Introduction to Medical Imaging Flashcards
who discovered xray?
Wilhelm Röentgen
Coolidge Tube
Dr. William Coolidge
Produced by focusing a beam of high energy electrons onto a tungsten target
X-rays
what does xray use?
Electromagnetic radiation
Cathode energy releases in the form of
electrons
Advantages of digital over conventional radiography
Magnification of areas of interest
Alteration of density
Measurements of distances and angles
Cassettes are inserted in the laser reader
ADC produces an image
Computed Radiography
detector screen of digital radiography contains__
silicon detector
Produce electrical signal when exposed to x-rays
digital radiography
- Large computer storage facility
- Images form different modalities are stored
- Allow instant recall and display of patients’ imaging study
- Easy accessibility for other hospital facilities
PACS
Constant stream of X-rays
fluoroscopy
uses of fluoroscopy??
- Angiography and interventional radiology
- Contrast studies of the GI tract
- Guidance of therapeutic injections and arthrograms
- Screening in theatre
- General surgery, urology, orthopedic surgery
water insoluble contrast material
barium
uses of contrast materials
GI tract studies
CT scan
DSA
Arthrography
Cross-sectional imaging with the use of .x-rays
CT scan
High attenuation
Light grey or white
High density
Low attenuation
black
Low density
Alteration of grey-scale settings
Image information can be manipulated to display various tissue of the body.
Windows
inventor of CT scan
Godfrey hounsfield
Relative density of an area of interest can be measured electronically
attenuation value
CT number of bone
+1000
used in Differentiation of normal blood vessels from abnormal masses (hilar vessels versus lymph nodes
Intravenous contrast
Differentiation of normal enhancing bowel loops from abnormal masses or fluid collections
Diagnosis of perforation of the gastrointestinal tract
Diagnosis of leaking surgical anastomose
oral contrast
Detailed examination of the pelvis and the distal large bowel.
Rectal contrast
Tube and detectors rotate as the patient passes through on the scanning table.
Multiple detectors
16 to 320 row scanners
Multidetector Row CT scan (MDCT)
uses High-frequency sound waves
Ultrasound
basic component of ultrasound
Piezoelectric crystals
conversion of sound into mechanical energy
Piezoelectric effect
Varying sound wave reflection
Echogenicity
Reflect more sound waves
White or light grey
Hyperechoic
Reflect less sound waves
Dark grey
Hypoechoic
appears black in utz
anechoic
Tissues distally receive more sound waves
Acoustic Enhancment
Reverse effect of acoustic enhancement - appears Darker Gas containing bowel Gallstones Renal stones Breast malignancy
acoustic shadowing
Uses non-ionizing radiation
Magnetic Resonance Imaging
Magnetic strength
tesla
increased density in MRI
appears darker
the primary nuclei used for mri imaging is the
hydrogen atom called proton
used to excite the proton which resonate and emit varying signals which are received, digitized and display as images
radiowave
the process by which the spins in the sample come to equilibrium with the surroundings
Relaxation
structures that appear white on T1
Fat Subacute hemorrhage Melanin Protein-rich fluid Slowly flowing blood Paramagnetic substances: gadolinium, manganese, copper Calcification (rarely) Laminar necrosis of cerebral infarction
structures that appear dark on T1
Increased water
*edema, tumor, infarction, inflammation, infection, hemorrhage (hyperacute or chronic)
Low proton density, calcification
Flow void
APPEARS BRIGHT IN T2
Increased water
edema, tumor, infarction, inflammation, infection, subdural collection
Methemoglobin (extracellular) in subacute hemorrhage
appears dark on t2
Low proton density, calcification, fibrous tissue
Paramagnetic substances: deoxyhemoglobin, methemoglobin (intracellular), iron, ferritin, hemosiderin, melanin
Protein-rich fluid
Flow void
Paramagnetic substance that causes T1 shortening = increased signal on T1-weighted images.
Gadolinium
Imaging modality of choice for most brain and spine disorders
MRI
MR for abdomen in children is used for:
staging of abdominal tumors
Imaging study for breast tissues
mammography
2 Basic forms of mammography
Screening
Diagnostic
age of women at average risk of breast ca
40
2 views in mammography
MLO and CC
commonly develop in women’s breasts because the breasts produce milk, which contains calcium
calcifications
Amass, or lump, found on a mammogram may be
Lymph nodes
Cyst
Fibroadenoma
can make mammogram evaluation difficult because the tissue can obscure small cancers
Dense breast tissue
use of gamma radiation to form images following the injection of various radiopharmaceuticals
Scintigraphy
emits gamma rays
Radionuclide
is an analogue of glucose and therefore accumulates in areas of high glucose metabolism
FDG
Area of high FDG concentration
hot spot
Isotope is attached to a biological compound to form a radiopharmaceutical
Most commonly used in ONCOLOGY
PET Scan
The main disadvantage of scintigraphy is
its non specificity
