Lecture Exam #2

Direct. When kVp is increased, the penetrability of X-ray beam is increased.

kVp has a ? relationship with density? Why?

mA has a direct relationship. If increase mA, it directly affects number of X-rays produced. If increase mA, density is increased. (brightness goes down.)

How is image density affected by milliamperage?

By the pixel size of each data element Images consist of pixel elements in a rectangular array

How is image resolution determined?

mA x time

How is mAs calculated?

By alignment of CR (needs to be on correct part of anatomy), patient's anatomy (part being parallel to IR), and IR (IR should be parallel to tube. IR

How is shape distortion controlled?

By using longer SID's & minimum OID's

How is size distortion (magnification) avoided?

If you increase your time, density increases (brightness goes down.)

How is image density affected by exposure time?

Photostimulable storage phosphor (PSP) technology

A digital receptor (DR) system is what kind of technology?

Photographic qualities and geometric qualities

A high-quality diagnostic radiograph must possess a good balance of what?

That it has many different energies

An x-ray beam is probably energetic or heterogenous which means?

No excuse

Automatic rescaling is _______________ for exposure technique selection inaccuracies.

System speed

DR systems can be operated at varying system sensitivity is known as?

Latent image: we can't see the image. Remnant radiation has made chemical changes on IR. Manifest image: the visible image. What we can see.

Differentiate between a latent image vs manifest image.

They take a wide range of techniques and make each image acceptable.

Digital detectors possess greater exposure latitude than conventional film screen systems because?

Recorded detail, sharpness of detail, and definition

Geometric qualities are also known as?

Visibility of detail which is a photographic property. These consist of brightness & contrast.

Geometric qualities are complemented by what?

Optimum use of focal spot size (we use smaller for extremities) Decrease OID- place part as close to IR as possible Optimum use of SID- as increase SID, we use less beam divergence which decreases sharpness.

How can image unsharpness be prevented?

Reduce exposure time, immobilize patient (sponge, blanket), patient hold breath, effective communication so patient knows what they need to do. If involuntary motion: decrease the time of exposure

How can radiographers lessen the unsharpness of a radiograph?

Give clear instructions, decrease exposure time.

How do we prevent movement during an x-ray?

By affecting image resolution (how clearly we can see between 2 structures), size (if larger-magnification) and shape (can have shape distortion where image looks shortened or elongated)

How do you geometric qualities contribute to image quality?

OID is distance between patient & IR. We want least amount of OID as possible. As OID increases, we lose detail because it appears magnified on IR.

How does OID affect recorded detail on an image?

As we increase SID, we increase or resolution (detail) because we have less magnification. As we decrease SID, we decrease amount of detail because the part appears more magnified.

How does SID affect recorded detail on an image?

The farther you move your tube from the IR, the less intense. Intensity goes down, brightness goes up & vice versa.

How does distance affect image density?

We don't want it because it affects how well we see that detail.

How does distortion affect geometric qualities?

Loss in resolution caused by dimensional shape of the actual target area on the anode surface. Where the electrons strike the surface of anode is determined by whether you select small or large focal spot on control panel. Small (collimating down) means electrons strike smaller area on anode, large means they strike a larger area.

How does focal spot size affect recorded detail? (Anode heel effect)

We don't have control over material unsharpness. It is a loss in resolution caused by the inherent characteristics of the IR material. Digital detector unsharpness is caused by the pixel element size of the detector technology. The more pixels we have the better the resolution.

How does material unsharpness affect recorded detail on an image?

Exposed IP in cassette is placed in a reader for electronic processing of the latent image into a manifest image (we can see) displayed on a monitor. Eliminates the need for an x-ray film dark room Creates a digital image through computer software

How does the DR system work?

Small gives better detail to see the bony trabecular detail and see cortical outline.

How does the focal spot size affect geometric qualities?

Accomplished by angling or rotating the patient relative to the central ray of the X-ray beam. Helps overcome superimposition of anatomic structures. Ex. Coyle method of elbow. 45 degree angle so we can see radial head. If no tube angle we couldn't see radial head.

How is deliberate distortion accomplished & why? Example?

If increase SID, density goes down (brightness goes up.)

How is image density affected by SID?

By using the smallest focal spot size possible based on X-ray tube manufacturer's specifications. Complications: We use small for extremities, but we have to use that for smaller techniques. If we select a small focal spot size, use it for small body parts & small technique. If we use a small focal spot size & larger technique there are too many electrons striking a smaller surface area on anode which creates more heat & can damage the tube.

How is unsharpness reduced with focal spot size?

The remnant radiation from the patient and converted into chemical or electrical changes that make up the latent image. Latent means that there are x-ray photons that have come in contact with the image receptor but you just can't see them yet. We have to make it visible.

Image receptor's detect what?

Primary radiation: the radiation exiting the X-ray tube. Scatter radiation: detrimental, produced from Compton Scattering, produces a fog on x-ray. Is non diagnostic radiation-doesn't contribute to image. Absorbed radiation: radiation that stays in the patient. From a photoelectric effect. Increases patients radiation dose. Remnant radiation: all radiation that strikes the IR after it passes through the matter

List & describe the 4 classes of radiation.

Use a grid for bigger body parts. Use beam restriction or collimation. If you are increasing your use of beam restriction it means that you are making your light field smaller or collimating.

List ways to control scatter radiation:

Brightness: window level (WL) Contrast: window width (WW)

On an image display (monitor) what controls brightness? What controls contrast?

Look at the SI# or exposure index # which verifies the amount of radiation that is acceptable Follow ALARA (make sure not overexposing patient)

Several key factors must be considered when evaluating proper IR exposure such as?

Indirect Direct

Two methods of digital image capture on a digital cassetteless system includes?

Milliamperage (mA), exposure time (s), source to image distance (SID).

What is the image density primarily affected by?

Barium enema, upper GI, videgrams, arthur swallows.

What are examples of fluoroscopy?

The focal spot size, OID, SID, motion, distortion. Are the details on our x-ray that we get by smaller focal size, reducing a OID, reduce movement, increase exposure time.

What are geometric qualities?

The prime factors of exposure technique.

What are milliamperage (mA), kilovoltage peak (kVp), & source-to-image distance (SID) often referred to as?

Are controlled by brightness in contrast.

What are photographic qualities?

Fluoroscopic imaging Digital or computerized imaging (CR)

What are the classes of diagnostic radiographic imaging?

Uses no cassettes Image display is in seconds Detectors can be direct or indirect (light or no light) Both types use thin film transistors Brightness of an image is not the same as radiographic density & not related to exposure.

What are the key features of digital radiography?

Milliamperage (mA): Milliamperage- current that we apply to the X-ray tube. Controls amount of electrons passing from cathode to anode Time: measured in seconds. Is how long we allow electrons to travel. Kilovoltage peak (kVp): Controls penetrability if X-ray beam. Is the power behind the beam. Affects beam quality & beam quantity. Have to be able to penetrate through body. Source-to-image distance (SID): distance from X-ray tube to receptor. Affects our density.

What are the prime factors of exposure technique? What are they? What is their function?

1. X-ray tube with a vacuum inside (contains a vacuum so no other atoms can react with the electrons that are produced in X-ray tube). 2. Source of electrons: Cathode-happens on cathode side, filament that is made out of tungsten, gives off electrons when heated. 3. Method to accelerate electrons to great speed: Voltage- controls the speed of electrons across an X-ray tube. 4. Method to stop electrons: Target- is the abode which is made out of tungsten. Tungsten has high melting point & high atomic #. 99% heat produced, 1% x-rays.

What are the requirements involved with x-ray production?

Film screen Photo stimuble phosphor system: more common with computed radiography (almost non existent) Digital detector systems: 1. Indirect 2. Direct

What are three types of image receptor's?

Size distortion Magnification

What are two types of distortion?

Filtration: inherent- already in X-ray tube, consists of aluminum. Helps remove low energy x-ray beam already there. Low energy photons can't penetrate through patient, so they would just get absorbed if not removed. Beam limitation: also known as collimation. If you include collimation it helps reduce the patient does and helps get rid of scatter.

What are two types of primary beam modification? And what are they?

SI #'s

What can the EI (exposure index) also be called?

Cathode: a filament that gives off electrons when heated (the source of electrons) Anode: a positive electrode toward which negatively charged electrons migrate.

What does an X-ray tube consist of?

Allows images to be transferred safely from safely from one network to another instead of printing film. Allows us to transmit images to other facilities Stored more compactly & decreases need for off site storage.

What does the PACS system allow us to do?

X-ray beam penetration. Is the power behind the beam.

What does the kilovoltage peak (kVp) control?

Motion Object unsharpness Focal spot size SID OID Material unsharpness Distortion

What factors affect recorded detail on an image?

Primary radiation from the X-ray tube travels through matter, & it's energy is finally detected by an image receptor. Remnant radiation creates chemical changes within the receptor that are invisible (latent image) The latent image must be processed to convert it to a visible image.

What happens during an x-ray that allows us to see the image? (imaging chain)

You get noisy or grainy images. Looks like drops of rain on a dry sidewalk.

What happens if you have two little exposure on an image?

The brightness will go up

What happens to brightness if you were x-raying a thicker body part?

We get less magnification and more detail

What happens to magnification if we increase our SID?

Patient dose is decreased because the penetrability of the X-ray is increased.

What happens to patient dose as we increase our kVp?

Can reduce the image contrast

What happens with too much exposure on an image?

Provides cross sectional views of the body. Helps with better diagnosis & eliminates exploratory surgery. Gives us slices to look at inside of patients anatomy. Called spiral or helical because of way it acquires image.

What is Computed Tomography?

Magnetic resonance imaging Uses magnetic field & radio waves Is used for viewing both anatomy & physiology Causes the hydrogen atoms in the body to change direction which allows us to view the anatomy. Does not produce ionizing radiation because it uses radio waves.

What is MRI?

Positron emission tomography Detects anatomy & function Is most commonly used to stage cancer. Radiopharmaceutical is injected into vein.

What is PET?

Cassette with IP placed in CR reader Reader scans the IP with laser energy and recovers the energy from the electron traps. Energy converts into manifest image or image we can see.

What is a CR reader?

Computed radiography (CR) CR is a storage phosphor technology.

What is a digital receptor (DR) system also known as?

Used to reduce the amount of scatter radiation reaching the image receptor. Intercepts a portion of the remnant radiation. Improves image quality. Are described according to grid ratio and frequency. Necessitate an increase in exposure to compensate for grid.

What is a grid?

Density (brightness in digital) & contrast if the image can be altered. Also post processing capabilities. We cannot alter without permission.

What is an advantage of digital imaging?

The loss of radiation energy as a result of passing through an absorbing material, such as the human body. The degree of attenuation can be high or low.

What is attenuation?

Computer software optimizers image quality by varying the brightness and contrast of the image on the basis of the exposure to the receptor.

What is automatic rescaling?

The x-ray beam can be modified before and after it enters the patient. Beam alterations can improve image quality and reduced dose.

What is beam modification?

Uses amorphous selenium as the active detector material (is inside IR) Uses TFT to capture electrons from x-ray interactions TFT collects and amplifies the electron signal Electrons signals are converted to computer data and displayed as an image

What is direct detector technology?

Any misrepresentation of the true size or shape of the patients anatomy as demonstrated on the radiographic image.

What is distortion?

A "live action" view of the interior of the body. Uses an image intensifier that electronically improves & enhances the image & transmits it to the television monitor.

What is fluoroscopy?

X-ray exposure hitting the receptor.

What is image density directly related to?

The overall darkness or blackness of an image.

What is image density?

Uses a scintillator (cesium iodide-produces light) material bonded to amorphous silicon The scintillator receives the x-ray energy and converts it to light energy Light energy is captured by amorphous silicon and converted to electrons Electrons are collected by TFT (thin film transistor) and sent to computer

What is indirect detector technology?

Voluntary: breathing moving Involuntary motion: peristalsis, Parkinson's

What is motion usually caused by? What are they?

Patient is injected or ingests radiopharmaceuticals. They are specific for the area being examined. The camera has sensors that detect emission of radiation from that area of the body which then produces the image.

What is nuclear medicine?

Loss in resolution (detail) caused by the inherent shape of the patients anatomic structures relative to the divergence of the X-ray beam.

What is object unsharpness?

Amount of unsharpness on an image.

What is panumbra?

Used when a patient cannot leave their dept. Have to use grid because won't have a Bucky with you. Have to wear lead apron when performing. Patient mobility , radiation dose

What is portable radiography used for?

Regardless of the mA & time combination, the same mAs value will yield the same exposure.

What is reciprocity of law?

Interaction of x-rays with any matter produces scatter radiation. Provides a little diagnostic information to image. Detracts from image quality with the creation of fog

What is scatter?

Any misrepresentation of the true shape of the patient's anatomy. Can get if tube angle isn't supposed to be used on an exam. Ex. Elongation, foreshortening Also called true distortion. Sometimes we may deliberately have shape distortion to deal with superimposed structures.

What is shape distortion? What is it also known as?

The image is always slightly larger than the actual object size. Magnification. We will always have some type of magnification.

What is size distortion? What is it also known as?

Ultrasound Sound waves bounce off of anatomy & are received by a transducer. Does not use ionizing radiation

What is sonography?

Involves using a c arm for surgeries, cardiac labs, bedside, pain clinic.

What is surgical radiography?

States that if we increase kVp by 15%, it's the equivalent of doubling our mAs. If we double our mAs, it doubles our X-ray exposure, our IR exposure or the X-ray quantity.

What is the 15% rule in regards to kVp?

A numeric representation of total x-ray exposure to the receptor. Tells us if we under or over exposed our patient Is not an indicator of the patients absorbed dose Values can vary greatly among manufacturers

What is the exposure index (EI)?

The amount of absorbing material that will reduce the intensity of the x-ray beam to half its original value. Used as a way to express x-ray beam quality. The absorbing material is typically aluminum

What is the half layer value?

It is used to calculate intensity with distance. Old intensity/ new intensity = (new distance) squared/(old distance) squared. States if we increase our distance by two, the intensities of the x-rays on the IR will reduce by a factor of four. If we cut our SID in half, the intensity of the x-rays on the IR will increase by a factor of four.

What is the inverse square law?

Light. 1 produces, 1 doesn't Indirect produces light, direct does not.

What is the main difference between direct and indirect detector technology?

Motion (most detrimental)

What is the most common cause of image unsharpness?

Cassette with imaging plate (IP) The IP is reusable for thousands of exposures.

What kind of imaging plate is used for digital receptor (DR)?

May need to change mA & time combination.

What might need to be done when you have involuntary movements with a patient such as Parkinson's, or peristalsis?

X-rays were discovered in 1895 X-ray beam energy us produced using high voltage electricity X-rays pass through matter & strike an image receptor Image receptor converts the energy of x-rays into an image. (1st x-ray took 15 mins)

What processes are involved in image production?

Good geometric qualities & visibility of detail

What two things do we have to have for a high-quality radiographic image?

Occurs in radiopaque matter which appears white on an X-ray. Matter that is difficult for radiation to pass through. It loses radiation energy as it's trying to penetrate through bone. We can give patient contrast (barium iodine). Ex. Iodine, barium, & bone all show up white. Barium & iodine have high atomic #

When does high attenuation occur?

Occurs in radiolucent matter. Matter that is easy for x-rays to penetrate through. Appears black in an x-ray. Ex. air in lungs. Air is easy to penetrate through. Not as dense.

When does low attenuation occur?

That it behaves according to the laws of light and intensity as a function of distance.

X-ray production is similar to appoint light source which means what?