Skip to content
Login Register

#imaging techniques

2 public questions tagged with this topic.

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 senses positron decay, none sense magnetic properties of hemoglobin differently.

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.

View Details
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 external X-rays, MRI uses radiofrequency from protons, so singly detected gamma imaging characterizes SPECT uniquely.

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.

View Details