Motherload Dx Imaging Final

Which of the following frequencies would include diagnostic ultrasound?

10 MHz

One Tessla is equal to:

10,000 gauss

In general, restriction of the primary beam with cones or collimators requires that the device restrict the beam to an area whose measured dimensions differ form the desired dimensions by no more than.......of SID

2%

The LD of humans is close to:

300 rads

For lung and prostate malignant tumors, a typical course of radiation treatments will result in a cumulative dose of approximately:

7000 rads

Which of the following is not part of the law of Bergonie and Tribondeau (increased tissue metabolic activity, increased tissue radiosensitivity)?

A fetus is less radiosensitive than an adult

A minimal x-ray exam of a body part includes:

AP and lateral views

The 10 day rule states that:

Appropriate x-ray exams should be scheduled within 10 days after the onset of menstruation

What is the depth of the voxel determined by?

Bem

No film ->

CT and MRI

Do x-rays or CT's collimate better?

CT's collimate 2X better than x-rays

What are MRI's really good at?

Contrast resolution AKA soft tissue contrast

Of the various macromolecules sensitive to radiation damage,......is/are considered most sensitive

DNA

Transverse relaxation is also called:

Spin-spin relaxation

A minimal MRI exam of a body part includes:

T1 and T2 weighted images

A CT image matrix is listed at 512 by 512. What does this mean?

The anatomical image is composed of more than 200,000 picture elements

Why is MRI non-ionizing?

The electron-binding force of atoms that make up human tissues is greater than the energies associated with the main magnetic field and the radiofrequencies used in MRI

True or false: Sonography is ideal for imaging lungs due to non-ionizing nature

False

True or false: There is a minimum amount of radiation a human can tolerate, less than 100 mR, with no adverse biological effects

False

What is the sensitivity of an atom to its magnetic field?

Gyromagnetic ratio

The primary biologically reactive molecular byproducts formed during the radiolysis of water are thought to be:

H+ and OH-

Which of the following has the highest gyromagnetic ratio?

Hydrogen

The single most important advantage of spiral CT is which of the following?

Imaging a large volume of anatomy in one breath hold

The units of gyromagnetic ratio (atom's sensitivity to magnetic field) associated with polar protons are expressed as:

MHz/T

Which of the following technologies has the best contrast resolution?

MRI

Free induction decay =

Nuclear relaxation in which RF signal (radiation) is emitted

Fusion scans man combine.....and.....images

PET, CT

If a small anatomical detail occupies less volume than that of one voxel which its is being projected, that detail may be rendered visible. This is an example of:

Partial volume averaging

The principle on which ultrasound is based is called the......effect

Piezoelectric

Considering MRI physics, during nuclear relaxation:

Radiation is emitted

A CT scan is made with a 0.5 mm slice thickness and a 0.5 mm pixel size. What is the size of the voxel?

(pixel size)^3 = (0.5)^3 = 0.125 mm Length X width X height (0.5) X (0.5) X (0.5)

The whole body radiation dose encountered in a technetium bone scan is approximately how many rads?

0.2

The generally accepted range of useful densities on a radiograph is.....above base + fog

0.5 - 2.5

Lines on radiographs running perpendicular to the direction of the film traveling through the processor are:

1. An indication of dirty rollers 2. Usually repeated every 3.14 inches

The MRI image appearance is determined by which of the following?

1. T1 relaxation time (white bone) 2. T2 relaxation time (dark bone) 3. Spin density

The cardinal principles of radiation protection is/are:

1. Time 2. Distance 3. Shielding

Assuming a FFD of 72 inches, which is the maximum allowable deviation of the collimation from the actual x-ray beam size?

1.2 inches

Diagnostic ultrasound intensity is measured in:

W/cm squared

Do x-rays or CT's have better spatial resolution?

X-rays have 2X better spatial resolution

What do x-rays do better than CT's? What do CT's do better than x-rays?

X-rays have 2X better spatial resolution and CT's collimate 2X better

Probably the greatest hazard associated with MRI is:

a projectile

A CT scanner initially obtains adult images in which plane?

axial

A minimal CT exam of a body part includes:

bone and soft tissue windows

If all other factors remain constant, radiation dose is related source to object distance.....

by the inverse square law

The medical physicist.......accurately relate the dose in mR, millirads or millirems form only the technique factors set into the xray machines

cannot

Bone window =

close to 1000

Spin density can be defined as hydrogen.....

concentration (because Hydrogen has highest gyromagnetic ratio and thus spin density)

Which of the following will always appear black on MRI regardless of the pulse sequence?

cortical bone

If all the other factors remain constant, radiation does is related to xray beam on time.....

directly

The exchange of......between two systems of a specific......is called......

energy, frequency, resonance

The RF signal emitted by tissues following RF excitation is called a:

free induction decay

The more narrow the CT window setting the......the contrast of the displayed image

greater

A hypothesized bioeffect of increasingly stronger MRI magnet strength is:

heating

Radiation induced damage in biological tissues:

is treated in the presence of increased oxygen levels of the tissue is being radiated

Voxels are:

isotropic

The rate of precesion of any polar portion of any element is called its:

larmor frequency

Radiation production guidelines in US are based on which type of dose-response relationship?

linear non threshold

The ability of an xray machine to produce constant radiation output at various conditions of mA and exposure time producing the same mAs is called:

linearity

Soft tissue window =

low - close to 0-30

A Hounsfield Unit:

numerical value of a pixel

Hot spots on a static bone scan image corresponds to:

osteogenic activity

Dose fractionation is less effective than a single dose of therapeutic radiation because:

recovery occurs between doses

Radionucleotide imaging is a......and......imaging modality

sensitive, nonspecific

The diagnostically useful portion of a characteristic curve mostly includes the......portion of the curve

straight line

The weakest link in the chain of diagnostic imaging is:

the processing system

All of the following are contraindications for MRI except:

total hip replacements

Spiral CT scans have:

very very fast scan times

T1 = T2 =

white bone dark bone