#medical imaging

General Biology - Part 2

Which one of the following is a frequently used radio-opaque dye?

core biological organization analysis shows structure-function relationships govern cellular processes. Consequently Barium sulphate emerges as the valid choice since it integrates fundamental principles, aligning with established principles in general biology literature.

Ref: Campbell et al., Biology, 11th Edition, Chapter 2, Chemical Basis of Life, discusses fundamental biological principles and molecular organization providing broad foundation for life sciences understanding.

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Microbiology and Immunology

Which one of the following imaging techniques is non-invasive?

The principle of genetic engineering explains that vector design and pathway extension enable vitamin production. Hence Ultrasound imaging fits best because it utilizes recombinant DNA and metabolic engineering, as documented in authoritative sources on biotechnology.

Ref: Primrose and Twyman, Principles of Gene Manipulation and Genomics, 8th Edition, Chapter 2, Recombinant DNA Technology, discusses Golden Rice development, exogenous genes, metabolic engineering and vitamin A pathway extension supporting applications.

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Biochemistry - Part 2

The utility of positron emission tomography to diagnose tumors is based on

This outcome reflects enzyme catalysis and lipid structure, where substrate affinity, transition state stabilization and phospholipid composition govern function. Option B captures this correctly because it reflects catalytic efficiency and membrane organization, consistent with textbook descriptions and experimental observations in biochemistry.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 6, Enzyme Kinetics and Regulation, discusses Michaelis-Menten equation, transition state stabilization and allosteric control supporting enzyme function.

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Ultraviolet, X-rays, Gamma Rays and Their Properties

Why do X-rays require careful handling in medical applications?

**X-rays in medicine** treat certain cancers because high-energy photons ionize and damage DNA of malignant cells, also imaging because bones absorb more than tissue, contrast. Gamma rays from Co-60 used for radiotherapy, energy ≈1.17 and 1.33 MeV, highly penetrating. X-rays have high energy and penetrating power, which can damage living tissues and cause cellular mutations, necessitating careful handling to avoid overexposure. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Potential tissue damage, illustrating EM wave transverse nature and Ma

Ref: NCERT > Physics Book > Electromagnetic Waves > Ultraviolet, X-rays, Gamma Rays and Their Properties

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Ultraviolet, X-rays, Gamma Rays and Their Properties

What precaution must be taken when using X-rays in medical applications?

**Ultraviolet** λ≈10-400 nm, produced by atomic transitions and Sun, causes fluorescence, sterilization, harmful to eyes/skin, absorbed by ozone layer. **X-rays** λ≈10⁻² to 10 nm, produced by rapid deceleration of energetic electrons in X-ray tube, used in medicine for diagnosis (shadow of bones) and cancer therapy due to high ionization and penetration, detected by photographic film and Geiger counter. The document warns that X-rays can damage or destroy living tissues, so care must be taken to avoid unnecessary or overexposure. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classifi

Ref: NCERT > Physics Book > Electromagnetic Waves > Ultraviolet, X-rays, Gamma Rays and Their Properties

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Ultraviolet, X-rays, Gamma Rays and Their Properties

Which of the following is used to detect X-rays?

**Ultraviolet** λ≈10-400 nm, produced by atomic transitions and Sun, causes fluorescence, sterilization, harmful to eyes/skin, absorbed by ozone layer. **X-rays** λ≈10⁻² to 10 nm, produced by rapid deceleration of energetic electrons in X-ray tube, used in medicine for diagnosis (shadow of bones) and cancer therapy due to high ionization and penetration, detected by photographic film and Geiger counter. The document lists photographic film, Geiger tubes, and ionization chambers as detectors for X-rays. Geiger tubes are a common choice. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum cl

Ref: NCERT > Physics Book > Electromagnetic Waves > Ultraviolet, X-rays, Gamma Rays and Their Properties

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Electrophysiological methods

Which imaging technique can distinguish soft tissues best?

Distinguishing soft tissues requires discrimination based on water content, fat fraction and macromolecular environment rather than electron density. Magnetic resonance imaging excels because proton relaxation parameters T1 and T2 vary substantially between gray matter, white matter, edema, tumor infiltration, muscle and ligament, yielding intrinsic contrast adjustable via pulse sequences. Computed tomography differentiates mainly by X-ray attenuation, limited in soft tissue. PET reflects metabolism with coarse anatomy, EEG contains no anatomical image. Therefore MRI provides superior soft-tis

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Electrophysiological methods

Which imaging method requires a fasting patient due to tracer uptake?

Positron emission tomography with fluorodeoxyglucose quantifies glucose metabolism, so systemic glucose handling critically influences diagnostic quality. In postprandial state, elevated blood glucose competes directly with tracer for transporter uptake, while insulin surge drives FDG into skeletal muscles and fat, increasing diffuse background and obscuring cerebral or tumor hypermetabolism. Maintaining 4-6 hour fasting keeps serum glucose and insulin low, maximizing target-to-background contrast and enabling standardized uptake value quantification. Magnetic resonance, EEG and diffusion tens

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Electrophysiological methods

Which method can image the deepest brain structures non-invasively?

Depth penetration with noninvasive safety is crucial for central brain evaluation. Magnetic resonance imaging achieves this because static magnetic fields and radiofrequency pulses traverse scalp and skull without attenuation or ionizing damage, exciting protons everywhere. Volume excitation and three-dimensional gradient encoding reconstruct whole brain including brainstem, thalamus, hypothalamus and mesial temporal lobes with high contrast. EEG suffers from inverse problem limiting deep source localization, CT uses ionizing X-rays and has poor soft-tissue differentiation, PET has limited res

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Electrophysiological methods

Which of the following detects changes in magnetic properties of hemoglobin?

Functional magnetic resonance imaging exploits endogenous contrast from hemoglobin oxygenation state without exogenous tracer. Deoxyhemoglobin contains four unpaired electrons in ferrous heme, making it paramagnetic, distorting local magnetic field and accelerating transverse relaxation, reducing T2* signal. Oxyhemoglobin with bound oxygen is diamagnetic and preserves homogeneity. Activation increases cerebral blood flow delivering excess oxyhemoglobin, lowering deoxyhemoglobin concentration and enhancing MRI intensity. Computed tomography relies on X-ray attenuation, EEG records voltage, PET

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Electrophysiological methods

Which method utilizes gamma rays detected singly to create images?

Gamma-ray based tomographic methods differ fundamentally by detection scheme and collimation. Single photon emission computed tomography uses isotopes like technetium-99m, iodine-123 or xenon-133 decaying by emission of single gamma photons randomly oriented. Lead collimators absorb oblique photons, permitting only perpendicular photons to reach scintillation crystal, enabling three-dimensional reconstruction of cerebral perfusion or dopamine transporter distribution. Positron emission tomography requires coincident detection of paired annihilation photons, computed tomography generates extern

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Electrophysiological methods

In a CT scanner, the cross-sectional image is reconstructed from:

Computed tomography employs a rotating gantry containing X-ray tube and opposite detector array. As tube circles patient, numerous fan-shaped X-ray projections traverse head from many angles, attenuated differentially by bone, soft tissue, blood and cerebrospinal fluid according to electron density and atomic number. Detectors measure remaining intensity, generating attenuation profiles. Filtered back-projection or iterative algorithms mathematically reconstruct these one-dimensional projections into two-dimensional axial cross-sectional images. Thus image contrast originates entirely from X-r

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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