Imaging Flashcards
How is tissue density described on CT
Hounsfield Units
What is the CT density of bone?
350-3,000 HU
What is the CT density of Soft tissue, liver, blood?
40, 50-70 HU
What is the CT density of of Fat?
-50 to -100 HU
What is the CT density of lung?
-550 to -800 HU
What types of artefact are visible on CT?
Motion Metal Beam hardening Volume averaging Contrasting tissue
What is the absorbed dose of radiation and how is it measured
Amount of energy deposited per unit mass of material. Measured in Gray (Gy)
What is the effective dose of radiation and how is it measured
The effect of a radiation dose on an organism. Measured in sievert.
What is the accepted occupational dose of radiation
1 year <20 mSv
5 years <100 mSv
What is the radiation dose, and background radiation equivalent, of a limb x-ray
<0.01 mSv, <1.5 days
What is the radiation dose, and background radiation equivalent, of a Chest x-ray
0.02 mSv, 3 days
What is the radiation dose, and background radiation equivalent, of a CT brain
3 mSv, 15 months
What is the radiation dose, and background radiation equivalent, of a CT chest
8 mSv, 3.6 years
What is the radiation dose, and background radiation equivalent, of a CT abdomen or pelvis
10 mSv, 4.5 years
Types of image artefacts on ultrasound (6)
Tissue transmission speed artefact (distance from probe) Acoustic shadowing Acoustic enhancement Edge refraction / shadowing Reverberation artefact Mirroring artefact
What is the difference between T1 and T2 weighted imaging in MRI
T1: short magnetic pulse / reception. Water is low intensity.
T2: longer magnetic pulse / reception. Water high intensity.
POCUS sensitivity/specificity for paediatric appendicitis
sensitivity 60-80%
Specificity 90%
Features of appendicitis on US
Primary: diameter > 6 mm, blind ending, non-peristaltic, non-compressible
Secondary: Appendicolith, caecal attachment, echogenic surrounds, free fluid, hyperaemia
Perforation: dilated bowel loops, echogenic fat, complex fluid collection
Causes of haematuria and differentiating factors
Post strep GN - preceeding sore throat / skin infection
HSP / SLE - rash and arthritis
HUS - diarrhoea +/- petechiae
Infective, schistosomiasis / TB - travel
Wilms tumour - abdominal pass
UTI - dysuria, fever
Pretest probability of UTI in febrile child
Girls, boys - circ and uncirc
Girls: 7.5% in 0-3 months, 5-8% <12 months, then < 2%
Boys: uncircumcised 0-3 months 20%, circumcised boys 0-3 months 2.4%. 3-6 months 3.3%, 6-12 months 1.7%, > 12 months < 1%
What is haemolytic uraemic syndrome / key features for diagnosis
Microangiopathic haemolytic anaemia (shistocytes, reticulocytosis, raised LDH, raised bilirubin)
Thrombocytopaenia
Acute kidney injury (haematuria, proteinuria)
Associated with diarrhoea (e. coli producing shiga toxin) or non-diarrhoeal (other infections, complement abnormality, immunosuppression, metabolic error).
Diagnosis of HSP & other clinical features
Palpable purpura (symmetrical, dependent)
Normal platelets and coagulation
One / more of
- abdominal pain (oedema and haemorrhage)
- arthralgia / arthritis
- renal involvement (proteinuria, haematuria)
- histopathology: leucoclastic vasculitis with IgA deposits.
Subcutaneous oedema
Dyspnoea / diffuse alveolar haemorrhage
ETT depth of insertion & CXR level
age / 2 + 12
Interclavicular line with neutral head
Extension of neck = tube in
Adrenaline dosing
- arrest
- anaphylaxis
- infusion
Arrest: 10 mcg/kg, 0.1 mls/kg 1:10,000 IV
Anaphylaxis: 10 mcg/kg, 0.01 mls/kg 1:1,000 IM
Infusion, post arrest: 0.05 - 3 mcg/kg/min infusion
1 mg (1ml of 1:1000) in 1L saline, at 5 mls/kg/hr = 0.1 mcg/kg/min
