Patient Interactions.

Patient Interactions

Patient Interactions Review Tube Interaction Patient Interactions
Heat Brems Characteristic Patient Interactions Classic Coherent Compton Photoelectric Pair Production Photodisintegration Why These are Important? Image Production Patient/Tech Safety

Patient Interactions Review of Tube Interactions: Heat Brems
Characteristic

Characteristic

Interaction in the body begin
Patient Interactions Interaction in the body begin at the atomic level Atoms Molecules Cells Tissues Organs

Patient Interactions Interactions of X-rays with matter
No interaction: X-ray passes completely and get to image receptor Complete absorption: no x-rays get to image receptor Partial absorption with scatter-some x-rays get to image receptor but some get scattered No interaction; X-ray passes completely through tissue and into the image recording device. Complete absorption; X-ray energy is completely absorbed by the tissue. No imaging information results. Partial absorption with scatter; Scattering involves a partial transfer of energy to tissue, with the resulting scattered X-ray having less energy and a different trajectory. Scattered radiation tends to degrade image quality and is the primary source of radiation exposure to operator and staff.

What happens to our Primary Beam?
Patient Interactions What happens to our Primary Beam?

EM Interactions with Matter
Patient Interactions EM Interactions with Matter General interactions with matter include: Scatter With or without partial absorption Absorption Full attenuation

X-ray photons can change cells
Patient Interactions X-ray photons can change cells If the photon hits the nucleus it can kill the cell. The nucleus carries DNA.

Some radiations are energetic enough to rearrange atoms in materials through which they pass, and can therefore he hazardous to living tissue. 1913

Some radiations are energetic enough to rearrange atoms in materials through which they pass, and can therefore he hazardous to living tissue. Hiroshima victim

Patient Interactions I don’t want that to happen to me!!

Patient Interactions Classical Compton Photoelectric Pair Production
Photodisintegration

Patient Interactions Classical (Coherent)

Classical (Coherent) Scattering
Patient Interactions Classical (Coherent) Scattering Excitation of the total complement of atomic electrons occurs as a result of interaction with the incident photon No ionization takes place Electrons in shells “vibrate” Small heat is released The photon is scattered in different directions Energies below 10kV WE can tell the difference between the heat and coherent because it is a photon incoming and exiting. The incoming photon comes in with a energy and changes direction leaving with the same amount of energy. Not useful in diagnostic radiology. Sometimes causes fog on the film. At a higher kVp a few of the classic coherent can add fog to the film.

Patient Interactions Classical (Coherent) Classical scattering

Net Result of Classical
Patient Interactions Classical (Coherent) Net Result of Classical No energy transfer Photon changes direction with same energy Occurs with LOW ENERGY photons No ionization Not diagnostic

Compton scattering COMPTON SCATTERING Outer shell electron in body
Patient Interactions Compton scattering COMPTON SCATTERING Outer shell electron in body Interacts with x-ray photon from the tube 3. Moderate energy electron Outer shell rather than inner shell electron .

Compton scattering Patient Interactions
Recoil electron can produce another interaction if high enough energy. Compton scattering does not provide any useful diagnostic information. Scatter provides no useful information. It adds unifrom density or fog to the film.

Patient Interactions Compton scattering compton scattering (effect)

Compton scattering Patient Interactions
Moderate energy x-ray photon ejects an outer shell electron. Energy is divided between scattered photon and the Compton electron (ejected e- or recoil electron) Scattered photon has sufficient energy to exit body. Since the scattered photon exits the body, it does not pose a radiation hazard to the patient. Can increase film fog (reduces contrast) Radiation hazard to personnel

Photoelectric effect Patient Interactions photoelectron
Incoming photon interacts with inner shell electron. The “knocked-out” electron is called a photoelectron. The energy of the incoming photon is absorbed.

Patient Interactions Photoelectric effect photoelectric interaction

Photoelectric effect Patient Interactions CASCADE
Sine wave coming into the body. CASCADE

Photoelectric effect Patient Interactions
Moderate energy x-ray photon ejects inner shell electron (energy absorbed) Leaves an orbital vacancy, releasing a photoelectron. (As vacancy is filled, another photon is produced-scatter radiation ) More likely to occur in absorbers of high atomic number (bone, positive contrast media) Contributes significantly to patient dose, As all the photon energy is absorbed by the patient , this is responsible for the production of short-scale contrast.

Patient Interactions Pair production Electron (Negatron) positron

Pair Production Patient Interactions
Very high energy…not used in diagnostic radiology. It has enough energy to hit the nucleus and break off two parts of the nucleus: 1 positron and a negatron. This is bad because the nucleus contains DNA. But it is good for cancer, because it kills the cell. Incoming photon must possess a minimum of 1.02 mEv. (million electron volts). Interacts with nuclear electric field and causes it to dissapear. In its place we get two elecgtrons : one positron and one negatron. Electron eventaully will filla vacancy. Positron unites with a free e- and the mass of the both particles is converted to energy ina process called annihnilation radiation. We don’t use this in diagnostic radiology.

Pair Production Very High Energy Photon…..MkV
Not used in Diagnostic X-ray

Patient Interactions photodisintegration Nuclear fragment

Patient Interactions Photodisintegration

Photodisintegration Very High Energy Photon…..MkV
Not used in Diagnostic X-ray

Summary of Interactions
Patient Interactions Summary of Interactions Classical Coherent Low energy photons No diagnostic effect Contributes to scatter Compton Effect (Scattering) Moderate energy photons Contributes to scattering Contributes to personnel dose Photoelectric Effect Definite diagnostic effect Contributes to image contrast Atomic number dependent Contributes to patient dose Pair Production High energy photons Not useful in diagnostic range Photodisintegration

What kind of interaction is this?

ssss Compton

ssssssssssssssssssss

Things to Remember About X-ray Interactions with Matter
Interactions with matter occur in biologic tissue Two interactions with matter important in diagnostic radiology: photoelectric & Compton Incoming photon or x-ray Interacts with: inner shell electron = photoelectric effect outer shell electron = Compton effect

Things to Remember About Diagnostic Radiation Production
Results in: ion and x-ray w/specific (discrete) energy = Characteristic scattered e- and x-ray w/varying (continuous) energy = Bremsstrahlung

Summary of Interactions

Image production Compton Effect Photoelectric Effect
Why Interactions are Important? Image production Compton Effect Biggest Contributor to Scatter Radiation, especially to tech No useful diagnostic information Photoelectric Effect Responds to atomic number, especially at lower kV ranges Biggest contributor to image contrast

Biggest Contributor to Personnel Hazard

During Fluoro – the patient is the largest scattering object
SO this is why we are behind the lead or the doctor. It is an exposure hazard in radiography and fluoroscopy . Large amount of scatter is produced by the patient in fluoroscopy. This exposure is the source of most of the occupational radiation exposure that radiologic technologists receive. During radiography if the radiologic technologist stays in the room they will need to shield themselves.

Both Compton and Classical cause scatter radiation.
Image Production Both Compton and Classical cause scatter radiation. Why is one of these a concern to diagnostic radiography and one is not? Why is one a concern to patient safety and one is not? Why is one a concern to technologist safety and one is not?

Image Production and Patient Safety
Photoelectric absorption is what gives us our image contrast. Photoelectric absorption is determined mostly by atomic number. The lower the kV of the photons, the more it is affected by atomic number. The higher the kV, the less atomic number factors into photon absorptions. However, patient dose increases with photoelectric absorptions because the energy of the photon is deposited in the tissue. This affects patient dose.

Differential Absorption
Image Production Differential Absorption Results from the differences between x-rays being absorbed and those transmitted to the image receptor Compton Scattering Photoelectric Effect X-rays transmitted with no interaction

Compton and Differential Absorption
Image Production Compton and Differential Absorption Provides no useful info to the image Produces image fog dulling of the image NOT representing diagnostic information At higher energies

Photoelectric and Differential Absorption
Provides diagnostic information X-rays do not reach film because they are absorbed Lower energies (more differential absorption) Gives us the contrast on our image

Image Production Beam Attenuation Attenuation is the reduction in intensity of an x-ray beam as it passes through an object due to the absorption and scattering of photons. The amount of attenuation that occurs depends on the intensity of the original x-ray beam and the physical properties of the object through which the x-ray beam passes.

Heat Brems Characteristic Patient Interactions Classic Coherent Compton Photoelectric Pair Production Photodisintegration Why These are Important? How our image is created Patient/Tech Safety

Patient/Tech Safety How do we measure Radiation and exposure to ensure patient safety? Units of measurement R, rad, rem Types of measurements conventional units, SI units Allowable dose limits general population patient dose fetal dose personnel doses Detection devices -personal and field TLD Pocket Dosimeter OSL Dosimeter Geiger Muller counter Ionization Chamber Governing bodies for doses NCRP NRC BEIR

UNITS OF RADIATION MEASUREMENT
To quantify the amount of radiation A: Received by Patient Employee Public

Units of Measure Roentgen Rad Rem

Unit of Exposure Exposure is a measure of the strength of a radiation field at some point in air. This is the measure made by a survey meter. The most commonly used unit of exposure is the roentgen (R). Roentgen: measures the amount of ionization in a certain amount of air after a certain measure of radiation exposure, abbreviated by “R”

ROENTGEN (R) Unit of measurement =measures ion pairs in a cubic centimeter at given conditions The quantity of radiation exposure in air Measures output of the x-ray tube Does not indicate the actual patient dose or absorption

Absorbed Dose Dose or Absorbed Dose: Absorbed dose is the amount of energy that ionizing radiation imparts to a given mass of matter. In other words, the dose is the amount of radiation absorbed by and object. The abbreviation for absorbed dose is “rad”.

Absorbed Dose

Dose Equivalent Dose Equivalent: The dose equivalent relates the absorbed dose to the biological effect of that dose. The absorbed dose of specific types of radiation is multiplied by a "quality factor" to arrive at the dose equivalent. Rem is an acronym for "roentgen equivalent in man."

Dose Equivalent

Roengten EQUIVALENT MAN (REM)
Different types of radiation produce different responses The unit of dose equivalence, expressed as RAD x QF = REM Used for occupational (employee) exposures Can be used when for dose of patient Not all types of radiation produce the same responses in living tissue The unit of dose equivalence, expressed as the product of the absorbed dose in rad (or gray) and quality factor. RAD x QF = REM used for occupational exposures can be used when for dose of patient

QUALITY FACTOR Qualifies what the damage is from
different types of radiation Example: QF for X-ray is 1 QF for alpha is 20 Alpha is 20 x more damaging to tissue Type of Radiation Rad Q Factor Rem X-Ray 1 Gamma Ray Beta Particles Thermal Neutrons 5 Fast Neutrons 10 Alpha Particles 20

Very low energy = More destructive

Why did the bunny die?? BUNNY A Received 200 rads BUNNY B

Why did the bunny die?? BUNNY A 200 rads x 1 for X-RAY = 200 REMS
BUNNY B 200 rads x 20 for alpha = 4000 REMS

Types of Measurement Conventional Units SI Units

Conventional vs. SI units
British units used since 1920’s United States still uses this system New system developed in 1948 System of Units based on Metric measurements developed by International Committee for Weights and Measures 1985- officially adopted

Conv. Units SI Units RADS REMS R GRAYS SIEVERT C/KG

Comparsion of Units

Comparison of Units Exposure R C/kg 1R=2.58x10-4 C/kg Absorbed Dose
Rad Gray 1rad=.01Gray 1Gray=100rad Dose Equivalent Rem Sievert 1rem=.01Sv 1Sv=100rem

RADS REMS RADS GRAYS Patient absorbed dose REMS SIEVERTS Employee
(technologists) =

REMS OCCUPATIONAL EXPOSURE R - ROENTGENS RADS – PATIENT DOSE

The exposure from an x-ray tube operated at 70kVp, 200mAs is 400mR at 36 inches. What will the exposure be at 72 inches? 100mR The x-ray intensity at 40 inches is 450mR. What is the intensity at the edge of the control booth which is 10 feet away?......think carefully… 50mR A temporary Chest Unit is set up in an outdoor area. The technique used results in an exposure intensity of 25mR at 72 inches. The area behind the chest stand in which the exposure intensity exceeds 1 mR. How far away from the x-ray tube will this area extend? 30 feet

The exposure from an x-ray tube operated at 70kVp, 200mAs is 400mR at 36 inches. What will the exposure be at 72 inches? 100mR Use Inverse Square Law The first exposure value is 400mR. The first distance is 36 inches. The second intensity is what we are looking for. The second distance is 72” Square both 72 and 36. Cross multiply Cancel out “inches2”, multiply, divide ?mR= 100mR

The x-ray intensity at 40 inches is 450mR
The x-ray intensity at 40 inches is 450mR. What is the intensity at the edge of the control booth which is 10 feet away?......think carefully… Use the Inverse Square Law. The first intensity is 450mR, the Second intensity is unknown. The first distance is 40 inches. The Second distance is 10 feet…..Convert feet to inches. So 10 feet is equivalent to 120 inches. Short cut method Cross multiply Cancel units

A temporary Chest Unit is set up in an outdoor area
A temporary Chest Unit is set up in an outdoor area. The technique used results in an exposure intensity of 25mR at 72 inches. The area behind the chest stand in which the exposure intensity exceeds 1 mR. How far away from the x-ray tube will this area extend? 30 feet Use Inverse Square Law. The first intensity is 25mR, the second Intensity is 1mR. The first distance is 72 inches, the second distance Unknown. Cross Multiply

Allowable Dose Limits An exposure of 500 roentgens in five hours is usually lethal for human beings. The typical exposure to normal background radiation for a human being is about 200 milliroentgens per year, or about 23 microroentgens per hour. In human tissue, one Roentgen of x-ray radiation exposure results in about one rad of absorbed dose (= 0.01 Gy). When measuring dose absorbed in man due to exposure, units of absorbed dose are used (the related rad or SI gray), or, with consideration of biological effects from differing radiation types, units of equivalent dose, such as the related rem or the SI Sievert.

PUBLIC EXPOSURE NON MEDICAL EXPOSURE
10 % of Occupational exposure 0.5 rad or 500 mrad or 5mGray Under age 18 and Students 0.1 rem

Education and Training Exposures
Student’s must never hold patients during exposures Effective dose limit (Annual) 0.1 rem or 1 mSv

Permissible Occupational Dose
Annual dose : 5 Rem/year 50mSv/year 5000 mrem Cumulative Dose 1 rem x age or 10mSv x age

Allowable DOSE - ANNUAL
CONVENTIONAL UNITS 5 REMS SI UNIT 5O mSv

OCCUPATIONAL EXPOSURES
5 REMS / YEAR BUT NOT TO EXCEED 1.25 REM/QUARTER

Allowable DOSE – TOTAL CUMMULATIVE
SI UNIT Age x 10msv CONVENTIONAL UNITS Age x 1 rem

Declared Pregnant Worker

Declared Pregnant Worker
2 badges provided 1 worn at collar (Mother’s exposure) 1 worn inside apron at waist level (baby exposure) Under 5 rem – negligible risk Risk increases above 15 rem Recommend abortion (spontaneous) 25 rem Must declare pregnancy – 2 badges provided 1 worn at collar (Mother’s exposure) 1 worn inside apron at waist level Under 5 rad – negligible risk Risk increases above 15 rad Recommend abortion (spontaneous) 25 rad (“Baby exposure” approx 1/1000 of ESE)

Pregnancy & Embryo Mother occupational worker Baby 5 rem
500 mRem or .5 rem/ year .05 rem/month

Embryo-Fetus Exposure limit
Radiation exposure is most harmful during the first trimester of pregnancy 0.05 rem or 0.5 mSv PER MONTH 0.5 rem or 5 mSv total gestation Embryo-Fetus Exposure limit

Fetus Exposure

Detection Devices Personal Monitoring Device Field Monitoring Device

Personal Radiation Monitoring
Monitors measure the quantity of radiation received by worker Every radiation worker must be monitored to determine the estimated exposure dose.

Personnel Monitoring Devices
Film Badges Thermoluminescent Dosimeters (TLD) Pocket Dosimeters Optically Stimulated Luminescence (OSL Dosimeters)

Personnel Monitoring Devices
worn at collar by employee film wedged between filters susceptible to fog from variety of factors should not be worn longer than 4 weeks Film badges

Personal Monitoring Devices- Film Badges – c changed monthly

Thermoluminescent Dosimetry (TLD)
Personnel Monitoring Devices Thermoluminescent Dosimetry (TLD) Based on property that x-ray can luminescence in certain materials Contains reusable crystal More expensive than film badge

Personnel Monitoring devices
Pocket Dosimeter Pen-like device Contains an ionization chamber Visible scale which provides estimate of gamma dose-provides immediate dose estimate

POSL Looks similar to film badges
Contains a piece of aluminum oxide instead of film Laser reads the luminescence to determine exposure Easy to change out, keep track of records

Field Survey Instruments
“Cutie Pie” Ionization Chamber Geiger Muller counter

Field Survey Instruments
Ionization Chamber: measures the ions in a gas chamber Cutie Pie Rad Cal Geiger-Mueller counter Several types of Ionization Chambers Scintillation Detector Based on principle that certain crystals emit light when struck by x-rays

Governing Bodies

REGULATORY AGENCIES Nuclear Regulatory Commission
National Council on Radiation Protection and Measurements NCRP - Reviews recommendation for radiation protection & safety. Distributes information re: radiation awareness Nuclear Regulatory Commission makes laws and enforces regulations

Review What is the annual allowable dose for a 32 year old Technologist?

What is the annual allowable dose for a 32 year old Technologist?
5 rem = 5000 mrem msv

What is the cummulative allowable dose for a 32 year old Technologist?

What is the cumulative allowable dose for a 32 year old Technologist?
32 REM or 320 mSv Or 3200 mrem

Patient Interactions.

Similar presentations

Presentation on theme: "Patient Interactions."— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Patient Interactions.

Similar presentations

Presentation on theme: "Patient Interactions."— Presentation transcript:

Similar presentations

About project

Feedback