At the position d max of maximum energy loss of radiation, the number of secondary ionizations products peaks which in turn maximizes the dose at that.

Slides:



Advertisements
Similar presentations
How is radiotherapy given Radiotherapy can be given in two ways: from outside or inside the body. External radiotherapy is the most common method of treatment.
Advertisements

Modifiers of cell survival: Linear Energy Transfer Lecture Ahmed Group
Cloud Radar in Space: CloudSat While TRMM has been a successful precipitation radar, its dBZ minimum detectable signal does not allow views of light.
NE Introduction to Nuclear Science Spring 2012
Energy deposition and neutron background studies for a low energy proton therapy facility Roxana Rata*, Roger Barlow* * International Institute for Accelerator.
Photon Beam Monitor-Unit Calculations
Charged Particle Radiation
10-1 CHEM 312 Lecture 10: Part 1 Radiation Reactions: Dosimetry and Hot Atom Chemistry Readings: §Reading: Modern Nuclear Chemistry, Chap. 17; Nuclear.
BME 560 Medical Imaging: X-ray, CT, and Nuclear Methods
Radiation Exposure, Dose and Relative Biological Effectiveness in Medicine Background Image:
Dose. Energy Gained Particles lose energy in matter. Eventually energy loss is due to ionization. An important measure is the amount of energy gained.
Tumour Therapy with Particle Beams Claus Grupen University of Siegen, Germany [physics/ ] Phy 224B Chapter 20: Applications of Nuclear Physics 24.
Interactions of charged particles with the patient I.The depth-dose distribution - How the Bragg Peak comes about - (Thomas Bortfeld) II.The lateral dose.
Quantities and Measurements - 2 Dosimetric Quantities
03/07/2015radiation safety - level 51 Radiation safety level 5 Frits Pleiter.
LESSON 4 METO 621. The extinction law Consider a small element of an absorbing medium, ds, within the total medium s.
Radiation Dosimetry Dose Calculations D, LET & H can frequently be obtained reliably by calculations: Alpha & low – Energy Beta Emitters Distributed in.
Planar scintigraphy produces two-dimensional images of three dimensional objects. It is handicapped by the superposition of active and nonactive layers.
8.1 PRODUCTION AND CHARACTERISTICS OF X-RAYS
Alexander Brandl ERHS 630 Exposure and Dose Environmental and Radiological Health Sciences.
ACADs (08-006) Covered Keywords Roentgen, gray, exposure rates, absorbed dose, dose equivalent, quality factors, linear energy transfer, relative biological.
Radiology is concerned with the application of radiation to the human body for diagnostically and therapeutically purposes. This requires an understanding.
Electron Beams: Physical Principles and Dosimetry
Photon and Energy Fluence
Radiation therapy is based on the exposure of malign tumor cells to significant but well localized doses of radiation to destroy the tumor cells. The.
Dose Distribution and Scatter Analysis
Stopping Power The linear stopping power S for charged particles in a given absorber is simply defined as the differential energy loss for that particle.
ECE/ChE 4752: Microelectronics Processing Laboratory
PAMELA Contact Author: CONFORM is an RCUK-funded Basic Technology Programme Charged Particle Therapy Treating cancer with protons and light ions Ken Peach,
Geant4: Electromagnetic Processes 2 V.Ivanchenko, BINP & CERN
Centre de Toulouse Radiation interaction with matter 1.
Resident Physics Lectures
Space Instrumentation. Definition How do we measure these particles? h p+p+ e-e- Device Signal Source.
Internal Radiation Dosimetry Lab 9. Radiation Measurement We use different terms depending on whether: 1.The radiation is coming from a radioactive source.
NE Introduction to Nuclear Science Spring 2012 Classroom Session 7: Radiation Interaction with Matter.
Using Radiation in Medicine. There are 3 main uses of radiation in medicine: Treatment Diagnosis Sterilization.
Gamma Ray Imaging Lab Tour
Medical Accelerator F. Foppiano, M.G. Pia, M. Piergentili
Calorimeters Chapter 4 Chapter 4 Electromagnetic Showers.
Alpha and Beta Interactions
3/2003 Rev 1 II.1.2 – slide 1 of 32 IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources Session II.1.2 Part IIQuantities.
Chapter 5 Interactions of Ionizing Radiation. Ionization The process by which a neutral atom acquires a positive or a negative charge Directly ionizing.
Numerical Model of an Internal Pellet Target O. Bezshyyko *, K. Bezshyyko *, A. Dolinskii †,I. Kadenko *, R. Yermolenko *, V. Ziemann ¶ * Nuclear Physics.
If information seems to be missing, make any reasonable assumptions. 1.A target has an areal density of 2.3 g/cm 2 and a thickness of 0.8 inch. What is.
Interaction Ionizing Radiation with Matter BNEN Intro William D’haeseleer BNEN - Nuclear Energy Intro W. D'haeseleer
Interaction of x-ray photons (and gamma ray photons) with matter.
415 PHT Plasma Level – Time Curve
Alhanouf Alshedi Basic Interactions of Radiation with Matter 2 ed Lecture.
AAPM TG-51 Protocol (Med Phys 26: , 1999)
Development of elements of 3D planning program for radiotherapy Graphical editor options  automated enclose of contour  correction of intersections 
Interactions of Ionizing Radiation
Chapter 5 Central Axis Depth Dose Calculations. 2 Definition of Beam Geometry The accurate delivery of a radiation dose to patient depends on the precise.
Chapter 2 Radiation Interactions with Matter East China Institute of Technology School of Nuclear Engineering and Technology LIU Yi-Bao Wang Ling.
Treatment Chart Record of patients radiation therapy history. Must contain: History and diagnosis Rationale for treatment Treatment plan Consent Documentation.
Linear Energy Transfer and Relative Biological Effectiveness
CHAPTER 3 DOSE DETERMINATION FOR EXTERNAL BEAMS
INTERACTION OF PARTICLES WITH MATTER
Electron Beam Therapy.
Dose Equivilant Rad Pro III NUCP 2331.
X-Radiation.
A system of dosimetric calculations
Outside the nucleus, the beta decay {image} will not occur because the neutron and electron have more total mass than the proton. This process can occur.
Resident Physics Lectures (Year 1)
Ch 10. A System of Dosimetric Calculations
Chapter 8 (Part 1) Measurement of Absorbed Dose
Resident Physics Lectures (Year 1)
Chapter 5 - Interactions of Ionizing Radiation
Innovations in the Radiotherapy of Non–Small Cell Lung Cancer
Hot and cold spots are common problems associated with planning:
Principles and Practice of Radiation Therapy
Presentation transcript:

At the position d max of maximum energy loss of radiation, the number of secondary ionizations products peaks which in turn maximizes the dose at that location. The dose is denned (see section on dosimetry) as total energy loss of radiation per mass. It can be formulated in terms of the activity A(t) (number of incident particles/second in cases of external beam treatment N(t)) and energy loss or stopping power dE/dx. The total absorbed dose D(t) after a period t of irradiation is expressed in terms of number of particles N(t), total amount of energy lost E R, and irradiated area A: with m, V, and  as mass, volume, and density of the exposed organs. This results in a absorbed dose D(t,d) after an irradiation period t at a certain depth d:

Within the area A each point at a certain depth d receives the same dose  ISODOSE. The absorbed dose at a certain depth d is directly proportional to the stopping power 1/   dE/dx ! A 75% 100%

 [cm 2 /g] The average dose due to energy loss of  radiation within a depth d over a period t is: The dose is directly proportional to the transfer and absorption coefficients which change with depth.

The dose distribution is less well defined compared to particle beams.

Within the area A each point at a certain depth d receives the same dose  ISODOSE. Isodose profiles are plotted in terms of the percentage depth dose %DD because absolute dose measurements are difficult. The percentage depth dose is the absorbed dose at a given depth d expressed as a percentage of the absorbed dose at a reference depth d max along the central axis of the beam. In figure above the percentage depth dose at point A is 75 %. Isodose charts are usually plotted in increments of 10 %. They depend on the beam geometry and the various absorption effects within the body tissue.

Examples of isodose profiles The isodose profile widens rapidly due to wide angle scattering. For electron beam the percentage depth dose increases with depth, the maximum range depends on the initial energy of the electron beam. For electron beam the percentage depth dose increases with depth, the maximum range depends on the initial energy of the electron beam.

For heavy ion beam the profile remains well defined but the percentage depth dose increases rapidly at well localized position due to Bragg curve behavior plus decay radiation from on-line produced activities.

For  -radiation the percentage depth dose peaks at small depths but ranges deeply into the tissue proportional to the absorption coefficient.

Cobalt 60 6 MeV 15 MeV 4 MeV The angle scattering is small, the beam profile and therefore the isodose profile remains well defined.

A carefully designed treatment plan is necessary to maximize the dose at the tumor location while minimizing the dose in the surrounding body tissue! Notice, while tumor might get maximum dose, the surrounding tissue may be exposed to at least 50 % of it which may cause problems.

Dose calculation should consider the following aspects 1.geometry of treatment 2.energy loss effects 3.straggling and widening of beam 4.backscatter

Treatment plan needs to be carefully designed, should rely on careful localization of tumor with modern imaging techniques (CT, MRI). Dose and dose losses should be simulated (three dimensional simulation).

A B C D

Typically, the prescribed dose depends on the size of the tumor and the specific organ which has been effected. The prescribed total doses range between 40 Gy to 70 Gy. For external beam therapy the dose will be administered over a period of five to six weeks with a daily dose ranging between 1.9 and 2.2 Gy/day (five days a week). The treatment time depends on the intensity of the radiation source!

For brachytherapy a radioactive source is implanted in a location near the tumor. Therefore the radiation is constant until the desired dose has been reached.

Example

For calculating the dose to be delivered geometrical aspects and backscattering have to be taken into account. Critical is the source- surface distance SSD which determines intensity losses between source and body. d is the depth of the tumor location! A dose rate of DR 1 = 1.17 Gy/min delivered over a distance of SSD 1 + d = 80.5 cm reduces over a distance of SSD 2 + d = 100 cm to: Substantial losses can occur by back scattering, the backscattered radiation will increase the dosage in the surrounding body tissue. Therefore a further modification has to be introduced by subtracting the amount of backscattered radiation BS in the body tissue.

The backscatter is defined as the ratio of scattered dose at depth d of body tissue to the scattered dose in air at the same length d.

To optimize treatment often multiple beam treatment is applied. This approach maximizes the dose at the location of the tumor and minimizes the dose in the surrounding body tissue.

Alternative options are the introduction of wedges which allow beam attenuation and absorption to shape the radiation field for optimal treat­ment.