Engineering principles in Medicine (BME-5109)

1.(a) Write the major key principles of biomedical engineering.

Ans: The major key principles of biomedical engineering are:

1.(b) List five stages in the use of radioisotopes which define their use in clinical diagnosis.

Ans: Five stages in the use of radioisotopes:

1.(c) Explain radionuclide imaging.

Ans: Radionuclide imaging is a nuclear medicine imaging technique that uses a small amount of radioactive material (radiotracer) to visualize and evaluate the function of organs and tissues. The radiotracer is administered into the body by injection, inhalation, or oral intake. As the tracer accumulates in the target organ, it emits gamma rays or positrons that are detected by a gamma camera, SPECT, or PET scanner. A computer processes these signals to produce images of the organ.

Principle: The technique is based on the detection of radiation emitted from a radioactive tracer distributed within the body. The amount of radiation detected from different regions reflects the physiological activity of the tissue.

Applications:

• Detection and staging of cancer
• Assessment of heart function and blood flow
• Brain imaging for neurological disorders
• Thyroid and kidney function studies

Advantages:

• Provides functional information about organs.
• Enables early detection of diseases.
• Non-invasive diagnostic method.

Disadvantages:

• Involves exposure to ionizing radiation.
• Lower image resolution compared to CT and MRI.

Conclusion: Radionuclide imaging is an important diagnostic tool that helps physicians evaluate organ function and detect diseases by tracking the distribution of radioactive tracers within the body.

1.(d) How is the rate constant related to the biological half-life when measuring clearance of radioactive material from the body?

Ans: The biological half-life (T½) is related to the rate constant (λ) by:
$$\lambda = \frac{0.693}{T_{1/2}}$$

The effective half-life combines both physical decay and biological clearance:$$\frac{1}{T_{eff}} = \frac{1}{T_{physical}} + \frac{1}{T_{biological}}$$

2.(a) Discuss different types of diffusions.

Ans: Diffusion is the movement of molecules or ions from an area of higher concentration to an area of lower concentration. The types include:

1. Type of Molecules: Diffusion can involve different types of molecules, including oxygen, carbon dioxide, glucose, ions (e.g., sodium, potassium, calcium), and other small solutes.

2. Location of Diffusion:

• Intracellular Diffusion — Movement of molecules within the cytoplasm of a cell.
• Extracellular Diffusion — Movement of molecules between cells or within body fluids outside cells.

3. Membrane Permeability:

• Selective Diffusion — Some membranes allow only certain molecules to pass through while restricting others.
• Facilitated Diffusion — Diffusion facilitated by specific carrier proteins or channels in the cell membrane. Molecules still move down their gradient but require assistance (e.g., glucose transport).

4. Specific Processes:

• Pulmonary Diffusion — Exchange of gases (O₂ and CO₂) during respiration in the alveoli of the lungs.
• Renal Diffusion — Movement of solutes across kidney membranes during filtration and reabsorption in the nephrons.
• Intestinal Diffusion — Absorption of nutrients (glucose, amino acids, fatty acids) and water across the intestinal lining in the digestive system.

5. Factors influencing diffusion:

• Concentration Gradient: The difference in concentration between two areas that drives the movement of molecules.
• Temperature: Higher temperatures generally increase the rate of diffusion.
• Surface Area: Larger surface areas facilitate more diffusion.
• Distance: Shorter distances allow for faster diffusion.

2.(b) Define osmolarity and tonicity. Describe the fundamental factors of fluid flow.

Ans: Osmole is defined as one mole of a nondiffusing and nondissociating substance. One mole of a dissociating substance such as NaCl is equivalent to two osmoles.  The number of osmoles per liter of solution is called osmolarity. (Osmolality is a measure of the osmoles of solute per kilogram of solvent.)

• isosmotic to another has the same concentration of solute particles.
• Hyperosmotic is greater solute concentration;
• Hyposmotic is lower solute concentrationf

Physiological solutions are often expressed in milliosmoles (mOsm)

Tonicity: It refers to the effect of a solution on the shape of a cell.

• Isotonic — does not change cell shape; cell is in equilibrium
• Hypotonic — cell swells due to water moving into the cell
• Hypertonic — cell shrinks due to water moving out of the cell

Fundamental Factors of Fluid Flow:

2.(c) What is bio-fluid flow? Explain the key aspects.

Ans: Biofluid flow refers to the movement of fluids within living organisms, broadly categorized into blood and lymph.

Key Aspects:

3.(a) Explain optimization principle for fluid power.

Ans: The optimization principle for fluid transport is based on Murray’s Law, which asks whether there is a design principle that minimizes the cost of maintaining a fluid transport system.

The total power required to sustain continuous blood flow includes:
$$P_T = P_f + P_b$$

Where:

• Pf = power required to drive the flow (overcome friction)
• Pb = power required to maintain blood supply

Using Poiseuille’s Law:$$P_f = \frac{8LQ^2\mu}{\pi r^4}$$

The metabolic cost of maintaining blood (Pb) is proportional to blood volume:
$$P_b = \alpha_b \pi r^2 L$$

Therefore total power:$$P_T = \frac{8LQ^2\mu}{\pi r^4} + \alpha_b \pi r^2 L$$

Minimum work of circulation occurs at the radius where:
$$\frac{dP_T}{dr} = 0$$

As vessel radius increases, cost of flow declines while cost of blood volume increases — so an optimal radius exists that minimizes total power.

3.(b) Define and describe fluid power.

Ans: Power (Pw) is the rate at which work is done when a force F acts to accelerate a moving body. Units are watts or J/s.

For a translating process:
$$P_w = F \cdot V$$

For fluid systems, power is expressed in pressure and volume terms:
$$P_w = Q \cdot \Delta P$$

Where:

• Q = volumetric flow rate
• ΔP = pressure drop

The power required to move a fluid through a conduit is a function of:

• Fluid velocity
• Diameter of the conduit
• Fluid density and viscosity

Electrical analogy:$$P_{Electric} = I \cdot \Delta\phi$$

Where Δφ = voltage (volts) and I = current (amps)

Power output of the left ventricle:

• Cardiac output at rest ≈ 5 L/min
• Normal systolic blood pressure = 120 mmHg (1.60 × 10⁵ dyne/cm²)
• Right ventricle average systolic pressure = 25 mmHg; power output ≈ 0.278 W

3.(c) A Cardiac patient undergoes bypass surgery in which an artery is replaced by on that is 10% larger in diameter. What is the percentage change in blood flow in the artery, assuming all other factors remain the same?

Ans: Using Poiseuille’s Law: Q ∝ r⁴

New diameter is 10% larger → r₂ = 1.10 × r₁
$$\frac{Q_2}{Q_1} = (1.10)^4 = 1.4641$$Percentage increase = 46.41%

Blood flow increases by approximately 46.4%.

3.(d) Explain classical ethical theories.

Ans: Classical ethical theories are broadly classified into two major categories: Teleological and Deontological.

i) Teleological Theory — Utilitarianism:

“Telos” means goal or purpose in Greek.

Developed by Jeremy Bentham, utilitarianism states:

“Morality should guide people’s actions to produce a better world.”

Utilitarianism is classified into two categories:

• Act Utilitarianism — judges each act by its individual consequences
• Rule Utilitarianism — judges actions by whether following a rule produces the greatest overall good

Biomedical Example: Deciding which patient receives limited dialysis services based on who benefits society more.

ii) Deontological Theory — Duty-Based Ethics:

“Deon” means duty in Greek.

Immanuel Kant argued that actions are right or wrong in themselves — not based on consequences. He identified two imperatives:

• Hypothetical Imperative — consequence-dependent (“Do A to achieve B”)
• Categorical Imperative — duty-based regardless of outcome

Biomedical Examples: Subjects must never be used without informed consent. A physician must never lie to a patient

4(a) Define tension, compression or shear stress?

Ans:

• Tension — Stress that pulls or stretches a material along its axis
• Compression — Stress that squeezes or compresses a material along its axis
• Shear Stress — Stress acting parallel to a surface causing layers to slide

4.(b) Categories bone and soft tissue as typically having linear or nonlinear mechanical properties.

4.(c) List the applications of biomechanics.

Ans: Biomechanics principle:

4.(d) If a spring is considered as being equivalent to an electrical resistance where force = voltage and displacement = current, the when electrical component is equivalent to a dashpot?

Answer:

• Spring: Force = k × displacement → analogous to V = R × I (Resistor)
• Dashpot: Force = c × velocity = c × d(displacement)/dt

Since velocity = rate of change of displacement (analogous to rate of change of charge = current):
$$F = c\frac{dx}{dt} \Rightarrow V = L\frac{dI}{dt}$$

A dashpot is electrically equivalent to an Inductor (L)

4.(d) Define mechanical properties.

Answer:

5.(a) What property of blood is described by the Fahraeus-Lindquist effect?

Ans: The Fahraeus-Lindquist effect describes the reduction in apparent viscosity of blood as it flows through small diameter vessels (capillaries < 0.3 mm diameter).

According to Lecture 3, viscosity is a measure of a fluid’s resistance to flow — it determines the internal friction within the fluid. In microvessels, red blood cells migrate toward the center creating a cell-free plasma layer near the wall, reducing effective viscosity. This makes blood behave as a less viscous fluid in microcirculation compared to large vessels.

5.(b) How does resistance to blood flow depend upon the effective diameter of blood vessel? (Lecture 3)

Ans: Poiseuille’s Law:$$R = \frac{8\eta L}{\pi r^4}$$

• Resistance is inversely proportional to the 4th power of radius
• Doubling vessel diameter reduces resistance by a factor of 16
• Even a small reduction in diameter (e.g., atherosclerosis) dramatically increases resistance and reduces blood flow
• This is why vasodilation reduces resistance and vasoconstriction increases resistance

5.(c) Calculate Reynolds number — laminar or turbulent? (Lecture 3)

Answer:

From Lecture 3, the Reynolds Number predicts flow regime:
$$Re = \frac{\rho v D}{\eta}$$

Given:

• ρ = 1000 kg/m³
• v = 0.5 m/s
• D = 5 mm = 0.005 m
• η = 0.004 Pa·s

$$Re = \frac{1000 \times 0.5 \times 0.005}{0.004} = \frac{2.5}{0.004} = \mathbf{625}$$

Since Re = 625 < 2000 → the flow is LAMINAR

According to Lecture 3: “Laminar flow occurs at low flow rates and is characterized by predictable and stable flow patterns” — fluid particles move in smooth, parallel layers without crossing each other’s paths.

6.(a) Describe the major fluid flow characteristics.

Ans: Major fluid flow characteristics:

6.(b) Explain different energy forms.

Ans:

Bernoulli’s total energy equation:$$P + \frac{1}{2}\rho v^2 + \rho gh = \text{constant}$$

6.(c) How does the body maintain energy balance?

Ans: Energy Balance Equation:
$$\text{Energy In} = \text{Energy Out} + \text{Energy Stored}$$

Energy Input — from food (Lecture 5: Weir equation):

• Carbohydrates: 4 kcal/g
• Proteins: 4 kcal/g
• Fats: 9 kcal/g
• Every 1 mL of O₂ consumed releases 20 J of energy

Energy Output components:

Regulatory Mechanisms:

• Hypothalamus — Central energy regulator; controls hunger and satiety
• Insulin — Promotes glucose uptake and energy storage
• Glucagon — Promotes glycogen breakdown and energy release
• Leptin — Signals satiety from fat cells
• Ghrelin — Stimulates hunger

Cardiac energy example (Lecture 5):

• Cardiac output at rest = 5 L/min
• Systolic pressure = 120 mmHg → Pw = Ps × CO
• Right ventricle power output ≈ 0.278 W

7.(a) According to the Poiseuille equation, the flow rate Q in a tube is proportional to what powers of the radius and length? (Q ∝ rᵃ·Lᵇ: what are the numerical values of a and b?)

Answer:$$Q = \frac{\pi \Delta P \cdot r^4}{8\eta L}$$

Therefore:

• a = 4 (flow proportional to 4th power of radius)
• b = −1 (flow inversely proportional to length)

Physiological significance:

• A 10% increase in vessel radius increases flow by (1.1)⁴ = 46.4%
• Even minor stenosis (narrowing) dramatically reduces blood flow

7.(b) Write a short paragraph describing the difference between laminar and turbulent flow, and name two physiological conditions under which turbulent the flow might arises in the body.

Ans: Laminar flow is smooth and orderly, with fluid moving in parallel layers. The velocity profile is parabolic — maximum at the center, zero at vessel walls. It is energy efficient and silent.

Turbulent flow, by contrast, is chaotic and irregular with eddies and vortices forming in all directions, requiring significantly more energy and producing audible sounds.

The key distinction is the Reynolds number (Re):

• Laminar: Re < 2000
• Turbulent: Re > 4000

Two physiological conditions where turbulent flow arises:

7.(c) Explain pressure in the cardiovascular system.

Ans: Pressure is defined as force per unit area (SI unit: Pascal = N/m²). Other units include mmHg, atm, and dynes/cm².

Key cardiovascular pressures:

Important formulas:

Mean Arterial Pressure:
$$MAP = \frac{SBP + 2(DBP)}{3} \approx 93 \text{ mmHg}$$MAP=3SBP+2(DBP)​≈93 mmHg

Pulse Pressure:
$$PP = SBP – DBP = 40 \text{ mmHg (normal)}$$PP=SBP−DBP=40 mmHg (normal)

Although capillary diameter is small (7–10 μm), the total number of capillaries from a single arteriole is so large that the total cross-sectional area is significantly greater, so arterial blood pressure is largely dissipated by the time blood enters capillaries.

Starling’s three factors regulating fluid transfer across capillary membranes (Lecture 2):

7.(d) Deduce the constitutive equation properties of fluid in motion.

Ans: The constitutive equation for a Newtonian fluid (shear stress–strain rate relationship):
$$\tau = \eta \frac{dv}{dy}$$Where:

• τ = Shear stress (Pa)
• η = Dynamic viscosity (Pa·s)
• dv/dy = Velocity gradient / shear rate (s⁻¹)

Properties deduced:

8.(a) What is compliance requirements?

Ans: Compliance requirements refer to the rules, regulations, and standards that organizations and individuals must adhere to in various fields including healthcare, finance, IT, and environmental protection. They are put in place to ensure legal, ethical, and safe practices within a given industry.

In the medical device industry specifically:

• New product development activities from concept, design, and manufacturing to sales and distribution must be documented in a controlled manner
• This is detailed in the Quality System Regulation (QSR) 21 of the Code of Federal Regulations (CFR) 820
• The FDA publishes guidance documents stating current thinking to assist manufacturers in determining safety and effectiveness

Five categories of compliance issues in biomedical practice (Lecture 6, Figure 11.1):

8.(b) Explain the functions of IEC.

Ans: The International Electromedical Commission (IEC) is one of three international bodies responsible for planning, developing, and adopting international standards. The IEC is specifically responsible for the electrotechnical sector.

Key functions:

8.(c) Narrate Belmont Report.

Ans: The Belmont Report is a foundational document in research ethics. It was issued in 1979 by the U.S. National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research, in response to ethical concerns arising from human subjects research — most notably the Tuskegee Syphilis Study. It is named after the Belmont Conference Center in Maryland where discussions leading to its development took place.

The report identifies three fundamental ethical principles:

1. Respect for Persons (Autonomy)

• Emphasizes respecting the autonomy and dignity of individuals
• Requires Informed Consent: researchers must obtain voluntary, informed consent ensuring participants understand purpose, procedures, risks, and benefits
• Special protections for individuals with diminished autonomy (children, cognitively impaired)
• Researchers must protect privacy and confidentiality of participants

2. Beneficence

• Obligates researchers to maximize benefits while minimizing harm
• Requires careful risk-benefit assessment — expected benefits must justify potential harm
• Special protections for vulnerable populations (children, prisoners, pregnant women)

3. Justice

• Benefits and burdens of research must be distributed fairly and equitably
• Researchers must avoid unjust discrimination in selecting participants
• Selection process must be fair and unbiased — vulnerable groups must not be exploited

Impact:

• Provided the foundational framework for the Common Rule (45 CFR 46) governing federally funded research in the USA
• Significant influence on international research ethics guidelines including the Declaration of Helsinki
• Basis for all Institutional Review Boards (IRBs) globally

8.(d) Describe the major transportation level of molecules in the human body.

Ans: The transport of molecules occurs at five levels:

1. Across Different Tissues

• Molecules move between distinct tissue types via diffusion and bulk flow
• Example: liver cells secrete albumin which moves across tissue barriers into blood

2. Between Different Cell Types

• Exchange between functionally different cells
• Example: capillary endothelial cells exchange nutrients with surrounding muscle or nerve cells

3. Between Cells of the Same Type

• Communication and exchange between identical cells within a tissue
• Example: gap junctions between cardiac muscle cells for electrical conduction

4. From Outside to Inside the Cell (Transmembrane Transport)

• Simple Diffusion — O₂, CO₂, lipids move freely down concentration gradients
• Facilitated Diffusion — Glucose, amino acids use carrier proteins (no energy)
• Active Transport — Na⁺/K⁺ pump moves ions against gradient (requires ATP)
• Osmosis — Water moves across semipermeable membranes
• Endocytosis/Exocytosis — Large molecules transported via vesicles

5. Within a Cell (Intracellular Transport)

• Molecules move within cytoplasm by intracellular diffusion
• Vesicular transport moves proteins from endoplasmic reticulum to Golgi apparatus

Supporting transport systems (Lecture 2):

Fluid compartments involved (Lecture 2):

• Intracellular fluid — Inside cells
• Plasma — Within blood vessels and heart
• Interstitial fluid — Spaces between tissues
• Transcellular fluid — CSF, bladder fluid, GI tract fluid, sweat

A floating ice block moves on water thanks to its own melting.

Inclined bottoms create underwater jets as cold meltwater sinks, pushing the block. Could iceberg motion be partly self-driven?

🔗 https://physics.aps.org/articles/v19/36

#IcePhysics #FluidFlow #SelfPropulsion #MeltingDynamics #Oceanography

#SteveMould - Can #Water #Solve A #Maze?

https://www.youtube.com/watch?v=81ebWToAnvA&ab_channel=SteveMould

#Math #Maths #Science #Physics #Fluid #Fluids #FluidDynamics #Flow #FluidFlow #Path #SolvePath #SurfaceTension

Referenced link: https://medicalxpress.com/news/2023-03-fluid-brain-sensory.html
Discuss on https://discu.eu/q/https://medicalxpress.com/news/2023-03-fluid-brain-sensory.html

Originally posted by Phys.org / @physorg_com: http://nitter.platypush.tech/medical_xpress/status/1641500564088389636#m

RT by @physorg_com: #Fluidflow in the #brain can be manipulated by sensory stimulation @plos @PLOSBiology https://journals.plos.org/plosbiology/article https://medicalxpress.com/news/2023-03-fluid-brain-sensory.html