IAEA Training Material on Radiation Protection in Cardiology

IAEA Training Material on Radiation Protection in Cardiology

International Atomic Energy Agency Talking about Radiation Dose L2 Educational Objectives 1. How radiation dose can and should be expressed, merits and demerits of each quantity for cardiology practice 2. How representative fluoroscopy time, cine time are for dose to the patient and the staff 3. Simplified presentation of dose quantities Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 2 20 mg of beta blocker Dose outside (in drug) is same as dose inside the patient body Not so in case of radiation Depends upon the absorption Different expressions for radiation intensity outside (exposure units), absorbed dose [called Dose] in air, in tissue In air Difficult to measure dose

inside the body Measure dose in air, then convert in tissue Absorbed dose In tissue Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 3 Patient dose variability in general radiology 1950s Adrian survey, UK measures of gonadal and red bone marrow dose with an ionisation chamber; first evidence of a wide variation in patient doses in diagnostic radiology (variation factor: 10,000) 1980s, European countries measure of ESD with TLDs and DAP for simple and complex procedures (variation factor: 30 between patients; 5 between hospitals) 1990s, Europe trials on patient doses to support the development of European guidelines on Quality Criteria for images and to assess reference levels (variation factor: 10 between hospitals) 2000s, NRPB, UK UK; National database with patient dose data from 400 hospitals

(variation factor: 5 between hospitals) 60 Lumbosacral joint 50 40 Patient dose distribution in EU survey 1992; lumbar spine Lateral projection 30 20 10 0 0 25 50 75 100 125 ESD (mGy) Radiation Protection in Cardiology Lecture 2: Talking about radiation dose

4 Patient doses in interventional procedures Also in cardiac procedures, patient doses are highly variables between centres Need for patient dose monitoring www.dimond3.org Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 5 Staff doses in interventional cardiology Large variability in staff exposure Need for staff dose monitoring Wu et al., 1991 Renaud, 1992 Li et al., 1995 Steffenino et al., 1996

Folkerts et al., 1997 Watson et al., 1997 Zorzetto et al., 1997 Va et al., 1998 Padovani et al., 1998 DIMOND 1999 Spain DIMOND 1999 Italy DIMOND 1999 Greece Effective dose/procedure (uSv/proc) 20 15 10 5 0 Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 6 Dose quantities and Radiation units Dose quantities outside the patients body Dose quantities to estimate risks of skin injuries and effects that have threshold Dose quantities to estimate stochastic

risks Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 7 Why so many quantities? 1000 W heater giving hear (IR radiation) - unit is pf power which is related with emission intensity Heat perceived by the person will vary with so many factors: distance, clothing, temperature in room If one has to go a step ahead, from perception of heat to heat absorbed, it becomes a highly complicated issue This is the case with X rays - cant be perceived Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 8 Dose quantities and Radiation units Dose quantities outside the patients body Dose quantities to estimate risks of skin

injuries and effects that have threshold Dose quantities to estimate stochastic risks Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 9 Radiation quantities Used to describe a beam of x-rays: Quantities to express total amount of radiation Quantities to express radiation at a specific point Radiation Protection in Cardiology Total radiation Total photons Integral dose Lecture 2: Talking about radiation dose Radiation at a specific point Photon fluence

Absorbed dose Kerma Dose equivalent 10 Radiation quantities x-ray beam emitted from a small source (point): constantly spreading out as it moves away from the source all photons that pass Area 1 will pass through all areas (Area 4) the total amount of radiation is the same The dose (concentration) of radiation is inversely related to the square of the distance from the source (inverse square law) D2=D1*(d1/d2)2 Radiation Protection in Cardiology Lecture 2: Talking about radiation dose d1=1 Area = 1 Dose = 1 d2=2 Area = 4

Dose = 1/4 11 1 - Dose quantities and radiation units Absorbed dose The absorbed dose D, is the energy absorbed per unit mass D = dE/dm SI unit of D is the gray [Gy] Entrance surface dose includes the scatter from the patient ESD D * 1.4 Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 12 Absorbed dose, D and KERMA The KERMA (kinetic energy released in a material) K = dEtrans/dm

where dEtrans is the sum of the initial kinetic energies of all charged ionizing particles liberated by uncharged ionizing particles in a material of mass dm The SI unit of kerma is the joule per kilogram (J/kg), termed gray (Gy). In diagnostic radiology, Kerma and D are equal. Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 13 Absorbed dose in soft tissue and in air Values of absorbed dose to tissue will vary by a few percent depending on the exact composition of the medium that is taken to represent soft tissue. The following value is usually used for 80 kV and 2.5 mm Al of filtration : Dose in soft tissue = 1.06 x Dose in air Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 14

Example 1: Dose rate at different distances Fixed FOV=17 cm & pt. thickness=24 cm Pulsed fluoro LOW 15pulses/s; 95 kV, 47 mA, FDD = focus-detector distance FSD = focus-skin distance Image Intensifier measured dose rate (air kerma rate) at FSD=70 cm: 18 mGy/min FDD dose rate at d= 50 cm: using inverse square law = 18 * (70/50)2 = 18 * 1.96 = 35.3 mGy/min Radiation Protection in Cardiology Lecture 2: Talking about radiation dose FSD d 16 Example 2: Dose rate change with image quality (mA) Fixed FOV=17 cm & pt. Thickness=24 cm 15 pulse/s, FSD=70 cm, 95 kV 1. pulsed fluoro LOW 47 mA, dose rate = 18 mGy/min FDD = focus-detector distance

FSD = focus-skin distance Image Intensifier Dose rate at the patient skin including backscatter (ESD=Entrance Surface Dose): ESD= 18 * 1.4 = 25.2 mGy/min 2. pulsed fluoro NORMAL 130 mA, dose rate = 52 mGy/min Dose rate at the patient skin including backscatter (ESD=Entrance Surface Dose): ESD= 18 * 1.4 = 73 mGy/min Radiation Protection in Cardiology Lecture 2: Talking about radiation dose FDD FSD d 17 Example 3: Dose rate change with patient thickness Fixed FOV=17 cm; pulsed fluoro= Low, 15 p/s FDD = focus-detector distance FSD = focus-skin distance 1.

Patient thickness 20 cm, Dose rate at the patient skin including backscatter ESD = 10 mGy/min 2. Patient thickness 24 cm, Dose rate at the patient skin including backscatter ESD = 25.2 mGy/min Image Intensifier FDD 3. Patient thickness 28 cm, Dose rate at the patient skin including backscatter ESD = 33.3 mGy/min Radiation Protection in Cardiology Lecture 2: Talking about radiation dose FSD d 18 Example 3: Pt. Thickness (contd.)

120 Dose rate (mGy/min) 100 80 Fluorosocpy: entrance surface dose; FOV 18 cm (Philips Integris 3000); Fluoro low Fluoro Normal Fluoro high 60 40 20 0 16 20 24 PMMA thickenss (cm) 28 Entrance dose rates increase with: image quality selected & patient thickness Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 19 Example 4: Equipment type

Entrance dose rates, FOV=17 cm, PMMA=20 cm 70 60 50 Entrance 40 dose rate 30 (mGy/min) 20 10 0 System A System B Low Normal High Image quality Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 20 Dose measurement (I) Absorbed dose (air kerma) in X ray field can be measured with Ionisation chambers,

Semiconductor dosimeters, Thermoluminescentt dosimeters (TLD) Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 21 Dose measurement (II) Absorbed dose due to scatter radiation in a point occupied by the operator can be measured with a portable ionisation chamber Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 22 1 - Dose area product (I) d1=1 DAP = D x Area Area = 1 Dose = 1

the SI unit of DAP is the Gy.cm2 Radiation Protection in Cardiology Lecture 2: Talking about radiation dose d2=2 Area = 4 Dose = 1/4 23 1 DAP (II) DAP is independent of source distance: D decrease with the inverse square law Area increase with the square distance d1=1 Area = 1 Dose = 1 d2=2 Area = 4 Dose = 1/4 DAP is usually measured at the

level of tube diaphragms Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 24 Example 1 DAP Patient thickness 24 cm, FOV=17 cm, FDD=100 cm, pulsed fluoro LOW 95 kV, 47 mA, 15 pulse/s FDD = focus-detector distance FSD = focus-skin distance Dose in 1 min @ FSD=70 cm: 18 mGy Area @ 70 cm: 11.9*11.9=141.6 cm2 DAP= 18 * 141.6 = 2549 mGycm2 = 2.55 Gycm2 Image Intensifier 17 Dose in 1 min @ FSD=50 cm: 18 * (70/50)2 = 18 * 1.96 = 35.3 mGy Area @ 50 cm: 8.5*8.5=72.2 cm2 DAP= 35.3 * 72.2 = 2549 mGycm2 = 2.55 Gycm2 DAP is independent of focus to dosemeter 11. 9 FDD distance

(without attenuation of x-ray beam) 8.5 FSD Radiation Protection in Cardiology Lecture 2: Talking about radiation dose d=50 25 Example 2: DAP Patient thickness 24 cm, FOV=17 cm, FDD=100 cm pulsed fluoro LOW 95 kV, 47 mA, 15 pulse/s FDD = focus-detector distance FSD = focus-skin distance Dose in 1 min @ FSD=70 cm: 18 mGy Area @ 70 cm: 11.9*11.9=141.6 cm2 DAP= 18 * 141.6 = 2549 mGycm2 = 2.55 Gycm2 Image Intensifier 17 Area @ 70 cm: 15*15=225 cm2 DAP= 18 * 225 = 4050 mGycm2 = 4.50 Gycm2 (+76%) 11. 9

FDD 8.5 If you increase the beam area, DAP will increase proportionately Radiation Protection in Cardiology FSD Lecture 2: Talking about radiation dose d=50 26 Other dose quantities outside the patient body Fluoroscopy time: has a weak correlation with DAP But, in a quality assurance programme it can be adopted as a starting unit for comparison between operators, centres, procedures for the evaluation of protocols optimisation and, to evaluate operator skill DAP vs fluoroscopy time for PTCA procedures DAPfluoro vs fluoroscopy time for CA procedures 70000 25000

60000 15000 y = 535.29x + 2162.7 R2 = 0.4497 10000 DAP (cGycm2) DAP (cGycm2) 20000 50000 40000 30000 20000 y = 711.46x + 2553 R2 = 0.5871 10000 5000 0 0 0 5 10

15 20 25 30 35 0 Fluoroscopy tim e (m in) Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 10 20 30 40 Fluoros copy tim e (m in) 27 50 60

Other dose quantities outside the patient body Number of acquired images and no. of series: Patient dose is a function of total acquired images There is an evidence of large variation in protocols adopted in different centres Coronary Angiography procedures No. frames/procedure No. series/procedure 1200.0 Mean no. series/procedure Mean no. frames/procedure 1600.0 800.0 400.0 0.0 16.0 14.0 12.0

10.0 8.0 6.0 4.0 2.0 0.0 Centre Ce ntre /Study DIMOND trial on CA procedures (2001) Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 28 Reference levels Reference levels: an instrument to help operators to conduct optimised procedures with reference to patient exposure Required by international (IAEA) and national regulations For complex procedures reference levels should include: 3rd level Patient risk more parameters and, must take into account the protection from stochastic and

deterministic risks Level 2 + DAP + Maximum Skin Dose (MSD) 2nd level Clinical protocol 1st level Equipment performance Level 1 + No. images + fluoroscopy time Dose rate and dose/image (BSS, CDRH, AAPM) (Dimond) Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 29 Reference levels DIMOND trial: third-quartile values of single centre data set (100 data/centre) Coronary Angiography procedures PTCA procedures 70 120

60 100 50 80 40 60 30 40 20 20 10 0 0 GR SP IT DAP (Gycm 2) Radiation Protection in Cardiology

IRL FT (m in) FIN ENG Fram e s X100 GR SP DAP (Gycm 2) Lecture 2: Talking about radiation dose IT IRL FIN ENG FT (m in) FR x 100 30 Reference levels in interventional cardiology Procedure: CA PTCA

DAP (Gycm2) 57 94 Fluoroscopy time (min) 6 16 1270 1355 No. of frames DIMOND EU project. E.Neofotistou, et al, Preliminary reference levels in interventional cardiology, J.Eur.Radiol, 2003 Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 31 Dose quantities and Radiation units 1. Dose quantities outside the patients body 2. Dose quantities to estimate risks of skin injuries and effects that have

threshold 3. Dose quantities to estimate stochastic risks Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 32 Interventional procedures: skin dose In some procedures, patient skin doses approach those used in radiotherapy fractions In a complex procedure skin dose is highly variable Maximum local skin dose (MSD) is the maximum dose received by a portion of the exposed skin Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 33 2 Methods for maximum local skin dose (MSD) assessment

On-line methods: Point detectors (ion chamber, diode and Mosfet detectors) Dose to Interventional Radiology Point (IRP) via ion chamber or calculation Dose distribution calculated Correlation MSD vs. DAP Off-line methods Point measurements (thermo luminescent detectors (TLD) Area detectors (radiotherapy portal films, radiochromic films, TLD grid) Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 34 Skin Dose Monitor (SDM) Zinc-Cadmium based sensor Linked to a calibrated digital counter

Position sensor on patient, in the X ray field Real-time readout in mGy Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 35 2 Methods for MSD (cont.): on-line methods (I) Point detectors (ion chamber, diode and Mosfet detectors) Dose to Interventional Radiology Point (IRP) via ion chamber or calculation 15 cm 15 cm IRP IRP Isocenter Radiation Protection in Cardiology Isocenter

Lecture 2: Talking about radiation dose 36 2 Methods for MSD (contd.): on-line methods (II) Dose distribution calculated by the angio unit using all the geometric and radiographic parameters (C-arm angles, collimation, kV, mA, FIID, ) Correlation MSD vs. DAP: Maximum local skin dose has a Maximum local skin dose versus DAPfor PTCA 4.0 3.5 PSD= 0.0141*DAP 3.0 PSD (Gy) weak correlation with DAP For specific procedure and protocol, installation and operators a better correlation can be obtained and MSD/DAP factors can be adopted for an approximate estimation of the MSD

2.5 2.0 1.5 1.0 0.5 0.0 0 50 100 150 200 250 DAP (Gycm2) Example of correlation between ESD and DAP for PTCA procedure in the Udine cardiac centre Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 37 2 Methods for MSD (contd.): off-line (I) Point measurements: thermoluminescent

detectors (TLD) Area detectors: radiotherapy portal films, radiochromic films, TLD grid Large area detectors exposed during the cardiac procedure: between tabletop and back of the patient Radiation Protection in Cardiology Example of dose distribution in a CA procedure shown on a radiochromic film as a grading of color Lecture 2: Talking about radiation dose 38 2 Methods for MSD (contd.): off-line (II) Area detectors: Dose distribution is obtained through a calibration curve of Optical Density vs. absorbed dose Radiotherapy films: require chemical processing maximum dose 0.5-1 Gy Radiochromic detectors: do not require film processing

immediate visualisation of dose distribution dose measurement up to 15 Gy Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 39 2 Methods for MSD: off-line (III) Area detectors: TLD grid Dose distribution is obtained with interpolation of point dose data Diagnostic Top 4 cm 8 cm 40.0-45.0 35.0-40.0 12 cm 30.0-35.0 25.0-30.0 20.0-25.0 15.0-20.0

16 cm 10.0-15.0 5.0-10.0 0.0-5.0 20 cm 24 cm dose (cGy) Pt Left Radiation Protection in Cardiology B C D Lecture 2: Talking about radiation dose E F belt width (cm) G H J

40 28 cm Pt Right 2 Methods for MSD: off-line (III) Area detectors: TLD grid Example of dose distributions Dose distribution for a RF ablation PTCA Dose distribution in a PTCA procedure Top Diagnostic 4 cm Top 400.0-450.0 8 cm 350.0-400.0 300.0-350.0 250.0-300.0 4 cm

12 cm 200.0-250.0 150.0-200.0 8 cm 100.0-150.0 40.0-45.0 16 cm 35.0-40.0 12 cm 30.0-35.0 25.0-30.0 20 cm 20.0-25.0 15.0-20.0 16 cm 10.0-15.0 24 cm 5.0-10.0 0.0-5.0 20 cm dose (cGy) Pt Left B

24 cm dose (cGy) Pt Left B C D E F belt width (cm) Radiation Protection in Cardiology G H J C D E F belt width (cm) G H

J 28 cm Pt Right Lecture 2: Talking about radiation dose 41 28 cm Pt Right 50.0-100.0 0.0-50.0 Exercise 1: Evaluation of MSD A PTCA of a patient of 28 cm thickness, 2000 images acquired, 30 min of fluoroscopy: System A: 2000*0.4 mGy/image=0.8 Gy 30 min * 33 mGy/min=0.99 Total cumulative dose = 1.79 Gy System B: 2000* 0.6 mGy/image=1.2 Gy 30 min* 50 mGy/min= 1.5 Gy Total cumulative dose = 2.7 Gy Cumulative

skin dose is a function of system performance or image quality selected Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 42 Exercise 2: Evaluation of MSD An crude estimation of MSD during the procedure can be made from the correlation between MSD and DAP in PTCA procedure: Example: A PTCA with DAP= 125 Gycm2 Maximum local skin dose versus DAPfor PTCA 4.0 MSD= 0.0141*DAP = = 0.0141*125= 1.8 Gy 3.5 PSD= 0.0141*DAP (with linear regression factor characteristic of the installation, procedure and operator) PSD (Gy) 3.0 2.5 2.0

1.5 1.0 0.5 0.0 0 50 100 150 200 DAP (Gycm2) Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 43 250 Dose quantities and Radiation units 1. Dose quantities outside the patients body 2. Dose quantities to estimate risks of skin injuries and effects that have threshold 3. Dose quantities to estimate stochastic risks

Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 44 3 - Dose quantities for stochastic risk Detriment Radiation exposure of the different organs and tissues in the body results in different probabilities of harm and different severity The combination of probability and severity of harm is called detriment. In young patients, organ doses may significantly increase the risk of radiationinduced cancer in later life Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 45 3 - Dose quantities for stochastic risk Equivalent dose (H) The equivalent dose H is the absorbed dose multiplied by a dimensionless radiation weighting factor, wR which expresses the biological effectiveness of a given type of radiation

H = D * wR the SI unit of H is the Sievert [Sv] For X-rays is wR=1 For x-rays Radiation Protection in Cardiology H = D !! Lecture 2: Talking about radiation dose 46 3 - Dose quantities for stochastic risk Mean equivalent dose in a tissue or organ The mean equivalent dose in a tissue or organ HT is the energy deposited in the organ divided by the mass of that organ. Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 47 Tissue weighting factor To reflect the

detriment from stochastic effects due to the equivalent doses in the different organs and tissues of the body, the equivalent dose is multiplied by a tissue weighting factor, wT, Radiation Protection in Cardiology ORGAN / TISSUE WT ORGAN / TISSUE WT Bone marrow 0.12 Lung 0.12 Bladder 0.05

Oesophagus 0.05 Bone surface 0.01 Skin 0.01 Breast 0.05 Stomach 0.12 Colon 0.12 Thyroid 0.05 Gonads 0.20 Remainder

0.05 Liver 0.05 Lecture 2: Talking about radiation dose 48 3 - Dose quantities for stochastic risk Stochastic risk Stochastic risk (death from exposure) is calculated multiplying effective dose E by the risk factor specific for sex and age at exposure 0.20 f= 0.16 de ath pe r Sie v e rt 0.12 (Sv ) Female Male 0.08 0.04 0.00 0

Stochastic Risk = E(Sv) * f Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 15 30 45 60 Age at Exposure 49 75 90 3 - Dose quantities for stochastic risk Effective dose, E The equivalent doses to organs and tissues weighted by the relative wT are summed over the whole body to give the effective dose E E = T wT.HT wT : weighting factor for organ or tissue T HT : equivalent dose in organ or tissue T Radiation Protection in Cardiology

Lecture 2: Talking about radiation dose 50 Effective dose assessment in cardiac procedures 1. 2. Organ doses and E can be calculated using FDA conversion factors (FDA 95-8289; Rosenstein) when the dose contribution from each x-ray beam used in a procedure is known Complutense University (Madrid) computer code allows to calculate in a simple manner organ doses and E (Rosenstein factors used) Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 51 Example 1 Effective dose (mSv) 0 2 4 6

8 Computed Tomography Head Torax Effective dose quantity allows to compare different type of radiation exposures: Different diagnostic examination Abdomen Liver Kidney Lumbar spine Fluorographic examinations Barium enema Barium meal IVU Radiographic examinationa Lumbar spine Abdomen Pelvis Torax Head Spine (full) Annual exposure to natural

background radiation Radiation Protection in Cardiology Interventional Radiology Diagnostic Therapeutic Annual natural dose Lecture 2: Talking about radiation dose 52 10 Example 2: Effective dose assessment in cardiac procedures For a simple evaluation, E can be assessed from total DAP using a conversion factor from 0.17-0.23 mSv/Gycm2 (evaluated from NRPB conversion factors for heart PA, RAO and LAO projections) Example: CA to a 50 y old person performed with a DAP=50 Gycm2 Effective dose E = 50 * 0.2 = 10 mSv Stocastic risk: R=0.01 Sv *0.05 deaths/Sv = 0.0005 (5/10000 procedures) Compare with other sources:

Udine cardia center: CA: mean DAP=30 Gycm2 E = 6 mSv PTCA:mean DAP=70 Gycm2 E = 14 mSv MS-CT of coronaries E 10 mSv Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 53 Staff Exposure Staff dosimetry methods Typical staff doses Influence of technical parameters Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 54 Many variables affect level of staff exposure Isodose map around an angiographic unit type of equipment and equipment performance distance from the patient beam direction use of protective

screens type of procedure and technique operator skill training Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 55 Staff doses per procedure High variability of staff dose/cardiac procedure as reported by different authors Correct staff dosimetry and proper use of personal dosimeters are essential to identify poor radiation protection working conditions Wu et al., 1991 Renaud, 1992 Li et al., 1995 Steffenino et al., 1996 Folkerts et al., 1997 Watson et al., 1997 Zorzetto et al., 1997 Va et al., 1998 Padovani et al., 1998 DIMOND 1999 Spain DIMOND 1999 Italy DIMOND 1999 Greece 20 Effective dose/procedure (uSv/proc)

15 Radiation Protection in Cardiology 10 5 0 Lecture 2: Talking about radiation dose 56 Staff dosimetry methods Exposure is not uniform: with relatively high doses to the head, neck and extremities much lower in the regions protected by shieldings Dose limits (regulatory) are set in terms of effective dose (E): no need for limits on specific tissues with the exception of eye lens, skin, hands and feet The use of 1 or 2 dosemeters may provide enough information to estimate E

Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 57 Personal dosimetry methods Single dosimeter worn above the apron at neck level (recommended) or under the apron at waist level Radiation Lens dose, optional protection measures Finger dose, optional Second dosemeter Image intensifier Two dosimeters worn (recommended) one above the apron at neck level another under the lead apron at waist level

Patient outside and above the apron at the neck, optional Personal dose dosemeter behind the lead apron Dose limits of occupational exposure (ICRP 60) Effective dose 20 mSv in a year averaged over a period of 5 years X-ray tube Anual equivalent dose in the lens of the eye 150 mSv skin 500 mSv hands and feet 500 mSv Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 58

Staff dosimetry methods (comments) Assessment of E is particularly problematic due to the conditions of partial body exposure Use of dosimeter worn outside and above protective aprons results in significant overestimates of E. On the other hand the monitor under the protective apron significantly underestimates the effective dose in tissues outside the apron. Multiple monitors (more than 2) are too costly and impratical. Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 59 Protective devices influence Protective devices: Radiation Lead screens: suspended, curtain Leaded glasses Lead apron Collar protection,

influence radiation field. Lens dose,optional protection measures Finger dose,optional Second dosemeter Image intensifier Patient at the neck, optional Personal dose dosemeter behind the lead apron Dose limits Only proper use of personal dosimeter allows to measure individual doses of occupational exposure (ICRP 60) Effective dose 20 mSv in a year averaged over a period of 5 years X-ray tube Radiation Protection in Cardiology

outside and above the apron Lecture 2: Talking about radiation dose Anual equivalent dose in the lens of the eye150 mSv skin 500 mSv hands 60 and feet500 mSv Exercise 1: annual staff exposure Operator 1: 1000 procedures/year 20 Sv/proc E= 0.02*1000 = 20 mSv/year = annual effective dose limit Operator 2: 1000 proc/year 2 Sv/proc E= 0.002*1000=2 mSv/year = 1/10 annual limit Wu et al., 1991 Renaud, 1992 Li et al., 1995 Steffenino et al., 1996 Folkerts et al., 1997

Watson et al., 1997 Zorzetto et al., 1997 Va et al., 1998 Padovani et al., 1998 DIMOND 1999 Spain DIMOND 1999 Italy DIMOND 1999 Greece Radiation Protection in Cardiology Effective dose/procedure (uSv/proc) 20 15 10 5 0 Lecture 2: Talking about radiation dose 61 Re-cap Different dose quantities are able: to help practitioners to optimise patient exposure to evaluate stochastic and deterministic risks of radiation Reference levels in interventional

radiology can help to optimise procedure Staff exposure can be well monitored if proper and correct use of dosimeters are routinely applied Radiation Protection in Cardiology Lecture 2: Talking about radiation dose 62

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