Intro to Labs and Panels & Diagnostic imaging DSA Flashcards
What data is included in a CBC?
WBC count Hgb Hct MCH MCHC MCV RDW RBC count Platelet count (Plt)
What information is included on a CBC with differential that is not included in the regular CBC?
Percentage and absolute differential counts (PMN, lymph, baso, eos, mono, atypical mono)
What info is included in a BMP?
BUN BUN:Cr ratio Calcium CO2 Chloride Creatinine eGFR Glucose Potassium Sodium
What additional info is included on the CMP that is not included on the regular BMP?
Albumin:globulin ratio (A:G ratio) Albumin (Alb) Alkaline phosphatase (AP) Aspartate aminotransferase (AST/SGOT) Alanine aminotransferase (ALT/SGPT) Bilirubin, total Globulin, total Protein, total
Describe US imaging
Uses high-frequency sound waves to generate an image, uses US coupling gel to aid in wave transmission to transducer
Pros and cons of ultrasound
Pros: no radiation, cheaper than other modalities, non-invasive
Cons: bowel gas and lung tissue hinder US image, technician skills vary, body habitus can affect results
Indications for US imaging
Trauma RUQ pain RLQ pain Pregnancy GU complaints Acute pelvic pain Cardiac concerns Evaluate blood flow
Procedures — thoracentesis, pericardiocentesis, etc.
What is a FAST exam?
Focused Assessment with Sonography in Trauma
Rapidly assesses for free fluid in the body! — primary views are subxiphoid, RUQ, LUQ, suprpubic
Describe conventional x-ray
Patient placed between film cassette and X-ray machine
X-rays pass through body and become attenuated, having photochemical reaction with fluorescent coated film, light particles create image
Radiographic density interpretation of air, fat, soft tissue, mineral, and metal on x-ray
Air = black
Fat = dark gray
Soft tissue = light gray
Mineral = off white
Metal = bright white
Types of contrast used with x-ray
GI contrast — Barium and gastrograffin
Typically given PO or PR; radioopaque to visualize GI tract
Ideal to wait 45 min s/p ingestion for best visualization
Adverse effects are minimal — N/V/diarrhea/constipation
Pros and cons of x-ray
Pros: cheap, easily accessible, fast, excellent screening tool, widely available
Cons: 2D pic, radiation exposure, poor detail of soft tissue
Uses indicated for x-ray
Cardiovascular Pulmonary Musculoskeletal Gastrointestinal Dental Mammogram Line and tube assessment
Modality that uses continually emitted x-rays and allows for real time visualization, but images are intensified with reduced radiation exposure and attenuation is different than conventional xray
Fluoroscopy
Uses for fluoroscopy
Esophagram Upper GI study Small bowel follow-through Barium enema Cardiac Vascular
Pros and cons of CT
Pros: widely available, quick, painless, somewhat reasonable price, 3D image in cross-section
Cons: potential contrast reaction, exposure to radiation, diagnosis limitations
Type of contrast utilized in CT, and why it is used
IV iodinated contrast — given IV or intra-arterial (opacifies vessel lumen)
Used because it increases attenuation compared to the anatomical structures that surround it (enhances visibility of internal structures)
Best uses: vessels, visualize tissue changes, urinary tract, fallopian tubes, etc.; neuro — veno/angiogram, abscess, malignancy
When would you NOT use contrast with CT?
If you’re suspicious of a bleed, renal stone, retroperitoneal hematoma — contrast might block your view of the bleed/stone
CT uses in Neuro, pulm, GI systems
Neuro: HA, trauma, r/o bleeds, CVA sxs, seizure
Pulm: acute SOB, CP w/ radiation to back, assess nodules/masses
GI: explore etiology of abdominal/pelvic pain, r/o renal stone, r/o GI path
[these are not all encompassing]
MRI basics
Use of magnetic field to generate image — manipulation of polarity of H+ atoms
Tissues generate different signals based on H+ composition giving GREATER DETAIL OF SOFT TISSUES
Define T1 vs. T2 images in MRI
T1 (longitudinal relaxation time) — time it takes for excited protons to return to equilibrium; contrast used
T2 (transverse relaxation time) — determines rate at which excited protons reach equilibrium or go out of phase with each other
Preferred contrast agent in MRI
Gadolinium
Administered via IV — tremendous paramagnetic properties
Used during T1 weighted imaging to improve visability of inflammation, tumors, blood vessels, organs, blood supply, etc.
Generally well tolerated with minimal SEs; reactions uncommon
When would you use T1 vs T2 imaging for MRI?
T1 — anatomy (anatomical details, fat containing structures, subacute hemorrhages). Water and collagenous tissue (ligaments, tendons, scars) have a lower signal transduction on T1 weighted image
T2 — pathology (edema, tumor, infarction, hemorrhage). Characteristic of T2 is high signal intensity of water. Pathology is often associated with edema/fluid, thus T2 is utilized in these cases
When should you use caution when selecting MRI?
Cardiovascular devices — pacemakers, stents, mechanical valves, IVC filters, etc
Unstable patients
Claustrophobic or agitated pts
Large body habitus
Cautionary considerations with Gadolinium contrast
Contrast induced nephropathy — can occur w/i 24-48 hrs of administration; characterized by increased serum Cr, decreased GFR with oliguria (<500mL UOP/day)
Nephrogenic systemic fibrosis — get pre-contrast GFR measurement
Advanced renal failure or dialysis pts (GFR <30mL)
Symptoms of nephrogenic systemic fibrosis induced by gadolinium
Thickening and harding of skin (spares the head); mimics scleroderma!
Also causes fibrosis of internal organs; stiffens extremities; flexion contractures
Pros vs. cons of MRI
Pros: safe, no radiation, precise with incredible detail of soft tissue
Cons: not widely available, costly, body habitus, pt must have extreme patience (takes 30-90 mins)
Define and note types of angiography
Injection of contrast media directly into artery or vein via needle or catheter
Invasive: percutanous (think cardiac cath lab - fluoroscopy)
Can also be non-invasive: CT or MRI
5 most important diagnostic imaging considerations when choosing a modality
- Safety
- Cost
- Availability
- Contrast vs. none
- Patient comorbidities
Deterministic (acute) and stochastic (chronic) effects of radiation exposure
Acute = burns, sterility, radiation sickness
Chronic = cancer, hereditary
Children, young adults, and women of reproductive age are at greatest risk with radiation exposure. What is an important consideration from this group?
Get B-hCG on reproductive age females!
The Law of Bergonie and Tribondeau states that the cells most sensitive to radiation have what 3 characteristics?
Rapidly dividing
Undifferentiated
Have long mitotic future
[high sensitivity = lymphoid organs, bone marrow, testes, ovaries, small intestines; fairly high = skin, cornea, lens, GI organs including esophagus, stomach, rectum; medium = growing cartilage, vasculature, growing bones]
What type of imaging has the highest radiation exposure potential?
Interventional fluoroscopy
[in order of increasing exposure: dental xray < CXR < mammography < CT < Nuclear medicine < interventional fluoroscopy]
What is PACS?
Picture archiving communication system
Allows you to look at and share previous imaging between providers
Contrast and radiation considerations in special populations
Previous allergy to contrast
Renal patients with creatinine > 1.5
Female pts — get B-HCG
Pregnant pts — don’t do contrast or radiation during days 16-45 bc critical for fetal dev’t
Children
Medications
What medication should you advise pts to withold prior to imaging with contrast d/t risk of lactic acidosis?
Metformin
Types of contrast reactions
- Hypersensitivity reactions — hives, anaphylaxis, urticaria, pruritis, angioedema; can be immediate or delayed. Pretreat w/ prednisone w/ diphenhydramine. Rapid tx is epi + saline +/- albuterol prn
- Chemotoxic reactions — self-limited; n/v, flushing
- Vasovagal reactions — increased vasovagal tone —> decreased SA and AV node conduction
You are seeing a pt and you suspect MS, what type of imaging would you do?
MRI
T1 — shows heterogeneity in white matter tracts
T2 — shows deep white matter demyelinating foci, with predominantly periventricular location — confirms MS
80 y/o male brought to ED after being found on floor; GCS is 10 and he is on warfarin. What type of imaging do you do?
CT w/o contrast
77 y/o male with acute change in alertness. What type of imaging?
CT w/o contrast
26 y/o female presents with neck pain s/p MVA. Denies weakness, numbness, tingling, UE pain, HA. What imaging do you do?
X-ray of neck - frontal and lateral
Get HCG first!
