Physics Flashcards

Question

What does the term 'heel effect' refer to?

Answer 1

Variation/spectrum in beam intensity, strongest beam closest to cathode

Answer 2

2.5 mm aluminum

Answer 3

Peak kilovoltage

Answer 4

* Increases maximum X-ray energy * Increases average X-ray energy * Increases total number of X-rays produced

Answer 5

Beam intensity increases as square of kVp

Answer 6

Mass attenuation is not affected by density of material

Answer 7

Amount of material required to attenuate X-ray to half original output

Answer 8

* Increased filtration -> decrease quantity * Increased filtration -> increase quality

Answer 9

Compton scatter

Answer 10

Difference between X-rays that are absorbed or pass right through

Answer 11

X-ray strikes inner shell electron and removes it from orbit, completely absorbed

Answer 12

Probability of photoelectric interaction is directly proportional to atomic number cubed (Z^3)

Answer 13

Linear relationship of X-ray and attenuating substance

Answer 14

* Tube current (mA) * Time of exposure (s) * Peak kilovoltage (kVp)

Answer 15

Noisy image due to not enough X-rays reaching film/detector

Answer 16

Mostly Compton interactions

Answer 17

More penetration (decreased attenuation) ## Footnote Higher kVp allows more x-rays to pass through the body, reducing the amount of radiation that is absorbed.

Answer 18

More signal to noise ## Footnote Increasing the number of photons improves the overall quality of the image by reducing noise.

Answer 19

Noisy image due to not enough x-rays reaching film/detector ## Footnote It is the most important source of random noise in radiographic imaging.

Answer 20

By increasing x-ray (mAs) or using more efficient detection ## Footnote Increasing the mAs results in more photons, which helps improve image quality.

Answer 21

Compton interactions ## Footnote Compton scattering is a critical factor in determining the quality of radiographic images.

Answer 22

* kVp * Thickness of the body part * Field of view (FOV) ## Footnote Higher kVp increases scatter, thicker body parts have more interactions, and smaller FOV decreases scatter.

Answer 23

Decreases noise (scatter) ## Footnote While collimation reduces scatter, it may also lower the signal to noise ratio, necessitating increased mAs.

Answer 24

Improves contrast by reducing scatter ## Footnote Using a grid involves a tradeoff of increased dose/mA.

Answer 25

Risk of using grid that blocks too many photons ## Footnote Can lead to quantum mottle and a noisy image if the grid is misaligned.

Answer 26

Air gap technique ## Footnote This technique helps in minimizing scatter radiation affecting the image quality.

Answer 27

How dark the film is ## Footnote Increased exposure leads to darker films, resulting in higher radiographic density.

Answer 28

Decreases quantum mottle, but increased kVp also increases Compton scatter ## Footnote The balance between mA and kVp is essential for optimal image quality.

Answer 29

Energy twice as far from source is ¼ the intensity ## Footnote As distance increases, the energy is spread over a larger area, resulting in more noise.

Answer 30

Noise increases as distance increases ## Footnote Greater distances can lead to reduced image clarity.

Answer 31

How visibility of finding is affected ## Footnote CNR is a critical factor in image interpretation.

Answer 32

By increasing mA ## Footnote This method enhances visibility without altering contrast.

Answer 33

How close two lines can be to one another and still visibly resolved ## Footnote High spatial resolution is crucial for detailed imaging.

Answer 34

Loss of spatial resolution ## Footnote It can occur due to various factors including motion and system limitations.

Answer 35

Blur caused by the focal spot size and distances ## Footnote Smaller focal spots reduce blur but can increase exposure time.

Answer 36

More magnification leads to more blur ## Footnote Magnification is calculated by the ratio of source to image distance (SID) to source to object distance (SOD).

Answer 37

More pixels per unit area, better spatial resolution ## Footnote Higher pixel density improves the clarity and detail of digital images.

Answer 38

Information recorded/information available ## Footnote MTF indicates the accuracy of the imaging system in reproducing detail.

Answer 39

Efficiency of detector to convert x-ray energy into image ## Footnote DQE helps predict the dose required for optimal imaging.

Answer 40

DQE is directly proportional to MTF and inversely proportional to SNR ## Footnote This relationship highlights the trade-offs in imaging efficiency.

Answer 41

* Linear attenuation coefficient * Energy (kVp) * Density * Atomic number ## Footnote Adjusting these factors can significantly improve image contrast.

Answer 42

Radiowaves, microwaves, infrared, visible light, UV, Xray/gamma ray ## Footnote This order represents the electromagnetic spectrum from lowest to highest energy.

Answer 43

2 protons and 2 neutrons ## Footnote Alpha particles have a net charge of 2+.

Answer 44

Cannot travel far, or penetrate deep ## Footnote Alpha particles are relatively heavy and positively charged, limiting their range.

Answer 45

Electrons which are emitted from the nucleus ## Footnote Unlike alpha particles, beta particles are lighter and can travel farther.

Answer 46

Electrons ## Footnote X-rays originate from the interaction between fast moving electrons and atoms.

Answer 47

Nucleus of atom ## Footnote Gamma rays are emitted as excess energy when an atom decays.

Answer 48

Help electron beam strike the target in acceptable size and reduce spatial spreading ## Footnote The focusing cup has a negative charge around the filament.

Answer 49

A vacuum ## Footnote This allows the speed and amount of electrons to be controlled independently.

Answer 50

Radiation released due to diversion of bombarding electron interacting with entire atom ## Footnote It is proportional to the energy of incoming charged particles and atomic number Z.

Answer 51

Low Z materials like plastic ## Footnote Using lead would increase bremsstrahlung production.

Answer 52

Ejected outer shell electron after energy imparted to it from filling inner shell vacancy ## Footnote This process occurs with lighter elements like tissues.

Answer 53

Binding energy of shell ## Footnote The energy released is equal to the difference in binding energies between outer and inner shells.

Answer 54

Exact and discrete energies ## Footnote They are depicted as sharp peaks over the bremsstrahlung continuum.

Answer 55

Heavier elements like tungsten ## Footnote Characteristic radiation occurs when outer shell electrons fill inner shell vacancies.

Answer 56

Quantity of x-rays produced, not quality.

Answer 57

Exposure time impacts quantity, not quality.

Answer 58

Affects quality and quantity of x-rays.

Answer 59

To denser/thicker tissue, unless it is pediatric thigh.

Answer 60

Blocks soft x-rays that don’t help imaging but add dose.

Answer 61

Higher Z increases bremsstrahlung x-rays produced and affects characteristic x-ray energy shell levels.

Answer 62

Maximum x-ray energy will increase to match kVp.

Answer 63

Average x-ray energy is ⅓ to ½ of maximum energy.

Answer 64

Lose characteristic peaks.

Answer 65

The number of electrons per amount of time.

Answer 66

Quantity of x-rays increases.

Answer 67

If kVp x 1.15 then mA/2 maintains same x-ray density; if kVp x 0.85 then mA x 2 maintains same density.

Answer 68

Amount of material required to attenuate x-ray to half original output.

Answer 69

* Beam filtration * Anode material * kVp * Wide beam

Answer 70

* Tube current * Tube potential * Voltage generator * Atomic number * Filtration

Answer 71

Restricting size and shape of x-ray beam.

Answer 72

X-ray strikes orbital electron and bounces off, no ionization or contribution to image.

Answer 73

X-ray strikes outer shell electron, removes it, and atom is ionized.

Answer 74

Compton scatter.

Answer 75

Photoelectric interactions.

Answer 76

* Photon energy * Atomic number of the absorber

Answer 77

More PE, more dose; more PE, more contrast.

Answer 78

More kVp, less PE.

Answer 79

Increased probability when binding energy and incident photon energy are similar.

Answer 80

incident photon energy cubed (1/E^3).

Answer 81

atomic number cubed (Z^3).

Answer 82

Photoelectric effect (PE) and Compton scattering ## Footnote PE contributes to image quality while Compton scattering degrades it.

Answer 83

Transmission decreases ## Footnote Increased PE leads to greater absorption and attenuation.

Answer 84

* Higher atomic number * Increased tissue density * X-ray beam energy (kVp) closer to K edge

Answer 85

* Increased probability of PE at lower keV * Increased relative probability of Compton at higher keV

Answer 86

Rate of energy loss by X-ray beam as it travels through a material ## Footnote It is not affected by the density of the material.

Answer 87

The probability of a material to attenuate X-ray beam over a set distance ## Footnote It is affected by the density of the material.

Answer 88

* Tube current (mA): proportional * Time of exposure (s): proportional * Peak kilovoltage (kVp): square * Distance

Answer 89

Noisy image due to not enough X-rays reaching the film/detector ## Footnote It is the most important source of random noise.

Answer 90

* Increase X-ray (mAs) * Use more efficient detection

Answer 91

* kVp: higher kVp results in more Compton scatter * Thickness: thicker body part has more scatter interactions * Field of view: smaller FOV decreases Compton scatter

Answer 92

Decreases noise (scatter) ## Footnote This results in lower signal to noise, requiring an increase in mAs to compensate.

Answer 93

Block too many photons leading to quantum mottle/noisy image ## Footnote Can occur when the grid is incorrectly aligned (upside down, wrong distance, off center).

Answer 94

It is ¼ the intensity ## Footnote The energy is spread out across four times the area, leading to more noise.

Answer 95

Noise increases as distance increases

Answer 96

The mottle is cut in half

Answer 97

Noise is fixed

Answer 98

By decreasing kVp which improves contrast

Answer 99

Less blur ## Footnote Smaller spots are used in mammography to compensate for blur related to magnification and in extremity exams to maximize spatial resolution.

Answer 100

Motion artifact ## Footnote It allows for more mA and less exposure time, thus decreasing blur.

Answer 101

By decreasing energy (kVp), increasing density, or increasing atomic number

Answer 102

Efficiency of detector to convert x-ray energy into image

Answer 103

Low DQE indicates high dose and high spatial resolution; high DQE indicates low dose and low spatial resolution

Answer 104

MTF (Modulation Transfer Function)

Answer 105

SNR (Signal-to-Noise Ratio)

Answer 106

More pixels per unit area lead to better spatial resolution

Answer 107

Measurement from center of one pixel to the next

Answer 108

Pixel size and pixel pitch

Answer 109

Better spatial resolution

Answer 110

Large matrix leads to small pixels, resulting in better spatial resolution

Answer 111

More magnification leads to more blur

Answer 112

By SID/SOD (Source to Image Distance / Source to Object Distance)

Answer 113

Brightness gain is the combined effects of flux gain and minification gain ## Footnote Brightness gain is crucial for understanding how image quality is affected in radiography.

Answer 114

Flux gain is the increase in magnitude of light from output phosphor relative to input, accomplished with higher voltage, increasing brightness ## Footnote Flux gain plays a key role in enhancing image brightness.

Answer 115

Minification gain is the concentration of electrons from a large photocathode to a small output phosphor, increasing electron and thus energy per unit area, increasing brightness ## Footnote Minification gain contributes to the overall brightness gain.

Answer 116

The ability of the intensifier to increase brightness deteriorates with age, requiring more dose to produce the same level of output brightness ## Footnote Aging tubes may lead to decreased image quality and increased radiation exposure.

Answer 117

Both electronic and geometric magnification increase dose ## Footnote Understanding the relationship between magnification and dose is vital for patient safety.

Answer 118

Geometric magnification involves moving an object closer to the focal spot to improve spatial resolution, but it increases blur ## Footnote Geometric magnification is a trade-off between resolution and image clarity.

Answer 119

To compensate for increased blur from geometric magnification, the focal spot is decreased in size ## Footnote Adjusting the focal spot size is a common technique in radiographic imaging.

Answer 120

The R/F ratio describes the relationship between intrinsic receptor resolution and focal spot size ## Footnote The R/F ratio is an important parameter in evaluating image quality.

Answer 121

If R/F is greater than 0.5, then magnification will increase sharpness ## Footnote Higher R/F ratios are often desired in imaging for better resolution.

Answer 122

In general radiography, R/F is less than 0.5, so magnification decreases resolution ## Footnote This highlights the limitations of magnification in general radiographic practices.

Answer 123

In mammography, R/F is greater than 0.5, so magnification increases resolution ## Footnote Mammography benefits from higher R/F ratios to enhance image clarity and detail.

Answer 124

increases dose by 1.4- 2.0x

Answer 125

xray tube far from patient, II close to patient

Answer 126

decrease dose, scatter, and blur/magnification (which improves image sharpness)

Answer 127

Minification gain ## Footnote Brightness gain refers to the increase in brightness perceived when viewing through an optical system.

Answer 128

More minification (less magnification) = more brightness ## Footnote A larger field of view generally allows for a wider perspective but at the cost of less magnification.

Answer 129

Less minification (more magnification) = less brightness ## Footnote A smaller field of view can provide greater detail through magnification but results in reduced overall brightness.

Answer 130

False ## Footnote A larger field of view decreases magnification.

Answer 131

increases exposure to maintain brightness

Answer 132

Decrease beam area, but compared to electronic magnification, no increase in beam dose

Answer 133

Air kerma and skin dose ## Footnote Electronic magnification enhances the radiation dose received by the skin and the air kerma, which is the kinetic energy released per unit mass in air.

Answer 134

Kerma area product (KAP) ## Footnote KAP is a measure of the total amount of radiation delivered to a specific area and remains unchanged with electronic magnification.

Answer 135

1) Move patient away from source, closer to image intensifier/detector 2) increase collimation (small field of view) 3) avoid magnification

Answer 136

87 mGy per min or 10 R/min (High level control is double)

Answer 137

Pincushion, s distortion, vignetting, glare, and saturation artifacts

Answer 138

Increases signal to noise ratio (SNR), but decreases spatial resolution Binning only applies to FPD

Answer 139

Pulses of higher mA instead of continuous mA If frame rate is below 30 from/sec, overall dose is reduced (though each individual pulse will have more mA)

Answer 140

FOV (smaller is better), focal spot size, image receptor limitations (FPD detector element and II television), motion factors, dynamic range, pixel binning (decrease spatial resolution but improve SNR), frame averaging, pulsed fluoro (better for spatial resolution)

Answer 141

Peds and extremities (less tissue)

Answer 142

Inverse square law dictates relationship between dose and distance Direct relationship between dose and exposure time

Answer 143

Never use above diaphragm Never use in pts getting nitrous oxide Place pt in trendelenberg

Answer 144

70, to maximize iodine k edge of 33

Answer 145

Filters out low energy xrays, increasing average energy (higher energy beam aka increased penetrating power) and half value layer Decreases contrast

Answer 146

Too much mA (and kVp) causes overexposed (too dark) Too little mA causes underexposed (too bright/mottled)

Answer 147

Increases dose and motion blur, decreases mottle/noise If there is AEC and the exposure is increased, dose is maintained, which also does not decrease mottle/noise, but motion blur still increases

Answer 148

Different thickness, density and atomic number

Answer 149

Low kVp High density (barium) High atomic number (iodine) Decrease scatter (grid or air gap) Decrease filtration NOT AFFECTED BY MAS

Answer 150

Cesium iodide scintillator Lateral light dispersion which decreases spatial resolution This is not an issue with direct using photoconductor amorphous selenium

Answer 151

Nearly 100% (compared to indirect) This is more efficient and means higher DQE

Answer 152

Mo concentration/breakthrough at the time of ADMINISTRATION (not elution). Must assay Mo first with dose calibrator and lead shield 0.15 microCi of Mo per 1 milliCi Tc

Answer 153

Uptake in stomach, salivary gland, lingual, thyroid

Answer 154

* Using pulsed fluoroscopy with low frame rates * Minimizing electronic magnification * Collimating the beam * Minimizing fluoroscopy time * Shortening the distance between the patient and the image receptor

Answer 155

* Using multiple gantry angles * Maximizing the distance between the patient and the x-ray source

Answer 156

[pulsed fluoroscopy with low frame rates]

Answer 157

[Use pulsed fluoroscopy with low frame rates]

Answer 158

[x-ray source]

Answer 159

* Collimating the beam

Answer 160

[To limit patient exposure to radiation]

Answer 161

Efficacy is defined as test performance under ideal conditions. ## Footnote This refers to the maximum possible effect of a treatment in controlled settings.

Answer 162

Effectiveness is considered test performance under usual conditions. ## Footnote This reflects how well a treatment performs in real-world scenarios.

Answer 163

Efficiency is producing a result with a minimum of waste and cost. ## Footnote This concept emphasizes optimizing resources to achieve the desired outcome.

Answer 164

Evidence-based medicine is integrated research evidence with clinical expertise and patient values. ## Footnote This approach aims to improve patient care through the use of the best available evidence.

Answer 165

radiation that extends beyond the active detector area decreases overbearing

Answer 166

extra rotation which extends beyond planned length on spiral/helical scans increases overhanging

Answer 167

stuff that doesn't contribute to the image quantum mottle (not enough photons) and scatter

Answer 168

quadruple the photon flux (mA) to double the SNR

Answer 169

higher mA (but not 1:1), longer rotation time (s), higher kVp, larger slice thickness, larger pixel, decreased pitch

Answer 170

Increases spatial resolution and noise

Answer 171

can correct for noise and allow for lower dose protocols

Answer 172

Wave of energy that does not require a media to travel in (like in vacuum) ## Footnote Velocity is fixed at 3 x 10^8

Answer 173

Velocity = frequency x wavelength

Answer 174

Energy = frequency x h, where h is a constant

Answer 175

* Radiowaves * Microwaves * Infrared * Visible light * UV * X-ray/gamma ray

Answer 176

NON ionizing radiation

Answer 177

The ability to remove electrons from an atom

Answer 178

The wave gets more energetic

Answer 179

Photon with energy >15 eV is ionizing

Answer 180

The atom is considered 'ionized'

Answer 181

* X-rays * Gamma rays * Alpha particles * Beta particles

Answer 182

2 protons and 2 neutrons, net charge 2+, cannot travel far or penetrate deep

Answer 183

Electrons emitted from the nucleus, faster and lighter than alpha particles

Answer 184

Long wavelength, low frequency/energy and do not contribute to image, just add dose

Answer 185

Short wavelength, high frequency/energy and are good for imaging

Answer 186

From the interaction between fast-moving electrons and atoms

Answer 187

Gamma rays originate from the nucleus of an atom and are given off as excess energy as the atom decays

Answer 188

Boiling off of electrons due to extreme temperature in the tungsten filament/cathode

Answer 189

High melting point and high atomic number (good thermionic emitter)

Answer 190

Escaped electrons forming a cloud close to the filament, limiting emission of electrons

Answer 191

They lose kinetic energy via excitation, ionization, and radiative loss (bremsstrahlung)

Answer 192

1% converted to X-ray, the rest is lost as heat

Answer 193

A sloped or angled target spreads heat

Answer 194

Where electrons land on the anode

Answer 195

Where X-rays land on the patient, defines the amount of blur

Answer 196

Decreases effective focal spot

Answer 197

Helps the electron beam strike the target in an acceptable size and reduce spatial spreading

Answer 198

Peak kilovoltage, determines the speed of electrons

Answer 199

Radiation released due to the diversion of bombarding electrons interacting with the entire atom

Answer 200

Radiation that depends on the binding energy of the shell and carries exact and discrete energies

Answer 201

Ejection of an outer shell electron after energy imparted to it from filling inner shell vacancy

Answer 202

The more bremsstrahlung X-rays produced (quantity)

Answer 203

Max X-ray energy is equal to original electron kVp

Answer 204

Average X-ray energy increases (change in quality)

Answer 205

Number of X-rays multiplied by the energy (roentgens per min)

Answer 206

Current of the tube: quantity of electrons moving from cathode to anode

Answer 207

Increases the quantity of X-rays produced, not the quality

Answer 208

Variation/spectrum in beam intensity, strongest beam closest to the cathode

Answer 209

2.5 mm aluminum

Answer 210

Overall energy of the beam, ability to penetrate an object

Answer 211

Total number of X-rays

Answer 212

Decreases quantity, increases quality (average energy)

Answer 213

Probability of photoelectric interaction is directly proportional to atomic number cubed (Z^3)

Answer 214

Peak of photon energy around binding energy for the K shell

Answer 215

Select kVp around 2-3x contrast agent K edge

Answer 216

Compton scatter

Answer 217

Compton scatter

Answer 218

X-ray strikes inner shell electron, removes it from orbit, and is completely absorbed

Answer 219

Incident photon energy cubed (1/E^3)

Answer 220

Less kVp increases photoelectric interactions

Answer 221

More photoelectric interactions result in more dose

Answer 222

Maximum/peak energy of electron stream

Answer 223

Maximum x-ray energy will increase to match

Answer 224

Average x-ray energy will increase (change in quality)

Answer 225

Total number of x-rays produced will increase (change in quantity)

Answer 226

Beam intensity increases as square of kVp

Answer 227

Max energy matches kVp

Answer 228

Average energy is ⅓ to ½ max energy

Answer 229

Lose characteristic peaks

Answer 230

The number of moving electrons

Answer 231

The number of electrons per amount of time

Answer 232

Quantity of x-rays increases

Answer 233

Increase mA

Answer 234

Single sine wave voltage

Answer 235

Spectrum of energies (polyenergetic beam)

Answer 236

More ripple = less quantity and quality

Answer 237

More uniform peak energy (monoenergetic beam)

Answer 238

Less ripple = more quantity and quality

Answer 239

Limited by kVp

Answer 240

Amount of material required to attenuate x-ray to half original output

Answer 241

Higher average photon energy = more penetrating, higher HVL

Answer 242

Lower energy photons removed first

Answer 243

Increases average photon energy as remaining photons are higher energy

Answer 244

* Beam filtration * Anode material * kVp * Wide beam

Answer 245

Does not depend on mAs

Answer 246

* Increased HVL and average energy (increase quality) * Decreased amount of x-rays (decrease quantity)

Answer 247

Increase mAs -> increase quantity

Answer 248

Increase quantity and quality (increased avg and maximum energy)

Answer 249

Increase quantity and quality (increased avg energy)

Answer 250

* Increase Z -> increase quantity (brem x-rays) * Change/increase characteristic x-ray peaks

Answer 251

* Decrease quantity * Increase quality (avg energy)

Answer 252

Focal spot blooming/wider spot

Answer 253

Focal spot thinning/smaller spot

Answer 254

Scatter from anode outside focal area ## Footnote Results in increased patient exposure and blurring

Answer 255

Using a lead collimator near output

Answer 256

X-rays transmitted through housing

Answer 257

X-rays deflected once they leave the tube

Answer 258

Total of leakage and scatter

Answer 259

From electron interaction with materials other than target

Answer 260

Restricting size and shape of X-ray beam

Answer 261

* Reduces primary radiation * Reduces secondary radiation * Improves image quality

Answer 262

Transmission measurements made at two different photon energies

Answer 263

Bone blocks low energy, soft tissue lets both through

Answer 264

X-ray strikes orbital electron and bounces off, changing direction

Answer 265

Does not result in ionization, net transfer of energy, or contribute to image

Answer 266

X-ray strikes outer shell orbital electron, removing it and ionizing the atom

Answer 267

* Results in fog * Causes ionization * Increases dose

Answer 268

Occurs at all energies, but decreased probability with higher energies

Answer 269

Compton scatter

Answer 270

Compton scatter

Answer 271

No, it does not depend on Z

Answer 272

Density of material; hydrogen-rich materials have increased probability

Answer 273

An X-ray strikes an inner shell electron and removes it from orbit, resulting in a photoelectron, and the X-ray is completely absorbed. ## Footnote This interaction is characterized by the absorption of the X-ray photon and the ejection of an inner shell electron.

Answer 274

It emits either an X-ray or an Auger electron, with Auger electrons dominating in biological tissue compared to tungsten. ## Footnote Auger electrons can lead to damage from free electrons in biological tissues.

Answer 275

20-120 keV, with a dominance at lower energy. ## Footnote This range is typical for diagnostic imaging.

Answer 276

Characteristic radiation, a photoelectron, and a positive ion. ## Footnote Characteristic radiation contributes to image contrast in X-ray imaging.

Answer 277

It depends on photon energy and the atomic number of the absorber. ## Footnote Higher photon energy and atomic number increase the likelihood of interactions.

Answer 278

It is the minimum amount needed to free a K shell electron. ## Footnote This is related to the binding energy of the electron.

Answer 279

Inversely proportional to the cube of the incident photon energy (1/E^3). ## Footnote Higher photon energy results in a significant drop in interaction probability.

Answer 280

Directly proportional to the cube of the atomic number (Z^3). ## Footnote Tighter bound K electrons in higher atomic number materials are more likely to undergo interactions.

Answer 281

More photoelectric effect leads to more contrast. ## Footnote This is due to differences in absorption rates among various tissues.

Answer 282

incident photon energy ## Footnote This principle highlights how increased photon energy reduces the likelihood of interaction.

Answer 283

atomic number ## Footnote This indicates that materials with higher atomic numbers have a greater likelihood of engaging in photoelectric interactions.

Answer 284

PE interaction due to the incident x-ray that is absorbed ## Footnote PE stands for Photoelectric Effect, which is a common interaction between x-rays and matter.

Answer 285

More PE, more dose ## Footnote This indicates that an increase in photoelectric interactions leads to a higher radiation dose to the patient.

Answer 286

More PE, more contrast ## Footnote Higher photoelectric interaction results in better image contrast in radiological images.

Answer 287

Less kVp, more PE ## Footnote Lower kilovolt peak (kVp) settings increase the likelihood of photoelectric interactions.

Answer 288

More kVp, less PE ## Footnote Higher kVp settings reduce the probability of photoelectric interactions.

Answer 289

Peak of photon energy around binding energy for the k shell/inner shell ## Footnote The K edge is significant in radiology as it influences the choice of kVp when using contrast agents.

Answer 290

kVp around 2-3x contrast agent K edge ## Footnote This selection is based on the average energy of the majority of photons being lower than the peak.

Answer 291

Difference between x-rays that are absorbed or pass right through ## Footnote This concept is crucial for understanding how different tissues interact with x-rays.

Answer 292

X-rays pass through and reach imaging receptor ## Footnote Transmission is essential for the formation of images in radiographic techniques.

Answer 293

X-rays are attenuated by body and don’t reach imaging receptor ## Footnote Absorption contributes to the contrast seen in radiographic images.

Answer 294

PE contributes to image, Compton degrades image ## Footnote Both processes deposit energy in the patient and attenuate the beam.

Answer 295

* Higher atomic number * Increased tissue density * kVp closer to K edge ## Footnote These factors enhance absorption and decrease transmission.

Answer 296

Increases attenuation, decreases penetration ## Footnote This is due to more interactions between x-rays and electrons in the material.

Answer 297

Increases PE and Compton ## Footnote More electrons in the tissue lead to higher interactions.

Answer 298

Increased attenuation ## Footnote Low kVp enhances the likelihood of photoelectric interactions.

Answer 299

Lower attenuation ## Footnote Higher energy x-rays are less likely to be absorbed.

Answer 300

30 keV ## Footnote This is a critical point for understanding x-ray interactions with matter.

Answer 301

Increased probability of PE at lower keV ## Footnote Conversely, Compton scattering probability increases at higher keV.

Answer 302

Increased attenuation, decreased penetration ## Footnote This is fundamental in determining the quality of images produced.

Answer 303

Linear relationship of x-ray and attenuating substance ## Footnote Beer's law describes how the intensity of x-ray radiation decreases as it passes through an attenuating material.

Answer 304

Fraction of photons interacting per gram of tissue ## Footnote Mass attenuation is a measure of how much x-ray photons are absorbed or scattered by a material.

Answer 305

Mass = density x volume ## Footnote Mass is the amount of matter an object contains, calculated by multiplying its density by its volume.

Answer 306

Probability of a material to attenuate x-ray beam over a set distance ## Footnote The linear attenuation coefficient indicates how easily a material can reduce the intensity of x-ray radiation.

Answer 307

Affected by density of material ## Footnote The linear attenuation coefficient is influenced by the density of the material through which the x-ray beam passes.

Answer 308

Rate of energy loss by x-ray beam as it travels through a material ## Footnote The mass attenuation coefficient helps to understand how much energy from the x-ray beam is lost in a given material.

Answer 309

Depends on atomic number and photon energy ## Footnote The mass attenuation coefficient is influenced by the atomic structure of the material and the energy of the incoming photons.

Answer 310

Mass attenuation coefficient = Linear attenuation coefficient / Density ## Footnote This relationship shows how the mass attenuation coefficient is derived from the linear attenuation coefficient adjusted for material density.

Answer 311

Radiation absorbed by skin ## Footnote The ESD is a critical measurement in radiology to determine the amount of radiation exposure to the skin.

Answer 312

* Tube current (mA): proportional * Time of exposure (s): proportional * Peak kilovoltage (kVp): square ## Footnote These factors collectively influence the amount of radiation absorbed by the skin during an x-ray procedure.

Answer 313

More kVp = more penetration (decreased attenuation) ## Footnote Higher kVp allows x-rays to penetrate tissues more effectively, resulting in lower attenuation.

Answer 314

Occurs as function of number of photons hitting imaging receptor ## Footnote Noise refers to the random variations in the imaging signal, which can obscure the desired image quality.

Answer 315

More photons = more signal to noise ## Footnote Increasing the number of x-ray photons reaching the imaging receptor helps to improve the signal quality relative to noise.

Answer 316

Noisy image because not enough x-rays reach film/detector ## Footnote Quantum mottle is a specific type of noise resulting from insufficient x-ray exposure, leading to a grainy image.

Answer 317

* More x-ray (mAs) * More efficient detection ## Footnote Increasing the milliampere-seconds (mAs) or improving detection efficiency can mitigate quantum mottle in imaging.

Answer 318

Mostly Compton interactions ## Footnote Scatter refers to the deflection of x-ray photons as they interact with matter, primarily through Compton scattering.

Answer 319

* kVp: higher kVp, more Compton scatter * Thickness: thicker body part has more scatter interactions * Field of view: smaller FOV decreases Compton scatter ## Footnote These factors influence the amount of scatter radiation produced during imaging.

Answer 320

Collimation decreases noise (scatter) although lower signal to noise, so mAs is increased ## Footnote Collimation helps focus the x-ray beam, reducing scatter but may require increased exposure to maintain image quality.

Answer 321

Improves contrast by reducing scatter ## Footnote Grids are used to enhance image quality by filtering out scattered x-rays that would otherwise decrease contrast.

Answer 322

Increases dose/mA ## Footnote While grids improve image contrast, they generally require a higher radiation dose to maintain image quality.

Answer 323

How dense grid is, height to distance between lead strips ## Footnote Grid ratio is an important specification that affects the efficiency of scatter reduction in imaging.

Answer 324

Moving grids to reduce grid lines ## Footnote Bucky grids are designed to move during exposure to prevent the appearance of grid lines on the final image.

Answer 325

Risk of using grid ## Footnote Grid cutoff occurs when too many x-rays are blocked by an improperly aligned grid, leading to poor image quality.

Answer 326

* Grid incorrectly aligned * Upside down * Wrong distance * Off center ## Footnote These alignment issues can lead to significant artifacts in the image due to inadequate x-ray exposure.

Answer 327

Separate patient from receptor (film) to reduce scatter ## Footnote This technique can effectively reduce scatter radiation without the need for a grid.

Answer 328

How dark film is ## Footnote Radiographic density is an important aspect of film interpretation, where darker films indicate higher exposure to x-rays.

Answer 329

More x-rays = darker film = increased radiographic density ## Footnote Increased exposure to x-rays results in a darker image on the film, indicating higher radiographic density.

Answer 330

Decreases quantum mottle ## Footnote Quantum mottle occurs due to insufficient mAs.

Answer 331

Loss of contrast ## Footnote Increased kVp leads to increased scatter radiation.

Answer 332

Energy twice as far from source is ¼ the intensity.

Answer 333

Noise increases.

Answer 334

Cuts mottle in half.

Answer 335

How visibility of finding is affected.

Answer 336

By increasing mA.

Answer 337

How close two lines can be to one another and still visibly resolved.

Answer 338

Loss of spatial resolution.

Answer 339

Patient motion.

Answer 340

Detector size limiting factors.

Answer 341

Focal spot size.

Answer 342

Less blur.

Answer 343

More magnification, more blur.

Answer 344

Source to image distance.

Answer 345

Source to object distance.

Answer 346

More pixels per unit area, better spatial resolution.

Answer 347

Measurement from center of one pixel to the next.

Answer 348

* Pixel size * Pixel pitch

Answer 349

Increased pixel density + decreased pixel pitch = better spatial resolution.

Answer 350

Information recorded/information available.

Answer 351

The dose required for optimal image creation.

Answer 352

By comparing image noise of a detector to that of an ideal detector.

Answer 353

Not efficient, high dose, high spatial resolution.

Answer 354

Efficient, low dose, low spatial resolution.

Answer 355

DQE is directly proportional to MTF and inversely proportional to SNR.

Answer 356

Compton LAC = density/energy ## Footnote This formula relates the linear attenuation coefficient to the density of the material and the energy of the incident x-rays.

Answer 357

PE LAC = density x atomic number^3/energy ## Footnote This formula shows how the photoelectric linear attenuation coefficient is influenced by the density and atomic number of the material.

Answer 358

* Decreasing energy (kVp) * Increasing density * Increasing atomic number ## Footnote These adjustments help enhance the visual contrast in radiographic images.

Answer 359

mA ## Footnote Longer exposure times necessitate a reduction in milliampere (mA) to avoid overheating the equipment.

Answer 360

Uses cesium iodine as scintillator to convert x-rays to light, then back to electrons, amplifying electron flux and energy ## Footnote This process enhances the brightness and clarity of the resulting image.

Answer 361

* Input phosphor * Focusing electrode * Output phosphor ## Footnote These components help focus the electron beam and convert light back into an image.

Answer 362

X-rays converted to light are then converted to electrons by the photocathode ## Footnote This is the initial step in the process of image intensification.

Answer 363

The combined effects of flux gain and minification gain ## Footnote It indicates how much brighter the output image is compared to the input.

Answer 364

Increase in magnitude of light from output phosphor relative to input, accomplished with higher voltage ## Footnote This gain increases the brightness of the output image.

Answer 365

Concentration of electrons from large photocathode to small output phosphor ## Footnote This process increases electron density and thus energy per unit area, enhancing brightness.

Answer 366

Deteriorates with age, requiring more dose to produce the same level of output brightness ## Footnote This means older tubes are less efficient at converting input to output brightness.

Answer 367

Moving object closer to focal spot improves spatial resolution but increases blur ## Footnote This principle highlights the trade-off between resolution and image clarity.

Answer 368

Relationship between intrinsic receptor resolution and focal spot size ## Footnote A higher R/F ratio signifies better resolution in the image.

Answer 369

Magnification will increase sharpness ## Footnote This indicates that higher ratios enhance image quality.

Answer 370

R/F < 0.5 ## Footnote This ratio suggests that magnification decreases resolution in general radiography.

Answer 371

R/F > 0.5 ## Footnote In mammography, a higher ratio allows for increased resolution through magnification.

Answer 372

* Larger field of view = more minification (less mag) = more brightness * Smaller field of view = less minification (more mag) = less brightness ## Footnote This relationship is crucial for optimizing imaging techniques.

Answer 373

Lower energy/monoenergetic beam and spatial resolution ## Footnote Ideal energy for mammography is 20 keV

Answer 374

25 kVP ## Footnote In comparison, x-ray typically uses 50 kVP

Answer 375

Molybdenum or rhodium ## Footnote They require lower energy due to binding energies of 18 keV and 20 keV

Answer 376

Molybdenum: 20 keV, Rhodium: 21 keV ## Footnote These edges filter the energies above and below the K edge

Answer 377

Beryllium window ## Footnote This is due to the low energy requirements in mammography

Answer 378

* More uniform tissue * Less tissue overlap * Less blur * Less dose * Less scatter * Improved spatial resolution * Improved contrast ## Footnote Compression also leads to lower inherent scatter in mammography

Answer 379

Improves spatial resolution ## Footnote Smaller focal spots (0.1-0.3 mm) tolerate heat less well, requiring lower mA and increased exposure time

Answer 380

Density of x-rays per unit space ## Footnote It decreases as you move away from the source and obeys the inverse square law

Answer 381

Decreases effects of tissue superimposition ## Footnote This improves the clarity of mammograms

Answer 382

Every 3 years ## Footnote This is overseen by the FDA under MQSA

Answer 383

3 megapixels ## Footnote This ensures adequate image resolution for interpretation

Answer 384

Interpreting physician ## Footnote This includes daily, weekly, quarterly, and semi-annual QC tasks

Answer 385

3 mGy with grid, 1 mGy without grid ## Footnote This is important for patient safety

Answer 386

Anode angle plus tube tilt ## Footnote This affects the geometry of the x-ray beam

Answer 387

False ## Footnote A grid reduces scatter and increases contrast but requires an increased dose

Answer 388

K edge filter ## Footnote Molybdenum and rhodium are commonly used for this purpose

Answer 389

Operates at very high tube currents and reasonable voltages ## Footnote Tungsten alloy targets are common in X-ray generation due to their high atomic number and thermal conductivity.

Answer 390

Remove X-rays that only contribute dose ## Footnote Filters help reduce patient exposure by ensuring that only useful X-ray energies are used.

Answer 391

Reduces dose and higher average energy ## Footnote A monochromatic beam minimizes beam hardening within the patient.

Answer 392

Attenuate less centrally and more along the edges ## Footnote This compensates for uneven attenuation of the beam by the patient.

Answer 393

Shapes the X-ray beam ## Footnote Collimation is applied both at the X-ray tube and at the detector.

Answer 394

Pre-patient restricts scatter and lowers dose; pre-detector shapes attenuated beam and removes scatter ## Footnote Both types of collimation are essential for optimizing image quality and patient safety.

Answer 395

Defines slice thickness directly ## Footnote In multi-slice CT, the slice thickness is determined by the width of the detector rows.

Answer 396

Filter scatter ## Footnote Septa help improve image quality by reducing scattered radiation.

Answer 397

Central row of detectors is more narrow than outer rows ## Footnote This design helps improve spatial resolution.

Answer 398

Convert X-rays into visible light photons, then into electrical signal ## Footnote Solid state detectors enhance image quality and sensitivity.

Answer 399

Axial and helical ## Footnote Each method has different advantages in terms of speed and image quality.

Answer 400

Stop and go method, better spatial resolution in z dimension, less partial volume artifact ## Footnote Axial scanning provides high-quality images but is slower compared to helical scanning.

Answer 401

Constant continuous spiral, faster, less motion artifact, better reconstruction ## Footnote Helical scanning allows for overlapping images, which reduces stair step artifacts.

Answer 402

Table movement/beam width ## Footnote Pitch affects spatial resolution and dose.

Answer 403

Table moves fast, with gap between slices, decreasing spatial resolution and dose ## Footnote This can lead to less detailed images.

Answer 404

Table moves slow, overlapping slices, increasing spatial resolution and dose ## Footnote Overlapping slices improve image quality but increase patient exposure.

Answer 405

Calculate value of attenuation for each pixel along a ray ## Footnote Back projection is a fundamental step in image reconstruction.

Answer 406

Filter applied prior to calculating back projection ## Footnote This technique enhances image quality by reducing artifacts.

Answer 407

Can correct for noise and can use a lower dose ## Footnote This technique improves image quality while minimizing radiation exposure.

Answer 408

Tradeoff between noise and spatial resolution ## Footnote Selecting the appropriate kernel is crucial for achieving the desired image quality.

Answer 409

Radiodensity of tissues ## Footnote HU values help differentiate between various types of tissues in the body.

Answer 410

As photon energy decreases, positive HU becomes more positive, negative HU becomes more negative ## Footnote This relationship is important in understanding tissue contrast.

Answer 411

Level is midpoint, width is range above and below ## Footnote Adjusting window width and level is essential for visualizing different tissue densities.

Answer 412

Decreased contrast and increased noise ## Footnote High KVP is often used to mitigate metal artifacts.

Answer 413

Decreases as you increase detector rows and beam width ## Footnote Overbeaming can lead to unnecessary radiation exposure.

Answer 414

Extension beyond subject, only with helical scans ## Footnote Overranging can increase radiation dose as it includes areas outside the intended scan region.

Answer 415

Decreases with increased number of slices acquired simultaneously ## Footnote Wider beams help minimize the overbeaming effect.

Answer 416

the number of photons that land on the detector, which has uniform detector efficiency, and is recorded successfully approximated by mA

Answer 417

less relative noise, more SNR, but also more absolute noise)

Answer 418

tight collimation (pre patient and pre detector) and tight windowing

Answer 419

large focal spot and detector size

Answer 420

small focal spot size, decreased magnification, more projections, sharp filter (tradeoff of more noise), smaller pixel size (increased matrix size or decreasing display field of view)

Answer 421

increases spatial resolution in the z axis only (x-y axis is NOT affected by detector aperture size)

Answer 422

increased spatial resolution but decreased contrast resolution decreased spatial resolution but improved contrast resolution

Answer 423

Field of view/matrix size

Answer 424

2 tubes and 2 detectors offset by 90 degrees Decrease mottle where fields overlap, faster, and higher pitch

Answer 425

Need slow regular heart rate to trigger capture ## Footnote This ensures effective synchronization with the heart cycle.

Answer 426

Susceptible to motion artifact ## Footnote Motion artifacts can affect image quality, leading to inaccurate results.

Answer 427

Reduced radiation ## Footnote This method typically involves lower radiation exposure compared to other techniques.

Answer 428

No functional imaging ## Footnote This method focuses on capturing images without assessing heart function.

Answer 429

Always axial ## Footnote Axial imaging captures images in a slice format, perpendicular to the axis of the body.

Answer 430

Scan continuously and back calculates ## Footnote This approach allows for the acquisition of data throughout the entire heart cycle.

Answer 431

Higher radiation ## Footnote Continuous scanning increases radiation exposure to the patient.

Answer 432

Can do functional imaging ## Footnote This method provides the ability to assess the function of the heart.

Answer 433

Always helical ## Footnote Helical imaging provides continuous data acquisition in a spiral path.

Answer 434

Bradycardia, systolic hypotension, cardiac failure, beta agonist meds (albuterol), severe COPD, AV heart block ## Footnote Metoprolol is a beta-blocker used primarily for cardiovascular conditions.

Answer 435

Sildenafil (PDE inhibitor) 48 hrs before exam, severe aortic stenosis, hypertrophic cardiomyopathy ## Footnote Nitroglycerine is used to treat angina and other heart-related conditions.

Answer 436

Sildenafil (PDE inhibitor)

Answer 437

25 mGy ## Footnote ACR stands for American College of Radiology

Answer 438

20 mGy ## Footnote Pediatric patients may have different dose limits due to their developing bodies

Answer 439

75 mGy ## Footnote Head CT typically has a higher dose limit due to the complexity of imaging

Answer 440

is 1/3 central CTDI + 2/3 peripheral CTDI

Answer 441

divide weighted CTDI by pitch unit is mGy

Answer 442

DLP= CTDI vol x distance of scan in cm unit is mGy*cm

Answer 443

DLP x k k is a constant, predetermined for a specific body part (takes into consideration radiation sensitivity of the tissue) unit is Sv

Answer 444

if patient is larger than phantom, CTDI vol is overestimated if patient is smaller than phantom, CTDI vol is underestimated

Answer 445

double mA-> doubles CTDI, DLP, and effective dose double kVp-> quadruples CTDI, DLP, and effective dose double pitch-> halves CTDI, DLP, and effective dose double rotation time-> doubles CTDI, DLP, and effective dose

Answer 446

CTDI weighted divided by pitch-> CTDI volume CTDI volume adjusted for scan distance-> DLP DLP adjusted for organ sensitivity-> effective dose

Answer 447

500 mrem; mandated monitoring if occupational dose expected to exceed 10% of this

Answer 448

lower energy photons are removed preferentially as X-ray beam passes through an object results in cupping and dark bands/streak artifact can be corrected with filtration to pre harden beam, calibration correction, correction software, or avoidance

Answer 449

hardened X-rays passing through middle of uniform shape compared to periphery results in darker center of image (harder beam=less attenuated)

Answer 450

X-rays passing through two dense objects results in bands/streaks between

Answer 451

dense object protrudes into X-ray and results in divergence of beam, resulting in shading artifacts adjacent to the object volume averaging within voxel resulting in intermediate density thinner slices to fix partial volume effect

Answer 452

when beam travels horizontally through high attenuating area results in streaking use automatic tube current modulation (increase dose through the area/add photons to overcome) or adaptive filtration (smoothes the data)

Answer 453

insufficient number of projections used to reconstruct the CT result in view aliasing (under sampling between projections) and ray aliasing (under sampling within a projection) seen as stripes radiating from object

Answer 454

streak artifact through several mechanisms seen more with high Z metals increase kVp and use thinner slices

Answer 455

extremities outside the field but still attenuating X-ray

Answer 456

calibration error or defective detector due to errors in angular position

Answer 457

typically where anatomy changes rapidly in the Z direction (skull), worse with higher pitch

Answer 458

seen at edge of multiplanar reformatted image with wide collocation of non overlapping intervals improved on helical scanner and thin slices

Answer 459

impedance and angle

Answer 460

mechanical energy producing vibrations which result in areas of compression (high pressure) and rarefaction (low pressure)

Answer 461

thought of as constant in particular medium equals wavelength x frequency (distance between areas of compression) x (rate of change between compression and rarefaction, how many oscillations through cycle)

Answer 462

represents a 50% loss of signal intensity (power) thickness that reduces ultrasound intensity by 3 dB

Answer 463

reflected at boundary between tissues with differences in acoustic impedance (defined as degree of stiffness; density x speed of sound) large difference in impedance results in large reflection

Answer 464

change in direction of ultrasound energy when beam is not perpendicular to boundary

Answer 465

non specular reflector results in scatter, especially with higher frequencies as smaller wavelength makes surface look rougher

Answer 466

reflect with return echo strength dependent on angle of incidence independent of frequency

Answer 467

HVT decreases (thickness required to attenuate the incident intensity by 50% higher frequency= more attenuation= superficial structure lower frequency= deeper structures

Answer 468

impedance and angle

Answer 469

changes depending on compressibility of tissue (slow in air, fast in bone)

Answer 470

determined by probe crystal material (thick crystal produces lower frequency and thin crystal produces higher frequency) wavelength changes to accommodate changing velocity in different media

Answer 471

high Q, long spatial pulse length, and narrow bandwidth

Answer 472

low Q, short spatial pulse length, and wide bandwidth

Answer 473

interface between transducer and tissue, minimizes acoustic impedance differences

Answer 474

linear: multiple individual elements firing and receiving independently (good for superficial things) curvilinear: scan lines diverge deeper into image (wider field of view, abdominal imaging)

Answer 475

elements activated and reactivated in phased pattern, using interference patterns to steer the beam small probe good for transvaginal, between ribs

Answer 476

converging beam increased transducer frequency and diameter

Answer 477

diverging beam power is greatest along the centerline, with decreased power "beam spread" outwards

Answer 478

spot between converting and diverging beams where beam is narrowest and maximum intensity best echoes and lateral resolution at this spot

Answer 479

number of cycles emitted per pulse by transducer x wavelength minimum of 1/2 spatial pulse length is required for separation between reflectors to resolve two closely spaced objects in the axial plane

Answer 480

ability to resolve objects in direction perpendicular to beam best at focal zone and improves with higher frequency because this narrows the beam; improves with higher scan line density

Answer 481

axial: smaller spatial pulse length lateral: focusing to focal zone or applying optical lens elevation: thinner crystal, minimize slice thickness

Answer 482

axial: spatial pulse length lateral: transducer element width elevation: transducer element height

Answer 483

strong reflector within low energy side lobe which reflects back to transducer as within the beam

Answer 484

-strong reflector located outside main US beam generates scatter detectable from the transducer -seen as peripheral echoes in a cystic structure -adjust focal zone and place transducer at the center of the image

Answer 485

two parallel highly reflective surfaces reflect echo back and forth before returning to transducer seen as multiple parallel reflections

Answer 486

reverberation but reflective surfaces are less than 1/2 spatial pulse length seen as triangle echo

Answer 487

beam encounters gas or air bubbles which vibrate and cause parallel echogenic bands

Answer 488

beam encounters a highly reflective surface which reflects object back onto reflective surface

Answer 489

assumed to be 1540 m/s if tissue slows speed, takes longer to return to transducer, and perceived as deeper

Answer 490

speed difference in tissues causes refraction, can duplicate or misplace object

Answer 491

echoes returning later are amplified more than echoes that return earlier to create a more uniform image

Answer 492

if ultrasound beam goes through material that attenuates sound more-> posterior shadowing if beam goes through material that attenuates sound less-> increased through transmission, brighter

Answer 493

less than 90 ideally 30-60 degrees

Answer 494

doppler angle is not as important since info is quantitative spatial resolution is worse than gray scale

Answer 495

very sensitive to flow without direction, does NOT exhibit aliasing NO dependence on doppler angle

Answer 496

when doppler shift is greater than nyquist frequency decrease doppler shift (lower frequency transducer or increase angle) increase pulse repetition frequency (increase scale)

Answer 497

-turbulent blood flow like AVF in kidney -most sensitive for stones with rough surface -ureteral jets flowing -burst of color filling screen due to motion; fetal kick

Answer 498

output power: increases brightness of sound sent to body (degrades lateral resolution) receiver gain: increases brightness after returns to the transducer (like post processing)

Answer 499

change in shape of the fundamental compression/rarefaction wave as it travels through tissue; generated in the deep tissue as it takes time to morph the wave transmit at one frequency and receive at another

Answer 500

improved lateral resolution (at expense of axial resolution), filter out grating lobe artifacts, reduce superficial reverberation artifact can make things appear more anechoic (turn solid cystic)

Answer 501

images object in multiple directions sharpens edges but loses posterior shadowing

Answer 502

intensity= power/area M mode (motion) and doppler decrease area and increase intensity

Answer 503

sonically generated activity of gas/vapor can be transient or stable and is measured by mechanical index (MI) most likely to occur at low frequency and high pressure

Answer 504

photons emitted from radionuclide-> collimator-> scintillation crystal-> photomultiplier tube-> pulse height analyzer

Answer 505

-decrease scatter -better sensitivity w thick crystal, worse spatial res -spatial resolution/signal intensity -excludes Compton scatter (less effective excluding scatter from a person compared to point source)

Answer 506

lower photon energy tracers should be used first to avoid Compton scatter interfering with pulse height analyzer (ie image with Xe before Tc)

Answer 507

assess uniformity of image extrinsic: with collimator, performed daily intrinsic: performed weekly

Answer 508

assess spatial resolution (differentiate between bars) and image linearity (if bars are straight) performed weekly

Answer 509

-daily to assess correct window prior to each study -monthly to assess axis is straight

Answer 510

ring badge: on dominant hand with label towards palm/source film badge: on collar at chest/neck level

Answer 511

small gamma camera with sodium iodine crystal good for wipe test samples, urine and blood samples

Answer 512

-dose calibrator gas filled chamber which is very sensitive in detecting ionizing radiation -however can be overloaded by very high radiation field resulting in dead time before can work again -does NOT provide information about radiation type

Answer 513

most commonly used dose calibrator/survey meter, used for higher dose rates without dead time

Answer 514

scintillator detector with PMT compares counts from region over thyroid to capsule of same radionuclide

Answer 515

consistency checked daily linearity checked quarterly accuracy performed at installation and checked annually geometry performed at installation and when device is moved

Answer 516

Yes, agreement states can be more strict than the national agency, but not less strict.

Answer 517

Greater than 100 mCi.

Answer 518

Clear the area; cover the spill; indicate boundaries of area; shield source if possible; notify radiation safety officer; decontaminate persons

Answer 519

protect the patient; confine the spill; clean up the spill; survey cleanup items and people

Answer 520

DTPA, MAG3, I123 MIBG, MDP

Answer 521

Sulfur colloid IV, I131 MIBG, In Prostascint

Answer 522

octreotide, heat treated RBCs, In WBCs

Answer 523

gallbladder wall, kidney, stomach, kidney, proximal colon x2, distal colon

Answer 524

positron emission tomography: 2 positrons emitted single photon emission tomography: 1 gamma photon emitted SPECT is not depth dependent and has improved contrast compared to PET

Answer 525

when point source is imaged and there is error of the center of rotation (misregistration error)

Answer 526

too many protons-> emission of positron during conversion of proton to neutron-> positron travels until it meets an electron-> annihilation event creates 2 511 keV photons emitted 180 degrees from each other-> detected by PET scanner

Answer 527

Ratio of true coincidences over total coincidences ## Footnote This is a key metric in evaluating the performance of PET imaging.

Answer 528

Signal to noise ratio ## Footnote This comparison helps in understanding the quality of the imaging signal relative to background noise.

Answer 529

Septa ## Footnote This results in increased sensitivity.

Answer 530

Spatial resolution and image contrast

Answer 531

Localization and attenuation correction

Answer 532

Skin and lung activity

Answer 533

It is overestimated

Answer 534

SUV continues to increase

Answer 535

High glucose level equals lower SUV

Answer 536

Blank scan

Answer 537

A diagonal line

Answer 538

A positron source (Ge or Cs) or a uniform source (cylinder phantom)

Answer 539

radio waves-> microwaves-> visible light-> ultraviolet (ionizing)-> X-rays/gamma rays (ionizing)

Answer 540

precession frequency equals gyromagnetic ratio x field strength precession frequency is directly proportional to field strength (B0)

Answer 541

it is not in the longitudinal phase

Answer 542

the time when longitudinal magnetization is 63% its final value greater the field strength/stronger the magnet, the longer the T1 (things with long T1s are dark)

Answer 543

transverse relaxation, spin spin relaxation, or transverse magnetization decay (when 63% has decayed) T2 is shorter than T1

Answer 544

inhomogeneities in the external field and inhomogeneities in the local magnetic field

Answer 545

Time to repetition ## Footnote TR is the time between two successive RF pulses.

Answer 546

Free induction delay ## Footnote FID is the signal decay created after an RF pulse.

Answer 547

It flips the signal and clears inhomogeneities in the field ## Footnote This process converts T2* into T2 and creates an echo.

Answer 548

Short TR and short TE ## Footnote This maximizes longitudinal contrast and minimizes transverse contrast.

Answer 549

Long TR and long TE ## Footnote This maximizes transverse contrast and minimizes longitudinal contrast.

Answer 550

Long TR and short TE ## Footnote This minimizes longitudinal and transverse contrast, allowing for subtraction of T1 and T2 weighting bias.

Answer 551

Vertical direction ## Footnote Phase encoding is applied vertically in MRI imaging.

Answer 552

Horizontal direction ## Footnote Frequency encoding is applied horizontally in MRI imaging.

Answer 553

Phase encoding ## Footnote Phase encoding is much longer than frequency encoding.

Answer 554

Repetition time x number of phase encoding steps x number of excitations ## Footnote TR repetition time= time between each RF pulse phase matrix= number of phase encoding steps number of excitations

Answer 555

At the time of readout (echo) ## Footnote Frequency encoding occurs during the echo readout phase.

Answer 556

SSG selective pulse is applied with the 90 degree RF pulse ## Footnote This process helps define the slice of the body being imaged.

Answer 557

After the slice selection Additional frequency encoding gradient is applied at the readout ## Footnote Gradients are applied following the initial pulse to encode the signal.

Answer 558

At 1/2 TE ## Footnote This pulse is applied along with two identical SSG selective pulses.

Answer 559

Additional frequency encoding gradient is applied at the same time as the readout echo ## Footnote This step finalizes the encoding process for the image data.

Answer 560

Steeper/larger gradient slope and thinner transmit bandwidth ## Footnote This relationship affects the slice selection process in imaging techniques.

Answer 561

Shallow/smaller gradient slope and thicker transmit bandwidth ## Footnote This influences the slice selection in imaging, affecting resolution and bandwidth.

Answer 562

longer TR increases SNR (also increases time) longer TE decreases SNR

Answer 563

small voxel, small field of view, thinner slicers, larger matrix

Answer 564

large voxel, stronger field strength/magnet, long TR, big FOV, large slices (aka large TRANSMIT bandwidth), small RECEIVER bandwidth, small matrix, short TE

Answer 565

90 degree RF pulse and 180 degree refocusing pulse ## Footnote Spin echo sequences are designed to refocus the spins and restore the transverse magnetization.

Answer 566

Less than 90 degree RF pulse and NO refocusing RF pulse ## Footnote Gradient echo sequences are more flexible but can be more susceptible to artifacts.

Answer 567

Reduce the TR ## Footnote Fast spin echo uses multiple 180-degree RF pulses to produce several echoes.

Answer 568

Intrinsic shortening of T2 signal ## Footnote J coupling can affect the relaxation times of certain molecules, impacting image quality.

Answer 569

180 degree RF preparation pulse ## Footnote This is followed by a 90 degree pulse to suppress certain substances.

Answer 570

Fat ## Footnote STIR is particularly useful in imaging scenarios where fat suppression is necessary.

Answer 571

CSF ## Footnote FLAIR sequences are useful in visualizing lesions near cerebrospinal fluid.

Answer 572

Less susceptible to metal artifact and field inhomogeneity ## Footnote This makes STIR sequences more reliable in certain imaging environments.

Answer 573

It will null the contrast enhanced tissue ## Footnote Gadolinium is often used as a contrast agent, and STIR can negate its visibility.

Answer 574

Extra time to inversion (TI) increases TR ## Footnote This increases the overall acquisition time for the sequence.

Answer 575

Considered T2* (not T2), and more susceptible to susceptibility artifacts ## Footnote This distinction affects the interpretation of the images produced.

Answer 576

Spin echo or gradient echo ## Footnote EPI is commonly used for diffusion-weighted imaging (DWI).

Answer 577

Highly vulnerable to magnetic susceptibility ## Footnote This can lead to image distortions and artifacts.

Answer 578

Interferes with J coupling, causes T2 signal of fat to increase ## Footnote This can complicate the interpretation of fat-suppressed images.

Answer 579

The number of echoes in the same TR ## Footnote ETL is an important factor in determining the efficiency and speed of the imaging sequence.

Answer 580

Proportional to 1/ETL ## Footnote A higher ETL results in shorter acquisition times.

Answer 581

Gradual decrease in transverse signal with each progressive echo train ## Footnote This phenomenon can affect the clarity and detail of the images produced.

Answer 582

bright rim on one side and dark rim on other occurs in the FREQUENCY encoding direction can be seen with spin echo or gradient echo sequences

Answer 583

intracytoplasmic/microscopic fat mix of fat and water per voxel

Answer 584

outlines fat water interface (macroscopic fat) only on gradient echo sequences. using spin echo sequences fixes this artifact

Answer 585

magnevist=gadopentetate=Gd DTPA (highest risk of NSF) eovist=gadoxetate=Gd EOB DTPA (50% liver uptake) multihance=gadobenate=Gd BOPTA gadavist=gadobutrol=Gd BT DO3A

Answer 586

worsens with greater field strength improves with increased gradient strength and wider receiver bandwidth

Answer 587

ripples in data at high contrast interfaces (like 'syrinx' in spine) improve with increased matrix

Answer 588

only in short echo time (TE) sequences where focus forms angle of 55 degrees with magnetic field

Answer 589

seen in the setting of metal, can use STIR to improve

Answer 590

shimming, passive and active

Answer 591

worse on in phase due to longer TE (longer time) T2* susceptibility effect worsens over time

Answer 592

Aliasing ## Footnote Aliasing is a phenomenon that can distort the image quality in imaging techniques such as MRI.

Answer 593

By increasing FOV ## Footnote FOV stands for Field of View, which is the extent of the observable world that can be seen at any given moment.

Answer 594

distortion/smear/stretch occurs when gradients are rapidly turned on and off

Answer 595

dark signal worse with stronger magnet or pt with ascites

Answer 596

It changes the frequency ## Footnote This change occurs during the active phase of the gradient.

Answer 597

A permanent phase shift is seen ## Footnote This phase shift is noticeable after the frequency has returned to baseline.

Answer 598

Slice selection ## Footnote Slice selection is a fundamental concept in MRI that involves choosing a specific slice of the patient's anatomy for imaging.

Answer 599

To be the shortest distance to minimize imaging time ## Footnote This selection helps optimize the efficiency of the imaging process.

Answer 600

Frequency matrix ## Footnote The frequency matrix is crucial for defining the resolution and detail of the acquired images.

Answer 601

Wider waveform, longer sampling time, more chemical shift ## Footnote A narrow receiver bandwidth can lead to increased chemical shift artifacts, affecting image quality.

Answer 602

Narrow waveform, increased frequency, shorter sampling time, worse SNR ## Footnote A wider receiver bandwidth can improve the speed of acquisition but may compromise signal-to-noise ratio (SNR).

Answer 603

More patient movement, flow artifact, susceptibility/metal artifact ## Footnote Longer sampling times increase the likelihood of artifacts in the images due to motion and other factors.

Answer 604

Gradient sequences ## Footnote Bright blood imaging enhances visualization of blood flow in the heart.

Answer 605

Double inversion recovery spin echo sequence ## Footnote This sequence is good for anatomy and less susceptible to artifacts.

Answer 606

Nulls myocardium to look for delayed gadolinium enhancement (scar) ## Footnote This helps identify areas of scar tissue in the heart.

Answer 607

Dynamic post contrast sequences ## Footnote These sequences help in detecting potential tumors in breast tissue.

Answer 608

No ## Footnote Implant rupture screening does not require contrast for effective imaging.

Answer 609

Chemical shift artifact ## Footnote This artifact can be corrected by increasing the receiver bandwidth.

Answer 610

Side to side ## Footnote This approach corrects for motion artifacts caused by cardiac or breathing movements.

Answer 611

Increases SNR but causes artifact on FLAIR if the breast is too close to the coil ## Footnote Signal-to-noise ratio (SNR) is improved, but proximity to the coil can introduce artifacts.

Answer 612

defines parameter for risk to implanted devices DOES NOT indicate translational force

Answer 613

Gradient intensive sequences, including echo planar sequences like diffusion ## Footnote These sequences involve rapid changes in magnetic gradients, resulting in higher noise levels.

Answer 614

140 dB ## Footnote This limit is established to protect patients and staff from excessive noise exposure.

Answer 615

Neurostimulation of the arms and legs ## Footnote Rapid changes in magnetic fields can stimulate peripheral nerves.

Answer 616

SAR = B0^2 × Alpha^2 × Duty Cycle ## Footnote B0 is the strength of the magnet, Alpha is the flip angle, and duty cycle relates to tissue cooling.

Answer 617

SAR quadruples ## Footnote This is because the strength of the magnetic field (B0) doubles, leading to an increase in SAR.

Answer 618

Gradient sequences have a lower flip angle than spin echo sequences ## Footnote Lower flip angles result in lower SAR.

Answer 619

Duty cycle is halved, so SAR is halved ## Footnote TR is the repetition time and affects how often the tissue can cool down.

Answer 620

GFR must be >30 ## Footnote This is due to the risk of nephrogenic systemic fibrosis in patients with lower GFR.

Answer 621

No, dialysis does not necessarily remove gadolinium ## Footnote Gadolinium can remain in the body despite dialysis, posing risks.