الفهرس 
TitleOnly 14 pages are availabe for public view
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Abstract
Cancer in prostate is a widespread malignant disease. Recently, external beam radiotherapy has
been used extensively for treating a large number of prostate cancer patient. Radiotherapy must
be accurate by delivering the maximum target dose while sparing the surrounding normal tissue.
There are many radiotherapy techniques used. One of these important techniques is Intensity
Modulated Radiotherapy (IMRT). Intensity Modulation Radiotherapy (IMRT) is a more
advanced technique of Three-Dimensional Conformal Radiotherapy (3D-CRT). IMRT applied
by using gantry machine that moves remotely around the patient from all direction 360 degrees
as it delivers radiation dose. Additionally can shaping the fields and directing the radiating field
at the prostate from different angles, the fields intensity can be modified to control the doses of
radiation sparing from surrounding critical organs. This also allows oncologist to give the tumor
the highest radiation dose while sparing organs at risk. Since the introduction of IMRT, this
technique has been widely used for prostate cancer treatment. IMRT can be used for delivering
conformal dose distributions by the selection of an appropriate energy and MLC for performing a
proper therapeutic plan and for delivering high-quality treatment through a treatment planning
system (TPS).
The Purpose of this Study
The study’s objective was to compare between 6MV and 10MV energies and assess the impact of
160 MLC versus 58 MLC on prostate cancer treatment and sparing critical organs (OARs) such
as; rectum, urine bladder, penile bulb, head of left femur and head of right femur by using
Intensity Modulated Radiotherapy (IMRT).
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Study Preparation and Description
The present study included fifteen cases confirmed prostate cancer and prescribed for RT
treatment. Xio Treatment Planning System (TPS) with software version 4.64.02 was used to
design the plans for each case. Three different intensity modulated radiotherapy plans with the
same parameters dose 72Gy, 7 fields, and same dose constrains were designed as follow: plan1:
6MV, 58 MLC with 1cm width, Plan 2: 6MV, 160 MLC with 0.5 cm width and plan3: 10 MV,
160MLC with 0.5cm width to evaluate the dose distributions relating to PTV coverage,
Homogeneity and Uniformity Indexes, and organs at risk doses. The three different IMRT plans
were evaluated to detect the most suitable plan to be used later for the treatment of prostate
patients according to achieving more homogeneous doses to the tumor volume and more sparing
to the critical organs surrounding.
The Results of this Study Showed the Following:
The results of this study showed that, variations in dosimetry founded by the intensity modulated
radiotherapy plans using 6MVenergy, the PTV dose percentage differences for D2%, D 5% and
D 50% were the same tumor coverage without any significant differences between 1cm vs. 0.5
cm MLC leaves. Dose percentage of D95% and D98% indicated that 160 MLC, 0.5cm width
leads to a better PTV coverage than 58 MLC, 1cm width with significant differences (p =
0.001), regardless of the energy used. No distinctive differences between Uniformity Index for
both leaves width were reported while, Homogeneity Index of the target showed that, 160 MLC,
with 0.5 widths enhanced homogeneity index than in IMRT plans using 58 MLC, with 1cm
width. With regard to OAR, 6 MV,160 MLC with 0.5cm spared rectum, bladder and penile bulb
in high-dose regions V60Gy V65Gy and V70Gy more than 6 MV,58MLC with 1cm, although without
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59
any significant differences. Also, the present work investigated the outcome of 6Megavolt and
10 Megavolt energies on the quality of IMRT plans for patients with prostate cancer. Results
showed that, There were only minor distinctions in (D95%) of planning target volume,
homogeneity and Uniformity index and organs at risk between 6Megavolt and 10Megavolt
energies and there were insignificant variation between them.
Conclusions
The 6 MV energy dose distributions with 160MLC leaf with 0.5cm width for the PTV
coverage and homogeneity generated by using treatment planning calculations were more
better than, those generated by using the 6 MV energy beams with 58MLC leaf with 1
cm.
The 6 MV energy dose with 160MLC leaf with 0.5cm width spared critical organs, such
as the rectal wall, the urinary bladder, the femoral head and penile bulb more accurately
than, those generated by using the 6 MV energy beams with 58MLC leaf with 1 cm.
No relevant advantage on PTV coverage, homogeneity and Uniformity index or dose
reduction at OAR was noticed between 6-MV and 10-MV.