Using X-Rays Safely (Part 1) - PDF

**[Using X-Rays Safely] [DOSE and Dosimetry ]** **[Discovery of X-rays:]** **[November 1985]:** Wilhelm Röntgen discovered **X-Rays** and *[won]* the *[first]* **Nobel** **Prize** in **1901** **: Henri Becquerel** *[discovered]* **radioactivity**\* (Marie Curie coined term radioactivity) *[from w...

**[Using X-Rays Safely] [DOSE and Dosimetry ]** **[Discovery of X-rays:]** **[November 1985]:** Wilhelm Röntgen discovered **X-Rays** and *[won]* the *[first]* **Nobel** **Prize** in **1901** **: Henri Becquerel** *[discovered]* **radioactivity**\* (Marie Curie coined term radioactivity) *[from what he]* *[thought]* was a **Failed Experiment**. Nobel prize winners 1903 **[December 1895:]** *[First]* **Dental X-Ray --** Dr Otto Walkhoff/Fritz Giesel - 30 minute exposure - *[Very]* **painful** - **Fritz** *[held the]* **Tube** *[whilst]* *[otto]* had **Film** *[inside]* of the **mouth** - **Fritz** died from a **metastatic carcinoma** in the **Hands** **[INTRODUCTION TO X-RAYS:]** In the UK, **Dental Radiography** *[accounts]* for **26%** of all *[diagnostic]* **medical X-ray** *[examinations]* in the **UK^1^** (intra-orals, OPGs, lateral cephs, CBCT) *[Globally]*, this is **1.5 billion** and *[around]* **15%** of *[all]* **DIAGNOSTIC X-RAYS** **[UK LEGAL REQUIREMENTS:]** The **Ionising** **Radiation** **Regulations** **2017** **(IRR17)** - **Radiation** **Protection** for *[workers]* and *[members]* of the **public** (Dentists, Pilots, Nuclear Workers Etc) The **Ionising Radiation (Medical Exposure) Regulations 2017 (IR(ME)R17)** - Radiation **Protection** for **Patients** -- Specifically those people **Optimizes** **Dosage** -- **Quality** **Assurance** **[Radiation Definition: The Emission of Energy]** - For *[example]*, the **Radiators** at home emit heat - The term **radiation** *[gets tied up]* with **Ionising Radiation**, but *[we need to distinguish]* *[between]* **Harmful** and **Non-Harmful Radiation** **[BENEFICIAL EFFECTS OF IONISATION EVENTS]** **Vitamin D Activation** (UV) **Prevention of** **Rickets**, **Osteomalacia** **Differential Absorption** (X Rays) **Image Production** **Blocks Neoplastic Cell division** (Gamma) **Radiotherapy** **[WHAT IS RADIATION?]** - **Radiation** is the *[emission]* of **Energy** - Think about "**Radiators**" at home - **Radiation** is *[very]* *[commonly]* *[tied]* up with **Ionising Radiation** - *[But it is important to distinguish]* *what* **Radiation** is **Harmful** - *[Most]* *[commonly]* this is **Electro-Magnetic Radiation** (waves/light/photons) - *[Also applies to]* **Particulate Radiation** - **Radiation** is *[separated]* into **two brackets** - **Ionising** - **Non ionising** **[INDIRECT DAMAGE --] Affects** *other* **Molecules** that *causes* **Damage** 1. **RADIATION \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- H2O \-\-\-\-\-\-- H2O+ + e-** 2. **H2O+ \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- H+ + OH** 3. **H2O + e- \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- H2O-** 4. **H2O- \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- H + OH** **H** and **OH** are the **FREE RADICALS** *[which combine to form]* **Toxic Oxidizing Agents**: - **HYDROGEN PEROXIDE H2O2** - **HYDROPEROXYL RADICAL** **HO2 +** **[MOLECULAR LEVEL: CELL IONISATION:]** *[Structural changes]* to **DNA** e.g. **Point Mutations** or **Clusters DS** **Radiation** *[directly]* *[interacts]* with the **DNA (direct)** - **Direct Damage** *[changing]* **DNA Structure** - *[Different]* **Radiation** *[types]* **Ionise Differently** - **Particles** *[deliver]* **More Damage** **Radiation** **Ionises** *[something else]* (indirect) - **Free electrons** *[get chemically]* "**mopped**" up - *[Generates]* **Free Radicals** which *[make]* **Chemical Changes** to **DNA** - *[A lot more common than direct]* - **Radiation** *[will]* **Ionise Something**, *[likely]* to be **Water** in **Cell** - *[Creates]* a **Free Radiations** - *[Will allow a]* **Chemical Reaction** with **DNA** **[TISSUE RESPONSES:]** **X-rays** *[causing]* **Tissue Ionisation** and *[there are three possible outcomes:]* - **Cell** **repair** - **Fatal Damage** (*tissue reaction*) - **Non-fatal damage**, - **DNA** **change** (*cancer, heritable effects*) **[*ADVERSE* HEALTH EFFECTS OF RADIATION EXPOSURE]** **[2 Types ]** **[SOMATIC EFFECT:]** **Somatic** **effects** *[occur]* in the **body** of the **Irradiated Individual** **[GENETIC EFFECTS ]** *[Occur]* in the **bodies** of the **offspring** of the **Irradiated Individual**, due to *[effects]* on the **Gonadal Tissues**. **[STOCHASTIC EFFECTS]** *[happen]* by '**chance'** or *[effects with a probability]* of **happening** **'Tissue Reactions'** *[formally]* known as '**Deterministic Effects'** *[are known to happen above a]* **THRESHOLD DOSE** **TISSUE REACTIONS: - pretty much inevitable** *[Effects]* are *[known]* to *[happen]* above a **Threshold Dose** *[Cause]* is *[largely]* due to **Cell Death** and *[impairment]* of **function** *[Different for each type]* of **Reaction**, and *[once]* *[exceeded]* **Severity Increases** **[TISSUE REACTIONS & RADIOSENSITIVITY]** - *[Most]* **Organs** *[can function]* with the *[loss]* of a **Moderate** **Number** of **cells** - **Continuously Proliferating Cells** e.g. **Bone Marrow** ***[very]* *[sensitive]*** - *[These occur above a]* **Threshold** **Dose** -- **Burns** , **Hair Loss** and **Radiation Sickness** **[DOSE]** **[WHOLE BODY EFFECT]** ------------------------ ----------------------------------------------------------------------------------------------------- **0.25 Sv** **Slight blood changes, e.g., decrease in WBC count** **1 - 2 Sv** **Vomiting in 3 hours, fatigue, loss of appetite, blood changes, recovery in a few weeks** **2 - 6 Sv** **Vomiting in 2 hours, severe blood changes, loss of hair within 2 weeks, recovery in a few weeks** **6 - 10 Sv** **Vomiting in 1 hour, intestinal damage, severe blood changes, death in 2 weeks for 80-100%** **\> 10 Sv** **Brain damage, coma, death** [ **VERY HIGH THRESHOLD DOSES**] - *[Not expected]* in **Diagnostic Imaging** - **0.1-2 Gy** - *[This could occur]* with an **Accident** -- *[not with]* **Diagnostic Imaging** [**CATARACT** *formation* *in* **EYE**] **Cataracts** *[were]* **5 Gy** *[but recently]* **lowered**! *[Has the]* **Lowest Threshold** "...*[recent]* *[evidence]* has *[indicated]* a **Threshold** of about **500 mSv**, a *[factor]* of **3** *[lower]* *[than previously thought"\*]* **[TISSUE REACTIONS]** - **Erythema** of the **Skin** - **Hair** **Loss** - ***[Reduction]*** in **Bone Marrow** **Cell Production** - **Cataract** *[formation]* in **EYE** - "**Radiation** **Sickness**" **Very high** **Threshold Doses** *[Due in large]* *[part]* to the **Killing/ Malfunction** of **Cells** *[following]* **High Doses** **[STOCHASTIC EFFECTS 'CHANCE':]** *[Additional]* **risk** (chance) of **Cancer Development** in *[exposed]* **individuals** *[owing]* to **Mutation** of **Somatic Cells** **Heritable** **Disease** in *[offspring]* *[owing]* to **Mutation** of **Reproductive "Germ" Cells** - **GENETIC EFFECTS** *[As you]* **Increase** in **Dose**, you *[increase]* the **Risk** *[Above]* **100 mSv**: **WELL-VERIFIED EFFECTS** *[Above]* **50 mSv**: *[somewhat]* **Verified** *[We believe]* in **Linear No Threshold Dose:** if you have **Radiation** **Exposure**, *[you have]* **Increased Yourself** to **Risk** (proportional) **I**nternational **C**ommission **O**n **R**adiological **P**rotection **No Threshold** dose (**no "safe" dose**) *[Chance]* of **Effect** **Increases** *[with the]* **Dose** of **Radiation** received **NO RECOVERY PROCESSES** *[There are]* **Different** **Models**: - **Blue lines**: low levels of radiation are good for you - **Higher** Risk model - **Lower** Risk model **NO** threshold dose -- no 'safe' dose **Risk** of **Secondary Cancer** *[increases]* with the **Radiation Dose** *[received]* [**Risk** from **Dental Radiography**] [*Increased* **Risk** *from* **CONE BEAM** CT In **DENTISTRY**] **IRR17: change dose limit to lens of the eye for staff** **500 mSv** **20 mSv** *[per year]* As you are younger, your lifetime cancer risk is higher than if you are older As you have more life to live when you are younger Age less than 10, risk factor is x3 -- reduces with age **[WHAT DO WE MEAN BY "DOSE" OF RADIATION?]** **Energy** *[Absorbed]* **Per Unit Mass** **Joule. kg-1** *[Transfer]* of **energy** from **Radiation** to **Atoms** 1 joule. kg-1 = 1 **Gray** (**Gy**) Absorbed dose *[But\...different types]* of **Radiation** *[have different]* **DAMAGING POTENTIAL** for the **same dose** *[Performed]* by **Medical Physics** **Experts -- Measured** *[with]* **IONIZING CHAMBER and Dose Area Product (DAP)** *[Measures]* **absorbed dose** in **mGy (milliGray), mGy.cm/ mGy.mm (dose-width-product) or mGy.cm2 (dose-areaproduct)** **Equivalent dose (D~r~) (Sievert)** = **absorbed** **dose** **(D)** x **RADIATION WEIGHTING FACTOR (W~R~**) **[𝐷~𝑟~ = 𝐷 × 𝑊~𝑟~]** *[Note]* the **EQUIVALENT DOSE (SV)** *[has the same units]* as **Gy, J/Kg** **Equivalent** **Dose** *[has a different unit]* (**Sievert**) *[Different]* **Tissues** *[have different]* **Radio Sensitivities** **1 mGy Absorbed Dose** of **Alpha Particles** in the **Lungs** = **Equivalent dose of 20 mSv** to the **Lungs** **[EFFECTIVE DOSE:]** *[Different]* **Organ Tissue Types** *[react]* *[differently]* to **Radiation** **Exposure** (radiosensitivity) I.e., *[some]* **Organs** in the **BODY** are *[more likely to develop]* cancer after **Radiation Exposure** For **Example**, **Highly Proliferating Organs** *[are more sensitive]* to **Radiation.** **Effective Dose (H~t~)** *[allows all]* **Radiation** **Risk** to be **Compared** and **Considers** **TISSUE WEIGHTING FACTORS (W~T)~** **Effective Dose** = sum of... - **Equivalent Dose** (organ 1) x **Tissue Weighting** (organ 1) + - **Equivalent Dose** (organ 2) x **Tissue Weighting** (organ 2) + *[Where]* **Dt,R** = *[average]* **Absorbed Dose** in *[volume]* of **Specific Organ** or **tissue R** of **Radiation Type** **Effective** **Dose** is *[measured]* in **SIEVERTS** *[Total of all organs]* = 1 **[Effective dose: STOCHASTIC EFFECTS]** *[Probability]* **co-efficient** for *[additional]* **Cancer Risk:** *[Additional]* *[chance]* of **Developing Cancer** *[Sweeping]* **Population** **Statement**: **Age** and **Sex** and *[where]* **Irradiated** will *[change]* the **%** **Probability** **Coefficient** for **Cancer Risk** is **5.5 x 10−2 Sv−1 (5.5% per Sv)** **[CBCT EFFECTIVE DOSE:]**  [**Radiation** **Doses** *from* **DENTAL RADIOLOGY RADIATION DOSES** *from* **Dental Radiology**] *[Using]* **Modern Equipment** in a *[proper way will usually mean]* **Doses** at the *[lower]* **end** of the **ranges** **[RADIOGRAPHIC TECHNIQUE]** **[EFFECTIVE DOSE (µSV)]** ------------------------------------------------ ---------------------------------------- **Intraoral Radiograph (bitewing/periapical)** **0.3 -- 21.6 µSv** **Panoramic radiograph** **2.7 -- 24.3 µSv** **Lateral Cephalometric Radiograph** **2.2 -- 6.3 µSv** **CBCT (Small Field Of View)** **11 -- 214 µSv** **CBCT (Medium Field Of View)** **18 -- 674 µSv** **CBCT (Large Field Of View)** **60 -- 510.6 µSv** **CBCT (Extended Field Of View)** **30 -- 1025 µSv** **CT Scan** **250 -- 1410 µSv** **CT Scan (mandible and maxilla)** **430 -- 860 µSv** **[MEASURING EFFECTIVE DOSE:]** **Dosimetry Phantoms** *[Can use a]* **Phantom** *[which]* has **Tiny Holes** in it *[Place]* **TLD's** in the **holes** and *[measure]*/*[quantify]* the **Radiation** **Lithium Fluoride Thermoluminescent Dosemeters** **[EFFECTIVE DOSE IN CONTEXT]** - Cosmic 320 µSv / year - Terrestrial Gamma Radiation (uranium, thorium, 40 K) 350 µSv / year - Internal Radiation (40 K, 14 C) 270 µSv / year - Radon and its decay products 1200 µSv / year - Man-made radiation - About 300 µSv / year **[RADIATION DOSES FROM DENTAL RADIOLOGY:]** *[This is just a]* **Vague Generalisation** *[Good]* to *[explain]* to **Patients**  **Dose** *[represents]* **ideal practice** *[Ideal]* **Practice** is *[far from]* **Universal** **Practice** is *[never peak]* -- **hence** *[why we need to]* **Optimise** **[IDEAL PRACTICE: OPTIMISATION]** **[OPTIMISATION]:** - *[Check]* on **Radiation** **Safety** [*once every* **Three Years** ] - *[Measurement]* of **Dose** *[required]* - By **RPA / MPE** *[visit]* or *[using]* **postal pack** (Public Health England method *"The* [likelihood] *of* [incurring] ***exposure**, the number of **people** **exposed**, and the **magnitude** of their **individual doses** should all be kept **as low as reasonably achievable, taking into account economic and societal factors"*** **ALARA** -- As Low As Reasonably Achievable **ALARP** -- As Low As Reasonably Practicable **[ALARP vs ALARA:]** **ALARA** *[does not account]* for **money** i.e., *[we should change]* **X-Ray Unit** *[every]* month is *[there]* is a **better option** *[available]* **ALARP** *[allows you to bring]* **Cost**-**Risk** *[into]* *[account]* **[DOSE OPTIMISATION:]** - *[Machine]* - *[Imager]* - *[Protecting Patient ]* **[OPTIMISATION: EXPOSURE]** **Exposure Factors**: - **kV** - **mA** (current) - Time *[Use]* **Appropriate Protocols:** - **Intra-Oral** 50-70 kV - *[There are set]* **procols** for *[each]* **TOOTH**, *[ensure]* it is **Correct** - **Panoramic/CBCT** \