. We obtained deviation average value of GI between CGR 0.2 cm and 0.4 cm using the homogeneous material on FBCT and CBCT modality ≤1.46% and ≤ 1:13%, respectively. As well as the material inhomogeneous deviation of ≤ 2.54% (FBCT) and ≤ 1.74% (CBCT). The deviation of the average GI value between FBCT with CBCT with CGR 0.2 cm respectively ≤ 1.95% (homogeneous) and ≤ 2.36% (inhomogeneous). Finally, the deviation of the average GI value between homogeneous and equivalent of homogeneous material is ≤ 0.80%. From the results obtained, that the Gamma Index can be influenced by the number of segments, modalities of CT, calibration of CT numbers, calculation grid resolution and depth of material.

, These

Studies

have

been

carried

out

to

evaluate

the

effect

of

a

homogeneous

and

inhomogeneous

material

on

IMRT

Technique

(Intensity

Modulated

Radiotherapy)

using

Fan

Beam

CT

(FBCT)

and

Cone

Beam

CT

(CBCT)

for

the

Gamma

Index

(GI).

The

Phillips

Pinnacle

treatment

plan

was

used

to

replan

5

patients

on

right

side

of

lung

cancer.

Photon

6

MV

was

applied

to

this

technique

with

30

segments,

50

segments,

and

70

segments,

repectively.

Using

Calculation

Grid

Resolution

(CGR)

0.2

cm

and

0.4

cm

for

resolution

in

the

calculation

of

the

dose.

As

well

as

the

calibration

of

CT

numbers

(CCN)

FBCT,

CBCT,

and

the

linear

density

are

used

as

a

correction

CT

number.

The

planar

measurement

for

the

evaluation

of

Gamma

Index

(DD

2%

/

DTA

2

mm,

the

passing

rate

of

90%)

carried

out

at

100

cm

SAD

with

the

homogeneous

and

inhomogeneous

material

at

a

depth

of

1.5

cm,

5

cm,

and

10

cm,

respectively.

We

obtained

deviation

average

value

of

GI

between

CGR

0.2

cm

and

0.4

cm

using

the

homogeneous

material

on

FBCT

and

CBCT

modality

≤1.46%

and

≤

1:13%,

respectively.

As

well

as

the

material

inhomogeneous

deviation

of

≤

2.54%

(FBCT)

and

≤

1.74%

(CBCT).

The

deviation

of

the

average

GI

value

between

FBCT

with

CBCT

with

CGR

0.2

cm

respectively

≤

1.95%

(homogeneous)

and

≤

2.36%

(inhomogeneous).

Finally,

the

deviation

of

the

average

GI

value

between

homogeneous

and

equivalent

of

homogeneous

material

is

≤

0.80%.

From

the

results

obtained,

that

the

Gamma

Index

can

be

influenced

by

the

number

of

segments,

modalities

of

CT,

calibration

of

CT

numbers,

calculation

grid

resolution

and

depth

of

material.

Key

words

:

Calculation

Grid

Resolution,

Calibration

of

CT

Numbers,

Cone]