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174 Cards in this Set
- Front
- Back
In Fourier analysis a complex wave pattern can be constructed by adding together s sufficient number of:
a. Sine waves b. Cosine waves c. Electromagnetic waves d. Mechanical waves e. Tangent waves f. Sound Waves g. USG waves |
a) Sine waves, b) Cosine waves
|
|
Select all correct statements regarding the indices of diagnostic test performance:
a. SEN=1/SPE b. SEN=TP/(TP+FN) c. SEN=TP/(TP+TN) d. SPE=TN/(TP+TN) e. SPE=TN/(TN+FP) f. SPE=FP/(FP+FN) g. SPE=1/SEN |
Remember the diagram. a/(a+c) and d/(d+b)
|
|
Which of the following units may be used to quantify the potential energy?
a. W b. J c. J/s d. Kcal e. Kcal/min f. Kcal/hr g. W*s |
J and Kcal
|
|
Select possible value/s) of the arterial blood pressure
|
150cm H2O and 10kPa to 16kPa
|
|
Select possible value(s) of heart and lung frequencies (HRF and LUF, respectively)
|
Hz means per second. HR=about 70bpm=1Hz. Lung frequency is 10-20 per minute=0.16-0.33Hz.
|
|
BMR depends on the temperature of the body. If a patient has a temperature of 312K, the BMR is (about):
a. 20% smaller than normal b. 10% smaller than normal c. 1% smaller than normal d. 1% greater than normal e. 5% greater than normal f. 10% greater than normal g. 20% greater than normal |
For every increase of 0.5C in internal temperature of the body, the BMR increases by about 7 percent.
|
|
Select possible process(es) responsible for the heat loss from the human body
a. Radiation b. Breathing c. Diffusion d. Thinking e. Digestion f. Convection g. Sweat evaporation |
a) radiation, b) Breathing, f) convection, g) Sweat evaporation
|
|
Select possible value(s) of the typical voltage output from the defibrillator (about):
a. 1V b. 10V c. 100V d. 1kV e. 5kV f. 20kV g. 50kV |
charges a bank of capacitors to approximately 1000 volts with an energy content of 100-200 joules.
|
|
Which of the following statements are true for AC and DC currents:
a. AC current frequency is always 0 Hz b. AC current frequency is always 50Hz c. AC current frequency is always >0Hz d. Effective DC current = maximum current value e. Effective DC current <maximum current value f. Effective DC current > maximum current value g. Ohmʼs law is valid only for DC current |
c) AC current frequency is always >0Hz, and
e) Effective DC current < maximum current value |
|
Which of the following functional groups are non-polar?
a. Methyl (CH3) b. Ethyl (C2H5) c. Aldehyde (COH) d. Carboxyl (COOH) e. Hydroxyl (OH) f. Amino (NH2) g. Propyl (C3H7) |
a) methyl
b) ethyl g) propyl |
|
Which of the following are true for gamma camera (GC)?
a. GC shows the distribution of radioactivity within the patientʼs body b. GC is simply a standard XR detector c. GC is simply a standard electron detector d. A computer is necessary for GC operation e. GC is used as a radiation detector in CT f. GC is commonly used in radio-therapy g. GC is a special detector used only for thyroid examination |
it is a device that is used to image gamma radiation emitting radioisotopes in the body. Is used in SPECT and PET scans as well. Thus, a) is correct, and d) is correct.
|
|
At what Reynolds number is flow in a tube usually turbulent?
|
above 3000
|
|
According to the Poisseuille equation, the flow rate Q, in a tube is proportional to what powers of the radius (R) and length (L) (Q-R^A*L^B, what are numerical values of A and B)?
|
P=8rhoLQ/pr^4. Thus A=4, B=-1
|
|
How does the resistance to blood flow depend upon the length of a blood vessel?
|
K is proportional to L
|
|
The Young's modulus of compact bone is:
|
About 15 GPa, slightly bigger than that of oak.
|
|
Consider Fickʼs first law. A 4-fold increase of the flux of particles may be induced by:
a. 4-fold increase of the diffusion coefficient b. 4-fold decrease of the diffusion coefficient c. 4-fold increase of the concentration gradient d. 4-fold decrease of the concentration gradient e. 3-fold increase of the concentration gradient and 2-fold increase of the diffusion coefficient f. 2-fold decrease of the concentration gradient and 2-fold increase of the diffusion coefficient |
a), c) and e).
|
|
Consider Nernstʼs equation for electro-diffusive equilibrium in a 2-compartment system. The electro-diffusive equilibrium potential across the membrane equals to zero when:
|
Temperature equals 0K and concentrations of ions are equal in both compartments. Nernst equation: 2.303(RT/zF)*log([ion ouside]/[ion inside]) where z=number of moles of electrons and F=Faraday constant.
|
|
To determine the pH value, a pH-meter is used. Which physical quantities are measured with the use of a pH-meter?
|
A pH meter is a voltmeter that measures electrical potential difference, but instead of showing volt, it shows the pH, as every pH unit is about 0.06V.
|
|
Consider 2 lenses having focal lengths of 0.25m and 0.02m. The focal length of a comvination of the two lenses equals to how many Ds?
|
(1/0.25)+(1/0.02)=54D
|
|
The electromagnetic radiation spectrum is spread over a broad range of the wavelengths. Select the value(s) which correspond to the visible light region:
|
400nm to 700nm
|
|
Which frequencies are detected by the human ear?
|
20Hz to 20kHz
|
|
For vision to be good at both large and distances and close up, the eye must have an accommodation of at least how many Ds?
|
4D
|
|
What is the energy range produced by an XR tube?
|
20kEv to 150kEv.
|
|
Which of the following phenomena are necessary for the laser operation?
a. Radioactivity b. Ion production c. Optical pumping d. Population inversion e. Stimulated emission f. Thermal diffusion g. Thermal motion |
c) optical pumping
d) population inversion e) stimulated emission |
|
What does the absorption law describe?
|
Relates attenuation of radiation to the thickness of tissue traversed and an absorption coefficient
|
|
Which effect(s) limit the AC current that can be safely injected into the human body?
|
c) electrolysis
d) heating of the body g) stimulation of neural tissue |
|
Which units are used to quantify the specific absorption rate (SAR)?
|
W/kg
|
|
Which of the following effective dose equivalent value(s) are dangerous to humans (Sv - Sievert)
|
more than 3 Sv will cause death within 30 days in 50% of cases. 2-5 Sv are dangerous.
|
|
What is teletherapy?
|
Radiation therapy administered by a machine that is positioned at some distance from the patient.
|
|
The grid in XR examinations are used to partially remove?
|
Scattered radiation
|
|
Which of the following values of optical density may be observed for an XR film?
|
Useful densities in diagnostic radiology range from about 0.2 to about 2.5
|
|
Hounsfield units that may be observed in a healthy patient?
|
From -1000 (air) to around 3000 (compact bone)
|
|
Which of the tissue characteristics can be visualised in a CT image?
|
CT scans measure the density of of tissues, and can be used to detect hemorrhage, tumors, and calcifications, among other things.
|
|
Which of the following statements are true for ultrasound waves?
a. Frequency=reciprocal of period b. Intensity=power per unit area c. Interference=algebraic summation of waves d. Absorption=energy dissipation in the medium e. Velocity=distance to complete one cycle f. Wavelength=rate of travel of sound through the medium g. Period=time to complete one cycle |
Frequency=reciprocal of period, intensity=power per unit area, and period=time to complete one cycle.
|
|
Which type(s) of radioactive isotope(s) are used in PET scans?
|
Gamma emitters
Proton emitters. Positron emission is also beta+ emission. |
|
What is the Doppler shift?
|
The magnitude of the frequency change in hertz when sound and observer are in relative motion away from or toward each other. In other words, it is the difference between transmitted frequency and the observed frequency.
|
|
What can be visualised in an MR image?
|
Proton density.
(Blood flow, tissue density?) |
|
What is the temperature of body skin?
|
32-37 degrees celsius (305-310K)
|
|
What is the most important mode of heat loss in a naked, human body?
|
Radiation
|
|
A side of a square equals to 1+/- 0.1 cm. The relative error of the square area is equal to?
|
0.2
|
|
Select possible values of arterial blood pressure
|
10kPa to 17kPa.
|
|
Possible values of respiration frequency?
|
In normal individuals 10-20 times per minute, or (1/6)Hz to (2/6)Hz
|
|
Standard deviation indicates
|
the amount of variability in a collection of measurements
|
|
Consider a sound source having an intensity of 30 dB. What is the absolute intensity?
|
[dB]=10*lg(W/m^2). Multiply answer by 10^-12, because it is the threshold for human hearing.
|
|
Energy values of visible light
|
2-3 eV
|
|
The minimal value of DC voltage which may produce an electric shock?
|
100V
|
|
An electric model of a cell membrane consists of
|
a resistor and capacitor in series
|
|
What are isobars?
|
Isobars are two nuclides that have the same number of nucleons.
|
|
Formula for calculating half-life.
|
Nt=No(1/2)^(t/t0.5). Where Nt=quantity that still remains, No=initial quantity.
|
|
Blood viscosity is dependent on
|
viscosity of plasma and hematocrit
|
|
How can you measure residual volume?
|
Plethysmograph
|
|
Electrode placements for ECG
|
Red - Right arm
Black - Right leg Green - Left leg Yellow - Left arm |
|
Chronaxie and Rheobase
|
The chronaxie (or chronaxy) is the minimum time over which an electric current double the strength of the rheobase needs to be applied, in order to stimulate a muscle fiber or nerve cell. C is always bigger than R
|
|
Comparing EEC and ECG signals, the amplitudes
|
of EEC signals are always smaller than ECG ones
|
|
How does the resistance to blood flow depend upon the radius of a blood vessel?
|
Poiseuille-Hagen Formula: R=(8*rho*L)/(pi*r^4)
|
|
The open and closed bells in a stethoscope detect, respectively?
|
The open bell is used to detect low-frequency sounds, while the closed bell is used to detect high frequency sounds.
|
|
As the body temperature decreases to 30 degrees celsius, the blood viscosity
|
increases
|
|
Which parameter is routinely used to characterize XR tube operation?
|
Product of the electron beam current and the operation time
|
|
The maximum sensitivity of the human ear occurs at about 3000Hz. Which part of the ear decides the value?
|
Basilar membrane
|
|
Consider a metal electrode immersed in a solution. What happens
|
Metal ions diffuse into the solution
|
|
Which part of the human eye has the biggest focusing power?
|
Cornea (about 43D)
|
|
Vision correction: Cylindrical, concave, and convex lenses are used for
|
Cylindrical: ocular astigmatism
Concave: Myopia Convex: Hyperopia |
|
Two XR films were overlapped. The optical density of each film equals to 0.1. The total optical density is then
|
0.1*0.1=0.01
|
|
Routinely used XR tube voltage during CT examinations
|
100 kV
|
|
Laser which emits radiation in the visible light spectrum
|
GaAs (semiconductor)
|
|
The absorption law is useless in the description of
|
Electron absorption
|
|
The near field limit for a coil used in magneto-therapy equals to
|
1000km
|
|
What is the unit of Specific Absorption Rate (SAR)?
|
W/kg
|
|
An AC current was applied through electrodes on a human arm. Which current will be felt?
a. 100 Hz, 2mA b. 100 kHz, 1mA c. 100 kHz, 5mA d. 100kHz, 10 mA |
a. 100 Hz, 2mA
|
|
Typical dose in radiotherapy is
|
20-80 Gy
|
|
If a Cu filter is added to an XR tube, what happens to the energy
|
The minimal XR energy decreases
|
|
Frequencies used in microwave diathermy
|
Therapeutic: 2450 MHz (122.5 mm)
Physiotherapeutic: 915 MHz (327 mm) and 433.9 MHz (690 mm) |
|
A developed XR film was irradiated by mistake a second time. What is the effect?
|
No change
|
|
Which of the following statements is true for electromagnetic waves?
a. Frequency=time to complete one cycle b. Intensity=power per unit time c. Interference=algebraic summation of waves d. Absorption=rate of travel through the medium |
c. interference=algebraic summation of waves. a=USG, b=USG.
|
|
Which type of radioactive isotope is used in SPECT?
|
gamma emitters
|
|
Which tissue characteristic is routinely visualized in an MR image?
|
proton density
|
|
Which technique is used to estimate body fat content
|
Bio-impedence measurements
|
|
What happens to the energy that is lost as a beam of ultrasound is absorbed in the human body?
|
It appears as heat
|
|
Heat loss from the body due to radiation is dependent upon
|
the ambient temperature
|
|
Human bone is mostly composed of
|
collagen and calcium apatite (Ca5(PO4)3(OH))
|
|
Number 11 in the binary system equals to
|
1011 (THE FUCK?!?!? Why the fuck should we have to learn this?!?)
|
|
Young modulus of human compact bone is about
|
15 GPa
|
|
Intensity used in magneto-therapy
|
5 mT. But this is complete and utter bullshit. Magneto-therapy is an "alternative" medicine, which has no proven effect. what the fuck is this shit?!?
|
|
Common trace elements in the human body
|
1. Boron
2. Copper 3. Iodine 4. Selenium 5. Zinc 6. Iron |
|
In Fourier analysis a complex wave pattern can be constructed by adding together s sufficient number of:
a. Sine waves b. Cosine waves c. Electromagnetic waves d. Mechanical waves e. Tangent waves f. Sound Waves g. USG waves |
a) Sine waves, b) Cosine waves
|
|
Select all correct statements regarding the indices of diagnostic test performance:
a. SEN=1/SPE b. SEN=TP/(TP+FN) c. SEN=TP/(TP+TN) d. SPE=TN/(TP+TN) e. SPE=TN/(TN+FP) f. SPE=FP/(FP+FN) g. SPE=1/SEN |
Remember the diagram. a/(a+c) and d/(d+b)
|
|
Which of the following units may be used to quantify the potential energy?
a. W b. J c. J/s d. Kcal e. Kcal/min f. Kcal/hr g. W*s |
J and Kcal
|
|
Select possible value/s) of the arterial blood pressure
|
150cm H2O and 10kPa to 16kPa
|
|
Select possible value(s) of heart and lung frequencies (HRF and LUF, respectively)
|
Hz means per second. HR=about 70bpm=1Hz. Lung frequency is 10-20 per minute=0.16-0.33Hz.
|
|
BMR depends on the temperature of the body. If a patient has a temperature of 312K, the BMR is (about):
a. 20% smaller than normal b. 10% smaller than normal c. 1% smaller than normal d. 1% greater than normal e. 5% greater than normal f. 10% greater than normal g. 20% greater than normal |
For every increase of 0.5C in internal temperature of the body, the BMR increases by about 7 percent.
|
|
Select possible process(es) responsible for the heat loss from the human body
a. Radiation b. Breathing c. Diffusion d. Thinking e. Digestion f. Convection g. Sweat evaporation |
a) radiation, b) Breathing, f) convection, g) Sweat evaporation
|
|
Select possible value(s) of the typical voltage output from the defibrillator (about):
a. 1V b. 10V c. 100V d. 1kV e. 5kV f. 20kV g. 50kV |
charges a bank of capacitors to approximately 1000 volts with an energy content of 100-200 joules.
|
|
Which of the following statements are true for AC and DC currents:
a. AC current frequency is always 0 Hz b. AC current frequency is always 50Hz c. AC current frequency is always >0Hz d. Effective DC current = maximum current value e. Effective DC current <maximum current value f. Effective DC current > maximum current value g. Ohmʼs law is valid only for DC current |
c) AC current frequency is always >0Hz, and
e) Effective DC current < maximum current value |
|
Which of the following functional groups are non-polar?
a. Methyl (CH3) b. Ethyl (C2H5) c. Aldehyde (COH) d. Carboxyl (COOH) e. Hydroxyl (OH) f. Amino (NH2) g. Propyl (C3H7) |
a) methyl
b) ethyl g) propyl |
|
Which of the following are true for gamma camera (GC)?
a. GC shows the distribution of radioactivity within the patientʼs body b. GC is simply a standard XR detector c. GC is simply a standard electron detector d. A computer is necessary for GC operation e. GC is used as a radiation detector in CT f. GC is commonly used in radio-therapy g. GC is a special detector used only for thyroid examination |
it is a device that is used to image gamma radiation emitting radioisotopes in the body. Is used in SPECT and PET scans as well. Thus, a) is correct, and d) is correct.
|
|
At what Reynolds number is flow in a tube usually turbulent?
|
above 3000
|
|
According to the Poisseuille equation, the flow rate Q, in a tube is proportional to what powers of the radius (R) and length (L) (Q-R^A*L^B, what are numerical values of A and B)?
|
P=8rhoLQ/pr^4. Thus A=4, B=-1
|
|
How does the resistance to blood flow depend upon the length of a blood vessel?
|
K is proportional to L
|
|
The Young's modulus of compact bone is:
|
About 15 GPa, slightly bigger than that of oak.
|
|
Consider Fickʼs first law. A 4-fold increase of the flux of particles may be induced by:
a. 4-fold increase of the diffusion coefficient b. 4-fold decrease of the diffusion coefficient c. 4-fold increase of the concentration gradient d. 4-fold decrease of the concentration gradient e. 3-fold increase of the concentration gradient and 2-fold increase of the diffusion coefficient f. 2-fold decrease of the concentration gradient and 2-fold increase of the diffusion coefficient |
a), c) and e).
|
|
Consider Nernstʼs equation for electro-diffusive equilibrium in a 2-compartment system. The electro-diffusive equilibrium potential across the membrane equals to zero when:
|
Temperature equals 0K and concentrations of ions are equal in both compartments. Nernst equation: 2.303(RT/zF)*log([ion ouside]/[ion inside]) where z=number of moles of electrons and F=Faraday constant.
|
|
To determine the pH value, a pH-meter is used. Which physical quantities are measured with the use of a pH-meter?
|
A pH meter is a voltmeter that measures electrical potential difference, but instead of showing volt, it shows the pH, as every pH unit is about 0.06V.
|
|
Consider 2 lenses having focal lengths of 0.25m and 0.02m. The focal length of a comvination of the two lenses equals to how many Ds?
|
(1/0.25)+(1/0.02)=54D
|
|
The electromagnetic radiation spectrum is spread over a broad range of the wavelengths. Select the value(s) which correspond to the visible light region:
|
400nm to 700nm
|
|
Which frequencies are detected by the human ear?
|
20Hz to 20kHz
|
|
For vision to be good at both large and distances and close up, the eye must have an accommodation of at least how many Ds?
|
4D
|
|
What is the energy range produced by an XR tube?
|
20kEv to 150kEv.
|
|
Which of the following phenomena are necessary for the laser operation?
a. Radioactivity b. Ion production c. Optical pumping d. Population inversion e. Stimulated emission f. Thermal diffusion g. Thermal motion |
c) optical pumping
d) population inversion e) stimulated emission |
|
What does the absorption law describe?
|
Relates attenuation of radiation to the thickness of tissue traversed and an absorption coefficient
|
|
Which effect(s) limit the AC current that can be safely injected into the human body?
|
c) electrolysis
d) heating of the body g) stimulation of neural tissue |
|
Which units are used to quantify the specific absorption rate (SAR)?
|
W/kg
|
|
Which of the following effective dose equivalent value(s) are dangerous to humans (Sv - Sievert)
|
more than 3 Sv will cause death within 30 days in 50% of cases. 2-5 Sv are dangerous.
|
|
What is teletherapy?
|
Radiation therapy administered by a machine that is positioned at some distance from the patient.
|
|
The grid in XR examinations are used to partially remove?
|
Scattered radiation
|
|
Which of the following values of optical density may be observed for an XR film?
|
Useful densities in diagnostic radiology range from about 0.2 to about 2.5
|
|
Hounsfield units that may be observed in a healthy patient?
|
From -1000 (air) to around 3000 (compact bone)
|
|
Which of the tissue characteristics can be visualised in a CT image?
|
CT scans measure the density of of tissues, and can be used to detect hemorrhage, tumors, and calcifications, among other things.
|
|
Which of the following statements are true for ultrasound waves?
a. Frequency=reciprocal of period b. Intensity=power per unit area c. Interference=algebraic summation of waves d. Absorption=energy dissipation in the medium e. Velocity=distance to complete one cycle f. Wavelength=rate of travel of sound through the medium g. Period=time to complete one cycle |
Frequency=reciprocal of period, intensity=power per unit area, and period=time to complete one cycle.
|
|
Which type(s) of radioactive isotope(s) are used in PET scans?
|
Gamma emitters
Proton emitters. Positron emission is also beta+ emission. |
|
What is the Doppler shift?
|
The magnitude of the frequency change in hertz when sound and observer are in relative motion away from or toward each other. In other words, it is the difference between transmitted frequency and the observed frequency.
|
|
What can be visualised in an MR image?
|
Proton density.
(Blood flow, tissue density?) |
|
Using the scientific notation of frequency, 10,000Hz can also be written as
|
100 hHz
10 kHz 0,01 MHz |
|
Body Mass Index formula is
|
m/(height)^2, where m=weight in kilograms, and height=height in meters
|
|
Body Surface Area (BSA) formula is
|
0,202*(mass^0,425)*(height^0,725)
|
|
In case of electrolyte solutions, what does Ohm's law describe?
|
The relation between density of electric current (EC) and electric field intensity
|
|
The sides of a square are 1 cm +/- 0.1cm. What is the relative error of the area?
|
1.1^2-0.9^2=0.4. Thus, +/- 0.2.
|
|
Consider a naked human body in air. What is the most important mode of heat loss?
|
Radiation, about 55%
|
|
Formula for BMR and average BMR?
|
BMR=4.1*m^0.75.
BMR for men is about 2000 kcal, or 8.37 MJ, as 1kcal=4184 Joules |
|
Where is the core temperature measured?
|
1) Esophagus
2) Rectum The eardrum is used as an approximation of the core temperature, but varies more |
|
Which device is the most popular in radiation detection?
|
Gamma camera
|
|
What is the most characteristic feature of a visco-elastic material?
|
The stress/strain relationship depends on time
|
|
In which part of the body is the pressure sub-atmospheric?
|
1) Airways at the end of expiration
2) Intrapleural (intrathoracic) cavity |
|
What is the ultimate stress (tension) of human cortical bone?
|
About 1.5%; lower as you age.
|
|
What is the average Peak Expiratory Flow rate?
|
Arbitrary question without more information, however, the graph (lecture) says 5L/s. It all depends on age, gender, height, and weight.
|
|
How long would a topical nerve action potential take to travel from the brain to the feet?
|
Depends on the nerve fiber, but for the sake of it say 40-60ms.
|
|
ECG quick guide. The P, QRS, and T represent?
|
P - Atrial depolarization
QRS - Ventricular depolarization and atrial repolarization ST and T - ventricular repolarization |
|
What amplitude range would be expected for electrical signals measured on the skin surface of a human body?
|
1uV to 1mV
|
|
What is a Snellen chart?
|
It is an eye chart used to measure visual acuity
|
|
The eye is most sensitive to which colour?
|
Green
|
|
How long would it take for sound to be transmitted between two people standing 3m apart?
|
Speed of sound at sea level: 340.3 m/s. (340.3(m/s)/3m)^-1= 8.81 ms.
|
|
What is the value of the resonant frequency of the human ear canal?
|
3000 Hz (proceed with caution, I have no idea if this is correct)
|
|
From a mechanical point of view, the middle ear may be regarded as
|
a mechanical transformer, that does not require any energy in the form of ATP
|
|
Could a current of 0.1mA at 50Hz cause cardiac fibrillation?
|
If applied directly to the heart, yes.
|
|
Approximate energy of UV radiation?
|
10-13eV
|
|
Which unit is used to describe heat energy?
|
Joule. (W*s=(J/s)*s=J, and 1 kcal=4184 Joules)
|
|
Which unit is used to describe absorbed dose?
|
Gray (Gy)
|
|
What is brachytherapy?
|
Internal radiotherapy, i.e., the source of radiation being implanted in tissue
|
|
Surface exposures that may be detected after XR?
|
40mR to 4,000mR.
|
|
As result of the X-ray examination the transparent film without traces of the object was obtained. Please give all possible explanations of such result.
|
No traces of the image → no irradiation:
1) X-ray tube did not operate 2) Filter was not properly selected 3) Film was not irradiated, e.g. by mistake not in the cassette during irradiation |
|
What is the value of the Larmor frequency for protons in a magnetic field of 1T?
|
The Larmor frequency can go fuck itself. That being said, the answer is about 40 MHz.
|
|
Formula for calculating effective half-life time.
|
Te = (Tp x Tb) / ( Tp+Tb). When both radioactive decay and biological elimination are present, the effective half-life will always be less than either the physical or biological half-life. If the difference in the two half-life values is rather large, the effective half-life will be slightly less than the shorter half-life of the two; if the two are equal, the effective half-life will be one-half of the physical or biological half-life value. Biological elimination is less than radioactive decay.
|
|
mAs - milliamperage seconds determines
|
it determines the number of electrons released off of the cathode, also represents the number of XR photons produced by the anode. The faster the mAs the better.
|
|
Optimal exposure time in XR?
|
1/60s or less. Doubling the mAs doubles the film exposure.
|
|
What is kVp?
|
It is the electrical potential across the XR tube when XR are not produced. Increasing kVp, increases the penetrability of the XR beam and increases exposure of the film. Determines contrast.
|
|
Magnetic characteristics of tissue that are the source of image contrast?
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1) Amplitude of magnetization → proton density
2) Spin-lattice relaxation time T1 3) Spin-spin relaxation time T2 |
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Hazards associated with MRI
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1) Magnetic fields B0 (3.0 T) • Internal magnetic objects (prosthetic devices, surgical clips) • External magnetic objects (medical instruments) • Influence on ion transport
2) Gradients → different gradient fields are turned on and turned off during imaging → magnetic field has to be changed → ΔB/Δt → US Food and Drug Administration → 6 T/s 3) RF energy absorption → heating of the tissue 4) Acoustic noises 5) Claustrophobia |
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Frequency of USG
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>20kHz. Diagnostic ultrasound: ~0.5 MHz to ~40 MHz
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Interactions of ultrasound with tissue
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Energy is dissipated in a medium → absorption →
heating of the medium → the law of absorption |
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How do you best select parameters in ultrasound examinations?
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Resolution → as big frequency as possible.
Absorption → as small frequency as possible. A compromise is needed to select the optimal frequency |
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How much energy is lost in feces and urine?
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5% + 5%
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What determines physical fitness?
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The capacity to consume oxygen. MO2CR=28 (very poor fitness) to 70 (superior fitness)
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What happens to BMR in hypo- and hyperthyroidism?
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Hypo- : 20-40% lower
Hyper- : 30-70% higher |
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Most of the energy in the body is used
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to maintain an internal temperature of 37degrees, i.e., heat production
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Processes that are responsible for heat loss from the body (at rest)
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1) Radiation: 55%
2) Convection/conduction: 25% 3) Breathing: 14% 4) Evaporation of sweat: 6% |
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Heat loss values
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At rest: 1.5 kcal/min
Heavy exercise: 15 kcal/min 1) Radiation: 5% 2) Convection/conduction: 15% 3) Evaporation of sweat: 80% |
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How much thermal radiation does the human body emit?
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3 W/m^2
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What is binding energy?
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Energy to be supplied to separate a nucleus into protons and neutrons. The binding energy is negative.
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What is a positron?
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Antiparticle of an electron, with a charge of +1.
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What is a gamma photon?
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The excess energy in nuclei are emitted as gamma photons (electromagnetic radiation). IT is a small u nit of energy that travels with the speed of light and has no mass.
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What is radioactivity?
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Activity is the rate at which the nuclei within the sample undergo radioactive transitions and can be expressed in therms of nubbier of transitions per second. The two units used are:
1) Becquerel 2) Curie |
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Which radioisotopes are used in medicine?
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1) 131 I
2) 125 I 3) 133 Xe 4) 99m Tc (deposits at places of elevated metabolic activity) |
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Remark regarding gamma cameras
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Computers are not needed, all you need is a CRT tube
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Example of when SPECT is used?
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Blood perfusion in the heart
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Positron-emitting nuclides include
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1) 11C
2) 13N 3) 15O 4) 18F |