Imaging Flashcards
1
Q
What is an x-ray?
Relies on what, and damage it can cause?
Good for what?
A
- ionizing radiation
- MC imaging: film mainly replaced by digital sensors
- relies on differential absorption: air, fat, water, bone densities
- ionizing radiation can damage tissue: developmental issues, cancer
- good for lungs, kidney/gall stones, bonesL anywhere there are air/fluid contrasts, or bone/soft tissue contrasts
- not as good for soft tissues and brain, pathology can be hidden by normal structures
2
Q
Best imaging options for bone lesions?
A
- x-rays: most valuable initial imaging:
look at nature of bone matrix
look at interface of lesion and bone - most lesions at metaphysis near growth centers
- benign: well defined, no cortical destruction or periosteal reaction
- malignant: ill-defined, destructive, infiltrative, lytic or blastic
- CT: best for eval subtle bone changes: good for areas hard to see on plain films
- MRI: better for soft tissue and infiltrative marrow lesions
- Bone scans: show metabolic activity, looking for mets:
PET/CT beoming imaging of choice
3
Q
DDx bone lesions?
A
- in general: trauma, benign lesions infection, inflammatory condition - aggressive bone lesions: mets primary malignant bone tumor infection
4
Q
What is a fluoroscopy? Pros and Cons to this?
A
- cont. x-rays used to obtain real time moving images of internal structures (GI studies)
- can use to help guide fine needle bx
- prolonged procedures can lead to skin burns
- small cancer risk
5
Q
What are upper GI studies?
A
- barium swallow + fluoroscopy
- contrast allows for exam of esophagus, stomach, and duodenum
- eval of ulcers, GERD, vomiting, blood loss, hiatal hernia
6
Q
What is a CT scan?
A
- x-rays taken in several planes are computer processed to show images in mult. slices: AP, lateral, sagittal, x-section, and even 3D
- part of PET and SPECT scans
- subject to artifacts and distortion
- best images with hgihest doses of radiation
7
Q
Advantages of CT scans?
A
- greater detail than regular x-rays
- can diff structures of close physical density
- eliminates superimposition of organs
- show calcified and hemorrhagic lesions
- can be shown in multiple planes or even as 3D image
- good in neoplastic disease:
- in abdomen in staging
- good for eval of masses in chest
- virtual colonoscopy - screening for colorectal tumors
- most intracranial neoplasms are visible on CT
8
Q
Downsides of CT scans?
A
- risk of cancer (may increase as CTs are used more)
- radiation dose of abdominal CT = 200 CXRs
- 0.4% of cancers in US due to CT
- worse in kids and immunocompromised pts
when contrast agents used:
-allergic rxns: 1-3% non-ionic and 7-12% ionic contrast agent
-anaphylaxis: old ionic agents 1%, now 2-30/mill
contrast induced nephropathy: 2-7%
- expensive
- observer variation
9
Q
What is a pancoast’s tumor?
A
- extension of tumor at apex of lung involving C8, T1, T2, nerves and possible destruction of ribs
- shoulder pain radiating in ulnar distribution
10
Q
How is a virtual colonoscopy done? Downside?
A
- usually done with CT, but can be done with MRI also
- reqrs bowel prep like colonoscopy
- no need for sedation, quick recovery: injection of butylscopolamine (antispasmodic)
- not as sensitive as colonoscopy
- can’t do bxs
11
Q
When are 3D reconstructions used?
A
- when planning local resection
- excellent for eval of bony architecture
- helpful in eval bony integrity, alignment and stability
- preop planning for sites of fixation and reconstruction - 3D CT
12
Q
What is a mammography?
A
- uses low energy x-rays to generate images
- normal breast has masses, not homogenous
- look for masses, asymmetries and micro-calcification
13
Q
What do you do with an abnormal mammogram?
A
- needs breast exam by skilled clinician
- further mammography to confirm if finding is real
- additional imaging tests - US - for better definiton
- BIRAD classification helps with further testing/f/u
- can use MRI with gadolinium - implants, very dense tissue
- needle or surgical bx may be recommended
- tissue dx is key for planning tx
- most mammogram abnormalities are not cancer, most are due to benign changes
14
Q
What are nuclear scans?
A
- radio-isotope is injected IV: usually technitium 99m, occasionally gadolinium
- 3 hrs later pt is scanned with gama camera
- provides 2d image, PET and SPECT provide 3D
these can be combined with CT and MRI - fxnl test: measures bone metabolism or remodeling
- half of material goes to bones - osteoblasts: shows fractures, infections and most tumors, lytic tumors may not trigger a healing response - not seen
- radioactive material is eliminated through the kidneys
15
Q
Use of bone scans?
A
- show increased metabolic activity or increased blood flow
- assess activity of known lesions, find unknown lesions
- sensitive test that can overestimate lesions
- marrow replacing tumors (MM) are cold until cortical disruption occurs
- bright spots are either arthritis or mets
