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BPH702S - BIOMEDICAL PHYSICS - 2ND OPP - JAN 2023 |
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nAm I BI A un IVERS ITV
OF SCIEnCE Ano TECHn OLOGY
FACULTY OF HEALTH, NATURAL RESOURCES AND APPLIED SCIENCES
DEPARTMENT OF NATURAL AND APPLIED SCIENCES
QUALIFICATION: BACHELOROF SCIENCE(MAJOR AND MINOR)
QUALIFICATION CODE: 7BOSC
LEVEL: 7
COURSE CODE: BPH702S
SESSION: JANUARY2023
COURSE NAME: BIOMEDICAL PHYSICS
PAPER: THEORY
DURATION: 3 HOURS
MARKS: 100
SECOND OPPORTUNITY/SUPPLEMENTARY EXAMINATION PAPER
EXAMINER(S) DR. VAINO INDONGO
MODERATOR: DR. NDESHIHAFELAVERA UUSHONA
INSTRUCTIONS
1.
Write all your answers in the answer booklet provided.
2.
Read the whole question before answering.
3.
Begin each question on a new page.
PERMISSIBLE MATERIALS
Non-programmable Scientific Calculator
THIS MEMORANDUM CONSISTS OF 5 PAGES
(INCLUDING THIS FRONT PAGE)
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QUESTION 1
[20]
1.1 Define the following terms: (i) tomography, (ii) radio-sensitivity, and (iii) nuclear magnetic
resonance.
(6)
1.2 State two medical imaging modalities whose performances are based on detections of
gamma rays ejected from the patient's body where the inner structures are obtained as a
result of spontaneous decays of radioisotopes.
(2)
1.3 Explain, in short, why is lubrication essential on mechanical or human machines?
(2)
1.4 A collagen of cross-sectional of 1.2 x 10 - 2 m2 and mass m kg has a tensile strength of
2.3 x 10 4 Nm-2• Calculate the;
(i) breaking force of the collagen, and
(3)
(ii) value of its mass, g = 9.8 m/s 2.
(2)
1.5 State two physical uses of bones in the skeleton.
(2)
1.6 The application of physics is an important phenomenon in observing electrical activities
of a biological material. Discuss in short the uses of the following instruments:
(i) Electroculography
(1)
(ii) Electroencephalography (EEG)
(1)
iii) Sphygmanometer
(1)
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QUESTION 2
[30]
2.1 Define flow rate and show that it is a product of cross-sectional area of a channel and
velocity of fluid under consideration.
(3)
2.2 Consider an incompressible fluid flowing at a steady rate through an enclosed pipe of
cross-section. Use the information in Figure 1 to derive the equation of continuity.
(5)
Figure 1
2.3 (i) State Bernoulli's principle in simple words.
(2)
(ii) State and discuss any two entrainment devices that work on Bernoulli's principle by
increasing fluid speed to create low pressures.
(4)
2.4 Define a transducer.
(1)
2.5 Elaborate on refraction of ultrasound, when an incident beam traverses through a
body of the patient.
(4)
2.6 Given that the ultrasound frequency of 2 MHz and wavelengths of 6.5 nm was used
to take an image of a bone. Calculate the acoustic impedance of a bone if the density
of a bone is 2.2 x 103 kg/m 3.
(3)
2.7. Calculate the amplitude reflection coefficient for a fat-liver interface.
= = Z (fat) 1.65 x 106 ; Z (liver) 1.34x10 6•
(4)
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2.8. The relative sound intensity is measured on a logarithmic scale. Calculate the
relative intensity of a sound beam when it is:
(i) reduced to a quarter.
(2)
(ii) a six-fold increase.
(2)
QUESTION 3
[30]
3.1 The human body is composed of 63% of hydrogen atoms. If we zoom into one of the
hydrogens past the electron cloud we see a nucleus comprised of a single proton. The
proton possesses a property called spin. State the properties of a spin.
(4)
3.2 Many magnetic resonance imagers operate at a magnetic field strength of 1.5 Tesla. A few
research units operate at 4.7 Tesla. What is the resonance frequency of the hydrogen
nuclei in both magnetic fields? y= 42.58 MHz/T
{2)
3.3 A group of spins was placed into a magnetic field with the number of spins in the lower
energy level of 5 and that in the upper level as 25. Calculate the energy difference LlE
between the spin states; k is Boltzmann's constant, l.3805x10- 23JX1; and the temperature
is 27°C.
(7)
3.4 A sample has a T2 of 50 ms. The net magnetization of 100 Tis rotated into the xy-plane
and allowed to decay. How much transverse magnetization will be present 17 ms after
being placed in the plane?
{3)
3.5 An x-ray machine mounted in Khomas Medical Centre has tungsten (1nW) as a target
material. One male patient with a fracture on the arm had to undergo radiographic
procedure to determine the severity of a fracture. The radiologist has decided on the
voltage of 90 keV and the radiographer recommended for 100 keV for settings during the
procedure. These two medical personnel mutually agreed for an average potential
difference to be set on the instrument. Calculate the energy of x-ray produced during this
imaging procedure.
(5)
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3.6 An x-ray beam intensity of 170 mW/m 2 was focused to pass through aluminium material
of half-value thickness ti;2 = 1.4 cm. Estimate the strength of intensity after passing
through a thickness of 2.0 cm for aluminium.
(5)
3. 7 Explain the attenuation by means of absorption and scattering of x-rays when passed
through a human body for imaging purposes.
(4)
QUESTION 4
[20]
4.1 State and discuss the law of radioactive decay.
(4)
4.2 Explain in short the term biological half-life.
(2)
4.3 Sodium-24 (24 Na) has a half-life of 15 hours.
(i) Estimate is its decay constant (s-1).
(2)
(ii) Calculate the activity of 24 Na radionuclide after 24 hours, when its activity A= 500 Bq
att=0.
(3)
4.4 Given that the activity of a radionuclide is A =-dN/dt =AN and decay constant is
A =ln2/T1;2,prove that the mean life, r = ½-Show all steps.
(5)
4.5 During radiotherapy, either radioactive or non-radioactive sources are used for efficient
treatment of cancer. Give two reasons why collimators are crucial in the gantry of a
radiotherapy equipment.
(4)
END
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