RADT 206 EXAM #1

The 18% increase in medical imaging is also resulting in an _______ average patient radiation dose

INCREASED

What is diagnostic efficacy

degree to which the diagnostic study accurately reveals the presence or absence of disease in the patient

• provides basis for determining whether the imaging procedure of practice is justified

Why are there concerns surrounding the increase of patient radiation dose

An increase in patient radiation dose could also mean an increase in stochastic and deterministic effects

What is STOCHASTIC

something that occurs years later and MAY be because of radiation

• could or could not be from radiation

What is DETERMINISTIC

dose that is determined … should the pt receive this dose in a short amount of time, there is an effect

• seen in fluoro/high cardiac fluoro studies

• happens within weeks or less

• definitely know it was from radiation

Describe CR (DR mode table)

• barium fluorohalide

• photo-stimulable phosphor

Describe SPR (DR mode table)

• NaI scintillator

• photodiode

Describe indirect DR (DR mode table)

• CsI

• charged couple device

OR

• CsI, GdOS scintillator

• thin film transistor

Describe direct DR (DR mode

• A-Se

• thin film transistor

Describe SPR

• Scanned Projection Radiography

• the “scout” image prior to most CT exams

• x-ray is energized but not rotating

• LOW radiation levels

What are the different ways to measure patient radiation dose

• ESE

• MMD

• GSD

• tissue dose

What does ESE stand for

Entrance Skin Exposure

What does MMD stand for

Mean Marrow Dose

What does GSD stand for

Genetically Significant Dose

What equipment is used to measure ESE

NOMOGRAMS and calculating through knowing output intensity for at least one operating condition (SID/kVp/mAs)

Describe the use of NOMOGRAMS to calculate ESE

• nomogram 1 →

  • curves on a graph, can estimate the output intensity of a radiographic unit if technique is known/assumed

  • use is a good approximation

• nomogram 2 →

  • more accurate, made individually for each radiographic unit

  • have to be given mAs/kVp

  • draw line between two points and intersection of that line with middle line on graph is mGyt

Describe how to solve ESE when comparing SID and SSD

(d1/d2)² = I2/I1

• d1 = SID

• d2 = SSD

• I2 = microGya2

• I1 = microGya1

• cross multiply

• e.g. →

  • (100 SID / 75 SSD)² / (x / 37 microGya)

  • (370,000 / 5625) = 66 microGya per mAs

Describe how to solve ESE when changing kVp

(new/old)²

• e.g. →

  • (76 kV/70kV)²

  • (1.09)² = 1.18

  • MULTIPLY that answer to the microGya per mAs

  • 66 microGya per mAs x 1.18 = 78 microGya per mAs

When kVp INCREASES, ESD _____

INCREASES

Describe how to solve ESE when changing mAs

multiply given mAs

• e.g. →

  • question calls for 80 mAs

  • 78 microGya per mAs x 80 mAs = 6240 microGya or 6.24 mGya

How do you convert microGya to mGya

you divide microGya by 1000

EXIT SKIN DOSE (ESD) is ________ of the ESE value

approximately 1%

Describe MMD

• cannot be directly measured

• estimation of the radiation dose getting to bone marrow

• believed that if it does, may cause stochastic effects like leukemia, lymphoma, etc

Describe GSD

• basically a gonad dose

• attempt to place a radiation dose value to our gene pool

• AVERAGES out those who have been irradiated vs those that have not

• this determines if radiation has contributed to genetic differences

Describe tissue weighting factors

states which tissues are more sensitive to radiation

• the HIGHER the weighting factor, the MORE sensitive it is to radiation

Order tissue weighting factors (high → low)

• 0.12 Wt

  • active bone marrow

  • colon (due to movement)

  • lung tissue (fragile)

  • stomach (due to movement)

• 0.05 Wt

  • bladder

  • breast

  • esophagus

  • liver

  • thyroid

• 0.02 Wt

  • gonad

• 0.01 Wt

  • bone surface

  • skin

What is a SENTINEL EVENT

unexpected occurrence that results in death, serious physical or psychological injury, or the significant risk thereof

Any skin dose exceeding ______ is a sentinel event and must be reported, as one of these events is always followed by severe skin damage

15 Gyt (during fluoro ?)

Describe DAP

Dose Area Product

• quantity that reflects not only the pt radiation dose but also amount of tissue irradiated

• mounted on collimator

• estimates how much entrance radiation skin is getting

• expressed in units of mGya cm²

DAP _______ with INCREASING field size even if the dose remains unchanged

INCREASES

______ field size results in LOWER DAP and less risk because LESS tissue is exposed

SMALLER

Describe the GANTRY of CT

Includes

• x-ray tube

• detector array

• high tolerance heat units

• pre-patient collimator

• high frequency generator

Describe the PATIENT COUCH of CT

• low z (atomic number)

• moves smoothly

• must index correctly to avoid imaging same tissue twice

• has a pre-detector collimator

Describe HELICAL MULTISLICE CT

couch is continuously moving while the tube rotates around

• today, essentially all CT imaging systems are third generation and utilize this

____ of exams are CT, but CT counts for ____ of patient’s total effective dose

15% … 50%

CT generally results in ____ patient exposure, but has finely collimated beam and minimized scatter

HIGHER

The HIGHER the multislice value the _____ the patient dose will be

LOWER

X-rays can result in a ____ ______ in the human body due to _______, the consequences of which can be measurable if significant damage results

molecular change … ionization

Describe the effects kVp has on the x-ray emission spectrum

when INCREASED, shifts to the RIGHT and amplitude INCREASE

Describe the effects mAs has on the x-ray emission spectrum

when INCREASED, amplitude INCREASES

Describe the effects filtration has on the x-ray emission spectrum

when INCREASED, shifts to the RIGHT and amplitude DECREASES

What is the difference between an ABNORMAL cell and a cell that has CEASED TO FUNCTION

abnormal cells function improperly, while cease to function is impairment or death of cell

When an atom is ionized, what changes

chemical binding properties

When a large molecule is ionized, what can happen

breakage or relocation of molecules occurs (becomes abnormal)

If there is a low enough amount of radiation, the cell has a chance of ______

recovery through repair

What does reversable mean

molecules that can become neutral again

How are molecules repaired when damaged

through repair enzymes/proteins

What are examples of DETERMINISTIC (nonstochastic) effects

• acute radiation syndrome

• local tissue damage

• hematologic depression

• cytogenetic damage

What are examples of STOCHASTIC effects

• leukemia

• other malignant diseases

• shortening of life span

• genetic damage

What are examples of FETAL IRRADIATION effects

• prenatal death

• neonatal death

• congenital malformation

• childhood malignancy

• diminished growth and development

What is the goal of radiobiology research

to study effects of radiation on tissue

What are the MACROMOLECULES

• proteins

• lipids

• carbohydrates

• nucleic acids

The body consists of these percentages →

• 80% water

• 15% protein

• 2% lipids

• 1% carbohydrates

• 1% nucleic acid

What is the smallest element of protoplasm

the cell

Which macromolecules contains enzymes for repair

protein

_______ provides most of the cell’s energy

carbohydrates

DNA and RNA are ______

nucleic acids

What is the function of LIPIDS

• store energy

• component of membrane

• protects against cold and heat

• assists in digestive process

• components of substances such as hormones

What is OSMOSIS

moving substances (water) inside and outside of a cell

What is HYPERTONIC (osmosis)

too LITTLE sodium inside or too MUCH potassium outside

• cell will collapse

What is HYPOTONIC (osmosis)

too MUCH sodium inside or too LITTLE potassium outside

• cell will swell

What is ENDOPLASMIC RETICULUM (cellular anatomy)

channels or series of channels that allows the nucleus to communicate with cytoplasm

What is GOLGI APPARATUS (cellular anatomy)

concentrates, packages and transports enzymes and hormones through the cell membrane

• minute vesicles that extend from the nucleus to the cell membrane

Nucleic acid in nucleus is critical and ______

radiosensitive

Put the phases of MITOSIS in order

• Interphase

  • G1

  • S

  • G2

• M phase

• prophase

• metaphase

• anaphase

• telophase

In what phase of MITOSIS can chromosome damage from radiation be SEEN

metaphase

• cell damage can happen from any stage, but earliest it is SEEN is metaphase

Tissues are groups of

cells

Organs are groups of

tissues

System is a group of

organs

Organism is

a human

Radiation is also given a weighting factor (Wr) … what are they?

• X-ray / gamma rays / electrons → 1

• Protons → 2

• alpha → 20

• the HIGHER the number, the HIGHER the impact/the HIGHER the ionizing

What is EqD

D x Wr

• D = dose

• Wr = weighting factor of radiation

• how much, what type of radiation

• applied when a person is exposed to different sources of ionizing radiation

• EQUIVALENT DOSE

What is EfD

D x Wr x Wt

• D = dose

• Wr = weighting factor of radiation

• Wt = weighting factor of tissue

• what tissue, what type of radiation, how much

• determines overall risk of exposure to ionizing radiation

• EFFECTIVE DOSE

What are the laws of BERGONIE and TRIBONDEAU

• HIGHLY mitotic, MORE sensitive

• HIGHLY metabolic, MORE sensitive

• undifferentiated, MORE sensitive

• YOUNGER age, MORE sensitive

What is LET

Linear Energy Transfer

• how much energy is transferred to the human body as it goes through it or stays in it

What is RBE

Relative Biologic Effect

• what did it effect

• what causes more damage

What is OER

Oxygen Enhancement Ratio

• how does oxygen play in scenario

Describe characteristics of LOW LET

• x-ray/gamma rays

• highly penetrating

• sparsely ionizing (can ionize, but not much)

• interacts randomly

• damage via INDIRECT action

  • does not hit the nucleus directly

• sublethal damage

  • repairable

  • low enough dose

Describe characteristics of HIGH LET

• particles of mass/charge

• particulate radiation

• alpha, neutrons

• is not penetrating (does not leave the body)

• very ionizing

  • constantly pumping out ionizing radiation

• damage via DIRECT action

  • hits the nucleus

• lethal damage

If LET is HIGH, then RBE is _____

HIGH

• a lot of energy is being transferred to tissue in HIGH LET, so the relative biologic effect would be higher as well

LOW LET has a ____ risk of damage to DNA/probability of interaction with DNA, while HIGH LET has a ______ risk

LOW … HIGH

What are the 4 methods of internal contamination

implanted, ingested, injected, inhaled

Describe RBE

the ability to produce biologic damage

• 200-250 kVp of known radiation over dose of test radiation = biologic effect

• weighting factor of radiation used to determine biologic damage

• comparing standard radiation with known effect to radiation with unknown effect and comparing weighting factor

• x-ray has RBE of 1

What is PROTRACTED dose

dose delivered continuously but at a lower rate

What is FRACTIONATION

dividing a dose of radiation into small amounts over a given time

• getting cumulatively irradiated avoids severe damage/death to cells

Describe OER

dose required to produce an effect in an oxygen deprived environment vs a normal oxygen environment

• OER is HIGH for LOW LET (OER of 3)

  • more sensitive to low LET

• OER is LOW for HIGH LET (OER of 1)

• something with HIGH oxygen is MORE sensitive to LOW LET

If a tumor was surrounded by oxygen, the tumor would be MORE sensitive to radiation in a _____ dose

LOW (low LET)

Radiosensitivity _____ with age

reduces

• increases somewhat in old age

Recovery is possible with _____ LET

LOW

What are MALIGNANT CELLS

• cells that divide abnormally

  • highly mitotic, highly metabolic

• increased amount of chromatin (information on cell)

• increased amount of nuclear material

• they are MORE sensitive to radiation

LET determines the WEIGHT of the ____, not the weight of the tissue or absorbed dose

radiation

The amount of energy deposited by radiation per unit length of tissue being traversed is what?

LET, which determines the use of a Wr when the equivalent dose is being calculated

Describe a LINEAR NON-THRESHOLD (dose response curve)

• anything above 0 results in response

• relates to stochastic response

• for x-rays

Describe a LINEAR THRESHOLD (dose response curve)

• has a gap between zero and beginning of response, not immediate

• states that there is a safe level of radiation before a known effect

• dose has been determined that it will have an effect at certain place

• relates to deterministic response

Describe a NON-LINEAR NON-THRESHOLD (dose response curve)

• not proportional

• lower curve is NONLETHAL dose, meaning there is a chance for recovery

• higher curve is DEATH, everything destroyed

• effect is not proportional to the dose

• not associated with anything specifically

• relates to stochastic response (?)

Describe a NON-LINEAR THRESHOLD (dose response curve)

• not proportional

• used for radiation therapy

• relates to deterministic response

• lower curve is NONLETHAL, chance for recovery

• higher curve is DEATH for cell

  • wanted in radiation therapy for tumor but could also potentially affect other surrounding healthy cells

What is X and Y on a dose response curve graph

X → dose

Y → reponse

What is another word for RADIORESISTANT

radioinsensitive

LETTER B (dose response curve)

Linear Non-Threshold

LETTER C (dose response curve)

Linear Threshold