the dosimetry of radiation therapy wang pengcheng 2007 [email protected]
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The Dosimetry of The Dosimetry of Radiation TherapyRadiation Therapy
Wang Pengcheng 2007
Radiation Therapy : the Myths
For many lay-people, the word radiation conjures a host of myths and misconceptions.
Radiation Therapy : Myths The therapy is believed to burn
recipients. The therapy is believed to make them
radioactive (only true with temporary internal implants).
Often viewed as painful. Often viewed as a last resort. Nursing needs to teach patients and
their family members about radiation therapy before it begins to relieve their fears and ensure their compliance.
What is true of Radiation Therapy The use of ionizing radiation is to interrupt
cellular growth. Is frequently done as an outpatient
procedure so we must stress self-care. This treatment modality may be chosen
when the treatment goal is curative, such as in Hodgkin’s disease, testicular seminomas, localized cancer of the head and neck, and cancers of the uterine cervix.
Radiation Therapy Is used to control malignant disease.
when a tumor cannot be removed surgically.
local nodal metastasis is present. prophylactically to prevent leukemic
infiltration to the brain or spinal cord. Palliative irradiation is frequently used
to relieve symptoms of metastatic disease, especially when it has spread to brain, bone, or soft tissue.
一、 Definition of Radiation Therapy
Definition : 利用射线对肿瘤及其侵犯底组织进行一
定剂量底局部照射,以控制肿瘤细胞生长底物理治疗技术。
Beam available all beam: xγπβαp…
Radiation Therapy
Is a cancer treatment modality used to cure, control, or
palliate malignant disease. Both internal and external
means of radiation therapy are available for local delivery.
More than 70% of all people with cancer will receive
radiation therapy. either as a primary, adjunctive, or
palliative intervention
Radiation can be used as a treatment for solid tumors or
combined with other treatment modalities ( chemotherapy
or surgery).
Goals of Radiation Therapy Cure
To eradicate the disease Control
Control the growth and the spread of the cancer
Prophylaxis (预防) To control microscopic disease
Palliation To reduce complications or symptoms of the
cancer. May be used to control pain.
二、 Development of Radiation Therapy
1.development of radiation
and equipments in RT
In 1895 x-ray was discovered.
In 1896, Henri Becquerel
discovered that uranium salts
emitted rays similar to x-rays
in their penetrating power.
安东尼 ·亨利 ·贝克勒尔( Antoine Henri
Becquerel , 1852—1908 年),法国物理学家。 1896 年 3 月,贝克勒尔发现,与双氧铀硫酸钾盐放在一起但包在黑纸中的感光底板被感光了。他推测这可能是因为铀盐发出了某种未知的辐射。从
而确认了天然放射性的发现。
二、 Development of Radiation Therapy
后来,居里夫妇将其称为“放射性”。现在,我们称其为天然放射
性。尽管贝克勒尔当时错误地认为它是某种特殊形式的荧光,但天然放
射性的发现仍不愧是划时代的事件,它打开了微观世界的大门,为原子
核物理学和粒子物理学的诞生和发展奠定了实验基础。
This phenomenon was studied by Pierre and Marie Curie and was later named radioactivity by them.
In 1903, the Curies shared with Henri Becquerel the Nobel prize in physics for their investigation of uranium and radioactive material.
Development of Radiation Therapy
In 1911, Marie curie was awarded the Nobel prize for her discovery of the elements radium.
Marie Curie died in 1934 of pernicious anemia caused by her long exposure to radium.
Development of Radiation Therapy
1902 , the treatment of skin cancer using radiation was reported
1920, orthovoltage therapy machine invented. The first Cobalt 60 machine was produced in
Canada. 1958, the first electron accelerator was built in
Britain 1968, the modern linear accelerator was built in
USA by Varian brothers 1990’s, modern time, 3D RT due to the computer
technique.
Development of Radiation Therapy
2. development of radiobiology The primary understand of radiobiology
were from the injure and the diseases like leukaemia.
1950, cell technique developed. Cell cycle revealed.
1960, radiobiology in molecular level: target thesis.
Development of Radiation Therapy
Radiation Cellular Effects
Approximately 20% is a direct effect.
Ionizing radiation causes breakage among the strands of
the DNA helix, causing cell lysis, which leads to cell death.
Works on the DNA of cancer & normal cells.
Approximately 80% is an indirect effect.
Ionizing can also ionize body fluids, especially water in the
cell, leading to the formation of free radicals, which cause
irreversible damage to the DNA by breaking the strands.
This causes cell lysis and cell death.
Radiation cellular Effects
Cellular death may occur immediately if DNA
repair does not occur, or at the time of cellular
division when the damaged cell attempts
mitosis (有丝分裂) and dies.
Finally, a tumor cell may become sterile by the
effects of radiation and die a natural death
without the ability to produce progeny
(offspring).
Cellular Factors Influencing Response to Radiation
Cell Cycle
Cells are most vulnerable to the disruptive effects of radiation during DNA synthesis and mitosis (early S, G2, and M phases of the cell cycle).
Oxygenation
Tumors that are well oxygenated are more sensitive to radiation. Radiation therapy might be enhanced if oxygen concentrations, hyperoxygenation, to tumors could be increased.
Cellular Factors Influencing Response to Radiation
Therefore the most sensitive cells to radiation are rapidly dividing, well oxygenated, more vascular cells.
Radiosensitivity
A radiosensitive tumor is one that can be destroyed by a dose of radiation that still allows for normal cell regeneration in the normal tissue.
Those tissues that are slower growing or at rest are relatively radioresistant.
Radiosensitivity
HighSensitivity
ModerateSensitivity
LowSensitivity
Radio-resistant
BoneMarrow
Skin Liver Muscles
LymphTissue
Lung Kidneys ConnectiveTissue
GI Tract SalivaryGlands
Thyroid Cartilage
MucousMembrane
PeripheralNerves
Gonads Heart
3. RT development in China 97-98,450 hospitals have RT, about 10000,
radiation oncologists , technician, physicists 1998, about 500 units accelerators and 500
cobalt 60 and 400 afterload system served in hospitals.
1999,about 30 r knifes and 60 x-knife Now: we can’t imagine how many RT
equipments served in different clinic unit.
Development of Radiation Therapy
三、三、 The methology and The methology and equipments for Radiation Therapyequipments for Radiation Therapy
1.external radiation therapy1.external radiation therapy
If the external radiation therapy is used, one of several methods of delivery may be chosen, depending on the depth of the tumor to be radiated.
The higher the energy the deeper the penetrating into the body.
Machines Used:
Kilovoltage Therapy Devices (Superficial radiation and Orthovoltage) deliver the maximum radiation dose to superficial lesions such as lesions of the skin and breast.
Gamma ray sources (Cobalt -60 units) deliver the radiation dose to deeper body structures and spare the skin from possible adverse effects.
三、三、 The methology and The methology and equipments for Radiation Therapyequipments for Radiation Therapy
Megavoltage Therapy (Linear accelerators and Betatron Machines) deliver their dosage to deeper structures without harming the skin and also create less scattering of radiation within the body tissues. This is high energy x-rays.
Particle beam therapy (Cyclotrons) This is used for treating hypoxic, radioresistant tumors with neutron beam therapy.
三、三、 The methology and The methology and equipments for Radiation Therapyequipments for Radiation Therapy
2.Brackytherapy Continuous low dose radiation from
implants. The benefits of local irradiation are:
A high dose can be given in a relatively few number of days.
Allows a high dose to be given in the tumor tissue while staying within normal tissue tolerance for the rest of the body.
三、三、 The methology and The methology and equipments for Radiation Therapyequipments for Radiation Therapy
三、三、 The methology and The methology and equipments for Radiation Therapyequipments for Radiation Therapy
3.Stereotactic radiotherapy What is Stereotactic Radiosurgery?
Stereotactic Localization Radiosurgery Applications
Different technologies Gamma Knife LINAC-based systems CyberKnife
三、三、 The methology and The methology and equipments for Radiation Therapyequipments for Radiation Therapy
What is Stereotactic Radiosurgery?
Method to non-invasively & specifically treat benign/malignant tumors and tissue abnormalities Uses methods of stereotactic 3-D
localization of surgical site Uses radiosurgical techniques to
perform the “surgery”
3-D Stereotactic Localization Goal: To target the tissue of interest with as much
accuracy as possible
Use imaging and 3-D mapping techniques to target tissue of interest
4 general medical imaging modalities used: X-Ray PET MRI Digital Subtracted Angiography
Use the patient as a reference for the localization 2 general methods:
Frame stereotactic localization (old school) Frameless stereotactic localization (new school)
The Imaging Modalities Tomographic Techniques:
PET (CT) and MRI Good for tumor pathologies Use multiple layers to get 3-D image
X-ray-based Techniques: X-ray and Digital Subtracted Angiography Good for vascular imaging (for treatment of
vascular malformations) Use pins and depth perception methods to
get 3-D localization
Types of Radiation Differs with different machines:
High-energy X-ray From linear accelerator systems
Gamma radation From Cobalt-60 source
Proton From particle beam or cyclotron Limited use in the US Uses Bragg Peak principle:
As proton slows down, it gives off disproportionately more energy
Right before it stops, it gives off most of its energy, resulting in a peak at that depth of tissue
Different Machines in Use Gamma Knife
Gamma radiation from Cobalt-60 Source Use multiple beams to treat tissue volume
LINAC-based systems (X-Knife) High-energy X-ray from Linear Accelerator device Use fractionation
CyberKnife Also a LINAC system, but LINAC is on a robotic arm Use fractionation Can be used for parts of body other than the head
Gamma Knife
-Over 30 years of clinical use and a great deal of publications
-Targeting Precision of within 2mm
-Multiple targets can be easily treated in one session
http://www.elekta.com/ContentUS.nsf
LINAC-Based Systems
-Less accurate
-In use in more hospitals
-Less efficient (longer treatment times)
http://www.radionics.com/resources/patient/xknife_description.shtml
CyberKnife
-Can treat most regions of body
-w/ Stereotactic frame, can approach accuracy of LINAC or GammaKnife
-Real-time frameless stereotaxy can be used
四、 the knowledge system of RT general clinic
肿瘤放射治疗的各种适应症 治疗并发症的临床处理技术
Oncology 肿瘤病因及其流行病学关系 肿瘤的分期分形 肿瘤的生长规律及其引流方式 肿瘤的临床诊断方法
radiobiology Physics of radiation therapy and clinic DosimetryPhysics of radiation therapy and clinic Dosimetry
五、 Introduction of radiation Physics
1. radiation physics is branch of medical
physics
Physics of Medical Imaging 医学影像物理学
Physics of Radiation Therapy 放射治疗物理学
Nuclear Medical Physics 核医学物理学
Definition of medical imaging physics
定义:医学影像物理学是用成像的物理原理和方法设计的各种成像装置,采集人体内部的解剖学、生理学和病理学的各种信息并实现可视化的科学。
主要工作内容:该学科提供新的成像仪器和设备的设计原理和方法,改进这些仪器和设备的性能,对临床使用的仪器设备进行质量控制,对各种成像装置形成的图像进行综合分析和集成、为管理和通讯这些医学图像提供新方法和新技术,研制和开发及以这些新方法和新技术为基础的医学软件包。
The introduction of Medical Physics home and abroad国内外医学物理学教育概况
American : The AAPM ( American Association
of Physicists in Medicine ) was established in
1958. In 1999,there were over 5000 members
in AAPM. About 2/3 of them work in the field of
radiation therapy,others in imaging diagnosis
and nuclear medicine.
China : Generally,the education of medical
physics is covered in biomedical engineering.The
subject and courses mostly lay particular stress on
medical engineering or medical imaging devices.
Table 1 : in 1997
Physicist in radiation therapy
Physician in radiation therapy
423 persons 3440 persons
The introduction of Medical Physics home and abroad国内外医学物理学教育概况
1993年, AAPM在“医学物理学硕士学位的教学计划”中,列出10门课程位最低要求:
Anatomy and Physiology 解剖学和生理学 Imaging Diagnosis 影像诊断学 Electronics 电子学 Health Physics—radiation protection
保健物理 ---- 辐射防护 Nuclear medicine 核医学
Medical and Biology Physics 医学及生物学中的物理学 Radiobiology 放射生物学 Radiation physics and Metrology 放射线物理学和计量学 Physics of Radiation Therapy 放射治疗物理学 Imaging Physics 影像物理学
1993年, AAPM在“医学物理学硕士学位的教学计划”中,列出10门课程位最低要求:
2 、 The contents of the physics of radiation therapy
Definition of radiation
dosimetry 研究放射治疗过程中,不同射线在人体组织中能
量转移、沉积、分布特点;不同种类射线在不同照射方式下射线剂量的计算方法,以及为达到一定的剂量分布所采取的治疗放射的一种技术方法。
2 、 The contents of the physics of radiation therapy
Structure of matter and nuclear transformation
核物理基础 Interactions of ionizing radiation
电离辐射与物质的相互作用 Measurement of ionizing radiation
电离辐射的测量 Devices for radiation therapy 放射治疗设备 X(γ) ray therapy X ( γ )射线射野剂量学
Electron beam therapy 高能电子束射野剂量学 Brachytherapy 近距离照射剂量学 Treatment planning 治疗计划的设计 Development of therapy technology 治疗技术的进展 Timing and dose fraction in RT 时间、剂量分次 Quality Assurance and Quality Control 质量保证和质
量控制
Reference Books The Physics of Radiation
Therapy , SECOND EDITION , written by
Williams and Wilkins
Review of Radiation Oncology Physics – A
Handbook for Teachers and Students