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
16
Q
How do PET scans work?
A
- Positive emission tomography
- usual tracer is fludeoxyglucose (FDG)
- CT xray usually performed in same sitting
- can be combined with CT, MRI to create 3D images
- esp useful in lymphomas and lung cancers
- FDG collects in highly metabolic tissue: detects active, rapidly growing tumors, used to detect mets
- dramatically displayed in scans
- higher grade malignancies detected more than benign processes: low grade cartilage lesions underestimated, hard to diff benign and low grade malignant lesions
- PET compared to 99 Tc (bone scan): 91 vs 75% sensitivity for cancer, 96 vs 95% for specificity
- expanding role in assessing response to cancer tx
- can affect care in about 1/3 of pts with cancer
17
Q
What is a SPECT scan?
A
- single photon emission computer assisted tomography: high resolution + accurate localization
- gamma/nuclear camera (bone scan) + CT scanner:
thallium, technetium, iodine, gallium isotopes used, emit gamma radiation that is measured directly - good for small spinal lesions: osteoid osteoma and osteoblastoma
- more expensive than bone scans (insurance companies may require authorization)
18
Q
What are MRIs?
A
- magnetic resonance imaging
- powerful magnets excite H protons to emit measurable electromagnetic radiation
- extremely sensitive imaging:
shows soft tissue as well as bone, distinguishes grey from white matter in the brain - oscillating coils switched on/off rapidly - characteristic noise
- many ways of presenting info: T1 and T2 imaging (diff pulse sequences), 3D reconstructions
- advanced MRI techniques: angiography, fxnl MRI, diffusion MRI, CSF dynamics
19
Q
Downsides to MRIs?
A
- expensive, slow
- claustrophobia
- pacemakers, stents
- small metal fragments
- metal artifact
- need calm pt
- may be genotoxic
20
Q
What MRI pulse sequence is better at detecting tumors and infarcts of the brain?
A
- T2
21
Q
MRI vs CT of the brain?
A
- skull gets in the way of xray imaging
- bone scatters x-rays much more than soft tissue, MRI radio waves pass unimpeded through bone (MRI is superior)
22
Q
What can you see on an MRI of the spine?
A
- radiation free
- superior for soft tissue imaging
- can see subtle differences
- L3-4 discitis - loss of disc space
- reactive edema in vertebrae
- gadolinium assists in delineating surrounding vascularity
23
Q
What is an US and how does it work?
A
- high frequency sound waves: produced by piezoelectric transducer
- reflect and echo off tissues: received in transducer
- processed in ultrasonic scanner: turned into digital image
- usually seen as 2D image, also movement over time, blood flow, location of blood, tissue stiffness, 3D
24
Q
Pros and cons of an US? Imaging modality of choice for?
A
- cheap, quick, easy, safe, comfortable, shows solids and fluids, muscle, tendon, bone surface
- hampered by bone, air, fat, very operator dependent
- imaging modality of choice for thyroid tumors/lesions
- can use to supplement mammography
25
Q
How do you make the dx of a tumor?
A
- tissue is the issue
- may need open bx
- may be able to do needle bx: CT, fluoroscopic, or US guidance
26
Q
FNB of lung lesions?
A
- use for peripheral lesions, dx yield: 90-97%
- outpt procedure: 22 gauge needle
- image guidance: fluoroscopy, CT, US
- lung bx: may lead to pneumothorax (10-30%), hemoptysis (30%)
27
Q
What should you look for on spine imaging for mets?
A
- breast, prostate, lung and kidney go to bones
- early spine mets usually seen at base of pedicle -
will see unilateral destruction of pedicle - winking owl sign - early on xrays are of limited use
28
Q
Of those who presented with isolated back pain - and had abnormal xrays of spine - what primary cancers were the main culprits?
A
spine:
- met from breasts (94%)
- lungs (74%)
- lymphoma (40%)
29
Q
Most common spot on spine for tumor to cause neuro compromise?
A
- 70% lesion in vertebral body
- 10% lesion in posterior elements
- disc isn’t usually involved (unlike infections that thrive in avascular areas)
30
Q
What imaging modalities can you use to assess response to tx?
A
- bone scan, CT, PET
31
Q
What imaging modality is best predictor of survival after cancer Rx?
A
- PET scans
- if PET scan is negative after therapy, the tumor is likely to be dead at time of surgery
32
Q
Causes of pathologic fractures?
A
- occur through area of weakened bone: osteoporosis benign cystic tumor malignant tumor - when tx fracture always assess the bone!
33
Q
Pros and cons of x-rays?
A
- pros: simple, inexpensive, readily available, easily interpreted
- ## cons: radiation, poor tissue contrast, technician dependent, in 2D
34
Q
Pros and cons of CT scan?
A
- pros: rapid, 3D capability, axial imaging, good bony detail
- cons: highest radiation, motion and metal artifact, limited ST contrast
35
Q
Pros and cons of bone scans?
A
- pros: images metabolic activity, very sensitive in bones, low cost
- cons: non-specific, poor detail, anatomic changes not visualized
36
Q
Pros and cons of MRI?
A
pros: superior tissue resolution
cons: expensive, motion, and metal artifact, can’t use in some pts (metal fbs)
37
Q
Pros and cons of PET/CT or PET/MRI?
A
- pros: combines fxn and anatomy, best imaging for most cancers
- cons: expensive (pre-authorization from insurance)
38
Q
Pros and cons of US?
A
- pros: very safe, inexpensive, and quick
- cons: small field of view, technician and radiologist dependent, artifacts
