Mammogram
0.4
Extremity (per view)
0.5
Pelvis
0.7
Hip
0.8
Abdomen radiograph
1.2
Head CT
2
Ventilation/perfusion scan2
Lumbar spine radiographs3.5
Background radiation, 1 year4
Conventional coronary angiography5
Chest CT8
Abdomen CT
10
Pelvis CT
10
Coronary CT angiography15
Yearly maximum for radiation workers50
Fetal doses with shielding (unless fetus is in eld of view)
Chest X-ray< 0.01
Abdomen radiograph
2.4
Pelvis
1.7
Lumbar spine
3.4
Head CT
< 1
Chest CT
< 1
Abdomen CT
10
Pelvis CT
10
5
1 Introduction to Emergency Imaging
Fig. 1.1 CT window and level: skull fracture with epidural hematoma.
a,c Bone windows. Bone detail is superb, with clear de nition of a right temporal bone fracture. The subjacent epidural hematoma is invisible, as it is mapped to the same shade of gray as the adjacent brain.b,d Soft tissue windows. The epidural hematoma as well as the ventricles, scalp hematoma, gray mat-ter, and white matter are all clearly distinguishable. The skull fracture is visible but less well seen than on wider windows.
a
b
c
d
6Emergency Imaging
Emergency Premedication (in Decreasing Order of Eectiveness)
This premedication consists of methylpred-nisolone sodium succinate (Solu-Medrol) 40 mg or hydrocortisone sodium succinate (Solu-Cortef) 200 mg intravenously every 4 hours until contrast study required plus diphenhydramine 50 mg IV 1 hour prior to contrast injection.
Management of Idiosyncratic Reactions
Epinephrine is contraindicated in severe heart disease.
Mild Reaction
• Most require no specific treatment• Discontinue injection, maintain IV access
• Monitor, reassure patient
• Diphenhydramine 25–50 mg PO/IV
IV Contrast Delivery and
Maximum Flow Rates
Many CT examinations require rapid injec-tion of contrast material for optimal vessel opacification. Small peripheral IV catheters and some central venous catheters cannot be reliably used for rapid injection. Exam-ples of various catheters and their maxi-mum flow rates are listed here (Table 1.3).
Idiosyncratic/Anaphylactoid Reaction to IV Contrast Material
• 0.6% incidence of all reactions (nonionic)
• 0.01–0.02% incidence of severe reactions (nonionic)
• ~ 1/170,000 fatality attributed to contrast injection
Adverse Reaction Classication
(Table 1.4)
Risk Factors for Idiosyncratic Reaction and Indications for Premedication
• Prior moderate or severe reaction to intravenous contrast material• Asthma with active wheezing
• Asthma with history of event requiring intubation in past 90 days
• Any prior life-threatening allergic reaction
Mild or moderate reactions to other aller-gens (seafood, medications), mild urticarial reactions to contrast material, and mild to moderate asthma do not require premedi-cation with steroids.
Elective Premedication
Recommended premedication consists of prednisone, 50 mg by mouth at 13 hours, 7 hours, and 1 hour before contrast media in-jection, plus diphenhydramine (Benadryl), 50 mg intravenously, intramuscularly, or by mouth 1 hour before contrast medium.
If the patient is unable to take oral medication, 200 mg of hydrocortisone in-travenously may be substituted for oral prednisone.
Table 1.3 IV contrast delivery and maximum ow rates
Peripheral IV catheter
20-gaugeup to 5 mL/sec
22-gauge
up to 3 mL/sec
24-gauge
up to 1.5 mL/sec
Triple-lumen central catheter1 mL/sec
PICC line1 mL/sec
Power PICC
Rate indicated on hub
Introducer sheathup to 5 mL/sec
Broviac/Hickman1 mL/sec
Table 1.4 Adverse reaction classication
MildTransient, self-limited, and not life-threatening: nausea, cough, headache, dizziness, itching, chills, ushing, chills, sweating, rash, nasal stuness
ModerateSystemic and more severe mild reactions: pulse change, hypotension, hypertension, dyspnea/wheezing, urticaria, bronchospasm, laryngospasm
SeverePotentially life-threatening:
Unresponsiveness, convulsions, anaphylaxis, cardiopulmonary arrest, symptomatic arrhythmia
7
1 Introduction to Emergency Imaging
• Immediate family history of renal insuciency
• Diabetes, collagen vascular disease, sickle cell disease, multiple myeloma, or gout
• Hypertension requiring medication
• Nephrotoxic medications (metformin,
nonsteroidal anti-inflammatory drugs [NSAIDs])
• Further risk stratification is based on eGFR or serum creatinine.
• Category I: eGFR > 60 or serum