Radiation Protection II

Sofia Skyttner, MSc
2019

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Who is here today?

Any question = good question!

Ministry of Information Photo Devision Photographer

National Authority in Radiation Protection

Swedish Radiation Safety Authority

Strålsäkerhetsmyndigheten (SSM)

Strålskyddslagen (2018:396)

1 § Humans, animals and environment shall be protected to the harm of radiation
https://www.riksdagen.se/sv/dokument-lagar/dokument/svensk-forfattningssamling/stralskyddslag-2018396_sfs-2018-396

Strålskyddsförordning (2018:506)

Föreskrifter (SSM FS 2018-XX)

Strålskyddslagen (2018:396)

1 § Syftet med denna lag är att skydda människors hälsa och miljön mot skadlig verkan av strålning.

2 § Lagen är indelad i följande kapitel:

1 kap. Lagens syfte och innehåll
2 kap. Lagens tillämpningsområde
3 kap. Grundläggande bestämmelser om skydd mot joniserande strålning
4 kap. Arbetstagares exponering för joniserande strålning
5 kap. Allmänhetens och miljöns exponering för joniserande strålning
6 kap. Tillstånd och anmälan i fråga om joniserande strålning
7 kap. Tekniska anordningar som kan alstra icke-joniserande strålning
8 kap. Tillsyn
9 kap. Straff och förverkande
10 kap. Tystnadsplikt, överklagande och avgifter

Strålskyddsförordning (2018:506)

1 kap. Förordningens innehåll
2 kap. Dosgränser
3 kap. Optimering
4 kap. Andra bestämmelser om skydd mot strålning
5 kap. Tillstånd och anmälan
6 kap. Dokumentation, information och samtycke
7 kap. Andra bestämmelser om undantag och dispenser
8 kap. Tillsyn
9 kap. Straff, överklagande och verkställighet

https://www.riksdagen.se/sv/dokument-lagar/dokument/svensk-forfattningssamling/stralskyddsforordning-2018506_sfs-2018-506

Regulations of SSM

SSMFS 2018:1 Strålsäkerhetsmyndighetens föreskrifter om grundläggande bestämmelser för tillståndspliktig verksamhet med joniserande strålning
SSMFS 2018:2 Strålsäkerhetsmyndighetens föreskrifter om anmälningspliktiga verksamheter
SSMFS 2018:5 Strålsäkerhetsmyndighetens föreskrifter och allmänna råd om medicinska exponeringar
SSMFS 2018:9 Strålsäkerhetsmyndighetens föreskrifter om godkända persondosimetritjänster
SSMFS 2014:4 Strålsäkerhetsmyndighetens föreskrifter och allmänna råd om laser, starka laserpekare och intensivt pulserat ljus

(FS = Föreskrift)

Reports of SSM

SSM Report 2009:03 National Survey on justification of CT examinations in Sweden
SSM Report 2010:14 Patientdoser från röntgenundersökningar i Sverige (2005-2008)
SSM Report 2012:23 Samlad strålsäkerhetsvärdering av hälso- och sjukvård
SSM Report 2013:11 Mätmetoder för bestämning av stråldoser till ögats lins

International Organizations in Radiation Protection

UNSCEAR - United Nations Scientific Committee on the Effects of Atomic Radiation
Assess and report on levels and effects of ionizing radiation exposure

IAEA - International Atomic Energy Agency
Safety fundamentals, requirements, guides & practices

ICRP - International Commission on Radiological Protection
Providing recommendations and guidance on all aspects of (ionizing) radiation protection
Publications: http://www.icrp.org/publications.asp

IAEA

Other international organizations

AAPM - American Association of Physicists in Medicine

RSNA - Radiological Society of North America

ACR - American College of Radiology

IRPA - International Radiation Protection Association

IPEM - Institute of Physics and Engineering in Medicine

…and many more!

Principles of Radiation Protection

Justification & Optimization

Nevit Dilmen

Justification & optimization

Toolkit to handle following issues

Radiation safety authorities & organizations
Protection quantities
Risk: late and acute effects
Distance, time & shielding
Categorization of staff and rooms
X-ray techniques that yield high doses
Special patient subgroups
Radiation related accidents & research

Patient of today...?

sculpture_fat_vs_skinny
紫流 (left)
All exams should be justified and optimized!

The principle of justification

X-rays in medical imaging should do more good than harm and
benefit-to-risk-ratio should be kept…

…As High As Reasonably Achievable (AHARA)

Individual (or societal) benefit should
be higher than the detriment it causes.

The principle of optimization

Optimization is a cyclic multidisciplinary process primarily involving:

Radiologist
Radiographer
Medical physicist

Without loosing diagnostics in image quality
patient dose should be kept…

…As Low As Reasonably Achievable (ALARA)

Choosing between image modalities, diagnostic tasks, optimization strategies & dose sparing techniques

Radiation protection team work

Radiologist + medical physicist + radiographer + …

Craig Taylor
… + surgeon + surgery nurse + medical engineer + contact person + radiation agent (strålskyddsombud) + remittent (regarding referals) + intensive care nurse + …

Radiation protection organization

radiation_protection_organization

Know YOUR who/what/when/how!

Radiation Protection Organization = Multiplication Table

batman"
Adrianogon

How to assess risks related to medical X-rays?

Formal system for a feasible and structured approach to radiation protection!

To assess dose…

…use reference anatomical and physiological models of man

To assess hazards…

…use molecular and cellular studies

To assess probability of detriment…

…use animal experiments; epidemiology

The probability of the effect occurring,
increases with dose, but not its severity

Additive risk for cancer

Stephen David Williams

LNT model, from Hiroshima/Nagasaki data

At low doses...?

Contradictory results…!

Lawrence Berkeley National Laboratory
B - the precautionary principle (försiktighetsprincipen)!

100 individuals exposed to 100 mSv...

Lamiot

Acute (deterministic) effects - staff

Rakesh Ahuja, MD
Radiation induced catharact, equivalent dose > 0.5 Sv

The severity of the effect occurring increases with dose, but not its probability

SSM dose limits

Effective dose

staff, 20 mSv/year

(patient family member: 1 mSv/year, patient: no dose limit)

Equivalent dose

fetal dose, 1 mSv/pregnancy
eye lens dose, 15 mSv/year
skin & extremities, 500 mSv/year

Karolinska investigation limits

H_p(10)

staff, 5 mSv/year (i.e. 0.5 mSv/month)

H_p(0.07)

eye lens dose, 5 mSv/year (i.e. 0.5 mSv/month)
skin & extremities, 50 mSv/year (i.e. 5 mSv/month)

Dosimeters: http://www.landauer.se/dosimetri-service/

Natural radiation: 1 mSv/year

skyddat_omrade
NASA Goddard Space Flight Center (left)

Category B: supervised area (skyddat område)
Category A: controlled area (kontrollerat område)

Upgrade to A-team...?

A (risk to exceed effective dose 6 mSv/year)

Surgeons/radiologists/nurses (angio-/intervention)

B (risk to exceed effective dose 1 mSv/year)

Nurses & physicians in anesthesia/intensive care
Surgery nurses & surgeons (C-arm)
Radiographers & radiologists (CT/conv X-ray)
Biomedical scientists (pediatric angio)
Engineers & medical physicists (all modalities)

Radiation protection dose quantities

dose_concept
Sofia Skyttner
Example

CT head examination

Absorbed dose to brain = 50 mGy
Equivalent dose to brain = 50 mSv
Effective dose for exam = 2 mSv

Radiation protection dose quantities

Doug Sim

Most radiosensitive organs

Organ	Tissue weighting factor
Breasts	0.12
Colon	0.12
Lung	0.12
Red Bone Marrow	0.12
Stomach	0.12
Gonads	0.08
Whole body	1.00

Other radiosensitive organs

Organ	Tissue weighting factor
Bladder	0.04
Liver	0.04
Oesophagus	0.04
Thyroid	0.04
Skin	0.04
Bone surface	0.01
Salivary glands	0.01
Brain	0.01
Remainder (*)	0.12

(*) Adrenals, Extrathoracic region, Gall bladder, Heart, Kidneys, Lymphatic nodes, Muscle, Oral mucosa, Pancreas, Prostate (M), Small intestine, Spleen, Thymus, Uterus/cervix (F)

Effective dose – when and how?

Effective dose for comparing…

…different diagnostic procedures
…similar procedures in different hospitals and countries
…different technologies for the same medical examination

Organ dose for…

…detailed retrospective dose and risk assessments after exposure of individuals
…epidemiological studies (i.e. study and analysis of the patterns, causes, and effects of ionizing radiation in defined populations)
…accidents involving ionizing radiation

Reference level is NOT a dose limit

Diagnostic Standard Dose

DSD, Diagnostisk standarddos
Delivered by hospitals

Diagnostic Reference Level

DRN, Diagnostisk referensnivå
Recommendations by authorities

There are no dose limits regarding patients,
but irradiation must always be justified and optimized

Effective dose in diagnostic radiology

Source of exposure	Effective dose
Dental X-ray	0.005 mSv
Chest X-ray (single projection)	0.02 mSv
Scull X-ray	0.06 mSv (*)
Mammography	0.4 mSv
Lumbar Spine X-ray	1 mSv
Head CT Scan	2 mSv
Chest CT Scan	8 mSv
Abdomen & Pelvis CT Scan	15 mSv

(*) Comparable to exposure during transatlantic flight

Special patient subgroups

X-ray techniques that yield high doses

Computed tomography
Angiography & intervention

Of special concern due to inclusion of healthy individuals

Mammography screening
Medical research studies

Patient groups that require special attention

Pediatric patients
Pregnant women

Acute (deterministic) effects - patient

LK Wagner

Effect	Skin dose threshold	Single-dose Onset
Early transient erythema	2 Gy	Only hours
Temporary hair loss	3 Gy	~3 weeks

Functional loss of irradiated organ or tissue, threshold dose exist, appear after days/weeks

Acute (deterministic) effects - patient

Effect	Skin dose threshold	Single-dose Onset
Main erythema	6 Gy	~10 days
Permanent hair loss	7 Gy	~3 weeks
Dermal atrophy	10 Gy	>14 wk (1st phase), >1 yr (2nd)
Induration (fibrosis)	10 Gy	differs
Telangiectasia	10 Gy	> 1 year
Late dermal necrosis	>12 (?) Gy	> 1 year
Dry desquamation	14 Gy	~4 weeks
Late erythema	15 Gy	~6-10 weeks
Moist desquamation	18 Gy	~4 weeks
Secondary ulceration	24 Gy	> 6 weeks

Radiation dose indicators...?

DAP - Dose-Area Product (Gycm²)
AK - Air-KERMA (mGy)
PSD - Peak Skin Dose ≈ AK
CTDIvol - Volume Computed Tomography Dose Index (mGy)
DLP - Dose Length Product (mGycm)

Note:

DAP unity prefix can vary between vendors…!
Ex: Gycm² , mGydm², etc…

Alarm levels for angio/intervention

AK (Air Kerma)	To do
3000 mGy	Inform patient, dose report to medical physicist
10000 mGy	Inform patient, referral to dermatologist

Note:

2000 mGy is fractional target dose at radiotherapy

Subgroup alarm levels

Interventional cardiac procedures

Procedure	DAP¹ (3 Gy equivalent)	DAP² (10 Gy equivalent)
Coronar Angio	550 Gycm²	1950 Gycm²
PCI	200 Gycm²	800 Gycm²
Coronar Angio + PCI	300 Gycm²	1050 Gycm²
TAVI	250 Gycm²	900 Gycm²

1 Inform patient, dose report to medical physicist
2 Inform patient, referral to dermatologist

X-ray tube angle: PA = best!

angulation
Sofia Skyttner

Exception: neonatal procedure where pat is placed directly on the detector in AP-position

Use zoom function sparsely...

Ha1_zoom
…and if possible:

Normal dose level (avoid high dose)
Low pulsed radiation (avoid continous/30 images per sec)

Simple steps to minimimze YOUR dose!

combined_rad_prot_actions
Sofia Skyttner
Read more: Geijer et al Eur. Radiol. 12 (2002)

Mammography screening

Compression (a.k.a. kompression)
Improved image quality
Less patient (and staff) dose

National Cancer Institute, Bill Branson

Research study including radiation...?

Flazingo Photos
Strålskyddskommitté- & Etikansökan

Children more radiosensitive

age-related_risk
Sofia Skyttner
Läs mer: ICRP Publication 60

Guidelines in pediatric X-ray

Dedicated equipment that allow for

High kV-short exposure time techniques
Easy grid (raster) removal
Flexible AEC (chamber selection)

Special care

Consider additional beam filtration
Avoid antiscatter grids for the smallest children, or use low ratio grids (8:1)
Use low dose detectors (i.e. high DQE digital detectors)
Use low dose fluoro (possibly replace conv X-ray)
Use TCM in CT and/or scan protocols adjusted to age/size
Use gonad shield for boys, not for girls & neonatal patients

Foetus - extra radiosensitive

Especially during first trimester!

Image Editor
Read more: ICRP Report 84

Pregnant patients...?

Female patients in fertile age shall always be
asked for pregnancy before X-ray!

Female pat in fertile age, vomiting for 10 days
Gastroscopy without remark, day 1
Rad ask for CT-abdomen, day 2
Radiographer do the exam
Exam shows nothing remarkable
Finally physician asks for pregnancy test, pat pregnant…!

1) Unjustified radiation of patient (and fetus)
2) Pregnancy question failed (three times…!)

X-ray of pregnant patient...?

X-ray department shall inform medical physicists about the examination if…

…fetus was either in or partly in radiation field
…fetus was not the patient

James Heilman

Termination of pregnancy...?

Generally fetus dose is: < 0.1 mSv @ conv X-ray & < 10 mSv @ CT exams

Early/mid pregnancy

Fetal dose < 100 mSv: Termination of pregnancy NOT justified based upon radiation risk
Fetal dose 100-1000 mSv: Magnitude and type of fetal damage depend on dose and stage of pregnancy, physician decision should be based upon individual circumstances