الفهرس 
TitleOnly 14 pages are availabe for public view
 |  | from | 115 |  |  |
| | | from | 115 | | |
Abstract
There are more than 200 types of human cancer, each with different
causes, symptoms and treatments. In general, cancer is predominantly an
environmental disease with 90-95% of cases being attributed to lifestyle
factors, and 5-10% due to genetics.
While cancer can affect people of all ages the overall risk of developing
cancer generally increases with age, at least up to age 80-85 yrs. Cancer is the
major cause of leading deaths in the 21st century in world with 14.1 million
cases and 8.2 million deaths occurred in 2012. These rates are rising as more
people live to an old age and as lifestyle changes occur in the developing
world.
Prostate cancer is the second most common form of cancer and the fifth
leading cause of cancer death among males. The prostate cancer causes death
for men over fifty years of age. Most of the deaths from prostate cancer are
related to advanced disease that can be prevented with better screening
practices. Among the different technologies adopted to cure the prostate
cancer; external radiotherapy is recognized as one of the important treatment
option.
The greatest challenge for radiation therapy or any cancer therapy is to
attain the highest probability of cure with the least morbidity. The simplest
way in theory to increase this therapeutic ratio with radiation is to encompass
all cancer cells with sufficient doses of radiation during each fraction, while
simultaneously sparing surrounding normal tissues. The ongoing pursuit to
achieve an optimal dose distribution has prompted the radiation therapy
profession to develop new techniques that incorporate advances in
technology. In radiation therapy today, modern techniques that include threedimensional
conformal radiation therapy (3D-CRT), intensity modulated
radiation therapy (IMRT), and arc radiation therapy (ART) are routinely used
in the treatment of cancers.
Accordingly, the current study was conducted aiming to compare
between different radiotherapy techniques: three-dimensional conformal
radiation therapy (3D-CRT), intensity modulated radiotherapy (IMRT) and
arc radiation therapy (ART) in achieving homogenous radiation dose
distribution to the tumor while maintaining lower doses to organs at risk in
patients with prostate cancer.
Summary
71
For this purpose, this study included fifteen prostate cancer patients.
Three treatment planning were performed to compare between using 3DCRT,
IMRT and ART used for radiotherapy treatment of the patients. The
planning target volume (PTV) and the volumes of the organs at risk were
delineated using CT scan (Siemens SOMATOM CT Scanner) for each
patient. The CT data is imported to the contouring workstation via local area
network system. A software application medical system (CMS XiO Radiation
Therapy Planning) was used for the treatment planning procedures. Bearing in
mind, for comparison, the estimation of some parameters, namely; the D2
(Dose delivered to 2% of the PTV), D5 (Dose delivered to 5% of the PTV),
D50 (Dose delivered to 50% of the PTV), D95 (Dose delivered to 95% of the
PTV), and D98 (Dose delivered to 98% of the PTV), the maximum, the
minimum, and the mean doses received by the PTV, V95(Volume covered by
95% of the prescribed dose), V105 (Volume covered by 105% of the
prescribed dose), in addition to the Homogeneity Index (HI), the Uniformity
Index (UI), the Conformity Index (CI), the Over Dose Indexes (ODI), and the
Global Max (GM) of the PTV. The organs at risk considered in this work
were: rectum, bladder, right head of femur and left head of femur. For
comparison of dose received by OARs, the estimation of some parameters,
namely V15Gy, V35Gy, V50Gy, V60Gy, V65Gy, V70Gy, D30%, the mean
dose and integral dose.
The results of the current study showed that, for the planning target
volume (PTV), the median doses received by PTV D2%, D5%, and D50%
were significantly higher in ART technique than in 3D-CRT and IMRT
techniques but, the median doses received by PTV D95% and D98% were
significantly higher in IMRT technique than in 3D-CRT and ART techniques.
In the present study, the volume % of PTV covered with 95% (V95%)
of the total prescribed dose in IMRT technique was nearest to the acceptable
ranges of V95% than in 3D-CRT and ART techniques. But in V100%, ARC
technique was nearest to the acceptable ranges of V100% than in 3D-CRT
and IMRT techniques. The Volume % of PTV covered with 105% (V105%)
was greater in ARC technique than 3D-CRT and IMRT techniques.
The better technique should achieve better and homogeneous dose
distribution to the PTV. The minimum and maximum acceptable radiation
doses to the PTV should be (95%-107%) which was achieved by three
treatment techniques. However, the inter comparison between the three
planning techniques for (HI, UI, CI, and ODI) proved that the radiation doses
received in IMRT is the best. However, the inter comparison between the
Summary
72
three planning techniques for MUs proved that 3D-CRT and ART have
smaller number of MUs than IMRT.
Regarding dosimetric parameters for organs at risk, the comparison of
3D-CRT techniques versus IMRT technique versus ART technique showed
that, the median doses delivered to rectum, bladder, right head of femur, and
left head of femur irradiated with IMRT technique were lower than that for
3D-CRT and ART techniques, but those doses were still within the dose
tolerance of the prostate cancer organs at risk.
With respect to dosimetric parameters for healthy tissue, the
comparison of 3D-CRT technique versus IMRT technique versus ART
technique showed that, 3D-CRT and ART techniques irradiated smaller
volume of normal healthy tissue in the low to medium dose region and
delivered lower integral doses than IMRT technique. However, IMRT plan
irradiated smaller volume of normal healthy tissue in the high dose region and
delivered lower integral doses than 3D-CRT and ART techniques.