Final Exam Material Flashcards
Inventor of CT Scan 1972
Godfried Hounsfield
Conventional CT (default)
Tube rotates 360 degrees then table moves
Helical CT
Moves in a continuous figure 8 while patient slides through
aka’s for helical CT
Spherical or multidetector
Hounsfield Units (HU)
Calcium +1000
Water 0
Air -1000
Maximizing bone vs soft tissue vs lung parenchyma/ Windowing
2000 HU of density captured per image: human eye see only 400 HU at a time
Best modality for fine bone detail
CT Scan
Best modality to see calcium
CT Scan
Modality to find OPLL
CT Scan
Modality to find subtle fractures
CT Scan
Thin section CT
aka high resolution CT
Thin section/ high resolution CT
Gold standard for chest imaging
Bone Window
Allows you to ddx cortex from medulla
Soft Tissue Window
Cortex and Medulla blend together. Muscular structures can by seen
Helical CT advantages
Image large areas in detail in short period of time. Higher dose and higher cost. Good for screening trauma in unconscious patients
CT advantages
Great for bone detail, fracture and tumor assessment, calcium lesions, GI/GU conditions, acute brain bleeds
3D CT
Used for reconstructive surgery and visceral conditions
Jefferson Fx
Often not visible on plain film, occurs via axial load to vertex of head, rust sign. CT is definitive
Dens Fx
Minimal displacement on plain film. Dens NOT well visualized on MR. CT is definitive
Hangman’s Fx
Very hard to see on plain film, via forced hyperextension injury, CT definitive
UID/BID
Very hard to see on plain film (bow tie sign/inverted bun sign), via hitting head and shoulder simultaneously or head turned during flex/ext injury, CT definitive
OPLL
Confirmed with CT but MR better to see degree of neural compromise. Manual adjusting contraindicated
Tumors
CT to view margins of lesion and tumors that have calcium
Lung Lesions
CT is gold standard for almost all lung lesions
CT and GI/GU
CT excellent resolution. Ultrasound may be a better alternative
Acute brain bleed
CT great to assess stroke, epidural or subdural bleeds
Metastatic disease (nuclear medicine)
Can image entire body with one exam (same exposure as C/T/L/P x-ray series); sensitive to early change
Fatigue fracture (nuclear medicine)
Sensitive but doesn’t explain problem if scan is negative; MR is better choice
Paget’s (nuclear medicine)
Great to identify which bones are involved
ddx bone island vs early mets (nuclear medicine)
For a px over 40 with pain and no series of previous films available. If scan is cold it’s a bone island
Bone scan/scintigraphy (nuclear medicine)
Fracture will stay hot for 12-18 months. Tc-99 most common.
Nuclear medicine
Aka bone scan/scintigraphy.
Sensitive but not specific.
Hot benign processes: Paget’s and FD.
Cold for MM
Nuclear medicine technique
A radionucleide is tagged to a metabolite and areas of increased uptake visualized.
Single Photon Emission Computed Tomography (SPECT)
Slices through a bone scan. Good to ddx active from inactive pars defect
Active pars defect (SPECT vs MRI)
Non union of stress fracture in pars due to repetitive hyperextension. Eventually fibrous bridge might form (not visible on X-ray)
Active = fractured pars defect
Boston hard brace holds body in slight flexion so healing can occur
Px with DISH getting numb. You suspect OPLL
Confirm OPLL with CT
Px with OPLL and neurological signs
Get MRI to see degree of cord impingement
CT abdomen imaging
Use oral contrast
CT imaging with kidneys involved
Use IV contrast
Reformatting
Volume averaging used to create slices in any plane
HU; X-ray vs CT
X-ray HU = heat unit
CT HU = Houndsfeild
Positron Emission Tomography (PET)
Tag radionucleotide with sugar to mimic sugar uptake. Can be used with CT or MRI. Good for tumor evaluation and screening for recurrence
PET advantage
Assessing many tissues at once
PET disadvantage
Expensive and technically challenging
