Radiology and Imaging Techniques Quiz

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Questions and Answers

What is a critical feature of a reporter gene probe?

It should remain unchanged in important structural regions. (correct)

It should alter the gene expression levels significantly.

It must produce a significant increase in molecular weight.

It should enhance the structural parts of the molecule.

Which of the following statements about optical imaging is true?

It primarily focuses on morphological imaging.

It operates within the wavelength range of 300-800 nm. (correct)

It provides low sensitivity at high concentrations.

It uses radiofrequency waves for imaging.

What is a significant advantage of ultrasound imaging compared to optical imaging?

Higher sensitivity in detecting low concentrations.

Ability to perform functional imaging.

High spatial resolution and fast processing. (correct)

Use of fluorochromes for detection.

Which of the following accurately describes the resolution of optical imaging?

1-5 mm Signup and view all the answers

What limitation does optical imaging face in terms of tissue penetration?

It has low penetration depth in tissues. Signup and view all the answers

How does ultrasound imaging produce an image?

By reflecting waves off an object and measuring the return signal. Signup and view all the answers

Which application is not typically associated with optical imaging?

Vascular imaging Signup and view all the answers

What is a primary disadvantage of ultrasound compared to optical imaging?

It has low sensitivity. Signup and view all the answers

What defines the specific activity of a radionuclide?

Radioactivity per unit mass of a radionuclide. Signup and view all the answers

Which statement is true regarding effective half-life?

It is influenced by both biological transport and radioactive decay. Signup and view all the answers

How is the radioactive decay process described?

A random process of unstable nuclei undergoing transformation. Signup and view all the answers

What is the relationship between physical half-life and biological half-life when calculating effective half-life?

If they are equal, effective half-life is equal to the physical half-life. Signup and view all the answers

What does radioactivity measure?

Nuclear disintegrations per second. Signup and view all the answers

Which type of decay involves the emission of an electron?

Beta decay. Signup and view all the answers

What is the maximum allowable time from the production of a radionuclide to its application?

Up to 3 T1/2. Signup and view all the answers

In the equation for calculating effective half-life, what does the term 2 signify?

The ratio of the physical and biological half-lives. Signup and view all the answers

What is the half-life of 82Rb+ used in perfusion imaging?

10 minutes Signup and view all the answers

Which property of 82Rb+ contributes to its high extraction fraction in the myocardium?

It is a monovalent K+ analogue Signup and view all the answers

What is the assumed uptake mechanism for [13N]NH3 in myocardial imaging?

Transported by Na+/K+-ATPase pump and passive diffusion Signup and view all the answers

Which of the following tracers has a shorter physical half-life than 82Rb+?

[13N]NH3 Signup and view all the answers

Which tracer is produced by a generator?

82Rb+ Signup and view all the answers

What is the metabolic fate of ammonium from [13N]NH3 in cells?

Converted to glutamate and glutamine Signup and view all the answers

Which perfusion tracer provides high image resolution due to its β+-Energy level?

82Rb+ Signup and view all the answers

What is a key feature of [15O]H2O in perfusion imaging?

It has a mean positron range of 0.492 MeV Signup and view all the answers

Which mechanism of accumulation involves the incorporation of antibodies to target specific antigens?

Antigen-antibody binding Signup and view all the answers

What is the most stable oxidation state for Technetium-99m?

+7 Signup and view all the answers

Which of the following is NOT a mechanism of accumulation for a Tc-99m radiotracer?

Electrostatic repulsion Signup and view all the answers

Which Tc-99m radiopharmaceutical is used for liver scintigraphy?

99mTc-HIDA2 Signup and view all the answers

What is the required energy emitted during the decay of Technetium-99m?

140 keV Signup and view all the answers

Which oxidation state of Technetium-99m is involved in penetrating the blood-brain barrier?

+5 Signup and view all the answers

What is the half-life of the 99Mo/99mTc generator?

6 hours Signup and view all the answers

In terms of complex geometry, what primarily influences the structures formed by Technetium-99m?

Oxidation state Signup and view all the answers

What type of Tc-99m radiopharmaceutical can be used for thyroid imaging?

99mTc-pertechnetate Signup and view all the answers

Which mechanism helps in the uptake of Tc-99m radiotracers through the action of lipophilic groups?

Metabolic trapping Signup and view all the answers

What is the half-life of the tracer [18F]Flurpiridaz?

110 minutes Signup and view all the answers

Which uptake mechanism is involved with [18F]Flurpiridaz?

Passive diffusion Signup and view all the answers

What is a key property of an ideal tracer for measuring myocardial blood flow?

High first-pass extraction fraction Signup and view all the answers

Why is 18F-FDG considered unsuitable for myocardial blood flow measurement?

Its uptake is independent of blood flow. Signup and view all the answers

What makes [15O]H2O the gold standard for quantifying myocardial blood flow?

It exhibits linear tracer extraction efficiency. Signup and view all the answers

What is a noteworthy characteristic of the uptake mechanism of [18F]Flurpiridaz?

High retention in cardiac tissue Signup and view all the answers

How is imaging quality for tracers assessed in myocardial blood flow measurement?

By tracer extraction efficiency and retention Signup and view all the answers

What significant impact does revascularization have on patients with myocardial viability?

It leads to a 79.6% reduction in mortality. Signup and view all the answers

What is the primary role of Carbidopa in Parkinson’s disease treatment?

Inhibits peripheral AADC, enhancing L-DOPA efficacy Signup and view all the answers

In which context is [11C]Raclopride used?

To measure changes in dopamine levels Signup and view all the answers

Which radiolabeled compound is best associated with dopamine transporter imaging?

[123I]FP-CIT Signup and view all the answers

What characterizes the SPECT findings in idiopathic Parkinson's disease?

Dot-shaped reduction in tracer uptake Signup and view all the answers

How is cerebral glucose metabolism related to neuronal function?

It is a suitable marker of neuronal dysfunction. Signup and view all the answers

Which statement is true about the uptake of [18F]FDG in the brain?

It is trapped by phosphorylation through hexokinase. Signup and view all the answers

What change is observed in D2 receptor availability after prolonged drug detoxification?

Decreased receptor availability Signup and view all the answers

What modification was made to the cocaine structure to stabilize its radiolabeled tracers?

Cleavage of the COO group between the rings Signup and view all the answers

Study Notes

Molecular Imaging

Molecular imaging is an intersection of molecular biology and medicine, enabling the visualization of physiological processes and cellular functions
Molecular imaging techniques combine structural information and molecular signatures
It provides relevant information for drug discovery and development

Biomarker

A biomarker is a laboratory measurement that can reflect the activity of a disease process
It can predict drug efficacy but might not always predict therapeutic outcome
It should provide information about a critical path in the disease's development

Imaging principles

Imaging comprises: Probe → Matter interaction → Detection → Image production
Imaging scale: size (nm → m), time (ms → y)

General Concepts in Molecular Imaging

Morphological imaging: Identifies the structure of a biological system
Functional imaging: Identifies cellular signatures and events in living systems
Hybrid imaging: Combines morphological and functional imaging
Label-free/Probe-free Imaging: Target-unspecific, predominantly for morphological imaging
Probe-based imaging: Target-specific, predominantly for functional imaging

Molecular Probe design

Reporter probes, methods, and reporter genes

Direct (targeted) reporter probes

Label part: Radionuclide, Fluorescent molecule, Paramagnetic metal complex or Air bubble
Pharmacophore: small molecule, peptides, antibody, oligonucleotide, macromolecule, etc.
Activatable reporter probes involve a non-active substrate, activated upon binding the target (i.e., FRET, BRET)

Direct method

Labelled drug lead: Structurally identical or very similar, pharmacological and pharmacokinetic characteristics similar, shares the same target (e.g., [11C]-Erlotinib)

Indirect/surrogate method(s)

Surrogate probe: Structurally different but competes for same target (e.g., Eliprodil → [11C]NB1)
Surrogate probe and surrogate target: Structurally unrelated, different target(i.e., [18F]FDG (Glut1) → Tyrosin kinase receptor)

Reporter gene

Foreign gene is introduced into cell genome, a stimulus expresses the gene, detected by reporter probe or the protein's own signal.

Optical imaging

Probe: Photon (λ = 300-800 nm)
Matter interaction: Absorption, penetration, scattering
Modalities: Fluor-, Biolumin-, Phosphorescence
Resolution: 1-5/1 mm
Chemical Probe: Near-infrared fluorochromes (NIR)
Application: Cellular and pre-clinical imaging
Advantages: High sensitivity (10-⁹ M), functional imaging, no ionizing radiation.
Limitations: Only pre-clinical, low penetration in tissue, high absorption in tissue, mostly 2D
Function: Fluorophore excitation, relaxation, fluorescence after excitation (e.g., FRET, BRET)

Ultrasound

Probe: Radiofrequency wave (λ < 1.5 mm)
Matter interaction: Reflection
Modalities: Ultrasonography
Resolution: 50-100 μm
Chemical Probe: None or microbubbles
Application: Vascular and interventional imaging, pregnancy, thoracentesis
Advantages: High spatial resolution, inexpensive, 4D, no ionizing radiation, fast, non-invasive.
Limitations: Low sensitivity (10-⁴ M), limited penetration depth, predominantly morphological imaging, inability to image through air pockets or bone, quality depends on skill.
Function: Wave reflection and distance measurement

MRI

Probe: Radiofrequency waves (non-ionizing)
Matter interaction: Nuclear spin transition
Modalities: Magnetic resonance imaging (MRI), spectroscopy (MRS), functional MRI (fMRI), hyperpolarized
Resolution: 50-100 μm
Chemical Probe: None (H₂O in the body) or paramagnetic contrast agents (Gd-, Fe-complex)
Application: Neurology, oncology, cardiology, tumor, brain, spine, musculoskeletal system
Advantages: Excellent soft tissue contrast, high spatial resolution, non-invasive.
Limitations: Low sensitivity (10-⁴ M), poor hard matter contrast, predominantly morphological imaging. expensive, long scan times, strong magnetic field (e.g. contraindicated for patients with pacemakers).

X-ray, CT

Probe: X-ray photons
Matter interaction: Transmission, absorption, scatter
Modalities: X-ray (2D), computer tomography (CT, 3D), phase-contrast X-ray/CT
Resolution: 10-50 μm
Chemical Probe: None or contrast agents
Application: Trauma, oncology, cardiology etc; bone trauma, infarction, tumors, calcification; cardiac, angiography, fibrosis, pulmonary embolism
Advantages: Highest spatial resolution, inexpensive, fast, high contrast resolution, non-invasive.
Limitations: Ionizing radiation (dose), poor soft tissue contrast, low sensitivity (10³ M), morphological imaging, radiation exposure
Examples of probes: Compounds containing heavier elements (I, Ba, Th)

PET, SPECT

PET: Positron emission tomography
SPECT: Single photon emission computed tomography
Probe: y-ray, positron → y-ray
Matter interaction: Transmission, absorption (annihilation), scattering
Modalities: Positron emission tomography (PET), Single photon emission computer tomography (SPECT), scintigraphy (2D)
Resolution: 5-10 mm
Chemical Probe: Radiotracers, radiopharmaceuticals (radiolabelled molecules)
Application: Neurology, oncology, cardiology, drug development, animals, various organs, function (e.g., liver, kidney, thyroid, heart, lung)
Advantages: Highest sensitivity, high functioning imaging, microdosing.
Limitations: Ionizing radiation (dose), very expensive. poor spatial resolution
Typical probes: Probes are needed and essential, radiolabelled molecules

Radiopharmacy

Radiopharmacy: Preparation, characterization, and QC of radioactive materials for human use; molecular imaging, and radionuclide therapy
Radiopharmaceutical: Medicinal product containing a chemical/biological part with a radionuclide/isotope. No pharmacological effect.
Radioactive decay: Random process of unstable nuclei, release excess energy in form of ionizing radiation
Radioactivity (A): Nuclear disintegrations per second Specific activity (Aspec): Radioactivity per unit mass of a radionuclide
Half-life (T½): Time for a quantity of radionuclide to decrease to half its original quantity
Effective half-life (effT½): Reduced lifetime of a radiopharmaceutical in an organ

Types of decay

Chart, range, shielding, Crossfire effect

SUV

Factor determining tracer kinetics, Compartment models (all types), Reverse and irreversible binding, How to choose a model

Standard Uptake Value

SUV = Bq in tissue or organs / (Bq injected dose/g body weight)
SUV >1 in region of interest → heterogeneous tissues distribution; <1 → regions lower radioisotope concentrations
Kinetics is needed to determine tracer kinetics, compartment model, and binding (reversible or irreversible)

Compartment model curves

Reference tissue curve
Specific and non-specific binding

Types of radiation

Ionizing radiation, LET, Gy and Sv, WR and WT

Dosimetry

Absorbed dose, Equivalent dose, Effective dose

Radiation, dose-effects and limitations

Internal Radiation Dosimetry

Radiolabelling concepts Isotope*(Bio)isosteres

Type of chemistry - Covalent bonds: direct labelling of radiocarbon or radiohalogens, 'organic' radionuclides
Type of chemistry - Coordinative bonds: labelling using metal chelators of peptides or proteins or radiometal labelling.

Quality Control of Radiopharmaceuticals

Radionuclide purity (isotopic purity): Fraction of total radioactivity coming from desired radionuclide.
Radiochemical purity: Fraction of total radioactivity coming from desired chemical form (e.g., [¹⁸F]FDOPA, [⁹⁹mTcO₄⁻]), determined by HPLC or TLC.
Chemical purity: Absence of undesired contaminants (e.g., Al³⁺).
Biological purity: Absence of pyrogens (e.g., endotoxins) and sterility (absence of microorganism, e.g., bacteria).

General Composition of a Kit

Components: Active component/ligand, reducing agent, auxiliary components, auxiliary ligand
Possible mechanisms of accumulation of TC-99m Radiotracer: Passive transport/diffusion, lons transport, Antigen-antibody binding, Adsorption/Chemisorption, Sequestering of cells, Metabolic trapping.

99mTc-Chemistry

Selected Tc-99m Radiopharmaceuticals
99mTc (and 186/188Re): Structure, Complex geometry, Production

[99mTc]Tc-Sestamibi, [99mTc]Tetrofosmin

[99mTc]MAG3, [99mTc]MDP, [99mTc]Medronate

[99mTc/186Re]-MDP, [99mTc/186Re]-EDTMP, [89Sr/223Ra]-analogues

[11C]Methylation reactions

[11C]CO2 reactions

F-18 production

Reaction summary: Aliphatic nucleophilic 18F-substitution, Aromatic nucleophilic 18F-substitution

Aliphatic Nucleophilic F-substitution

Aromatic Nucleophilic F-substitution

Neurology (Brain cuts)

Biological targets: AADC, D2 receptors, DAT transporter, misfolded proteins.
Metabolism: glucose metabolism trace [¹⁸F]FDG.
Perfusion: [¹⁵O]H₂O, ⁹⁹mTc-HMPAO, ⁹⁹mTc-ECD, ⁹⁹mTcO₄⁻.

Neurology (Dopaminergic System)

Dopamine synthesis: ¹⁸F]FDOPA
D2 Receptor: ¹¹C]Raclopride

Neurology (Alzheimer's Disease)

Misfolded proteins: Beta-amyloid, Tau
Amyloid PET Tracers: ¹⁸F]flutemetamol, ¹¹C]PIB, ¹⁸F]Florbetapir
Tau PET Tracers: ¹⁸F]RO948, ¹⁸F]FTP, ¹⁸F]Flortaucipir

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Description

Test your knowledge on radiology and various imaging techniques, including optical imaging and ultrasound. This quiz covers critical concepts such as the features of reporter gene probes, resolution, limitations, and applications of different imaging modalities.