sgsmp physics course for fmh residents · sgsmp physics course for fmh residents radiation...

SGSMP Physics Course for FMH residents

Radiation ProtectionandQuality AssuranceLecture by PD Dr. Uwe Schneider

Contents

001 Radiation Protection Basics

002 Radiation Protection in in Medicine and Radiation-Oncology

003 Radiation Protection Legislation

004 Quality Assurance in Radiation-Oncology

RO

ENTG

ENTE

CH

NIK

STR

AHLE

NBI

OLO

GIE

GR

UN

DLA

GEN

RA

DIO

LOG

IE

STR

AH

LEN

PH

YSI

K

Content001 Radiation Protection Basics

• Radiation effects

• Dose definition and dose measurement

• Radiation exposure

• Radiation damage

• Radiation risk and cancer induction

• Natural radiation

• Artificial radiation

Radiation Protection Basics Effects of radiation exposureHow effective is radiation exposure?

-Radiation deposits energy in the body: in a confined volume dependent on radiation quality.

- This energy can be measured.

In the context of radiation it is true what PARACELSUS wrote:

"the dose makes the poison"

Radiation Protection Basics Measurement of dose I• the need of protection againstionizing radiation,

• the application in medicine

requires quantitative methods to determine a "dose of radiation".

The purpose of a quantitative concept of a dose of radiation is:• to predict associated radiation effects (radiation detriments)

• to reproduce clinical outcomes.

Radiation Protection Basics Measurement of dose II

Absorbed doseD = energy/mass [1 Joule/kg = 1 Gy]

can be measured, but:- not accounted for biological effects

- different organ sensitivity (with regard to the same absorbed dose)

- absorbed dose is a point dose

Radiation Protection Basics Dose definition I

X-ray exposure:0.1 Gy x 1 = 0.1 Sv

Equivalent dose

Accounts for the effectiveness of the given radiation in inducing biological harm:

HT,R = DT x wR in Sievert (Sv)

DT = absorbed dose in GywR = weighting factor for radiation

quality

Neutron exposure:0.1 Gy x 20 = 2 Sv

Radiation Protection Basics Dose definition II

20Alpha-particles, heavy ions

5Protons (energies larger than 2 MeV)

51020105

Neutrons: energy-range - below 10 keV- 10 keV - 100 keV- 100 keV - 2 MeV- 2 MeV - 20 MeV- larger then 20 MeV

1Electrons, all energies

1Photons, all energies

Weighting factor wRRadiation quality and energy

Weighting factors (StSV Anhang 1)

Radiation Protection Basics Dose definition IIIFrom absorbed dose to equivalent dose

Radiation Protection Basics Dose definition IV

Irradiation of thyroid:0.1 Sv x 0.05 = 0.005 Sv

Effective dose

Accounts for different organ sensitivities:

E = ΣΤHT x wT in Sievert (Sv)

HT = Equivalent dose in tissue TwT = weighting factor for tissue T

Irradiation of colon:0.1 Sv x 0.12 = 0.012 Sv

Radiation Protection Basics Dose definition V

Weighting factors for different organs (StSV Anhang 1)

0.05

0.05

0.12

0.12

0.12

0.12

0.20

Weighting factor wT

Remainders

Bone surface

Skin

Thyroid

Esophagus

Liver

Organ or tissue

Breast

0.05Bladder

0.01Stomach

0.01Lung

0.05Colon

0.05Bone marrow (red)

0.05Gonads

Weighting factor wTOrgan or tissue

Radiation Protection Basics Dose definition VI

From equivalent dose to effective dose

Radiation Protection Basics Dose limits I

Dose limits:

- Dose limits are defined for specific person groups

- Dose limits are not applicable to medical exposures- resulting from diagnostic procedures applied in diagnosis- therapeutic procedures applied in treatment of disease.

- Dose limits are not applicable to natural exposures

- Dose limits are defined by the Radiation Protection legislation (based on ICRP-report 60, 1990)

Dose limits IIRadiation Protection Basics

Public exposure

radiation

exposed to

Occupationally

Group

1

1

2

5

500

150

20

Dose limit in mSv/a

Effective Dose(without environmental and medical exposure)

Pregnant workers:incorporated dose

Pregnant workers at abdomen(Equivalent dose)

Persons between 16 and 18 years of age (effective dose)

Skin, hands, feet (Equivalent dose)

Eye lens (Equivalent dose)

Effective dose

Location and dose quality

Annual dose limits from StSV (22.06.1994)

Radiation ExposureRadiation Protection Basics

A radiation exposure is each event during which dose can be absorbed

Radiation exposure can happen by:

1. Irradiation from outside: Source is outside of the body or skin is contaminated.

2. Irradiation from inside:Source is gaseous, fluid or aerosol and be inhaled or eaten.

Radiation exposures are divided into three categories:• Occupational exposure.• Medical exposure.• Public exposure.

Radiation InjuryRadiation Protection Basics

Deterministic effects

• Radiation injury at large dose: H>0.5 Sv

• Complication is a function of Equivalent dose and Volume

• Certain to occur above threshold level for dose

Stochastic effects

• Malignancies and hereditary effects

• Probability of tumorinduction is function of effective dose

Radiation Protection Basics Deterministic effectsLethal Dose LD50: 4 Sv

Ulceration/Perforation5065Stomach

Pneumonitis17.524.5Lung

30

10

50

55

65

23

Dosis TD5/5* [Gy]

Liver

Eye lens

Optic nerve

Skin

Bladder

Kidney

Organ

Liver failure

Cateract

Blindness

Necrosis/Ulceration

Bladder contracture

Nephritis

Endpoint

40

18

65

70

80

28

Dosis TD50/5* [Gy]

*probability of 50% and 5% complication within 5 years, respectivelyData from Emami et al, Int J rad Onc Biol Phys 1991 21 109

Stochastic effectsRadiation Protection Basics

• The likelihood of stochastic effects is proportional to the effective dose received without a dose threshold.

• For radiation exposures far beyond the threshold dose

• Comparisons on the basis of effective dose:x-rays, Radiation-Oncology, natural exposures

Radiation Protection Basics Radiation risk

Estimation of radiation risk:

Source: Epidemiological data from the Atomic-bomb survivors with extrapolation to low dose:

For radiation protection we assumeca. 50 cancer deaths per 1 Million persons per 1 mSv.

= 5% / Sv(linear dose-response relationship)

Radiation Protection Basics Cancer induction

Dose-response relationships for radiation injury:a) Linear for cancer risk and

b) Steep gradient with threshold for acute radiation injuries

c) spontaneous, not radiation related cancer

Natural radiation IRadiation Protection Basics

Biological effects of radiation:- During it’s development life on earth was exposed to ionizing radiation.

- At the beginning of life radiation exposure was much larger than nowadays.

- Radiation contributed significantly to the evolution of life.

Natural radiation IIRadiation Protection Basics

Cosmic radiation exposure: - radiation from sun and outer space - is increasing with increasing height - mean exposure: 0.34 mSv/a

Natural radiation IIIRadiation Protection Basics

Primordial radio-nuclides

- Primordial radio-nuclides are left over from when the world and the universe were created.

-They are typically long lived, with half-lives often on the order of hundreds of millions of years

-Most of these sources have been decreasing, due to radioactive decay since the formation of the Earth

-As a consequence some decay chains died out. Example: Plutonium-Neptunium-decay-chain

Some nuclides like 238U have several members of its decay chain

Natural radiation IVRadiation Protection Basics

Terrestrial radiation: - from the earth crust - major sources are natural radium,

uranium and thorium- Swiss alpes < 1.5 mSv/a- Swiss Jura < 0.45 mSv/a

Natural radiation VRadiation Protection Basics

Radioactivity in gemstones

- Exposed to radiation in order to change their color(Topas, Rubine, Saphire, etc.)

- Irradiation with electrons and x-rays is harmless

- Irradiation with neutrons, can produce other radio-nuclides (nuclear reactions) – up to 2000 Bq pro g

Natural radiation VIRadiation Protection Basics

Radiation inside the human body: - Some of the essential elements that make up the human body, mainly potassium and carbon, have radioactive isotopes that add significantly to our background radiation dose.

- Incorporated with food and water mainly in muscle.- Water: nuclides from natural decay chains.- 0.45 mSv/a

Natural radiation VIIRadiation Protection Basics

Radon and decay products: - Radon gas is a decay product of uranium, which is relatively common in the earth's crust.

- Radon has a short half-life (4 days) and can be inhaled and remain lodged in the lungs. It decays into other solid radioactive nuclides, causing continued exposure.

Natural radiation VIIIRadiation Protection Basics

Radon and decay products: 1.6 mSv/a (0.3 ... 100 mSv/a)

Natural radiation IXRadiation Protection Basics

Summary of natural radiation in Switzerland

Natural radiation XIRadiation Protection Basics

Total radiation exposure in Switzerland due to natural radiation exposure

2.8 mSv/a (1.0 ... 150 mSv/a)

approximately 5% of 2’500 fatal cancers per year per 1 Million citizens originate from natural radiation (without Radon).

Radiation Protection Basics Artificial radiation sources INuclear expolsions and fallout: - Frequent above-ground nuclear explosions between 1950-1965- 50% local fallout, rendering the immediate surroundings highly radioactive- 50% carried longer distances in the atmosphere; fallout due to rain. - external and internal radiation exposure- < 0.01 mSv/a

Radiation Protection Basics Artificial radiation sources IISmall sources (Several materials contain radioactive nuclides):

- Illuminated displays, Glas, tiles, etc. < 0.02 mSv/a

- flying (cosmic radiation exposure)

- Tobacco: 5 mSv/a

Radiation Protection Basics Artificial radiation sources III

Nuclear reactors: - Release of certain amounts of radioactive contamination

< 0.015 mSv/a

Radiation Protection Basics Artificial radiation sources IVTschernobyl accident (Exposure of Swiss citizens):- Between 1986 and 2000 the mean effective dose was approximately 0.5 mSv(Maximum 5 mSv)

- Today mean effective dose: 0.01 mSv

Radiation Protection Basics Artificial radiation sources V

Other sources: - Industry, Research, Hospitals < 0.03 mSv/a

Control unit of a liquid waste storage unit: monitoring of dose limits. Liquid waste from hospitals may be radioactive contaminated and must be stored before releasing into canalisation.

Radiation Protection Basics Artificial radiation sources VI

Medicine:- Radiation exposure in Radiology ~1 mSv/a- radiation exposure in Nuclear Medicine and Radian-Oncology ~0.05 mSv/a

Nuclear Medicine

X-rays

Radiation Protection Basics Artificial radiation sources VII

Total artificial radiation in Switzerland:

1.2 mSv/a (thereof 1 mSv/a from medicine)

002 Radiation Protection in Medicine and Radiation-Oncology Content

• Radiation protection when using diagnostic sources

• X-ray imaging in Radiation-Oncology

• MV imaging in Radiation Oncology

• IMRT and Protons

• Radiation Protection of personal

Radiation exposure of the patientRadiation Protection in Medicine

Radiation exposure in Radiation Oncology

Diagnostic radiation+ Simulation+ CT imaging, virtual simulation, 4D-CT + PET imaging, PET-CT imaging+ IGRT: kV-Imaging+ IGRT: ConeBeam-CT+ Imaging during radiation therapy (gated radiotherapy)

Therapeutic radiation+ IGRT: MV imaging+ IGRT: MV-ConeBeam-CT+ Radiation therapy+ IMRT

Radiation exposure of the patient

Radiation Protection in Medicine

Radiation exposure during diagnostic x-rays

- Surface dose is largest dose in the patient- Organ dose is usually in the order of mSv

If you compare with natural radiation keep in mind:- Dose rate for diagnostic application can be 1’000’000 larger than with natural exposure.

- Effectiveness of radiation is increasing with increasing dose rate!

Radiation Protection in Medicine Example: Effective dose

Radiation exposure of the spineCalculation of effective

dose:

E =

E = 0.7 mSv

0.5 mSv x 0.12 +0.9 mSv x 0.12 +2.0 mSv x 0.20 +0.1 mSv x 0.12 +1.0 mSv x 0.12

Stomach0.5 mSv

Lung0.1 mSv

Colon0.9 mSv

Bone marrow1 mSvOvaries

2 mSv

Effective DoseRadiation Protection in Medicine

Fluoroscopy, intervenitonalx-rays> 200 mSv

Scull0.5 mSv

ThoraxTeeth

0.1 mSv

Mammography0.2 mSv

1 mSv

2 mSv

5 mSv

10 mSv

20 mSv

25 mSv

EffectiveDose

General public

Occupational exposed

Annual limit

CT-ScullPelvis

Thoracic spineAbdomen

CT-ThoraxCT-Abdomen

Bowel

Type of X-ray examination

Natural Radiation

Radiation Protection in Medicine Dose ranges: x-rays

Dose intensive examinations > 0.5 mSv

- CT examinations- Serial exposures- Fluoroscopy

Dose

0.5 mSv

Low dose range < 0.5 mSv

- Single exposures of the Thorax- Single exposures of extremities- Single exposures of scull

Frequency of the number of x-ray examinations


Low dose range61%

Teeth16%

large dose9%

CT2%

Pelvis, Abdomen

12%

Total large dose 23%

If you look at frequency the low dose-range examinations contribute most

Proportion of collective dose


CT29%

large dose51%

Low dose range7%

Pelvis, Abdomen

12%Teeth1%

Gesamter Hochdosisbereich92%

If you look at total dose the dose-intensive examinations contribute most

SimulationRadiation Protection in Medicine

Simulation is fluoroscopy

Radiation-induced Skin Injuries from Fluoroscopy

Dose intensive examination with doses up to 100 mSv or more

In case of an accident much more:

4D-CT imaging IRadiation Protection in Medicine

- Motion is registered during CT acquisition

- Patient is scanned multiple times at each couch position

4D-CT imaging IIRadiation Protection in Medicine

CT scans are sorted regarding the breathing cycle

3D imaging 4D imaging

Effective dose 3D

for head scan: 10 mSv

for abdomen scan: 20 mSv

Effective dose 4D (maximum)

100 mSv

200 mSv

IGRT kV/MV imagingRadiation Protection in Medicine

kV imaging

Dose for 1 exposure ~ 0.1 … 1 mSv

Treatment with 30 fractions and two Setup-fields:

Dose ~ 6 … 60 mSv

MV imaging

Dose for 1 exposure ~0.5 … 5 mSv


Dose ~ 30 … 300 mSv

IGRT cone Beam CTRadiation Protection in Medicine

MV Cone beam CT

Dose for 1 exposure ~ 20 … 50 mSv


Dose ~ 600 … 1500 mSv

kV Cone Beam CT

Dose for 1 CT~ 10 … 20 mSv


Dose ~ 300 … 600 mSv

Attention:Local dose can be large!Example: H&N irradiation 3-5 Gy extra Parotid dose

Impact of IMRT IRadiation Protection in Medicine

Conformal 3D irradiation

Small volume with high dose Large volume with low dose

Beam-On-Time static < Beam-on-time IMRT

IMRT

72 Gy

4 Gy

Impact of IMRT IIRadiation Protection in Medicine

Comparison of different treatment techniques for prostate cancer with regard to cancer risk

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

3D-15MV IMRT-6MV IMRT-15MV Protonen(passiv)

Protonen(aktiv)

Can

cer r

isk

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

3D-15MV IMRT-6MV IMRT-15MV Protonen(passiv)

Protonen(aktiv)

Can

cer r

isk + 18% + 23%

- 46%

+ 56%

+ 2%

+ 28%

- 52%

+ 2%

Moderate increase of cancer risk when using IMRT

Impact for the patientOberservations with Hodgkin-patientsCumulative cancer risk for a patient irradiated at 30 years of age is at the age of 60:Males: 18% (Comparison to general population: 7%)Females: 27% (Comparison to general population: 9%)


Content003 Radiation protection legislation

• Governmental regulation

• Registration and license

• Responsibilities in a Radiation-Oncology clinic

• Radiation protection for the personal

Radiation protection legislation LegislationSwiss radiation protection legislation is based upon international recommendations of the ICRPOrganisation in Switzerland:

Regulatory authority for industrySUVASchweizerische Unfall-Versicherungsanstalt

Regulatory authority for nuclear installationsHSKHauptabteilung für dieSicherheit von Kernanlagen

Regulatory authority for medicine, teaching and researchBAGBundesamt für Gesundheit

Implementation rulesDepartments

Radiation protection regulation (StSV) from 1994Bundesrat

Radiation protection legislation (StSG) from 1991Parlament

Principles

Justification- necessity and justification- benefit- benefit >> radiation risk

Optimization- ALARA

Dose limits- for general public and occupational exposed persons

- no dose limits for patients

A RAAs Low As Reasonably Achievable

Radiation protection legislation

In therapeutic medical exposure, optimization is achieve by keeping exposure of normal tissue ALARA consistent with delivering the required dose to the planning target volume (PTV).

Radiation protection legislation How to get a licenseSetup and operation of a medical linear accelerator or a x-ray diagnostic device needs a license

Supports the lincenseeContractor

Applies at BAG for a license- Radiation protection building plans- Radiation protection calculations

Licensee(legal person)

Conditions fulfilled

BAG charters the license

BAG inspection after installation

Inspection ok

License with individual conditions (usually for 10 years valid)

Radiation protection legislation Operation of a Linac

The operation of a linear accelerator requires:

- Existence of a medical expertise (“ärztliche Sachkunde”)- Assignment of a radiation protection officer (“Strahlenschutzsachverständige”)

- Liability insurance- The equipment must be up to date- License of the BAG- Implementation of a QA program- Comply with radiation protection legislation

Responsibilities Radiation protection legislation

- all patients which accumulate more than 1 mSv of dose- responsible for using their personal dosimeter

Occupational exposed persons

- Qualification for Radiation-Oncology („Facharzt“)- medical responsibility for diagnostic and therapeutic application of ionising radiation to patients

Medical expert(Radiation Oncologist)

- qualification as a Medical Physicist- implement radiation protection rules in the clinic- responsibility for radiation protection

Radiation protection officer(Medical Physicist)

- responsibility that the hospital complies to radiation protection legislation

- assign radiation protection officer- must guarantee safety in the hospital

Licensee(legal persons, usually hospital administration)

Personal dosimetry I Radiation protection legislation

Determination of radiation dose (Dosimetry) (Art.42ff):

The licensee must determine radiation exposure of all occupational exposed persons in his hospital, each person individually and on a monthly basis, by an accrediteddosimetry lab.- He has to inform his employees about the measurements.- he hast to pay the costs for the dosimetry.

Personal dosimetry II Radiation protection legislation

Personal dose report (Art.57):

The licensee has to register the accumulated dose in the personal radiation report on a yearly basis.

When employment stops the occupational exposed person receives the dose report with the accumulated dose from the licensee.

004 Quality Assurance in Radiation-Oncology Content

• Definition and organisation of quality assurance

• Quality assurance for equipment

• Quality assurance for treatment delivery

QA in radiotherapy IQuality Assurance

Quality assurance in radiotherapy"Quality Assurance in Radiotherapy" is all procedures that ensure

consistency of the medical prescription, and safe fulfillment of that radiotherapy related prescription.

Examples of prescriptions:

• the dose to the tumor (to the target volume)

• minimal dose to normal tissue

• adequate patient monitoring aimed at determining the optimumend result of the treatment

• minimal exposure of personnel

QA in radiotherapy IIQuality Assurance

Quality standards is the set of accepted criteria against which the quality of the activity in question can be assessed.

In other words: Without quality standards, quality cannot be assessed.

Quality standards in radiotherapyRecommendations of international organisations (WHO, ESTRO,…)

Regulation by the Swiss authorities: “Linear accelerator ordinance” (Beschleunigerverordnung, BeV, 25.01.2005):

“The licensee has to establish a ongoing QA-program based on international accepted standards, which incorporates both, the medical aspects of radiotherapy and the equipment-specific and medical physics issues.”

QA in radiotherapy IIIQuality Assurance

Why does a radiotherapy center need a quality system?

1. You must establish a QA program because it is law!

2. It helps to provide “the best treatment”.

3. It provides measures to approach the following objectives:

Reduction of uncertainties and errors (in dosimetry, treatment planning, equipment performance, treatment delivery, etc.)

Reduction of the likelihood of accidents and errors

Providing reliable inter-comparison of results among different radiotherapy centers

Full exploitation of improved technology

QA for equipment IQuality Assurance

General structure of a quality assurance program for equipment (under the responsibility of the Medical Physicist)

QA for equipment IIQuality Assurance

Acceptance

Acceptance of equipment is the process in which the supplier demonstrates the baseline performance of the equipment to the satisfaction of the customer.

Commissioning

Commissioning is the process of preparing the equipment for clinical service.

Quality control

An ongoing program of regular performance checks to verify that treatment equipment remain consistent within accepted tolerances throughout its clinical life.

QA for treatment delivery IQuality Assurance

Patient charts (Radiation-Oncologist and Medical physicist)

The radiation chart is accompanying the patient during the entire process of radiotherapy.

Basic components of a patient treatment chart:• patient name and ID,• photograph,• initial physical evaluation of the patient,• treatment planning data,• treatment execution data,• clinical assessment during treatment,• treatment summary and follow up.

Any mistakes made at the data entry of the patient chart are likely to be carried through the whole treatment.

QA of the patient chart is therefore essential!

QA for treatment delivery IIQuality Assurance

Portal imaging (Radiation-Oncologist and Therapist)

Portal imaging is frequently applied in order to check geometricaccuracy of the patient set-up with respect to the position of the radiation beam.

Process control requires that local protocols must be established to specify:

• who has the responsibility for verification of portal images (generally a clinician), and

• what criteria are used as the basis to judge the acceptability of information conveyed by portal images.

QA for treatment delivery IIIQuality Assurance

Record-and-verify systems (Medical physicist and Therapist)

At the time of treatment, patient related parameters are identified at the treatment machine and, if there is no difference, the treatment can start.

If discrepancies are present this is indicated and the parameters concerned are highlighted. Treatment cannot start.

In-vivo dose measurements (Medical physicist)

There are many steps in the chain of processes which determine the dose delivery to a patient. Each of these steps may introduce an uncertainty.

It is therefore necessary for specific patient groups or for unusual treatment conditions to use in-vivo dosimetry as an ultimate check of the actual treatment dose.

sgsmp physics course for fmh residents · sgsmp physics course for fmh residents radiation...

Documents