Physics - Chapter 1

Who is the “father” of x-rays?

Wilhem Conrad Roentgen

Wilhem Roentgen - Facts and Dates

Born - 1845 in Lennep, Germany

PhD from University of Zurich - 1869

Discovered X-rays Nov. 8, 1895

First Radiograph of Wife’s Hand - Dec. 22 1895

Described practically every property of x-rays we know today.

Describe how Roengen discovered the x-ray

He was experimenting with a Crooks cathode ray tube while studying fluorescent properties of the cathode rays. He covered the tube with black cardboard, so no light could escape and noticed a piece of cardboard painted with barium platinocyanide fluoresced every time the tube was energized. He experimented with exposing photographic plates and found that the rays created a “photograph” on the plate. He called these rays x-rays, x standing for unknown variable.

Name 2 side effects from the first initial x-rays?

Acute Radiodermatitis (radiation burns)

Electrocution of the operator in setting up the equipment for exposure

What was the treatment for radiation burns?

Amputation

How long were the first initial exposure times?

20-30 minutes - 2 hours

Who brought attention to the dangers of x-rays?

Thomas Edison / Clarence Dally (Edison’s assistant who died from his injuries)

What were the identifying traits of people in the profession (Early days of x-rays)

Amputations and Gloved hands

True or False: Radiation can be contained?

False - they decrease with distance, but cannot be contained.

True or False: X-rays are stable atoms

False - Isotropic (unstable atoms) that go in all different directions

Define Ionizing Radiation

Radiation with sufficient energy to ionize atoms

True or False: A unit of measure must be agreed on and understood by a society to mean the same thing to all of its members.

True

Name the Fundamental Quantities

Mass, length, Time

Name the derived quantities

Velocity, acceleration, momentum, power, work, force

Name the radiologic / special quantities

Dose, Dose equivalent, Exposure, Radioactivity

What are the two systems of measure commonly used in radiologic sciences?

Imperial (British)

System International (SI) / Metric

What is Mass?

The quantity of matter contained in an object;

Does NOT change with gravitational force or if the substance changes form

What is Matter?

Anything that occupies space, has shape or form and has mass.

True or False: The Fundamental Quantities can be combined mathematically to create derived and special quantities

True

What is the equation for Velocity?

Velocity = Distance divided by Time

Units of measure = meters per second (m/s)

Velocity is the measure of speed

What is the equation for Acceleration

Acceleration = Final Velocity minus the Initial Velocity divided by Time

Units of measure = meters per second squared

Represents changes in velocity

What is the equation for Force

Force = mass multiplied by acceleration

Units of Measure = Newtons

Force is a push, pull or other action that changes the motion of an object

What is the equation for Momentum

Momentum (p) = mass multiplied by velocity

Units of measure = kilograms - meters per / second (kg-m/s

What is the equation for Work

Work = Force multiplied by distance

Units of Measure = Joule (J)

What is the equation for Power?

Power (P) = work divided by time

Units of measure = Watts (W)

What is Inertia?

The property of an object with mass that resists a change in its state of motion; applies to objects in motion and at rest.

The property of mass, and all objects with mass have inertia.

Newtons 1st Law of Motion

An object at rest will stay at rest unless acted on by an external force.

An object in motion will remain in motion at the same velocity and in the same direction unless acted on by an external force.

The ability to do work is

Energy

2 types of Energy

Potential Energy - Energy in a stored state

Kinetic Energy - Energy being expended; it is in the act of doing work

Describe the 4 forms of Energy

1) Electromagnetic - exists as an electric and magnetic disturbance in space

2) Chemical - exists through chemical reactions

3) Electric - created by the flow of electricity

4) Thermal - exists because of atomic and molecular motion

True or False: Matter can be transformed into energy, but energy can not be transformed into matter

False

The Coulomb/kilogram and the Roentgen are used to measure

Radiation intensity in air

What is ionization?

The removal of electrons from atoms

What is an ion pair?

An electron removed from an atom and the atom from which it came; the two together are an ion pair.

Conversion Factors - Coulomb/Kilogram // Roentgen

1 C/kg = 3876 R (divide)

1 R = 2.58 × 10 to the negative 4 (0.000258) (multiply)

What does the Gray / Rad measure?

Radiation Absorbed Dose (an expression of the quantity of radiation energy absorbed by tissues being irradiated)

Conversion Factors - Gray // Rad

1 Gray (Gy) =100 Rad —> (larger #)

1 Rad = 10 to the negative 2 (0.01) Gray (Gy) —> (smaller #)

What does the Sievert // REM measure?

Occupational Exposure / Dose Equivalent

REM = Radiation Equivalent Man

Conversion Factor - Sievert / REM

1 Sv = 100 rem (Larger Number)

1 rem = 10 to the negative 2 (0.01) Sv

What do the Becquerel and Curie measure?

Radioactivity

Becquerel - quantifying the number of individual atoms decaying per second

The process whereby a radioactive atom gives off particles and energy in an effort to regain a stable state

Disintegration / decay

Conversion Factors - Becquerel // Curie

1 Bq = 2.70 e x 10 to the negative 11 Ci (Divide)

1 Ci = 3.7 × 10 to the 10 Bq (Multiply)

An expression of the relative risk to humans of exposure to ionizing radiation is called

Effective Dose

True or False: All tissues, organs and systems have the same level of radiosensitivity

False

Kerma is an acronym for…

Kinetic Energy released per unit mass

What is Kerma? Air Kerma?

used to describe the quantity of radiation energy delivered to a given point;

A measure of energy released at a given point

Air Kerma - an expression of the quantity of radiation released in air

An expression of the amount of energy absorbed at a given point is called

Dose

What is the difference between mobile and permanently installed equipment?

Mobile Equipment is a unit on wheels

Permanently installed refers to units in a fixed place in a particular room; not intended to be mobile

What does the tube head assembly consist of?

x-ray tube, collimator, and tube stand

Which part of the x-ray equipment converts electrical energy into x-rays?

X-ray tube

Describe the anode and cathode of the x-ray tube

Anode - positive electrode over the head of the table

Cathode - negative electrode over the foot of the table

Which part of the x-ray equipment serves to restrict the x-ray beam to the area of interest of the body and helps localize the beam to that area?

Collimator

Which part of the x-ray equipment gives mobility to the x-ray tube and gives flexibility to produce an image from a variety of different angles and the ability to accommodate the patient’s condition?

The tube stand

What are the 3 basic configurations of the tube stand

The floor mount, the floor - ceiling (floor-wall) mount, and the overhead tube assembly (ceiling mount)

Which mount is most widely used in hospital settings and the most versatile in design?

The ceiling (overhead tube assembly) mount

What does the control panel do?

Used to select kVp and mAs

allows the radiographer to fine tune exposure parameters to obtain the best image

Control the electricity applied to the x-ray tube to produce x-rays

The ALARA principle states

it is the radiographers responsibility to minimize radiation dose to the patient, oneself and others in accordance with the As Low As Reasonably Achievable Principle

What are the cardinal principles of minimizing radiation dose?

MAXIMIZE shielding

MAXIMIZE distance

MINIMIZE time (exposure)

The use of radiopaque materials to greatly reduce radiation exposure to areas of the patient not essential to the examination being performed is defined as

Shielding

Refers to the duration of exposure to ionizing radiation and amount spent in a healthcare setting where exposure to ionizing radiation is accumulated; includes length of exposure and number of times being exposed

Time

Refers to the space between oneself and the source of ionizing radiation

Distance

True or False: The intensity (quantity) of radiation increases over distance

False: diminishes

True or False: The smaller the area of exposure, the lower the total dose to the patient

True

kVp controls blank whereas mAs control blank

kVp - penetrating power

mAs - number of photons produced (quantity)

The 15% rule state:

by increasing the kVp by 15%, we can reduce the mAs by ½ and still maintain optimum exposure to the IR.

True or False: To knowingly duplicate an exam because it is less time consuming than stopping to question is an obvious ethical violation

True

True or False: Routine or elective exams should be limited to 10 days before the onset of menstruation

False - 10 days AFTER to avoid fertile times or when the woman may be pregnant

True or False: The radiographer serves as a patient advocate and must pay attention to daily workflow as it relates to patient exposure

True