Diagnostic Tools Flashcards
two types of clinical diagnostic tech
molecular and medical imaging diagnosis
technique used to analyze biological markers in the genome and proteome the individual’s genetic code and how their cells express their genes as proteins
molecular diagnosis
technique and process used to create images of the human body for clinical purposes or medical science
medical imaging diagnosis
functions of mass spectrometry
-measures mass better than any other technique and can give info about chem structures
what are mass measurements good for?
to identify, verify and quantitate: metabolites, recomb proteins, proteins isolated from natural sources…etc
how does mass spectrometer work
ion source: makes ions –> mass analyzer: separates ions based on their mass-charge ratio –> mass spectrum: presents info
key specifications of mass analyzers
resolution, mass measurement, accuracy and sensitivity
detection of the various pathogenic mutations in DNA and/or RNA samples in order to facilitate detection, diagnosis, subclassfication, prognosis and monitoring response to therapy
nucleic-acid based molecular diagnosis of human disorders
a genetic disease w/c is caused by a single nucleotide change in the 6th amino acid of the beta chain of hemog.
sicle cell anemia
who and when is the PCR invented
Kary Mullins (1985); noble prize in ‘93
Principles of PCR
- Temperature cycling: denaturation - 94, annealing -55, extension - 72
- every cycle DNA between primers is duplicated
* does exponential amplification
components of PCR rxn
- template DNA
- flanking primers
- thermo-stable polymerase (Taq polymerase)
- dNTP
- PCR buffer
- thermocycler
genetic disorder characterized by abnormal body movements and reduced mental abilities; caused by mutation of Huntingtin (HD) gene
huntington’s disease
individuals w/HD vs. non-HD individuals
non-HD: CAG repeats less than 30x
HD: CAG repeats more than 36x
How can someone determine if they have HD?
PCR can be performed; the DNA is amplified via PCR and sequenced and the number of the trinucleotide repeats is counted
retrovirus that attacks the immune system
HIV
principles of HIV test
HIV tests rely on PCR w. primers that will only amplify a section of the viral DNA found in an infected bodily fluid; pcr product = HIV+, no pcr prod = HIV-
accurate absolute quantification of template molecules by separation of target molecules and counting statistics
droplet digital PCR
Goals of Human Genome Project
- to identify all of the genes in human DNA
- to determine the sequences of the 3 billion bases that make up human DNA
- to create databases
- to develop tools for data analysis
- to address the ethical, legal, and social issues that arise from genome research
implications of genome decipher
epigenetics -> gene regulation -> RNA and protein markers
allows analysis of thousands of gene in one experiment
DNA microarray
Dideoxy (SAnger) method
- denaturation
- primer attachment and extension of bases
- termination
- gel electrophoresis
sequencing that performs large-scale sequencing of DNA by DNA fragmentation, duplication into a vector and individual sequencing
shotgun sequencing (assembled electronically)
NGS Platforms
pyrosequencing sequencing by ligation H+ ion generation/ion torrent reversibly dye terminators massive parallel sequencing illumina flow cell platform
massively parallel seq.
bridge amplification, clonal expansion
illumina flowcell platform
sequence by synthesis, bridge amp.
ion torrent seq
semiconductor sequencing based on the detection of H+ions, amp by emulsion PCR
Who discovered xrays?
Wilhe, m Conrad Roentgen (Nov. 8, 1985); 1901 novel prize for phys
form of EM radiaion that penetrate matter and can cause fluorescence of some atoms, expose film and biological damage
x-ray
parts of x ray tube
- cathode - electron source
- tungsten filament
- negatively charged concave cup around filament
- focal spot
- thermonic emission
- anode -target w/c electrons strike
- tungsten target
- stationary - anode in large block of Copper
- rotating - disc rotates w.c spreads e- around target thus less heat build uo
problems with conventional radiography tech.
- inability to distinguish soft body tissue because of limited contrast
- inability to resolve spatially structures along the x-ray propagation axis resulting in a loss of depth information
forms of diagnostic imaging
CT, ultrasound imaging, MRI
uses x-rays to produce an image/cross sectional imaging; requires computer manipulation of images
computed tomography
principle of CT
principle that an image of an unknown object can be obtained if one has an infinite number of projections through the object
uses 3D imaging tech. to evaluate the vascular system
CT angiography
advantages of CTA over conventional angio
- img reconstruction w/o the use of exposure to radiation or IV contrast
- overlying structures can be eliminated
- does not require arterial puncture
used in most CT imging to distinguish normal anatomy from pathology
Contrast media - ex: iodine based IV contrast
principles of utrasound
high freq. sound is transmitted into the body, usually in very short pulses;
returning echoes are analyzed to create an image; reflections are due to variations in acoustic impedance; uses Doppler effect
Capabilities of ultrasound
provides real-time imging
- color doppler
- non-toxic
- inexpensive
limitations of ultrasound
- poor or no imaging through bone,gas
- operator dependant image quality
- images more difficult to interpret than CT
uses strong magnetic field and radiofreq. waves to image structures; no ionizing radiation and great for soft tissue
MRI
principle if MRI
- Radio freq, is passed through the coils (in the target area) that excites H+
- The gradient magnets are then activated in the main magnet and alter the magnetic field in the area that is being scanned, causing H+ to spin
- Radio freq. is turned off and H+ return to their natural state
- protons align themselves and the protons that are not cancelled create a signal and are the ones responsible for the image
role of contrast dye in MRI
makes target area stand out and show irregularities; blocks x-ray photons from reaching the film, thus showing different densities in the tissue
MRI measures what neural parameters
changes in phosphorus metabolism
- blood flow
- blood volume
- blood oxygenation
