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RAD 106 Exam 3
| What is x-ray intensity? | The number of x-rays in the useful beam? |
| What is the relationship between mAs and x-ray intensity? | X-ray intensity is directly proportional to mAs |
| What is the relationship between kVp and x-ray intensity? | X-ray intensity is proportional to kVp^2 |
| What is the relationship between distance and x-ray intensity? | X-ray quantity is inversely proportional to the square of the distance from the source (inverse square law). When SID is increased, mAs needs to increase to compensate. |
| What is the relationship between filtration and x-ray intensity? | Adding filtration to the useful x-ray beam reduces patient radiation dose |
| What determines the manner in which the x-ray beam interacts with the patient? | Energy |
| What is the relationship between penetrability and x-ray energy? | As the energy of an x-ray beam is increased, the penetrability of the beam through the patient or shielding material is also increased |
| What is penetrability? | It is the ability of x-rays to penetrate deeper in tissue and be transmitted through the patient to the IR |
| What is the half value layer and relationship with x-ray energy? | HVL is the thickness of material to reduce beam intensity by half. Attenuation is the reduction in x-ray intensity which results from absorption and scattering |
| What can x-ray beam energy be identified by? | kVp or filtration, but HVL is more appropriate |
| What are factors that affect x-ray energy? | Increasing kVp increases the energy of an x-ray beam. Increasing filtration increases the average energy of an x-ray beam. |
| What is inherent filtration? | It is already provided by the physical components built into the x-ray tube and housing |
| What is added filtration? | Attenuating materials placed in the path of the x-ray beam outside of the x-ray tube housing to achieve a certain beam quality |
| What is total filtration? | The sum of both added filtration and inherent filtration within the system |
| What is a compensating filter? | It absorbs parts of the radiation beam to balance exposure between thick and thin body parts, ensuring uniform image density and reducing overall patient radiation exposure |
| What is a wedge filter? | The most common type of compensating filter used in radiography to produce a balanced image receptor exposure when imaging body parts of uneven thickness. |
| What is a bow-tie filter? | A specialized compensating filter used exclusively in CT imaging to shape the x-ray beam intensity according to the natural contours of the human body |
| What is Coherent scattering? | An incoming photon changes its direction without changing its wavelength or losing energy. No ionization occurs and no energy is transferred to the body tissue. |
| What is Compton scattering? | An incoming photon collides with a loosely bound outer-shell electron, ejecting it from the atom and loses energy while changing direction. It causes ionization and is the primary source of radiation to radiologic technologists. |
| What is Photoelectric effect? | An incoming photon collides with a tightly bound inner-shell electron, surrounding all of its energy to eject the electron from its orbit. The photon is completely absorbed and creates diagnostic image contrast and radiation dose absorbed by the patient |
| What is Pair Production? | An incoming photon interacts directly with the strong nuclear force field of an atomic nucleus, completely disappearing and converting its pure energy into an electron and a positron. Primarily used in high-energy radiation therapy and nuclear medicine |
| What is Photodisintegration? | An incoming photon escapes the electron cloud and strikes the atomic nucleus directly, transferring all of its energy to shatter the nucleus and eject a nuclear fragment. Occurs only in specialized high-energy industrial applications |
| What is differential absorption? | The process where some x-ray photons are absorbed by the body while others pass completely through to hit the IR. Different tissues absorb x-rays at different rates. It increases as kVp decreases |
| What are examples of dependence on atomic number? | Photoelectric absorption is greater with higher atomic numbers, while Compton scatter is unaffected by the atomic number |
| What are examples of dependence on mass density? | Photoelectric absorption increases as mass density increases and Compton scatter increases as well |
| What two compounds are used as an aid for imaging internal organs with x-rays? | Barium and Iodine as they have higher atomic numbers and mass density |
| What is the atomic numbers of Barium and Iodine? | Barium is 56 and Iodine is 53 |
| Are Barium and Iodine contrast agents? | Yes as they are positive contrast agents |
| What is exponential attenuation? | It is how an x-ray beam decreases in intensity as it passes through a material. The number of photons in the beam drops by a fixed percentage for every equal thickness of tissue it crosses. It technically never reaches absolute zero intensity. |
| What is attenuation? | The reduction in the total number of x-ray photons remaining in an x-ray beam after it passes through a given thickness of material. It is combined as a result from absorption and scattering |
| What is the difference(s) between absorption and attenuation? | Absorption is a certain type of interaction where an x-ray photon transfers 100% of its energy to the body and completely disappears, while attenuation is the overall reduction in the total number of photons in the x-ray beam due to absorption and scatter |
| What are the critical steps for effective quality control? | Establishing baselines, define thresholds, document everything, schedule routines, and standardize testing |
| How does quality control measures impact patient safety and image quality? | Dose reduction, artifact prevention and elimination, diagnostic accuracy, and minimize repeats |
| What are some specific tests, maintenance procedures, or inspections for quality control? | Phantom testing, collimator accuracy, visual inspection, generator calibration, and quality control of display monitors. |
| What are the compliance, cost, and lifespan benefits of quality control measures? | Preventative savings, extended lifespan, regulatory compliance, and minimized downtime. |
| Does the National Council on Radiation Protection and Measurements (NCRP) and FDA have regulatory requirements regarding minimum filtration amounts in x-ray systems | Yes, for x-ray systems that are operating above 70 kVp, the minimum total filtration required is 2.5 mm Al/Eq. These laws ensure that x-ray machines operating in clinics have a standard "safety net" to catch low-energy x-ray photons. |
| HVL is lowered by a decrease in what? | kVp |
| When SID is increased, mAs must be increased by _ to maintain constant exposure to the image receptor. | Square of SID ratio |
| Added filtration will _ beam energy and _ HVL. | increase;increase |
| X-ray intensity is proportional to _. | kVp^2 |
| The main purpose of added filtration is to reduce _. | Patient dose |
| A compensating filer is used to create _ exposure with a body part of _ thickness. | uniform; nonuniform |
| A low-quality beam would also have low _. | Penetrability |
| Grays, or milligrays, in air are the measurement for x-ray _. | quantity; exposure and intensity |
| The inverse square law has the same effect on x-ray _ and x-ray _. | intensity;exposure |
| If filter thickness is _, then x-ray intensity is _. | increased;decreased |
| Coherent scattering is an interaction between _ x-rays and atoms | low-energy |
| The photoelectric effect is an interaction between an x-ray and a(n) _ electron that results in total x-ray absorption | inner-shell |
| At energies below 40 keV, the predominant x-ray interaction in soft tissue and bone is _. | Photoelectric absorption |
| Pair production is an interaction between an x-ray and a(n) _ that causes the x-ray to disappear and causes two electrons to take its place | nuclear electric field |
| Compton interactions, photoelectric absorption, and transmitted x-rays all contribute to _. | differential absorption |
| Compton scattering is an interaction between an x-ray and a(n) _ electron that results in ionization and loss of energy | Outer-shell |
| High kVp techniques reduce _. | Patient dose |
| Photodisintegration is an interaction that takes place at which energy level? | Energies higher than 10 MeV |
| A incident x-ray interacts with an atom without ionization during _. | Coherent scattering |
| Only at energies above 10 MeV can _ take place | Photodisintegration |
| An outer-shell electron is ejected and the atom is ionized during _. | Compton interactions |
| When the mass density of the absorber is _, it results in _ Compton scatter | increased; increased |
| _ occurs only at the very high energies used in radiation therapy and in nuclear medicine P.E.T. imaging | Pair production |
| Differential absorption in diagnostic imaging is primarily caused by _. | Photoelectric absorption |
| The use of contrast agents increases the amount of _. | differential absorption, compton scatter and photoelectric absorption |
| A negative contrast agent is _. | air |
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