1.5 Advanced Imaging

computed tomography

combines xray tech with computer processing

CT scans are ideal for

bone pathologies

CT scans use

ionizing radiation (more than radiograph)

CT scans are oriented by

planes of motion

coronal

image in frontal plane, read from anteiror to posterior

axial/transverse

cross sectional image, marked by R or L to indicate side of body

sagittal

midsection/side view, viewed from left to right

CT scan indications for use

high risk trauma, complex fractures, subtle fractures when radiographs show negative, surgical planning, evaluation of spine

CT scan advantages

available, highly detailed anatomy, bone accuracy, absence of superimposition, less time and cost

CT scan disadvantages

more expensive than radiograph, less detail for soft tissue, ionizing radiation

magnetic resonance imaging

use magnetic fields to generate images in 3D slices

MRI is the ideal imaging modality for

detecting subtle or early pathology (like stress fractures)

MRI indications for use

MSK soft tissue, ability to evaluate bone marrow, AVN, osteomyelitis/bone tumors, IVD pathology

MRI advantages

no ionizing radiation, excellent resolution of soft tissues, stress fractures

MRI disdvantages

cost, imaging time, patient comfort, less bone resolution, ferrous metal/pace makers, tatto/iron, pregnancy

bone scintigraphy/scan

nuclear imaging test using tracer, plays a role in evaluation of bone pathology

bone scans are

sensitive to bone pathology but not specific

bone scan indications for use

tumors, bone metastasis, metabolic bone disease, combination with other imaging

bone scan advantages

high sensitivity for changes in bone metabolism, lower cost than CT or MRI, availability

bone scan disadvantages

high radiation dose, residual radioactivity, prohibits contact with young children after test, low specificity, poor anatomic detail, time sensitive, pregnancy/breastfeeding

dual energy absorptiometroy (DEXA) scan

gold standard for bone density

T score

a comparison of bone density to the average peak bone density of a 30-year-old healthy adult

Z score

comparison of bone density score to norm of age

advantages to DEXA

minimal ionizing radiation, non-invasive, quick

disadvantages to DEXA

presence of ionizing radiation

diagnostic ultrasound

reflective imaging, no ionizing radiation, diagnostic and procedural, shows BF, looks at soft tissue (not bones)

indications for diagnostic ultrasound use

all soft tissues, nerves, feedback

advantages of diagnostic ultrasound

no ionizing radiation, real time imaging, dynamic assessment, low cost, portable, compare to contralateral (bc of low cost), rapid

disadvantages to diagnostic ultrasound

operator dependent, does not penetrate bone, better for superficial structures, may have problem during obesity

ionizing radiation can be sourced from

natural or artificial sources

ionizing radiations can be more harmful at

higher doses, cellular skin and protection (order based on evidence guidelines)

very high radiosensitivity of organs

embryonic tissue, lymphoid organs, bone marrow, reproductive organs, GI organs

very low radiosensitivity of organs

brain, spinal cord, muscles

ionizing radiation exposure can be environmental

exposure differs in various US regions