Fifty shades of Gy: Radiation in Interventional ...

Fifty shades of Gy: Radiation in Interventional Cardiology Marjan Boshev University Clinic of Cardiology Skopje, Macedonia May 2016

Rising Awareness – Understanding the Impact

Х- rays - Ionizing Radiation

Radiation dose units Dose type

Classic units Unit

SI units Abrr

Unit

Abrr

Exposure (Air Kerma) Roentgen – for X-rays or γ-rays only

R

Coulomb per kilogram

C/kg

Absorption (Energy

Radiation absorbed dose

Rad

Grey

Gy (=100 Rad)

Rem

Sievert

caused by any radiation in a living organism)

Roentgen equivalent mammal

*Sv (=100 Rem)

Radioactivity (from

Curie

Ci

Becquerel

Bq

deposited by any type of radiation in any material)

Equivalent (Biologic effect

radioactive sources – α, β)

*1 mSv = 50 CXR

Schematic view of C-arm

Types of X-rays in cath lab 1. Primary radiation (radiation that exits from the tube), 2. Absorbed radiation (photoelectric absorption by the patient), 3. Scattered radiation (primary, secondary), 4. Transmitted radiation (exits the patient without interaction), 5. Remnant radiation (X-rays that hit the film/detector --- useful), 6. Leakage radiation (from the primary source)

Radiation exposure of interventional cardiologists Three (3) sources of radiation („stray radiation“):

- Tube housing leakage (minor, unless defects present), - Primary scatter from the patient and table – by far the major source of exposure to the interventionist, - Secondary scatter from other objects in the room (minor, not requiring shielding)

Adverse effects of ionizing radiation

-Dose-dependent; eg. erythema, tissue fibrosis, cataracts, -There is a threshold

-Effect is not dose-dependent, -Occurrence probability increases with increasing of the radiation dose, eg. cancer -There is not a threshold

Adverse Health Effects of Sustained Low-Level Radiation Exposure • Eye diseases – posterior subcapsular lens opacity changes and cataracts • Thyroid diseases – benign and malignant thyroid tumors • Cardiovascular diseases – accelerated atherosclerosis • Reproductive Health Effects – lower fertility, spontaneous abortion • Brain diseases – Brain tumors

Updated data: Oct 10, 2015 • Brain and Neck Tumors – 41 physicians & 1 nurse working with ionizing radiation in catheterization laboratories

What radiation dose does interventional cardiologist receive as a result of professional (occupational) exposition to radiation? The annual dose of radiation in high volume cath labs ~ 5 mSv* (Literature reports: 0,1-30 μSv effective dose per IC procedure (avg. 10 μSv per procedure) Avg. workload ~ 500/year………….500 x 10 μSv = 5 mSv) The cumulative dose after 20 years of professional life ~ 100 mSv

* Picano E, Vano E, Domenici L, Bottai M, Thierry-Chef I. Cancer and non-cancer brain and eye effects of chronic low dose ionizing radiation exposure. BMC Cancer 2012; 12:157.

Limiting the radiation exposition “what is good for the patient is also good for the staff” Four (4) basic methods: 1. Time, 2. Intensity, 3. Distance, 4. Shielding …… TIDS

Factor “time” • Limited to necessary minimum • Screen usually displays the fluoroscopy time (FT), but not fluorography (cine angio) • Fluoroscopy – – 95% from the total X-ray operative time, – only 30-40% of the total radiation exposure of the staff and patients , • Fluorography – – only 5% from the total Х-ray operative time, – almost 60-70% from the total radiation exposure of the staff and patients • Fluorography – 10х higher radiation dose than fluoroscopy • Complex procedures – CTO, bifurcation, multivessel – require longer procedural time → increase radiation dose • “Foot on pedal – eyes on screen” (“heavy foot syndrome”)

Factor “intensity” Minimization of radiation intensity: 1. Optimal setting of the technical parameters of the tube: current intensity (1622 mA) and voltage (60120 kV) 2. Reduction of “pulse rate”/“frame rate” of the tube (in a way that will not affect picture quality)

Factor “distance” • Distance from the source should be as far as possible • Step back: For every doubling of the distance from the source (2x), radiation intensity reduces for 4 times (“inverse square law”)

Factor “shielding” • Significantly reduces staff radiation exposure • Shields – Structural, – Mobile, – Personal

Radiation protection in interventional cardiology

Additional factors that influence radiation exposition • Patient weight • Operator (inter-operator variability) • Image intensifier and tube position (SID-Sourceto-image distance) • Working projections • Image Amplification • Collimation • Arterial Access Site





Additional factors that influence radiation exposition • Patient weight • Operator (inter-operator variability) • Image intensifier and tube position (SID-Sourceto-image distance) • Working projections • Image Amplification • Collimation -FPD 9″: FOV 4,5/6/7,5/9 inch -Radiation dose increases with • Arterial Access Site increasing image amplification/magnification


Additional factors that influence radiation exposition • Patient weight • Operator (inter-operator variability) • Image intensifier and tube position (SID-Sourceto-image distance) • Working projections • Image Amplification • Collimation • Arterial Access Site (Radial vs Femoral)

Optimization in Radiation Protection (ALARA)

Radiation Exposure Monitoring • Regulatory and Surveillance Bodies – The International Commission on Radiological Protection (ICRP) – The International Atomic Energy Agency (IAEA) – Organization for Occupational Radiation Safety in Interventional Fluoroscopy (ORSIF)

• Radiation Exposure Monitoring – Personal Dosimeters (TLD)

• ICRP occupational dose limits recommendation: – EU: • 20 mSv/year (5 y) • max 50 mSv/year (one y)

– Germany: 400 mSv (lifetime dose limit) – US: • 50 mSv in any one year • 10 mSv X Age (years) – lifetime limit

• Monthly Dosimeter Replacement • Wearing of 2 dosimeters (under the apron & above the apron at collar level)

Future in radiation protection Robotic-Аssisted PCI

ZERO Gravity Protection System