The Dosimetry of The Dosimetry of Radiation TherapyRadiation Therapy

Wang Pengcheng 2007

pcwang@tsmc.edu.cn

Brife Introduction of Radiation Therapy and

radiation dosimetry

Wang Pengcheng

2007

Radiation Therapy ： the Myths

For many lay-people, the word radiation conjures a host of myths and misconceptions.

Radiation Therapy ： the Myths

Radiation Therapy ： the Myths

Radiation Therapy ： the Myths

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.

二、 Development of Radiation Therapy

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

关于curie介绍

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

表 1 肿瘤治疗五年生存率的变化年 代 20 世纪初 30 年

代60 年

代90 年

代五年生存率 5% 15% 30% 45%

表 2 三大治疗手段对肿瘤治愈率的相对贡献

治疗手段 手术治疗 放射治疗 化学治疗

相对贡献

22% （ 48.9% ）

18%（ 40% ）

5%（ 11.1

% ）

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

Linear accelerator

http://virtualtrials.com/jhrs.cfm

Display of treatment planning:

http://virtualtrials.com/jhrs.cfm

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

The main contents of Medical Physics

医 学 影 像 物 理 学 放 射 治 疗 物 理 学 核 医 学 物 理 学

Ò ½Ñ §Î ïÀ íÑ §

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

教材：《放射治疗剂量学》， 主编：王鹏程，人民军医出版社

肿瘤放射物理学，主编：胡逸民，原子能出版社

肿瘤放射治疗学（第三版），主编：殷蔚伯，谷铣之，中国协和医科大学出版社

Reference Books