Radiologic Imaging Flashcards
Physiologic imaging
SPECT, PET
X-Ray contrast agents
Iodine, barium
Use of iodine based contrast
administered through IV, visualize blood vessels, may cause anaphylactic reaction
Barium-based contrast
administered orally or as enema, visualize GI tract
Uses of X-rays
bony fractures/pathology, foreign objects, growth studies, infections, mammography
advantages of X-rays
low cost, high yield, low radiation exposure
x-ray limitations
low resolution, poor contrast for soft tissues
Uses of computed tomography
- head (trauma, stroke, cancer)
- lungs (nodules, emphysema, fibrosis)
- cardiac (embolisms, blockages)
- abdominal/pelvic (trauma, acute pain, cancer)
- extremities (complex fractures)
advantages of CT
fast, high resolution
limitations of CT
moderate to high radiation dose
MRI physics
magnetic field (Bo) created by a strong magnet, which is then perturbed by gradient coils. radiation of hydrogen atoms as they relax back to Bo are measured
MRI contrast agents
metal chelates (gadolinium): shorten relaxation times of surrounding protons, administered IV/orally, anaphylaxis is rare
Uses of MRI
neuroimaging, cardiovascular disease, musculoskeletal, abdominal imaging
advantages of MRI
no exposure to ionizing radiation, good soft tissue contrast
limitations to MRI
implants, pacemakers, metallic foreign bodies not compatible, claustrophobia & noise issues, all equipment in the imaging suite needs to be MR-safe
Ultrasound physics
sounds wave produced b/w 1-18 Hz. travels and reflects off tissues and transducer absorbs reflected waves. image generated based off strength and time it took for waves to return
Uses of ultrasound
obstetrics, cardiology, abdominal, head and neck, pelvis
advantages of ultrasound
instant image, no ionizing radiation, inexpensive & high yield
limitations of ultrasound
not able to penetrate bone, gas creates poor images, QUALITY OF IMAGES IS OPERATOR-DEPENDENT
Functional Magnetic Resonance Imaging (fMRI) physics
same as MRI but uses change in magnetization b/w oxygenated and deoxygenated hemoglobin, change in blood flow can be measured being coupled to neural activation - blood flow changes mapped onto normal MR image
uses of fMRI
functional brain mapping, detect effects of disease on brain function
advantages of fMRI
no ionizing radiation, studies can be repeated multiple times
limitations to fMRI
spatial/temporal resolution is limited, claustrophobia, no quantative
Physics of fluoroscopy (interventional radiography)
same as x-ray but detector system is an image intensifier, interventional radiologist controls the fluoroscopy
uses of fluoroscopy
angiography, placement of cardiac stents, guided biopsies, GI fluoroscopy
advantages of fluoroscopy
real-time imaging, inexpensive compared to MR or CT
limitations of fluoroscopy
medium radiation exposure, misuse could cause radiation burns
Single photon emission computed tomography (SPECT) physics
VERY SENSITIVE TOOL. molecules are labeled w/ gamma-emitting radionuclides, gamma ray is detected and then image can be overlaid a CT
uses of SPECT
bone scan, MI, parathyroid imaging, functional brain imaging, cancer imaging, infection imaging, GI function imaging
advantages of SPECT
ability to determine physiological function
limitations to SPECT
low resolution, medium to high radiation exposure
Positron Emission Tomography (PET) physics
similar to SPECT but uses positron-emitting radionuclides, positron annihilates when it encounters electron resulting in two 511 keV gamma rays, also overlaid CT image
uses of PET
oncology, neuroimaging, cardiology, regional cerebral blood flow, infections, bone scan
advantages of PET
physiological function, better resolution than SPECT, images ARE quantitative
limitations of PET
positron-emitting radioisotopes are short lived, take longer, more expensive
Anatomic Imaging
Diagnostic radiography (x-ray), Ultrasound, CT, MRI
